Composting in the Carolinas - Proceedings of the 1996

Transcription

Corr
co
as
COMPOSTING IN THE CAROLINAS
Proceedings of the 1996 Conference
COMPOSTING SOLID WASTES, YARD WASTES AND/OR BIOSOLIDS
October 23-25, 1996
Myrtle Beach, South Carolina
Edited by:
Dr. Richard K. White
Sponsored by:
North Carolina State University
Clemson University
NC DEHNR, Division of Waste Management
SC DHEC, Division of Solid Waste Management
NC DEHNR, Division of Pollution Prevention and Environmental Assistance
SC Ofice of Solid Waste Reduction and Recycling
NC Recycling Association
SC Recycling Association
NC Composting and Organics Recycling Council
Published by:
CLEMSON UNIVERSITY
1 13 McAdams Hall
Clemson, South Carolina 29634-0357
Phone: (864) 656-4073
COMPOSTING IN THE CAROLINAS
ORGANIZING COMMITTEE
Ron Alexander
E & A Environmental Conmltants, Inc.
Craig Barry
Dee Browder
Wheelabrator Clean Water Systems
Bobbie Campbell
Mecklenbwg County Recycling
Sarah Carson
J. Ray Cox
NC DEHNR - Water Quality
K. C. Das
University of Georgia
Bob Forbes
CHZM Hill
Frank Franciosi
R T Soil Science
Beth Graves
NC DEHNR - Division of Pollution
Prevention and Environmental
Assistance
Ron Grote
NC State University
Sidney Harper
US EPA, Region IL'
Ellen Huffman
Charlotte-MeckletlbrrrgUlility
Department
Ted Lyon
NC DEHNR - Division of Waste
Management
John Oxner
Richiand County Extension Agent
Diane Marlow
SC Clean and Beaut@
Tony Martin
Marlin Bio
Trille Mendenhall
Charlotte-Mecklenburg Utility
Department
Bob Rubin
Cindy Salter
Organics Matter
John Schnabel
SC Department of Health and
Environmental Control
Jim Shelton
Joan Williams
SC Department of Health and
Environmental Control
Dick White
Clemson University
Fran Wolak
Clemson University
PREFACE
The conference on “COMPOSTING IN THE CAROLINAS - Organics Another Way” recognizes
the importance of comprehensive programs for managing organic wastes. This topic affects
environmental agencies and groups on the federal, state and local levels.
A comprehensive, organic waste management program includes waste reduction, recycling, and
reuse, which include composting. The purpose of this conference is to provide a forum to discuss
the issues associated with the composting of municipal solid wastes, yard wastes, biosolids or
other organic wastes. This program is intended to acquaint participants with the basic principles
of composting, developing public education and information programs, examining regulatory and
environmental issues, planning and designingof composting facilities, economic issues associated
with composting, odor control strategies, and marketing of composted materials.
These waste management and recovery issues do not start or stop at the state or county
boundaries. Each of the issues addressed will help waste management personnel to better select,
design and operate facilities handlingthe compostable fraction of their waste streams.
The sponsoring Agencies and members of the Planning Committee appreciate the support and
encouragement of thoseattending the Conference.
Dr. Richard K. White, Clemson University
Chairman, Organizing Committee
TABLE OF CONTENTS
COMPOSTING ISSUES SESSION
The Economic Angle of the Compost Business . . . . . . . . . . . .
Rodney W. Tyler
Composting Process Models and Model Application
Philip B. Leege
.....................................
.............................
Innovation and Update in Compost Marketing: A Year in Review
Rot1 Ale.rander
1
9
17
ODOR CONTROL SESSION
Biofilter Economics and Performance
R. .4llen Bo,vette
19
Enhanced Biofilter Design for Consistent Odor and VOC Treatment
Larty Finn and Robert Spencer
.......................................
Air Emissions Testing and Odor Modelling . . . . . . . . .
Titn Muirhead, Todd Williams and Graham Gillqv
28
33
NORTH CAROLINA COMPOSTING PROJECTS
Changes in the North Carolina Compost Rules
Ted L,von
........................................................
34
Case Study - The NC Zoo MSW Pilot Composting Project
Brooks Mullane and Bob Rubin
35
The Reduction of Fish Processing Wastes to Provide a Marketable Product Through Composting
Lori Cunniff and Joseph A!. Edwards
39
Solid Waste Pilot Compostlng Project: Results and Lessons Learned. The Marine Corps Base,
CampLejeuneExperience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Julie A. Shantbaugh and Pent1,v Mascaro
44
COMPOSTING - CASE STUDIES
Development of a Leaf Distribution Program for On-Farm Composting
Archer Christian andGregoty Evanylo
53
The Big and Small of Riosolids Cornposting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Todd 1ltillianls,R. Allen Boyette, Eliot Epsteitl, Scott Plett and Curtis Poe
58
TABLE OF CONTENTS (CONTINUED)
Agitated Bin Composting, Start-up and Operation
Patrick D. Byers
.....................................................
71
COMPOST ECONOMICS
Cost Savings Through Regional Biosolids Composting in the Triangle Region
Parrick Davis and JudvKincaid
80
Municlpal Solid Waste Composting: Does It Make Economic Sense'?
Mitch Renkow andA. Robert Rubin
87
....................................
Developing and Facilitating Green fndustty Markets for Composted Organic Materials
Anita R. Bahe
95
...........
COMPOST END USE RESEARCH
Evaluation of Compost-Based Potting M I X For Commercial Nurseries. . . . . . . . . . . . . . . . . . . . . . . . . .
Frank Franciosi, Ted E. Bilderback and William G. Lord
Compost Effect on Cotton Growth and Yield
Aziz Shiralipour and Eliot Epsrein
......
102
108
...............
..................................
1 16
Papermill Sludge Compostmg and Compost Utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gregory K. Evanylo, W. Lee Daniels and Ren ShengLi
124
Composted Biosolids for Agronomic and Horticultural Crop Production
James E. Shelton, J.R. Joshi, and P.D. Tate
VARIOUS COMPOSTING TOPICS
Increasing Invessel Eficiency at a Commercial Biosolids Composting Facility: Practical
Aspects of Moisture Loss Estimation and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Keshav Das and Harold M. Keener
144
Compost Stability Determlnation . . . . . . . . . . . . .
Manning M'. McAdanls and Richard K. White
The Effect of Large Scale Vermicomposting on a Corporate Hog Farm
Chris Christenberry,.Lfichael Edwards and Tom Christenberry
Trace Metal Uptake/Availability from Three Municipal Composts
K.R. Baldwin and J.E. Shelton
136
...................................
. . . . . . . . . . . . .
150
155
TABLE OF CONTENTS (CONTINUED)
page@)
COMPOST MARKETING & UTILIZATION
Usmg Compost Successfully . . . . .
Ron Alexander andRod Tyler
Author’sIndex
..................................................
..
179
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.
.
180
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . ..
.
183
Addresses for Pnmary Authors
TitleIndex
167
DISCLAIMER
Papers appearing in this volume were submitted by the authors in a “camera-ready’’ form.
They were reviewed only for editorial consistency. The authors are responsible for the technical
accuracy of the data and interpretation of data. Opinions and interpretations employed in these
papers do not imply the endorsement or support of the editors or publishing agency. Use of
brand, firm or trade names in this volume is for identification purposes only and does not
constitute endorsement by the editors, publisher or sponsoring agencies.
THE ECONOMIC ANGLE OF THE COMPOST BUSINESS
Rodney W. Tyler
BFI
Lorain County Resource Recovery Complex
Oberlin, Ohio
Factories produce products for sale. All factories deal with the same basics ofpurchasing raw materials, combining
them to produce a product and selling products to customers to derive profits. As ntlow of raw materials increases, so
does production and If markets are available, sales will follow. Compost factories have a unique edge over this standard
factory system because they usually gerpaid to take raw materials.
Payment for inflows (unprocessed orgamc matenals) and outflows (compost products) results in a dual revenue business
for the compost factory Since dual revenue generation is not the standard for most businesses, it is covered in detail
here Understandrig both sides of this unique economic equation allows managers to conduct business more efficiently
COMPOST BUSINESS RATIOS
The compost business is unique because there are two sets of customers for the company to satisfy: 1). The intlow
custoriier, requiring services for disposal or reuse of solid wastes. These are the old, established businesses familiar with
terminology about how to handle "waste". Since over half of the US currently have programs diverting materials like
yard tnmmings or biosolids to reuse programs, traditional services like landfilling must be expanded to include
beneficial uses for these valuable "organic resources". Composting is the technology normally chosen to accomplish this
task and automatically develops another customer base (2) around the distribution of the final product. Sales of finished
product requires a more technically minded customer base. This relationship, between inflowing and outflowing
matenals, is in the table below, showing both sides of the "economic compost equation", otherwise referred to as the "Tchart". The left side focuses on waste management services, the right side on sales of organic products.
Table 1 1.1 : Economic compost equation ("T- chart") for the compost business
Inflowing materials = 100,000 yards
(tip fees collected)
Outflowing materials = 16,500 yards
(products sold)
Revenues
$6.00/yd
$6.00/yd
costs
$5 .OO/yd
$O/yd
Net Return
$1 .OO/yd
$6.00/yd
Inflow Revenues + Outflow Revenues = Total revenues
(SlO0,OOO + $99,000) = $199,000
It is assumed in this example that costs of operations are about $5.00 per cubic yard. As with most figures in this paper,
these are examples only and actual figures should be determined on a site by site basis.
-"WeAmericans love numbers Vumbers provide facts Facts give us answers Ifwe can quantifL a problem, we can solve i t . Ofcourse. i t helps
ifthe numbers are accurate. but i i I S more important that they exist If they exist. they are assumed io be accurate andpolicy can be developed" --Cha: Miller 1995
1
The T-chart is the most simplistic way to get to the bottom line which analyzes both inflow and outflow economics at a
compost factory. Obviously a lot more work has to be done before arriving at the T-chart shown. There are several
ways to calculate each side of the T. The easiest method is to calculate total revenues as if each side is a separate
business. The compost factory owners emphasis will usually be placed on either the inflow (tip fee) side or on the
outflow (product sales) side. Only the most successful coniposl factories h m e excelled at maximizing both sides of the
T a t die same h e . Understanding both sides of the T-chart means to understand the composting industry as a whole.
In general business and in other factones, the "bottom line" is all that really matters in the long run In Table 1 1.1, the
"bottom line" is "I + 0 = 1otal Revenues" where I = inflow revenues ($lOO,OOO), 0 = outflow revenues ($99,000) and T
= total revenues ($ 199,000) Note the inflated inflow revenues from higher tip fees even though the product is given
away, the bottom line is nearly the same
Table 1 1.2: Revenues generated from increased tip fees and giving awav product.
Inflows ( 100,000yds)
Outflows (16,500 yds)
Costs = $5.00/yd
Costs = 0
Revenues = $I.OO/yd
Revenues = 0 (product given
away)
Net + $2.00/yd
Net = 0
Net return = $200,000
(note again that all costs are covered by the tip fee side)
The tipping fees increased only $1 OO/yd (or about $4 OO/ton) to achieve the same revenues as selling all the product in
the previous example at $6 OO/vd Since composting shnnks matenals, it will normally be easier to adjust total revenues
quickly by increasing tip fees associated with the inflow matenals
Many compost marketers do not realize the subtle relationship between product sales, tip fees, total company
profitability, or what percentage of their profit is coming from the nght or left side of the T As the compost industry
matures and becomes more competitive, it will become imperative for managers to understand what the % of total
revenue is generated from each side ofthe T Another example is shown below, indicating a free tip fee for inflow
matenals and all revenues to be generated by product sales (opposite to table 1 I 2 )
Table 1 1.3: Revenues generated from increased sales of finished product and free tip fees.
Inflow (1 00,000 yds)
Outflow ( 16,500yds)
Costs = $5.00/vd
costs = 0
Revenues = 0 (free tip fees)
Revenues = $36.50/yd
Net
= ($500,000)
Net = $602,250
Net Return ( I + 0 = Total) = $102,250
(ndie all costs are covered by the sales side)
2
Economic ratios are often used to study relationships of one item compared to another The leverage ratio is a measure
of liquidity in finance Most lenders will not approve home loans unless a standard ratio of spending to income is
achievable Ratios of revenues associated with the nght or left hand side of the T-chart are important By usmg T-chart
ratios (or T-ratios), the amount of dependence that a facility has on either side I I ~relation to total revenues IS easy to
calculate Two examples below illustrate different T-ratios
Table 1 1.5: Examples of T-ratio calculation for tip fee or market dependent strategies.
Revenues from:
Idlow
$100,000
outflow
$ I00,000
Total Revenue = $200,000
"
I/ T" ratio = $100,000/$200,000= 50%
" O n ratio = $100,000/$200,000 = 50%
In the,above example, the revenues are split equally between mtlow and outflow. This is a balanced approach but often
times not feasible during competitive bid situations. For instance, what would happen to the ratios if the inflow revenue
had to drop to a low number just to obtain a competitive bid? At first, this may sound unrealistic, but many companies
are beginning to rely more on the sale of the finished product to generate profits. These profits can only come from the
dollar markets at this time due to the underdevelopment and lack of economics associated with the volume markets. A
shift in emphasis from the balanced approach shown above to a market dependent approach is shown in table 1 1.6.
Table 1 1.6: T-ratio calculations for "product sales dependent" strategies.
Revenues from:
Inflows
$10,000
Total Revenues = $175,000
In = 6%
Outflows
$165,000
o n =94%
Total revenue has been significantly reduced. Note that if the inflow numbers are negative, the T-ratio system will not
work. There are very few examples of compost factories in the country that are successful while having a negative left
side. Most already had an established business and use compost as a replacement for a more expensive ingredient. It is
not wise to over compensate one side or the other for lack of profitability. The above example is a poor business deal
unless the market sales are guaranteed and even then, profitability is low and the future dim if competition in the market
increases.
Consider another example in which a market is developed over time and average price of product (right side) raises from
$6.00 to $1 0.00 per yard while the inflow side stays constant. Perhaps h s example is realistic in a contract situation
over five years.
3
rable 1 1 7 Right side of the T revenues over a five year increase
Inflows = 100,000yards
Outflows = 16,500 yards
Costs = $5.00bard
Revenues = $6iyard
costs = 0
Revenues = %6.00@rd
Net return = $100,000
Net = $99,000
Outflow = 16,500 yards
costs = 0
Revenues = $1 O.OO/yard
Net = $165,000
Year One O/T ratio = 50%
Year Five O R ratio = 62%
Using the same volumes as previous examples, year five I/T = 38% ($100,000/$265,000) and O/T = 62%
(Sl65,000/$26S,000). Note the two sides added together (38% + 62%) equal 100% and that the marketing function has
now assumed dominance in economic importance over the total operation. As such, this economic importance should
automatically predispose the entire operation to maximum quality control of the product, so that market revenues are
preserved. When the contract for this project is reviewed, the company with strong markets will be in a position of
strength
Many'economists are quick to point out that it is impossible to pay for capitalization, start up and operation costs based
upon the sales of the product alone. Most successful companies have OR ratios of 25% or less. A recent study in
Switzerland stated that the average compost marketing program produced income of only 10% of site operating costs
alone (hinton, 1993). This means that an OR ratio of less than 10% exists. It was later revealed that many local
markets had to be subsidized and the majority of the income came from the tip fee (or inflow) side.
Since many of these facilities were partially funded by local cities, sales support from the marketing side would help
these public-pnvate partnerships "pay otr' sooner, or reduce needs to raise tipping fees in the future (Brinton, 1993).
Note that although the above example is only a 12% increase on the O/T ratio, the total revenue increased 33%!
Guidelines for these T-ratios are not age old standards ... rather they depend on which side of the T the principles of the
compost factory owner lie. My own experiences are that 7540% of the income should come from the inflow side until
the industry reaches an age of maturity and diversification. At that point, competitiveness will increase and people will
have to rely more heavily on profits from the marketing side.
Currently, companies relying on product sales for all of their profits are doing so not due to competition, but due to
inferior management, poor design of inflow systems, or their excellent ability to market end product. An O n ratio that
is indicative of a healthy compost factory is .25 or less. T h s means total product sales account for less than 25% of total
revenues (where total revenues = inflow + outflow revenues). A company may be able to survive a year or two if they
do not cover costs associated with overhead by paying the interest only on loans. As the company matures and long term
debt is paid off, they can rely more on the sale of the products without risking daily survival.
To every rule of thumb there are, of course,exceptions. Although they are rare, companies that depend 100% on
outflow revenues for making an operation profitable do exist. More times than not, these companies have used compost
to replace a higher valued product in an already successful business.
For example, Malcolm Beck, in Austin Texas, has operated a compost facility without a tipping fee successfully for
many years. His original facility has diversified (as you would expect by any mature business) and the compost product
is now sold through 12 ditlerent mixes to retail and wholesale clients ranging from $14.50 to $60.00 per cubic yard
(Goldstein, 1993) Even in this highly successful marketing example, only about 40% of sales are from small
volumeretail buyers (Goldstein. 1993), indicating the need to depend upon the larger wholesale market to deplete
inventories.
4
PRODUCTION
There are entire textbooks which identlfy production necessary in operating a compost facility This section only focuses
on a small portion which is often overlooked management and measurement of efficiency in production systems
Compost factories can be broken down into stages of production. Much like any product manufacturing process, the raw
materials must first be collected, graded, processed, composted, checked for quality, manufactured, sold, delivered and
used successfully. Each stage of production can be individually measured and analyzed to assure the site manager is
using the best available technology and maximizing efficiencies. Each "stage" manager is constantly challenged to
improve the system.
An example of processing yard tnmrmngs is shown n table 1 1 1 1 and is a good indication of how many vanous options
eust and associated costs Keep in mind that the only thing that should matter to a businessman is the quality of the end
product, processing (and safety) cost per cubic yard of producing compost through the system
Table 1 1 . 1 1 : Options for processing yard trimmings using various stage production techniques
Stage 1
Tipping floor
sorting)
Tipping floor
(sorting)
Tipping floor
(sorting)
Stage 2
Gnnding
to 2" minus
Grinding
to I " minus
Gnnding
to 4" minus
Stage 3
Achve
composting
Active
composting
Active
composting
Stage 4
Screening
Stage 5
Cunng
Stage 6
Sales
Stage 7
Use
Screening
Cunng
Sales
Use
Re-grind
to 1 " minus
Active
composting
Curing
Sales
The system for composting can be chosen around equipment to fit the management's objectives. The number of options
alone are c o h i n g not to mention economics and efficiencies relating to each. Key factors to reaching a decision
include total site size, inflow volumes, production and site storage capacity and market demands for products. It is
obvious that equally marketable products from all the options listed only occurs on paper and that there will always be
significant physical differences from the different processes.
A process diagram helps to accurately compare economics of each oprion in an entire production system and how the
efficiency of each stage fits the particular compost factory. Breaking up the entire system into bite size chunks which
can identify throughput efficiencies, it is easier to understand and manage. By using such a template, factory owners can
assure themselves that the true cost of composting is calculated at each stage and that it is done the same way each and
every time. Finally, the use of data allows managers and workers to understand why each decision is made.
With Table 1 1.1 1, "what if' situations can be created to simulate efficiencies of stages types of equipment, which is
helpfid when the equipment salesman or consulting engineer visit. Remember that the compost factory manager's
objective should be to maximize inflow and outflow revenues while keeping total production costs (at each stage) as low
as possible. Municipal objectives may d 8 e r slightly because they may focus more on cost avoidance, but are generally
the same.
Further analysis of the options above is beneficial. Each stage represents a work station in a factory which is responsible
for ,g particular task. Getting all stations to work together as a team while maximizing revenue is the name of the game.
Therefore, a factory manage needs a measurement tool to analyze complete systems based on the whole as well as the
sum of it's parts.
5
Benchmarks for costs ofcomposting are not clearly identified due to the number of feedstocks, the number of processes,
and the vaned equipment available to process matenals When asked what it costs them to compost, most operators at
factories respond with unsui ity However, when asked what the average sales pnce for the end product is, most
operators are reasonably close It is common for production costs ranging from $1 O/ton to $40/ton for yard tnmmings
and over $2OO/dq ton for biosolids (Goldstein, 1993)
CHOOSING MARKETS
When compost factories have the l u m y of time to diver@ sales efforts, a concept worth considering is "highest and
best use". The concept is simple in suggesting the placement of finished compost in markets achieving the highest
return. Highest and best use is stnctly an economic focus for each factory and does not consider benefits of
diversification or other long term business strategies. An example of highest and best use for a new compost factory
opening soon with an annual production of 30,000 cubic yards is depicted in table 1 1.12.
Table 1 1.12 Choices for highest and best use of compost at a new compost factory with profit as the only motivator.
Annual Potential Markets Locally Available:
Totals
10,000yards Retail (@ $lS.OO/yd
20,000 yards Landscaper (@ $8.00/yd
10,000yards Nursery @ $6.00/yd
10.000 yards Topsoil @, $5.00hid
50,000 yards = $420,000
$1 50,000
$160,000
$60,000
$50.OOO
$420,000
The example is realistic in showing that even though retail retums $15.00 per cubic yard, it will only absorb about 1/3 of
the yearly production. The same is true as each successive market would be filled to capacity before moving on to a
lower priced market. Remember, this is a theoretical approach only and the time it takes to develop the above markets
are not taken into account in the example.
Many inexperienced compost businessmen make mistake of planning for 30,000 yards to be sold at the $15.00 per yard
retail level the first year. Market development takes time and therefore consideration must be given to promoting
products to a number of markets unless plenty of room is available for material storage. Diversification of a marketing
approach helps alleviate concems with inventory buildup and eventual overload from start up compost factories, but
makes it almost impossible to obtain an average sales price of $1 Ycubic yard. The example above could theoretically
yield $3 10,000from sales of 10,000yards to retail and 20,000 to landscapers. However, this would require 100%
market share in both market sectors, which is very unrealistic.
6
The following example helps identify esactly why a natural hierarchy already exists around each major market.
Table 11.13: Potential markets" in "Big City USA".
Yearly compost factory production
"Big City, USA" = 50,000 ydslyr.
Tvnical marketing questions:
What market wants the product the most?
What is the best marketing strategv?
What is the highest and best use?
Who will we hire to sell the product?
What type of quality does this market require?
How will the market use theproducts?
Dollar Markets:
Retail
Landscape
Nursery
Topsoil
sports turf
15,000 yddyr. @ $15.00/yd
75,000 yddyr. @ $8.00/yd
30,000 yddyr. @ $6.00/yd
50,000 ydslyr. @ $5.00/yd
20,000 vds/vr. @, $1 2.OO/vd
Tolal dollar TAB * * * = $ I , 495,000
Total volume potential = 190,0OOyds/yr.
Average price/cubic yard = $7.87
Volume Markets:
Silviculture
60,000 yddyr. @ $.50/yd
Roadside
60,000 yddyr. @ $4.00/yd
Landfill cover
20,000 yddyr. @ $3.00/yd
Agnculture
300,000 vdshrr. @, $.50/vd
Why WOUWthey buy our product?
Total dollar TAB*** = $480,000
Total volume potential = 440,000 ydshr..
Average pricehbic yard = $ 1.09
When do they need the product?
Total available business = 610,000yards
at an average price of $3.23 yielding a
revenue of $1,974,999. (These numbers are
considered to be total tnarkt TAB'S).
*Numbers used are examples only
**(Market TAB = Dollar TAB+Volume TAB This is calculated for both volume (cubic yards) and revenue)
***(TAB = Total available business in dollar sales)
Production from the Big City USA facility is only able to satisfy a total of about 8 6 % of the total market needs or 26%
of the dollar market needs in the above example There is no logical reason why the marketer at this compost factory
would choose Agnculture as the highest and best use market unless the product was not high enough quality for the
dollar or other volume marhets By choosing enough of the dollar markets to satisfy yearly production, a minimum of
$200,000 per year can be generated from product sales
Marketers should consider short term revenues compared to long term market share. For instance, when the first
compost factory is built in a market area with enough landscapers to purchase 100% of the annual compost productions,
p e d - c a n set in. "Jack up price!" say expert marketers from other industries. "Where else are they going to go to get
product?" is their logical argument.
7
Be careful! Professionals buying compost products remember history well and can become permanent prospects rather
than loyal customers if not treated fairly. Besides, dollar markets, when treated fairly, act like annuities on investments.
In this particular example, the marketer would be crazy to do anything but set a fair price and service priority accounts.
This strategy would ensure that even when competition came to town (in time, be sure that it will), the customers would
still see fair prices with proven service and would be reluctant to change compost suppliers.
The economic return from a successful marketing program also needs to be analyzed on a regular basis. For instance,
the example above which yields $700,000 in sales of compost to the dollar markets may not be worthwhile if cost of
personnel and supplies is $700,000. It may at times be better to d i v e r s e sales to lower paying markets, reducing
manpower needed, potential expenses, increasing the bottom line. The general rule is that "the more return in each
market, the more attention, effort and resources are needed to service it". This is especially true for servicing the retail
markets. Remember that "Retail is Detail". Markets left without service over time will begin to gradually reduce their
collective demand for products.
CONCLUSION
Economics are the dnving force to the compost business If the long term money-making potential is not available to
compost factory owners, composting will only be possible as the lesser of two options in waste management If the
economics of the compost business reveal that the composting option is less expensive or more profitable than other
formspf waste management, i t will be the leading form of recovery by the year 2000 If not, it may be reduced in
importance
The importance of understanding the economics of the compost business is paramount and the need for information is
urgent All employees of composting operations should be encouraged to understand the economics involved in the
business and contnbute ideas that help cut costs or increase revenues
The dual revenue potential ofthe compost business is only possible with the development and maintenance of permanent
quality markets whch buy quality products Market development, as a part of the nght side of this revenue stream, is
equally important to compost factones because there are non-financial PR benefits to having a stable market demanding
compost products With the help of a small consortium of green industry professionals in each market, the market
development objectives can be achieved, which in turn will help the compost factory owners achieve their financial
objectives
(This paper is an excerpt from chapter 11 of "Winnine the Organics Game-The Compost Marketers
Handbook", by Rodney W. Tyler, ASHS Press, 1996, For more information, contact Lisa Preston at 70318364606 ext. 309).
8
Comnostinv Process Models and Model ADDlications
Philip B. Leege
Chairman, Standards and Practices Committee
The Composting Council
Alexandria, VA 22314 USA
and
Composting Infrastructure Development Manager
The Procter & Gamble Company
Cincinnati. OH 45224- 1788 USA
Presentation to the "Composting in the Carolinas" Conference& Expo
23 - 25 October 1996 Myrtle Beach, South Carolina
ABSTRACT
To understand cornposting and the variety of approaches technology developers have taken with a variety
of compostingfeedstocks, it has been foundthat models and tablesmakethetaskeasier.
No longer need
composting remain in a black box of mystery and understanding. No longer need composting remain an art.
A series of Modelshave been developedthatilluminate feedstock choicesandfinished product
requirements, and that define the steps to managing composting operations and producing predictable
quality
product. The Models describe inputs to composting unit operations and outputs. The Models go on to describe
key elements and control parameters for insuring success.
Technologies that have been developed have been placed by industry representatives in five categories
that have common approaches to applying principles identified by the Models.
The Composting Models andTechnology Table pave the way to insights of understanding when
engineeringsystems, when evaluatingproposals, whenpermitting projects, when troubleshootingproject
operations, and when inspecting facilities.
Widespreaduse oftheModelsand
Table in thecompostingindustryanditsclients
canaid in
promoting a common understanding of composting, and
may help avoid the oversights, the misunderstandings
and the pitfalls that have led to poor operations and failures. Those who will benefit include project developers,
scientists and technology developers, equipment suppliers, engineers and designers, compost producers, product
testing laboratories, compost marketers, and regulators. With the knowledge imparted by the Models and Tables
the composting industry can move forward with increasing confidence in its ability to sustain success.
I.
Introduction
Models and Tables have been developed to illuminate steps and process management requirements to
insure production of predictablequalitycompost.Themodels
can be used asteachingaids,as
a meansto
understand the variety of approaches taken to composting technology development, as a guide to managing product
attribute development during composting, and as a guide to planning sampling and testing of feedstocks, process
management parameters and finished product. Their use is resulting in development of insights that lead to better
understanding of the process and products of composting. Their use is leading to a clearer understanding of the
impact feedstock choices and operating parameter control has on market attributes of compost products. Their use
may lead to development of least cost approaches to production of product for specific end markets.
2. The Composting Process Model
a. Background: A simple model was developed to illustrate the municipal-scale aerobic composting
process, as shown by FIGURE I . COMPOSTING UNIT OPERATIONS.
At the box in the upper le'ft comer of the schematic diagram, this first-level model shows Materials
Collected and Delivered to the Cornposting Facility. At the box in the lower right comer, Finished Product is
9
shown produced by the facility. In between, the composting process is shown by seven Steps, moving from leftto-right and top-to-bottom
Materials Collected and
Delivered to the Facility
D
1. Feedstock Recovery
7
I
D
4
2. Feedstock Preparation
I
3. Composting
Treatment
4. Odor
5. Compost Screening
I
6. Compost
Curing
*
fl
D
7. Compost Storing
and Packaging
\
Model First Level Detail
Finished Products
I
FIGURE I . COMPOSTING UNIT OPERATIONS (FIRST LEVEL MODEL)
Material Collected and Delivered to the Facility. Feedstocks can be chosen from one or more of the
following sources:
Food processing residuals
Manure and agricultural residues
Forestry and forest product residuals
Biosolids
Leaves, brush and yard trimmings
Grass clippings
Source separated compostable material
Mixed municipal solid waste
Compostqualitycontrolmeasuresnormally
begin outsidethecompostingfacility,tohelpinsure
compliance with finished product standards for the protection of public health and safety, and for environmental
protection and enhancement objectives. Measures include collection and delivery of clean compostable feedstock,
that contains a minimum of chemical and organic contaminants. Obtaining clean feedstock requires instruction and
training of waste generators and waste haulers; their cooperation determines to a large extent the level of these
contaminants in finished product. Success in the feedstock delivery infrastructure must be supplemented, however,
by central facility sorting to remove unavoidable mistakes that turn up in the materials delivery stream.
IO
Step 1 Feedstock Recovery is the final inspection and separation of chemical contaminants and residue
(physical contaminants) from the composting feedstock at the facility consistent with recovery objectives for quality
of compost and quantity of feedstock. Initial sampling and testing takes place here.
Step 2 Feedstock Preparation involves establishingconditionsforcomposting,and
mayinclude
settingthe initial carbon tonitrogenratio,managinginitialpH,initiatingmicrobialdiversitywithrecycled
compost. setting initial porosity, setting initial moisture content, and controlling odor and vectors.
Step 3 Corn posting involves pathogen treatment, feedstock degradation, and biological stabilization of
the compost. Pathogen treatmentinvolvestemperature exposurefor prescribed timeperiodsand may include
homogenization by turning and mixing. Management of biological activity can include porosity control, moisture
control,pileoxygencontrol,
pH control,microbialdiversitycontrolviatemperaturemanagement,and
homogenization.
Step 4 Odor Treatment is offsetto the right in the diagram. It is intended to preventrelease of
objectionable odor to atmosphere. It may involve collection of air from the process and other odor sources, and
treating it in a biofilter or other positive odor treatment system.
Step 5 Compost Screening and Refining is a finishing step that removes oversized material like stones
and bulking agents, and may include removal of physical contaminants (residue) down to 4 mm, including glass,
metal fragments, hard plastics, film plastic and sharps.
Step 6 Compost Curing is another finishing step to develop the level of compost stability required for
particular end markets, and to eliminate inhibitors to seed germination and plant growth. The sequence of Steps 5
and 6 may be, and often is, reversed to retain bulking material for its ability to maintain pile porosity as long as
possible to insure aeration for continuing the stabilization process and avoid odor generation.
Step 7 Compost Storing and Packaging allows adjustment to seasonal demands for finished product,
and may prepare compost for the “high dollar” markets with amendments and bagging.
TheFinishedProduct
that is produced fordistribution must be testedforcompliance
governmental regulatory standards and with market attributes and specifications.
The Composting Council Standards and Practices Committee has
systems, for all feedstocks, can be described by this model.
with
noted that all aerobic composting
The modelhas been expandedtothesecondlevel
with addeddetailasshown
by FIGURE 2 .
COMPOSTING UNIT OPERATIONS MODEL, to include process inputs and outputs for each unit operation. Inputs
include additives, air, recycled material used as inoculum, mixing and turning operations, water and sometimes
bulking material. and amendments. In addition to outputs already shown by the first level model, the second level
version shows traditionalrecyclablematerials,chemicalcontaminantsandresidues,andfrom
Step 4 Odor
Treatment, clean air exhaust.
11
-
Materials Collected and
Delivered
to the Facility
I
2. Feedstock Preparation
c
-1
1
Additive
I
Materials
Conlaminan&
i (7
(
)
7)
-
Air
m
4. Odor Treatment
Turning
and hflnng
c5
Exhaust
5.Screening
Compost
Air
1
and Refining
Residue
Curing
Water
J
6. Compost
)r 7. Compost
Storing
and Packaging
1
Finished Products
FIGURE 2 . COMPOSTING UNIT OPERATIONS MODEL (SECOND LEVEL MODEL)
Operatingparameters: Within each composting unit operation,operatingparametershave
been
identified as shown in TABLE 1. OPERATINGPARAMETERS. Theseare important tomanage and control to
insure operational success.
I
OPERATINGPARAMETERS
Set & Control the Carbon to Nitrogen Ratio
Mix Additives and Amendments
Set & Control Porosity
Set Particle SizeiAdd Bulking Material
Turn and Mix
Aerate
Control pH
Set & Control Moisture
Biological Activation
Control Temperature
Control Pathogens
Test Feedstocks and Compost
I
TABLE 1. OPERATINGPARAMETERS
Processcontrolparametersinclude
carbon to nitrogenratio,porosity,oxygen,moisture,and
temperature.Processmanagement includes particle size,additives and amendments, biological activationand
microbial diversity, turning and mixing, aeration, pH and pathogen reduction. Odor management is discussed in
two parts, odor control and odor treatment. The management of process control operating parameters is presented
in the Comppst Faciliv UperafingGuide and in the Composfing Technology Selection Guide.
A third level of detail is shown by Models not included here that list all process control parameters in
their appropriate place.
Sampling and testing of feedstock and material undergoing biological degradation is required to provide
the necessary data for process control.
3.
Model Applications
The modeling approach has been applied in several ways as an aid to understanding. These include the
descriptionoftechnologyapproaches
to composting,applicationsofsamplingandtestmethods,compost
attributes management, and to compost products identification.
Cornposting Technologv Croups
Technologies used for composting range over a broad spectrum of options. The composting industry1
has placed composting technologies into five groups, as shown in the TABLE 2 . COMPOSTING TECHNOLOGY
Cornposting
Manaptent
Approach
GROUP 1
GROUP 2
GROUP3
GROUP 4
GROUP 5
Weather
Protection:
Open
Open
Covered
Covered
Covered
Pile
Piles
Windrows
Piles
Piles and
Tunnels and
Tunnel and
Windrows,
Vessel Systems
BaysiTrenches
and Beds
Active Active Active
Active
Configuration:
Passive
Process
Management:
Biology
Management Nutrient
balance:
Porosity:
Moisture:
Oxygen:
'
8
Temperature:
Unmanaged
Undisturbed
Unmanaged
Unmanaged
Unmanaged
Initial C:N ratio
set
Turned
Water Make-up
Convective
Aeration
Initial C:N ratio
set
Static Structure
Forced
Aeration
Temperature
Control
Initial C:N ratio
Turned
Water Make-up
Forced
Aeration
Temperature
Initial C:N ratio
set set
Turned
Water Make-up
Forced
Aeration
Temperature
Control Control
TABLE 2. COMPOSTINGTECHNOLOGY GROUPS
The composting industry categorization of technologies is generic, and specific technology suppliers
offer variations within a technology group. A given technology can be and often is a combination of approaches to
the seven process steps.
The placement of' technologies into five groups basedon predominant composting unit operation characteristics is
an approachthatwasdeveloped
by peerreviewduringconsideration
of acompaniondocumentdeveloped
by The
CompostingCouncilandavailable
from thatassociationentitled Composting Facility Operating Guide.
13
In the US Conference of Mayor's ltf~m~cipal-.%ale
Composrrng: '4 Decision Mukers Guide to Technology
Selection, a number of projects are fully described using the model and accompanying text.
Sampling and testing plans must be designed to suit the specific approach used in each composting
project.
Sampling and testing marketable product provides the data needed to demonstrate compliance with
environmental standards andtoprovideusersinformationneededto
plan for properapplication of compost
products.
I
Sampling
and
Test Methods
Test methods have been developed for the broad range of data needed by processors and marketers.
Each test method is introduced with a header, TABLE 3 TESTMETHODSHEADER. The header shows the
Test Method name and Units of measurement and a check listof Test Method Applications either to the
management of process unit operations steps one to seven, andor to verification of Product Attributes for
compliance with safety standards or market specifications.
Units:
Test Method:
Test Method Applications
Process Management
Product Attributes
?;rep I
Stcp 2
Step 3
slep 4
Slep j
Step 6
Feedstock
Recovery
Feedstock
Preparat~on
Composting
Odor
Treahnent
Compost
Screening and
Curing
step 7
Safety
Standards
Compost Compost
Stor~ngand
Packag~ng Rehnmg
Market
Attributes
TABLE 3. TESTMETHODS HEADER
The columns extending down from the Header indicate by location of test name abbreviations the
Process Management step or the Product Attribute for which each test applies.
ComDost Attributes Management
Compostattributesmanagement
MANAGEMENT below.
is summarized in theTABLE
4.
COMPOSTATTRIBUTES
PROCESSING STEPS
THAT DETERMINE PRODUCT ATTRIBUTES
Step 2 :
Step 3:
Step 4: Step 5 :
Step 6 :
ATTRIBUTES
Feedstock
Collected
SAFETY
STANDARDS
Regulated chemicals
Pathogens
I 1
Step 1 :
Recovery
Feedstock Feedstock
Compostmg Odor
I Preparat~onI
I Treatment
I Screen~ng I Curing
and
Refinmg
X
I
X
X
X
X
Step 7:
I
Compost Compost Compost
Storlng
and
I
Packaging
X
X
X
X
X
X
X
X
X
I
I
MARKET
SPECIFICATIONS
Man-made inerts
Growth screening
Stability
Organic matter content
PH
Soluble salt content
Water holding
capacity
Bulk density
Particle size and
texture a
Moisture content
Plant food content
U
~
~~
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
TABLE 4. COMPOST ATTRIBUTESMANAGEMENT
Compost Products
Processors have developed a variety of value-added products as indicated by FIGURE 4. COMPOSTING
PRODUCTSMODEL.
15
Slaterials Collected and
Delivered to the Facility
-
#
I
* *
I
Recyclable Materials
B
++ 4. Odor Treatment
2. Feedstock
Preparation
I
1
Product Finished
3. Composting
I
I
r
5. Compost Screening
and Refining
6. Compost Curing
9
+ FinishedProduct
t
I
P
*
Finished Product
I
I
.
Model F~rst
Level Detal
#
7. Compost Storing
and Packaging
\
Finished Product
I
+
~~
FIGURE
4. COMPOSTING
PRODUCTS MODEL
An appropriate sampling and testing plan must be designed specifically for each finished product.
Conclusion
Use of the Models has left many to exclaim, "Now I understand composting!" Although variations
in its application to specific project approaches are many, it allows for an understanding of composting that
moves it from an art to a science, and may in time prove useful in avoiding project failures and helping to
insure the production of compost products with predictable quality attributes to serve reliable customer markets
and users.
16
INNOVATION AND UPDATE IN COMPOST MARKETING
AYEARMREVIEW
Ron Alexander
E&A Environmental Consultants, Inc.
Raleigh, North Carolina
An integral componentto any successful composting project is its product marketing or distribution program. As
compost has becomesa more household product, the number of successful programs has increased. In fact, successfid
compost marketing programs are commonplace, especially where the marketing program, and production of a quality
program is taken seriously. For instance, it has been estimated that80 - 85% of all the biosolids compostproduced today
is betng swcedUy marketed. This paper Hnll focus on outlining innovations in compost marketing and trends
which have
impacted the marketplace.
As a point of reference, it is important to first d s u s s marketing related challenges which haveaffected the success
of various marketing programs. By far, the two biggest reasons why compost marketing programs havefailed is because
of lack of product quality and lackof effort. Although producing a high quality product does not always assure that your
product will be effectively marketed, if an acceptable quality is not produced, it is unllkely that an effective program will
be established. It is important to realize that dflerent end users and applications have different requirements as far as
compost characteristics, and therefore a usable product forone customer may not be a usable product for another.To assure
the & & p n e n t of a long term market, your product must not only
be of high quality, but mustalso be consistent in nature.
The other major reason for marketing programfailure is a lack of effortor resources being provided for its development.
It is unportant to mderskd that k e with any start-up program,proper resources and effort mustbe made to assure a stable
base is developed from which to work. As the program grows, in a period of two to four years, the effort necessary to
improve and maintain the program ismuch less than at programinitiation. Other problems whch have affected compost
marketing are lack of market planning, lack of green industry (end user) knowledge, not following basic marketing
principles, regulatory barriers, and to some degree, product stigma.
One of the biggest trends in not only compost marketing but also production, deals with the variety of new
feedstocks being utilized inthe production of compost. Aside from yard trimmings,animal manures, biosolids and mixed
sold westes, substantial quantities ofsource separated organics, various agricultural by-products and industriaYcommercia1
by-products arenow being manufactured into compost. These new feedstocks have in some cases caused new process
challenges, but havealso provided products with some very specific and unique
characteristics. These new feedstocks have
often allowed for greater public acceptance and have allowed corporations to recycle more organicby-products through
composting.
Product diversification within specific facilities has also increased as an understanding of customer needs and
product applications have become better understood. Compost producers are now producing various productsat a given
facility. This is being done through blending with other products, various composting refrnement steps and varying the
amposhng process itself. It is commonplaceto tind yard trimmings composting facilities producing firewood, biomass fuel,
mulch and compost. f i s trend illustrates how compost facility operators are beginning to see themselves as product
manufactures and not wastemanagers.
Integratq cOmpOStinto mainstream products has also increased and has allowedfor greatermarket penetration.
Compost has become a component to commercially marketed growing media,topsoils and specialty blends. Compost has
even been used as a base for fertilizer products. The trendof integrating compost into mainstream products has increased
in both bagged and bulk products and for thoseproducts marketed on botha retail and commercial level,
Niche marketing of compost possessing unique characteristics has also improved to a great degree. Through
research and practical application, the industry has identified thepreferred characteristics for compostused by particular
end users for spec& applications. More and more compost producers have taken advantage of h s understanding and have
amcentratedUmr marketing effortson a specific enduser group or application which particularly suits their product. Other
17
compost producers and marketers have varied their cornposting process to affect product characteristics or have added
d t i v e s to produce a product which meets the specific needsof a particular end user group or application. For instance,
a compost ca% be finely screened for use as a topdressing. Nutnent rich feedstocks could be composted to the point of
stabilization, or until odors have been signrfcantly reduced, but not h l l y stabilized in order to retain a higher quantity of
nutrients for end users which desire larger quantities of nutrients. Ths trend of niche marketing willcontinue to grow as
new products and new product uses are developed and as an understanding of whch products are best suited for these
applications are determined.
There are also a variety of new rapidly expanding marketsin which compostmarketers have been exploiting to a
great *.
However, the most unportant &
e
th
c
hhas continued to expandat a rapid pace is the homeowner market.
Organic Gardening magazine has estimated that twenty seven million gardeners are now using compost. Thls product is
being purchased in both bulk and bag form througha variety of sources. Topsoil blenders and companies which produce
custom soil blends have increased their use of compost products. Topsoil and other custom blended products are being
marketed around the country fiom between $25 - $45 per cubic yard picked up at the blending sites. Products such as
garden soils, potting media, golf course and athletic field mixes are also being produced with compost. Environmental
applicaticmsfor compost have also increased to a great degree. Compost is beingused in erosion control. Finer composts
are bemg applied in liquid suspension and coarse products are being blown and bulldozed onto slopes. Composts arebeing
used in wetland mitigation, biofilters, stormwater filtrationas well as many other applications. Many of those applications
require compostproducts possessing specific characteristics and for that reason demanda hgher value. The agncultural
industry is also increasing its usage of compostin a slow but steady fashionas the benefits of organic matter are once again
b e q understood Compost is being used by row crop, small h i t , as well as tree fhut (orchards) farmers.These products
a~ not only being used as soil amendments, butalso as low-grade fertilizers, mulches and fungicides.
Compost is being established as a mainstream product in many areas of the country. As knowledge of positive
d
t
sspreads, the value ofcompostshould inaease. Many ofthe topics which we have discussed earlier, such as improved
product quality, niche marketing and creative applications for compost have allbeen established as a means not only to
market compost but also as a means to improve its value. The value of compost varies widely and is predominately based
on product q d t y , compehtion and customer type. However, overall, the price of compost has increased. On a nationwide
basis it appears that compost value is greatest on the westcoast and the northeastsections of the United States. Compost
brokas are typically payingW
e
e
n$1.SO to $19.00 per ton for compost, whileprofessional end users are paying between
$2.00 and $27.50 per cubic yard. Retail customers are purchasing product for between$4.00 and $35.00 per cubic yard,
plcked-up. Begged productis being marketed for betweenS 1 .SOand $4.00 per bag by mass merchandisers as well as local
garden centers. It is also common to see several lines of compost based products marketed in the same store. More
"designer" type products are being produced ona regional basis as are products with strong regional name recognition.
Many new tools have been developed to improve the marketablitiy
of compost. Best practices (instructions) for
the use of compost in specrfc applications have been developed, as have specifications for the products used in these
applications. The national Compostlng Council
is preparing to release several new tools such as the "Field Guide to Compost
Use", "Compost Enhancement Guide", "Farmers Guide to Compost Use", and a compost use video. These tools bring
cunpos&marketing and end use to a new level. Information on compostuse and marketing has even been made available
through the "Best Practices in Chrpstmg" wolkshops, developedby the CompostingCouncil, and the "Using Compost and
Other Organic Products"seminars, co-sponsored by the Composting Council andthe American Society of Horticultural
Science.
Ovaall,the markets and value of compostare in a growth mode. We now better understand the needs of specific
markets and requirements of specific end users. We are investing more time and the resources necessary to produce high
quality products. Greater creativity is being shown in the manufacturing and marketing of products. As these trends
continue, marketing success will also continue to expand. However, several marketing related challenges do still exist.
Challenges often arise where u p - h t planning and market research has notbeen completed and where poor quality products
are produced Typically, however,cOmpOSt marketingis most challenging at the timeof facility start-up or after a si&1cant
expansion of a facility hasbeen completed. Overall, compost procurement laws developed by public entities (federal and
state) have proven to be ineffective and time to time
facilities are still found "dumping"product onto the market at a price
far below its value. This af€ects product value and marketability in that whole geographcal area. However, overall,these
challenges are far outweighed by the successes we are seeing on a national basis. In as such, compost is starting to become
a household name and a mainstream horticulturaVagricultura1 product.
BIOFJLTER ECONOMICS AND PERFORMANCE
R. Allen Boyette, PE
E&A Environmental Consultants, Inc
Cary, North Carolina
INTRODUCTION
Biofiltration has proven effective at treating odorous gas streams emitted fiom various typesof facilities including
wastewater treatment plants, sewage pump
stations,solid waste processing facilities, and composting facilities. Widespread
acceptance of biofiltersystems has beenlimited due to mixed results and lack of understanding at some facilities(Williams
1994). Signhcant n
to
fr
m
a
o
itnand mderstmding of operating parameters has developed over the past few
years which has
led to more biofilter installations. Thn understanding has been obtained through pilot studies by vendors and owners on
existmg gas s t r e a m s , trial and m o r by operators at existing full scale systems, and published research byprivate firms and
universities. Most designers and operators of waste processing facilities have experience with other types of odor control
equipment such as thermal oxiduffs, chemical scrubbers,or activated carbon, and have found biofilters to be more effective
at treating odorous gas streams both in odor removal efficiencies and economically. As a result, numerous biofiltershave
been installedto retrofit existing waste processing facilities and included in the design of new facilities to provide effective
& control. "Ius paper outlines the economic considerations for a biofilter system and provides casehstory lnformation
including capital costs and removal efficiencies at operating waste processing facilities.
ECONOMIC CONSIDERATIONS
Several factors affect the capital and operating costs of biofilter systems. Thesectionsbelow
outline these
considerations as they relate to constructing and operating an open bedbiofilter system for odor control.
CaDItal
Pm-treatment - Pre-treatmentof gas streams to improve biofilter operations include removing particulatematter, cooling,
and humidlfying. OAen times some type of spray system, either coarse or atomizing nozzles, isused to pre-treat the gas
stream. Typical applicationsmay be at totally enclosed compostlng facilities for dust removal, for coolingof compost offgas,
and humidifying exhaust gas from various enclosed odorous tanks. Complex pre-treatment systems result in increased
biofilter system c o s t .
Concentration and Biodegradabilityof Compounds - Biofilters are effective at treating relatively low concentrations of
odorous compounds in exhaust gas from wasteprocessing facilities. Odorous gas streams from some facilities that may
result in lugh concentrations of particular compounds may result in increasing the size of the biofilter. This determination
is made by evaluating the mass loading and biodegradability of specific compounds to determine the sizeof the biofilter.
tncreasing the biofilter size will increase the capital cost of constructing the system.
Quantry of Air Being Treated - Generally, themore air being treated, the greater the size and cost of a biofilter system.
Removal EfjciencyRequirements - Normally the design basis for an odor control system is to remove as many odorous
compounds as possible. In some applications a lower removal efficiency may be deemed appropriate for.reducingodor
problems, whdein other applications a greater safety factorto ensure maximum achevable odor treatment
may be desired.
These design considerations will effect the biofiltersize and cost.
Ductwork - OAen times the cost to collect and transport the odorous gas fiom the source to an area appropriate for the
biofilter is actually more expensive than constructing the biofilter itself Ductwork will normally be constructed fiom
currosion resistant materialssuch as plastics, fiberglass, stamless steel, or aluminum. The furtherthe odor source is located
fiom the biofilter site, the hgher the ductwork cost.
- Space limitations may result in requiring walls to contain the media,special earth work techmques, or
equipment access concerns that could increase the construction cost of the system.
Avoifobfe Spoce
- A hgher degree of automation for monitoring such process variables as temperature,
pressure, auflow rate, or equipment status will result m increased capital costs.
Degree ofAulpmotion Desired
- The degree of flexibility for biofiltersystems normally includesthe number of blowers or the number
of biofilter cells. Generally, the greater the flexibility in the total system, the greater the capital cost. ThIs results from
increased ductwork costs, increased installation costs, and increased airdamperdcontrols.
Degree o/f;leubili!y
Design Foctors - Design factors such as detailed pre-treatment systems, unusual site conditions or complex collection
systems may result in lncreasedenpeering costs. In addition, such factors as pilot studies or permitting requirements may
increase capital costs.
QDeratine Costs
Elecbiciv - Generally, electncity to operate the blower(s) is the largest portion ofthe operating cost for a biofilter system.
Electricity for water pumps, controls, etc. willadd minimal cost.
Medio Repfucement - The second largest operating cost is generally media replacement. Depending on various factors,
m d a r e p l m e nwdl
t typically occur afterseveral years of operation. The cost for media replacement consists of removing
the old media,obtaining new media, and placing the new media.
Periodic Inspection ond Testing - Labor
and laboratorycosts associated with monitoring and checking the biofilter system
are typically minimal.
Equipment Mointenunce
- There a few mechanicalparts associated with a biofilter system.As a result, maintenance costs
are typically minimal.
Sidesmom Treoment - The only sidestreamrequiring further treatment is wastewater from the biofilter drain system. llus
amount is normally small andresults in minimal cost. There is no disposal cost for the media as it does not require further
treatment prior to uses such as landscaping.
CASE HISTORIES
Several facilities have recently constructed open bed biofilter systems forodor control. Most facilities have installed
open bed systemsinstead of totally enclosed systems foreconomic reasons. The increased process control provided by
totally enclosing a biofilter has
not justified the additionalcapital expenditure as documented by the successful odor control
by numerous open bed systems. The reasons for installation of biofilter systems varyfiom facility to facility and include:
reacting to odor complaints from neighbors, installing odor control to reduce odorous emissions from new facilities, and
complying with regulatory requirements. The technique used for reducing overall odor emissions from waste processing
facilities varies from facility to facility. Some facilities collect and treat the most odorous gas streams as is the case with
amymstmg facdities that operate with negahve-on
and treat gas pulled throughthe compost piles with a biofilter. Other
fechties have pinpointed speclfic areas w i h a facility that result inthe most si@kant odorous emission and collect gas
from that source and treat with a biofilter as is the case with covering various type tanks and treating exhaust through a
biotilter. Some facilities totally enclose the entire treatment area and collect all of the building air. This is the case with a
totally e
n
c
o
ls
e
dcompostlng facility whichtreafs all bddmg exhaust through a biofilter system. Table 1 summarizes the case
histmy lnformntionby outhung the destgn and optxahng data forseveral facilities as well as the capital cost and the removal
efficiency where available. Of the facilities descnbed, several have not conducted d e t a ~ l e dtesting for odor or speclfic
ccmpomd removal efflciencles. This generally results from the analytlcalcosts involved in conducting such testing. As a
result, actual data m spec& compound removal efficiency is lirmted. More subjective analyses from owners and operators,
such as there are no odors fiom the biofilter surface and no
odor complaints since the biofilter was installed, have been used
to evaluate biofilter effectiveness.
The capitalcosts indicated in Table 1 are the total capital cost for the biofilter system including design,construction,
and startup. The odorous gas collection system fcr each case isnot included in the capital cost as collection systems vary
fn>m slmple ductsto elaborate ducting and controls. The inclusion of collection systems can sipfkantly increase the cost
of m s t a h g an odor control system and would be required with any odor control technology selected. Therefore, including
the collection%stem costs may skew the biofilter cost data and not accurately allow comparisons of capital costs between
different odor control technologies. Operating and maintenance (0 & M) costs for biofilter systems are generally not
tabulated by operators. Therefore, actual operating costs are difficult to determine. The major operatingcost for a biofilter
is normally electricity to operate the blower followed by periodic media replacement. Through the use of locally available
materials, facilities are able to lower &a replacement costs. Detailed economic analyses have been performedfor biofilter
systems to emmate 0 & M costs. These estimates are normally accurate because electncity use is easily calculated. Total
0 & M costs normally range &om $2 - $14 per CFM of exhaust gas treated (H’illiams and Boyette 1995). The following
sections describe variousbiofilter systems.
Cape Mqv Counw hiunicipal Utilities Authoriv (C.LiCAUUA),Cape . k i q Court House, NJ - CMCMUA operatesa 20 dry
ton per dav m vessel composting facility in Cape May Court House, New Jersey. Biosolids are compostedin an in-vessel
system for 14 days, followed by an aerated static pile curing process for 21 days. Fourteen days of aerated curing is
performed under negative aeration with exhaust gas treated through a biofilter system. The negativeaeratlon used in the
cunng process is accomplished through the use of contmuousiyoperating blowers. The biofilter was designedto treat a total
of 2,400 CFM at a loadmg rate of 4 C M S F . Pre-treatment of the exhaust air is accomplished through either of two spray
chambers designed to cool the exhaust gas prior to treatment by the biofilter. The exhaust air from the curing blowers is
collected through a ducting system maintained under negative pressure by two biofilter blowers. Each of the biofilter
blowers serves either of two equal size biofilters. The biofilter media consists of locally available yard waste compost and
wood chps. The biofilter was placed in senice in July 1996 and was constructed for a total capital cost of 949,800. The
biofilter has been treating odors with the operators commentingthat no odors &om the biofilter surface are noticeable.
Performance testing of the biofilter system is scheduled for September 1996 (Donojrio 1996).
Centml C o n m Costa Sanitary Dirbicl (CCCSD),Martinez. CA - CCCSD operates a 45 MGD activated
sludge secondary
wastewater treatment plant OKWTp). To reduce odorous emissions from the facility, CCCSD installed covers on three
k l v e d au flotation (DM)tanks. A ducting system was installed to collect odorous air and reduce corrosion inside the
t a n k s . The biofilter system treats 3,500 CFM of odorous exhaust gas. The system consists of in-line spray nozzles to
inrrease hurmdity of exhaust gas and two equal size cells totreat the odorous gas. The media consists of locally available
yard waste compost and wood chips. The biofilter is 700 square feet and designed at a loading rate of 5 CFM/SF. The media
is fourfeet deep andthenominal open bed residence timeis 48 seconds. System pressures and temperatures are
continuously monitored and recorded. The biofilter began operation m July 1996. The total capital cost of the biofilter
system not including covers or collection ducting was $ 129.700. Performance testing of the odor removal efficiency of the
system 1s scheduled for September 1996 (Kaweah 1996; Pomroy 1996).
Davenport. Iowa - The city of Davenport operates a28 dry tons per day aerated static pile biosolids composting facility.
The m h g and compostmg areas are totally enclosed with 2 10,000CFM of exhaust treated through a biofiltration system.
The system i n c l u d e s two separate biofilters with each one divided into four separate cells. Each cellhas its own individual
blower mth an in-ltne spray d
e for humidification. The biofilter media consistsof yard waste compost and wood chips
and is four fwt deep. The biofilter was designed at 5 C M S F and the total treatment area of the biofilter is 42,000 square
f i . The b1oNter system was constructed for S495,500and began operatlons in June 1995. Odor removal testing on two
cells was conducted in October 1995 and the resulting removal efficiencies averaged 86% (Plert 1996; Zarn 1995; E&
1996)
-
E a c r Ifampron, New York East Harnpton operates a35 tons per day agtated bed municipal solid waste (MSW)hiosolids
cornpostmg fncdity. MSWhiosolids composting is conducted inside a totally enclosed building. A biofilter is located
adjacent to the b d h g and treats 50,000 CFM of building exhaust gas. The faclllty began operations m March 1995. The
biofilter media consists of wood c h p s and leaf compost with media placed three feet deep. The biofilterwas designed at
5 CFM/SF wth a mhce tune of 36 seconds. The total capital cost of the biofilter was SI 35,400. No odor testing of the
system h a s been performed, but facllity operators have not noticed anv odors Gorn the biofilter surface (Alix 199.5).
21
Everen Washington - The city ofEverett is constructing a biofdter to treat odorou~emissions fiom the head works
areaof
the W W T P . The biofilter was designed to treat 15.000 CFM of exhaust gas at a loading rate of 2.67 C M S F . The media
w
l
ibe placed fourfeet deep and the residence time will be90 seconds. The media will consist of locally available compost
and wood chips.Pre-treatment of the gas consists of in-line spray nozzles for humidification. The biofilter consists of two
separate 2.8 10 SF cells with each cell having its own individual blower. The biofilter is scheduled to be operational at the
end of 1996 (Saner 1996).
Ham'sonburg - Rockingham Regional Sewer Authority(HRREA),Mount Crawford.VA - HRRSA constructed a 5.5 dry
tansper day biosolids composhng facility whichbegan operations in December 1995. 3,150CFh4 of exhaust gas fiom the
compostlng process is collected and treated through a biofilter system to reduce odors fiom the compost facility. The system
collsists of a spray chamberto humid@ and cool exhaust gas. The biofilter was designed at a loading rate of 4 CFM/SF and
is 790 square feet The &a mnsists ofbiosolids cOmpOStand wood chips and was placed four feet deep. The system was
d
e
d for a total capital cost of $58,000 (Hannan 1995).
Hoosac Water Qualiv District, M A - Hwsac operates an aerated static pile biosolids composting facility. The facility
received numerous odor cornplaints fiom neighbors of the facility. As a result, four biofilters were constructed to treat
15,600CFM of compost p'ocess exhaust gas. The biofilter m d a consists of locallyavailable wood chips and leafcompost
placed three feet deep. The biofilters wereplaced in service in 1992 and have eliminated odor complaints fiom neighbors
of the fachty. Odor removal efficiency by the biofilter has been measured at 61% to 94%. Hoosac is currently expanding
the capacity of the composting facility which will include'construction of additional biofilters for odor control fiom the
additional composting areas (E& 1993).
-
Rivanna Water andSewer Authority (R W U ) , Charlottesville, VA The RWSA operates a 15 MGD pump station located
a d p e n t to the R ~ a n n a h v in
e rCharloaesvllle, Virginia. Neighbors are witiun approximately 150 feet of the pump station
and had complained about odorous emissions from the wet well. Based on capital constraints, RWSA initially installed a
counteractant agent spray system which resulted in a slight reduction in odor problems at the facility. In 1995 RWSA
lostalleda biofilter system to treatthe 2,825 CFM of wet wellexhaust to provide more effective odor treatment. The system
includes a spray chamber to humidify the air. The biofilter was designed at 5 C W S F and is 565 squarefeet in size. The
system began operations in September 1995. Odor removal efficiencies were measured at 76% in October 1995. Since
the biofilter has been in operation, no odor complaints have resulted fiom the pump station. The lower odor removal
efficiency was due to low odor levels of the inlet gas, 75 D R . The outlet odor level was 18 DR which is typical of well
operating biofiltas. The biofilter was constructed by the authorityfor a total capital cost of $4 1.300 (E& 1995; Wescoat
1996).
Seviervrlle, TN - Bedminster Corporation operates a 225 tons per day municipal solid waste and municipal biosolids cocomposting facility in Sevierville. Tennessee. The MSW and biosolids are loaded into an in-vessel composting system
followed by an aerated static pile curing. The aerated static pile curing occurs in a totally enclosed building with 80,000
CFM of blllldmg exhaust
btated through a biofiltration systern The biofilter is comprised of two blowers and fiveindividual
cells wtuch are approximately 3,960square feet each and was constructed in 1995. Performance testing of the biofilter was
conducted in 1996. Odor removal efficiency of 91% was obtained. Specific compound removal efficiencies were also
measured with a total volatile organic compounds (VOC's) removal efficiency of 93% obtained (E& 1996).
I/MsyN. Wiarnanrlo. H I
- UMSYN operates a food waste digestion facility in Wiamanilo, Hawaii.
In an effort to reduce
odorous emissions fkom the facility andresulting off site odor impacts, the facility installed covers over the receiving tank,
two storage tanks. and the hervest tank. A ductmg system was installed to collect odorous air for tceatment by a biofilter
system A temporary biofilta was cmstrwted in two weeks utilizing onsite personnel and local contractors to meet facility
permit requirements. The biofilter was designed to treat 2,500 CFM of exhaust gas. The biofilter is 625 squarefeet and
b g n e d at a loading rateof 4 CFM/SF with medra lhree f& six inchesdeep. The media consists of compost andovers fiom
a local yard waste cornposting facility. The temporary system was installed for $1 1,400 not including tank covers and
collation ductmg. The system began operations in September 1995. Performance testing was conducted in October 1995.
Inlet odorconcentratmnsranged from 13,700 to 25,100 D/T and a 82% removal efficiencywas obtained. A total reduced
sulfur (TRS)removal efficiency of 9 9 9 h was also obtained (E& 1995).
22
-
Western Lake Superior Sanitary District (WLSSD), Duluth, MN - The WLSSD operates a45 MGD WWTP. The facility
has received odor complaints from residents in Duluth's lower west end neighborhood resulting fiom the W W T P . In ongoing effortsto
odorous emission hthe plant, the distnct isinstalling a biofilter system to treat exhaustgases fiom
the building enclosingthe g n t room, the sludge hckener room, and the in-feed screw pumps. Wastewater channel air is
m
a
U
y used & make-up air for a solid waste incmerator.In the event the incinerator is down for maintenance,the channel
air will be diverted to the biofilter s y s t e m . Phase I of the exhaust collection system includes ducting fiom thechannel air,
gnt mom, and thickener room. Phase I1 of the exhaust gas collection system will include mtluent screw pump covers and
duchng to the biofilter system. The biofilter system is designed to treat 50,OOO CFh4 of exhaust gas with hydrogen suifide
concentration d
at 1 - 20 ppmv. Exhaust gas is pre-treated through a spray chamber designedto increase humidity
and m o v e particle matter prior to treatment by the biofilter. The spray chamber consistsof an existing concretechannel
that was moddied witha compressed airhater spray n o d e system. The biofilter system includes three individual cells with
each d e s i g n e d to treat 16,670 CFM of exhaust air. The biofilter is 1 1,800 square feet and designed at aloading rate of4.2
C M S F . The m d a c0I)siSts of yard waste produced by the distnct and wood chips from a localpaper mill. The media is
four feetdeep with a nominal open bed residence tune of 57 seconds. Construction of the biofilter system beganin August
19%, and thesystem is anticipated to be on-he by November 1996. Total capital cost of the biofilter system was $387,000
(Hamel 1996).
SUMMARY
The case histories discussed outline biofilter systems that have been successhl in treating odorous exhaust gas from
various typesof waste processing facilities. Table 1 outlines the design and operating data as well as the capital cost for
these fecllities. odor removal efficiencies have rangedfrom 76%to 94% for the five biofilters tested. TRS compounds have
been reduced by 99% or greaterat the two facilities tested. One facility achieved a 93% VOC removal efficiencies. Ths
data, as well as operator comments, lnckcate that open bed biofilter systems are effective atreducing odorous emissions from
waste processing facilities.
The capital cost of a biofilter system is b a d on several factors including type and quantity ofexhaust gas being treated
and locai slte conditions. Table 1 shows the capital cost for several biofilter systems. Figure 1 shows the capitalcost range
per CFM of exhaust gas treated. Unit costs for smaller biofilter systems are higher due to a greater percentageof the cost
resulhng h m engineering and contractor mobilization. For small biofilters treating less than 15,000 CFM of exhaust gas,
cap~talcosts range from approximately $10 to $38 per CFM of air treated. For large biofilters treating more than 100,000
CFM of evhaust gas,capid costs range h m approsimately $2.50to $5 per CFM of air treated. Figure 2 showsthe capital
costs per square foot of biofilter surface area. For smaller biofilters, capital costs range from approximately $45 to $185
per square foot of bioiiltersurface area. For larger biofilters, capital costs range from approximately 6 12 to $20 per square
foot of biofilter surface area. These capital costs can be used for budgetary estimates and for comparison with other odor
control technologes.
Based on the continued documented effectiveness of biofilter systems, more waste processing facilities will view
biofiltrahon as an economically favorable odor control alternative.
23
24
n
+
W
a
w
U
I-
0
LL
5
LL
U
0
e
W
+
0
v)
J
0
-ae
I-
a
0
W
U
Wr13/$ 'IS03lWlldtl3 W101
3
3
3.
n
N
N
3
3
?
N
3
3
9
0
0
v)
b
v
0
0
N
9
v)
0
>
a
W
a
a
IW
2
I-
E
a
a
W
LL
II-
0
O
U
0
W
a
a
v)
3
d
a
W
I-
n
v)
0
0
a
n
k
a
0
W
U
K
W
U
-
3
c3
26
I
0
0
0
9
ON
0
0
r-
9
In
Alix, C. E b A Environmental Consultants, I ~ c .1996. Biofilter construction cost for East Hampton Compost Facility.
Personal communication.
D0nofi-10,L.
Cape May County Municipal Uhbties Authority. 1996. Biofilter constructionc o s t s . Personal communication.
E&AEnvironmental Consultants, Inc. 1993. "Perfortnance
Williamstown, Massachusetts." Internal document report.
Testing of BiofiltmHoosacWater
Quality District,
E&A Environmental Consultants, Inc. 1995. Rwmna Pump Station biofilter odor panel results. Internal data.
E&A Environmental Consultants, Inc. 1995. UNISYN biofilter air testing results. Internal data.
E&A Environmental Consultants, Inc. 1996. "SummaryReport of Biofilter Testing at Sevierville, Tennessee." Internal
document report.
H a m e l , K Westem Lake SuperiorSanitary District 19%. WLSSD biofilter planning and design. Personalcommunication.
Harman Construction. 1995. Schedule of values for HRRSA dewatering and cornposting facility construction.
Kaweah Construction Company. 1996. Schedule of Value for CCCSD DAF OdorControl Project.
Plett, S . City of Davenport CompostingFacility. 1996. Compost facility biofilter operations. Personal communication.
Pomroy, J. Central Contra Costa Sanitary Distnct. 1996. DAF biofilter operations. Personal communication.
S e s s e r , L. E 3 A Environmental Consultants, Inc. 1996. City of Everett Waste Water Treatment Plantbiofilter. Personal
communication,
Wescoat, N. Rivanna Water and Sewer Authority. 1996. hvanna Pump Station biofilteroperation.
communication.
Personal
Williams, T.O. 1994. "Biofiltration for Control of Odorous Emissions and Volatile Organic Compounds (VOC's)From
Wastewater and Sludge processing Facilities." Presented at Water Environment Federation Specialty Conference series
on
odor and VOC emission control formunicipaland industnal wastewater treatment facilities.April 24 - 27, 1994,
Jacksonville, Florida.
Williams, T.O. andBoyette, R.A. 1995. "Biofiltration forthe Control of Odorous and Volatile Organic Compound
Ermsslons in Ngh Temperature Industnal Applicatlons." Presented at the A
M 88th Annual Meeting, June 1995, Sari
Antonio, Texas.
Zam, B.
Estes Companv, 1995. Actual costs for biofilter at Davenport, Iowa composting facility. Personal communication.
27
ENHANCED BIOFILTER DESIGN FOR CONSISTENT ODOR
AND VOC TREATMENT
Larry Finn
Vice President of Engineering
Bedminster Bioconversion Corporation
Marietta, Georgia
Robert Spencer
Director of Project Devleopment
Bedminster Bioconversion Corporation
Marietta, Georgia
Introduction
Biotilters are recognized by an increasing number of state air quality regulatory agencies as ”best available control
technology” (BACT) for treatment of volatile organic compounds (VOCs) and odor. This has been the case for two cocomposting facilities permitted by Bedminster Bioconversion Corporation in Cobb County, Georgia, and Marlborough.
Massachusetts. Both areas are
in ozone non-attainment areasas defined by the U.S. Clean Air Act, and therefore, since such
operations have the potential to emit VOCs, ozone precursors, air quality permits are required.
Pottntial VOC emissions from MSW composting plants are estimated
be to
only 0.05% of total MSW tonnage processed
(Kissel. 1992;Eitzer, 1995). Although thereis little published data on VOC emissions rates from biosolids composting, it
has been estimated that compostingof biosolids generates only0.2764 lbsidry ton of VOC emissions (E&A Environmental
Consultants. 1994). Despite theselow emission rates, they are enough to trigger regulatory review for facilities such
as the
Cobb co-composting plant where 300 tons per day of municipal solid waste are processed with I50 tpd of municipal
biosolids, thereby creating the potential to emit approximately 49 tons per year of VOCs. Other literature documents
biotilter treatment efficiencies for VOCs of 65 to 99% (Wheeler, 1992;Williams and Miller, 1992;Amiron. 1994).
Lessons Learned
A properly functioning biofilteris teaming with both macro and microscopic biologicalorganisms, the work horses of
this pollution control technology. But, as Bedminster and other biofilter operators have found, to maintain a biofilter in
optprrmal operating condition requires considerable care and feeding to provide food, air, and water. Bedminster’s Sevierville,
Tennessee co-composting facility hasbeen operating since October 1992, andup until December 1995, the facility treated
exhaust air with conventional biofilters. Those four years provided valuable experience which ultimately led to the
“enhanced” biofilter designused to retrofit the Seivierville biofilters, and installed at
new
theCobb County. Georgia facility.
Once a biofilter is operating at reduced rates of odor removal efficiency, the difficult decision becomes determining
the
point at which it is necessary to take more extensive corrective action than adding new media.
In locations where there are
residences or businesses within “smelling distance” of the operation,it is a sure bet the decisionwill be heavily influenced
bq those neighbors.
Corrective actions to rejuvenate a biofilter are usually performed in the following order:
I.
Addingmoremedia to the top ofthebiofilterto
compensate forsettling
3
-.
Remixing of the mediatoregainporosityand
3.
Replacement of the mediaoncemixingisnolongereffective
4.
Reconstruction of theunderlyingairdistributionsystem
distribute moisture
28
Considering that conventional biofilter design has media overlaying a system of air distribution pipes, remixing and
replacement of media requires costly excavation of the biofilter. For larger biofilters such as the 30,000 square foot of
conventional-biofilter previously employed at Bedminster’s Sevierville, Tennessee co-composting facility, such maintenance
activity proved to be necessary more frequently than originally planned.
The other downside of such remedial maintenance was the time it took to do the work, and the fact that a substantial
portion of the air treatment system was taken off line for at least several days, further taxing the remaining biofilters.
In the
Sevierville situation, since there were three separate biofilters, sufficient redundancy remained to allow for continued
treatment ofexhaust air during such maintenance. However, many composting facilities
are served by a single biofilter which
is not designed and constructed to allow for maintenance
on a portion ofthe filter while the remaining portions still function.
Recognizing thehndamental importance of maintainingan optimally functioning biofilter in a cost-effective manner,
especially for a450 tpd co-composting facility located adjacent
to a residential areaas is the Cobb County plant, Bedminster
designed, patented, and constructed biofilters for both the Sevierville and
Cobb facilities which have proven tobe superior
in performance than the conventional design first employed at the Sevierville operation.
Room for ImDrovement
During the design phase of the Sevierville facilityin 1989, the prevailing wisdomof consultants and literature was that
at a loading rateof4 to 8 cfm/sf. the mediain a biofilter would only have to be replaced every
3 to 5 years. This information
was based primarily on biosolids composting facilities, not MSW composting, and the fact that there are biofilters at
biosolids composting operations which hnction well with older media.. However, Bedminster’s Sevierville biofilter
degraded the wood chiphark mulchkompost media within2 years to the point that a sample of hardwood chips from the
filter media could be squeezed with two fingers into a mineralized pile of humus. The reason for such high rate of
degradation is not known, but it may be that the exhaust gasses from MSW composting provide a food supply for the
organisms which results in a more diverse range of organisms, hnctioning at a higher metabolic rate
Another problem was drying of the media, which is some situations resulted in devleopment of cracks in the media,
something that surface irrigation could not repair. Apparently the warm building exhaust gasses,
combined with exothermic
heat released by the microorganisms, resultedin differential rates of drying on the lower
side of the biofilter, which set off
an exponential drying effect. Such differential dryingis attributed to two “spiral effects” by Ned Ostojics of Odor Science
& Engineering in a recent issue of BioCycle, such that moisture migrates to areas of lesser air flow, with those areas
becoming more moist, further reducing air flow rates. Simultaneously, at different locations, dryer areas with less flow
resistance become even more dry (Goldstein, 1996).
Bedminster’s experience at the Sevierville facility also showed a build-up of fine dust particulate in the pipes, the
underside ofthe filter fabric( which was intended to keep biofilter media from washing down
to pipes), and the media itself.
This contributed to increased back pressure as air flow was impeded by the accumulation of dust particles.
These operational realities took their toll on the first generation of Sevierville biofilters, and the company spent
considerably more money than anticipated replacing and rebuilding the biofilters in the first four years of operation.
Pre-treatment and humidification
At the Cobb County facility, eachofthe six blowers which feed the biofilter with 35,000 cfm of exhaust air, force cocurrent air and water through six himidification towers packed with plastic media. This pre-treatment step serves to:
I.
Humidify
the
stream
air
-.7
Scrubparticulate
out
3.
Reduce temperature of
the
Remove
4.
VOCs
exhaust gasses
The decision to install the humidification towersat the Cobb plant was based on the successful resultsofa pilot scrubber
u n i t installed at the Sebierville facility to treat exhaust gasses from one of Bedminster’s Eweson digesters.
Sevierville Biofilter Performance
Unlike the Cobb biofilter, Sevierville’s doesnot yet have a humidification pre-treatment system. Instead, the media is
kept moist by surface irrigation. and turning with the Compost-A-Matic turning machine.
Some form of pre-humidification
maybe added in the future, but after nine months of operation
the filter is performing very well even without
the
humidification towers.
To document the performance of the new Sevierville biofilter, Bedminster contracted with E&A Environmental
Consultants of Cary.
N.C. to perform air flow measurements, and quantify volatile organic compounds (VOC) removal rates.
Samples were also collected for odor panel analysis
of biofilter inlet and outlet gases.The E&A monitoring was performed
in late February 1996, three months after the filter started operation.
The Sevierville biofilter consists of 5 rectangular bays approximately 200 feet in length and 20 wide, with an average
media depthof3 feet, anda total surface area of
20.000 square feet. Two40,000 cfm blowers deliver80,000 cfm of building
exhaust air into the base of the filter. resultingin a loading rate of 4 cfmkquare foot, with a design residence time forthe
gasses of 15 seconds.
E&A determined that the average removal rate
of total non-methane VOCs was 93.5 percent, based
on an average inlet
VOC concentration of 33 ppmv. and an outlet (top of biofilter) VOC concentration of 2.15 ppmv (results reported as
conce?trations in parts per million on a volumetric bases of total non-methane organics per EPA Method 25C). E&A’s
report concluded that “the data clearly justifies the
need for VOC treatment of exhaustgases from the facility and thatthe
biofilter system is working very effectively at reducing the quantityof VOC’s discharged.”
The average odor removal efficiency was determined to be 91 percent based on an odor panel determination of 354
D/T
of the inlet air and32 DIT of the outlet air (top of biofilter).
At the time this paper was duein early August, such independent testing of theCobb biofilter in combination with the
humidification towers had not yet been performed. However, it is expected that such information will be presented at the
conference in late October.
Air Oualitv Permits
The Atlanta metro-region has been designated
by the U.S. EPA as an ozone non-attainment area. and therefore
Bedminster’s Cobb County co-composting facility was required to submitan air quality permit application as a potential
source of VOC emission. For the purpose of the air quality permit applicationto the Georgia Environmental Protection
Division, it was assumed that the biofilters (not factoring
in the humidification towers) would impart 75% treatment
efficiency for VOCs.The following major permit conditions are intended to keep the biofilter
in optimal operating condition:
The temperature of the air stream flowing to the biofilter shall not Iexceed
1 3 dgrees F during any operation of the facility.
The pressure drop across the biofilter shall not exceed 8 inches of water during any operationof the facility.
The average bed depth of each biofilter bay shall notbe less than 30 inches during any operation of the facility
A water sprinkling system shall be installed for the purpose of maintaining the properbed moisture content.
The permit requires contiuous recording of tempreature and pressure drop, and daily recording
of the bed depth in each
of the seven biofilter bays. There are no emission monitoring requirements in the permit, and there is no regulated odor
standard in Georgia.
The Commonwealth of Massachusetts, where Bedminster
is curently seeking permits for
a co-composting facility for the
City of Marlborough. Massachusetts(80 tpd MSW and 40 tpd biosolids), publlisheda draft “Guidance and Policy for the
Evaluation of Odors at Composting Facilities”. It proposes that composting facilities use5 dilutions to threshold (DIT) as
the minimum design standard for odor at the property line (or most sensitive receptor if approved by the DEP), based on
literature references, which citea D/T of 5-10 as the level at which complaints can begin to be expected at many sites. The
policy requires use of air quality dispersion modeling
(EPA approved ISCST model), and for biofilters
the assumed emission
should be not less than 50 DIT on average. unless other adequate information is submitted.
Therefore, Bedminster’s air quality permit application for the Marlborough facility assumed
a biofilter emission rate of
50 DIT, even though actual emissions as measured at the Sevierville facility were 32 DIT.
The Massachusetts DEP guidance document also recommends that biofilters be designed as follows:
Loading rate not to exceed 3 cubic feet per minute per square foot.
Pre-scrubbing to prevent excessive ammonia and particulate loading
Empty bed detention time of 45 - 60 seconds, with 3-4 feet of media.
Provide for short term contingency for routine replacement of the mediia, or
catastrophic
failure.
The design proposed for Bedminster’s City of Marlborough facility complies with these recommended design standards.
For addtional “odorinsurance”, Bedminster is also proposing that the biofiiter
be covered, andtwo roof ventsused to further
dilute and disperse the biofilter off gasses. It is anticipated that this facility will be operational in mid 1997.
Conclusions
Biofilters treating MSW composting facility exhaust air may require more extensive management than biofilters treating
a more homogenous exhaust stream such as that from a biosolids composting facility.
Construction of an above-ground “managed” biofilter allows for periodic mixing andreplacement of media, and thus
maintenance of the biofilter in optimal operating efficiency.
Pre-treatment of exhaust gasses with humidification
may help maintain the biofilter in optimal operating efficiency by
removing dust particulate, humidifying and cooling the air, as well as scrubbing out some VOCs.
References
Klssel. J.C.;C.L. Henry & R.B. Harrison. 1992. ”Potential Emissionsof Volatile and Odorous Organic Compounds From
Municipal Solid Waste Composting Facillities”. Biomass & Bioenergy Vol 3. Nos 3-4, pp 181-194, Pergamon Press Ltd.
I992
E&A Environmental Consultants. Unpublished data prepared for permitting Phelps Dodge Composting Facility. Brooklyn,
N.Y. 1994.
Wheeler. M.L. Proactive Odor Management.The Evolution ofOdor Control Strategies at the Hamilton,Ohio Wastewater
Treatment and Sludge Composting Facility. Biofilter details and data presented at the BioCycle National Conference, St.
Louis. Mo. May 1994.
Williams, T.O. & F.C. Miller. “Odor Control Using Biofilters”. BioCycle. Vol. 33, No.10. pp 72-76. October 1992
Amirhon. P.& G.A. Kuter. Performance Evaluation
ofBioflter at Dartmouth, MA, Biosolids Composting Facility. Presented
at the New England Water Environment Association Annual Meeting, Boston, MA. February 1994.
Goldsttjn. N . “Odor Control Experiences:Lessons From the Biofilter”. BioCycle, Vol. 37, No.4. April 1996.
Massachusetts Departmentof Environmental Protection, Guidance and Policy for the Evaluation
of Odors at Composting
Facilities.Boston.1996.
AIR EMISSIONS TESTING and ODOR MODELINGat the REVITALIZED
REGIONAL COMPOST FACILITYin HICKORY, NORTH CAROLINA
Graham Gilley
Sludge Consortium
City of Hickory, North Carolina
Todd Williams
Cary, North Carolina
Tim Muirhead
Professional Services Group, Inc.
Knoxville, Tennessee
INTRODUCTION
Full in-vessel capacity operation the
of revitalized Regional Compost Facility (RCF) in Hickory,
North
Carolina was initiated on January 4, 1995. Professional Services Group Inc.
(PSG) was contracted bythe
ownership ofthe RCF, to provide operations, maintenance, and management
(OM&M) services via a
multi-year agreement. The ownership is a Sludge Consortium, comprised of four local governments
Cities of Hickory, Newton, and Conover and Catawba County. The odor problems and revitalization
program for this 20 DTPD in-vessel biosolids compost facility have been well documented
in the past
couple of years. In response
to continued concernsby nearby residents and businesses
of adverse health
and environmental impacts fiom any odorous emissions being emitted the
fiomRCF, the Consortium and
PSG elected to perform a comprehensive
air emissions testing and odor monitoring program during
the
first year of operations. E&A Environmental Consultants, Inc.was commissionedto perform the
sampling and testing program
to address the concerns ofair emissions, odors, and any public health and
environmental impacts attributable to
the operations ofthe RCF.
BACKGROUND
The $7.7 million RCF usingthe Ashbrook-Simon-Hartley (A-S-H) Tunnel Reactor technology
was
voluntarily shutdown bythe Consortium in February,1991 due to chronic odor problems and persistent
1992 the Consortium selectedPSG to
complaintsby nearby residents and businesses. In December,
implement a comprehensive odor mitigation and control program, which would
Mly address all odorous
emissions fiomthe RCF. A major component tothis program was the implementation of $1.5 million
odor control facilities additions and modifications, substantially funded
by a U.S. EPA Innovative/
Alternative (VA) Technology Replacement Grant. PSGwas awarded in April,1994 the notice to proceed
as the first tier subcontractor to manage the construction ofthe additions and modifications
to the odor
control facilities.The project was completed by December,1994 and the RCF was started-up on January
4,1995 and placed immediately into111 facility operating capacity. Since start-up, more than
4,500 dry
tons of biosolids have been
successllly processed into "Exceptional Quality" compost with a high
very
reliability in facility operations, process performance, and odor control and reduction. Many
the of
odor
to control and
control system improvementsin Hickory were based upon PSG's comprehensive approach
eliminate odorskom point-source, hgitive and area emissionsat the in-vessel biosolids composting
facility in Schenectady, New York.
The technical highlights the
of Odor Control Facilities Additions and Modifications Project included
the foll0-g:
0
0
0
0
0
Rehrbished andrelocated the 9,500 c h chemical scrubbing system fiom the
dewatering and compost buildingto replace the 4,000 c h chemical scrubbing
system at the biosolids receiving station and pretreatment plant.
Retrofitted the existing 9,500 c h scrubbing system with high treatment efficiency
nozzles, installed W e plates for
packing media, upgraded spray piping and
addition of mist elimination packing media in top cone
sections and installed
improved on-line instrumentation for process monitoring and chemical feed control.
Optimized biosolids and composting unit processesto mitigate odors with an
emphasis placedon biosolids quality and dewatering, amendment recipe type and
metering, in-feed compost mixture and moisture, and in-vessel Tunnel Reactor
aeration and retention time.
Upgraded the 5,200 c h process air exhaust duct with a 72,000 c h fiesh air
air handlinglodor
ventilation supply and foul air exhaust system. Installed new
exhausting system for the dewatering and composting building, which included
high intensity capture hoods, fiesh air ventilation screens
bird and push fans, foul
air ducts with multipldtapered exhaust ports and dampers, and induced draft fans.
Installed two parallel trains of 36,000 c h three-stage packed-bed wet chemical
scrubbers with a combined treated discharge
of 72,000 c h from a 50-foot tall
exhaust stack. The packed-bed scrubbers were configured in a close-coupled
arrangment to achieve the highest level
of treatment and space efficiency.A new
odor control building was constructedto house the scrubbing trains,as well as the
MCC, PLC/annuciator panel, chemical metering pumps and laboratory bench areas.
PSG’s OM&M contract with the Consortium required that the odor control system
be capable of
capturing the odors produced fiomthe various processes withinthe RCF and provide 99% concentration
removal of the various odorous compounds.A daily and monthlyodor control monitoring and testing
program has been implementedto monitor and document contract compliance.
As graphically illustrated
in Figure1, these levels of scrubbing treatment have
been readily and continuously achieved for both
high
intensity nitrogen compounds (ammonia and amines),we11
as as very pervasivesulfur compounds
(dimethyl sulfide, dimethyl disulfide, and mercaptans). Prior to start-up and during shakedown and
acceptance testing ofthe odor control facilities additions and modifications,
the Consortium and PSG
initiated and implemented a public relations and outreach program the
with
various concerned residents
and businesses which surround
the RCF.
by the Consortium and PSG for
the
Several informational meetings and progress reports were provided
general public duringthe first few months of operation of the RCF. Based upon
the feedback fiom the
community, the majority the
of previously offendednearby residents and businesses had not detected any
odors fiom the RCF and were fully satisfied with
the improvements made atthe facility. However, the
high level of odor control
and treatment performance of the
new facilities did not alleviate
the concerns
been the most vocal aboutthe RCF.
and complaintsby a small group of individuals, who had historically
The proactiveand sincere communication concerningthe OM&M activities andodor control system
performance at the RCF becamethe basis for these individuals to elevate their concerns and complaints of
the facility fiom an issue of odors
to adverse health effects and environmental impacts. Accordingly, PSG
and the Consortium electedto respond to the persistent and heightened concerns
of these small group of
residents by hiring E&A to perform a comprehensiveair emissions study of
odors and regulated toxicair
pollutants to assessthe potential impact of the RCF
on nearby receptors and surrounding environment.
Figure 1
Odor Scrubbing System Performance
CONC. (ppm)
. .. .. .. .. . .
100
-
.
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ................._................ .................. .. .. ...... ... ... ... ... .. .
.. .....
. . . . . . . . .. .. . . .. .. .. .. .. .. .. .. .. .. .. . ..... .
. .. . ... _ _ . _ , ._
.....
..
. .....
. .... .
...
.
.. ..
..
..
10
...
. ..
.. ..
1
0.1
0.01
NRH- NR
3 H- S2H
H2S
OUTLET
DMS
CL2
H20
0INLET 69DESIGN
EMISSIONS STUDY
The Study focusedon the remaining sourceof emissions fiom the RCF, which werethe stack exhausts
fiom the two odor scrubbing systems. These point-source emissions represented a combined atmospheric
discharge of 81,500 c h . All other historical fugitive release
of emissions fiomthe processes and
buildings atthe RCF wereeliminated by the new fiesh air ventilation and foul
air capture system.
Additionally, areas emissions sources at the RCF did not exist the
since
compost discharged fiomthe
Tunnel Reactors were being directly loaded
into trucks and hauledto off-site agricultural sites for curing
and application. The quantityof compost on the on-site curing padwas minimal or non-existent, and
thus, the scrubber stacks represented the sources
of emissions which could have an off-site impact.
A comprehensive air sampling and testing program
was developed to address the neighborhood
residents expressed concernsof odors and health effects fiom
the residual compounds inthe scrubber
stack exhausts. The program includeda baseline analysis,followed by three scheduled quarterly tests, and
random spot sampling (takenby the neighborhood residents)and testing. Eight different gas sample
locations were includedin the baseline testing andthree of these locations were used
for the quarterly and
random testing programs. The samples were analyzed
for Total ReducedS u l k (TRS) compounds,
Volatile Organic Compounds(VOCs), sulfuric acid(H2S04),and chlorine (CL2 ). Limited odor analysis
was included in the program since the TRS compounds
are good indicator of odors, given their pervasive
and low threshold characteristics. Table1 summarizes the air emissions sampling and testing program.
Table 1. Air Emissions Sampling and Testing Program.
Biosolids Scruber Outlet
Compost Scrubber Inlet
ComDost Scrubber Outlet
Combined Scrubbers Outlet
Property Line Upwind
Property Line Downwind
Neighborhood Downwind
m,VWS, a
z ,Hzs0-4
TRS, vocs
m,VWS, CLz, Hzs0.1
vocs
TRS, vocs
TRS, vocs
m,v o c s
TRS, vocs
CL2, vocs
TRS,vocs
cL2,
TRS, vocs
vocs
CL2, vocs
The purpose of the baseline programwas to quantify the emissions in the scrubber exhausts atthe
property of the RCF and inthe neighborhood community. Samples were collected
during representative
operating conditions with scrubber flow rates field verified
during sampling. A combined samplewas
collected from both scrubber exhausts
as a flow weighted composite in an effort
to represent mixingof the
scrubber exhaust stack emissions in
the atmosphere prior to any off-site impact. A sample
was also taken
in the neighborhood to determine baseline information for comparison with
hture sampling and testing
events. Three quarterly sampling events were performed over
the next nine months as follow-up to the
baseline analysis, in an effort
to gather ambient emissionsdata during varying weatherand climatic
conditions.
As shown in Figure2, two of the samples were takenthe RCF propertyline and one sample
was
gathered at a downwind neighborhood location.
The random testing usinggrab sample cannisters
allowed for either the plant personnel or one
of the concerned residents inthe neighborhood to obtain an
ambient air sample for emissions testing. The Study allowed six
forspot sampling events, with
three of
the cannisters given to neighborhood residents, after
training was provided by W. These cannisters
allowed forthe immediate samplingby the residents when they perceived an odorharmll
or
emission
from the RCF in their neighborhood. These random samples were analyzed for
the regulated VOCs and
by plant personnel using a pump and color detection tubes.
chlorine gas measurements were also made
Gas samples were collected in tedlar bags and shipped
to a certified laboratory for performing detailed
s u l k compound analysis using gas chromotography/flame photometric detection(GCffPD). Twenty
sui& compounds were analyzed to a detection limit4.0ofparts per billionby volume (ppb/v). VOC
samples were collected in summa cannisters and shipped to a certified laboratory for
analysis
by gas
used the EPA
chromatography/mass spectrometry( G C M S ) . The analyses performed for these samples
Method TO-14 for 43 specific compounds which
are common VOCs, 30 of whichare regulated CleanAir
Act compounds. In addition to these 43 compounds,15 other tentatively top remaining compounds were
also identified withthe detection limitsof these VOCs in the range of 0.2 to 2.0 ppb/v. Given the
concerns of the neighborhood residents of
the chemicals usedin the scrubbing process being emitted
in
the exhaust stacks,the Study included gas detection tube analysis for
sulkic acid and chlorine. Table2
summarizes the analyses and testing approach performed the
for Air Emissions Study.
BASELINE TESTING RESULTS
Air samples were collectedon March 30,1995 during normal daytime facility operations with
the
weather during sampling being mild
in temperature, mostly sunny and a gentle prevailing breeze. Very
streams. These odors were not
faint chemical-type odors were detectable in both scrubber system exhaust
objectionable or pervasive.No facility odors were noticeable onthe plant site and atthe property line
locations or in the neighborhood.
&"""
D
Q
The emissions samples collected the
in tedlar bags and analyzed for
the 20 Total ReducedSulfur (TRS)
compouids showed that onlysix compounds were detected
in any of the samples, as listed below.
Hydrogen sulfide was only detected the
in headworks scrubber and both scrubber systems had very low
inlet concentrations ofTRS compounds. Both scrubber systems showed outlet concentrations belowthe
detection thresholdsfor the sulfur based analytes, resultingin a removal efficiency >99% for these
odorous and very pervasive compounds.This performance ofthe scrubber systems were also verified
by
snif3ng the outlet emissions fromthe exhaust stacksfiom inspection portsduring gas sampling.
Hydrogen Sulfide
Carbonyl
Sulfide
Dimethyl
Sulfide
Methyl Mercaptan
Carbon Disulfide
Dimethyl Disulfide
All ambient samples for
TRS resulted in concentrations below detectionlimits and sulfur based odors
were not detected atthe upwind, downwind,or neighborhood locations atthe time of sampling. The TRS
concentrations measured in all samples were at least one order of magnitude below any regulatory limit.
Based upon these results,the baseline testing showed that emissions from
the RCF did not contain TRS
concentration levels and thus, caused
no off-site odorsor health and environmental impacts.
The baseline testingof summacannister samples for VOCs showed
that only 16 ofthe 43 possible
compounds via the EPA TO-14 protocol were detected in
any sample. Five of these 16 were detected
in
thqupwind or background location, and thus, indicative oftheir presence in ambient conditions. These
five hazardous chemicals, four
of which are listed as an air toxic by the North Carolina Department
of
Environmental Health and Natural Resources (NC DEHNR) were detected
the at
same concentration at
both the downwind propertyline and neighborhood locations. These compound measurements, while not
high enough in concentration to pose any health threat or adverse impact
to the environment, do indicate
they exist inthe ambient air and thatthe RCF hadno impact on their ubiqituous
nature in the local area.
The concentrations ofthe top 15 tentively identifiedVOC compounds were estimated for
all samples.
As shown in Figure3, cumulative VOC emissions fromthe RCF were several orders of magnitude below
the regulated limitsby North CarolinaOSHA, United StatesOSHA, and NOSH for worker and public
exposure. Using 8-hour continuous exposure limits,
the VOC emissions fromthe RCF included only 11
identifiableVOC compounds fromthe regulated lists, withthe measured concentrations at
the outlet of
both scrubber system exhausts
between two and five ordersof magnitude lessthan the lowest allowable
threeof
regulatory agencies.
exposure limits and recommended concentration levels specified for any
In addition to recommended exposure limits, all 11 compounds identified were compared against
NC
DEHNR’s emission rate limits for each specific compound.This regulation governsthe emissions control
of all 105 air toxic compounds
in North Carolina. Emissionsrates for all 11 compounds identifiedin the
scrubber exhausts atthe RCF were anorder of magnitude below
the allowable emissionrate limits. If any
particular compound exceeded
the regulatory limitwould require an air toxic emission permit with
NC
DEHNR. The cumulative mass emission
rates of air toxic compounds fromthe RCF was determined to be
18 1 lb/yr,
as compared tothe NC DEHNR emission rate limit of 6,795 lb/yr for
the corresponding
compounds. Thus, the results of the VOC analyses clearly showedthat no air toxic or other regulated
hazardous compound were present m
in c i e n t concentrationsin either the RCF scrubbersystems inlet or
outlet exhausts to cause any health or environmental concerns.
Figure 3
VOCs Testing Program Results
1.000E+ 07
1000000
100000
10000
1000
100
'_j
10
RCF
NC
OSHA
US OSHA
NIOSH
I H O d o r Scrubbers I
Sulfuric acid and chlorine were also analyzed
in the exhaust gas of both scrubber systems as
the last
cpmponent ofthe baseline testing program.The gas detectiontubes have a limitsof 245 ppb/v for sulfuric
acid and20 ppb/v for chlorine. As expected, sulfuric acidwas not detected inthe scrubber exhausts, since
this solubility of this chemical causes itto remain inthe recirculating scrubbing solution and does not
allow transfer intothe vapor phaseas a component ofthe exhaust emission. However, chlorine canbe
liberated fiom scrubbing solutions
into the exhaust andbe discharged as an offensive andharmll
emission ifthe odor treatment devicesare not properly operated and controlled. Only a trace
( a 0 ppb/v)
of chlorine were measured inthe scrubber exhausts atthe RCF. At the levels measured,the chlorine
emission rate was significantlybelow the NC DEHNR limit's for permissible exposure levels of toxic
air
pollutants, and thus,the scrubbing chemicals atthe RCF did not contributeto adverse off-site health and
enviromental impacts. Table3 summarizes the air emissions resultsof the baseline testing program.
Table 3. Air Emissions Baseline Testing Program Results.
~
SAMPLE
LOCATIONS
Biosolids Scrubbers
Compost Scrubbers
Combined Scrubbers
Property Line Upwind
Property Line Dowwind
Neighborhood
m.
vocs
(ppbh)
(ppbhr)
ND
ND
ND
ND
ND
ND
275
517
489
8
8
7
.
:..
crr,
ND
GO
4 8
ND
ND
ND
.
H2W
(ppb/v) (wpblv)
ND
ND
ND
ND
ND
ND
QUARTERLY TESTING RESULTS
Three follow-up sampling events were performed
at the RCF to supplement the baseline air emissions
three month intervals to analyze
for
sampling and testing. The samples were collected in approximate
VOCs and TRS compounds during representative seasonal weather periods. Per
the original sampling
plan, 3 samples were collectedat the property line upwind and downwind,as well as downwind inthe
at RCF and the
neighborhood. Sampling was performed during normal day time operating conditionsthe
fiom previous sampling events to account for
the wind direction
exact sampling locations were adjusted
on the day of sampling. All samples were collected
in duplicate to ensure a complete ofsettesting results.
F
I
For all threeof the follow-up sampling events, none the
of 20 Total ReducedSulfur (TRS) compounds
were detected in any of
the 3 samples. These results were consistent with
the baseline testing program
sulfiu compounds were being emitted off-site
from the RCF. The quarterly
and indicate that no odorous
emissions testings forVOCs showed consistent results amongstthe sampling events and locations. Table
4 summarizes the number of VOCs identified andthe cumulative concentration of these compounds.
A detailed breakdown ofthe identified VOCs showed
that 14 of the 17 compounds detected were
present at similar concentrations in all
three sample locations for allthree quarterly emissions tests,
No VOCs were detectedin downwind atthe property
indicating their ubiqituous nature during sampling.
line or in the neighborhood, which did not also exist at a comparable concentration
the upwind
in
sample
at the RCF property line. Thus,the VOCs detected atthe 3 sample locationsfor each quarterly test were
reflective of their continued and consistent presence the
in ambient backgrounddue to the environs near
the RCF. The concentrationsof all VOC’s identified in any sample were compared against
the three
rigulatory limits for permissible worker exposure and public health levels. Once again,ofall
the
detectable compounds were present in concentrations
4 to 6 orders of magnitude belowthe most stringent
recommended exposure limit or specified air toxic level, and thus,
the quarterly testingof RCF emissions
showed nohealth threator environmental impact forthe levels of TRS compounds and VOCs measured.
RANDOM ‘SPOT’ TESTING RESULTS
The Air Emissions Study made provisions for upsixtorandom ‘spot’ sampling and testing
by either
PSG plant staff andor the concerned neighborhood residents. Several of the ‘spot’ samples were
conducted during early morning hours
in attempts to gather samplesduring the worst case time periods,
which occur at sunrise. This time of day would have
the greatest possible accumulation of emissions fiom
the RCF dueto the early morning temperature inversion, which was often present
in the Hickory area.
Other spot samples were performed
during normal night-time hours when typical operations
theatRCF
occurred, in order to evaluate emissions during typical evening, weekend and holiday periods when
PSG
personnel are not normally present atthe plant. The neighborhood residents were concerned that
the unit
operations and especiallythe odor scrubber systems were loosing control and causing
the odors duringthe
unstaffed periods atthe RCF. It was explained to them atthe public meetings about
the automated
operations atthe RCF with PLC control of
the odor scrubber systems, all
of which contain alarm
annuciating and telemetry features
to ensure thatwas not the case. However, the Emissions Study
included the random ‘spot’ sampling by the neighborhood residentsto address their specific concerns.
Given the simplicity of gas sample collection with
the Summa cannisters, itwas agreed that VOCs and
the 15 of the most prominent and tentatively identified compounds would
be analyzed so that any
measurable compounds could
be compared with federal and
state regulatory exposure levels and
air toxic
emissions limits. When a sample
was taken, the cannisters were picked
up by PSG personnel, sampling
event data recorded and then shipped fiom
the RCF to the testing laboratory under a chain-of-custody.
Chlorine gas was also analyzed
by the PSG personnel using a hand held
gas pump and colorimetric tube
when contactedby the neighborhood residents concerning a random ‘spot’ sampling event. Fourtheof
available six cannisters were usedby the neighborhood residents at times when
they perceived odors fiom
the RCF to be most noticeable and pervasive.The samples were collected fiom
April through July of
1995, encompassing different weather conditions still
of wind, temperature inversions, light haze, heavy
fog, sunny and very humid conditions. Table5 summarizes the four random “spot” testing results.
Table 5. Air Emissions Random ‘Spot’ Testing Program Results.
EMISSIONS
PARAMETERS
vocs, ppbh
Other, uG/m3
NEIGHBORHOOD SAMPLES
(4128/95) (616195)..(7f7/%)
25.1
13.0
20.8
68
80
177
.’,
(4!2/95)
10.6
40
REGULATORY L
E
Y
E
L
L
/
s
m
NIOSE
5.7~10~ 5.6~10~ 3.4~10~
1 0 . 8 ~ 1 0 ~ --------10.2~10~
NC OSHA US OSHA
EMISSIONS MODELING
The Air Emissions Study comprehensively and definitively demonstrated the
thatRCF did not
contribute to any adverse off-site health and environmental impacts based the
upon
testing analyses
performed. Despite these very favorable results,
the neighborhood residents shifted their continued
concerns fiom health and environmental impact issues back
to odors. Despite notidentiwg any of the
odorous and pervasive reduced sulfur compounds off-site
in various gas samples collected during
the Air
Emissions Study,the Consortium electedto perform a comprehensive odor modeling evaluation to assess
fiom the two scrubber systems.
the level of off-site impact fiom
the low, but quantifiable stack emissions
The primary purpose
of the emissions modeling workwas to predict levels and/or periods
of off-siteodor
detectability andthe associated impact reductions for various compost system exhaust stack modifications.
.
Air samples were collected fiom both scrubber stack exhausts
at the RCF on June 7, 1995 during
normal operating conditions,as well as upwind and downwindareas during the early morning and/or
evening periods when odor occurrences were perceivedthe
byneighborhood residents as being most
prevalent. Weather duringthe gas sampling effortwas good, with partly cloudy conditions and a steady
westerly breeze withan average temperatureof 75 deg. F, which were very similar atmospheric conditions
as the baseline emissions study sampling. Duplicate
air samples were collected in conditioned tedlar bags
and shipped overnight to another commercial laboratory using standard chain-of-custody procedures.
The samples were analyzed for odor using a trained
and screened odor panelby dynamic-dilution
olfactometry. The odor results were quantified in both terms of dilution-to-threshold @/T) ratio in
accordance withASTM Method E679-91 and intensityin accordance withASTM Method E544-75.
The emissions modeling utilized both aspects of odor analysis and perception; detectability and intensity.
Odor detectability is quantified by
the DIT ratio in whichthe detection thresholdis expressed as the
number of volumes of odor-pee air required to reduce
one volumeof the odorousgas to the median
detection threshold. Typically the D/T ratio is defined atthe ED50 detection threshold, where50 percent
of the trained panelists can
sniff test different dilutions of sample
air with non-odorous air and correctly
distinguish the odorous air stream fiom the non-odorous sample. Odor intensityis typically quantifiedby
a rangeof sample dilutions sniffed
by the panel of trained odor technicians to standard dilutions
of stable
gas, n-butanol. For specified rangesof n-butanol concentrations, a corresponding scale, which is ranged
fiom 1 to 8, defines the level of odor intensity. Both odor detectability and intensity measurements were
performed inthe Air Emission Study to model any off-site impacts
at the nearest receptors.
ODOR MONITORING RESULTS
Table 6summarizes the odor sampling results used in
the emissions dispersion model to fiuther
assess
off-site intensity and detectability.
As shown, both scrubber systems had equivalent inlet odor concen23 to 81 D/T. The propertyline upwind
trations of 196 DIT with outlet concentrations which ranged fiom
and the neighborhood downwind had odor concentrations ofand
6 5 DIT, respectively. The odor panelists
reported significantly different sources
of odors for thesetwo samples as compared to boththe scrubber
inlet and outlet samples. While performing
the on-site and off-site odor sampling,
E&A staff confirmed
that no RCF odors were detected, which supports
the analysis of the odor panelists. Furthermore, the
upwind and downwindodor sample results indicate that a detectable level
of odor is prevalent inthe local
of any odor impact fiomthe RCF.
environment and neighborhood, independent
Table 6. Odor Detectability Results.
SAMPLE
LOCATIONS
ScrubbersInlet
Scrubbers Outlet
Property LineUpwind
Neighborhood Downwind
BIOSOLIDS SYSTEM
(am,)
(p-m;)
23
25
COMPOST SYSTEM
(am-) (p.nt)
81
55
ODORCONC. @rr)
(avg.)
(model)
196 196 196
67*
99*
1
6
4
5
* flow-weighted average.
The inlet odor concentrations were identified to be equivalent for
the biosolids and compost scrubbing
systems. Despite this coincidence, the compost scrubber system inlet
was well below those reported values
for other in-vessel biosolids composting facilities.The industry has reported odor inlet concentrations
as
high as 1,200 D/T. The lower inlet odor concentrations at theRCF is the result of the high level of
success of in-vessel process control and odor
mitigation of the composting process. The outlet
concentrations of both scrubber systems are reflective of high odor treatment performance when compared
to other chemical wet scrubbing levels reported at other in-vessel biosolids composting facilities.
The results of the odor monitoring effort were used as inputs for the dispersion and off-site impact
modeling. A conservancy was built in forthe purpose of the dispersion model in that
the outlet odor
was assumed to be 100 D/T and for the biosolids
Concentrations for the compost scrubber system exhaust
scrubber exhaust was assumed to be30 DIT. These model inputs provided a level of conservancy when
the assessmentwas performed and represented worst case exhaust conditions for scrubber operations.
98% of the stacks’ emissions,the flow-weighted odor
Since the compost odor scrubber system represents
outlet concentrationfrom the RCF during the odor sampling effortsas shown in Table 6 was 67 D/T. The
equivalent flow-weighted outlet odor concentration for
RCF stacks’ emissions in the model
was 99 D/T.
The dispersion model also used more rigorous property line upwind and neighborhood downwind odor
concentrations. An odor concentration of1.O D/T is a level in which odors can be detected but not
specifically identified as to their source and
type. Typically odor concentrations below1 D/T are not
detectable by most individuals. Similarly, odor concentrations above4 D/T is often definedas a nuisance
threshold, where they are distinctly detectable and even recognizable with an intensity which
be may
regarded as offensive by a receptor. Odor Concentration thresholds at compost facility property lines
are
being limitedby state regulatory agencies at levels between
5 and 10 DIT to prevent off-site nuisances.
was related to odor intensity inthe model to
Odor detectability using the threshold @IT) value
evaluate the sensitivity to nearby receptors using a dose-response formula and the n-butanol scale. While
there is no nationally
or North Carolina standards which define acceptable ambient odor levels,
the
research and experience in the composting industry has shown that n-butanol ratings 3above
will have an
odor impact with an intensity that will be perceived
as a nuisance. Thus, E&A determined fiom the odor
sampling and testing results the calculated n-butanol equivalents which defined the specific odor
concentration @/T) in the Hickory area that may lead to a nuisance level at the nearest receptors.
As shown in Table7, the nearby off-site receptors (neighborhood downwind location) nuisance odor
threshold was defined as less than 4 DIT. This off-site receptor nuisance threshold
is lower than any
existing regulatory odor standards for on-site levels
at facility property lines,as well as lower thanthe
levels measured inthe ambient air inthe Hickory area. Additionally, the Air Emissions Study defined the
ambient airodor level of 1 Dm, which is lower than the measured upwind and downwind ambientodor
concentrations Of 4 and 5 D/T. The contribution of these background
odors, produced by other human
activities and environmental sources the
in area aroundthe RCF,were not considered in the modeling
analysis to evaluate nuisance conditions.Thus, a very rigorousodor impact levelwas used inthe
dispersion model to assess any off-site impacts contributed by the scrubber emissions
fiom the RCF.
Table 7. Odor Intensity Results.
,
n-BUTANOL
MTENSITY SCALE
BIOSOLlDS SCRu3BBERs
@/T)EQUIVALENT
1
COMPOST SCRUBBERS
@/T) EQUIVALENT
1
1
2
2
4
6
4
6
8
11
13
9
12
16
ODOR DISPERSION MODEL
Several different emissions dispersion models were evaluated to identify
the most applicable format
and the Industrial Source Complex Short Term (ISCST2) model
was selected. This is a refined model
that employs historical weather data and can evaluate numerous emissions sources and receptors simultaneously. U.S. EPA recommends this model for evaluating simple and intermediate terrain using site
specific source and receptor parameters and meteorological data. Discrete receptors
can be evaluated, as
well as odor concentrations in defined grid
areas. The refined model estimatesthe odor concentration at
data and produces summaries of
the highest concentrations
each receptor for each hour of meteorological
recorded at each receptor and the fiequency of occurrence of concentrations higher
than the model defined
odor nuisance threshold. Frequency of occurrences
can be narrowed to 30-secmd peak timeperiods.
The model incorporated five yearsthe
of most recent meteorological data
&om the Hickory Regional
Airport and digitized terrain data aroundthe RCF using topograhic maps of Catawba County. These
maps provided the coordinates and elevations
of all sources, terrain, and receptors inthe area using the
North Carolina coordinate system.A grid of 589 receptors points were identified within 50
a meter (1.1
mile) radiusof the RCF andthe 3 nearest and most sensitive receptors were discretely analyzed within
the
model. Figure 4 shows an area map aroundthe RCF in Kickory, with identifications ofthe scrubber
exhaust stacks and the 3 nearest and sensitive receptors.
As seen in Figure 4, terrain features below900
feet in elevationare not shown because they did not impact
the modeling analysis.
The primary odor inputs
to the model werethe RCF scrubber systems' exhaust stacks emissions, with a
defined odor output threshold atthe nearest receptors ofless than 4 D/T. The dispersion model employed
5 scenarios, including existing conditions and
4 combinations of increased compost scrubber system
exhaust stack height and emissions velocity, to consider commonly used source emission strategies to
reduce anyodor impacts atthe near receptors. The compost scrubber system stack emissions were
the
focus ofthe modeling scenarios since was
it determined that this point-source accountedfor 93% of the
discharged air flow and98% of the discharged residual odors fiomthe RCF. The 4 additional modeling
scenarios included increased exhaust velocity
to optimal dispersion conditionsfor existing stack height
and two increased stack heights, as well
as existing exhaust velocity an
at increased stack height. The
increased exhaust velocity scenarios used ambient
air &om a dilutionfan installed at the base ofthe stack.
ODOR MODELING RESULTS
The resultsof the ISCST2 dispersion model indicatedthat nuisance odor conditions (> 4 DD') would
occur very infiequently for the existing hcilities. In addition,the model results showed that
the most
odor impacts couldbe achieved by increasingthe stack exit velocity, with benefits
significant reduction in
also achieved&om an increase in stack height. In order to assess the degree ofodor impacts on the
nearest and most sensitive receptors for each model scenario, a tabulation
was compiled of the highest
odor concentrations projectedduring a thirty second (30-sec) peak occurrence,
as summarized in Table 8.
0
0
0
0
v)
n
..
n
L
0
0
Q\
.._.. ..
0
m
c
0
'.. ...
............
!
i
t
I
0
C
o
\
...........
.
0
w
v)
.
...........
........
...........
- -.
0
SUMMARY and CONCLUSIONS
An air emissions study, which spanned
9 months in 1995, was performed duringthe fist year of
operation of the revitalized Regional Compost Facility
in Hickory, NC. A comprehensiveair emissions
sampling and testing program was implemented
to evaluate the performance ofthe odor control systems
and address public concerns
of off-site healthand environmental impacts. All emissions were compared
to concentration thresholds and exposure levels of numerous compounds
as regulated by 3 governmental
(federal and state) agencies. Additional scrubber stack emissions
and ambient air sampling and testing
were performed for odors asinputs into a dispersion modelto assess off-site nuisance impacts, both locally
and at discrete sensitive receptors. Five different scenarios were evaluated
by the model with use of
conservative assumptions andthe utilization of stringent impact criteria at receptors. Accordingly,
the
following conclusions were developed
as a resultof the Air Emissions Study:
The Regional Compost Facility
has minimal or no off-site health and environmental
sulfur
impact fiom its scrubber systems’ emissions as analyzed for total reduced
(TRS) compounds, volatile organic compounds (VOC), sulfuric acid, and chlorine.
TRS and VOC emissions inthe scrubber systems’ exhausts were significantly below
regulated concentration levelsby U.S. and NC OHSA and NIOSH and air toxic
emission limitsby NC DEHNR.
Both the biosolids and compost scrubber systems performed excellent for removing
TRS compounds and emitted acceptably low levels
of residual odor when compared
to compost industry experience for odor treatment using wet chemical scrubbing.
Only trace levelsof total residual chlorine (TRC) were detected
in the compost
scrubber exhaust and well below regulatory limits.Chlorine odors were not
detected off-site and had no impact on health or environmental concerns.
Other chemicals used inthe scrubbing process, i.e. sulfuric acid were not detectable
in the stack exhausts and thus, did not contribute to any perceived or
odors
impacts.
The existing facilities and operations the
at RCF resultedin infrequent or nonexistent levels of odor detection, both on-site and off-site
during emissions testing.
The dispersion model predicts that for existing facilities and operating conditions,
nuisance odorthresholds occur infrequently at the nearest three sensitive receptors.
Peak nuisance odors atthe nearest three sensitive receptors could
be eliminated by
increasing the compost scrubber system exhaust stack 25
byfeet and increasing its
emissions discharge velocityto the optimal point-source dispersion level. This
scenariowould also reduce detectable or perceived odor at nearest receptors
by 50%.
The implementation of this comprehensive air testing, emissions analysis, and odor modeling
theat
RCF in Hickory, NC demonstrated that
the sensitivity of the nearby residents is such that no matter how
favorable the results, their detection of nuisance odors and perceptions of adverse healttdenvironmental
impacts may still exist.Thus,the potential still exists for concern bythe Consortium andPSG of any
periodic off-site detectability of odorous emissions which may
be perceived as originating from the RCF.
However, the Air Emissions Study results and E&A’s independent assessment support
the reality of the
highly productivepublidprivate partnership which existsbetween the Consortium andPSG. The very
successful level of operations and odor control since start-up,
a&ms the revitalization of the RCF. Its
performance, reliability, and beneficial use for biosolids managementthe
forConsortium communities,
reflects a positive outlook
on the h t u r e of “Composting inthe Carolinas”.
CHANGES IN THE NORTH CAROLINA
COMPOST RULES
Ted Lyon
N.C. Departmentof Environment, Health and Natural Resoutces
Division of Waste Management
Solid waste compost ruleswent into effect in North Carolina in 1991. Two separate sets of rules were put into
effect. One set of rules dealt only with requirementsfor yard waste composting. Yard waste rules included yard
waste and other untreated and unpainted
wood wastes. Some agricultural wastes could be composted at a yard
waste facility. The other set of rules dealt with composting municipalsolid waste. The municipal solid waste
compost rules were written primarily for mixed waste composting. Most s o u ~ c eseparated organics, suchas
mixed paper, were excluded from yard waste facilities and
as a result had to be regulated as mixed waste.
One Sectionof North Carolina municipal solid waste rules
addresses pilot or demonstrationcompost projects.
The intent of this Section was to evaluate the feasibility
of a proposed compostproject. However, we began to use
it as a way of working with individualswho wanted to compost certain source separatedmaterials. Facilities that
composted such materialswould not be expected to pose the same level of health or environmental concernsas
those composting mixed waste.
Some of the materials that have been composted in demonstration projects include various
food processing
wastes, restaurant wastes, tobacco and cotton processing wastes, hatchery waste and mixed paper. Compostinghas
been accomplished using windrows, aerated staticpiles, bins, and rotating drums.
Two points becameobvious while working with the various demonstration projects.1) The existingrules were
not user friendly to composting source separated organics.2) There was little interest in projects to compost
mixed waste.
As a result the compost rules were rewritten effective June 1996. Yard waste ruleswere combined into one
set of rules with the municipal solid wasterules. Application, siting, operation and testing requirements were all
based on the types of material to be composted and the sizeof the facility.
Four facility types and two facility sizeswere established. Type one facilitiesmay only receive yard waste and
untreated and unpaintedwood waste. Type two facilities may receive wastes such as s o u ~ c eseparated paper, meat
free food processing wastes, vegetative agriculturalwastes or otherwastes that arenot expected to contain
sigruficant amountsof pathogens or other contaminants. Materials expectedto contain pathogenswould have to be
composted ata Type three facility. Typefour facilities would be those receivingmixed waste, cocomposting with
sludges, or receiving wastes anticipatedto contain contaminants. Facilitysizes were separated at 6,000 cubic
yards
per quarter for Type one facilities and 1,000
cubic yards per quarter for other facilities.
Pads are no longer requiredfor Types one, two, and three facilities where soil conditions are adequate. Testing
requirements atType two and three facilities were reduced since the potential for contaminants is less
than with
mixed waste. Engineer stamped plans arenow only required forType four and large Typethree facilities.
The Division of Waste Managementhas been pleased withthe success of our demonstration program and will
continue to approve projects underthe demonstration guidelines. Manyof the existing demonstration projects that
we have been renewing annuallywill be converted to permits.
Case Study: The N. C. Zoo MSW Pilot Composting Project
Dr. Bob Rubin, NCSU, Biological & Agricultural Engineering
and
Brooks Mullane, N. C. Zoo Horticulture Dept.
HISTORY and BACKGROUND
The North Carolina Zoo first opened as an Interim Zoo in 1974. The first permanent exhbit was Forest
Edge (Zebra, Ostrich and Giraffe), which opened in 1979. The R. J. Reynolds Aviary opened in 1982, the African
Pavilion and Plains in 1984, the Stedman Education Center in 1990, the Sonora Desert in 1993, and all the rest of the
North American exhibits opened in 1994195196. The African exhibit area covers about 300 acres and the North
American exhibits cover about 200 acres. In 1994, approximately 934,000 visitors came to the N. C . Zoo, of whch
more than 120,000 were school children. Between 275 and 300 permanent staff, 175 seasonal employees and 200
volunteers work at the Zoo. The Zoo houses approximately 1000-1200 individual animals representing between 250
to 260~pecies.
The Zoo's exhibit philosophy requires extensive use of plant material as part of the naturalistic settings
provided for the animals. In between the exhibit areas, the Horticulture staff strives to preserve the native woods of
the property. Over 90 acres of turf are maintained and we have more than 6 1,000 plants representing 1,500 or more
plant species.
Education of the public to respect the plants and animals, as well as bring meaning to the protection of the
world's ecosystems and biodiversity are key messages the Zoo relates to its visitors. The N. C. Zoo's Composting
Operation is just oneaspect of our overall commitment to conservation.
THE COMPOSTMG OPERATION
The MSW Composting Pilot Project began June 1, 1995. For the decade or so prior to this, elephant and
rhino manures and bedding had been brought to the Horticulture service area and mixed with plant debris. This
material was allowed to sit and age and then was used throughout the non-exhibit landscaped areas of Africa. Upon
implementation of the Pilot Project, a more structured composting system was devised to satisfy the criteria specified
in our permit.
One of our first obstacles was the construction of a solid, but temporary, ramp for the Animal Keepers to
use to be able to dump from their utility vehicles. The Horticulture staff, with the aid of a design by the Zoo's
Architect, built a ramp consisting of 10" x 10" timbers, deadmen, cables and backfilled with red dirt. The placement
of the ramp was particularly important due to the flow of traffic, wet winter conditions and the most effective use of
limited available space. Through several trial-and-error efforts, we have settled on a system of windrow placement
that allows for the best drainage we can have (using a packed dirt surface) and the most efficient windrow turning
capacity to end near our aging pile.
A combination ofregular turning and the use of fly parasitoid wasps, for filth breeding flies, arereleased
every two weeks, March through October. These are purchased from Rincon-Vitova Insectaries, Inc. at a cost of
$30.00 plus shipping for 20,000and are incorporated into the freshest compost windrow. This has significantly
reduced the fly problem around the Greenhouse area. We have very little odor problem unless you happen to be
there when the wind is blowing from the South as the Elephanmino Keepers are delivering a fresh load.
The particle size of our finished compost could definitely be improved. But, since we do not have a tub
grinder. we do a lot of hand screening of product before being used as a soil amendment or conditioner. As seen in
Table I , the nutrient value is not sufficient to be used as a fertilizer. With the vast amount of soil amendments and
conditioners utilized in the Zoo, the compost is very much an asset since it increases the organic matter in our natural
clay soils, improving drainage. It also is used to mix with topsoil for new plantings to increase water holding
capacity of the soil mix.
An excellent example of Zoo compost at work is in the raised beds of the"Browse Garden" or Animal
Enrichment Garden. This garden is used to produce edible plant material for a wide variety of the Zoo's animals as
a means of enhancing their diet or providing a treat to eat or play with on e h b i t or in their holding areas.
Everything grown has been approved by the Zoo's Veterinarian. Some examples are mostall of the normal
Southem-grown vegetables and fruits, including asparagus and strawberries. We also grow banana plants for the
leaves and stalks which are enjoyed by everything from the polar bears to the warthogs. A majority of what is grown
is given to the various primates. But the Lions, Bobcats and Elephants enjoy the cantaloupes, watermelons and
pumpkins. This is a totally organic garden which has been very successful, much owing to the use of compost.
There were some questions about the Zoo staffs concem about using compost, so a questionnaire was sent
out (copy included). There was an overwhelming positive response. Of the 82 Surveys returned, 63 commented
favorably towards Zoo composting, with many stressing that more should be done and some suggesting we sell the
finished product to produce revenue. Another impressive result of the survey was that 42 of the 82 respondents said
they composted at home.
COMPOST QUALITY
Samples of the composted herbivore manures and the herbivore manures co-composted with other
biodegradable wastes have been collected and analyzed. The results of the analysis are summarized in the tables
below. The analysisindicates that these materials contain low levels of essential plant nutrients and very low levels
of the regulated metals. The quality of the manure compost is presented in Table 1. Table 2 presents the quality of
compost produced from the co-composting of feed fish with manure. These feed fish (2.5 Tons) were the result of a
malfunctioning freezer. Rather than transport these fish to the landfill, they were blended with manures to manage
these biodegradable wastes on site rather than tax the local landfill.
This demonstration indicates that the N. C. Zoological Park can manage a variety of organic wastes on site.
The diversion of the feed fish to production of compost suggests that many of the biodegradable wastes generated in
the Zoo can be managed successfully on site and need not be transported to the local landfill.
POTENTIAL AND REAL ECONOMIC SAVINGS
Currently, the N.C. Zoo compost site diverts more than 1100 tons of solid waste per year from thelandfill,
saving more than $44,000a year in hauling/tipping fees. The compost, in turn, is used at the Zoo in place of
purchasing soil supplements at a savings of at least $2,400 per year. Since the permit is fora Pilot/Demonstration
Site, composting is limited to materials specified in the permit. If the site were upgraded to meet the requirements of
a permanent compost facility, approximately 300 additional tons per year could be diverted from the landfill with a
savings of$12000 and the compost could be stockpiled for renovatiodexpansion projects saving $25,000 per year in
purchases of soil supplements. (The soil supplement cost of commercial compost for the North American Exhibits
was more than $125,000, which could have been provided by the Zoo's Compost Facility if it had been upgraded and
permitted.)
The initial Pilot Program Permit has been extended to June 1, 1997. If the upgraded Permanent Site,
estimated to cost around $128,600, is not constructed and permitted by then, the Zoo could be forced to cease the
compost operation and begin paying the $46,400 in hauling fees and soil supplement costs without realizing the
additional savings of$37,000 per year. When considering the option ofeither NO SITE or the Permanent Site, the
savings would be $83,000 and the payback less than two years. If the current permit is extended and the option is
either the current site or the Permanent Site, then the savings would be $37,000 and the payback less than four years.
In either case, the Permanent Site will pay for itself in two to four years.
i6
COMPOST QUALITY
(As Dry Weight)
NORTH CAROLINA ZOOLOGICAL PARK
Results as mgkg unless specified
-
Parameter
Sample 1
Sample 2 w/feed fish
Dry Matter (%)
48.74
55.45
TKN
12031
19105
TP
4830
8208
K
7685
9993
Ca
1 1390
1200 1
Na
230
Zn
47.1
56.9
cu
15.0
22.0
Ni
.66
.85
Cd
.57
.6 1
Pb
.79
1.54
61 15.5 PAN
I
835
9702.5
Coliform (mpdg)
450
790
Salmonella
<1
<1
To convert concentrations to mass per ton, multiply by.0020; to convert to mass/lOO lb, multiply
by .OO 1; for example:
PAN in Sample 2 is calculated as either 19.4 PAN/ton or .97 lb/100 lb.
37
I
1/25/96
To: All NCZP Employees
From: Brooks Mullane, Horticulture
Please take a few minutes to answer the following questions
concerning the use of Zoo compost within the Park. The data
collected should provide information that can be used in
the NCZP Pilot Composting Program to be submitted
to the Carolinas
1996.
Thank you for your
CompostingConferenceinOctober,
cooperation.
1.
a
paper
In what department do you work? (Please check)
Animal
Purchasing
Horticulture
Warehouse
Education
Marketing
Design
Facilities
Society
Human Resources
Management Services
How
long
have
you been
at
your
current
position?
2.
What is your levelof education? (Please check)
HS2 yr degree
BS- Higher-
3.
Did you know
composted
our
Zoo?
at
Yes
No
4.
Do you believe
the
Zoo
should
compost?
Yes
5.
Briefly give your opinion of the use of composted animal
manures within the Park.
6 .
Do you compost at home? Yes
animal
manures
and
horticultural
debris
No
No
were
being
The Reduction of Fish Processing Wastes to
Provide a Marketable Product Through Composting
Lori Cumiff
Fibrestone Technical Affiliates Inc.
Miami, Florida
Joseph M. Edwards
Hoover Aquatic Farms
Balsam Grove, NC
Worhng in and around the troutaquaculture and processing industries, Hoover Aquatic Farms has been able to observe
how mortality and processing by-product has and is being handled. The most common disposal method being utilized is
a landill application. Hoover Aquatic Farms was determined to find a more economical and environmentally hendly
method to handle these wastes. What occurred was the evolution of the waste disposal
process, which finally became a
fully aerated cornposting facility that includeda leachate collection system. This allows for the reduction of the fish
processing waste to a marketable product.
T h s paper presents the historyof the waste disposalprocesses at a fish farmingoperation and the evolution to a fully
aerated composting system. Mortality and processing by-products have traditionally utilized a land fill application for
the most common disposal method.M e r various problems at Hoover Farms with this type of operation, alternatives
were explored. A windrow static pile composting operationwas selected. There were several modifications of this
system'until a fully aerated system with anonpermeable liner was designed. This paper will discuss the various
modlfications and show the final systemin detail.
The trout fish farming operation at HooverAquatic Farms consists of a series of inter-connected pools, known as
raceways. The small f?ye are kept in the uppermost tank, andas they grow, they are let into each successive tank until
they reach maturity in the lower tank.The fish are fed with pellets, whch are disbursed automatically on demand by the
fish &omstorage containers. The rate and the amountof feed can be controlled, and this information is recorded to be
able to check conditions and the health
of the fish. Water supply for theseoperations is from a spring fed stream from
the mountains. The water passes through the farm, and it is returned downstream from
the farm.
Solid processing by-product wastefrom these operations include fishheads, tails, entrails and mortality. Mortalities
(dead fish) arecaught in the screens at the endof the raceway andare placed into thecompost pile close by. These
wastes have very littleodor when they are right off the production line. The odor becomes more pronounced after a day
or two. This gives ample tlme tocombine these wastes with wood chips or other bulking agents and start the
composting process before any odor develops.
Originally, at Hoover Aquatic Farms, solid waste from
h s fish processing was buried on site with a cover of lime and
then backfilled withsoil. This worked for a while untildogs and other animals began to dig up the fish wastes. This
created a breeding groundfor maggots and other insects. The deterioration of the fish waste caused severe odor
problems. Additlonally, these burial pits were located close to the feed water streamfor the farm and could have poseda
potential environmental hazard. Therefore, Hoover Aquatic Farms decided to look atsome waste disposal alternatives.
The first solution consideredwas the local landfill. However, considering the problems that were occurring on site,
Hoover Aquatic Farms determined that this would simply transfer the
problem to another site. A more pro-active
solution wouldbe needed.
It was decided that the best waste disposal alternative would
be composting. This would allow Hoover Aquatic Farms
to take a traditional waste product andturn it into a usable product. Additionally, this composting would hopefully
eliminate the odor and animal problems. Fish processing waste was mixed with a bulkingagent such as sawdust.
Sawdust was an easily accessible waste product in theNorth Carolina area. Aeration and moisture control would be
necessary. Therefore, a trench eight feet wide, one footdeep and 120 feet long was dug with a basin at one end. A
nonpermeable liner was placed into the trench andbasin. The air handling manifolds, which wouldaerate the pile, were
placed In the trench Over the p ~ p eseveral
,
inches of crushed stone was prepared and used as the bed. The waste was
then piled into windrows on top oithls gavel.
This method eventually proved unsatlsfactory. The trench filled
up with water and leachate, andh s prevented the
proper aeration of the pile Water and leachate, which collected in a lined collection pond, resultedin severe odor
problems and caused numerous complaints from other
farms in the vicinity.
The next attempt at aeration had the goal ofmore umformly distnbuting the air. An aeration system usingpipe was
installed prior to pouringa concrete slab. This system, however, did not provide for
the collection of leachate,as it was
originally thought that the accelerated composting would use up all the moisture
in the waste. This attempt alsoproved
unsatisfactory.
Batch cornposting utilizing individual compartmentswas tned next. Piping madold was laid out foreach compartment.
Chips to a depth of approxlmately four inches were alternated with the fish wasteprovide
to
cover and toabsorb
moisture from the freshly placed fishwaste. The initial layer of wood chips at the bottom would also help absorb
moisture and distnbute the air d u n g the early loadingstages. Molsture control duringt h ~ process
s
proved to be the
largest problem.
The w w d door boards of the bins became bowed from the weight
of the compost in the filled unit. This was later
corrected by utilizlng tongue and grooved boards for the design
of the wood doors. Since moisture control was a
problem, I t was decided that rain water mustbe eliminated, Therefore, a roof was added. This helped shield the
compost pile from therain. After about a month , the compost was ready to be unloaded.
Leach& continued to collect at the bottomof the piles. This resulted in leachateseeping out of the bottom of thebins.
This again created anodor problem, and it became apparent thatit would be necessaryto make provisions to collect and
handle the leachate for recyclingor disposal.
The nest modular units were constructed out of concrete block. This helped overcome the rapid deterioration of the
wood caused by the excess moisture. A new product called BioPlate was then installed to assist with leachate collection
and aeration. BioPlate is simplya two foot-by-two foot modular concrete unit which
forms the base for thecomposting
system. It is designed with aeration holes throughout the system.It was also designed to support the weight of a
tractorfloader dnven onto the floor of the bin. See Figure 1 for design details of theBioPlates.
The holes (9mm, approx. 32/plate) allow the leachate to go into the holes and move along
to a collection areaby gravity
feed. Both negative and positive aeration have been found to work well with these
plates based on field applications and
data supplied by Dr. James Shelton of the NC State Agricultural test facilityin Fletcher, NC. Hoover Farms utilized
positlve air flow from beneath the pile because
of existing plant setup. This method of aeration precludes the addition
of
an odor control system if t h ~ should
s
become necessaryin the future without enclosingthe entire composting complex.
At this time, odor associated with the exhaustedair has not been aproblem.
Figure 2 shows the leachate collection system prior to the installation
of the BioPlates. The addition of the BioPlates, as
shown in Figure 3, allows for the collection of the leachate and the acceleratedcomposting due to aeration.
The leachate travels along the impermeable surface down into a collection
tank. Water from this collection tankcan be
recycled back onto the compost pile as moisture is needed. Excess liquid is collected and taken toa sanitary sewer
treatment plant.
The Hoover Farms compost system nowoperates in both an economical and environmental friendly manner andhas
become the permanent waste management tool for their operations. Hoover Farms encourages similar farm operations
to benefit fromcomposting as opposed to landfllling, andrealizes that the successfulcomposting operation resulted
from constantlyseeking better alternatives and utilizing research efforts
of a local University
/
,
BioPlate t9
w
COMPACTED SUB SOIL
~
NOTE: Reinforce concrete slab and
side support with re-bar per local
code requirements
F
FlBRESTONE TECHNICAL AFFILIATES
BioPlate@ Cornposting
Plate
patented
1
II
3
h
3
u
rn
7
m
c
C
0
c,
.+
m
'0
C
M
0
3
C
.-I
57
0
c,
a
E
0
U
CU
0
C
0
Solid Waste Pilot Composting Project: Results and Lessons Learned
The Marine Corps Base, Camp Lejeune Experience
Julie A. Shambaugh
MPrineCorpsBaSe
Camp Lejeune, North Carolina
Penny M~scruo
Parsons Engineering Science, Inc.
Gary, North Cprolina
BACKGROUND
Established in May 1941, MarineCorps Base, Camp Lejeune provides specialized training
to prepare troops
for amphibious and land combat operations. Today, Camp Lejeune occupies 153,000 acres with 14 miles of beach
on the Atlantic Ocean. The Base operates and maintains more than 450 miles of fonds, 50 miles of railroads, seven
wastewater treatmmt plants, five water treatment plants, a municipal solid waste landfill, and 6,800 buildings and
facilities supporting 144,OOO Marines, Sailors, and their families. The Base buses the 2d Marine Division, the
nucleus of the M h Corps East Coast force-in-readiness. Six Marine and two Navy C o d are stationed
aboard @mp Lqeune. Also located within the boundaries of b
m
p Lejeune is the Marine Corps Air Station, New
River.
Camp Lejeune provides for its own solid waste disposal requirements. Approximately 300 tons of solid
waste are generated each work day at Camp Lejeune. Composition of the waste is similar to that of a small city.
The housing area refuse is similar to municipal waste collected from urban residential areas while the waste from
the Base d
u
s
t
r
i
a
l area is similar to the commercial and industrial waste generated inmany cities. The Base
currently operates an unlined d
t
a
r
y landfill. A Resource Conservation and Recovery Act Subtitle D multicelled
lined landfillfacility with leachate cdlection system at a 170-acre site locatedon-Base is expectedto be in operation
by 1 January 1998. This new landfill will result io significant operating costs to Camp Lejeune, making alternate
means of mpnnshq solid wppte o h more cost-effective. In M effort to reduce the volume of solid waste requiring
landfilling and to make optimum use of yard wastes prohibited from landfill disposal, theBase requested approval
from the North C a r o l i n a DivisionofSolid
Waste Management to undertakeayear-longSolid
Waste Pilot
Composting Project. The state-permitted pilot project was approved in November 1994 and was initiated in 1995
upon delivery of windrow turning equipment.
PROJECT OVERVIEW
Chnp Lejeune's solid waste reduction and recycling efforts are drivenby Department of Defense, Marine
Corps, and State of North Carolina solid waste reduction and recycling goals and State of North Carolina landfill
disposal prohibitioas. In developing the Base's solid waste management plan, a solid waste sorting, sampling, and
analysis exercise was conducted io the fall of 1993 at the sanitary landfill. The characterization analysis included
waste from households, offices, and commercial and industrial activities. Results of thesampling analysis indicated
that compostable materials such as paper products (37 percent), food wastes (15 percent), and yard wastes (three
percent) comprised approximately 50 percent of Camp Lejeune's landfilled solid waste stream.
In contrast, the
compostable fraction of the United States' landfilled solid waste stream totaled 41 percentin 1994 and consisted of
30 percent paper products, three percent food waste, and eight percent yard waste.
Based on this analysis, it was estimated that as much as 8,OOO tons, about 30 percent by weight, of the
materials landfilledat Camp Lejeune could successfblly be collected for composting given realistic collection rates,
projected capture rates, and contamination levels. Camp Lejeune officials decided to undertake a year-long solid
waste pild compost project as a means of gaining experience upon which to evaluate the implementation of fulla
xale facility
Tbe_State of North Carolina Solid Waste Section issued a permit in November 1994 to Camp Lejeune for
a Municipal Solid Waste Compost Demonstration Project to be operated over a 12-month period
at the Base’s
sanitary landfill; the project was initiated in October 1995. By conducting this project, G m p Lejeune has gained
the necesmy experieoce to &ermine the exto which long-term municipal solid waste composting CM be
feasibly cooducted aboard h.
Tbe project m t e d various mixes of compostoble maiwiah
yard wastes,
food wpstes, pulverized dsbrdded paper, chipped wood waste, corrugated cardboard, horse mpnure, wastewater
and woter plantsludges, and wood dr. F
W compostbps beea tested using the Toxicity CharacteristicLeaching
Procedure. No limitmg pcvpmebn h v e beep identified and the hished compost mptefipl has successfully been
wed in borticulturd rpplicotioos d to reptore topsoil depleted, sandy lonm soils.
n
ic
w
Objectives of the stabpermitted pilot solid waste compost demonstration project+re to:
Evaluate cornposting various mixes of available material generatedat Camp Lejeune to gain experience
upoa wtucb LO e v d u p c tbe i m p l d o n of a full-scale facility;
~~rbot~B.ee-peowotedyprdw~CMbecomportedpndbeneficirrllyfeused;
Establish & d w J o
p
e
procedures for meeting patbogea reduction requirements;
chprscreriotico and dem>astrote suitable uses of the resulting c
o
m
p
o
s
;
t and
FurtheF &tine solid w.de reduction capabilities and equipment requirements ofa full-scale solid waste
compog! k i l i t y .
This paper ,womarizes procedures used to successfullycoordinate and implementtheyear-longpilot
project. It also preseats the results obtained through c o m p o s t i n g various ratios of permitted solid waste materials.
Windrow mixes, formption techniques, huning regimes, and moisture additioo requirements are discussed. The
d
u
tq umpookd mptetirrlr have beep subject to numerous laboratory analyses. Thecharacteristics of the
canpmt rue discuosed in tbe p a p aa w d as product distribution details and d
t
s
.
COORDINATION PROCESS
T b project was inithdby t& Base Envinxuneatal Manageaxat Depprtment,EnviraMlentol Compliance
Division, Pdlutioa Prwdiua sectioo rod was conductedat the Bme sanitary lpodfill by the Facilities Department,
Bme MPiaterrPlrce Diviioa, Reeds rod Grwnds Section. Technical catroctor support was provided by Pprsons
Engineering Science. M d y meetings were held pmong project participants to ensure that the project stayed on
track. Diocuofiolr bpi= i n c l u d e d planned windrow mixes, progressto dab, problems and observations,and finisbed
m
a
e
t
d a p p l i d o a projects. Meeting participants routinely included State regulators, temperature takers,
mess hall
manager, horticulturist, equipmeat operators, project support contractor, and project k g e r .
Time regular monthly meetings proved very valuable in providing an opportunity for input from various
and buy-in, and kept open the lines of communication
among the vuious BMC depummb. Moot Import.ntly, it helped pave the way from a pilot project to a full-scale
pemaneatly &g
solid waste compost facility. M d y meetings were also supplemented by daily
commuaicatioo between the temperahue taker, project amager, and equipment operator supervisor. This helped
to &lit&
d rsinforce standad operating procedures, ensure that windrow turning or moisture addition was
rccomplished (LO n
eeded,and m
a
im
id
i the occurrence of windrow failure.
Bpse persoaoel, promoted projed bmktorming, synergy,
PRE-COMPOSTING CONSIDERATIONS
A primary coosideration before officially beginning the pilot compost project was to have appropriate
windrow turning equipment on site. In the past, a front end loader had been used to turn yard waste windrows.
That processwasextremelytime
consuming, did not adequatelyinvertwindrows,andresulted
in extensive
F
incorporatioa of soil into windrows. Although the project p e r m i t was received in November 1994, the project was
September 1995 when windrow turning equipment was available.
not officially initiated until
A secondpry project consideration was manpower limitations. The additional tasks associated with this
project - food waste collection, paper collection, temperaturetaking, windrow turning, project monitoring, record
keeping, and project management
were all incorporatedinto work schedulesofexistingpersonnel.When
considering permpneptly sustpining the level of effort necesspry to operate the pilotor expanding from the level of
effort required to d u c t the pilot to a larger d e project, optimizing limited menpower resources was critical.
-
WINDROW MATERIALS
An objective ofthe pilot project was to evaluate the composebility and compatibility of severalsolid waste
stresms geoerpted at Camp Lejeune. The Stnteisnred permit allows the following materialsto be composted at the
project site:
.
Yard waste including grass clippings, twigs, leaves, and pine needles;
Untreated wood waste including tree branches, large limbs, and stumps;
Food waste from mess halls;
*Cormgated cardbonrd, clean or soiled;
Paper such aa undeliverable bulk mail from the Base Post Office;
* H o n e mpoure from the Bsse stables;
Water oofteaino lime sludge;
Wpstew.ter treahmt plant sludge; and
Wood ash from the biomass project.
sources.
Yard w
as&,untreated wood waste, and paper provide primary windrow carbon
Yard and paper
wastes are deposited a d co-mingled in a designated area wherethey are stockpiled until anew windrow isformed.
wben a oew w i d r o w is formed, yard and paper wastes are processed through
the tub grinder. This eliminates
large limbs that might jamb windrow turning equipment and helps to jump start the yard waste decomposition
process. Through experimentation,use of a one-inchscreen on the tub grinder was determined
to be most effective.
Use of a tinex ecree~cauaed the bullring ageat to breakdown too m n resulting in too little pore space in the
windrows. It waa Joo f d that yardwaste should be ground as close as possible to the timeof windrow
formation. W k m ground yard wpptB wp8 otoclpiled, it began to decompose prior to being formed id0 windrows.
This was especially detrimeotal during the d y molrths of the project wheowindrow nutrient soutces were minimal
due to limitatioas 011 the amount of food waste that could be collected and colder ambient air temperatunxi. This
was not the case with untreated wood waste which owld be ground or chipped into one-inch sized piecesahead of
its scheduled use md stockpiled wrccessfully in a designated area at the project site.
Food waste, horse manure, d wastewater treatment plant sludge provide primary windrow nitrogen
sources. Food waste is collected in water-tight containers individually serviced and transported to the project site,
Monday through Friday. Food waste is added to a windrow on a daily basis during a
two-week period after
windrow base materials are laid down. Several food waste collection containers were already used at mess halls
to collect k
i
t
c
h residuals for laadfilling; severalothers were purchased to increase the quantity of food waste that
could be collected d diverted to the compost project. Pulpers to process kitchen residuals were already in place
at Camp Lejeune mess halls and have proven to be valuable to help with the consistency of the food waste. The
pulpers can be adjusted to reduce or increase the amountof free liquidin the food waste. As the project continues,
it is believed that the w e of these pulpers can be refined to minimize the addition of water
to windrows by
increasing the liquid coateat of the food waste during dryer periods of the year and vice versa. However, the
amount of liquid in the food waste will be limited by the collection process. Wastewater treatment plant sludge is
added M (L nutried supplement only and is deposited when a new windrow is being formed.
Soiled corrugated cardboard was also successfullycomposted in some windrows. The cardboard was
contaminated with food residuals, vegetables oils, etc., and was separated at the Base materials recovery facility
from material slated for recycling. Cardboard was delivered separately to the project site and was processed in the
tub grinder when a new windrow was being formed. It was mixed with yard waste at a ratio of approximatelythree
parts yard waste to one part shredded cardboardand used in forming the initial windrow prior to adding food waste.
Horse manure was used successfully in several windrows but has proven to be difficult to collect. Unlike
the othermaterialscomposted,horsemanurewas
not previouslycollectedandlandfilled.Themanurewas
stockpiled at the Base stables and picked up by gardeners for use on garden plots. Stockpiled manure was added
to some windrows but did not enhance the process enough to warrant the additional labor collection cost.
Water softening lime sludge was included in the pilot
to determine if the resulting compost could be
enhanced by its addition. This material presents a management problemto the Base as there is no established means
of disposal or reuse currently other than the Base landfill.
Each of the materials listed above was used during the first eight months of the pilot project with the
exception of the water softening lime sludgeand wood ash. Water softening lime sludge is scheduledto be included
in awindrow to be formed in July1996. Wood ash is anticipated to be available in August 1996 when an
experimental biomass energy generating facility, under construction at Camp Lejeune by the U.S. Environmental
Protection Agency, will be operational.
During the first eight monthsof the project approximately 1071 tons of yard, wood and paper waste were
usedin forming 15 windrows. The ratio of food waste to yard and wood waste increased considerably over the
course of the project. In the first windrows, the ratio was a low as 1 part food waste to 10 parts yard and wood
waste. In the more recently constructed windrows, the ratio has increased to 1 part food waste to 2 parts yard and
wood yaste. A total of 230 tons of food waste, 7 tons of wastewater treatment plant sludge, and 29 tons of horse
manure were composted.
The pilot compost project has also been used to divert some special food wastes from the Base landfill.
For example, several tons of pasta which could not be served due to expired shelf- life were added to a windrow
composed of yard and food waste. The pasta presented a special handling problem because it was so dry. The
pasta was soaked in water for several hours prior to being mixed into the windrow. Water also had to be added
several times during the composting cycle.
WINDROW OPERATIONS
Standard procedures for windrow formation were developedas the pilot project progressed. This section
discusses procedures used in forming, monitoring, and turning the windrows. A spreadsheet data management
system was develop to track daily procedures, windrow composition, and monitoring results for each windrow.
Windrow Formation
Standard operating procedures during the project have been to form a new windrow approximately every
two weeks. This schedule was developed primarily due to the limited amount of food waste able to be collected.
Fifteen to 20 tons of food waste could be collected within a two-week period. A windrow of approximately60 feet
long provided an adequate carbon to nitrogen ratio using the available food waste. Extending windrow formation
time to greater than two weeks resulted in limited success reachingpathogen reduction temperaturesequal orgreater
than 131 degrees F and maintaining that temperature for 15 days. The windrow often began to heat up during the
time food waste was being added andthen cool off before the requisite 15 days after the
last of the food waste was
added. A 60 foot windrow could also be turned in a relatively short time period allowing adequate turning time
for all active windrows given available manpower resources.
The bulking agent of ground yard wastes, chipped wood wastes, and paper was formed into a windrow
approximately 60 to 80 feet long, 12 feet wide, and six feet tall. The size was determined by the capabilities of
the windrow turner and to minimize required windrow turning time. In windrows where sludge or horse manure
was used, it was added during initial windrow formation with the bulking agent. After
the bulkmg agent was
formed into a windrow, food waste waS added during the next ten work days. Food waste was placed daily in a
trench on the top of the windrow and covered with b u h g agent. During the last five days of food waste addition,
tbe windrow was turned after each food waste addition. Thrs provided good mixing of the ingredients before the
stprt of tbe 15&y potbogen reduction cycle during which the windrow was maintained at or above 13 1 degrees F
and turned at least five times.
Eoch active windrowwas d t o r e d daily for temperatures, odor, and moisture. Temperature monitoring
wna performed using a four foot probe; odor and moisture monitoring were determined subjectively.
Temperstures were recofded from four, evenly-spaced locations dong the windrow at depths of two and
four feet into the
The temperature rwdings from the two foot depth were used for monitoring
achievement of bmperohres sufficient to destroy pathogens. Temperntures were not recorded on weekends. For
purpores of achievingpdwgeo reduction, temperatures were considered to remain at the temperrrtures recorded on
Friday as loog PO the kmpmtum recorded on Monday were dso above 131 degrees F. Temperature monitoring
was continued after the 15&y pathogea reduction cycle was documented, though
on a less frequent h i s . Compost
was not distributeduntil the tempemure of the windrow stabilized at less t h 35
~degrees F aboveambient
tem~erotureowitbout turning to emwe that the material was sufficiently cured. If the temperature of.windrows
coatinued to remain high, the windrow was turned.
windr~~.
Although temperature was the primpry indicator used to determine when windrows needed to be turned,
windrow odor and moisture were also noted daily and considered for this purpose. This assessment was made at
the sorqe time that temperahues were
The following standardized terms were defined for assessing odor
d moisture CaOdiriaaE of windrows:
recorded.
Moisture;
W~-wwcrterrunsoutw~ahpodfulofmPterirrlissqueezed
Moist handful of mpterirrl fonns a ball under moderate pressure and holds together for at
least 15 d
Dry not poaoibie to form a ball with mpterial thot holds together for at least 15 seconds
Very Dry dust evideat when material handled
-
-
-
If a windrow was described as smelling likea
m
m
o
& or rotten eggs, or was 'wet", it was turned that day.
If a windrow was rated as dry, the windrow was sprayed with wateras soon as practical unless rain was forecasted
for that day or the next day. Because the facility is uncovered, it is extremely susceptible to weather conditions
which requires operotors to be extremely flexible. In addition, standard operating proceduresmust change with the
seasons.
An oxygen meter was recentlypurchased to enhancewindrow monitoring effectiveness. Theoxygen
quantification allows more accurate information on microbial activity. The meter serves as an aid in determining
the need to turn the windrow by indicating the oxygen level present in the windrow.
A Scat windrow tumer model 482B pulled by a bulldozer was used to turn the windrows. In addition to
initial turning of the windrows during the formation periodto mix and aerate the materials, windrows were turned
periodically to increase oxygenandincorporatemoisture.
The need forturningwasprimarilydetermined
by
pssessing thetemperaturereadings
and moisture and odor ratings. When temperaturesstartedtodrop
to
approximately 134 degrees F, the windrow was turned that day. Also, if temperatures escalated to 150 degrees F
or higher, the windrow was turned that day. When the moisture rating was "wet", the windrow was turned
that
day, some times as many as four times in one day to provide adequate aeration. This proved to be particularly
important in the colder months.
After pathogen reduction temperatures were achieved for the required 15 days, turning was continued on
a less frequent and urgent basis. Turning helped to ensure the compost was cured and
to reduce the compost
moisture level to that necessary to screen the material (dryer material screened more easily).
ANALYTICAL, MONITORING
Prior to distributing compost from the pilot project, finished compost
was sampled and subjectedto several
laboratory analyses. Generally, windrows were sampled once every three months. A composite sample from each
windrow was analyzed for: percent moisture, percent humic matter, nitrogen, phosphorus, potassium, soluble salts,
pH,cadmium,copper,iron,lead,nickel,selenium,
and zinc. Forwindrows towhichsludgewasadded,the
composite sample was also analyzed for mercury and arsenic.
The composite samples were collectedby hand auguring into each windrow at approximately four evenly
spaced points. Thesample material was pulled fromapproximately two feet into thecomposting mass. The
compost from all sample pointswas mixed in a stainless steel bowl. A sample box, supplied by the laboratory, was
filled with approximately one cup of material from the bowl. These samples were analyzed by the State of North
CarolinaDepartment of Agriculture Soil andAgriculturalWasteLaboratories.Theselaboratoriesoffervery
reasonably priced services to the State agricultural community.
For windrows to which sludge was added, the
compositesampleswerealso
analyzed for mercuryandarsenic.
The Statelaboratories do notperform these
analyses so a private laboratory in Jacksonville, North Carolina was used. In addition to the chemical parameters
listed above, the composite sample foreach windrow completed within a quarter (three month period) were further
composited into one sample which was analyzed for fecal coliforms. Analytical data for the windrows sampled
to date is compiled in Table 1.
DATA MANAGEMENT
A spreadsheet wasdeveloped using Lotus 1-2-3 software to organize the daily monitoring information from
the windrows as well as the analytical results of quarterly sampling. The spreadsheet includes cells where the
following information is entered:
Date of windrow formation;
Approximate tonnages and cubic yardages of materials in each windrow;
Daily temperature, moisture, and odor ratings;
Nutrient and metals concentrations; and
Volume of material in windrow following compostingand curing.
Usingtheentereddata,
the spreadsheetcalculatesthepercentreduction
of materialachievedthrough
composting. Temperatures are also graphed to demonstrate achievement of sufficient temperatures for pathogen
reduction.
DISTRIBUTION
Prior to material screening, the compost was sufficiently cured (asdemonstrated by temperature that did
not rise to more than 35 degrees F above ambient air temperatures without turning) and analytical results from
sampling were received and reviewed. Screening was found to greatly increase the usefulness of the material by
improving the texture and removing contaminants such as plastic and metal debris and large sticks. A three-sort
screenerwas used producingoversizeddebris,medium
sized compostmaterial,andfinelyscreenedcompost
material.Afterthe
cured material was screened, the medium and finely screened materials were distributed to
selected locations where the material was used as topsoil amendment.
19
Base soils are primarily sandy loam with little topsoil. Limited topsoil resources are available throughout
the Base raising the value of the fished compost to the rnaintennnce and &cement
of Camp Lejeune's grounds.
The finishaj compost semes M m important topsoil amendment d will provide a continual s
o
w of valuable
topsoil amedmnt material.
Compost was first applied as part of a coordinated effort
to improve the grounds around
barracks. Denuded
were covered with approximately 8 to 10 truck loads of material which were used as a top dressing
mixed with mil and tben seeded with grass during the second week of April. Within a few weeks the seed was
law
ptep6
germhated and provided approxixuately 90 percent coverage over the area. Future projects will include application
to food plots when wildlife fodder is grown, the Base golf course, a newly constructed range, landing strips,tank
fTpils,andBfo4iooprolre~.
Uee of the tinisbed compost m a t e d will be promoted though Camp Lejeune's self-help program which
available to Marine and civilian units to pccomplish s d projects. This mechanism was
succeoofullyuaed b rssbn the bamcka grounds during the pilot project. Given the limited budget and labor pool
for g
d mpintnnnncc, the self-help programwill
be M important mechanism to utilize the m
a
t
e
d
.
Md~twmnlly,coatractors working aboard Base CJU be given occes6 to government furaished,mpterials, such as the
finisbed c
o
m
p
o
s
,tto u8e in contracted projects.
&
e
ad
LESSONS LEARNED
By d u c t i n g this project, Camp Ljeune has gained the necessary experience to determine the extent to
which long-term municipal d
i
d waste composting canbe feasibly d u c t e d aboard Base. Along the way,
numeleswa~w e l e a r n e d that e n a b l e d the project to be successful. ~hese~essonsare s u m m ~ r i ~ ebelow:
d
-
success.
Firor and foremost, project buy-inis d
o
l to ehsure project
This included
support fnw all pertiso involved in or rssociatcd with the projectincluding mPnagement personnel,waste
geperptora, C
d
e
lco
tro, d compoft equipmeat operrrton. All parties must listen to the requirements of others and
be wilknp and ab& to rewin flexible and alter standard practices where
mxssary.
. . - Daily communicrrtion between all parties
helpsto ward off problemsearly and provide
quicker aolutiaas to p d e m s when they wereencountered.Adequatecommunication
wasaconstanteffort,
especially as playen changed throughout the life of the project.
.
w
- Smaller is not necessarily better. Processing materials in tub
a grinderwitha
=rea smaller than oaeioch in sile produced a b u b g agent that was too fine to provide adequate windrow pore
space. Am, with smaller ~ctee~p,
wear increased on the grinding equipmentandprocessingtimeincreased.
sooOer is not necessrrrily b&& t h la
~ter. Grindingyardwaste to be used forbulkingagent
must be done
immediately prior to wiodrow f d m . Grinding too far in advance and then stockpiling mptefiol can waste the
errergy pwmted by its decompocitioa. Ooce g r d . tbe natural decomposition of tbe yard waste is ecceleratd.
This initial beating is useful to 'jump start' the composting process, especially when minimal nitrogen sources are
available, M was the case in the fall d winter months.
-
Food Waste P
ul~h Pulping food waste proved to be very advantageous because it produced a
uniform m
a
t
e
d
.The pulped food waste composted at a relatively even rate and minimized the presence of large
pieces of food (fruit) in the f d product. In addition, pulped food waste tended to stay in place in windrows.
Items such as whole fruit had a tendency to roll away from the windrow during turning.
-
It is easier to establish standad operatingprocedureswith a limited,manageable number
of sbort wmdrows. This minimi.rpd the M o u n t of m
a
e
t
d to be handled in a given amount of time and increased
operation flexibility. In &tion, this approach resulted in less m
a
e
td to rehandle if a particular windrow did not
compost well.
ODeratinn ProceQureS
-
Procedures will vary from season to season due to variab!e
temperatures and rainfall in eastern No& Carolina and the uncovered project site. B u h g agent variability also
requires sepsoapl operation a d j u t a a t s . Increased quantities of gnus in spring and summer reduces the need for
supplepseotd water; increased quantities of leaves in the fall and winter increases the need for supplemeatal water.
-
S c d g is an a d d i t i o d step that isworth the time and equipmentinvestment. It serves
to remove contaminants resulting in a more desirable horticultural material. The finished product is more uniform
in size and is relatively Free of cootaminants such as plastic and metal debris and large wood pieces.
Water - Easy pcce88 b large quantities of water is essential. It was not uncommon to spray 1,OOO to
2,000 gallaaa of water on active windrows on a given day during some times of the year eve0 at this small pilot
project site.
.
- Turning is required frequeotlyduring
food waste additionand the
active
composting
@ of patbogem reduction. W l m temperotureo were above 134 degrees F, frequeot turning (one or more times
per day) did not a d v d y impact the decomposrtioo pmcess as long as windrows had adequate moisture. When
temperaturea were lower, 131 to 133 degrees F, turning some times resulted in temperptures dropping below 13 1
degrees F the next b y .
-
Curiqg Finished compost should be kept in windrows rather than a large stockpile priorto
scteeoing. M a t e d that was stockpiled was wetter than windrowed material and therefore more difficult for the
s c h g equipment to process. Stockpiled material was windrowed and turned several times for several days to
dry out the material prior to screening.
-
Camp Lejeune compost tested high in soluble salts and thus is not suitable as a straight
plan&ngmedium. For exaq.de, it should only be used as potting soil for plants when mixed with soil or peat moss
at8 d o of r~ I
d l:l.
CONCLUSIONS
Thc experieoce gained through this pilot project provides important insights for other installations
or local
governments seeking to achieve similar solid waste reduction goals or compost program objectives. Department
of Defense loftnllotioashave a unique opportunity in the communities and states in which they are l o c a t e d : they
can take the lead in implementing innovative solid waste management and reduction programs such as this and
demoastrate their commitmeat b environmeatnl quality and resource conservation. Such a proactive approach to
this issue reflects positively oo the Department of Defense and on the high quality of p
e
r
s
o
d leadership at each
installation.
52
DEVELOPMENT OF A LEAF DISTRIBUTION PROGRAM FOR ON-FARM COMPOSTING
Archer H. Christian
Department of Crop & Soil Environmental Sciences
Virginia Tech
Blacksburg, Virginia
Gregory K. Evanylo
Department of Crop & Soil Environmental Sciences
Virginia Tech
Blacksburg, Virginia
INTRODUCTION
On-farm recycling of many organic wastes can benefit both agricultural and urbanisuburban communities by
producing a valuable soil amendment, mitigating some animal waste disposal problems and reducing landfill
burden. Most agricultural soils in Virginia and other southeastern U.S. states are inherently low in nutrients and
organic matter, the cost of which is paid in high off-farm inputs. Top soil removed as part of the suburban
development characteristic around metropolitan areas in the southeast, must be replaced and heavily fertilized at
substanfial cost. following construction activities. The utilization of properly processed composts to improve soils
and as potting media substitutes has been well demonstrated to improve soil chemical and physical properties and
enhance plant growth and health. Certified Organic farming operations regularly rely on composts to increase soil
organic matter and nutrient holding capacity, and to suppress disease. Composting easily source-separated, organic
municipal and agricultural wastes positively addresses the need for alternatives to disposal and for improvements in
agricultural, horticultural and residential soils.
Virginia’s 1995 municipal solid waste volume is estimated to have exceeded 9 million tons, (U. Brown, personal
communication, 1996). Although yard wastes generally constitute approximately 15 percent of this flow (May and
Simpson, 1990), only 354,000 tons were recycled in 1993 (Steuteville, 1996). Most waste management entities that
collect leaves keep them separate from solid waste and make the leaves available to citizens. Additionally,
legislation exists allowing municipalities with a composting’program capable of handling locally generated yard
wastes to ban landfill disposal of those wastes. However, beneficial use or recycling of Virginia’s collected leaves
is not practiced on a broad or systematic scale. Virginia’s agricultural sector annually produces approximately 18
million tons of animal manures (E. J . Fanning, personal communication, 1996). Much of the collected material is
spread on forage and hay fields, but continuous application is limited by agronomic rates and frozen ground
conditions in order to protect ground and surface waters.
There has been minimal effort to date to recycle municipal yard wastes and manures through on-farm
composting in Virginia; however, there are advantages to combining these wastes for composting. The low
carbon:nitrogen (C:N)ratio and the high moisture content of animal manures and the high C:N of leaves and other
woody yard wastes make them difficult to compost individually, but these properties make them ideal for cocomposting. The availability of leaves coincides with that of manures that are collected but cannot be land applied
during the winter. On-farm composting can be conducted adequately using standard farm equipment, such as a
tractor with bucket and manure spreader. Additionally, farms often have more suitable land area available for
composting than do municipalities or other landfill operators.
On-farm composting to successfully recycle municipal yard wastes requires education, the establishment of
linkages among local government, waste managers, and farmers, the facilitation of flow of resources, proper
processing, and market development. To achieve the efficient recycling of wastes for producing beneficial soil
amendments on-farm, Virginia Cooperative Extension (VCE) specialists established a cooperative composting
project with the Rivanna Solid Waste Authority (RSWA) in Albemarle County, Virginia. The project was partially
I
funded by the Southern Region Sustainable Agriculture Research and Education Program.
OBJECTIVES
The overall objective ofthis project was to develop a process for recycling of municipal yard wastes onto
agricultural land for cornposting and to document that process for implementation by waste managers throughout
the southern United States. Specific objectives were:
1. to develop a collaborative program between VCE and the KSWA, to distribute leaves to area farmers for
composting and utilization;
2 . to provide educational, technical and troubleshooting assistance to participating farmers to ensure a high quality
finished compost;
3. to develop and provide educational programs for other, non-participating farmers and agricultural professionals
about the composting process and soil quality benefits of recycling organic wastes onto land:
4. to demonstrate the benefits of compost application on soil, physical, chemical and biological properties and crop
growth in on-farm tests;
5. to develop a handbook and an electronic version for use in the Southern region for waste managers to utilize in
implementing a yard waste distribution system for on-farm composting. This guide will be a collaborative
effort between extension specialists, farmers, waste managers and researchers that documents successful
education. technology transfer, troubleshooting and demonstration processes.
METHODOLOGY
Project Collaboration: Extension project coordinators collaborated with the RSWA to establish a plan to deliver
leaves collected in the fall and winter of 1994 and 1995 to area farms. The KSWA and local Extension personnel
solicited farmer participation through advertisements and personal contact. Two informational meetings were held
to present the details of the program and establish respective roles. Six farms representing the landscapehursery
industry, organic vegetable production, and beef cattle operations participated in the program.
Furmer Educafion. Some of the participants had previous composting experience; nevertheless, farmer
education was an important part of the project. The following combination of educational techniques was utilized:
I . Project coordinators organized a field trip for the group (including a representative from RSWA) to visit an
on-farm composting system in northern Virginia, operated by an experienced on-farm composter. The farm
manager utilizes a self-propelled windrow turner to co-compost a wide variety of organic materials, including leaves
from a nearby city. The finished compost is applied on the Certified Organic vegetable farm. Process control, endproduct characteristics, and compost utilization in crop production were demonstrated and discussed.
II. A 30 page handbook was developed and provided to each of the farmer participants as a resource guide on
composting principles, processing, troubleshooting and end-product quality guidelines, and recommended
application rates. Tables and charts for recording equipment usage, labor expenditures, windrow temperatures, and
experimental results from field/pot trials were included. The notebook was reviewed with each participant during a
farm visit prior to the start of herhis composting. This notebook was supplemented with selected articles and
publications on composting on an as-needed basis.
I l l . The project’s Farm Management Specialist provided individual training to most of the farmer participants in
utilizing spreadsheets for fixed and operating cost allocation in order to enable an accurate assessment of the
economics of the composting operations.
IV. Three on-farm field and greenhouse studies are underway to compare the effects of compost and
commercial fertilizer on soil physical and chemical characteristics and plant growth. An economic evaluation of the
program will be made by comparing the expenses associated with delivery, composting, and utilization of yard
wastes and manures with the expenses associated with landfilling wastes and the use of commercial fertilizer. The
research process will also provide a basis for further independent investigation on the part of participants.
Feedstocks. In mid-March of 1996 RSWA delivered between 180 and 250 cubic yards of bulk leaves to each of
5 of the participating farms Weather and delivery vehicle problems caused a delay beyond the anticipated
54
December-January deliveries. Under a separate agreement made by the 6th farmer directly with the City of
Charlottesville. approximately 160 tons (-990 cubic yards) of bagged leaves were delivered directly to his farm in
December 1995. Under this arrangement, the City also provided personnel to debag the leaves at the farm. The
total volume of leaves delivered to all 6 farms was approximately 2600 cubic yards.
All but one of the operations co-composted the leaves with animal manures, which were primarily chicken or
turkey litter from production operations in nearby counties. Off-farm horse stable bedding and on-farm beef
manure collectionsfrom winter feeding areas were also utilized at some of thesites.
Composting. Each farmer set up a system for windrow construction and turning/mixing that worked best for
herhis particular operation in terms of the availability of raw materials, equipment and labor. Initial pile
construction was performed with a tractor and bucket and, in some cases, additionally with a manure spreader.
Feedstock proportions were determined after estimating C:N ratios and bulk densities ofwaste materials from
previous analyses and from published figures, because composting began within no more than a few days after
receipt of materials. Laboratory analysis of the poultry litters and horse bedding used by the participants to cocompost with the leaves was performed to permit subsequent assessment of end-qualityas a function of mixtures.
Four of the participating farmers utilized a RSWA tractor-pulled type windrow turner to turn their compost at
least three times. Additional turning and mixing of the windrows was performed with a tractor and attached bucket
or fork. Project personnel made regular farm visits to provide composting technical support.
At submittal of this paper, field trials have begun or are planned for three farms during summer of 1996.
Compacisons of compost amended and commercial fertilizer amended soil or potting media will be conducted.
Sweet corn is being grown at two locations and potted annuals and perennials at the third. Effects on soil chemical
and physical properties and plant quality and yield will be assessed.
OUTREACH
The Project team presented an On-Farm Composting Field Day in June as an In-Service Training for VCE as
well as an educational event for other interested individuals. It included demonstrations at two farms using two
different composting systems - turned windrows and static pile aeration. One of the project farms was a field day
site. A 13 page handout was produced for participants which provided a composting process overview and list of
resources. The audience of 32 included VCE agents, Soil & Water Conservation personnel, State of Virginia
Department of Conservation & Recreation Nutrient Management Specialists, farmers, and nursery operators from
many parts of Virginia.
The project team conducted an educational forum, The Successful Municipal Yard Waste Composting Program,
on August I , 1996 at the annual conference of the Virginia Recycling Association. The program addressed
composting principles, technologies, regulations, practices, and successful publiciprivate partnerships. Project team
members and participating farmers were among the presenters. The audience for this event included public and
private waste managers, VCE personnel, private composters and marketers, educators and planners.
Various articles and publications have been and will be produced for appropriate audiences as part of this
project. Publications to date have been an Extension bulletin, On Farm Leaf Mulching: An Optionfor Farmers and
Municipalities, and an article entitled Yard Waste Composting Opportunitiesfor Farmers are Enhanced by
Available Exemptions From Sfate Regulations, published in the December 1995 Crop & Soil Environmental Science
News and the Winter 1995196 issue of the Virginia Biological Farmer, the quarterly journal of theVirginia
Association for Biological Farming. An Extension publication based on the farmer notebook developed for this
project is in preparation. The Virginia Yard Waste Management Manual, first published as an Extension
publication in 1990 ( I39 pages) is being revised and updated for a second edition release. The manual is designed
to serve as a total management guide for local government officials, extension agents, and private sector individuals
in the siting, design and operation of a yard waste management program. It also provides information on collection
reduction strategies, and identifies ways to tap potential publiciprivate linkages for yard waste recycling,
55
The Pro.ject handbook W I I I be an Extension publication documenting the project and providing guidelines for
other waste management entities and/or groups of farmers and others to utilize for similar programs. It will
complement the Virginia Yard Waste Management Manual and provide information on: a) economic.
environmental and agricultural benefits: b) establishing the farmer-waste manager connection; c)strategies to
address barriers and meet the needs of participants; d) the economics of on-farm composting of leaves and
agricultural wastes; and e) conducting successful education, technology transfer, troubleshooting, and overall
program management. Guidebook abstract, highlights and program component summaries will be available through
the VCE web site.
Field days are being planned for Spring 1997 to demonstrate the effects of compost in the field and pot studies.
These results will also be published in appropriatejournals, newsletters and Extension bulletins. Conference posters
and presentations such as this event are also part of the project outreach.
RESULTS AND DISCUSSION
Farmer feedback has been positive, and most plan to continue to compost on a large scale. Finished compost has
been used in landscaping projects, bagged and sold from a nursery retail operation, and sold in bulk from at least
one farm. The City of Charlottesville found direct leaf delivery to a farm to be a better option than stockpiling at
the present location. One of the participating farmers has signed a 5-year contract with the City to receive 1,000
tons of leaves annually.
Problems also occurred despite the general positive response. The major impediments to a successful program
were:
1 . Leaf delivery logistical and timing problems resulted in later receipt of leaves than desired by farmers for
efficient composting initiation. Delivery truck breakdown and weather conditions also delayed composting start-up
dates. Five of the six participants did not receive leaves until March, when spring growing season activities were
already underway, making it difficult to attend to the windrows to the extent desired and advised.
2 . Inadequate space and inappropriate slopes hindered optimal compost pad siting in two cases. Adequate space for
300+ cubic yards of material is not necessarily hard to find on a particular farm; but equipment access and
maneuverability, and surface slope are important additional considerations. A much greater volume of leaves than
initially planned was delivered to the farmer participating in the direct-haul arrangement. This resulted in the
windrows stretching beyond the original site into a swale, where the soil was often too wet for equipment traffic.
Additionally. the windrow turner was difficult to maneuver on even slight down-slopes.
3. Utilizing a manure spreader for initial windrow construction is effective only when small volumes of alternating
individual feedstocks are added continuously or feedstocks are layered in the spreader before operation; otherwise,
the resulting windrows will simply include unmixed sections of single feedstocks. Follow-up mixing with a manure
spreader is very effective, but it is not as economical as utilizing a tractor with bucket, a front end loader or a backhoe.
4. Variations in process performance occurred with the same approximate mix of 6 parts leaves to 1 part
litterhanure (vol/vol). In some cases, the windrows continued to heat to temperatures greater than 60°C for several
weeks following daily or every other day turnings. Temperatures rarely exceeded 120°C at other sites. This result
illustrates the impact of both feedstock characteristics and cornposting conditions. Differences in C:N ratio,
moisture content and bulk density were inevitable among different litter sources. Litter was stockpiled uncovered
for up to a month prior to windrow construction at some locations, and the age and condition of the delivered leaves
varied. Proximity to a water source for re-moistening windrows at turning, normally an important consideration,
was not necessary in this project because precipitation was adequate to meet composting water needs. In fact,
excess water supply by snow and rainfall resulted in longer cornposting times than expected for most farmers
because of lack of equipment or labor and time to adequately aerate the windrows. However, no objectional odors
were reported by participants or their neighbors. Laboratory analysis has not been conducted on the final products
at the time of submittal of this paper.
56
r
CONCLUSION
1
This project is demonstrating that increasing waste recycling through composting of municipal yard trimmings
and agricultural manures on farms can be an attractive opportunity for many farmers and an economical option for
waste managers. A multi-focused program providing information and education and facilitating relationships can
insure success. Generators, haulers and farmers all need to be aware of the importance of feedstock consistency in
efficient processing and a high quality end-product. Farmers also need to be aware of the impacts of climate and
age on feedstocks and the constraints imposed by equipment, labor and time in order to maximize qualityand
minimize processing problems. Establishing linkages between the agricultural and waste management communities
can help all parties realize the benefits of municipal yard waste recycling on farms and improve the future
productivity of agricultural and horticultural soils.
I
REFERENCES
May, J.H. and T.W. Simpson. 1990. The Virginia Yard Waste Management Manual. VA Cooperative Extension
Pub. NO. 452-055.
Steuteville, R . 1996. The State of Garbage in America, Part I . BioCycle, 37(4):54-61.
THE BIG AND SMALL OF BIOSOLIDS COMPOSTING
Todd Williams, P.E.
R. Allen Boyette,P.E.
E&A Environmental Consultants,Inc., Cary, North Carolina
Eliot Epstein, Ph.D.
E8tA Environmental Consultants, Inc., Canton, Massachusetts
Scott Plett
City ofDavenport, Iowa
Curtis Poe, P.E.
Harrisonburg-Roclungham Regional Sewer Authority, Virginia
INTRODUCTION
Bimlids ampstmg wntinues to be one of the more popular methods of biosolids management utilized in North
America. According to the most recent BioCycle survey (Goldstein, 1995), 228 biosolids composting facilities were
operational by the end of 1995 in the United States. The aerated static pileis still the mostpopular biosolids technology used
with 101 facdities or 44% of the total being that variety. Many communities
evaluating biosolids management options are
cmcemed with the cost of cornposting biosolids,the technolog used, and odors associated with the process. The technology
used keds to have flexibility to manage varying quantities and characteristics of biosolids. Composting facilities must be
operated free of odor problems and they mustbe able to process materials in a cost-effective manner. Two new biosolids
ampstmgfacilities which utilize the aerated static pile methodof composting began operation in 1995. One facility is a
large 28 dry ton per day ampstmgfacility that p'ocesses yard wastes as well as biosolids in Davenport, Iowa. This facility
is totayr enclosed f o r d OQr control. The other is a smaller 5.5 dry ton per day facility which is owned and operated
by the Hamsonburg-Roclangtuun R e g i d Sewer Authority in Mount Crawford(Harrisonburg area), Virgma. Tlus paper
p
v
i
&
s
a dehled desaiption of theequipment and facilities included in each of these two static pile operations, provides
a summary of the initial stages of operation, and provides a dehled cost comparison ofactual capital costs and operation
and maintenance costs of the two facilities. This dormation will provide valuable insight to various communities
considering cornposting as part of their biosolids management programs.
DAVENPORT, IOWA
The City of Davenport, Iowa operates a 26 million gallonsper day (MGD) capacity secondary treatment plant
which serves approximately 150,000 persons. Thckened sludge from the treatment plantis anaerobically digested prior
to dewatering. The resultant bimlids are dewatered u m g three two-meter belt filter presses to between13% and 20% total
solids. The dewatered biosohds were previously landfilled at the Scott County landfill. Increasing landfilling costs and
environmentalco~lcemover this practice prompted the Cityto consider alternative biosolids management techmques. After
au evaluation of all exdng management options, lime stabilization, and composting were evaluated fully. The Cityvisited
noperating facilities in 1992 and early 1993 to gather first-hand dormation about operating performance, costs,
and operator hediness of these operations. It was after h s evaluation that the Citychose aerated static pile composting
as the preferred management method.
After selecting composting as the method of choice, five issues were identified as crucial to the success of the
project. These issuesinclude the following:
0
0
0
0
Evaluation of various alternative sites
Manage Cityof Davenport and Scott Countyyard wastes
Effectively
manage
odors
Construct facility w i h budget
Cease landfdling biosolids by early 1995
In 1992, several potentialsites were considered for the construction of the composting facility. The existing Scott
County Landfill and land adjacent to the existing wastewater treatment plant (WWTP) were consideredas were othersites.
A parcel of land adjacent to the existing WWTP was selected due to its proximity to biosolids production and the
compatibility of surrounding land use.
The City also mede a commitment to manage all collected yard wastes from the City and Countyat the composting
faclllty since a 1 9 9 1 statewide ban on 1andfUing yardwastes had been enacted. Th~srequired storage and processing areas
and equipment.
odor management at the cayoshng facility was a critical planning consideration. Total enclosure of the mixing,
canposbn&and drying areas with all offgases bemg treated through biofilters was provided in the design tocontain and treat
the majority of facility odors.
The construction of thls facility needed to be done w i h the allotted budget. Through detaileddesign criteria
review and the selection ofpnaiW canpanents, the facillty wasable to have the design capacity required and those design
features desired by the O w n e r , while remaining w i h the established budget.
Due to increased costs and regulatory pressures, the City committedto cease landfilling the dewatered biosolids
in mid- 1995. Design permitting, andconstruction of the cornposting facility had occur
to on a fast-track schedule in order
to meet ths.The den@ ofthis facility was initiatedby E&A Environmental Consultants, Lnc. and Shive-Hattq
Engineers and Archtects in May 1993 with conceptual design completed by August. Final design was begun in October
1993 and completed in M m h 1994. Six bids were received, three of whichwere w i h the allotted budget. After receipt
of bids and selection of Estes Company of Davenport as the contractor, construction began in June 1994. Substantial
cumpldion of the facility occurred in August of 1995.
The Davenport canposting facility is designed to process 28 dry tons per day of20% total solids digested biosolids
cake on a five-day per week aperating basis. In addition to managmg biosolids, the facility is designedto manage up to
35,000 cubic yardsper year of yard wastes.Figure 1 shows the process flow diagram for the facility. A description of the
process flow and equipment features follows.
0
Site Chamcteristia - The compost facility is located on a 15 acre rectangular parcel of land immediately
south of the WWTP. This parcel abuts a railroad yard tothe west and the Mssissippi k v e r to the east.
City owned property on the southern border creates additional buffer area tothe only residential areas
within half a mile of the site. A 6-foot high, 3,500-foot long levee completely surrounds the site to
prevent flooding during a 1 0 0 year flood event.
e
0
Mal~ria6Dclivery and Processing - Only clean yard wastes are accepted for processing. Yard wastes
are delivered by private and public vehicles to a paved outside storage area. Yard waste quantities are
estimated volumetrically by vehicle size by operations personnel for material billing. Yard wastes
rtqumng size miuction are ground withan 800 horsepower horizontal grinder prior to use as a b u h g
agent A W !
to 70% reduction in yard waste volumeis achieved through grinding and stockpiling for
one month. Wood chips and shredded tires are delivered and stored under cover in the b u h g agent
storage area. Dewatered biosolids are hauled via seven and ten cubic yard capacity dumptrucks from
the WWTP to one of the two biosolids receiving bins.
Bulking Agents - The primary b u h g agents used at the Davenport composting facility are paper mill
suallty wood &IPSand shredded rubber tires. Wood c h p s are supplemented with shredded rubber tires
at a ratio ofone volume shredded tires to two volumes of wood chips. Because!the shredded rubbertires
are loOo/ae
r
c
o
v
e
e
r
d through sxeemng, the quantity andcost of new wood c h p s is reduced by o n e - h d .
shredded yard wastesare also used to supplementt h wood
~ ~ chiphire mixture at a rate of one volume yard
wastes for every four volumes of wood chipdtires. These materials, as well as recycled b u h g agent,
are stored under cover and then loaded into the automated
mixing system. A variable bullung agent to
biosolids ratio was allowed for in the design with anaverage volumetric ratio of three to one (3:1). A
pilot test was conducted to vex-@ the correct ratio and to produce a product for market evaluation.
0
0
M i n g - Mwng of the bullung agents with biosolids occurs in a totally enclosed, automated continuous
feed system. Biosolids and b u k n g agents are loaded into live-bottom hoppers for metering to the
llldanated mking
Two 50 cubic yard capacity biosolids hoppers and two 20 cubic yardcapacity
b u h g agent hoppas are provided Variable speed screw dnves discharge biosolids
and bullung agents
onto a feed conveyor at a rate which is automatically controlled by weight belt sensors connected to a
programmable controller. The bulking agents and biosolids are thoroughly blended in one of two
continuous feed pugmill mixers with the resultant b l e d discharged into a concrete bunkerat the south
end ofthe canposting building. odon>us gases from the mixing building are vented to the composthall
where they are collected for treatment in the biofiltration s y s t e m .
-
Composting Compostingofthe biosolids occurs in a 6 6 , O O O square foot building which is totally
enclosed and insulated. A 40 foot wide central access aisle separatesthe east and west aeration zones.
precast polymerized concrete trenches are placed six feet on center to provide aerationto the compost
p h . The facility design ellows fora one-foot base of wood chips to be placed over theaeration trenches
followed by eight feet ofmix and a one-foot insulative cover of recycledcompost. Compost pilesare 90
feet long. A customdesigned hole pattem was used in heavy duty cast iron covers to provide d o r m
mationdown the length of eachtrench. Four trenches are serviced by one of 24 aeration stations each
capable of pmvidmg 1,400 CFM at eight inches of water c o l u m n . Each blower stationis capable of
operating in induced draft (negative) or forced Wsitive) aeration mode, depending on operator
pefaence and the stage of the composting process. Negative aeration is practiced forthe first 10 days
of the composting process with exhaust gases being collected and vented directly to biofilters for
treatment. The blowers are then witched to positive aeration mode for the remainder of the 21-day
composting cycle toenhance drying ofthe mass. Offgas fiom the compost piles and thebuilding are
collected via centrallzed ducting for treatment withthe compost pile exhaust through biofilters.
The seration rate is controlled with a temperature feedback control system that is operated through the
facility computer. Up to four aeration rates are provided for each individual compost pile based on
variations in pile t m p e m b m . HI- temperatures result in an increased blower run time (odoffcycle).
Three thennocouples placed in the pile provide temperature readouts with the low temperature
thermocouple automatically selected as the temperature feedback controller. In thrs way, the oxygen,
cooling, and dryingrequirements for each individualpile are controlled independently of other piles.
Allowancz for up to five days of aerated dryingis provided in the composting building for periodic times
when additional drying is necessary. Th~sarea also serves as a yard waste pre-aeration area when large
quantities of grass clippings are received.
0
k e n i n g - A six-foot diameter by 35-foot long trommel is provided in the covered portion of the facility
at the ea& ad of the CompOBf bud-.
The satemng system is fed froma 15 cubicyard capacity happer
where front-endloaders deposit ullscreened compost material. The screen separates oversizematerial
for recycling into the compost process and a 3/8 inch minus compost product for curingand use.
CuringAemtion - Aerated curing is providedutilizing portable blower stations and re-usable perforated
high density polyethylene pipe. This area is located under cover adjacent to the screeningarea and is
sized to handle 30 days of screened compost production. Cycling timers operatedthrough the facility
computer control aeration cycles as necessary in this stage of theprocess.
0
Odor Control - Because of the high priority to effectively manage odors at t h r s facility, all building and
process exhaust from the mixing andcomposting buildings is collected and scrubbed through two large
biofiltas. Each filter is sued to process 105,oOO CFM of exhaust gas at a residence time of 45 seconds.
A 4 foot deep mixture of yard waste compost and woodchips is used as the biofilter media. Each filter
is &vided into four indepemdent zones with an individual booster fan and
controls. This allows for
61
redundancy during scheduled and unscheduled maintenance activities. Moisture control is provided
through in-line humidification and surface Imgation.
0
Compost Utilization - A compostmarketinganalysiswasconductedin
the Quad Cities area in the
Summer of 1993. Pilot &
e
swere also conducted to generate compost for testing and utilization
purposes. A strong demand for the product wasidentdied. Currently, the City has initiated marketing
of compost with i
n
b
persarmel. Pricing for thecompost which is sold in bulk is between$4 and $8
per cubic yard depending on quantities purchased.
Moving Stock - Moving equipment at the compost facility consists of two 1Ocubic yard capacity front-
end loaders, two S-cubic yard capacityfiont-end loaders and a horizontal yardwaste grinder.
The Davenport Composting Facilityhas been operating since August of 1995. Yard wastes have been received
at the fecility since May of 1995 at a rate a p p m c h g 38,000 cubic yards per year. An old tubgnnder wasused temporarily
to process yard wastes requiring gnndmg. However, a large capacity mobile hammermill-type grinder was recently
prachesed by the City to meet the yard waste gtindmg needs. The volumeof yard wastesis reduced to approximately 30%
ofthe m a m q v o l u m e after gnndmg and storage in a stockpile forone month. Tlus material is then blended withthe wood
chip/shreddedrubber tire mixture at a rate of one volume shredded yard wastes to fourvolumes wood chipdtires. The yard
wastes provide add~tionalenergy in the composting process which was particularly importantwhen wetter biosolids cake
was received as described below.
Biosolids loading to the composting facility averaged 21.3 dry tons per operating day for the first six months.
However, in September an upset condition at the wastewater treatment plant, in combination with an industrial facility
discharge ofa high svspended solids and BOD l&g,
ulaeased the overall biosolids production and, therefore, the loading
to the "mposting facility to an average of 32dry tons per opemhng day. The facility was able toaccommodate the increased
quantity of biosolidsby increasing the pile height. The existing mixing,aeration, and odor control systems were all able to
accoIllIllodateh s umxased quantity o f b k l d s without jeopardizing facility operation in any way. An additional problem
encountered as a result of the d
u
s
t
r
i
a
l facility discharge was thata much wetter (1 3% - 15%) biosolids cake resulted.
Cmaeqmtly,the dry ton loedng to the compost facility desreased dramahcally as the bulking agentratio had to be increased
to maintain the target mix solids umtent of 40% to 42% total solids. Less energy was available per volume of mix due to
the decreased amount of dry biosolids. Therefore, increased amounts of yard wastes were added to the bulking agent to
provide the nexxwuy energy to provide adequate drying during m p o s t i n g . Cake solids has since increased to the 17%
total solids range and is anticipated to continue to improve over the next several months.
ARer the initial start-up and shakedown of the mixing system, the system has been able to operate and to process
the quantity ofbiosolids generated in less than five hours per operating day. Tlus allows operators enough process
time to
construct compost pilesand move compost piles for screening.
The " e n i n g operation has recently passed its performance test requirements in February. The trommel screen
has a b
g
ncapacity of140 cubic yards per hour to achieve a 3/s-inch minus compost product. The performance test showed
that the saeen was able to process approximately 170 cubic yardsper hour ofmaterial. Due tothe delays by the equipment
supplier, the City rented a portable trommel screen for several monthsin order to generate recycled b u h g agent for use
in the mixing operation and also compost product for market development.
The odor control system has worked very well over the twelve monthsof operation to date. No increases in air
handhng system back pressllreshave been noted and no odar complaints have been receivedfrom theneighbors surrounding
the facilitysince its start-up.
Personnel
The facility is operated by nine full-time p e r s o n n e l and a number of part-time personnel as follows: A
superintendent, a clerk, six operators, one laborer, one part-time clerk (for weekend yardwaste deliveries), and two parttime laborers in the summertimefor various housekeeping and maintenance activities.
62
HARRISONBURG, VIRGINU
The Hamsonburg-Rochgham R e g i d Sewer Authority (HRRSA) located in Mount Crawford, Virgma operates
a 16 MGD capacity secondary treatment plant whch serves approximately 40,000 persons and a si@lcant amount of
mdustnal wastes hfour a m poultry px-oasm. The North k v e r Wastewater Plant was recently expanded fiom8 MGD
to 16 MGD, and is currently treating 9.1 MGD of wastewater. Thickened sludge ffom the treatment plant isanaerobically
digested prior to storage in a lagoon or dewatered with a new high solids belt filter press. The previous HRRSA
management programincluded l a n d application of approximately six mdlion gallons annually of liquid biosolids at 4% solids
on numerous farm land application sites. Roclungham County, in which the wastewater facility is located, is one of the
largest poultry producing counties in the country. As a result, land application of poultry manure is common practice. A
Karst d geology canbured with over apPlicatM ofthese manures in some cases created isolated instances of groundwater
nimconamination HRRSA was,therefae,ais0 collcerned about the perception oftheir land application programsadding
to the groundwater contamination problem. During recent years, siting of new land application sites, concerns over
permitting issues, increased monitoring costs, and the potential concerns regarding groundwater nitrate problems all
contributed towards spurring HRRSAs interest in developing another management t e c h q u e such as composting to
supplement land application.
After selecting aerated static pile composting as the method of choice, HRRSA contracted with the enweering
team of EBtA Environmental Consultants, Inc.,Patton Hanis Rust & Associates, and Hazen & Sawyer p.c.for the design
and construction of dewatering and composting facilities. The project was initiated in April 1994. The facility basis of
design consisted of establishing design issues such as biosolids processing capacity, process flows, etc.,as well as the
performance of a dewatering pilot study, a b u g agent survey, a cornposting pild study, and a compost marketing
asscpnnent These tasks were conducted between May 1994 and August 1994. From these work activities, a preliminary
conceitual design was developed and the final design initiated in the Fall of 1994. The design work wascompleted in
Janua~y1995 and six bds wen received from contractors in February 1995 with three bids w i b HRRSAs budget. M e r
selection of Harmon Construction in Hanisonburg as the general contractor, construction commenced in April 1995, and
the facility was substantially completed in December 1995.
One of the key issues in the early planning stages of the project was the selection of appropriate dewatering
equipment. Plate and frame presses. centrifuges, and high solids belt filter presses wereevaluated for replacement of the
existing vacuum filter presses at the North Rlver Plant. Based on operating and maintenance costs, availability of spare
parts, and the use of the existing structures, it was debmined that the most cost-effective means of dewatering would be
thmugh t
k use of a high-sohis belt filter press. Two premiere beltfilter press manufacturers conducted pilot studies in June
1994 at the wastewater plant to determine dewatering performance under actual conditions. From t h ~ sdewatering pilot
it was determined that tbe Ashbrodc High Sohis Belt FilterPress resulted in superior performance. It was determined
through economic analysis that the savings in the capital and 0&M costs of the cornposting operation morethan justified
the dhtional capital cost of a high solids belt filter press being procured on a pre-qualified basis.
study.
Facility Dcrcriptioa .ad Procerr Fbw
Although the design and construction of these facilities included dewatering and composting, this paper will discuss the
cornposting portion of the facility only. The composting facilityis designed to process 5.5 dry tons per day of 25% total
solids digested biosolids cake on a five day per week operating basis. Figure 2 shows the processflow diagram for the
facility. A description of the process flow andequipment features at this facility follows:
Ste Chorecterira'cc- The cuyostmg facility is located on a two acre parcel of land immediately adjacent
to existing digesters and dewatering building at the North k v e r Plant. Muumal site grading and other
preparation activities were required for the collstIuction of the composting facility. All biosolids
receivmg, mixing, caqodmg drying, screening, andcuring and compost storage activitiesoccur under
a 40,000 square foot pre-engineered metal building.
Materials Delivery and Processing - Dewatered biosolids are conveyed ffom the belt filter press to a
concrete storage bunkers in the composting facility. Wood chips aredelivered in dump or live-bottom
trailers for use as the primary b u b g agent. A portion of the wood chips (up tothree operating days)
can be stored under cover with the balance stored outside on an asphalt pad.
63
r
b
-
-
BufkingAgenfs Paper mdl quality wood chips are used as the primary bullung agent and supplemented
with a k
t
e
d mount ofyard waste available fiom the R o c h g h a m County Landfdl. An asphalt storage
pad is provided for storage of new bullung agent as well as recycled bullung agent.
Mixing - Mixing of the b u h g agentswith biosolids occurs in an electrically-dnven 18 cubic yard
capacity batch mixer. The batch mixer is equipped with weigh scales to determineexact quantities of
each ofthe b u h g agents as wet1 as the biosolids used in any given mix. A fiont-endloader is used to
load the batch mixer with the biosolids and the bulking agent. After thoroughly mixing thesematerials,
the initial mix is discharged into a 60 cubic yard capacity three-sided concrete storage bunker,
whch is
also under cover in the composting buildmg.
-
Comprjng Compostlng of the biosolids occurs under cover in a 15,000 square foot area. A fiont-end
loader picks up the mixture fiom the initial mixdischarge bunker and places it in the static pilesin the
cornposting area. The facility is designed to allow a one-foot base of wood chips to be placed over
aeration piping, followed by eight feet of mix, and a one-foot insulative cover of recycled compost.
Canpost p k are approximately 90 feet long. Highdensity polyethylene pipe isused to supply aeration
to the compost piles. Sixteen aeration stations, each capable of providing 630 CFM at eight inches of
water c o l u m n service two high-density polyethylene headers spaced approximately four feet apart. A
custom design hole pattern was used in the design of the aeration laterals to provide uruform aeration
down the length of the compost piles. Each blower station is capable of operating in the induced draft
(negative) or f
d (positive) aeration mode depending on operator preference andthe stage of the
cornposting process. Negative aeration is practiced routinely for the first ten days of the cornposting
process with exhaust gases bemg cdlected and vented directly to an open biofilter for treatment. Blowers
are then switcbedto positive mode forthee
r
m
&of the 2 1d a y cornposting cycle to enhance drying.
The aeration rate delivered to the static p k s is COntroUed based onoperator adjustmentsthrough a central
programmebk logic controller system. Allowance for up to five days of aerated drying isalso provided
in the cornposting buildmg forpenodic times when additional dryingis necessary.
-
is screened through a deck-type screen that has a three-foot
by five-foot rectangular deck with punch plate holes to a %-inch sized product. The screening system
has a capecih/ of40 cubic yards per hour and produces a %-inch minus compost product for curing and
Scrreening After composting, thematerial
use.
Curing Armrion - Aerated curing is provided under cover using portable blower stations and reusable
perforated hgh density polyethylene pipe. " u s area islocated adjacent to the compostingarea and is
d to handle 30 days of screened compost production. Six portable aeration stations areprovided in
the curing area for positive aeration. Cycling timers control aeration rates as necessary in h s stage of
the process. Upon completion of the curingperiod, the compost is moved outside to the storage area for
mmketmg. The paved storagearea provides up to two months capacity for the finished compostproduct.
Odor Corn1 - OQr control at h s composting facility consists of treating process offgas &om the most
odorous cumposting process and treatment through a biofilter system. h t i a l modelling at the facility
imbcated that the nearest receptors, approximately 1
feet fiom the facility, would not be adversely
affected with this type of OQr mtrol approach A 3.150 CFM biofilter has been provided to allow a 60second r
e
s
b
i time of odorous gases in the open bed biofilter system for treatment. Moisture control
is provided through in-line humidification and surface irrigation.
O.OO
Composr Utilization - A compostmarketing
assessment was performed in mid-1994 to determine
potential demand for a compost product. Currently, the Authorityis initiating a program to market the
compost using in-house personnel. Pricing for the compost has not been established,but is anticipated
to be approximately $5 to $8 per cubic yard.
Personnel
Two part-timeoperatocs are ahzed to operate the umpostmgfacility two to thre days per week. These operators
also perform other plant operations such as dewatering, land application of liquid biosolids, and other duties w i b the
wastewater plant operation.
Initid Operation
The HRRSA composting facility beganprocessing bicwolids intemittently in January 1996. Because the North
Rim Plant has a biosolids storage lagoon which is maintained for
the land application program, the Authority could begin
aperationsat the f d t y at a slow controlled pace, thus allowing operators to gain knowledge andcodldence in the process
prix to iKxeesing k d n g to the fachty. Seven individual compost piles have been constructed and 34 dry tons of biosolids
have been composted as of mid-March. The composting process has met PFRP temperature requirements and screened
cunpost is being produced for curing. Odors at the facilityare minimal. Full-time utilization of thebiofilter will begin in
April as loading to the facility increases.
COSTS
Comparing costs for both facilities is a very interestingexercise. Economies of scale play an important factor in
the construction and operating costs of compostingfacilities. However, whencomparing the costs of these two facilities,
one should be co-t
of the basic differences in facility design which have the greatest impact on costs. The basic
differences in the two facilities are summarized belowby unit process for those which are impacted.
SHmOrk
The Davenport Facilityincludes cost of appmximately $400,0oO for installation of a flood protection
levee.
The Davenport facility includesa yard wastereceiving area and gnnding equipment.
The Davenportfacility includestwo 50 cubic yard capacity biosolids bins and two 15 cubic yard
capacity b u h g agent bins with variable speed outfeed devices. Two pugmills are used to mix
biosolids and bullung agent on a continuous basis. A weigh belt isused to weigh materials and to
eubmatically adjust feed rates through a PC controller. HRRSA facility mixing system includes one
18 cubic yard capacity batch mixer with weigh
scales to measurebulking agent to biosolids ratios.
CompootiagA e r a t h
The Davenport facility includes in-trench aeration, whereas HRRSA utilizes above ground high
density polyethylene pipe. Davenport has pile temperature feedback to provide aeration rate
adjustments. HRRSA has manualeeration rate adjustments through a central PLC system.
Enchuurts
The mixing, composting, and drymg processes are totally enclosed in insulated pre-engineered
buildings at the Davenport facility. These processes are only covered at HRRSA.
Odor Control
The Davenport facility collects all offgases fiom mixing, composting, and drying processes and
budding air for treabnent through biofilhration HRRSA facilitytreats exhaust gases fiomcomposting
piles when in negative aeration throughbiofiltration.
Bbrdidr Cake
The Davenport facility design was based on20% total solids, whereas the HRRSA facility design
was based on 25% total solids. This single factor increases the facility capacity by approximately
o n e - h d more biosolids ona dry weight basis because less volumes are managed per dry ton.
66
CAPITAL COSTS
Thecctpital costs reported are in 1995 dollars and include all moving stock, stationary equipment, buildings, site
improvements, engineering, p t t i n g , and construction management. The cost of land acquisition is not included.
The Davenport and HRRSA cornposting facility capital costs are summanzed in Table 1. Capital costs for
Davenport are shown as is and then withthe deletion of the flood protection levee and the yard waste receivingprocessing
for comparison with HRRSA This c
o
m
p
hshows that the large capacity totally enclosed aerated static pilecomposting
facility at Davenport has a similar unit cost of $275,000per dry ton of biosolids capacity as the smaller HRRSA facility
i
s simply housed under covm. It should be noted that because of the higher solids content in the dewatered biosolids
at HRRSA, a third more bioeolids capacity on a dry weight basis is available at HRRSA, thereby redwing the resultant unit
costs per dry or wet ton of biosolids capacity.
Tabk 1
COMPARISON OF CAPITAL COSTS
I
Jhvcnport'
TotdC.pit.lCort'
million
S8.61
I
H RRSA'
SI31 million
-paDryTonpaD.YofC.prcity
S307.400
S274,JOO
Cc&paWdTonpcrD.yofc.p.city
S61.500
S68,600
A4urlalCut'paDryTonpaD.yofC.p.crty
S27J.400
S274,JOO
SJJ,100
S68.600
(
- ,
O&M COSTS
0 & M costs for the two facilities are compared in Table 2. The 0&M costs at Davenport are based on actual
agerating data for the first six months ofoperation. These costs i n c l u d e yard waste processing. The quantity of biosolids
processed on average is only 21.3dry tons per actual operating day. The 2,339 dry tons of biosolids processed over that
period compares toa design quantity of3,640 dry tons which translates to 64%of facility capacity. Thls lower thruput is
due to start-up/shakedown of the system and loadingloperationalproblems at the WWTP which resulted in much wetter
biosolids cake during November through February (1 3% to 17%) as compared to the 19% to 2PATS whch was being
acheved in September and October.
0&M costs for HRRSA are estimated based onprojections since no historical data is yet available. HRRSA is
designed to operate only three days per week in the initialdesign year (1 9%). However, because of start-up/shakedown,
the facilityhas not been operated at thattype of schedule as of yet.
Labor accounts for the largest percentage of O&M costs at both facilities at roughly one-hrd of the budget.
Typically, b h g agent costs are the next largest portion which is also true at the HRRSA facility. However, Davenport's
bullung agent costs are greatly reducedby using shredded rubber tires and yard wastes to supplement newwood chips as
the bullung agents. Utilities at Davenport are a higher percentage of theO&M cost due to the large amountof a d o w which
is collected for treatment through the biofilter system. Maintenance costs at both facilities are projectedbased on hourly
costs and operating costs and hourly run times for moving stock andstationary equipment. Fuel is based on actual usage
at Davenport to operatethe fiont-end loaders and yard wastegrinder. Mmellaneous includes product monitoring.
67
c
Table 2
COMPARISON OF O&M COSTS
k
*/;
$/Dry Ton of BloaoUdr
$/Dry Ton of BioaoUds
ofTd.l
I
% of Total
33.19
34.9
28.0
9.46
10.0
18.6
11.64
12.2
49.74
36.1
Utilitia
38.47
M.in(aunce
25.65
wIbg
16.67
12.1
Y d Waste Tip F a Revmud
N d O&M Cod
39.76
97.95
conport Rcvmue'
28.57
-
33.51
-
Net O&M C
oda'
69.38
-
61.56
-
Labor
h
HRRSA'
Dmvcnport'
CkwOry
31.2
29.68
'&scdon fint rix month of @
o
nand 4costa to poceg 2,339 dry tom of biosolids and yard wastes.
Notes:
on
p
r
o
w fintyear qurntityof 940 dry tom of bioeolih.
'
B
r
e
e
don first ten m
o
n
hof y d wade nvmuca adjusted for six months.
.
' A d j d O&M ant .Aay d waste revenuca.
' A d j d O&M ant bucd on atimrtsd compd produ&on at both ficilitia d $5 per cubic y u d nlcs revenue.
08tM~areeshmatedtobeS95perdrytonofbiosolids~ssedatHRRSAandS138perdrytonofbiosolids
procesd at Davenport. F i p 3 shows the relative cost impact of these costs categories. Actual O&M costs at Davenport
W
deaease
III
as the dewatered bimlicis cake sol& content continues to improve. These costs compare very favorably with
other operating biosolids cornposting facilities nationwide.
ANNUALIZED COSTS
Total a
n
n
-
costs for both facilities are compared in Table3. The capital costs were amortized at 5% interest
as follows:
b
b
Moving stock at 7 years
Stationary equipment
at 10 years
Structures,sitework, and engineering at 20 years
Table 3
COMPARISON OF ANNUAL COSTS
HRRSA'
247.12
Notes:
60.77
199,170
211.88
'Bascd on first six months of operation and actual costs to process 2,339 dry tons of biosolids and yard wastes.
B a d on projected first yearquantity of 940 dry tons of biosolids.
'Bad on first ten months of yard waste revenues adjustcd forsix months.
'Adjusted OBtM cost after yard waste tip fee revenw.
52.97
I
4u)9
0
0
E
0
0
0
- - -0
0
0
0
0
0
0
0
0
0
* c 9 w - o c n o o b < D r r , d - c 9 o J -
i1
0
0
Yard waste tip feerevenues 8ce accounted for at Davenport. Compost revenues of $5 per cubic yard are assumed
at bothfacilities based on preliminary market investigations and reported revenues from other
similar facilities.
CONCLUSIONS
As th~spaper illustrates, two s w x s f u l aerated static pile biosolids composting facilities began operation in the
United States in 1995. The larger capacity facilityin Davenport, Iowa uses a totally enclosed approach for environmental
and odor control n y s o n s . The smaller facility in Harrisonburg, Virgha utilizes a covered aerated static pile method of
composting. Both facilities utilize the popular aerated static pile method of cornpostingas well as unique process control
featcaes that have a proven track record at other facilities. Many of these most recent features have been incorporated into
these f d t i e s based on owner prefaence and the budgetary c o n s t r a i n t s . Odor control at both facilities has been completely
s a h s f a c b y . The facilitieswere built within budgetaq c
onstraints,while at thesame time incorporating the most important
owner4esiralf
m possible. Cod camperiscms p
r
o
v
w
e
d
l here show that cost-effectivecomposting can be achieved using
aerated static pile with a high degree of odor removal efficiencyand varying characteristics of the feedstock biosolids and
b u h g agents available.
About the Autkors:
Todd Williams, P.E.. is a senior engineer for E&A Environmental Consultants, Inc.
in C w , North Carvlim. R.Allen Boyette. P.E., is an engineer with the same. Eliot Epstein, Ph.D.is President of E&A
Environmental Consultants,Inc. at the main oflce in Canton, Massachusetts. Scott Plett is the C i v of Davenport's
Composting Faciliv Manager. Curtis Poe, P.E., is the Erecutive Director ofthe Hamsonburg-Rockmgham Regional
Sewer Authoriw in Mount Cnnvforri, Mrginia Inquiries tvgardmg this paper should
be directed to Todd Williams 91
at9460.6266.
70
AGITATED BIN COMPOSTING, START-UP AND OPERATION
Patrick D. Byers
Assistant Director
Compost & Vegetation Processing Services
Solid Waste Authority ofPalm Beach County, Florida
INTRODUCTION
The transition 6om a plot facility to a full-scale plant in Palm Beach County, Floridahas been relatively smooth.
The primary challenges are plastics removal and marketdevelopment for the finished compost.
The Solid Waste Authority of Palm Beach County
(SWA), Florida took a "testing the waters" approach to
compostlng biosolids and yard trimmings.The Authority was faced with a Florida ban on yardtrimmings disposal and the
need to find alternativesto landfilling biosolids. in 1991, it began operating a 2.3 dry todday agitated bay facility, with the
idea of expanding capacity to process about 120,OO tondyear of material. Success with the pilotplant led the Authority to
move faward with a larger facility.
Expansion of the SecondNature Compost Facility (SNCF), the name of the Authority's plant, proceeded rather
hmoothly. Eight bays were added to the four in the original compost building and a new building that houses 24 bays was
constructed, malung the facility the
largest agitated bed compost plant utilizing the Wheelabrator Clean
Water Systems (IPS)
technology. Operations commencedon October 1, 1994. The facility now accepts wastewater residuals generated by Palm
Beach County and the City of West Palm Beach and Seacoast Utilities. The SWA owns and operates the SNCF. It is
responsible for the management and disposal of solid waste
in Palm Beach County, whichhas a population of approximately
one million people.
COMPOST FEEDSTOCK
The Authority nowaccepts approximately 120,OO tons per year of raw yard tnmmings. Since plastic bags are still
allowed in SWAs yard tnmmings collection program, a rather extensive presorting process is necessary. Yard trimmings
are delivered fromfive SWA transfer facilitiesby 100-yard walking floortrailers or via other various types of commercial
trucks. Because loads get combinedat the @ d e rstations, incoming materialis a mix of bagged yard trimmings, and brush
and wood ofvarying size. M e r being unloaded in a receiving area, materials are separated into two fractions: clean yard
tnmmjngs for composting and contaminated stream for fuel production. Acombination of mechanical and hand sortingis
utihed to remove pieces of plastic and other debris. About 90 percent of the contaminants are removed prior to grinding.
Once the yardtnmrmngs presort is completed, a contractor grinds the cleans materialtwice in standard tub pnders.
The ground mulch is fed directly into a trommel screen with 1 1/4" screens. The 1 1/4" minus product is sent to the compost
fachty and 1 1/4" plus is sold forhel. The screened mulchenhances the compost facility capacity not only by using up more
yard trimmings, but also by increasing the ability to accept more biosolids. The double ground yard tnmmings are
transported to the compost facility in 100 cubic yard walking floor trailers (same as the transfer facility trailers) and
discharged onto the tip
floor area. Approximatelythree days ofcovered storage is available forground mulch at the compost
facility.
The wastewater residualsdelivered to the SNCF average about 13 percent dry solids andare dewatered with belt
presses. The City of West Palm Beach, which supplied approximately 75 percent of the biosolids delivered in fiscal year
1994/1995, is presently undergoing an expansion of its 40 million gallon per day (MGD) wastewater treatment plant
71
(WWTP) to 55 MGD by Ilecember, 1996. During this espansion, the city has taken the opportunity to enhance its
dewatenng operation andespects to increase wastewater residuals dewateringcapabilities from 13 percent dry solids to an
average of 18 to 22 percent. This will allow the city toreduce the amount of wet tons delivered to the compost facility,
thereby reducingthe need for furher expmsion of the compost facility and composting equipment. Significant
compost cost
savings will occurby investing in equipment capable of producing ah e r biosolids cake.
All wastewater residuals are delivered to the compost facility in 30 yard tractor trailers that utilize dump type
The trucks back up to an elevated tipping platform
to discharge loads over two
a foot wall and downonto the tipping
floor, which has approximately two days of storage capacity.Operators works kom 5:30 a.m. to 5:30 p.m.; the goal is to
load all mixed biosolids and yard tnmmings into the bays during thesame work day. On occasion, two or three loads of
biosolids may remain on the tipping floor overnight, which
has not created odor problems.
bodies.
Ncxq to the tipplng floor1s the mixing area where the yard
tnmmings and biosolids are combined to produce the
feedstock mixme. Two stabonary batch mixers capable of handling approximately 16cubic yards of material ata time stand
slde by side. A weight sensor, which measures the net weight of the material fed into the mixer,
enables operators to tailor
rmx feedstocks. Tpically, the operatormixes a 50.50 (by weight) yardtnmmingshiosolids combination in the batch miser
to ob- a targeted final mixme dry solids content of 38 percent. Controlling the moisturein the mixing process is crucial
to maintruIllng optmum composting conditionsin the reactors. Carehl testing of the dry solids content and bulk densityof
all feedstock components1s so Importmt that the proper mixture ratiosare calculated and adheredto. Mistakes made at this
point cahaffect the compostmg process and the quality of end
products, possibly resulting in increased costs and timespent
troubleshootlng.
COMPOSTING PROCESS
Once the feedstock mising is completed, the material discharges from the batch mixer
onto a stacking conveyor
and into a small stockpile. The feedstock inventoryis individually fed intoone of the 36 compost reactors through the use
of a shd steer-type loader. The compost facility was designed so that 14 to 28 cubic yards could be added to each of the 36
reactors ona dady basis. The exact amount is based on the quantity of biosolids delivered
each day to the compost facility
by the generators. The SNCF has a designed wastewater residuals daily peak capacity of 220 wet tons with an annual
capacity of upto 60,000 wet tons.
Each of the 36 composting reactors are separated into six aerationzones. They vary in length, with shorterzones
toward the mixing end where the composting process is initiated. Each
zone of each reactor is designated a single
temperature sensor anda single aeration blowerto allow individual temperature control and aeration.
The zones are always
designated with lettersb e m g with " A and increasing through the alphabet from the mixing end toward
the finished end.
Process control includes continuoustemperature monitoring and automatic controlof the aeration system.
There are three agitators in the 12 bay building, and six agitators in the 24 bay building. The bays are equipped
with a transfer dolly formoving the agitator from one reactor to the
nest. There is approximately a 38 percent reduction in
weight during thecomposting process as a result of decomposition and moisture drivenoff by elevated temperature in the
reactors.
ODOR CONTROL SYSTEM
The compost facllity utilizes three separate 12,000 square foot biofilters, each servicing 12 reactors. The media
consists of a four foot deep mlsture of 50 % southern pinechip and 50 % southern pine mulch, withsix inches to one foot
of southern pine mulch on top
to optlrmze moisture conditions. The composting system isequipped with aneshaust system
that ventilates the interiorof the enclosed compost building. It maintains negative airpressure within the building, which
includes the tipping floor, feedstock mixing
area, composting reactors, andcompost discharge area.
72
Twelve 60 horsepower fans control the supply of odorous air from the compost facility to the biofilters. Each
ventdation bloweralso can dscharge to the atmosphere directly. The discharge path is controlled with a manually operated
damper. The two speed blower motors are capable of
operating at high speed ( 16,000 cu. A./min.)when discharging to the
biofilter and at low speed ( 12,000 cu. A./min.) when discharging directly to theatmosphere. (The resistance to air flow
through the biofilter requlres more discharge pressure and, thus, a higher speed.) The normal path of ventilation air is
through the blowersto the biofilter. Discharge to the atmosphere is limited to theevening when there is little or no odor in
the building. Air is discharged through a stack that is the same height of the building. Operators also may open up the
bddmgs doors in the evening to allow heatto dissipate. The SNCF is bordered on the east side by a landfill (after which
the nearest neighboris a half-mile away) andon the west side by a county road thatis 400 feet away, after which there is no
development for approximately sevenmiles.
An acceptance test was performed on the biofilters during
start-up. The biofilters collectively achieved a dlscharge
mnmtratlon average of 10 ddutlons to threshold (ED 50) and a butanol intensityaverage of 1.4. The biofilter is regularly
monitored to maintamproper operating conditions. Addition of wateris necessary, particularly during summer months. The
amount of water addition requlred fluctuates depending on conditions both within and
outside the compost building.
In addition to the blofilter and atmospheric dilution,SNCF operators follow specific guidelines to reduce odors.
Uncomposted blosolids or mixture of biosolids and amendment cannot sit for prolonged periods without agitation and
controlled aeration. Uniform aeration is important, with temperatures not allowed to consistently rise to above 65C. In
addition, reactors are agitated and aerated on a consistent schedule, because rapid swings in compost aeration and
temperature can resultin the release ofexcessive odors. Pools of water should not sit on the floor
or aisles. The mainfloor
and mixing equipment are cleaned regularly.Other practices involve maintenanceof proper moisture levels in the compost
and thorough mixingof the feedstock mixture.
PRODUCT QUALITY
The compost mix remains in the bays for a minimum of 14 days, and duringsummer
the
retention may be as long
as 2 1 days. The SNCF does not have a curing area, but because of product storage, compost remains on site for an average
of two months (and sometunesas long as four months). Finished compost is tested for pathogens, vector attraction reduction
and stability. The compost meets the U.S. EPA Part 503 and Florida Department of Environmental Protection standards
for unlimited distnbution. Stability, monitored with carbon dioxide respiration testing,shows a stable tovery stable rating
upon discharge from the bays. Stability tests on product when it actually is distributed
show similar results.
Finished compost IS stored in "blocks" that are50 feet by 100 feet and about 15 feet in height. The piles continue
to have elevated temperatures and dry solids content remains steady because less surface area is exposed to moisture.
A&tlonal testing is done on the stockpiled material for fecal coliform, salmonella, helminth
ova and enteric viruses; there
have not been problems with regrowth (attributed primarily to the uniform
temperature). Stockpiling in the block formation
can, however, cause the matenal to become anaerobic. Therefore operators turn the pile two tothree days before product
distnbution to release ammonia.
F
I
E
SECOND NATURE COMPOST FACILITY
FISCAL YEAR 1994-1995 ANNUAL SUMMARY
MONTH
FEE.
OCT.
(1)YARDWASTE RECEIVED
JAN.
DEC.
NOV.
4425 1
4268 1
5141 1
7
44770
(2) YARDWASTE
( X SOLIDS)
496
528
531
532
576
626
656
( J ) SLUDGERECEIVED
(WET TONS)
2774 4
3138 0
4091 9
4753 8
4301 8
5248 3
5
127
123
124
129
129
132
3523
3860
5086
6132
5549
44637
4591 8
(7) PROCESSED COMPOST
(X SOLIDS)
481
480
506
494
( 8 ) PROCESSED COMPOST
(DRY TONS)
2147 0
2204 1
2897 2
3086 8
2352
2157
JULY
5324
3936 4
JUNE
MAY
3692
35602
1
4527
54538
0
43603
APR.
-
MAR.
AVG. SEPT.
TOTAL
AUG.
4103 1
4439 1
53268 8
(WET TONS)
(4) SLUDGE
626
682
553
493
514
568
46554
4419
4015 9
42170
3713 2
3840 1
40974
133
134
130
12.9
115
120
127
6909
5878
6238
522 1
541 9
427 1
4586
522 3
62673
57245 €6353
54428
53269
49474 5421 3
47789
49132
50053
5291
6
634998
552
497
49169 3
(X SOLIDS)
(6) SLUDGE
(DRY TONS)
62487
(WET TONS)
IS) COMP. O.S.I. DISTRIBUTED
510
566
555
559
564
2693 4
3274
6107
4564
25000
MOO
16468
7249
29746
475
520
2981
29794
6
27974
2377
5 244336826
8
275562776433067 1
8701
9431
17802
10746
128952
21103
2905 4
290540
(WET TONS)
IO) COMP. AUTHORITY USED
8000
40500
45000 42000
loo00 8000
56790
50250
(WET TONS)
11) 051. COMP. INMNTORY
(WET TONS)
36922
154067
75173
148483
119854 231998
(I)
Monthly total, compost faclllty yardwash foodstock
146825
190858
149740 136068
177938
165065
197284
(6) Monthly total, comport facllltydischarge (XI plusX31 tlmes 0.62
( 7 ) Monthly average, ProCesMd compoM percent dry rollds
(81 Monthly total, comport faclllty processed compost
(X6 tlmes 17)
(9) Compost Organlc SupplementsInc. has dlstrlbuted
(2) Monthly avenge. yardwastepercent dry solld
(I)Monthly total, compost facillty sludge feedstock
(4) Monthly avenge, sludg. percent dry solids
(6) Mo(0nthlytotal, compost facilltyahrdg. fowhtock (XJ times x4)
(IO) Compost uttllzedb y the Solld Waste Authority
(11) Organlc Supplements Inc. P~M
~II
compost inventory
COMPOST FACILITY PRODUDUCTION
7000.0
OCT.
NOV.
DEC.
JAN.
FEB.
MAR.
APR.
"
~
MAY
JUNE
__
~
JULY
AUG.
SEPT
.
COMPOST MARKETING PROGRAM
-
25000.0
g
vl
20000.0
15000.0
t; lowo.o
5000.0
0.0
JAN,
~~~~~
L d l
DEC. NOV. OCT.
FEE. APR. MAR.
JUNE MAY
JULYSEPT. AUG.
~~
(9) COMP. O.S.I. DISTRIEUTED
~
~
~
~
~~~
O(IO) COMP. AUMORIM
~
~~
~
~
USED
o(11) O.S.I. COMP. INVENTORY
~
"
.
WASTELYATER RESIDUALS MANAGEMENT
FISCAL YEAR TO DATE FY94B5
PROCESSING COST SUMMARY
ACCTl
51222
51301
51400
51401
52100
52200
52300
52400
52500
52600
TOTAL
ACCOUNT TITLE
REGULAR SALARIES a WAGES
-OTHER SALARIES AND WAGES
REGULAR OVERTIME
OTHER OVERTIME
FICA TAXES
RETIREMENT CONTRIBUTIONS
LIFE HEALTH, DISABILITY INSURANCE
WORKERS COMPENSATION
UNEMPLOYMENT COMPENSATION
ACCRUED SICK a ANNUAL
53403
53405
53406
54001
54002
54101
54301
54302
54403
54501
54601
54602
54603
54604
54605
54606
54607
54608
54609
55101
54701
54901
55103
55p01
55202
55203
55205
55206
55208
55209
55210
55304
55401
55402
59962
59965
ENVIRONMENTAL MONITORING
CONTRACT PERSONAL SVCS
OTHER CONTRACTUAL SVCS
TRAVEL CLASS A a B
TRAVEL CLASS C
TELEPHONE
ELECTRICITY
WATER AND SEWERAGE
EQUIPMENT RENTAL
INSURANCE PREMIUMS
RIMaFFICE EQUIPMENT
R/"FACILITIES 6 STA EQPT
Rh-MOBILE EQUIPMENT
RIM-TIRES
RIM-MISCELLANEOUS
RIM-RADIO EQUIPMENT
RIM-GROUNDS
R/M-UTILITY SYSTEMS
R/M COMPOST SYSTEMS
OFFICE SUPPLIES
PRINTING AND REPRODUCTION
LICENSES AND PERMITS
PHOTO SUPPLIES6 DEVELOP
GASOLINE
DIESEL FUEL
OIL a LUBE
TIRES, TUBES, ETC
MINOR EQUIPMENT
SAFETY EQUIPMENT
OTHER SUPPLIES
UNIFORMS
OTHER MATERIALS
BOOKSPUEUMEMBERSHIPS
EDUCATIONAL EXPENSES
MOBILE EQUIPMENTLABOR EXPENSE
GROUNDS MAlNT LABOR EXPENSE
$1.304
BUDGET FY94/95
$412.196 19
$19 600 00
$44 318 19
$200000
$35 810 72
$82 668 96
$0 00
$0 00
$954 35
$6,073 14
jhC3.621.55
PERS3NNEL S E R V I C E S
59966
F A C l l l T Y hlAlNT LABOR EXPEliSE
59960
TOTAL
ADMINISTRATION EXPENSE
OPERATING EXPENSES
$13.50000
$0 00
$20,000 00
$903 00
$250 00
$850 00
$175,700 00
$10,426 00
$6.426 00
$23.13900
$1.40000
$17 50000
$38.569 00
5400 00
$4.000 00
$3 300 00
$0 00
$200 00
$168.029 00
13.900 00
$1.50000
$500 00
$275 00
$2.500 00
$40.000 00
$12.46000
$10,10000
$17.856 00
$5.139 00
110.282 00
$7 300 00
$6.926 00
$1.10000
$2.300 00
$67,950 00
$0 00
EXPENSE
FY94/95
$388.352 58
$17.314 36
$42.649 55
49
1695
$35,145 68
$74,900 69
(560.790
47
560.790
1102.778 84
$452 00
$18.706 05
BALAf
$23 843
52.285
$1 668
$665
17.768
($102 778
1602
.
(512.632
($138.164
~"
5741,785.71
f10.13025
$0 00
$5.32602
$902 13
$226 20
$338 10
$197.330 87
$9,959 53
$50 00
$7,348 00
$0 00
43
$5,531
$36.897 66
$360 00
13.941
$58 30
$1 894 97
$200 00
$121 00
$88,726 67
$1.05806
$934 35
$100 00
$251 63
$2,090 16
15 $22.938
$12,636 74
flO,M16 73
$10,935 80
$2,31662
$9.961 35
$5.303 50
$1.482 42
58
5624 20
$690 00 61000
$74,435 01
$0 00
so
so
w
so 00
$0 00
IO
Iow
5o.00
Io00
$3.369
$14.673
$0
$23 81
$511 4
($21,630 8
$466 4
16.376 M
$15 791 01
400a $1
$11 968 5 ;
$1.671 3'
$40 o(
7(
$ I ,405 0:
(5200 M.
$79 M.
$79,302 3?
$2.841 94
$565 65
$400
$23 37
$409 84
$17061 85
($176 74
$13 27
$6.920 20
$2 822 38
$320 65
50
$ 1 996
$5.443
$475 80
$1
($6485 01
$674.680 00
$521,245 85
$1,278.301 55
$1,263,031 56
R53403 ENVIRONMENTAL
MONITORING
R53406 OTHER CONTRACTURALSERVICES
R54608RIMUTILITYSYSTEMS
R55304 OTHER MATERIALS
1975
539,000
$615
19.350
1975
50
$615
59.350
so 00
5 3 9 . m 00
$0 00
$0 00
TOTAL
ADDITIONAL
ENCUMBERED
EXPENSES
$49,940
510.940
s 3 9 . m 00
TOTAL
I
PERSONNEL 8 OPERATING EXPENSE
$153.434 15
99
$15,269
ADDITIONAL ENCUMBERED EXPENSES
STATISTICAL INFORMATION
TOTAL
OPERATING
EXPENSES
TOTAL
CAPITOL
DEPRECIATION
EXPENSE
$1 273.971 96
$1.007.706 44
TOTALCAPITALANDOPERATINGEXPENSES
$2,281,678 40
49,169 30
53.268 80
102 438 10
WASTEWATER WET TONNAGE PROCESSED
YARDWASTE WET TONNAGE PROCESSED
TOTAL
TONNAGEPROCESSED
OVERALL COST PER WET TON PROCESSED
OVERALL COSTPER WET TON WASTEWATERF
OVERALL COST PER DRY TON WASTEWATERR
(AT 12 7% DRY SOLIDS)
TOTAL
WASTEWATER
YARDAGE
PROCESSED
TOTAL
YARDWASTE
YARDAGE
PROCESSED
TOTAL
COMBINED
YARDAGE
PROCESSED
PERCENTAGE OF WASTEWATER RESIDUALS B'
PERCENTAGE OF YARDWASTEBY WEIGHT
3UALS PROCESSED
N A L S PROCESSED
GOLBSNARD
OLBSNARD
$22 27
$46 40
$365 39
65,559 07
193.704 73
259.263.79
FIGHT
48%
52%
CALCULATION OF WASTEWATER RESIDUALS GENERATC
rlPPlNG FEE
TOTALFISCAL
YEAR 94/95EXPENDITURES
INTERLOCAL AGREEMENT PROJECTEDMAXIM1
ONNAGE OF WASTEWATER RESIDUALS (12%DRYSOLIDS)
OPERATING COSTPER DRY TON WASTEWATEf
OPERATING COST PER WET TON WASTEWATE
TIPPING FEE CALCULATION
SIDUALS PROCESSEDAT 12 7% DRY SOLIDS
ESIDUALS
OR WASTEWATER GENERATORS (57% OF COST)
75
$1 273,971 96
59,143 00
$204 02
$21 54
$12 28
FISCAL YEAR 1995-1996 ANNUAL SUMMARY
MONTH
NOV
OCT
DEC
JAN.
]
FEE.
I
u09.75
(1) YARDWASTE RECENED
1
4.002
3,903
I
538
570
4.755
MAR.
APR.
5 160
4,125
3,763
MAY
JUNE
JULY
AUG.
4,367
5,333
4.618
651
09
1
604
4.275
5.747
SEPT
AVG.
TOTAL
4,447
40,026
(WET TONS)
(2) YARDWASTE
577
~
61.9
600
558
57 6
1% SOLlDSl
3,756
13) SLUDGE RECENED
3.409
5.321
5,542
5,143
4.26941.356
3.895 4.595
(WET TONS)
12.8
14) SLUDGE
12.9
13.1 12 913 0
0
12.5 12 1 2 7
12
9
13.9
1% SOLIDS)
561
151 SLUDGE
668 480
503
666
440
589
593
731
5,305
664
(DRY TONS)
6,137
16) PROCESSED COMPOST
5.204
4.748
4,749
50,457
4.595
5.606
5.358
(WET TONS)
0
i
54 3 54 86 0 4
51 5 48.6 53
0
51.7
53 8 54 3 56
1% SOLIDS)
10) PROCESSED COMPOST
2,850
2.445
1.478
1.061
3.186
2,435
2,310
3.847 3,332
4,010
3,036
27,323
2,907
(DRY TONS)
I¶)COMP. 0.5.1. DISTRIBUTED
839
773
5.690
8.221
2.431
1,450
2.239
1,482
1.588
13.340
1.482
(WET TONS)
12
(0) C W P . SWA DISTRIBUTED
5,395
4.7281
5.121
5,573
4,788
- W E T TONS)
8.996
1 1 ) O.S.I. COMP. INVENTORY
9.568
10,705
9,972
12.413
10.183
5.421 9.360
8,553
16.658
(WET TONS)
(7) Monthly a n n p e . processed compost prcmnt dry solids
( I )Monthly toUI. compost facility processed cmnpost(#6 lunes #TI
(9) Compost Orpane S v p p l m n u Inc. h ~ distributed
s
(lo) Cornpoft Ytnlozed by fhe Solid Wade Authorily
(1) Monthly IouI. compost facvl#ty yardwale feedstock
(2) Monthly a n r a p . yardwaste prconl dry solid
(1)Monthly Ioul. compost fac8loty sludp. laedstock
(4) Monthly awnge, s l u d p p r c e n l d rsollds
y
(5) Monthly totll. Compost 1aCllity sludge fndstock [#IIlmcS I I )
(L)Monthly t o u t compost faclllhl doschaqe 111 plus #I) 11ms0.62
ocr
NOV
OEC
JAN
(l1)lnventory- #ll*I~HO-#Y-ownfrmnscmn
((2) Includes dephlmn of tha Dyer stockpile. (5,000 TONS)
FEI
MAR
APR
76
MAY
JUNE
JULY
AUG
SEPT
50,1534.000
7.478
4,731
6.869
6.16
WASTEWATER RESIDUALS MANAGEMENT
FISCAL YEAR TO DATE FY95/96
PROCESSING COST ANALYSIS AS OF JULY 1 1996
.CCT#
1222
1301
1400
1401
2100
2200
2300
2400
2500
2600
OTAL
ACCOUNT TITLE
REGULAR SALARIES a WAGES
OTHER SALARIES AND WAGES
REGULAR OVERTIME
OTHER OVERTIME
FICA TAXES
HEALTH INSURANCE
ACCRUED SICK a ANNUAL
PERSONNEL SERVICES
3403
3405
3406
4001
4002
4101
4301
4302
4403
4501
601
0602
4603
OTHERCONTRACTUALSVCS
TRAVEL CLASS A a B
TRAVEL CLASS C
TELEPHONE
ELECTRICITY
WATER AND SEWERAGE
EQUIPMENT RENTAL
INSURANCE PREMIUMS
R/M-OFFICE EQUIPMENT
R/M-FACILITIES 8 STA EOPT
RIM-MOBILE EQUIPMENT
R/M-TIRES
RIM-MISCELLANEOUS
R/M-RADIO EQUIPMENT
RIM-GROUNDS
RIM-UTILITY SYSTEMS
RIM COMPOST SYSTEMS
OFFICE SUPPLIES
PHOTO SUPPLIES a DEVELOP
GASOLINE
DIESEL FUEL
OIL a LUBE
TIRES. TUBES, ETC
MINOR EQUIPMENT
SAFETY EQUIPMENT
OTHER SUPPLIES
UNIFORMS
OTHER MATERIALS
BOOKS/PUBUMEMBERSHIPS
MOBILE EQUIPMENT LABOR EXPENSE
GROUNDS M I N T LABOR EXPENSE
FACILITY MAlNT LABOR EXPENSE
OPERATING EXPENSES
4604
4605
6606
4607
#608
4609
5101
4701
4901
5103
5201
5202
5203
5205
5206
5208
5209
5210
5304
5401
5402
)962
3965
3%6
B60
3TAL
3TAL
BUDGET FY94I95
$441 682 17
$3 155 60
126
$49
66
$502 40
$41 004 52
$94 225 50
so 00
so 00
$1,348 04
$12.036 28
t643.081 17
S13.8Nl00
$0 00
$15.000 00
$0 00
$154 00
$4.920 00
EXPENSE
$317,633 66
154
93
80
118.659 83
$501 90
$25,469 21
$59.933 89
$37,620 00
$58,348 71
$1.34804
90 00
$522,670 04
so 80
$30,466 83
$0 50
$15.535 31
$34 291 61
($37,620 0
($58,348 7
$0 00
t12.036.2B
$120,411 13
$7,395 00
$0 00
$5.245 17
so 00
$122 90
$805 52
$123.000 00
$5,533 15
$0 00
$17,369 00
PO 00
$24,916 17
$65,961 66
$0 00
$1,081 00
$1 024 61
$0 00
$6,405 01D
$0 M3
$9,754 8:3
SO MI
$27 1(I
$4.11441I
($123,000 M
$0 00
$0 00
$215,982 00
$1.539 00
$1.15000
9124.389 44
$785 16
9515 76
so 00
$000
$1,720 72
$18.864 22
$8.358 74
$8,352 14
$9 142 51
$1,713 00
54,587 31
$4,376 10
$53 74
$550 00
$87,363 19
$0 00
so 00
SO oc
$91.592 56
5753 84
$634 24
$0 00
$126 00
$1,694 28
$5,605 78
$5,785 26
$9.327 86
95.207 49
$5,867 00
$2,992 69
$1,739 90
59.522 26
$497 10
$1,050 00
($18,939 19I
$0 00
SO 00
$547.308 00
$524.029 11
$23.278 89
91,190,389 17
$1.046699 15
$143.690 02
$1,675 00
$7,124 75
91 1,62484
$000
$899 60
$11,624 84
$1.675 00
15 $6 225
$0
$0 00
$672 50
so00
$11,40000
$196 00
$0 00
$1,400 00
$25,000 00
$76.470 00
$0 00
$2.000 00
$1,940 00
$0 00
so00
$126 00
$3,415 00
$24,470 00
$14,144 00
$17,680 00
$14.350 00
$7,580 00
$7.580 00
$6,11600
$9,576 00
91,300 00
$1,600 00
$6&424 00
$0 00
so00
$802.90
IOw
so00
PERSONNELaOPERATlNGEXPENSE
BALANCE
FY94/95
16124,048 51
$5,8668!5
$196 CK1
(517.369 CK
S1.4WCK
$83 8:i
510,508 34I
$0 ocI
$919 ocI
$915 35I
so ocI
IOM)
ADDITIONAL ENCUMBERED EXPENSES
OTHER CONTRACTURAL SERVICES
RIM FACILITIES ANS STA EQPT
RIM UTILITY SYSTEMS
RIM COMPOST SYSTEMS
MINOR EGUIPMENT
OTHER MATERIALS
3TAL
ADDITIONAL
ENCUMBERED
EXPENSES
XPENSES
YEARTODATEEXPENSESUMMARY
COST FOR LANFILLING A PORTION OF
40
$2,060
$000
$26.297 00
w
so00
$0 00
sow
$49.454 49
$40,881 84
$8,572 65
STEWATERRESIDUALSRECEIV
$1,087,58099
$74 921 85
YEARTODATEEXPENSESUMMARY
EVENUE
uI00
$26,969 50
$2.060 40
$0 00
$1.162.502 84
FIXEDREVENUE
ASSET
TIPPING FEE REVENUE
CAPACllY EXCEDENCE REVENUE
COMPOST SALES REVENUE SUMMAR)
5635.445.00
$588,699 94
$332.073 50
$13,340 00
YEARTODATEREVENUESUMMARY
$1,569,558 44
EAR TO DATE
PROFIT OR LOSS
PERCENTAGE OF PROFIT VS EXPENS
$407.055.59
37 43%
TOTAL TONNAGE WASTEWATER RESIDUALS DELIVERED TO THE AUTHORITY
TOTAL TONNAGE WASTEWATER RESIDUALS SLUDGE COMPOSTED
TOTAL TONNAGE WASTEWATER RESIDUALS SLUDGE BYPASSED TO THE CLASS I LANDFILL
TOTAL TONNAGE WASTEWATER RESIDUALS NO TIP FEE RECEIVED (SEACOASTUTILITIES)
TOTALTONNAGE WASTEWATERRESIDUALSEXCEDENCEPERINTERLOCALAGREEMENTS
TOTAL TONNAGE YARDWASTE COMPOSTED
OVERALL TOTAL FEEDSTOCK TONNAGE COMPOSTED
OPERATING COSTPER WET TON FEEDSTOCK COMPOSTED
OPERATING COST PER WET TON WASTEWATER RESIDUALS COMPOSTED
CURRENT WET TON TIP FEE CALCULATION FOR WASTEWATER RESIDUALS GENERATORS (57% OF COST)
77
48.0%3
41,33!5
6,76:2
5.3213
6,0313
40,0215
81.361
$13 37
$26 31
$15 00I
-
SOLID WAST AUTHORIM OF PALM BEACH COUNTY
ANNUAL VEGETATION DISPOSITION SUMMARY
FISCAL YEAR 9 5 4 6
CITIZENS GIM-AWAY AREA
(1) THIS INFORMTWN IS TAKEN FROM A REPORT TITLED "INCOMINO M.S.W. BY SITE BY MONTH.
( I ) THIS INFORYITlON IS TAXEN FROM A REPORT TITLED W I N S W I C - . THIS INCLUDES THE CATAOORIES OF MQATATION" AND "COMPACTED MQATATWN"
(I)THIS INFORMATION IS TAKEN FORM A REPORT TITLED 715 TRANSPORTED TONNAOE BY MONTH"
(4) THIS INFORMATION IS ASSUMINO AN AVERAOE OF 300 LBSNARD FOR SINOLE OROUND AND WDCBSIIbRD FOR DOUBLE GROUND.
1o.m
2.000
0
OCT
NOV
DEC
JAN
FEE
APR
M*R
MONTH
78
MAY
JUNE
JULY
AUG
SEPT
VEGETATION MANAGEMENT
FISCAL YEAR TO DATE FY95196
PROCESSING COST ANALYSIS AS OF JULY 1 1996
c
PCCTL
5 1222
5 1400
52100
52200
52300
52400
52500
5 2600
TOTAL
5 3403
5 3405
5 3406
54001
54002
54101
54301
54302
54403
54404
5450 1
54601
54602
4603
46M
4605
4606
4607
1609.
5101
5103
5201
5202
5203
5205
5206
5208
EXPENSE
$104,834 33
$14.970 19
$9.258 41
$21.127 19
$1 1.02500
$20.563.13
$351.72
339.66
$429.82
SO.OO
$1.314 00
$3.140.43
$0.00
$177.080.09
$164.213.45
BUDGET FY94/95
$125,617 03
$13.000 00
$10.604 20
$24.366 71
so 00
$0 00
$351 72
000
$0.00
ACCOUNT TITLE
REGULAR SALARIES 6 WAGES
REGULAR OVERTIME
FICA TAXES
HEALTH INSURANCE
LIFE AND ACCIDENTAL DEATH INS
LONG TERM DISABILITY
SHORT TERM DISABILITY AND E A.P
ACCRUED SICK 6 ANNUAL
PERSONNEL SERVICES
$0.00
OTHER CONTRACTUAL SVCS
TRAVEL. CLASS A 6 B
TRAVEL CLASS C
TELEPHONE
ELECTRICITY
WATER AND SEWERAGE
EQUIPMENT RENTAL
SANITARY UNIT RENTAL
INSURANCE PREMIUMS
RIM-OFFICE EQUIPMENT
R/"FACILITIES 6 STA EQPT
R/"MOBILE EQUIPMENT
RIM-TIRES
RIM-MISCELLANEOUS
RIM-RADIO EQUIPMENT
RIM-GROUNDS
RIM-UTILITY SYSTEMS
RIM COMPOST SYSTEMS
OFFICE SUPPLIES
PHOTO SUPPLIES
S141.200.W
51.131.55000
$0.00
$0.00
$250.00
$0.00
540 1
5402
9962
9965
9966
9960
XPENSES
YEAR
EVENUE
$500 00
$0.00
$41,614.72
$0.00
$0.00
$357.51
$0.00
$0.00
$0.00
so00
$0.00
$0.00
SO 00
$0.00
$0.00
$0.00
$1,140.00
$23.680.00
s1o.OOO 00
$1.500.00
$5,200.00
$900 00
$5.M)o.00
SO.OO
$1,418.98
$18.824.43
$5.876.54
5396.50
$833 19
$233.75
$1 ,568.85
$3.040.00
$90.000.00
$0.00
$900.00
$650.25
SO 00
$22.238.00
$55,848.36
50.00
$0.00
$0 00
so.00
$0.00
$0.00
too0
ASSET DEPRECIATION
( STRAIGHT LINE DEPRECIATION)
TWENTYYEARASSETS
TENYEARASSETS
SEVENYEARASSETS
FIVE YEAR ASSETS
(RESIDUAL VALUES NOT INCLUDED)
$9.500 00
$588 00
$0 00
SO 00
$0.00
SO 00
so 00
$50.oo0.00
PERSONNEL 6 OPERATING EXPENSE
5304
$0.0
S I .M)o.00
OTAL
5210
$0.00
$1 13,037.92
$647.741.3
$0.0
$250.0
$0.0
50.00
OTAL
5209
$0.00
($339.66)
($429.82)
($1.314.00)
$3.14043
($7,133.36)
$0.00
SO 00
so 00
$4,080 00
$245 00
$0.00
$0 00
$42.480.00
GASOLINE
DIESEL FUEL
OIL L LUBE
TIRES, TUBES. ETC
MINOR EQUIPMENT
SAFETY EQUIPMENT
OTHER SUPPLIES
UNIFORMS
OTHER MATERIALS
BOOKS/PUBL/MEMBERSHIPS
MOBILE EQUIPMENT LABOR EXPENSE
GROUNDS MAlNT LABOR EXPENSE
FACILITY MAlNT LABOR EXPENSE
OPERATING EXPENSES
$0.00
328.162.08
$483.808.70
$0.00
$20.782 70
($1.970 19)
$1 ,345 79
$3,239.52
($1 1,0250 0 )
($20,563.13)
so00
$0.00
a DEVELOP
~~
SO M
$5,420 01
$0 M
$0O(
$500 M
$865 21
50.m
f 1 . m o(
($357 51
50.m
SO M
S50.000.M
50.w
$0ci
$0ci
50.n
(5278.98
$4.85557
$4.123 46
$1,103.5a
$4,366.81
$666 25
$3.431.15
s2.3a9.75
$90,000.00
$0.00
$900.00
($33.610.36
SO 00
$0 00
sow
$1.540.666.00
$643,918.86
$896.404 14
$1.717.746 09
$828.132.31
s8a9.270.7a
--
TO DATE
TOTAL
EXPENSES
COST FOR TRANSPORT FROMTRANS1
STATIONS
$828.132.31
$719.121.00
YEAR TO DATE TOTAL EXPENSES
$1.547.253.31
FIXED ASSET REVENUE
TIPPING FEE REVENUE
MULCH SALES REVENUE
$0.00
$1,641.700.00
s12.010.50
YEARTODATETOTALREVENUES
S1.653.710.50
EAR TO DATE
$106.457.19
PROFIT OR LOSS
PERCENTAGE OF BUDGET EXPENDEC
PROJECTED FISCAL EXPENDITURE BASED ON YEARTO DATE EXPENSES
TOTAL TONNAGE VEGATATION DELIVERED FROM TRANSFER STATIONS
TOTAL TONNAGE VEGATATION DELIVERED DIRECT TO SITE SEVEN
TOTAL TONNAGE VEGATATION DELIVEREDTO VEGATATION PROCESSING AREAAT N.C.R.S.W.D
OPERATING C 0 5 T S W A. OPERATIONS PER WET TON OF VEGATATION DELIVERED
TO N.C.R.S.
CONTRACT MULCHING COSTS PER WET TON OF FEEDSTOCK DELIVEREDTO N C.R.S.W.D.
TOTAL OPERATING COST PER WET TON FEEDSTOCK DELIVEREDTO N.C.R S.W.D.
79
48 23l
$1.074.68;
55.31
10.35
65.66
$5.21
57.3;
$12.6'
COST SAVINGS THROUGH REGIONAL BIOSOLIDS COMPOSTING
IN THE TRIANGLE REGION
Patrick Davis
Water Resources Project Director
Triangle J Council of Governments
Research Triangle Park NC
Judy l n c a i d
Solid Waste Planning Director
Research Triangle Park NC
INTRODUCTION
Several local governments in the Triangle region have recently completed a study evaluating the economic,
environmental, and technical feasibility of a regional biosolids cornposting facility. The study concluded that such a
facility could save money for local governments through economies of scale.
For many communities, co-composting of wastewater biosolids with materials such as yard waste, clean wood
waste, and mixed paper waste is becoming an increasingly attractive method for biosolids disposal. Increasingly
stringent regulations, public concern over environmental issues, and decreasing availability of suitable land
application sites within economical hauling distances combine to make sole reliance on land application of biosolids
a less attractive alternative for wastewater treatment plants. Furthermore, composting of clean wood waste and
mixed paper waste can be an important addition to an integrated approach to local government solid waste
management.
The problem is that composting facilities are typically expensive to build, operate, and maintain. Many local
governments cannot afford to independently develop these facilities.
The Town of Cary's recent need to develop a biosolids management plan for a wastewater treatment plant
expansion project provided the impetus for an interlocal exploration of regional biosolids composting in the
Triangle. Following several meetings organized by Triangle J Council of Governments, the Towns of Apex, Cary,
Clayton, Gamer, and Zebulon; the City of Durham; Durham County; and Orange Water andSewer Authority agreed
to cooperatively fund a $38,000 regional biosolids composting facility feasibility study. By working together, each
participant received a study that would have cost much more undertaken alone.
The feasibility study was conducted by E&A Environmental Consultants, Inc. from Cary, North Carolina.
Coordination of the study was provided by Triangle J Council of Governments.
The eight study participants currently manage a total of approximately 24 dry tons per day of biosolids, with
individual amounts ranging from less than one ton to over nine tons per day. This amount is steadily increasing
with the population growth in the region. The feasibility study compared the costs of capital, operations, and
maintenance expenses for three different facility sizes based onthe amount of biosolids handled each day: IO, 20, and
40 dry tons. This enabled individual governments to determine the potential economies of scale from forming
partnerships with neighboring communities.
The feasibility study also evaluated and compared the costs of three different cornposting technologies: aerated
static pile, agitated bed, anda combined aerated static pile and agitated bed
technology.
STUDY ASSUMPTIONS AND DESIGN CRITERIA
The single most critical factor in terms of facility size and economics of a biosolids composting facility is the
cake solids concentration of the biosolids. It was assumed for the purposes of this study that the biosolids arriving
at the facility would be 18% solids cake. This value was based on the experience of participating entities in
dewatering of biosolids. Currently, the City of Durham is the only study participant which actively dewaters
biosolids by mechanical means (i.e.. belt filter press, plate and frame press, centrifuge, etc.). The City of Durham
currently processes and dewaters digested biosolids to between 16% and 18% solids. which are then land applied. All
the other pqlclpants are currently land applying digested liquid biosolids ranging in solids content from2% to 6%
total solids.
It was also assumed that all biosolids brought to the facility would be well within the metal concentrations
llmits set by state and U.S. EPA standards for exceptional quality biosolids. Current metal concentrations in
biosolids from the participating entities is substantially below these limits.
Transportation costs to the facility were not included in the analysis. It was assumed that delivery costs would
be the responsibility of the participating entity and that biosolids and other compostables would be transported to the
facility in self-tipping vehicles, such as dump trucks, live-bottom trailers, or other vehicles with means for dumping
loads into bins or open storage pads.
It was assumed that the facility would be operated on an eight hour per day basis, five days per week. In addition
to this base operating schedule, it was assumed that the facility would be staffed and open for eight hours on
Saturdays solely to receive yard wastes and to load compost for customers. It was assumed that a set of weight
scales would be provided at the facility to determine weights of materials received and removed from the facility.
Biosolids receiving would be in a paved, totally enclosed building, adjacent to the mixing system. A series of
concrete bunkers or receiving bins would be used for participating entities to deposit their loads of biosolids. Space
was provided in the facility designs to allow for storage of up to half a days biosolids production on average.
Bulking agent storage was assumed to occur in an open asphalt storage pad with capacity to manage up to 60 days
worth of yard waste in an unground form. In addition, 60 calendar days of storage would be provided for ground
bulking agents which have been processed through the yard waste grinding unit. A two to one volume reduction was
assumed through the yard waste grinding operation.
Processing was assumed to occur on a five day per week basis, approximately 6 1/2 hours per day, for a total of
32.5 operating hours per week. Processing equipment was sized to process the daily average quantities of incoming
materials at a peaking factor of 1.5 or 150%.
Because no site had been established for a facility, a number of assumptions were made to allow for a generic
site. They included the following:
On-site utilities were assumed to be hooked up within 1,000 feet of the main building.
Road access improvements would be necessary only for 1, 0 0 0 feet of entry.
Adjacent off-site infrastructure improvements were assumedat a cost of $500,000.
The site was assumed to be fairly level, contain good soil, and have no unusual drainage problems.
The cornposting and storage areas were assumed to beset back 200 feet from the perimeter.
Fencing and a locking entry gate were assumed as costs in the cost estimate.
The cost of land was assumed at $40,000 per acre, amortized at 5% over 20 years. It was assumed that a tip fee
of $15 per ton would be charged for yard waste and similar bulking agents. It was also assumed thatthe sale price of
the finished compost product would be $4.00 to $6.00 per cubic yard. A $1 .OO per cubic yard of compost marketing
cost was also assumed, with sales only in bulk, not bags.
It was agreed by participants that biofiltration would be the technology used to treat odor from the composting
process. All three composting technologies examined were based on a totally enclosed mixing and composting
building with exhaust gases being treated through a biofiltration system. Curing, screening, and material storage
areas were assumed to bein combinations of covered or open storage pad areas which would not be connected to the
odor control system.
TECHNOLOGIES COMPARED
Two basic technology types -- aerated static pile and agitated bed -- were compared in the study, with a third
hybrid technology added in order to determine whether it could be more efficient andcost-effective than either of the
other two alone. Three sizes -- 10, 20, and 40 dry tons per day -- were examined for each technologytype, for a total
of nine different facility scenarios. Receiving, mixing, screening, and curing/storage areas would involve similar
XI
equlpment for all three technologies. The cornposting system itself is the part of the facility that would differ
depending upon the technology.
For all three technology types, yard waste and similar bulking agents would be dumped on a concrete storage pad
under cover. This area would have concrete pushwalls and could accommodate any type of bulking material that
needed to be kept dry. A mobile tubgrinder would be used to process yard waste up to 10 inches in diameter. A
discharge conveyor would allow staclung of the ground material into a surge pile which would be moved by front-end
loader into the amendment storage area. Ground bulking agent would be placed into a batch mixing box for the 10
dry ton per day facility. The batch mixer has a capacity of 18 1/2 cubic yards and is outfitted with weigh scales such
that precise quantities of bulking agent and biosolids can be measured and mixed. The mixed material would be
discharged into a surge pile in a concrete bunker. Because of the large quantity of material which must be handled for
the 20 and 40 dry tons per day facilities, a more automated mixing system was assumed. It would include two
receiving hoppers for biosolids and two receiving hoppers for bullung agent, whch would then discharge material
onto conveyors for transport to a continuous feed pugmill type mixer and subsequent stockpiling of mix material in
a surge pile in a three-sided concrete bunker. Both the batch mixer and the continuous feed mixer systems would be
permanently mounted and electrically driven and in a totally enclosed area.
After composting, the screening system for all three technologies would be under cover and would involve a
rotary trommel screen. The recovered bulking agent would be recycled back into the mixing process.
The subsequent aerated curing for all three technologies would take placeover 30 days under cover on an asphalt
pad. Aeration would be run i n a positive aeration mode only, using reusable high density polyethylene aeration
pipe. After 30 days, the compost would be moved outside onto an open asphalt storage pad until it is sent to
market.
In the aerated static pile composting technology, composting would occur in a totally enclosed pre-engineered
building with concrete flooring and pre-cast trenches to provide aeration. A base of wood chips would be laid down,
on which an eight-foot layer of mix of biosolids and bulking agent would be placed, plus a one-foot cover of finished
compost as an insulation layer. Offgases from the aeration blowers as well as the building air would be collected and
treated through an open biofiltration treatment system.
In the agitated bed composting technology, mixed materials would be placed into the front end of individual
agitated bed bays. The agitated bed system would be housed in a totally enclosed building with automated
temperature feedback controlled blower stations extending down the length of agitated bays. Each concrete bay would
be ten feet wide, seven feet deep, and 203 feet long. An automated turning device would ride on a series of rails to
the rear of the bay, where it would start turning the material by picking it up with an elevating faced conveyor and
throwing it over its shoulder, thus moving the material down the length of the bays. Eight bays and two agitators
would be required fro the I O dry ton per day facility, 15 bays and three agitators would be required for the 20dry ton
per day facility, and 30 bays with six agitators would be required for the 40 dry ton per day facility. Only positive
aeration would be provided, and offgases would be collected and treated through a biofilter system.
In the combination aerated static pile-agitated bed technology, the composting time within the agitated beds
would be reduced from 21 to 14 days. This would reduce the length of the bays from 203 feet to 152 feet and reduce
the number of agitators to two for the 10 and 20 dry ton per day facilities and four for the 40 dry ton per day facility.
BULKING AGENTS
The primary bulking agents assumed to be used in the cornposting facility were yard waste, clean wood waste,
and mixed paper. The local governments participating in the study manage a total of approximately 1 1,500 tons per
year of yard waste, and significant additional amounts are handledby neighboring jurisdictions. Based on waste
characterization studies in the region, it was estimated that approximately 22,000 tons per year of clean wood waste
in currently landfilled within the six-county region. It was also estimated that 17% to 20% of landfilled municipal
solid waste in the region is mixed paper waste.
The study concluded that between 7,300 and 8,350 tons per year of new bulking agent would be required for the
10 dry tons per day facilities; between 14,600 and 16,700 tons per year of new bulking agent would be required for
the 20 dry tons per day facilities; and between 29,250 and 33,400 tons per year of new bullung agent would be
required for the 40 dry tons per day facilities. Because mixed paper does not possess the structural integrity to
x2
STUDY CONCLUSIONS
The stud! results confirmed the partlclpants' expectations that there here slgnificant economies of scale to be
achleved through reglonal cooperation. This was true with regard to all three technologies. Figure 1 gives an
overview of the annual cost per dry ton processed for all nine facilities examined in the study.
FIGURE 1
Triangle J Regional Composting Facility
Annualized Cost per Dry Ton Processed
vs. Biosolids Input Capacities
I
A
B
h
I
\
\
\
\
0
20
10
30
Dry Tons of Biosolids p e r Day (5 Dayweek Basis)
4 Aerated
Static Pile
A AQitated Bed
*Agitated Bed-Aerated Static Pile Combination
x3
40
The annual costs i n Figure I include capital, amortization, and operating and maintenance costs. They do not
Include revenue from tip fees or compost sales, and they do not include land acquisition costs. The aerated static pile
technology was the least costly option: $321 per dry ton for the I O dry ton per day facility, $261 per dry ton for the
20 dry ton per day facility, and $219 per dry ton for the 40 dry ton per day facility. The agitated bed technology was
the most expensive option: $405 per dry ton for the I O dry ton per day facility, $320 per dry ton for the 20 dry ton
per day facility, and $262 per dry ton for the 40 dry ton per day facility. The combination facility fell in between the
other two technologies in cost: $366 per dry ton for the 10 dry ton per day facility, $294 per dry ton for the 20 dry
ton p e r day facility, and $239 per dry ton for the 40 dry ton per day facility.
The land area requirements for the processing areas of the 10, 20, and 40 dry ton per day sizes of aerated static
pile facilities were 2.5,4.5, and 8.4 acres. The land area requirements for the processing areas of the three sizes of
aerated static pile-agitated bed facilities were 2.3,4. I , and 7.6 acres. The land area requirements for the processing
areas of the three sizes of agitated bed facilities were 2.4,4.3, and 8.0 acres. With the 200-foot setback, the acreage
requirements were considerably more, ranging from 13.9 to 33.0 acres.
Economies of scale and the relative costs of the three technologies were also apparent when factoring in the cost
of land and the anticipated tip fee and compost sale revenues. These adjusted figures are included in Table I . The
adjusted annual cost per dry ton for the aerated static pile technology was $244 to $263 for the I O dry ton per day
facility, $186 to $205 for the 20 dry ton per day facility, and $135 to $153 for the 40 dry ton per day facility. The
adjusted annual cost per dry ton for the agitated bed technology was $340 to $356 for the 10 dry ton per day facility,
$250 to $266 for the 20 dry ton per day facility, and $190 to $206 for the 40 dry ton per day facility. The adjusted
annual cost per dry ton for the combination facility was $293 to $310 for the I O dry ton per day facility, $217 to
$234 for the 20 dry ton per day facility, and $158 to $176 for the 40 dry ton per day facility. The range in cost is
due to the range in composting revenue assumed: $4.00 to $6.00 per cubic yard.
IMPLICATIONSFOR BIOSOLIDS MANAGEMENT
Two of the study participants are currently paying a cost for biosolids management through land application that
is higher than the cost they would incur by composting at an aerated static pile facility sized for 20 dry tons per day.
These two entities combined arecurrently handling approximately 12 dry tons per day of biosolids, but they estimate
that by the year 2006 they will be handling a combined total of approximately 20 dry tons per day. A regional
facility appears to be a cost effective method for biosolid management for these two entities.
Other study participants are currently paying less for land application of biosolids than they would pay for
composting at a regional facility. However, the availability of a composting option at a regional facility could be of
great benefit to them during periods of inclement weather when land application is not feasible. For this reason,
other study participants are potential users of a regional biosolids composting facility if such a facility should be
built.
IMPLICATIONS FOR SOLID WASTE MANAGEMENT
The bulking agent requirements for a biosolids composting facility are such that all of the yard waste in the study
region could be composted at the facility. A significant amount of clean wood waste from construction could also be
composted in such a facility.
The study also concluded that food waste could be composted at the facility in the same ratio with bulking agent
as 1 8 9 cake biosolids is composted with bulking agent. This ratio is one ton of biosolids or food waste for ,578
tons bulking agent.
This factor can be significant in managing solid waste, in that food waste is approximately 6% of landfilled
municipal solid waste. Composting merely a portion of this food waste would be extremely helpful to local
governments trying to achieve waste reduction goals. Moreover, the composting of food waste opens up an
opportunity to compost more bulking agent. Up to one-third of the bulking agent in a composting facility could be
mixed paper, so more composted food waste would provide an opportunity toreduce the landfilling of mixed paper.
A further benefit of adding food waste to biosolids for composting is that it would result in even further
economies of scale. If the facility were handling closer to 40 than 20 dry tons per day, the cost per dry ton would
decrease significantly, and every user of the facility would incur lower costs.
Q
W
4
N
W
N
I-
W
N
r-
P
z
x5
2
N
The annual adjusted cost per &y ton of biosolids for a 20 dry ton per day aerated static pile facility would be $186
to 5205. This translates Into a cost per 1 8 4 dry. or food waste, cost of $33 to 37 per ton. For a 40 dry ton per day
aerated statlc plle facihty, this cost would be $24 to $28 per ton.
NEXT STEPS
Two of the study participants are now working with Triangle J Council of Governments to evaluate the
economic, environmental, and institutional feasibility of establishing a regional biosolids composting facility and to
identify potential sites for such a facility. These participants have concluded that there are significant benefits from
cooperating in a regional biosolids composting facility:
economies of scale in constructing, operating, and maintaining a facility;
economies of scale in marketing compost to end users;
minimized potential for conflict and competition in compost marketing;
a biosolids management option for periods when land application is not possible; and
extended life for municipal solid waste landfills due to the opportunity to compost other materials with
biosollds.
These study participants have made an initial determination that the aerated static pile composting technology is
the preferred approach; that the facility shouldbe publicly-owned and either publicly or privately operated; and that a
20 dry ton per day facility size is preferred, with land acquisition to allow for expansion to a 40 dry ton per day
facility size.
The next products expected from this regional effort are a set of general principles for guiding the further
development of a regional biosolids composting facility; recommendations concerning the legal structure for public
ownership; and a draft interlocal agreement related to these objectives.
X6
MUNICPAL SOLID WASTE COMPOSTING: DOES IT MAKE ECONOMIC SENSE?
Mitch Renkow
Department of Agricultural and Resource Economics
A. Robert Rubin
Department of Biological and Agricultural Engineering
INTRODUCTION
Municipal solid waste composting is an alternative to the disposal of garbage in sanitary landfills.
Municipal solid waste (MSW) composting facilities are currently operational in more than a d o z n locations
throughout the United States, and many communities are currently exploring the possibility of incorporating
MSW composting into their integrated solid waste management systems. The growing interest in MSW
composting has been stimulated by a desire to minimize the amount of garbage entering landfills - either as a
way meeting state waste diversion requirements or as a way of extending landfill life.
Communities contemplating establishment of an MSW composting facility need to weigh several factors,
including the environmental consequences of landfills versus composting, the relative political and social costs of
siting landfills and composting facilities, and the economic implications of the alternatives. In this factsheet, we
present information on the costs of MSW composting and how those costs compare with the costs of land
disposal in sanitary landfills. Following a brief overview of MSW composting technologies, we report the
results of a survey of 19 MSW composting facilities around the United States. We then use the cost information
collected in the survey and actual landfill cost data from one North Carolina county to compare the cost of
MSW composting versus the cost of land disposal. This analysis indicates that even accounting for the
beneficial effects of delaying construction of a new landfill, a solid waste management system that includes
MSW composting costs significantly more than a solid waste management system without MSW composting.
MSW COMPOSTING TECHNOLOGIES
Composting is a controlled biological process that uses natural aerobic processes to increase the rate of
biological decomposition of organic materials. It is carried out by successive microbial populations that break
down organic materials into carbon dioxide, water, minerals, and stabilized organic matter. Carbon dioxide and
water are released into the atmosphere, while minerals and organic matter are converted into a potentially
reusable soil-like material called compost. The loss of water and carbon dioxide typically reduces
the volume of
remaining material by 25 46 to 60%; compost can be used as a soil amendment in a variety of agricultural,
horticultural or landscaping applications.
Composting is most commonly confined to municipal yardwaste operations that use leaves, grass clippings,
and other yard trimmings as a feedstock. The number of yardwaste composting facilities throughout the country
has grown tremendously over the past five years as state regulations have increasingly banned yard trimmings
from landfills. MSW composting processes glJ of the biodegradable components of the wastestream that
decompose most readily - paper, food waste, and wood in addition to yard trimmings. On average, these
materials account for 55%-7096 (by weight) of a community’s solid waste. The significant volume reductions
associated with composting and the possible uses of compost make MSW composting attractive as a potential
87
F
means of diverting waste from landfills. On the other hand, MSW composting requires considerable pre-sorting
of the incoming waste and screening of the finished product to remove uncompostable materials such as glass,
metal, and plastic - activities that tend to be relatively costly.
The two basic processes used in large scale composting are windrow-based technologies and in-vessel
technologies. In windrow systems, waste is brought to a central open air facility and formed into windrows that
are three to five feet high.' The windrows are turned periodically to maintain a stable temperature and .rate of
decomposition, and water is added as needed to maintain an appropriate moisture content. After a desired level
of decomposition is reached, the composted product is ready for assembly and distribution to end-users. A
somewhat more sophisticated alternative to the simple windrow system is the aerated windrow system. Aerated
windrow systems replace manual turning of windrows with a nehuork of pipes that force air into the windrows.
In-vessel systems employ considerably more sophisticated proprietary technologies. These technologies
offer a highly controlled, enclosed environmeot for effecting the biological decomposition needed to produce a
highquality product. In-vessel systems tendtobe considerably more capital intensive than windrow
technologies, though, requiring a larger initial investment. In addition, the greater technical complexity of these
systems usually requires a workforce that is more highly trained (but fewer in number) for operating the
composting facility.
COSTS OF MSW COMPOSTING FACILITIES
A telephone survey of MSW composting facilities operating in various parts of the country was conducted
in the spring of 1995. Nineteen facilities were contacted, and facility managers were asked a number of
questions regarding the specific composting technology employed (windrow, in-vessel, etc.); operational details
(process time, percent volume reduction, annual throughput); costs (both debt service and operating/maintenance
costs), disposition of the finished product (usesand users, revenues from sales, and quality control systems to
assure product consistency). Respondents were also queried as to any problems that had been experienced since
start-up and ways in which problems were dealt with. Of the nineteen facilities contacted, three have shut
down. One facility (located in Escambia Co.. FL) was closed due to liability and cost problems, one (located in
New Castle, DE) was forced to shut down due to odor problems, and one (located in Pembroke Pines, FL) has
shut down temporarily due to technological problems.
Table 1 provides an overview of 17 oftheMSW composting facilities surveyed.' Of the seventeen facilities
listed, ten are publicly owned and operated, five are privately owned and operated, and two are publicly owned
operated by private firms. About 4 0 % use in-vessel technologies, with the balance relying on less sophisticated
windrow systems. Annual throughput varies considerably, although publicly operated facilities tend to handle
smaller volumes of waste. With one exception, process time ranges from one to four months and volume
reduction ranges from 2 5 % to 70%.
Table 2 indicates the uses of finished product from the facilities surveyed. Over half the facilities listed
farmers and/or landscapers as the primary users of the compost that is produced. Six facilities contract with
nurseries for disposal of some of their compost, and in five cases compost is used as landfill cover. Somewhat
surprisingly, only two facilities provide compost for use as roadside fill dirt. In general, most compost was
given away at no charge.
'Windrow formation may be preceded by shredding the incoming product to reduce particle size at the
outset of the composting process.
W e include information for the Pembroke Pines facility, even though it is not currently operating.
X8
Table 1. Overview of MSW cornposting facilities surveyed
Location
Publiclv owned and owrated facilities
Columbia Co., WI
in-vessel
Lakeside, AZ
in-vessel
Martin/Fairbault Co., MN
in-vessel
aerated windrow
M a c k Island, MI
aerated windrow
Portage, WI
Sumter Co., FL
aerated windrow
Wright Co.. MN
aerated windrow
Buena Vista, IA
windrow
Fillmore Co.. MN
windrow
Lake of the Woods, MN
windrow
Publiclv owned and Drivatelv omrated facilities
Sevier Co., TN
in-vessel
Mora, MN
windrow
Privatelv owned and Drivatelv owrated facilities
Baltimore, MD
in-vessel
in-VeSSel
St. Cloud, MN
Whatcom Co., WA
in-vessel
Pines,
Pembroke
FLb
aerated windrow
Montgomery Co., KS
windrow
2
4
4
3
67-80
10-12
100
150
200-250
6.P
509
6
'
500-600
65
60
100
550
5040
1.5
2.0
2.0
1.5
2.0
nla
200-400
9
7
nla
5
8
6
3
4
16
50-55
175
35-40
11
1.5
2.5
3.0
3.0
2.0
3.0
2.0
4.0
4.0
3.0
1.o
1.5
2
7
4
4
9
nla
50 %
45 %
50 %
nla
60 %
25-50 %
70 96
50 %
60 %
a. The Mora facility also processes some compost for 12 months with volume reduction of 60%.
b. The Pembroke Pines facility is not currently operational.
40%
%
50 %
50 4%
60 %
loud,
Table 2. Disposition of final product at M W composting facilities surveyed
Location
How product is used
Publiclv owned and owrated facilities
Columbia Co., WI
Lakeside, AZ
MartinIFairbault Co., M N
Mackinac Island, MI
Portage, WI
Sumter Co., FL
Wright Co., MN
Bueoa Vista, IA
Fillmore Co., MN
Lake of the Woods, MN
Agriculture
Landscaping
Agriculture,landscaping,nurseries
Landscaping, landfill cover
Agriculture, landscaping
Landscaping, roadside fill dirt
Agriculture, landscaping, roads, nurseries, landfill cover
Landfill cover
Agriculture, landscaping
Soil conditioner for closed landfill
Publiclv owned and privatelv operated facilities
Agriculture,
landscaping,
nurseries
TN
Sevier Co.,
Mora, MN
Landscaping, nurseries
Privatelv owned and Drivatelv owrated facilities
Baltimore, MD
Agriculture
St.
MN
Agriculture
Whatcom Co., WA
Nurseries
Pines,
Pembroke
FL
Agriculture,
nurseries
Landfill cover
Montgomery Co., KS
o n l y nine of the facilities contacted were able to provide sufficient cost information to allow computation of
average costs on a per-ton basis. In the case of privately-operated facilities, most firms informed us that this
was proprietary information that they were reluctant to divulge. Public composting facilities were considerably
more forthright about their costs; however, in several cases the requisite data (particularly data on operating and
maintenance costs) was simply unknown by the facility manager.
A n n u a l debt service costs were, in most cases, provided by survey respondents. Where debt service
information was unavailable, these costs were computed as 10% of initial capital investment (comparable to
principal and interest payments on a bond h a n d at 8% over a 20-year period). In the case of the Sevier
County facility, the reported initial capital cost of $6.5 million included a significant subsidy on the part of the
vendor of the composting technology (Bedminster Corp.). Presently, a comparable system would cost twice that
amount, and hence we computed the "unsubsidized" a n n u a l debt payments based on the price that a prospective
purchaser would have to pay for establishing a similar facility. Finally, annual debt service costs and a n n u a l
operation and maintenance ( M M ) costs were divided by the number of tons of a n n u a l throughput to arrive at a
cost per ton.
k
Table 3. Costs of selected MSW composting facilities
O&M
Type of
system.
Average
Volume
(ton/day)
service
costs
Revenue
($/ton)
($/ton)
($/ton)
Net cost
($/ton)
Sevier Co., TN
- reported
- unsubsidizedb
I-v
I-v
150
150
$13
$26
$23
$23
$1
$1
$35
$48
Columbia Co.. WI
I-v
74
$14
$29
none
$43
Baltimore, MD
I-v
550
$27
$24
none
$5 1
Martin/Fairbault Co., M N
I-v
100
$28
$5 1
none
$79
Portage, WI
AW
16
$26
$24
none
$50
Wright Co., MN
AW
175
$28
$23
none
$5 1
Sumter Co., FL
AW
53
$22
$52
$20
$54
Fillmore Co., MN
W
11
$4 1
$240
none
$28 1
Lake of the Woods. MN
W
1.5
$176
$1.795
none
$1,971
$26
$28
Location
Debt
Weighted average'
a. I-V
=
in-vessel; AW
=
aerated windrow;W
SI
$53
= windrow
b. "Unsubsidized" estimate assumes an initial capital cost of $13 million (asopposed to the reported value of
$6.5 million).
c. These are mean costs (weighted by tons processed), excluding the Fillmore County and Lake of the Woods
facilities, and using the unsubsidized estimate for the Sevier County facility.
Table 3 lists the per-ton costs for the nine facilities that supplied cost information. There it will be observed
that for six of the nine facilities, net costs lie clustered around $50 per ton (ranging from $43 to $54). One
facility cost $79 per ton, and two other facilities - both of which handle relatively small amounts of material
annually - had extremely large per-ton costs. In only one case were sigmficant revenues from compost s a l e s
reported.
Respondents generally reported being pleased with how well their facilities were operating. Two
problems odor and residual plastics in the final product - were identified by a number of individuals questioned. Three
respondents cited odor as a continuing problem, and an additional four had had odor problems that were
remedied by installation of bio-filters. Residual plastics were cited as problematic at seven facilities. In most of
these cases, this has l e d to greater emphasis on pre-sorting of feed stock prior to composting.
In summary, our survey indicates that MSW composting facilities generally involve costs around of $50 per
ton, although we did uncover some cases of extremely large operating costs for a couple of facilities handling
relatively s a l amounts of trash. The great bulk of facilities contacted receive no revenues for the compost
they produce; rather, they generally give the finished product away to farmers, landscapers, nurseries, and
landfills. We found little evidence of any particular cost advantage related to public versus private operation.
Respondents generally appeared to be satisfied with the operational aspects of their facilities. Odor and residual
plastics were identified as the primary areas of concern, but most operations had developed mechanisms for
dealing with these problems.
Msw COMPOSTING VERSUS LANDFILLS
The survey results presented above indicate that communities contemplating MSW composting as part of
their integrated solid waste management system should expect composting to cost in the area of $50 per ton. In
North Carolina, this is above what it costs nearly all municipalities and counties to dispose of waste in sanitary
landfills. However, as mentioned in the introduction, one of the benefits of municipal solid waste composting is
that it extends the life of landfills by diverting waste. A key economic question that arises in assessing the
desirability of establishing a MSW composting facility, then, is whether or not the economic benefits of
extending landfill life exceed the additional cost of processing waste through composting.
To address this question, Table 4 compares the cost of landfilling all waste generated within the county with
a hypothetical scenario in which 50% of a county’s waste is landfilled and 50% is processed at a MSW
composting facility. To do so, we utilize 1995 landfill cost data from Rowan County, North Carolina. Rowan
County owns and operates a sanitary landfill that currently handles approximately 100,OOO tons of garbage per
year at a cost of just under $24.00 per ton. Total costs are made up of three roughly equal components: (a)
Operating and maintenance (O&M) costs; (b) debt service on the capital outlay for construction; and (c)
contributions to a reserve fund for environmental monitoring. Note that contributions to the reserve fund are
fixed costs that accrue regardless of the amount of waste handled; a reduction in the amount landfilled therefore
increases the per ton cost of this cost item. Debt service is also a fixed cost; however, extending the life of the
landfill effectively draws out the period of time over which initial capital outlays are paid off and hence will
lower the size of the total annual principle and interest payment (although not necessarily on a per ton basis).
Finally, variable c o s t s will fall in direct proportion to the reduction in waste landfilled and so remains constant
on a per ton basis.
Rowan County is currently planning to develop a new cell (at a cost of $3 million) that will take 7 years to
fill up at current waste generation rates. The first column in Table 4 provides the costs for the “landfill
everything” scenario. These cost figures assume that (a) the $3 million capital outlay is financed over the seven
years it will take to fill the cell up, at
interest rate of 5 % ; (b) the current amount set aside annually for
enviroMlental monitoring remains constant; and (c) current per-ton variable costs remains constant. Given
these assumptions, the total annual cost of solid waste management would be $2.2 million (or $21.28 per ton of
waste handled).
The remaining columns of Table 4 present the costs of solid waste management assuming that half of the
waste generated within the county is landfilled and half is processed at a MSW composting facility. Here, we
take the variable and fixed costs of MSW composting to be equal to the averages derived from the results of our
survey of composting facilities presented earlier ($30and $20 per ton, respectively).
92
Table 4.
Comparison of annual waste management costs with and without MSW cornposting
Landfill
+ MSW Composting
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
Landfill
OdY
Landfill
Cost
Compost
Cost
Total
Cost
Fmed
$2,195,496
cost' $1,053,670
$1,141,826
$1,357,213
Variable
$2,023,238
Costb
$1,580,505$442,733 $885,465
Total
$4,218,733
Cost $2,634,175
$1,584,558
$2,242,678
105,367
Tons of 52,684
garbage
52,684
Fixed cost per ton$20.84
Variable cost per ton $8.40
Total
$40.04
cost per$50.00
ton
$30.08
105,367
$12.88$20.00
$21.67
$8.40
$19.20 $30.00
$21.28
a.
Fixed cost for the landfill includes contribution to a resewe fund for environmental monitoring. Fixed costs
for the landfill are computed assuming a $3 million loan at 5 % interest paid out over 7 years in the
"Landfill Only" scenario, and over 14 years in the "Landfill + MSW Composting" scenario. Fixed costs
for MSW composting are assumed to be $20 per ton of waste handled.
b.
Variable costs for the landfill are assumed to be $8.40 per tonof waste handled.
composting are assumed to be $30 per ton handled.
Variable costs for MSW
Diverting half of the county's waste to a MSW composting facility entails processing half the county's
waste steam at a per ton cost that is more than twice the cost of landfilling. There is some cost saving in
extending the life of the landfill by lengthening the period over whch debt needs to be paid off. ' h s cost
saving only partially offsets the greater cost involved in composting, however.' The overall impact of diverting
half of the county's waste to a MSW composting facility is an 88% increase in the county's a n n u a l solid waste
management bill - from $2.2 million ($21.28 per ton) to $4.2 million ($40.04 per ton).
From a financial perspective, it is clearly not possible to justify construction of a MSW composting facility
for the specific case of Rowan County, even when the value of extending a landfill's life is taken into account.
In
' fact, the per ton cost of landfilling actually rises, due to the fact that while fixed costs drop by 15% the
amount of trash over which these fixed costs are spread falls by 50%.
03
Further analysis indicates that only if landfill costs were more than double those of Rowan County ($59.00 per
ton) would processing waste at a MSW composting facility become economically feasible. Disposal costs are
currently much lower than this at most, if not all, landfills in North Carolina. We conclude that only if landfill
costs were to rise considerably - or markets for compost were to develop such that revenues from compost
sales grew eoough to substantially offset the higher costs of composting - would MSW composting become an
economical component of a community's integrated solid waste management strategy.
DOES MSW COMPOSTING MAKE SENSE?
From an economic perspective, communities contemplating MSW composting as a component of their
overall solid waste management system should proceed with great caution. It is clear
that at present MSW
cornposting cannot be justified on financial grounds where landfill costs are relatively low (asin North
Carolina). It is conceivable that there are other factors that might justify the larger costs of MSW composting
in some communities. One such factor is the strength of state- mandated waste diversion requirements. Where
these mandates are binding - and to the extent that other, cheaper alternatives such as yard waste composting do
not divert sufficiently large volumes from landfills - MSW might be rendered more attractive (although no less
costly).
A second possible reason sometimes offered as to why some communities might want to explore MSW
composting has to do with the difficulty of siting a new landfill. According to this argument, if a community
perceives MSW cornposting to be more environmentally "friendly" and/or to be less damaging to local property
values than land disposal, it may be easier to site an MSW composting facility than a new landfill. This
contention is probably no longer true for most if not all communities, however, given recent well-publicized
negative public reaction to MSW composting facilities in various locations across the country due to odor
problems and cost overruns.
DEVELOPING AND FACILITATING GREEN INDUSZRY MARKETS
FOR COMPOSTED ORGANIC MATERIALS
Anita R. Bahe. Ph.D.
Car_\..North Carolina
Introduction
Choosing alternative strategiesfor handling the by-products of growth and consumption, particularly
solid
wastes, requires addressing issues that are somewhat nonexclusive in nature (i.e., address public
goods and
scnices). Therefore the decisions concerning implementation
of various alternatives will affect the stateof social
welfare. One alternative strategy, organic waste ( resource) reutilization (composting and compost utilization), is
an important component of integrated waste management planning thatinvolves an interaction of technical
(scientific) and economic considerations. Technical innovationsin recent years have not only made the process of
composting much more clTicient. but also have made it possible to produce a wide array of quality compost
materials having spccific and desirable characteristics. This technological progress is accompanied by ongoing
global efforts totvard the goal of greater environnrenlal sustainabili@. As a result there are continuous changes in
policies concerning waste management, land utilization, and renewable resources, perhaps enhancingthe viability
of increasing composting activities.
Such technological. political, and economicevolution poses various consequences to the composting
indust&. including an increased demand for rcadily available and diverse recycled organic products. This
increased demand means new market opportunities. Although scientific advancements in the processing of
compost have gained i n elliciency, the econonlic feasibility as an alternative to landfilling andor incineration may
depend on the establishment and maintenance of
high quality markets. The success of such an endeavorwill be
influenced by the proper identification of potential consumers, assessment of their specific needs,and recognition
of their demands. As an example. some clients may wish to purchase a high quality compost
to be used as a soil
amendment or soil conditioner, as opposed to a substitute for inorganic fertilizers or for use as a mulch. Successful
source, thus requires an economic
marketing of compost as a soil amendment rather than a primary fertilizer
assessment of the benefits that are not necessarily related to the nutrient content of the product. When nutrient
be used to
value is of importance to the consumer. market prices (per Ib. a.i.) of common inorganic sources can
provide an indes of the consumer’s willingness-to-pay (WTP) for complimentary or substitute goods. Where
nutrient content is not of primary importance. other tangible and intangiblebenefits require identification,
therefore more specific field research will probably be necessary in order to determine the appropriatecosts and
benefits.
Steps in Market Development
Prior to establishing and fundingnew research protocols, it is important to target potential consumers and
identify the stakeholder groups that are likely to be affected by market activity. Stakeholders are individuals,
organizations. or groups who (which) affect andor are a e c t e d by decisions concerning an alternative course(s)
of
action (Dunn etal.. 1988). With regard to high qualih compost markets. possible stakeholders include the
producers of quality conlposted materials. the consunlers of organic materialsthat demand speclfic product
characteristics. and other citizens (non-users)that are indirectly affected by the production and utilizationof these
products in their communities.
After stakeholders have been identified it is important to define the niche (typeof market category) this
producer/consumer interaction falls into. Specifically, what are the market forces motivating the decisionto divert
more organic wastes into the processing of higher quality (high value) compost?Is t h s market development being
driven by the presence of prevailing rlrarkef opportunities (i.e.. purecompetition as private good)? or arethe
current markets too competitive or unavailable causing a focal shift to non-traditional market issues (as with pure
public goods)’? or are iltrpevcct rrrarh-ets (Le. not purely competitive as with quasi-private goods) an option
(Pearce etal.. 1994)? Assessing the niche ‘fit’ means identifving whether or not the good provides enough public
E
bcncfits to bc constdcrcd t~o~~-c.~clu.rr\v
and/or suttablc i n a traded market system. Currently, compost SeenlS to
rldc the line bctncen ‘nlarketcd goods w i t h significant public benefits’ and ‘non-marketedgoods with public
benefits’. Question then. \\helher the production of high quality composts to meet specific consumer demandcould
causc a shift to a quasi-pri\.ate (non-exclusive)marketed good with both private and public benefits. This is
presumably a probable outconle.
Assessing the Market
Often non-cxclusivity is partnered with imperfect market conditions, thus enablingthe use of several
valuation techniques for assessment of the potential costs and benefits. First, the term ‘value’ requires specific
definition for purposes of consistency and accuracy in market analysis. Often individuals refer to ‘value’ as
meaning desirable and/or useJul (Pearce etal., 1994). Defined as such, ‘value’ becomes a criterion and the
valuation process is used to establish monetary measures or eschange worth. In the valuationof many pure private
goods. the surrogate nrarkef technique can be employed. Here existing markets for goods or services that display
some relativity to the costs and benefits of the surrogate good are appraised. For a surrogate good like a high
quality compost. cxamples of existing markets include organic fertilizers, peat, and topsoil. The inherent
acceptability of other recycling programs and products could even serve as a measure of value. The problem with
the surrogate market technique is that it is limited to assessment of use values only.
For a quasi-private market like that of high quality compost, methods that include analysis of tangible
(use) and non-tanglble (non-use) values would be more appropriate. The total value of the compost would then be
based on assessment of opportunity costs, optionand existence values, costsof uncertainty and the actual use
values (Mitchell and Carson. 1993; Pearce et al.. 1994, Sugden and Williams, 1978). These types of costs and
benefits are defined in Table I . These measures can be further employed by using scientific surveys of targeted
consumer groups in an effort to determine theirtrue value of the commolty. The contingent valuation (CV)
survey technique is a particularly useful tool for assessing consumer’s willingness-to-pay (WTP) where many
potential non-use values and intangible costs and benefits may exist (Mitchell and Carson. 1993).
The contingentvaluation method (CVM) has become one of the more accepted scientific survey
techniques used to assess goods and services that have associated environmental effects. CVM is used to acquire
information about the preferences that individuals and/or groupshave for specfled goods or services. When using
the CV method: 1) hypothetical markets are created, 2) respondents (targeted consumers) aregiven as much
information as possible to ensure that they are accurately informed about the good to be valued, and 3) the
appropriate payment vehicle and questioning technique are then selected. By using CV, the change in well-being
that the survey participant(s) incur as a result of access to a good or service can be established in monetary terms.
The CV method is perhaps the best survey technique market researchers canuse when assessing the value of pure
public or quasi-public (quasi-private) goods’. In the event that market researchers are assessing the value of pure
private goods. other methods are often used, especially those intended to use price cottiparison as the primary
indicator of value. Having laid out a generalized market development scheme, certain componentsof the plan can
now be used to more specifically determine the needs of targeted consumers.
One groupof consumers that could potentially constitute a high quality and highvalue market includes
golf course superintendents. urban landscapers, topsoil blenders, and greenhouses,generally categorized as the
greet1 industy. Green indusf~v
consumers demand a materialthat is of the highest acceptable standards and
consistency with respect to both physical and chemical characteristics for use as a soil amendment. Realizing the
cost elTectiveness of using compost soil amendments in heavily scrutinized landscape maintenance practices, such
as golf course turf or greenhouse production. both tangible (actual use) and intangible (non-use) values must be
assessed. Operational field research is one way to enhance the attainment of this type of cost and benefit
information.
I
Detailed information about the use of this method can be found in Usinn Surveys to Value Public Goods: The
Contingent Valuation Method (lY93) by R.C. Mitchell and R.T. Carson.Resources for the Future. Washington,
D.C.
T;~ble1. Definition of cost and benefit measures discussed.
)
I
I
I
II
opportunitv costs - *’ the value of production forgone by using particular inputs
to produce particular output” ; “what is forgone in order
to choose or obtain an alternative”
option and existence values- ‘‘ Ilaving the choice or rightto purchase or obtain
a desirable good or service” and ‘‘ value gained froman
amenity for reasons other than expected personal use”
uncertainty and risk - “the value of knowledge and assurances concerning
the effects (and irreversibilityof effects) andthe type
and amountof risk (risk aversivion) associatedwith
an alternative courseof action”
actual use value - “the amount of utility gained from the direct or indirect
personal use of a good or service”
I
I
Research Aooroach
Research I recently completed at NCSU is an esample of how a protocol can be derived in which
operational field research is conducted within a cost-benefit analytical framework. I attempted to addresssome of
the cost-knefit questionsas they pertain to compost utilization in ongoinggolf course management. The discovery
of effects. such as added nutritional value, soil physical or chemical property changes, metal accumulation
potential. etc. inevitably influences the ‘valuation’ of the amendment in user speclfic situations. But, taking a
practical view of golf course management, it was apparent that other factors were influential in the valuation
process and often were unaccounted for by compost marketers. Thisis especially true for end users that are
required to meet the highest quality standards forwhat they produce in this case tees, fairways, and golf course
greens. A lower tolerance for less than acceptable conditions is likely demonstrated by owners of private clubs and
owners. members. and management.more often than by homeowners or highway travelers glancingat beautified
roadsides. Implementing appropriate research projects can help to further define anddevelop the type of organic
materials that are acceptable to the golf industry.
The NCSU study was an operational field research project that involved testing four organic amendments,
each tovdressed four times per year at two different rates following aerification of bermudagrass (Cynodon
clnctvlon) tees and fairways (Tables 2 and 3 ) . The trials were conducted on three different golf courses in the
Carolinas. The soil type and management differed somewhat at each location. Soil samples (2.5 cm x 5 cm cores)
and l e a f tissue samples were collected monthly the duration of the study and tested for most of the major nutrients
implications
and heacy metals. The objective of this research was to determine the agronomic and environmental
of using these amendnlents as an added management
tool. Further, this informationwas applied to an assessment
of the economic efficiency associated with producing and using acceptable quality recycled organic materials for
urban landscapc management.
-
AnronomicBiolonical Effects Summary
It was interesting to discover that the agronomic and/orbiological effects resulting from the application of
each amendment were either beneficial or nondetrimcntal to the nutrient statusand toxicity of the turfgrass
ecosystem to which they were applied. Consider for example that: I ) soil rhizosphere P, Ca, and Mg
concentrations were positively affected by the RKSS’ and SCTYW treatments, 2) foliage N-P-K levels were
increased with the RKSS and Ca’ and Mg levels were increased with the SCTYW, 3 ) soil rhizosphere Cu and Zn
levels were increased with BDMSW’ and RKSS’ (though site specific), and 4) foliage concentrationsof Cu and
I
Indicates statistically significant treatment effects at all trial locations with an alpha= 0.05, e=treatment*date.
97
SS with small wood chips used as a bulking agent
b
j (SCTYW)
.
. . .
. ...... .. . .
.
..
.. .
... , . .
. . .
a yard waste (YW) compostproduced by The OM.Scotts Company in
Marysville, OH using an mechanically aerated
windrow. technology
.
. . .
.
I
/
,
*
; (MFHM)
. ...... ....
.. . . .. ...
:.
,.
,.
an
additional
organic
nuterial referred, to asgranular
a
humate, is formed
by natural deposition in the SouthwesternUSA and is extracted, air dried,
screened, and bagged by the Menefee Mining Co., Dallas, TX.
Mn were increased at two sites by RKSS and MFH" respectively. There were also site speclfk increases in
organic matter content from the different treatments over time.
The associated increases in the availability of micronutrients would be of great economicvalue in
managing turf due to the potential to enhance disease tolerance. This is a subject of current interest yet in need of
furtherrescarch. In the event that further research revealed such positive effects on turf health, growers would be
bctter able to 'value' certain nvorded cosfs.such as expenditures for specific fungicides or for replacement seedsod
that may otherwise be required. The chemical analysis of the amendments tested revealed that each of the batches
received within a specific compost tqpe were quite consistent with respect to elemental concentrations, pH. and
organic matter content. This is important from a quality assurance standpoint andis very important to
marketability.
ldentifyinp Acceptability
Despite this positive news, acceptability of use, which did increase as some of the risks ofuncerfuinty
declined. was still not high enough for a successful market to be developed. Why? There were certain problems
associated with the physical properties of the certain amendments. Excessive moisture, clumping, oversized and/or
lack of uniform particles. presence of inerts. etc. created application problems. Compost suppliers cannot expect
supcrintendents to bcar the unexpected costs of having to invest large sumsof capital in new equipment in order to
be able to apply their product. This is assuming that the turf maintenance industry even has equipment available to
the marketplace that is spccifically designed to alleviatc such dilenunas. Also, with any product that is to be
topically applied. uniform spreadability is necessary to achieve the most eflicient results. And, when a material is
most beneficial to plants when it is made available in the root zone in a timely fashion, the material should be
processed so it can bc applied in a way that will facilitate movement into the soil rhizosphere.
Particle size. uniformity, and moisture content are characteristics that influence utility. Uniform particles
screened to at least 0.6 cm ( 1/4-) in size or less is imperative if the amendment is to filter throughleaf tissues and
tllatch. down into 1.2 cnl to 2 . 5 cm (1/2' - I' ) diameter aerifying holes. The material must be dry enough to avoid
plugging as well. The longer the nuterial remains above the soil rhizosphere, unsatisfactory aesthetic conditions
are caused and excessive wear to mower reels create other unacceptable costs. As can be seen, the biological
benefits that organic soil amendments such as composts can provide do not necessarily narrow the cost/benefit ratio
enough to justify includingthem in ongoing landscape management operations.
0 -
7
E
Use of a Prclimm~nC V S u n w for Market Valuation
A peliminary CV suney was also a component of this operational research protocol. Table 4 summarizes
the illlormation presented i n the survey about the characteristics of the commodities to be valued. The
supcnntendents that participated in the survey gave very similar responses. In general the respondents indicated
they would be WTP $10-$12/yd3 for bulk materials but only for products that were uniformly screened at a
minimum of 0.6 cm (l/-Ij: dry enough to avoid application problems (z20% moisture); and assured not to contain
concentrations of pathogens, viable weed seeds. or trace metals that could become problematic over time. The
consensus also indicated a WTP of an addilional $2/yd3 if research demonstrated that the specified compost had
positive effects on disease suppression and that repeated use would safelylead to an eventualreduction in inorganic
fertilizer and pesticide inputs.
When asked to value compost based on N content alone, respondents were not WTP more than the
equivalent of 35“ Ab. N as an added fertility value of the amendment. Nearly all of the respondents stated that they
would not tolerate a topdressed material visible on the greens for 24 h or ontees and fairways for > 48 h. both
conditions lead to a declille i n their valuation of 50-75%. The presence of inerts decreased the value of the
compost by 25%. The presence of a moderate odor decreased the value 10-50%, whereas most individuals stated
they would not even use a material with a strong odor.
Participants were also asked to respond to the following statements:
1 ) Recognizing the peat availability is becoming more limited over time and that the cost of peat is averaging
$2.00/ft3 (= $50/yd3),would you be willing to use morecompost as opposed to peat in construction activities if you
knew there was little risk of adverse effects? Most of the respondents said they would use more compost but in no
instanGe would pay the same amountfor compost as for peat.
2) Assuming you know all of the previously discussed benefits would be gained by the use of your selected
compost amendment. what concerns associated w i t h the increased use of compost as a soil amendment in your
operation would you maintain’? Respondents listed the need for more research, quality assurance andtosicity risks,
storage and delivery logistics. and etrect on mowing units.
I n particular, some of the highly educated and proactive superintendents thatI discussed this nlarket
opportunity with at great length (includingthose participating in the field trials), expressed much the same
concern. In summary, they felt that there is a lack of research data concerning the longterm environmental effects
of repeated compost applicationsas well as on the short term plant effects; and that quality assurance andproduct
consistency, including questionable laboratory analysis accuracy, are concerns. Two respected superintendents
wrote the following comments, “material is more diEcuIt to handle andapply, therefore it increases my actual cost
to use”. “would use only if screened down to match particle sizeof topdressing s a n d , and “cost not a determining
factor the quality of the product is”. When it comes to management of golf course greens, the latter statement is a
rule of thumb in the business.
-
Market Potential
Assuming that producers of compost are capable of and committedto providing the quality materials that
green indusfty consumers demand, the market and revenue potential may be larger than expected. Providing an
acceptable quality compost to superintendents in the Carolinas alonecould result in a market for approximately
619.000 yd3 applied on tees and fairways using the lowest rate tested in my research (0.4 yd3/1000 ft’). For a
compost soil amendmellt with a bulk density of 0.4 ton (363 kg/yd3), nearly 250,000 to 500,000 tons of recycled
organic materials could be utilized in golf course maintenance activitieswithin this region. Lfthis application was
made only once per year the revenue potential in this region, assuming aWTP of $10-12/yd3, would be $2,500,000
to $3,000,000 from the golf industry alone.
It seems apparent that the compost industry. urban landscape planners. and communities would benefit
from more research cllbrts designed to develop and facilitate marketsfor high quality compostsoil amendments.
By devising a sound market development scheme. assessing the niche ‘fit’, analysing the costs and benefits by
using both scientific field data and survey methodology, green industty markets for high value composts can
succeed.
Table 4. Description of the commodity superintendents were asked to value in terms of their
(WTP) in preliminary survey.
~~illingness-to-pilv
Assume that compost materialscan be processed and made available to you with the following characteristics: .(
macro-nutrient content of N = 2%, P = 1.5%, and K = 1%
.I organic matter content of ~ 0 %
./ pH from 6.2 to 7.2
.I moisture content or25%
4 hea\y metal contents < pollution concentration limits as set by EPA for sludge
.I pathogen levels also meet EPA Scction 503 sludge requirements
4 free of viable weed seeds
References
Dum. W.N., R.E. Basom and C.D. Frantz. 1988. Educational policy analysis: A guide to applications. Andover.
MA: The Network pp.20-37.
Mitchell, R.C. and R.T. Carson. 1993. Using surveys to value public goods: The contingent valuation method.
( S . Allen ed) Resources for the Future. Washington D.C.
Pearce, D., D. Whttington, S . Georgiou, and D. James. 1994. OECD Documents - Project and policy appraisal:
Integrating cconomics and environment. OECD Paris, France.
Sugden. R. and A. Williams. 1978. The principles of practical cost-benefit analysis. Oxford University Press, Inc..
New York
EVALUATION OF A COMPOST BASED POTTING MIX FOR COMMERCIAL NURSERIES
Frank Franciosi
R.T.SoilSciences
Rocky Mount, N.C.
Ted E. Bilderback
Department of Horticultural Science
Raleigh, N.C.
William G. Lord
North Carolina CooperativeExtension
Franklin County, North Carolina
LouIsburg, N.C.
INTRODUCTION
Composts have been used by gardeners for centuries, however commercial nurserymen generally have not
used composts in potting mixes due to the lack of available uniform product and few guidelines onrates and
management practices for commercial potting mixes. Leo Bennett, ownerof Cedar Creek Nursery, Louisburg,N.C
began blending a composted product available from R.T. Soil Science of Rocky Mount, N.C. at a 1:1 by volume
ratio Into his standard pine bark and sand potting mix. The new potting mix provided a savings in potting mix
costs. plants seemed to be less moisture stressed between irrigations, and plants seemed to grow well in the new
mix. However. Leo was not sure he was getting optimal growth with the new blend and wondered if the weight
(bulk density)could be reduced consequently reducing the weight of the conmners.
The R T Soil Sciences compostwas an 85% (by volume) organicfraction of approximately equal volumes
of composted cotton gin stems andhulls and composted hardwood fibers and a 15% by volume fraction of fly ash.
Fly ash composts have been used previously as components of container substrates andprovided good results (Butler
and Bearce. 1995; Bilderback et.al. 1990). Greenhouse Rose’s in the Butler and Bearce study had equal flower stem
lengths. flower bud size and numbers of flowers produced as the control substrate containing no fly ash and stem
fresh weights of flowers in the ash:bark media exceeded those of the soil:sand:peat (equalvolumes) control substrate.
Bilderback et. al. had similar results among substrates tested where Rhododendron ‘PI” had a larger growth index,
bud count and visual rating for the pine bark:sand:fly ash substrate than the 5 pine bark:l sand standard potting mix.
PURPOSE AND GOALS OF PROJECT
With interest in optimizing growth and production efficiency, Leo Bennett contacted theCooperative
Extension Service and a protocol for a study was developed in cooperation with Ted Bilderback and Bill Lord of the
North Carolina CooperativeExtension Service , Leo and Katrina Bennett of Cedar Creek Nursery, Louisburg, N.C.
and Frank Franciosi of R.T. Soil Sciences, Rocky Mount, N.C. The objectiveof the container substrate evaluation
was to determine the physical and chemical characteristicsof test substrates and evaluate growth responses of two
nursery crops to four container potting mixes.
102
Test
Substrates
Tablc 1
Substmtc
-
and amendments.
Description
3PB:?RTC:1 S
CEDAR CREEK Standard: Composed of 2 parts Pine Bark : 2 parts R T Soil Sciences Compost
and 1 part Sand (by volume). The Cedar Creek Standard Substrate was amended with 1.7 Ibs of
CaSOd yd3 ( 6 #/7 yd3) and 0.9 Ibs./ yd3 (6# / 7 yd3 )C-Trel. Woodace 20-5-10 Controlled
Release Fertilizer was surface applied atthe rate of 54 g product / 3 gallon (10.8 g N) / contamer.
IPB: IRTC
Pine Bark : R T Soil Sciences Compost (5050 by volume). Substrate was not amended during
mixing and potting but 5.6 g C-Trel was applied to the surface of the container and then feathered
into the substrate by hand after placing containers in the test area. Woodace 20-5-10 Controlled
Release Fertilizer was surface applied atthe rate of 54 g product / 3 gallon (10.8 g N) / contamer.
3PB: IRTC
Pine bark : R T Soil Sciences Compost (75:25 by volume). Substrate was not amended during
mixing and potting but 5.6 g C-Trel was applied to the surface of the container and then feathered
into the substrate by hand after placing contamers in the test area. Woodace 20-5- 10 Controlled
Release Ferulizer was surface applied atthe rate of 54 g product / 3 gallon (10.8 g N) / conmner.
RTC
R T Soil Sciences Compost ( 100% by volume). Substrate was not amended during mixing and
potting but 5.6 g C-Trel was applied to the surface of the contamer and then feathered into the
substrate by hand after placing containers in the test area. Woodace 20-5-10 Controlled Release
Fertilizer was surface applied at the rate of 54 g product / 3 gallon (10.8 g N) / container.
(100%)
PROCEDURES
Two nursery species: Ilex vomiforia ‘Nana’ , Dwarf Yaupon and Ilex cornufa ‘Burfordi Nana’. Dwarf
Burford Holly were selected for the study and potted into 3 gallon containers. Plants were placed in a completely
random block design in 10 replicated blocks of each species. All cultural practices including, irrigation, fertilizer,
and minor element supplement were those of Cedar Creek Nursery. The containertest substrates and amendments
added to each are shown in Table I .
Data collected and analyzed during the study included physical properties and nutnent analysisof contamer
leachates at the initiation of the study, and after 4,8,12and 16 weeks and foliar analysis collectedat the termination
of the study in September 1995. C o n m e r leachates were collected following the Virginia Tech Extraction Method
procedure. Following this procedure, approximately 2 hours after irrigation,about 500 ml of irrigation water was
poured over the surface of the container and the leachate expelled was collected in a shallow my, transferred to a
sample bottle and refrigerated until transported to the Horticultural Substrates Laboratoryin Raleigh for N03-N,
NH4-N. and P analysis using a spectrophotometer (Spectronic 1001 Plus, Milton Roy Co., Rochester, N.Y). Three
irrigation samples were collected for comparison on each sampling date.
To determine physical properties, 5 pots of each substrate were fiiled and included in the study as fallow
pots without plants. At the end of the study, these pots were transported to Raleigh to the H o ~ c u l t u r a Substrates
l
Lab and physical property evaluations conducted to determine Total Porosity, Air Space, Container Capacity.
Available Water, UnAvailable Water Content and Bulk Density.
Table 3. Physlcal properues o f selected substrates.z
Substrate,’
Water
TotalConmner Au
Water
Poroslty
Capacity Space
Available
Unavailable
(% Volume)
0.43
7.7
67.0
79.3
22.85
PB: RTC:S
43.2
66.0
83.0
IPB : lRTC
70.8
68.0 3PB :1RTC
18.3
86.3
RTC
13.8
80.6
Normal 25.0-35.0
25.0-35.0
0.19-0.52.0
.050.0-85.0
10.0-30.0
45.0-65
Ranges for
Pine Bark : Sand Substrates
Bulk
Density
(g/cc)
13.3
12.2
1
0.3
28.2
42.6
(% Volume)
(g/cc)
ZAll analyses performed using standard aluminum soil sampling cylinders (7.6 cm ID. 7.6 cm h).
Air Space and Container Capacity affected by height of contamer.
RESULTS
Total porosity , air space and conmner capacity were less in the Cedar Creek standard mix than other
substrates tested, due to the addition of sand (Table 2). Sand increased the weight (bulk density)but also tended to
increase the available water capacity by decreasing unavailable water. Addition of each increment of pine bark
increased total porosity. Air space and container capacity as well as available and unavadable water were dependent
upon the volume of pine bark added. The 100% R.T. Soil Sciences Compost had physical propemes most similar to
the Cedar Creek standard .
All Substrates were within guidelines for total porosity, air space and bulk density when compared to
standards developed for pine bark and sandcontainer mixes. However test substrates exceed normal ranges for pine
barksand contamer capacity and available water capacity values. This suggests that in regard to Physical Properties
all four substrates couldbe used to produce plants in containers if irrigation management was tailored to the substrate
where excessive watering whch could reduceair space below desired m g e s was avoided.
Initial pH varied considerably among test substrates and no statistical differenceswere established (Table 3).
The 100% RT Compost tended to have the highest pH initially and throughout the study. The Cedar Creek standard
maintamed pH within guidelines for good plant response throughout the study. The PB:RTC (1:l) substrates
maintamed a higher pH than the 3: 1 or the Cedar Creek standard. This may have been due to the high conmner
capacity (Table 2 ) which provided more water for acidity and alkalinity reactions to occur within the substrate. The
3: 1 PB:RTC maintamed pH levels similarto the Cedar Creek standard.
Conductivity levels(EC) were initially above suggested ranges (0.5 to 2.0 mmhoskm) as expected ~n
unieached contamers immediately after potting ( d a t a not shown). Leachates 4 through 12 weeks remained above 0.5
mmhos conductivity for all substrates and were considered acceptable for plant growth. After 4 weeks, conmner
leachates conmned acceptable to high levels of nitrate nitrogen (74 to 108ppm ), the 100% RTC had the lowest
NO?-N but was within the suggested range (50 to 100 ppm) (Data not shown). Nitrate nitrogen levels for all
substrates were statistically similarand acceptable at 8 and 12 week, and all were below optimal levels for producing
rapid growth at 16 weeks. Ammonium nitrogen levels were consistently low but were not different among
substrates.
Table 3. Conlamer leachate pH from 4 substrates on 6 sa~nplingdates."
Sampling Dates
(Weeks after potting)
12
Substrate
4
PB:RTC:S
6.7ab
6.9a1PB : 6.4b
IRTC
3PB :1RTC
6.3b
RTC
0
6.
5.9
6.7a
6.2b
ns
5.9 6.4b
16
18
ns
l6.2b
b
6.4b
7.3
6.66.lb
6.lb
7.8 8
7.2a
5.5
.Oa
7. l a
7 .Oa
5.8
"Suggested pH 5.2-6.5 for VTEM leachates. Each value represents the mean of 3 leachate samples.
Phosphorus IS difficult to mainan in organlc substrates since soluble phosphate leaches rapidly
during
lrngation and is not fixed by organic potting components. Recommended levels ( 15 to 30 ppm) in leachate solution
have been reduced to 10 ppm in recent Best Management Practices publications to reflect levels often present when
tested. All though P concentrations in the 100% RTC substrate were generally below guidelines, the other
substrates maintained concentrations higherand within suggested guidelines(Data not shown). In fact. the PB:RTC
( 3 :1) and the Cedar Creek Standard maintamed adequate P throughout 16 weeks of the study.
Tissue nitrogen, potassium , magnesium and iron, 18 weeks after potting were within acceptable guidelines
for all four substrates (Table 4). Tissue phosphorus was within guidelines but somewhat low for all test substrates
which is somewhat surprisingsince solution concentrationswere maintained near optimal levels in the PB:RTC
(3: I ) and the Cedar Creek standard. Calcium was evidently available in hgh levels and therefore was absorbed in
large amounts from all four substrates.
Manganese and Zinc levels were extremely high in tissue. Hollies are known accumulators of metals
particularly manganese and frequently are shown to have levels in the 1 to 2 % tissue range as high as macronutrients as is the case in this study. The high Mn and Zn levels do not appear to have created any antagonisms,
primarily because high levels of Ca and Fe were also availableand absorbed in large amounts. If high Mn and Zn
levels were considered to be creating problems, dropping the micro-nutrient package at potting would seem advisable.
The only minor element which might need to be supplemented when the RT Compost is utilized might be copper
although no tests were run in this study to determine copper levels orneed for other elements.
The growth indexes, a measure of plant diameters (maximum- minimum/ 2) plus height (thesum divided
by 3) were similar for the Cedar Creek standard,and the Pine Bark : RT Compost substratesboth 1:l and 3: 1,
however the 100% RT Compost had a lower growth index than the PB combination mixes (Table 5 ) . The same was
generally true of the height measurements, exceptthe PB :RTC 1:l and 100% RTC were the same.
Table 4.Effect of substrates on flex cumura 'Burfordii Nana' holly foliar nutrient levels at the end
olIhe growmg season.z
Container
Substrate
P
N
K
Zn Ca
Mn
Mg
Fe
(56 tlssue
(PPm)
dry weight)
ns
ns
PB:RTC:S
2.lbc
ns
0.2
2.0
1.3ab
0.3 1319.7a
2432.7a
172.0a
1PB : lRTC
2.oc
0.2
2.0
1.2b
0.3
1484.0bc
122.7b
773.7b
0.2
2.0
1.3a
0.3
2268.8ab
156.5ab
815.0b
3PB2.2ab
:1RTC
RTC
3.2a
0.3
1.9
1.2b
0.3
124.7b
1115.0~
532.7~
sufficiency
1.83.8
0.151.0
1.02.0
0.21 .o
0.20.8
35.0250.0
50.0200.0
50.0200.0
levels
L.
Each value is the mean of 3 foliar samples
CONCLUSIONS
The significance of this study to Leo and Katrina Bennett and the nursery industry is that plants grow well
the compost substrates and using the compost can reduce costs of potting mixes. In the test less growth occurred
in the 100% RT Compost which had less desuable air and water relationships and nuuient capacity characteristics.
The compost benefitted from the addition of pine bark and related to plant growth benefitted greatest with the addition
of 3 parts pine bark to 1 part RT Compost. Although the Cedar Creek standard potting mix was quite acceptable.
removal of the sand increased growth and reduced handlingeffort and shipping costs.
In
LITERATURE CITATIONS
Bilderback. T.E., Everette F. Hartzog and Rob Means. 1990. Use of Composted Fly Ash and Pine Bark as a
Potting Medium. Proc. SNA Res. Conf. 35:76-79.
Butler. Susan H. and Bradford C. Bearce. 1995. Greenhouse Rose Production in Media Containing Coal Bottom
Ash. J . Environ. Hort. 13:160-164.
Table 5 . Growth lndex and Plant Height of Ilex comufu ‘Burfordii Nana’ holly
as affected by substrates.
Growth Indexy
Plant Height
(m)
b
M.Oa
PB:RTC:S
7 1.Oa
1PB :IRTC
66.1ab
3PB : 1 RTC
75.6a
RTC
51.lb
“Mean separation by Duncan’s Multiple Range Test 5% level. Each value represents the mean
of 10 plants.
Y Growth lndex = Greatest Width + Least Width divided by 2 + height then the Sum divided by 2 .
The measurements were made at the termination of the study on September 29,1995.
57.lb
COMPOST EFFECT ON COTTON GROWTH AND YIELD
By:
Aziz Shiralipour, Ph.D.
Center for Biomass Progmns
University of Florida
Gainsville. Florida
Eliot Epstein, Ph.D.
Canton, Massachusetts
INTRODUCTION
Although there is some use of municipal compost on farms, the utilization of compost is not a standard
practice in commercial agriculture. In order for agricultural markets to develop and make compost use a standard
practice, the agronomic benefits andsafe use of compost application mustbe demonstrated anda cost benefit analysis
developed. Because of the high cost of transportation relative to product value, compost must not only address
agronomic concerns, but also be tailored to specific regional factors.
PURPOSE AND GOAL OF THE PROJECT
The goal of this project was to demonstrate the benefits of compost application in commercial agriculture
for the purpose of securing markets for municipallyderived compost. The project provided comprehensive on-farm
demonstrations of the agricultural use of municipal compost on cotton in California. Althoughthe project was
conducted in California, the concepts, advantages,and utilization of compost for cotton and other agricultural crops
applies nation-wide.
This paper presents the first year’s results of the three-year project which started in 1994.
DEMONSTRATION SITE
The first year of the demonstration tookplace on Torigiani Farm,a large cotton crop farm in the Lost Hills
Valley.Thedemonstrationsitewas
72 acres in size. The size was designed for a side-by-side comparison of
compost application to current agronomic practices.
The demonstrationhighlightedgrowth,
yield, andwater
conservation. The project utilizedyard
wastehiosolids compost produced by San Joaquin Composting, Inc. (SJC) of Lost Hills, California. SJC has been
operating a large-scale yard wastehiosolids composting operation receiving
feedstocks from the cities of Los Angeles
and Fresno, California. Torigiani Farm continued to conduct its regular farming practices in the compost-amended
plots.
The primary concern of the project team was to ensure a quality product that is stable and mature and that
meets the needs of the demonstration and commercial
users. SJC has produced the compost for this demonstration,
transported it to the site, and worked closely withthe project team to insure product quality and acceptabilityto the
agricultural users. Torigiani Farms provide thedemonstration site, carried out all necessary land preparation, planted
the cotton, irrigated the land, maintained the crops, and harvested the crops. Land preparation, planting practices,
and maintenance of the compost-amended portion of the site were conducted exactly the sameas for the rest of the
farm, with the exception of the application ofco-composted yard waste and biosolids prior to planting. The project
team designed the plots, supervised the entire process, and collected both soil moisture and plant growth data.
1ox
T.ABLE I
San Joaquin Compost Analysis
ConstituentsTested
As Received (YO)
Dry Weight
(%)
I
Total Nitrogen ( T N )
I .4
2.1
Organlc Nitrogen [n\r-(NH,N + NO,N)]
I .4
2. I
50.0
34.0
Bulk Density (Ibs/ff)
pH Value
1.5
X
Elecrical Conductivity (EC 1.5 w/w) (mmhodcm)
4.5
67
Total Dissolved Salts ('IDS)
1.6
2.3
Carbon to Nitrogen Ratio [(OMn)/N]
5
X
18
X
Ag Index (<2 = poor;
>IO
= excellent)
METHODOLOGY
Compost TvDe and Method of Preparation
The co-composted yard waste and biosolidswas prepared from source-separatedyard waste collected from
households in the City of Los Angeles and from the Hyperion Treatment Plant. This material was blended and
composted using a mechanically turned windrow system by SJC. The compost produced at SJC was used at the
Torigiani Farms demonstration site, which is located approximately 12 miles from the SJC facility. The compost
with United States Environmental Protection
Agency regulations
product used in this demonstration project complied
to protect public health, safety, and the environment, as stated in 40CFR503. The analytical report of the compost
by the Soil Control Laboratory, a certified laboratory, is given in Table 1.
Compost quality washigh and typical of biosolids cornpost. Total nitrogen, mostly as organic nitrogen, was
1 .J percent and would be released slowly over the growing period, supplementing any inorganic nitrogen applied
as fertilizer. Phosphorus and potassium levels were higher than many biosolids composts. The agricultural index
of 18 was excellent.
Compost Rate and Method of Application
In December 1994, the compost was applied using a hydraulically driven, spinner-type, truck-mounted
manure spreader. After application,the compost was disked into the topsix inches of soil. The compost was applied
at rates of 0, 3, and 6 dry tons per acre (dt/a).
Design of the Demonstration Site
The 72-acre demonstration site was divided into nine equal eight-acre plots. Three plots were randomly
chosen for each rate ofcompostapplication (see Figure 1). Soil type, in general, was loam. Before compost
application, soil samples from all plots were collected and sent to a certified laboratory for analysis.
FIGURE 1
Design of Demonstration Site
Plot I
Plot 3
Plot 4
Plot 5
Plot 6
Plot 7
Plot 8
Plot 9
7 2 Rows
7 2 Rows
12 Rows
7 2 Rows
12 Rows
7 2 Rows
12 Rows
228 Feet
228 Feet
228 Feet
228 Feet
228 Feet
228 Feet
228 Feet
Rate 6 dUa
Rate 6 dt/a
Rate 3 dt/a
Rate 0 dt/a
Rate 3 dt/a
Replicate I
Replicate 2
0 dUa
Rate 6 dt/aRate
Replicate 3
Planting and Growth Measurements
Cotton seeds were planted onApril 24 and 25, 1995, using commercial farming equipmentat a rate of 16.5
pounds per acre. Growth measurements includedheight of plants, number of leaves, number of
branches, length of
branches, number of buds, number of bolls, and yield of crops.
Water Retention Tests
After the heavy rains of January 1995,soil samples from all nine plots were takenfor measurements of soil
as daily measurements of water content for determination of water retention.
water contentat field capacity, as well
One hundred g r a m s from each sample were oven-dried at 103°C for 24 hours. Water was then added to
these soils to bring them to field capacity level; 23 . g a m s of water were required to bring the dried soil from each
plot to field capacity. Two hundred grams of wet soil from each plot’s sample were transferred toa plastic container
weighing 8.7 grams. Daily water loss was measured for two weeks.
RESULTS
Since cotton is not a high-cash crop, the rates of compost application chosen for this project (3 and 6
were low. -Although the rates of compost application were low, incorporation of 3 and 6 dt/a improved the crop
growth, cotton yield, and water retention.
In general, the increases in growth, yield, and water retention were greater in the east ends of the plots in
comparison to the west ends of the plots. This could be due to the higher salt concentrations in the soil in the west
ends. When compost was added, the percentage of increase in growth, yield, and water retention was greater in the
compost
west ends than in theeastends when comparedto the same ends of the controlplots.Apparently,
application was very effective in improving the physical and chemicalproperties of the westends, resulting in great
improvements as compared to non-amended plots.
In addition to improvement of soil’s physical and chemical properties, incorporation of compost into the
soil added a considerable amount of available nitrogen. The available nitrogen from the soil, and then from the
compost after application, was 51 pounds per acre, 121 pounds per acre, and 164 pounds per acre for 0 (plots 2 , 6.
and 8), 3 (plots I , 5, and 7), and 6 dt/a (plots 3, 4, and 9), respectively. These figures were calculatedusing the data
provided by the Soil Control Laboratory and from Table I . Nitrogen added by compost was calculated from Table
1, assuming the rate of mineralization was 15 percent during the first year. Nitrogen from the soil was calculated
using the soil analysis provided by the Soil Control Laboratory (laboratory results not shown). These figures do not
include the fertilizer added by the growers.
Effec; of Compost on the Vegetative Parts of Compost
Cotton Height
The height of the plants increased with compost application during the measuring period (see Figure 2 ) .
The percentageof increase in height ranged from 4.6 to 12.5 percent for the compost application of3 dt/a and from
9.7 to 13.9 percent for the compost application of 6 dt/a.
PLANT HEIGHT - INCHES
25 I
5/9/95
CWPO(IT
APPUCATION
5/31I95
6116/95
MEASUREMENT DATE
7/14/95
Figure 2. Effect of compost applicationon cotton plant height.
111
Plant heights in the east ends of the plots were greater than in the west ends. However, the percentage of
increase due to compost application was greater in the west ends of the plots. The percentage of height increase in
the east ends ranged from 3.6 to 6.6 percent for the compost application of 3 dt/a and 4.5 to 8.2 percent for the
compost application of 6 dtla, while the percentage of increase in the west ends ranged from 5.4 to 14.3 percent for
the compost application of 3 dwa and 14.6 to 21.6 percent for the compost application of 6 dt/a.
Number of Leaves
The number of leaves also increased with compost application (see Figure 3). The percentage of increase
in the number of leaves ranged from 6 . 7 to 10.1 percent for the compost application of 3 dt/a and 8.9 to 23.7 for
the compost application of 6 dtia. The patterns of increase in the east and west ends of the plots were similar to
those of the heighr increase. Since the increase in the number of leaves did not reduce the size of the leaves (visual
observation), the area of photosynthesis increased. This was one of the main factors in growth improvement.
LEAVES
NUMBER OF LEAVES
CwpOsT
APPLICATION
BRANCHES
NUMBER OF BRANCHES
COIPOST
APPUCATlON
"
25
20
15
10
5
n
"
5/31/95
6/16/95
?I14195
MEASSUREMENTOATE
" 6/16/95
a12195
8/21/95
7/14/95
MEASUREMENT DATE
Figure 3. Effect of compost application on the number
of leaves and branches on cotton.
Number and Length of Branches
Since the number andlength of the branches might influence the number of flowers andthe yield of crops,
their measurements were included in this study. Both the number and length of the branches were increased by
compost application. Figure 3 shows the increase in number of branches as a result of compost application. The
percentage of increase in the number of branches for the compost application of 3 dt/a ranged from 7.5 to 20.0
percent, while the percentage of increase for the compost application of 6 dt/a ranged from 12.9 to 20.0 percent.
The percentage of increase in the length of branches for the compost application of 3 dt/a ranged from 10.9 to 16.7
percent, while the percentage of increase for the compost application of 6 dt/a ranged fiom 11.9 to 17.6 percent.
Again, the patterns of increase in the east and west ends of the plots were similar to those for number and height
of leaves.
112
TABLE 2
Effect of Compost on Number of Buds'
0
3
6
-
6.50
west ends of plots
5.10
entire plots
5.80
-
east ends of plots
7.40
13.8
west ends of plots
5.30
3.9
entire plots
l
Percent Increase
east ends of plots
I
I
Yumber of Buds**
Collection Site
Compost Rate (dt/a)
1
east ends of plots
6.35
I
9.5
I
7.40
13.8
1
I(
I
west ends of plots
6.30
23 5
entire plots
6.85
18.1
'Measurementdate was 7/14/95.
**Each number is the average number of buds of 30 plants from each end and 60 plants from entire plots.
Effect of Compost on the Reproductive Parts of Cotton
Bud, Flower, and Boll Formation
Compost application enhanced the production
of bud, flower, and boll formation. The percentage of increase
in bud production was 9.5 percent for the compost application of 3 dt/a and 18. I percent for the compost application
of 6 dt/a (see Table 2 ) .
Appearance of the flowers was also enhanced by compost application. The number of flowers increased
by increasing the rate of compost application. Twice the number of flowers were found on the 3 dt/a plotsas
compared to the control, and three times as many flowers were found on the 6 dt/a compost plots as compared to
the control. The percentageof increasein boll numbers ranged from 14.9 to 27.3 percent for the compost application
rate of 3 dt/a and 17.0 to 45.4 percent for the compost application rate of 6 dt/a (see Table 3). Figure 4 shows the
increase in the number of bollsas a result of compost application. The percentageof increase in early measurement
dates is much larger than later dates, which indicates earlier boll productionin compost-amended plots. Increase in
boll formation due to compost application was greater in the west ends than the east ends of the plots.
Crop Yield
Compost increased the cotton yieldsignificantly (see Table 4). The increase is probably the result of soil
improvement and the nitrogen addition to the soil. The percentage of increase for the compost application of 3 dt/a
was 24.4 percent, and the percentageof increase was 37.2 percent for thecompost application rate of 6 dt/a. Again,
the percentage of increase was greater
in the west ends of the plots, while the total yield was higherin the east ends.
TABLE 3
Effect of Compost on Sumber of Bolls
*Each number IS *e average number of bolls of 60 plants from three plots (20 planti from each plot. I O plants from the east ends and IO plants
from the west ends)
WEIGHT - Ibs/plotS
BOLLS
NUMBER OF BOLLS
COUWST
1
fl[
8/21I9
7/14/95 8/2/9! I
MEASUREMENT DATE
300
250
200
150
100
60
0
3
6
0
COMPOST RATE dry to-a
-
Figure 4. Number of cotton bolls and yield from 30 plots.
Effect of Compost on Water Retention of the Soil
Most of the water loss from the soil took place a few days after saturation. For example, over 46 percent
of the soil water was evaporated from the non-amended soil after 24 hours. This loss for soils amended with 3 dt/a
and 6 dt/a of compostwas 45 percent and 43.5 percent. respectively. The water savings in this case was 1.1 percent
and 2.6 percent for the compost application rates of 3 dt/a and 6 dt/a. respectively. Fourteen days later, the savings
were greater: 4.4 percent for the compost application rate of 3 dv'a and 6.8 percent for the compost application rate
of 6 dt/a (see Figure 5). During periods of water stress, the increase in water content could significantly affect cotton
yield.
TABLE 4
Effect of Compost on Cotton Yield*
'Measurement date was I1/30/95.
**Each number is the average weight of
I5 plants from each end and 30 plants from entire plots
FIG. 5: Compost effect on soil water content
60
40
35
1
2
3
5
4
6
'
7
8
9
1 0 1 1 1 2 1 3
Time (days)
0 tonlacre
+
3 tondacre
0
6 tons/
acre
SUMMARY
Compost application to cotton fields, even during the first year, showed an increase in plant growth and
yield. This could be the result of both chemical and physical properties. The nitrogen, which was in an organic
form, was released slowly overthe growing season. This nitrogen supplemented the usual nitrogen
provided through
fertilization. Phosphorus andpotassium were alsoincreased. Compost contains micronutrients whichcould also have
affected plant growth.
Normally, the beneficial effects of the organic matter from compost is not seen for two or more years.
However, there wasan increase in water content for both the 3 and 6 dt/a application rates. Compostimproves soil's
water retention and other physical properties, enhancingroot proliferation and development. The manifestations of
compost on the soil's chemical and physical properties undoubtedly enhanced cotton plant growth and yield.
Composted Biosolids for Agronomic and
Horticultural Crop Production
James E. Shelton, J. R. Joshi, and P. D. Tate
Department of Soil Science
Mountain Horticultural Crops Research and Extension Center
Sustainable agriculture is dependent upon maintaining soil productivity which has been equated to soil organic
content (Tisdale et. al. 1985). Maintenance of soil organic matter is extremely difficult under tilled cropping systems
which increases aeration, hastens organic matter decomposition and facilitates erosion, resulting in physical loss of
organic matter and other soil components. Limited land resources existing in the southeastern United States requires
frequent, if not continuous, production on the same land which has led to a decrease in organic matter, a reduction
In the quality of soil physical and chemical properties and a decrease in yields of tobacco (Miner and Sims, 1983).
The greenhouse and nursery industries have also relied heavily on peat moss for the improvement of container media
for crop production. Peat moss is not an unlimited resource and regulated harvest in some countries has resulted in
increasing price and a significant cost in container media.
Land application of wastewater biosolids is an increasingly popular method of utilizing wastewater biosolid
residuals. However, federal (40 CFR Part 503) and state regulations established metal loading rates which limit long
termuseofland
for this purpose. Increasing urbanization. local political uncertainties, and unsuitable weather
conditions may also limit land application in some communities. Composting of these residuals with carbon sources
such as wood waste would enhance product quality and allow for greater distribution and is a promising solution to
the problem. While the literature is replete with reports on the beneficial uses of wastewater biosolids on various
crops,the reports oncomposted wastewater biosolids are limited (Woodbury, 1992). A literature reviewby
Shiralipour et. al., 1992, reported that the major benefit from the application of compost to soil was derived from
the improved physical and chemical properties related to the increased organic matter content rather than its value
as a fertilizer.
Wastewater biosolids composting using woodchips has the potential of producing a high quality compost with
relatively high nutritive value which could increase soil organic matter and supply nutrients in a slowly available
form. In order to diversify its biosolids managementprogram to meet long-term requirements the CharlotteMecklenburg Utility Department (CMUD) selected composting as a long-term biosolids management alternative and
established a pilot project to evaluate the process and produce compost for crop production research (Huffman et.
al., 1995). The studies reported herein are a part of the CMUD production research component.
Methods
The pilot project composting methodology was an aerated static pile using dewatered biosolids with woodchips
and sawdust as bulking agents (Huffman et al., 1995). The feedstock ratio of compost, used in these studies, was
3: 1 : O S of woodchips, biosolids, sawdust composted for 28 days, using aerated static pile technology, under a covered
open sided facility and then moved to an outdoor location for 30 days maturing. Compost was screened through a
1.27 cmmeshandmet
theClass A pathogen reduction criteria, pollutant concentration limits (PC) and veltar
attraction requirements (VAR) established by EPA for exceptional quality (EQ) compost. Compost also met North
Carolina regulations for unrestricted use.
Compost was analyzed for C, N, P, K, Ca, Mg,Mn,Zn,AI, Cu, Pb, Ni, and Cr by the Analytical Services
Laboratory - Department of Soil Science, North Carolina State University. C and N were analyzed using a PerkinElmer Model 2400 CHN Elemental Analyzer (Perkin Elmer Corp., Nonvalk, Connecticut). P, K, Ca, Mg, Mn, Zn,
AI. Cu, Pb, Ni, Cd, andCrwere determined byICP using a PerkinElmerPlasma
2000 emission spectrometer
following a dry ashing in a muffle furnace at 500°C with dissolution in HCI.
A t u r f typefescue (cv. Bonanza)-bluegrass (standard) seed mixture (9:l by weight) was seeded on 4 cm of
wastewater biosolids compost (WBC) over perforatedplasticat
a seeding rate of 390 kgha".
No fertilizer
amendments were applied until the time of first clipping 24 days after seeding at which time weekly fertilization with
0. 50. 100 m-g kg" N as Peters 20-8.6-16.6 (20-20-20) soluble fertilizer was applied. Two additional clippings were
made 48 and 60 days after seeding. Clippings were oven dried at 50°C and weighed.
Rooted cuttings of dwarf nandina (Nana domesticus L.) cv. Fire Power was set in 2 gallon containers, in a
pinebark compost media containing 0, 25, 50, 75, 100% WBC. Each media combination was fertilized with 3, 6
or 9 kg m-j of Osmocote 18-2.6-10 (18-6-12) (Sierra Chemical Co., Milpatis, CA), a slow release fertilizer mixed
prior to potting. Each treatment was replicated 3 times. After 100 days of growth plant height (ht.), diameter (D)
was measured in centimeters and plant density (d) was rated on a scale of 1-10 by 4 individuals. A growth quality
index (GQI) was calculated as (ht+DR) x d/IOO. Fall color development was rated by 4 individuals.
Rooted cuttings of geranium (Geraniaceae L.) were grown in 2 qt. containers containing media composed of
pine bark and WBC at 0, 25, 50. 75, 100% compost by volume. Fertilizer application rates of 50, 100, or 200 ppm
N solution (as 20-20-20) was applied weekly. Each combination of compost and fertilizer was replicated 4 times.
Growth measurements consisting of height and diameter were taken at 30 and 45 days after transplanting, Bloom
bud stalk counts were also taken at 45 days.
Results and Discussion
The chemical and physical properties of WBC used in the experiments reported herein are shown in Table 1 .
Primary nutrient content were generally higher than other types of compost (Shelton, 1995). Micronutrients and
heavy hetals were generally lower than was reported by Shelton. 1995. for other composts with the exception of Cr.
All metals were below EPA-Part 503 PC limits.
Greenhouse sod production - Seeding germination and early growth of fescue-bluegrass was excellent as shown in
Fig. 1 with the first clipping 24 days after seeding. Fertilizer treatments initiated at the time of first clipping resulted
in a small but not significant increase in biomass production during the following 24 days (2nd clipping, Fig. I ) .
However, by the 3rd clipping, 60 days after seeding there was a significant response to the fertilizer treatments (Fig.
I ) . This growth response suggests a readily available nutrient supply from the compost in the initial growth stages,
which was reduced and adequate levels were not being mineralized for maximum
growth during the rapid growth
stage following the second clipping. Thus, a significant response to fertilizer treatments. Sod wasofacceptable
quality for marketing at the end of the 60 day period.
Based upon the results of these studies, sod production is feasible using compost over perforated plastic or other
landscapefabrics without soilrequirements.However,
these experiments were conducted under greenhouse
conditions andlonger periods mayberequired outside. Although notreported here an outdoor sodstudywas
established using a municipal solid waste compost over perforated plastic. This crop was seeded in October and
harvested in late March.
Dwarf nandina - Figure 3 shows the GQI at 100 days of dwarf nandina grown in pine bark-WBC media containing
3, 6, 9 kg m-' of Osmocote 18-2.6- I O ( 18-6- 12)slow release fertilizer. Increasing the percentage of compost in the
media significantly (P=0.05) increased growth quality. Response to fertilizer rate was dependent on the composition
of the growing media. With media containing 50 percent or less compost a significant growth response occurred
with increasing fertilizer rates except in the standard bark media containing no compost. Media containing 75 or
100 percent compost did not respond to increasing fertilizer rates indicating that mineralization of the WBCwas
releasing adequate nutrients for maximum plant growth.
A desirable red foliage associatedwith this plantwas significantly decreased with WBC or byincreasing
fertilization (Fig. 3). Fall color development is a function of leaf chlorophyll content which isenhanced with
nitrogen addition either from the fertilizer or mineralized from the compost. Thus, the standard bark growing media
with the lowest fertilizer addition resulted in the highest color rating.
1 I7
Geranium - The addition ofcompost to pinebark significantly increasedgrowth of geranium but there wasno
difference due to compost rates above 25% (Fig. 3 ) . Growth response to increasing fertilizer rates were reduced at
increasing percentages of compost with no significant difference above the 50% compost rate. Bloom bud response
to compost additions was significant to both increasing rates of compost and fertilizer up to the 50% compost rate
(Fig. 3). Mineralization of nutrients contained in the compost was apparently adequate to support growth and bloom
budresponse in the 7 5 and 100% compost media.
Conclusion
Woodchipsand sawdust compostedwith wastewater biosolids serving as a nitrogen source produced an
"exceptional quality" compost with lowheavymetal content. Theproductimproved
the rate of sod grownon
perforated plastic as compared to conventionally grown sod and may significantly reduce the rotation time while
utilizing none of the valuable topsoil. As a media component for greenhouse and container grown plants, compost
gave excellent results andacted as a slow release nutrient source whichmay serve as maintenance during the
marketing process which may extend over several weeks or months.
The results of these investigations show that composted biosolids may be used effectively in the production of
agronomic and horticultural crops. Although cost of compost at the national level is erratic at the present time this
is thought to be due to unfamiliarity of producers in how to use the product. Compost appears to be a suitable
replacement for peat moss in the greenhouse and nursery industry and should be available at a lower cost. However.
based upon the potential use of compost as reported by Slivka et. al., 1992, prices may increase as growers learn to
use the product.
Acknowledgements
Appreciation is expressed to the WaterResourcesResearch
institute and Charlotte Mecklenburg Utilities
Department (CMUD) for their financial support and cooperation.
I18
References
Huffman, E.. J. Shelton. and J. Bellamy. 1995. Pilot scale testing of the Charlotte aerated pile compost process.
ProceedingsComposting in theCarolinas Conference. pp 66-76. January 18-20, 1995. edR.K. White, R. Rubin
and F.J. Wolak.
1983. Changing fertilization practices and utilization of added plant nutrients for
Miner, G.S. and J.L.Sims.
efficient production of burley and fluecured tobacco. In:Recent Advances in Tobacco Science #9 Production of
Quality TobaccoLeaf. Symposium 37th Tobacco Chemist Research Conference October 11-13, Washington, DC
pp. 4-76.
Shelton. J.E. 1995. Effect of various feedstocks on compost properties and use. ProceedingsComposting in the
Carolinas Conference. pp 161-170. January 18-20,1995. edR.K. White, R.Rubin and F.J. Wolak.
Tisdale, S.L., W.L.Nelsonand J.D. Beaton. 1985. Cropping systems and soil management. In: Soil Fertilityand
Fertilizers. 4th Edition. Macmillan Publishing Co. New York, NY. pp. 631-676.
Wood6ury, P.B. 1992. Trace elements in municipal solid waste composts: A review of potential detrimental effects
onplants,soil biota, and water quality. Biomassand Bioenergy 3:239-259.
Table I . Characteristics of WBC compostused in these studies.
Parameter
YO
Parameter
C
39.8
B
15.0
N
1.75
Mn
628.7
cu
I 19.2
P
ma
kg"
K
0.3 1
Zn
306.0
Ca
1.56
Pb
24.0
Mg
0.19
Ni
9.7
S
0.34
Cd
1.1
Fe
0.94
Cr
92.7
AI
0.92
Na
275.0
CI
413.0
Soluble Salts
. 10 mmhs cm"
Bulk Density
pH ( 2 : 1 )
0.51 g cc"
6.5
Fertilizer Rate (mg kg -l)
50 I 1 0 0
48
24
60
Days after seeding
Fig. 1. Effect of weekly fertilization, mg kg-'
of N as 20N-8.6P-16.6K (20-20-20),
on growth of bluegrass-fescue sod grown on wastewater biosolids compost.
No fertilizer applied until first clipping (24 days).
121
Fertilizer Rate (kg m”)
9.
8-
Color Rating: 1, Poor; 10, Excellent
7-
2
3
.
I
6-
5-
2 4-
I
8
3210 1.
25
0
50
100
75
YOCompost
Fertilizer Rate ( kg m-3)
05
HI0
HI5
GQI = [(Ht + Wd)/2]*Density/100
0
25
50
75
100
YOCompost
Fig. 2. Effect of media composition (pine bark-compost) andfertilizer
rate on growth quality index and fall color development
of dwarf nandina
I22
250
Fertilizer Rate ( ppm)
0 5 0 a100 M200
200
n
E
150
v
IbD
.-
;100
50
L
0
50
25
O
h
75
Compost
Fertilizer Rate ( ppm)
0
25
50
75
100
YOCompost
Fig. 3. Effect of media composition (pine bark-compost) and weekly
fertilizer rate on growth and bloom stalk countof geraniums
123
PAPERMILL SLUDGE COMPOSTING AND COMPOST UTILIZATION
Gregory K. Evanylo, W. Lee Daniels, and Ren Sheng Li
Department of Crop and Soil Environmental Sciences
Virginia Polytechnic Institute & State University
Blacksburg, VA 2406 1-0403
INTRODUCTION
Economically viable and environmentally acceptable methods
to recycle organic wastes are needed by the pulp
and paper industry. Previous studies have demonstrated the successful utilization of papermill sludge in land
reclamation projects (Bellamy et al., 1990; Pridham and Cline, 1988), as soil amendments for field-grown agricultural
and forest crops (Cline and Chong, 1991; Henry, 1991; Logan and Esmaeilzadeh, 1985), and as potting media, after
composting. for production of container-grown greenhouse and nursery crops (Chong and Cline, 1993; Chong et ai.,
1987; Cline and Chong. 1991).
Papermill sludgeis usually composted in the U.S. andCanada by blending with organic wastes suchas sawdust
and animal manures, placed inwindrows, and allowed to compost for three to five weeks with frequent turning of the
windrows (Campbell et al., 1991; Chong and Cline, 1991; Chong et al., 1991). Completely cured compost that is
acceptable for containerized plant production can be achieved by maintaining the compost in a static phase for an
additiopal four to six weeks with occasional turning (Chong and Cline, 1991).
The Virginia Fibre Corporation (VFC) requested that we monitor the composting efficiency of its combined
primary and secondary dewatered papermill sludge and testthe suitability of the finished product as a soil amendment
and/or as a potting soil substitute. Papermill sludge normally hasa moderate to high carbon:nitrogen (C:N) ratio, which
often requires supplemental N to facilitate complete composting; however, the Virginia Fibre dewatered papermill
sludge has been enriched withN (asNH,OH) to enhance secondary wastewater treatment biological digestion. and the
sludge may not require additional N to complete composting.
PURPOSE AND OBJECTIVES
The purpose of the research was to determine how much, if any, supplemental N is necessary to facilitate
complete cornposting of the VFC papermill sludge. Research wits also conducted to determine the suitability of the
papermill sludge compost as a potting mix constituent. Specific objectives were:
I.
To determine the effect of threerates of NH,NO, as a supplemental N source on the temperature
relationships of composting papermillsludge and on chemical propertiesof the finished compost, and
2.
To compare variousproportionsandsizefractions of composted papermill sludge and a commercial
soilless potting mix as media for plant growth.
PROCEDURES
COMPOSTING STUDY
The composting study was conducted at the VFC production facility in Amherst, Virginia on a Virginia
Department of Environmental Quality-approved clay-surfaced composting pad of low permeability and having a 2%
slope. The downslope boundary of the pad was bermed using scraped topsoil to ensure that runoff was funneled to a
collection point that drained to a retention pond.
ExDerimental desien
Three compost windrow treatments, consisting of papermill sludge plus three rates of fertilizer N, were:
Treatment 1 :
Treatment 2:
Treatment 3:
Dewatered papermill sludge plus no supplemental N
Dewatered papermill sludge plus 30 Ibs NH,NOlper 1000 Ibs sludge (dryweight basis)
Dewatered papermill sludge plus 60 Ibs NH,NO,per 1000 Ibs sludge (dry weight basis)
The ammonium nitrate was applied to the sludge when the windrows were formed. The treatments were
designed to ensure that a wide range of C:N ratios were achieved at the start of composting. Each treatment was
replicated four times and completely randomized within blocks.
Windrow PreDaration
Sludge windrows 12 to 18 feet wide at the base, 8 to IO feet high, and 30-40 feet long were constructed
between 30 May and 1 June, 1995. The windrows were oriented to enable the runoff to drain toward the collection
drain. Nitrogen was applied on June 5 , and windrows were turned initially on the same day. Windrows were turned
throughout the study with a front-end loader.
Monitoring
Temperatures were measured daily with long-stemmed thermometers to determine when windrows needed
turning. The thermometer sensor was inserted about 24 inches below the pile surface at approximately 1/3 of the
distance from the ground to the top of the pile in two locations in the windrow.
Windrows were turned initially whenthe lowest temperature reading exceeded 130°F and the average of the
two readings exceeded 135°F. Water was added to the piles as they were turned to approximate 50-60% moisture
content ;sing the hand squeeze method. Later, windrows were turned and watered after temperature readings peaked
as the windrows decomposed and failed to attain the initial high temperatures. Active composting and temperature
monitoring was discontinued after 129 days (on 16 October, 1995). The compost was permitted to cure without turning
an additional 35 days prior to screening for laboratory testing and for use in the greenhouse potting study.
Analysis
Compost was sampled from each treatment for analysis
of total C, total KjeldahlN (TKN), NOl-N, and NH,-N
at composting initiation(2 June, 1995) and for NOl-N and NH,-N 14 days after composting initiation (2 1 June, 1995).
Finished compost was analyzed for: pH; electrical conductivity (EC); total C; TKN; NO,-N; NH,-N; total P; Mehlich
I-extractable P, K, Ca, Mg, Mn, B, Mo, Fe, and Zn; water-holding capacity; and stability based on reheating potential
(Brinton, et al., 1995).
GREENHOUSE STUDY
A greenhouse container study employing various proportions of the non-N amended (treatment 1) finished
compost and a commercial potting medium (Promix””) was conducted to determine the capability of thecompost to
support plant growth. We measured plant seed germination and growth response to various combinations of sludge
compost and Promix””to assess the quality of the compost.
Plastic pots having a volume of 128 in3 (approx. % gallon) were used to grow four plant species (radish,
snapbean, marigold, and hot green pepper) for yield and growth data in the following soilless media treatments:
1 . Commercial potting mix (Promix””)
2. Composted papermill sludge
a. 2 mm (0.08 in)< particle size diameter < 7 mm (0.28 in)
b. particle size diameter < 2 mm
c. particle size diameter < 7 mm
3. 50:50 mix of Promix””and composted papermill sludge 2a
a. 0 Ibs N/acre
b. 60 Ibs N/acre
125
The growth medium treatment no.3b was the only treatment to receive supplemental N. All treatments were
replicated three times and randomized within blocks fora total of 72 pots (4 plantspecies x 6 growth media treatments
x 3 replicatiens). To equalize the effects of P and K from the growth media, all pots also received P and K at a rate of
60 Ibs P,O, and K,O per acre.
growth media and wateredto attain 90% field capacity
Undrained pots (lined with plastic bags) were filled with
on 20 November, 1995. Eight snapbean and ten of the radish, pepper, and marigold seeds were planted the next day,
and the pots were covered with plastic film to preserve moisture until the seedlings emerged. The film was removed
after emergence, and seedlings were counted and thinned
to two per pot, except for the radish (4/pot). Germination was
assessed for radish and pepper by measuring the percentage of seeds that germinated and emerged from the growth
media treatments within 2 weeks of sowing.
Water loss was replaced by daily additionof water to assure a constant pot weight (60% field capacity). The
plants were harvested at maturity on the following dates: 4 January, 1996 (radish), 15 January (snapbean), 5 February
(marigold), and 8-23 February (pepper). The following determinations of yield and growth were made after harvest:
radish
fresh
roots
and
snapbean
fresh
bean
pod
and
marigold
flower
pepper
fresh
fruit
and
oven-dried above ground biomass weights
oven-dried above ground biomass weights
number and
pedicel
length; oven-dried above ground biomass weight
oven-dried above ground biomass
weights
RESULTS and DISCUSSION
COMPOSTING STUDY
Field monitoring
Temperature patterns resulted in 16 windrow turnings (Fig. l-3), and water was added twice. Frequent rainfall
during June supplied needed moisture, but composting efficiency may have been reduced
by inadequate water additions
during July and August.
Temperatures rose immediately upon windrow formation and maintained those
representative of thermophilic
microbial activity for the 129 daysof the study. The composting rate,as reflected by windrow temperature, was slower
with no supplemental N than with the N additions during the initial three weeks as assessed by the standard errors of
the means (not shown on figures). Temperature did not vary among the three treatments between late June and midSeptember, but windrow temperatures were significantly higher with the highest NH,NO, rate than with the other N
treatments during the last monthof composting. The compost probably had not completely stabilized at the time that
the experiment was haltedas indicated by the windrow temperatures, which exceeded ambient temperatures ( > I 10°F
in all treatments). Furthermore, the final treatment temperatures were significantly higher with the higher N rate
treatments (using standard errorsof the means). The VFC stopped temperature monitoring and windrowturning before
ambient temperatures were reached.
ComDost analysis
The concentration of mineral N in the fresh sludge was low (121 ppm mO,+NH,]-N), but the concentration
of totalN was I .22%. The total C concentration of 50.6% resulted in an initial C:N ratioof 4 1.5, which was higher than
the normally recommended starting C:N ratioof 30: 1 for composting. Thus, supplemental N may have been required
2 and 3. based on starting C and N concentrations
to facilitate optimum composting. Estimated C:N ratios for treatments
ofthe sludge and known additions of fertilizer N. were 22.7 and 15.7, respectively. The effects of N treatments were
evident 14 days after composting initiation as NH,- and NO,-N concentrations increased with the NH,NO, application
rates (Fig. 4). Ammonium concentrations were more than twice as high as nitrate concentrations.
N treatment did not effect the chemical properties
of the finished compost, whose chemical analyses gave the
following values: pH (mean=6.73), TKN (mean=1.75%), NH,-N (mean=l 1 ppm), total C (mean=37.2%), C:N ratio
126
T
m
0
v)
0
T
I27
0
cv
0
0 7
7
T
7
0
I
I
l
l
l
l
o a x
4
0
0
d\O\
a 0
a'
cv
X'
x
T
X
X
0
c9
0
7
128
Q)
/94
x
0
9
0
m
I29
0
N
T
0
0
0
Q)
CQ
Q
cn
T
Q)
Q
cn
I-
z
I30
u)
0
0
0
0
Effect of N rateonelectricalconductivityand
finished compost.
Table 1.
N
rate
(Ibs N/ 1000
Ibs sludge)
0
30
60
Electrical
conductivity
Mehlich I-extractable Cu concentration in
Mehlich I
cu
dS/m
PPm
1.67a
I .60a
1.19 b
0.088 b
0.145 b
0.2 10a
Means within the same column followed by thesame letter are not significantly differentat the 0.05 level of probability
by the Duncan’s Multiple Range Test.
(31.3), total P (mean=0.3 IYo), or Mehlich I-extractable P (mean=214 ppm), K (mean=247 ppm), Ca (mean4136pprn),
Mg (mean=449 pprn). Mn (mean=93 ppm), Zn (mean=26 ppm). or B (mean=4.8 ppm). The C concentration typically
declined greatly, while N concentration increased slightly. Final N concentrations were not significantly different
among treatments despite the differences in the initial concentrations of mineral N. Increased ammonia volatilization
from the high N treatments may explain the equalization of compost N concentrations.
The composted sludge is a fertile potting medium comparedto the Promix””(especially with respect to N and
P), whose C:N ratio and the concentrations of TKN and total P were 64, 0.57%, and 0.12%, respectively. Total C
concentrations were similar(37.2% for composted sludge VS.36.5% for Promix”). Electrical conductivity was reduced
and extractable Cu concentration was increasedwith the highest N rate (Table I), but the values werewithin
recommended standards for high quality growth media.
Reheating potential for the finished compost from the three
N treatments were all between 18 and 36°F above
ambient temperature. This values indicate that the material, while not completely cured, should support plant growth
without phytotoxicity. Therefore, the three N treatments appeared to produce similarly stabilized compost despite the
differences indicated by temperature responses.
Water potential curves for the Promix””, various particle size papermill sludges, and the Promix”-papermill
sludge mix demonstrated that Promix” retained significantly more plant-available water than any papermill sludge or
the Promix”-sludge mix (Figure 5 ) . The composted sludge retains and provides considerably less moisture for plant
growth than does the commercial potting medium.
GREENHOUSE STUDY
Germination data (Table 2) demonstrated that the sludge compost was statistically equal to the Promix” in
terms of providing a medium for initiation of plant growth. The intermediate-sized compost provided adequate seedmedia contact for germination.
The addition of N to the Promix””-composttreatment did not influence yields, biomass production, or other
measured plant parameters for any of the plant species investigated; therefore, the remaining discussion will address
only the effects of growth media on plant parameters.
Potting media treatments significantly affected vegetative and fruit yields and plant
biomass in all species. The
highest radish fresh root yields (Table 3) and snapbean fruit yields (Table 4) were produced in the Promix””. The
and increased snapbean
Promix”-compost mix and the finest particle size compost also gave the high radish root yields,
leaf biomass above the larger particle size compost. Growth and yield differences may have been due to differential
plant-available water related to water-holding capacity and particle size.
131
F
132
L
Q)
U
Table 2.
Radishandpeppergerminationdataforseedsplanted
Sojlless
media
in variousgrowthmedia.
Germination percentage
Radish
I . Promix’”
2. Sludge compost
a.2mm<x<7mm
b.<2mm
c.<7mm
3. Promix-compost 2a
54
Pepper
95a
1 OOa
95a
65 b
70 b
90a
95a
b
Means within thesame column followed by thesame letter are not significantly differentat the 0.05 level of probability
Table 3.
Effects of growth media onradishroot
yield andtopgrowth biomass.
Soilless
media
treatment
Radish
root
yield
Radish
leaf
biomass
1 . Promix ( 100%)
g/POt
58.5a
@Pot
3.02a
2. Sludge compost (100%)
a.2mm<x<7mm
b.<2mm
c. < 7 mm
3. Promix-compost a ( 5 O : S O )
28.2 b
42.0ab
27.6 b
43.9ab
1.95 b
2.29 b
2.06 b
2.20 b
Means within thesame column followed by the same letter are not significantly different
at the 0.05 level of probability
Table 4.
Effects of growthmediaonsnapbeanfruit
yield andtopgrowth biomass.
Soilless
media
treatment
Snapbean
hit
yield
Snapbean
leaf
biomass
1 . Promix
dP0t
69.0a
dP0t
13.5a
2. Sludge compost
a.2mm<x<7mm
b.<2mm
c. < 7 mm
3. Promix-compost a
34.6 b
40.2 b
45.6 b
64.1 a
6.74 b
6.14 c
8.91 bc
12.lab
Means within thesame column followed by the same letter are not significantly different
Table 5.
Effects ofsoilless media on marigold flower number, pedicel length,and biomass.
Soilless
media
rreatment
1. Promix
7 . Sludge compost
a.2mm<x<7mm
b.<2mm
c. < 7 mm
3. Promix-compost a
Marigold
flower
number
Marigold
pedicel
length
Marigold
leaf
biomass
no./pot
24.8a
cmlflower
3.04a
dP0t
7.63a
18.3 b
15.5 b
15.8 b
17.5 b
2.72 b
2.76ab
2.58 b
2.65 b
3.98 b
3.78 b
3.87 b
4.30 b
Means within the same column followed by the same letter are not significantly different at the 0.05 level of probability
Table 6.
.
Effects of soilless media onpepperfruitnumberand
Soilless
media
treatment
1 . Promix
2 . Sludge compost
a.2mm<x<7mm
b. < 2 mm
c. < 7 mm
3. Promix-compost a
Pepper
Pepper
fN it
number
biomass
yield, andbiomassproduction.
Pepper
h i t
leaf
yield
no.ipot
10.0
gipot
16.0 b
g/POt
1 1.7a
7.75
11.0
9.00
13.4
24.6 b
59.4a
39. lab
69.9a
4.16 b
12.7a
12.4a
16.0a
Means within the same column followed by the same letter are not significantly different
Marigold flower number, pedicellength,and topgrowth biomass were highest withthe 100% Promix”
treatment, and plant parameters were reducedin all treatments that includedcomposted sludge (Table 5). Lower water
availability may have reduced composted sludge treatment yields.
Pepper responded differently to the media treatments than the other plant species (Table 6). There was no
effect of media on the numberof pepper h i t produced; however, theh i t yields were greaterin the compost-containing
treatments than in the commercial potting mix. Pepper may use water
more efficiently than radish, snapbean and
marigold. In addition, the duration of pepper growth is longer than the other species, and the plant’s greater nutrient
requirements may have been better satisfied by the fertile compost than by the unamended commercial potting mix.
CONCLUSIONS
The papermill sludge produced a stable, mature compost although the heating cycle had not plateaued at
ambient temperature. The time required to attain complete composting was longer than expected because the material
was not optimally homogenized (via mixing) and watered. Under optimum conditions, the papermill sludge should
completely compost in 8- 12 weeks.
The major differences between thecommercial potting mix and the composted papermill sludge appeared to
be related to the ability of the media to provide plant-available water and the high
nutrient (especially N) concentration
of the compost. The commercial potting media held more water than the sludge at all water potentials, thus the
commercial potting mix was a more effic~entsupplier of plant-available water. The stability tests, the C:N ratio, and
the nutrient-content indicated that the compost was a high quality, fertile growth medium. The pepper probably
performed better with some compost than in the commercial potting medium alone because the compost was able to
maintain long term nutrient (especiallyN) availability for crop growth. Therefore, the papermill sludge is an adequate
potting medium, but composting should be allowed to proceed until ambient air temperature is attained before the
material is used as a high quality soilless media substitute. As produced, the material is best as an organic fertilizer, soil
amendment, or supplemental nutrient source for potting media. The compost.will benefit from addition of a waterholding materialsuch
as peat moss, butitsown
water-holding characteristics can be improved by greater
homogenization of the sludge during composting, co-composting with other materials that can increase the plantavailable water-holding capacity, and screening the final product.The finer material may be used as a potting medium
and the coarser material as a soil amendmentlorganic fertilizer.
LITERATURE CITED
Bellamy. K.L., N . deLint, N.F. Pridham, and R.A. Cline. 1990. Agricultural utilization of paper mill sludge in the
Niagara area. Proc. 13th Intl. Symp. Wastewater Treatment and 2nd Workshop on Drinking Water, Montreal.
P. 65-8 1 .
Brinton.W.F..Jr..Eric
Evans, Mary Drofher, andRichardB.
compost self-heating. Biocycle 36 ( I 1):64-69.
Brinton. 1995. Standardized test forevaluation of
Campbell, A.G., R.R. Engebretson, and R.R. Tripepi. 1991.Composting a combined RMP/CMP pulp and paper sludge.
Tappi Journal. 74: 183- 191.
Chong, C., and R.A. Cline. 1991. Composts from paper mill wastes. Landscape Trades 13(9):8- 1 1.
Chong, C., and R.A. Cline. 1993. Response of four ornamental shrubs to container substrate amended with two sources
of raw paper mill sludge. HortScience 28:807-809.
Chong, C., and R.A. Cline. 1994. Response of container-grown nurserycrops to raw and composted paper mill sludges.
Compost Science & Utilization, Vol. 2. No. 3, 90-96.
Chong, C., R.A. Cline, and D.L. Rinker. 1987. Spent mushroomcompost and paper mill sludge as soil amendments for
containerized nursery crops. Comb. Proc. Intl. Plant Prop. SOC.37:347-353.
Chong, C., R. A. Cline, and D.L. Rinker. 1991. Organic wastes as growing media. Comb. Proc. Intl. Plant Prop. SOC.
411315-319.
Cline, R.A., and C. Chong. 1991. Putting paper mill waste to use in agriculture. Highlights Res. Ontario 14( l):16-19.
Henry, C.L. 1991. Nitrogen dynamics of pulp and paper mill sludge amendment to forest soils. Water Sci. Technol.
24:411-425.
Logan, T.J., and H. Esmaeilzadeh. 1985. Paper mill sludge evaluated for use in cropland. Ohio Rpt. 70(2)22-25.
Pridham, N.F., and R.A. Cline. 1988. Sludge disposal: Completing the ecological cycle. Pulp and Paper Canada
89(2): 173- 175.
I35
INCREASING INVESSEL EFFICIENCY AT A COMMERCIAL
BIOSOLIDS COMPOSTING FACILITY:
Practical Aspects of Moisture Loss Estimation and Control
Keshav Das,PhD
Department of Biological and Agricultural Engineering
The University of Georgia
Athens, Georgia
Harold M. Keener, PhD
Department of Food, Agricultural and Biological Engineering
The Ohio State University / OARDC
Wooster. Ohio
INTRODUCnON
Throughput at commercialcomposting facilities greatly impact operational costs and the overall success of the
is processed (treated) to a
operation.Throughputis
defined asthe total amount of inputmaterialthat
predetermined level of maturity.Increasingthroughput involves accelerating the process of degradationthus
reducing the total time required to reach the specified maturity level. Numerous factors affect the process of
degradation. Some of these are the material’s moisture content. initial C:N ratio, porosity, operating temperature,
pH and operational factors such as aeration system and frequency of agitation of the bed of compost. Optimal
conditions for composting have been studied and defined in the literature for different types of cumposting systems
and compostable materials(Haug. 1993).
It is well known that a moisture level of 5565% (wet basis) is required for effective composting. Moistures
below this can prevent sufficient microbial buildup and result in poor degradation. Moisture effect on microbial
activity in compost. measured as oxygen uptake rate. has shown that activity increases exponentiallyasthe
moisture level increases up till about 60 %. beyond which activity was found to decrease (Schulze. l%l). The
activity at 60 % [0.756 mg(02)/g(volatiles)-hrl was found to be almmt double thatat 51 % moisture [0.385
mg(Oz)/g(volatiles)-hrl. This study illustrates the importance of moisture to the c a n p t i n g process and shows
that small reductions in moisture can causes significant decrease in activity, affecting the overall kinetics and
economics of the process.
This paper describes work on implementing a protocol to increase the throughput of the composting system at
the City of Akron Composting Facility in Akron Ohio. The facility is a Paygro type invessel system with four
vessels, each 20 feet wide (6.1 m), 10 feet deep (3.05 m) and 720 feet long (219.5 m). A detailed description of the
system configuration and operation isprovided by EPA (1989). Each vessel 720 feet long is divided into 12 zones
of 60 feet each and is aerated by a pair of blowers that supply a total of 5000 ft3/min (2.36 m3/sec) at a back
pressure of 8 inches of water (2 Wa). Air is supplied to a plenum at thebottom of the vessel and flows through the
campostandis vented atthe top of the vessels. Preliminary assessment of the performance of thefacility
conducted in the summer of 1993 showed that rapid dryingof the compost and excess aeration resulted in cooling
of the compost and inabilityof the compost to reheat and undergo recolonization after agitation. It was determined
that to improve the performance of the system it was necessary to raise and maintain the moisture content of the
compost during its time
in the vessels.
Typically materials started compostingin the vessels at a moisture contentof 55-65% (wb) and dried to a level
in the range of 30-40 %
’ (wb) within a period of 7-8 days of c a m p t i n g . Figure 1 s h o w s a typical temperature
profile measured in the reactor during the first 14 days (336 hrs) of compting. The temperature rose rapidly in
the first day and thereafter reduced. Agitation of the bed of compost was performed on the sixth day following
which there was a rapid temperature increase whichwas sustained f a less than one halfday. Thereafter, the
136
temperature in the vessel remained below 25°C indicating very low microbial activity. This was verified be
measuring the volatile solids during the first 15 days of composting.
It was known that moisture was limiting, however there was no easy way to estimate the average moisture
content of the material in the vessel accurately. Hence it was difficult to know how much water to add during
mixing. Direct sampling was the earlier method of choice, but this was inadequate because the samples were
typically taken from the tap center of the bed where condensation occurs and the moisture content was always
measured to be high. As shown later in this paper, maximum drying was occurring along the walls and hence
when the material was agitated and mixed, the resulting moisture content was very low. It was clear that a method
of estimating the total a m m t of water in the vessel would be of great use. This was the motivation towards
implementing the moisture balance method described here.
O I
0
I
48
I
I
I
I
96
144
192
240
Hours of Composting in theVessel, hrs
I
288
336
Figure 1. A representative temperatureprofile within the conpostingvessel d m the fist 15 days of
mposting. T u n 1 was the first scheduled agitation andmixing of the bed pertOnned on the 6th day
(144 -)
In order to increase the throughput of the facility by maintaining umditions optimal for microbial activity, the
following objectives were identified and pursued :
1. Develop and test a protocol for estimating the average moisture amtent in each zone of compost based on
easily measured variables and the use of a psychometric water balance.
2. Calculate the amount of water that must be added to the compost to maintain moisture ata predetermined 55%
level (e.g. 55 %).
3. Quantify airflow non-unifomity in the bed and estimate the amount of channeling.
PREDICTING MOISTURE CHANGES DURING COMPOSTING
To maintain an estimate of the moisture in the vessel at all times a moisture balance around the vessel was
implemented. The theoretical basis of a moisture balance for forced aeration cornposting systems was
mathematically expressed by Keener et al. (1993) as shown below in equation (1):
I37
Where, mwis the mass of water in the c o m p o s t , W,is the humidity ratio of air at the local temperature and the
subscript “as” indicates that the air is saturated. M , is the mass flow of air into and out of the vessel, b,, is the
metabolic output of water, i.e. the amount of water produced per unit mass of dry matter degraded. M, is the mass
of c o m p o s t dry matter in the vessel at any time. The subscripts “in”, “out” refers to the air entering the vessel and
d
leaving the vessel. The - symbol is the differential operator indicating a rate of change of the term operated on.
de
Equation (1) directly gives the rateof change of moisture occurring inthe vessel at a given time. The moisture in
the vessel at the end of the time step is calculated by multiplying the rate of change by the length of the time step
(e.g. one day)and then subtractingthis result from the initial total moisture in the vessel.
Measurement and Calculation Theow
In order to use equation (1) we need to measure the following parameters : (1) inlet air flow rate into the
compost, (2) inletairtemperature,
(3) inlet air humidity, and (4) average compost temperature (underthe
assumption that air exit temperature is equal to the temperature of the c o m p o s t and is saturated with moisture).
Air temperature and humidity was measured using a handheld humidity/temperature monitor, whose probe was
inserted directly into the air flow in the duct. A meter of this type can be bought from a scientific instrument
company for about $300-400 depending on the options available. Compost bed temperature was measured using a
T-type thermocouple insert( a t approx. $20) that was part of the routine data monitoring at the facility. In order
to obtain a good representation of c o m p o s t temperatures it is recommended to measure thetemperature from atleast
three locations at the surfaceof the c o m p o s t and average the values. The mass flowof air was estimated by using
the fan curve (plotof static pressureversus air flow)of the blower which was obtained from the manufacturer. The
static pressure (AP)against which the fan was working was measured using a U-tube manometer ( a t approx.
$15) at a point in the duct workbetween the blowerand the vessel. For a given static pressure the fan curve
provides the volumetric flowdelivered by the fan. This was expressed as an equation and is shown below.
CFMX(4200-(212.5
= 2
AP))
Eq. (2)
The humidity ratio(W,) of the air is calculated by first calculating the saturated vapor pressure using equation
(3) and then using equation (4). The saturated vapor pressure (p,) is a function of temperature of air (T expressed
in K) and is given as(ASAE Standards, 1970):
p,, = exp[- 5800*2206+ 1.3914993 - 0.048640239 T+4.17&4768X10~5 T2
-
T
Eq. (3)
1.4452093X10-8T3 + 6.545%73 InCT)]
and the absolute humidity (mass of watedmass of dry air) is given as a function of relative humidity (Rh) as
(ASAE Standards. 1970):
W, = 0.62198 *
R h * P,,
101325 - Rh * p,,
Eq. (4)
The implementation of the moisture balance in the spreadsheet is performed as shown in the listing below. A
convenient time step for analysis is one day as almost all measurements are made on a once a day basis. Smaller
time steps of a few hours will increase the accuracy of the procedure.
1. Determine the volume of the zone of compost in the vessel (Vol), wet bulk density ( B u l k ) and initial moisture
content (MC,). These are routine measurements madeat most commercial facilities.
2. Calculate the initial mass of moisture (M,) and dry matter (M,) in the zone of intemt. These are,
M, = MC, X Vol X Bulk
M, = (l-MC,)X VOI X Bulk
Eq.
(5)
3. Calculate the amount of air flow that occurred in the specified time step using EQ (2).
Eq (6) is developed from aheatbalance on the compostassuming that heat loss due to conduction is
negligible. Additional details on these equations can be obtained from Keener et al. (1993). Here A N is the
;ass of dry matter degraded in I b s (orkg), M , is the mass flow of air lbm/day (kg/=) and H, is the enthalpy
of the air in Btu/lbm at the air temperature. Subscripts “in” and “out” refer to air entering and leaving the
vessel. The term “h,” is the heat of combustion of the mixture of compostables in Btu/lbm (Jkg). A data base
of values for heat of combustion of various materials is presented by Keener et al. (1993). For the mixture
under study the value of h, was 9OOO BtUnbm (20.9 MJkg). The enthalpy of moist air (HJ in Jkg is
calculated using the following expression:
Specific heat capacity of dry air C, is 1006.9 Jkg. specific heat capacity of moist air C is 1801.0 Jkg(water
vapor). and the latent heat ofvaporization L, is 2502535.3 Jkg(water evaporated). The resultant in H, in J k g
must be multiplied by 4 . 3 1 X l e to convert to Bhdlbm.
5. Calculate the mass of water produced due to metabolic activity. A value of b,, = 0.6 kg of water produced for
every kg of dry matter degraded is accepted in the literature (Smith and Eilers. 1980). Therefore the water
produced AMw+is given as
AM,’AM,
= b,, X
Eq. (8)
6. Calculate the mass of water lost due to evaporative coolingwhich is given as
where the W,’s are evaluated usingJ3q (4) presented earlier.
7 . Evaluate the total water balance, given as
M, (at present time) = M ,(at previous time)+ AMw+- AM,
t
Eq. (10)
Illustration of Calculation
To illustrate the use of the above equations the following calculation scenario is shown based on actually measured
variables inthe system. The compost was to be maintained at a target moisture of 54% (wb) andthere was
360,000 lbs of wet material at 54 % moisture initially in the vessel, and the total air mass flow rate was 86,000 Ibs
(dry air)/day. Air entered the vessel at a temperature of 84.3T and relative humidity of 47.3% and left the vessel
at 166°F and 100% respectively. Use of EQ. (6) shows that a total dry matter loss of 4040.2 Ibm/day occurred if the
material had 4 of 9OOO Btuhbm. The amount of water produced will be 2421.1 Ibm/day (Eq. 8) and the amclunt of
water removed by evaporative cooling will be 30571.8 Ib/day (Eq. 9). Calculation yields that the total amount of
water in the vessel reduced from 194,400 lbs to 166,249 I b s at the end of one day. In this same period the total dry
mass reduced from 165.600 to 161.560 Ibs. Therefore the moisture Content at the end of the first day would be
166.249/(166,249+161,560). which is 50.7 % on a wetbasis. To remain at a moisture content of 54 %. this
reduced dry matter requires 189,657 I b s of water. As the vessel already has 166.249 lbs. the remaining of 23.408
lbs of water needs to be added. This amount equals 2.806 gal of water into the vessel at the end of day 1. This
calculation needs to performed repeatedly till the point where water can be added (i.e. at day 4 or 5 . when a turn is
scheduled).
RESULTS
The above described procedure was implemented by measuring the inlet air temperature and humidity and static
pressure on the fan once a day. Temperature data was accessed from the monitoring and recording system of the
facility. where all the zones in each vessel was monitored and data was sent to a central computer in the control
room.. Table 1 shows the measured properties during the first seven days of composting and Figure 2 shows the
predicted (line) and actual measured (symbols) moisture changesduring composting. The material being
composted was a mixture of biosolids. recycle compost. bark and sawdust in a volumetric ratio of 1.0/2.0/0.5/0.25.
The resultant mixture’s initial moisture contentwas 51.1% (wb).
Predicted moisture contentline
based on measured air and campost properties
Actual measured moisture content
based on samples ohtained from the
tap30cmofthecompostbed
30 !
0
1
1
I
I
I
I
3
4
5
6
Days of Composting, day
Rediied moistwe content line based on measued ai and compost properties. The actual
1
2
Figure 2.
measured values areshown as symbols (filled triangle)
7
0.0
Table 1. Measured temperature and humidities used in the moisture balance calculation and estimation of the moisture
content of the compost in the vessel. No measurement was made on day 4 and 5. The analysis was performed based on
data from day 3 for these days.
Days of composting ->
1
2
3
4
5
6
7
29.8
100.0
Rh.i.
cull
56.1
59.4
40.8
30.1
100.0
%
31.7
50.7
29.4
100.0
73.5
38.6
As seen in figure 2 the predicted moisture levels were within 5 % at day 3 and within 7 % at day 7 . The data used
far these calculations were measured once a day and were rather coarse (Table 1). Increased fiquency of
measurements will increase the accuracy of the prediction procedure.
ESTIMATION OF CHANNELING AND NONUNIFORM AIRFZOW
A commonly foundproblem during sampling of compost for moisture estimation was the non-uniform drying
along the walls. A series of samples along the width of the vessel were obtained to estimate the drying along the
walls. Figure 3 shows the changes in moisture along the width of the vessel over a period of 9 days. The entire
eras-section of the vessel was divided into five regions (left to right) and the moisture was estimated using four
samples from each region.
60
-C Start
h
p
-t
Day 4
-C
Day9
I
55
v
30
f
I
I
I
I
5
3
4
Regions across the width of vessel
Figure 3. Measwed rnoistlre content acrms t h e width of t h e cornpostingvessel. The width betweenwalk is
20 feet and is divided into 5 regions, each fourf e e t wide. Moistlres represent average of 4 samples taken at
diftereni locationswithin each region. Threecuves are moistuesat start of composting, d a y 4 and day 9.
1
2
During the same period the temperature at the top of the compost wasmeasuredin
each of the five regions.
Equations 3-10 described earlier were used with the mass flow of air ( M ,) as the unknown which was calculated
in each case. Figure 4 shows the results of this calculation. The air flow through each of the five regions is
represented as calculated. The numbers that appear as negative do so because of the increase in moisture in these
regions due to condensation. Sections 1 and 5 had the highest flows based on the amount of cooling and drying
observed. The actual numbers indicating the flows do not have quantitative significance. The flows in each region
gives a representation of the relative flows over the width of the vessel.
I41
14000
"c Days 134 -&- Days 4-9
e
12000
9
-
'E
10000
f
8000
'\\\
\\
6000
4000
2000
0
-2000 !
1
1
2
I
I
3
4
5
Reaions across the width of vessel
Figure 4. Estimated adow through eachof h e regions in the crass sedion of the vessel. AiRow was estimated
based on amount of drying obsewved, h e m negative values indicate regionsof higher moisturedue to
condensation. Cuves give relative estimatesof amounts of a i going through each region and do not have an
absolute numerical importance.
This high amountof drymg and coolingofcompost illustrates theamount of air that is channelingalong the walls
of the vessel. This phenomena is enhanced by the shrinkage of the compost as it dries and its moving away from
the wall region resultingin higher porosity in these regions.
SUMMARY AND CONCLUSION
The importance of optimal moisture in camposting has been clearly illustrated in laboratory studies (Schulze.
1%1) and is observed in full scale vessels (Figure 1). In order to increase throughput by eliminating moisture
e
r
f
m
e
d
.The procedure was
limiting conditions a protocol for the implementation of a moisture balance was p
simple to perform,used very minimal instrumentation at very low cost (approx. $500). and took abaut 10 minutes
each day. Over the period of 7 days thepredicted and measured values agreed within 4-7 % (Figure 2). The errms
by increasing the
increasing with time. It is recognized that the procedure can be made considerable more accurate
frequency of sampling and increasingthe number of samples. A step by step procedure and therequired equations
and calculations are presented in this paper. The spreadsheet used by the authors can be obtained upon written
request.
Observation of air flow non-uniformity with increased flows along the walls of the vesselwere verified by
measuring the change in moisture content along the width of the vessel. As evaporative cooling and removal of
moisture through this mechanismis the most dominant process. drier regions will have had more airflow through
them than others. Based on this fact, the moisture balance was perfumed to estimate the mass flow of air in
different regions across the cross section of the vessel. Figures 3 and 4 show the moisture contents and the
estimated air flows. Significantchannelingis seen andthisis a major s a u c e of wasted energyinaeration.
center of the bed. Frequent
Throughput is affected by excess coolingalong the walls and inadequate aeration at the
agitation of the compost bed is one method to overcome this phenomena. Another possibility is the introduction of
baffles along the wall that will divert flow towards the centerof the vessel and prevent air flowing along the walls.
In this project, channeling was documented and quantified. however no attempt was made to prevent or counteract
this. These modificationswill be tested in futurework.
REFERENCES
ASAE. 1970. ASAE STANDARDS. American Society of Agricultural Engineers, 2950 Niles Rd.. St. Joseph. MI
49085.
EPA. 1989. In-VesselComposting of MunicipalWastewaterSludge.
Summary Report - USEPACenter
Environmental Research Information, Cincinnati
OH 45268. EPA/625/8-89/016. Sept. 1989. p 57-74
for
b u g , R.T. 1993. The PracticalHandbook of Compost Engineering. Lewis Publishers.CRC Press. Inc., Boca
Raton Florida3343 1. p 698.
Keener, H.M.. C. Marugg. R C . Hansen, and H.A.J. Hoitink. 1993. Optimizing the efficiency of the composting
process. In: Science and Engineering of Composting - Design. Environmental, Microbiological and Utilization
Aspects. Renaissance Publishers. WorthingtonOH 43085. p 59-94.
Schulze, K.L. 1961. Relationship between moisture content and activity of finished compost. Compost Science
(Summer 1961). p 32-34.
Smith, R.. and R.G. Eilers. 1980. Numerical simulation of aerated sludge composting. USEPA report # EPA600/2-80- 19 1.
LIST OF SYMBOLS USED
Time coordinateused in the differential operators
Mass of water generated by microbial degradationof dry matter, lb/lbor kg/kg
Specific heat capacityof the compost, J/lcg-"C
Volumetric flow of air calculated from thefan curve. f?/min
Enthalpy of air flowing into the compostbed, Btuhb or J/kg(dry air)
Heat of combustion of the compost material, Btu/lb
or J/kg(dry matter)
Latent heat of vaporization of water
Mass flow of air into or out of the compostvessel, lbm/day or
Kg/=
Dry matter of compost, Ibm or kg
Mass of water in the compost. lbm or kg
Saturated vapor pressureof air at the defined temperature, Pa
Relative humidity of the air, %
Temperature of the compost,"C or K (depending on equation)
Humidity ratioof the saturatedair entering or leaving thecompost, lb/lb or k e g
ACKNOWLEDGMENTS
Theauthors areK. Das. Post-doctoral Researcher. Department of Biological and Agricultural -Engineering.
University of Georgia. Athens GA 30602 ([email protected]) and HM. Keener, Associate Professor, Department
of Food, Agriculture and Biological Engineering. Ohio State UniversityDARDC. 1680 Madison Ave., Wooster
OH 44691. This work was performed with the cooperation of the personnel at the City of Akron Composting
Facility and the Kurtz Bros. Composting Services, Inc.. Akron Ohio. The cooperation and work in this project of
M. Tripodi, A. Berger of Kurtz Bros.. M. Sciarini, R. Maas and W.Krieder of OARDC is gratefully acknowledged.
COMPOST STABILITY DETERMINATION
Manning W. McAdams
Environmental Quality Specialist
South Carolina Marine Extension
Charleston, South Carolina
Richard K. White
Newman Professor
Clemson University
Clemson, South Carolina
INTRODUCTION
Composting has become a financially attractive alternative to landfilling certain solid wastes.
Growth in the
compost Industry is creating a greater need for viable markets. Standardsof quallty and consistencyof compost can help
In the expansion of these markets. Additionally, standards in the testing of compost can enhance
process control,
helping make production more efficient.
Characterized by moderate and almost unchanging microbial growth, stabilityis an essential aspectofcompost
quality Low growth rates give benign organisms a competitive advantage over pathogens such as Sulnronellu and
&fhrurn, which thnve m high-growth-rate conditions (Inbar et al., 1990). Also, stability prevents nutrients from
becommg tied up in rapid microbial growth, allowing themto be available for plant needs. Furthermore, stability
prohibits rapid 0, uptake. which can create anaerobic conditions, offensiveodors and heavy metal dissolution.
Though some authors use the terms synonymouslv, stability and maturityare defined differentlyin this paper. For
stability, Haug (1 980) provided a subjective, yet practical definition: “the point at which the rate of oxygen
consumption is reduced so that anaerobic or odorous conditions are not produced to the extent that they
cause problems
with storage and end use of theproduct.” A more theoretical definition mightbe the point where readilydegradable
substrate is diminished so that its decomposition rate does not control the overallrate of decomposition. The rate of
decomposition is instead determined by the rate of enzymatic, macromolecular decomposition. True stability occurs
when microbial activity is assured to continue at a constant, low level. Methods for determining stability should include
the assurance that microbial activltyhas decreased as a result of low concentrations of readilydegradable substrate, not
suppressed from t e m p o r q parameter limitations,e.g., low pH., moisture content, oxygen,etc.
On the other hand, maturity IS defined as the condition where compostposes no adverse effects on plants and is
determined emplrically using bioassays (Chen and Inbar 1993). In view of the larger number of variables, industry
standards for determining maturityare more numerous than those for stability. The decomposition needed reach
to
maturity vanes with the type of plant grown and the particular agriculturalor horticultural practice employed. The
crop’s nutnent needs, resistance to disease, and the time between compost spreading and the
crop planting all affect the
decomposition needed for compost to reach maturity.
Using these definitions, it follows thata compost which is mature is likely also tobe stable. Yet a stable compost
may not always be at a level of maturity adequate for useas a medium for growinga certain species of plant. In this
paper, we will focuson methods for determining stability. However, in manycases these methods can be used as
indicators of maturity after correlating them to conditional- and plant-specific bioassays.
METHODS FOR DETERMINING STAE3ILIlY
Traditibnally, compost producers have relied on the ageof the compost to tell them whenit was stable. Age is a
sub~ect~ve
measurement and requires ample experience and a consistent substrate and process, and it becomes less
preclse when substrates, conditions, and technologies change. The obvious advantages to using age are its simplicity
and low cost.
Temperature is another Indicator. Niese ( 1963) was one of the firstto observe a correlation between temperature
and stability. The correlation was later quantified by Woods End Research ( 1 993). Woods End developed a numerical
ranking system based on maximumtemperature rise after mixing compostsamples in Dewar flasks. The system
resembled the Rottegrad index used in Germany, which related oxygen uptake
to the potential for heat generation
(Jimenez and Garcia, 1989).
A problem with using temperature is the influence of other factors. For example, the addition of water to compost
can initiate displacementof fungi by bacteria. As bacteria consume fungi, they generate heat,causing temperatures to
Increase (Harada et al. 198 1 ). Other factors include pilesize and weather conditions. Properly using the Woods End
method ellminates many of these outside mfluences, however
a disadvantage is still the length oftime needed for the
temperatures In the compost to reach their maxlmum. NormallyI t takes several days. The main advantages to
temperature measurement are its simpllclty and lowcost.
Harada et al. (1 98 1 ) tested chemical analyses methods, including carbon-to-nitrogen (CN) changes. Total carbon
content decreased as CO, evolved; while total nitrogen content remained constant. Thus, the decrease in the C/N
reflected decomposition. Iannotti et al. ( 1 993) found a similar trend in water extract C/N. C/N becomes inaccurate
when ammonia volatilizatlonoccurs causing a decrease in nitrogen. Also, C/N requires laboratory expertlse and
sophsticated equipment for measurement.
Besides temperature and C/N, Harada et al. ( 1 981) also studied changes in cation-exchange capacq (CEC). CEC
not only reflected the decomposition rate, but also dlrectly measured the capacityof compost to holdnutnents. Although
C/N IS more common m the literature, CECpresents an efficient means for measuringdecomposition. The short-cut
method developed by Harada et al. requires mmimal laboratory equipment andexpertise while at the same time being
accurate. CEC will increase as compost approaches stability.
Recently, Dinel et al. ( 1996) determined stability by observing the ratios ofextractable lipids. Using dlethyl ether
(DEE) and chloroform (CHCI,)to extract the lipids,they observed that DEE extracted lipids diminished, while (CHCI,)
extracted lipids stayed fairly constant through the compostingprocess. The DEE extracted lipids represented readily
degradable lipids whch were quickly consumed by themicrobes during decomposition. The (CHCI,) extracted lipids
represented non-readily degradable lipids, which were consumed at slower
a
rate.
The lipid extraction methodhas the advantage that itaddresses the underlying chemistry of stability. Also
according to Dinel etal., the lipid extraction method canbe performed accurately, relatively inexpensively and for all
composts, It also requires minimal laboratory expertise. The extraction process takes 20 hours.
RESPIROMETRY AND OXYGEN UPTAKE
Respirornetnc methods determine microbial activity in compostby measuring oxygen uptake andor carbondioxide evolution (which are on 1: 1 molar basis under aerobic conditions). Michael et al. (1 993) measured carbondioxide evolution in yard-wastecompost. The yard wastewas kept in containers underoptimal cornposting conditions,
temperature, moisture, etc.. Exhaust gases from the aerated compost containers passed through a NaOH solution. The
NaOH was later titrated to determine the amountof CO, evolved. CO, evolution reflected microbial activity.
The advantage of C 0 2evolution is its ability to measure both aerobic and anaerobic activity. Yet, to what extent
each activity adds to total C 0 2 evolution is difficult to calculate. Anaerobic decomposition produces CO, at lower rates
than does aerobic decomposition. In other words, simplv measuring a decrease in CO, evolution might indicate
lncreaslng stability or a shift to moreanaerobic conditions.
Oxygen-uptake rate reflects biologlcal actluty, Ivhlch in turn 1s a functlon ofcondltions and the amount ofreadily
degradable substrate. Pressel and Bldlingnler ( 198 1 ) found oxygen-uptake rates to be highin raw material, as microbes
p e w rapldly from digesting readily degradable substrate. Over several weeks, as readily degradable substrate
dimmished, so did microbial activlty and oxygen-uptake rate.
A number of methods for measuring the oxygen-uptake
rates are available. For example, the standard bottle
method uses dissolved compost in an oxygen-charged solution anda D.O. meter to measure the dissolved02.A
problem with this methodIS that it does not account for undissolved0,. Also, the aqueous environment differs from the
actual composting environment:organisms predominate in solution that are normally not found in less-aqueous
environments. Also the potential exists for oxygen deficiency, microbial shifts, andchanges in water matrix during
slurry preparation (Iannotti, et al., 1993).
The "Warburg"method measures the pressure in a beaker containing compost and alkaline solution. Under the
constant temperature, constant volume condltions, a decrease in pressure indicatesa decrease in 0, concentration. Yet
the apparatus can test only very smallsamples. Finally, low 0, concentrations In the air surrounding the compostcan
effect the slowmgof 0,difision (Pressel and Bidlinper, 198I).
Another apparatus consists of a membrane-covered, Clark-type polarographic probe with a D.O. meter. Samples
are placed In sealed 500 ml Erlenmeyer flasks and kept at 37°C under constant-volume, constant-temperature
conditions. The D.O. meter measures the 0,concentration in the surrounding air. O2concentrations are recorded for
an hour on a volatilesolids basis. Usmg this apparatus to test poultry manure amended municipal solid waste
(MSW),
Iannott~et al. 1993 found specific oxygen uptake rates
of2.0 mg O,/(g VS.hr) for raw and0.5 mg O,/(g VShr) for
stable compost.
Recently, Whlte and McAdams( 1996) measured oxygen-uptake rates in dairy manure solidshedding material
compost usmg an electronlc resplrometer. The resplrometer has a constant volume, a CO, sink and a metered 0:
addition to maintain a constantpressure. Usmg this equipment with the dairy manuresolidshedding substrate, the
specific oxygen uptake rate decreased from1.7 mg O j ( g VS-hr) to 0.74 mg O,/(g VS-hr) during composting.
ELECTRONIC RESPIROMETRY
An N-Con Comput-Ox@ respirometer designed for testing liquids was modified for composting
solids (White and
McAdams, 1996). The new reactors (Figure 1) were glass beakers 7.5-cm in diameter and I-L in volume. Inside, a 5cm segment of PVC pipe supported a round mesh screen on whichthe compost laid. By suspending the compost above
the bottom of the reactor,a plenum was formedin which a magnetic bar rotated to circulateair. The reactor was sealed
by an expandable plumber's plug, and attached to the underside of the plug wasa KOH container. On top of the plug
was a nipple that connected thereactor to the respirometer via an oxygen-delivery tube.
The reactors were kept at40°C by a circulating water bath.The reactors were leftopen for one hour in the water
bath. T h s allowed the compost to reach the temperature of the bath, preventing errors from increased pressure as
temperature increased. The reactors were then capped with the plugs and connected to the electronic respirometer.
Pressure sensors the respirometer detected pressure drops inside the reactors. Once a drop was detected, 0,was
metered into the respective reactor until the pressure returnedto normal. Oygen flow rates were monitored and
recorded on a computer disk every fifteen minutes.
Electronic respirometry had many advantages. It gave consistent results after four hoursof testing (Figure 2 ) .
The oxygen uptake ratedecreases over time, fromday 0 to day 45. White and McAdams discussed the analysis of these
data in detail. The rate of change of oxygen uptake became essentiallyzero near day 30. Using the respirometer was
simple and required minimal technicalexpertise.
Electronic respirometry measured actlvity In real time under controlled, optimal conditions. This gave added
assurance that activity in the composting substrate would not pick up
if conditions changed. In other words it helped
determine whether the declining actlvlty, reflectedby the oygen-uptake rate, was a function of declining readily
degradable substrate or some parameter limitation such as temperature or moisture. This contrasted chemical methods
146
Figurc 1. Rurcbr used measuring 0,uptake of compost
3 8m
0
0
1
3
2
4
5
Hours
Figure 2. Ouygen-Upuke rate for drury-solids compost measured using an N-Con Electronic Respirometer.
SUMMARY AND CONCLIJSIONS
The method for determining compost stability will depend upon the qualitv
of end product needed, the analytical
capability of the compostlng facility and the
experience of the compost operator(s). Table I summarizes the most
common methodsof determming compost stabilityas discussed previously.
As yet, no method for determinlng stabllityIn compost has emerged as an industry standard. Each has its own
advantages and/or limitations. Because the practlcality of a system will depend on thesize and technology of the
operation, more than one stability measurement may be necessary.
What is most unportant is thata concerted effort be put forth to establish some standard for determining
a stable
compost. Already, some state governments have putforth criteria. If healthy markets are to be established and if the
compost industry isto forge its own destiny, it must take the initiative.
Table I Common Methods For Determming Compost Stability
Accuracy Method
&
Precision
Laboratory .
Ability
Time
Very Low
Temperature
1 Varies
Medium
Carbon:Nitrogen (C/N)
Medium
High
Catlon-Exchange
Capacity (CEC)
Medium
Medium
Medium
Carbon-dioxide
evolution
Medium
O\ygen-Upt&e
(Mechanical)
Oxygen-Uptake
(Electron~c)
High
Medium
Comments
Very Low
More of anart than science
+
Slow
I LowMedium
I
Equipment needs vary
Medium
Measure of past microbial
activity
Medium
LowNedium
Measure of past mlcrobial
activity
Medium
LowNedium
Measure of potential
microbial activity
Medium
LowMedium
Drawback: Calculating the
contnbution from anaerobic
Slow
High
Medium Medium
Many different methods
Low
Fast
High initial cost;Good
precision; Integrated into
process control
High
Chen, Y and Y Inbar. 1993. Chemical and spectroscopical analysis of organic matter transformations during
cornposting in relationtocompostmaturity. Dept. Of Soil andWater
Sciences. The Hebrew Universityof
Jerusalem. Sclence and Engineering of Cornposting Design. Environmental Microbial and Utilization Aspects.
Edited by Harry J. I-loitink and Harold M. Keiner, Ohio AgricultureResearch and Development Center Ohio
State University, Wooster Ohio. pp. 55 1-600.
Dinel, H., M. Schnitzer, and S. Dumontet. 1996. Compost maturity: extractable lipids as indicators of organic matter
stability. Compost: Science and Utilization. Emmaus, PA. 4(2):6-12.
Harada, Y.A. and A. Inoko. 1980. The measurement of cation-exchange capacity of composts for the estimation
of the degree of maturity. Soil Science and Plan[ Nutrition.
26(3):353-362.
Harada, Y , A Inoko, M. Tadaki, and T. Izawa. 198 1. Maturing process of city refuse compost during piling. Sod
Science and Plant hirtririon. 271357-364
Haug, R.T andW F. Ellsworth January 1991, Measuring compost substrate degradahility. Biocycle. Ernmaus, PA
32( 1):56-62.
Iannotti, D.A.,T. Pang, B L Troth, D.L. Elwell, H.M. Keener and H.A.J. Hoitink. 1993. A quantitative respirometric
rpethod for monitoring compost stabilitv. Conrpost: Science and Utilizatiorl Emmaus, PA. 1(3):52-65.
Inbar, Y., Y. Chen, Y. Hadar, and H.A.J. Hoitink. 1990. New approaches to compost maturity. Biocycle. Emmaus,
PA 3 1( 1 2):64-69.
Jimenez, E.I. and V.P Garcia. 1989 Evaluation of city refuse compost maturity: a review. Biological CVasle.7.
27(2) 115-142.
McAdams, M.W. Compost stability measurement using oxygen respirometry. Masters Thesis. Department of
Apcultural Engineering.
Clemson
University.
,
Methods of Soil Analvsis Part 2: Chemical and Microbiological ProDerties Second Edition. Soil Society of America,
Inc.Madison, W I . pp.553-559.
Pressel, F. and W. Bidlingper. 1981. Analyzing decay rates of compost. Biocycle. Emmaus, PA 33( 1):66-69
Standard Methods for the Examination of Water and Wastewater. 1989. 17th Edition. American Public Health
Association.Washington, DC.
Whlte, R.K. and M.W. McAdams. 1996. Compost: olygen uptake and stability. Presentation at the 1996 ASAE
Annual International Meeting. Phoenix, Anzona.
Woods End Research Laboratory, Inc. 1993. Compost self-heating flask. An advertisement brochure for an apparatus
that helps determine compost stability through temperature measurement. Mt. Vernon, M E .
THE EFFECT OF LARGE SCALE VERMICOMPOSTING ON A CORPORATE HOG FARM
chns christenberry
MicbaelEdwards
Tom Chnstenbeny
Vermicycle Orgamcs, Inc.
Charlotte, NC
INTRODUCTION
Eastern North Carolina has the largest concentration of lugh densityhog facilities in fhe United
States. These facllities (operations with at least lo00 livestock head per acre) haveposed serious challenges
in the handling of wastes. Currently, themajority of operatlornsimply fill facultative lagoons with
waste. The facultative lagoonsare a cost effective form ofhandhug swine waste, however they have
created environmental concerns. Recent odor c
o
m
p
a
lm
s
t,ground water contamination, and river
contaminahon have prompted both industry and governmentto look for alternative ways
to reduce nutrients.
Vermicycle Organics, Inc.(VO) evaluated several pilotvermicomposting projects to assess the
best managed way to handle swinewastes. In 1994, a 10 acre open field project was concluded after 14
mpnths of study. Due to unsuitableweather and poor end product, the pilotwas rejected as an effective
form of r
e
d
t
i
o
n
.Data conducted from theopen field trial helped in the formation of an enclosed
venniconversion system trial.T h enclosed system trial led to the foundationof current methodsfor
handling livestock waste.
Vermicomposting isthe use of earthworms to breakdown organic nutrients. Unldce commercial
compostmg, vermicompostingproduces a pure, hgh quality organic by-productcalled castings. In several
investigations worldwide, scientists have
i n d n t e d that castings may hold untapped potential as a plant
growth compound.
The first full scale swine remediation operation is located in Wilson, NC, at CloverM Farms.
Tlus operation successfully handles over l0,OOO Ib. of solid swine wasteeach week. The success of this
operation has prompted the construction of several new operations with much larger capacity. Interest in
the operationhas prompted additionalresearch on VO ‘s casting product called Vumicyclem.
PURPOSEAND
GOALS
The purpose of the vermiconversion study was
to determine theimpact on nutrient management,
develop efficientoperating designs, andproduce a marketableend-product at a large livestockfacility.
The objectivesof the project are as follows:
To collect dataon nutrient levels from raw material, lagoons,
and
end product.
To determine efficientmethods of handling raw matenal and finished product.
To design acost effective solid separation
system.
To detemme the marketability of the end product.
METHODS
- Before any data couldbe collected a facility was designed andbuilt to separate waste and enclosethe
vermiconvasion process. An underground sewage pipesystem directs waste from the swine house toa
large concrete pit. Above ground, a platformcontaining a solids separator(Key Dollar, Eugene Oregon)
was constructed. Waste is pumped from the pit to the sepmtor. A press at the end of theseparator
removes excess wattr. Solids are collected after seperation on a 15 x 15 concrete pad. The liquid porhon
of the waste is piped to the facultative lagoon. The separating system isfully automated and managed by
electronic sensors.
Once collected thesolids are tnmported via frontend loader to a 30 X 200 foot greenhouse. "Ius
greenhouseinslaesthatoptimumtempera~aremaintarwdsothatwastecanbehandledinallseesons.
Thegreenhouseumtainsfour6x190x2ftbedsconstructedofcedarboards.Acudomdesignedspreader
delivers waste to each bed. The beds contain thousandsof pounds of redworm (Eisinia fotidae). Worm
populations are maintained at levels to manage the waste stream. Moisture andtemperature are managed
using shade cloth, automaticmisters,
and manipulahng greenhouse c&.
Weekly man hours for
operation are less than eight.
fans.
Each month water samples were collected from the lagoons under the scrutinyby the Soil and
Water Conservation agent (Wilson Dwtrict). Samples were analyzed for nutrientsby NC DeptMment of
Agriculture. Quarterly,s a m p l e s of solidsfrom the concrete pad were analyzed to insure suitable raw
Wt.
Harvesting ofthe end-product is performed bi-monthly. VO uses a specifically designedmactune
&ch lifts and conveys theh
&
e
d
product. The conveyed productis passed through a harvester. The
harvester separates earthwonus from castings. It has the capability of segmeating wonus and their eggs
so
that eggs can be reintroduced to new beds.
The collected castingsare -ked to a facility and tested for NPK levels. Once nutrient levelsare
determined, product isbagged. The larger bags (10 Ib. and 25 Ib.) can be handled by a third party. VO
constructed a bagger for the smaller2 Ib. bags because a thrrd party source was unavailable.
The markassessment was conducted in two phases. Phase one was the development of a
marketing plan whrch includedtof the market ~ ~ U I O ~ Assessment
~ ~ I C Swas
.
using
m v e n t i d market research tools Included in Phase one trials wze the product testing for efficacy.
Nutrient analysis was conducted by NC Department of Agnculhpe. Grow studies weze conducted intwo
commercial g
r
e
e
n
h
o
w in Wayne and Wilson counties
(NC.) The Wilson county trialcompared control
plots to Vermicycle" enhanced plots in the propagation of azaleas. The Wayne county trial compared
Marigold growth versus control.
Phase two was a test market directed at results from phase one. Independent retailers and n h e s
were targeted in the Charlotte (NC) area. Acceptance of retailer and consumer, penetrationof stores,and
sales were the determining criteria for study.
DATA & RESULTS
The ori@ design of placing separation andremedmtim facility at thesame site worked well
however several changeswill be made to future facilitiesbased on information learned from tius trial. Large
central rernedLation greenhouseswill be constructed at sites d~stancedfrom indwidualfarms. 'This will be
done for two reasons,cost andbimntamination concerns. It is more cost effective to place a large
connected greenhouse supplied by multiple sitesthat placing a single greenhouse at each swine farm.
Because disease iseasily spread among livestock, acentral location keeps traffic low at eachfarm thus
reducing the risk of qmadmg pathogens.
The solidsseparation process works well. Ln future,products an auger system will prevent
time
delays in collecting waste. l h s trial proved the reliablty of sensor controlled separation. ' h s eliminates
both VO employees and farm employees in monitoring separation.
6141
Solids
(Collected from pad)
Castings
6003
24522
26549
20493
2 1997
Second, a sigruficant reduction occurred in lagoon nutrients
as a result of solids separatlon.
N~trogen.Zinc, and Copper showed reduchonwhle no changes wereseen in Potassium and Phosphate.
Potash
Phomhate
Nitroeen
3.35
Baseline
4.24
(avg. PPM)
Post Separation
(9 month avg. PPM)
zinc
195
889
103
600
101.81.28
763
coo
1.08
Whlle U u s data IS promismg, I t w i l l need to be followed for another year. It w i l l be necessary to
duplicate this analysis at a hog farm that has a new lagoon. The lagoon m this study IS over five years
old
The marketin , phase of h s project is promsing. Market research revealed that the publlc
a-wareness of castmgs . a d their abilitlesis low. Interest in good quality organic fertilizersIS growmg.
Consumm are confuwd by the many composts and the huge differences in their quality.
VO determined
developmg a successful market would requrre the following:
Proven efficacy
Distancing from the compost market
Presentmg a unique product
Creatmg a strong brand identification
In response to the marketresearch, VO designed attrachvepackapg and trademarked VemicycleTM
and Natures Ultlmate Plant FoodTM.Greenhouse trials showed VermicycleTM
was very efficacious and safe.
Selling materials were designed to assist in presentation.
Armed with Phase one data, VO successfully conducteda market trial. Over 70% of the target
retrulm accepted s b b g VermicycleTM.Thrs was done despitea retad pnce more than hvlce that of
compost. Retailers remarked on Vermicycle'sTMease of use and great quality. B a u s e all product must
pass through the end of a worm, seeds and contarmnatesdo not reach the end product. As tlus paper goes to
P M t , restocbg of i m t d orders is taking place.
CONCLUSION
A l l the objechves of the Vermiconverslon study werem e t . Data collected has allowed VO to
adjust appropnately for new vermiconvemonsites.
I t appears solid separatlonhas beneficial effectson reducmg nitrogen levels in lagoons. Large
concentrations of nutnents are collected in solid form, thus nutrients duenot burden thefacultative lagoon
dynarmcs and may evencause mcreased lagoon efficiency. Data will need to be collected for at least 16
additional months. It would also be beneficial to study a new lagoon and the changes thatoccur by sohd
separatmg from the first day of operation.
Deslgn of the facllity was sufficient.To increase efficiency andaddress disease protect~on,
additional facilitiesare centralized. Separators will operate on ihdvidual hog farms and solids will be
trucked short distances to a large mdh-greenhouse s~te.The buckmg costs are outweighed by the efficiency
benefits. Special hauling and waste delivery vehcles are currently being evaluated.
The marketing datahas been extremely valuable. First, the casting analysishas shown that
V d c y c l e T MIS a quality product. A d d l t i d studres are in progress to determine new bortlculture uses.
Research on &seaseresistance and hormone productmu
is planned.
Next, the market tnal has mapped out how to drstribute Vmcyclem. Nahonwide hstribuhon1s
VO. Add~tiooalmarketing tools such as P.O.P. dlsplays and M advertising "mprugn
are belng planned.
a short term goal of
Years of work and phmmg have been validated by studymg h s large vermicooversion facility.
VO 1s currently starhug operations on facilities 800% larger than th~sfirst project. Tbe might gained by
researchng the Clover M facility is paying off in greatez efficiency at new projects. The data c o l l e c t e d has
also pointed out the ackhtional information thatis still required for successfulcompletion of V O s long team
goal of becoming the leadex in large scale vermicomposting.
Bibliography
Danmn. Charles, The Formation of Vegetable Mould Through The Action of Earthworms., Volume 28
(New York University Ress, 1989)
Jones,Theresa, 'Boom Market Now a Growing Concern,"
(July, 1 9 9 6 ) , page B1
Raleigh News and Observer
Mattern,Vicki,"The OG Guide to Organic Fertilizers," O r g m c G a r d e n i n g g
(June 1996), pp. 55-59.
Riggle, David, "New Horizons for Commercial Vermiculture," BioCvcle
October 1994..pp. 58-65.
. International Symposium on Earthworm Ecology (ISEE 5 )
(July, 1994), Ohlo State University
TRACE METAL UPTAKE/AVAILABLLITY FROM THREE MUNICIPAL COMPOSTS
K. R Baldwin and J. E. Shelton, North Carolina State University
INTRODUCTION
The potential uses of composts as fertilizers andsoil amendments have propelled many studies aimedat
evaluating responsesof crops to these products. One of the greatestconcerns about using compost foragricultural
purposes is the bioavailabilityof contaminants contained in the material.
Researchers have worried about Cd in sludges and compost and the food chain risk associated with land
application of these materials sincet h e 1970’s (Chaney andRyan, 1993). Excessive detary Cd can accumulate
over one’s lifetime in the hdney cortex and cause renal tubular dysfunction(FancoN qndrome), a disease in
which low molecular weight proteins are excreted in urine. Bioavailabilityof Cd contained in compoststo tobacco
plants (Nicotiana tabacum L.) is a part~cularconcern because tobacco is able to absort, Cdwith no major signs of
toxicity (Tancogne et a l . 1988). Schroeder and Balassa(1%1) conducied a survey of sources of Cdintake by
humans and found t o b a c c o contained the hghest Cd concentration of all products tested (1.65 mg kg” or 3 1.2 pg
pack“ ).
Recentl!. Jing and Logan ( 1992) reported on the phytoavailabilityof Cd from Merent sludges where
equal amounts of Cd were applied in each pot. Crop uptake of Cd increased with increasing sludge Cd
concentration. This was explained in terms of the filling of spectfic Cd bindmg sites in the sludge: The
population
of Cd binding sites varies widely in strength of specific Cd adsorption, and as sludge Cd concentrationincreases,
the least strongly bound Cd is more phytoavadable. Evidence i n d a t e d plant uptake of Cd from sludge with low
Cd content was l e s s than that from sludges with hgher Cd content. even if the same total amount of Cd was
applied. These f i d n g s supponed the Corey et. al ( 1987) hypothesisthat plant trace metal uptake is controlled in
part by sludge chermstq. Corey et a l . (1987) concluded that specific metal adsorption on sludge surfaces would
normalb be the controlling factorin metal phytoavailability in soil-sludgemixtures. Citing data from many
stuQes. they c o n c l u d e d that sludges with higher metal concentration cause lugher metal uptake by plants when
equal amount of metals are applied (i.e. Qfferent amountsof sludge dry matter and hence adsorption capacitywere
applied).
The solubility of trace metals increases with decreasing pH. Sanders and Adams (1987) found that as pH
was decreased for each sludge and metal, a thresholdpH was reached below whch metal solubility was sharply
increased Adams and Sanders (19&1) found that the lugher the sludgemetal concentration, the hgher the
threshold pH point of increasing metal solubility.
OBJECTIVES
In western North Carolina, burley tobacco is often grown on steep slopes where soil erosion canbe a
sigtllficant problem. Twenty years ago. additions of organic matter, primarily manures, to these soils was a regular
management practice whch not only provided nutrients tocrops but helped to reduce erosion as well.
lncorpomtion of orgamc matter improved infiltration and drainage potential which
r e d u d runoff. Since that
time, chemical fertilizershave r e p l a c e d manures as principal nutrient sou~cesfor burley crops, organic matter
levels in soils have decreased and erosion has increased. The increasing interest in the beneficialreuse and
potenaal availabilityof composted organic waste materials presentsan opportunity for burley tobacco farmersto
begn again to regularly apply orgamc matter to burley fields. There remain concern, however, about the
availability of trace metals contained in composts
to burley tobacco because tobacco is known to be a metal
accumulator. The objective of this experiment was to determine the plant availabdity
of compost trace metalsto a
burley tobacco crop.
METHODS AND MATE-
SOIL
The soil chosen for the field study was a Dyke clay soil (clayey mixed mesic Typic Rhodudults) located on
the North Carolina Department of Agriculture Mountain Research Stationin Waynesville, North Carolina. An
analysis of the soil is presented in Table 1.
I55
F
COMPOSTS
Three composts were evaluated in this study: 1 ) mmposted municipal solid waste and wastewater
biosolids cornpost (COC); 2) municipal sotidwaste compost (MSWC): and 3) wastewater biosolids compost
(WBC). A chemical analysis of the composts is presentedin Table 2.
The COC was produced by an aeroblc. in-vessel process by Bedminstera Bioconversion Corporation in
Sewer County,T N . The feedstocks for the material were municipal solid waste and wastewater biosolids; and they
were &gested for three days in a Ewesons &gestor, a compartmentallzed r o b q cylinder, and then deposited in
windrows on an aerated curingfloor. The windrows were turned regularly, and cornposting continued on the
computercontrolled aerationfloor for four to six weeks to meet EPA PFRP requirements (Environmental
protection Agency pnw;eSses to Further Reduce Pathogens).. After composting the c o m m was cured on a storage
floor for over one month.
co-sponsored by the Buncombe County, NC, Department of
The MSWC was produced in a pilot
Solid Waste and the North Carolina Cooperative ExtensionS e n i c e . The feedstock w a s municipal solid waste
(MSW) which was minimally presorted to remove undesirable inorganic materials. ground. and placed in
windrows. The windrows were turned weekly to provide adequate aeration. and moisturewas added when needed.
Three month old MSWC was used in the field experiment.
The W C was produced by the Charlotte MecklenburgUtility District. Centrifuged, dewatered ( 18-20%
TS) sewage sludge was mixed with wood c h p s and straw in a ratio of 1 5 : 1, placed in aerated static piles for a
period of 28 days. and then cured for 30 days in an unshelteredarea.
prow
Table 1. Experimental Dyke soil chemical characteristics (mgkg")
in May, 1994 before addition of composts.
N
1600
PH
5.8
Mn
cu
870
26
Zn
Cr
64
Cd
<1
81
Ni
Pb
19
13
Table 2. Elemental compositionof composts. COC,MSWC and WBC, applied to a Dyke
soil in 1994 at 0,25. 50 and 1 0 0 Mg h a " .
C
AI
Ca
Fe
K
Mg
N
P
S
1
36.41
Coc"d
MSWCM 6.41
35.89
wBCd
Cd
Coc"
MSWC"
WBC"
1.79
3.60
1.37
2.77
0.94
1.72
1.42
3.40
1.58
0.38
0.27
0.35
0.3 1
0.26
0.22
c1
Cr
cu
Mn
Ni
Na
737.7
2.9203.0
39.7
5117
6126
370.3
215.0
58.0
1.0
448.7
339.3
602.7
52.723.7
2.1
356.3
140.3
325.0
880.7
173.3
1.31
0.30
2.12
0.26
0.08
O.%
0.70
0.07
0.43
Pb
Zn
18.0 96.334.0
16.3
88.3
499.0
' Co-Composted municipal d i d waste and wastewater biosolids (SevierCo.. TN)
BUBLEYTOBACCOCULTURE
1994: A tall fescue/clover crop was plowed and diskedin the spring, P was incorporated at 56 kg ha",
and the field was harrowed. Twenty-two plots were arranged in randomized complete blocks with four blocks.
Plots measured 3.7 by 10.4 meters. Treatments consisted of: 1) MSWC. COC and WBC applied at 25.50 and
1 0 0 M g ha" (dw)to N-fertilized plots(224 kg ha.' N) without lime (9 plots); 2) MSWC, COC and W C applied at
25. 50 and 100 Mg ha" to N-fertilized plots(224 kg ha" N) h
e
d to bring the pH to 6.5 (9plots); 3) N-fertilmd
(224 kg ha" N) control plots without lime and limed to pH 6.5 (2 plots); and 4)Unfertilized (0 kg ha" N) control
plots Hithout lime and limed to pH 6.5 ( 2 plots). Lime was applied to amended plots at 4OOO kg ha".
Compost was dstnbuted as uruformly as possible to plots by hand and thefield was then d~sked.
Insufficient MSWC was available for 1 0 0 Mg ha" applications to limed and unlimed plots in two replications and
data from these plots has been treated as missing data. Burley tobacco (Mcotrana rusrica L. var TN 90)was
mechamally transplanted in three rows per plot with 1.23 metersbetween rows and 22 plants per row. Mssing
throughout
and/or dead plants were reset w i h n 7 days. Conventional crop management strateges were employed
the growing season (NC Cooperative ExtensionSeMce. 1994), and B was foliarly applied to burley plantsin June.
The crop washand-harvested in September, hung ontobacco sticks, and air-cured in barns at the research station.
1 9 9 5 : FerttliLer and lime treatmentswere reapplied to respechve plots, but compost was not applied.
Burley tobacco (TN 90)was planted on May 30th and managed conventionally. Serious blue mold disease pressure
required addtional sprays of fimg~cidesin 1995. After harvesting theburley leaf was hung on sticks in barns on
the research station to cure.
ANALYSES
$&f: A smnless steel soil probe (2.54 cm &meter) was used to collect a composite sampleof forty cores
from the research field prior to application of compost, N-fertilizer and lime. This sample was air dned and then
ground in a soil grinder to pass a 2 mm sieve. After thorough mixing, a 200 gram subsample wasobtiuned for use
in laboratory analvscs. Total N was determined by Kjeldabl digestion (Bremner. 1%5a)., and total Mn. Cr, Cd.
Cu Ni. Pb, and Zn by aqua rega dgestion (McGrath and Cunlfle.1985). pH by 1 :1 soiYwater volume ratio and
CEC by W O A c at pH 7 (Soil Conservation Service. USDA, 1972).
Soil samples were c o l l e c t e d from harvest rows in May. July. and September of1994 and June. July, and
September of 1995. A W
e
s
s steel soil probe was used to oollect a composite sampleof four cores (20an long
by 2.54 cm in dnmeter) from each plot. Samples wereairdned, ground to pass a 2 mm sieve and stored at room
temperature in soil cartons. Samples were extracted with DTPA at pH 7.3 (Lindsay and Nowell, 1978). Exmcts
were analyzed for Zn. Ni. Cu. Cd and Pb on a Perkin-Elmer Plasma 2000 System inductively coupled plasma
emission spectrometer (ICP).
C'ompust: Approximately 5 kg of each compost was c o l l e c t e d at the time of field application andstored
for three weeks at 5" C. Approximately 0.5 kg of each sample was thoroughly
mixed, and a 0.1 kg subsample was
b
e
d overnight at70" C and then groundin a stainless s t e e l Wiley mill to pass a 2 mm sieve.
A 2.5 g compost subsample (replicatedthree times) wasashed in a mufne furnace at 500' C overnight.
Two ml of &stilled H20and 4 ml6N HCI was added and the subsample heated on a steam
The subsample
was brought to volume in a 50 ml volumetric with distdled water and analyzed for elemental content(except N)
w~ a Perkin-Elmer Plasma 2000 inductively coupled plasma emission spectrometer. Compost N concentration
was determined with a Perkin-Elmer PE 2 4 0 CHN Elemental Analyzer.
Tobacco: Tobacco leaves were c o l l e c t e d from growing plants inJune. July, August and September of
1994. Ten most-recently-matured leaves were stripped from ''guard rows" adjacent to the center "harvest row'' in
each 3-row plot. Leaves stripped in June were rinsed with distilled water before drying; leaves stripped in other
months were dned without rinsing. Cured leaf samples (composited by weight from all stalk positions) were
b n e d by subsampling fromcured hands at @ng. All leaves were dned at 70" C, and then ground in a
stainless steel Wiley mill to pass a 1 mm sieve. Ground samples were stored at room temperature in acid-washed
glass jars.
Ten leaves were stripped from guard rows in June. July and August of 1995. In June, most-recentlymatured leaves were rinsed in &stilled water before d y n g at 70' C. In July and August. IO plant leaves were
stripped from two stalk positions: most-recently matured leaves ftom the upper part of the plant and mature leaves
from the lower part of the plant. near the stalk position where a leaf had been collected in June.. These leaves were
not rinsed before d y n g at 70" C . Cured leaf samples from upper, middle, and lower stalk positions were
subsampled from curedhands at grading. Dried samples were ground in a stainless steel Wiley mill to pass a 1
mm sieve and stored in acid-washed glassjars at room temperature while awaiting laboratory analysis. Dned plant
samples were analy7zd as per 1994.
Stafistrcs: Compansons between means were made using a general linear modelsprocedure in the
Statistical Analysis System (SAS, 1985).
bath,
I57
RESULTS AND DISCUSSION
Copper
Leaf Cu: Variation in trace metal concentration withn each pH category was large throughout the
experiment. Consequently. the analysis of varianoe for each compost treatmentwas conducted using the General
Linear Models (GLM) procedure with pH as a continuous ratherthan a hscrete variable (Ray, 1982).
'fable 3. Mean tissue Zn and Cu cmcmmtiuo (mg kg") ofburley leafsamples m September
of1994.JuneandAugustof1995andcuredIcav~inbothyears~~~
COC. MSWC and WBC applied at 0,2S. 50 and 100 Mg ha". Within columns,
means followed by the same I d l e r arc not sipificantly different at p =0.05.
Irearments.
1994 Zn
cmw
COC'
wwc:
W
37.8a
B
C
J
1995 Zn
Fresh'
Cured
Composrte'
25
50
100
Szpt.
28.1a
33.7b
35.9b
37 5b
440a
38.2a 36.4a 58.4a
63.lab
50.lb
71.Ob
54.6b
71.lb
78.6~
38.3a
39.5a
41.3b
41.2ah
Middle6
40.7a
46.8b
46.lbc
S0.Sbc
48.8c
53.1~
0
25
50
100
29.7ab
27.9a
29.5ab
35.4b
38.9a
40.la
45.2a
61.8b
38.9a
40.4a
41.la
5O.Oa
41.la
41.5a
47.0a
49.3a
42.5a
43.9a
46.0a
68.0ab
36.4a
38.7a
38.8a
35.6a
59.8a 0 38.9a
29.8a
29.9a
29.4a
33.4a
40.h
66.3a
67.7a
69.4a
41.Sa
37.8a
41.7a
47.0ab
42.71
41.9a
54.6b
44.9~
52.3bc
43.7a
52.k
46.4ab
53.9~
Rate
0
25
50
100
4 6 . la
43.3a
49.8b
Fresh
June
Sept
58.8a
64.7ab
66.7b
1994 Cu
Fresh
Cured
cured
L
o
w
e
'r
57.7b
Cured
0
25
50
100
8.0a
1l o b
12.5b
13Sb
8.8a
12.lb
15.8b
28.7~
16.9a
19.0~
21.8b
20.6bc
13.9a
15.3a
153a
16.4b
10.2a
13.7ab
lS.2b
17.2b
MSWC
0
25 5.lb
8.8ab
8.la
9.7b19.9a
9.
7.3ab
17.7a
18.4a
14.0a11.7a
14.6a
14.3a
1S.9a
10.9a
12.2a
13.0a
17.9b
WRC
14.7a
0
17.7s 2 57.0a
17.2a 50 7.3ab
100
8.6a
8.2a
8.3a
9.4a
8.0a
7.m
19.9a
6.9a14.la
18.0a
11.9a
12.5a
10.3b
50.2a
1995 c u
Frcsh
COC
50
100 lab
=
42.9a
45.5ab
49.4b
55.8~
16.7a
13.7a
12.4a
14.2a12.6a 21.3a
I l.3a
14.3b
14.6b
16.5b
1 I.2a
14.0a
2 1.9b
11.5a
15.9b
11.0a
14.9a
14.4a
15.6a
24.1b
-
15.1ab
12.9a
I5.6ab
20.2b
I5.0ab
18.3a
13.4b
16.2ab
'I CKompostwl municipal solid waste and wastewater biosolids(Sevia Co., TN)
Municipal Sdid Waste Compost ( w m c r m b e Co., NC)
Wastewater Biosolids Compost (Charlotte. NC)
'
'mosI-redy.fnalured
leaves
'weighted composite sample
stalk position of leaves sampled
'
Miner and Tucker (19%) reported a North Carolina nutrient sufficiency range for Cu in the uppermost
fully developed tobacco leaf prior to flowering of 5 to 10 mg kg". Collins et al. ( 1%1) reported that flue-cured
tobacco contained 14.9to 2 I . 1 mg kg" Cu. Robson and Reuter (1981) found that for the majority of crop plant
c
species. Cu causes toxicity when the foliar Cu content IS 20 to 30 mg kg”. Mean leaf Cu concentrations at various
sampling dates for lffering rates of COC. MSWC and WBC application are shownin Table 3.
There was no effect of pH on leaf Cu concentration io COC andWBC treatments in September of 1994
(Figure 1: rates are pooled for W C ) , nor in MSWC treatments (data not shown). Indeed, 1994 late season leaf Cu
concentration in 25 and 100 Mg ha” COC treatments increased with increasingpH (rate X pH interaction). There
is usually a negative correlationbetween Cu uptake and soil pH (Tiwari and Kumar, 1982).
There was no pH &
e
c
ton 1994 cured leaf Cu concentration in any compost treatment. Cured leaves in
COC and WBC treatments in 1994 (Figures 2 and 3) showed a rate effect, wiule MSWC treatments (data not
shown) &d not. Leaf Cu concexuration in the 100 Mg ha” rate COC treatment was in the toxicity threshold range
reported by Robson and Reuter ( I 981). High l e a f Cu concentration at iugh pH: 1) supported
the theory that with
high rates of addtion of metals. the pH threshold for diminishng availabilityoccurs at hgher soil pH (Adams and
Sanders. 1984); 2) suggested the ling andLogan ( 1990) conclusion that “the population
of Cd b i d n g sites in
sludge varies widely in strength of specific Cd adsorption. and as sludge Cd concentration increases, the least
strongly bound Cd is more phytoavailable“can be applied to compost Cu as well: and 3) supported the hypothesis
h s case compost chemistry) controls the activity
of Cu in the soil
of C o p et al ( 1987) that sludge chemistry (in
solution.
Leaf Cu concentration in MSWC and WBC treatments was not related to pH and leaf Cu concentration
was relatively low in both cases at low pH. In these
adsorptive capacity of compost IMY control Cu
availability rather than low soil pH.
Early leaf Cu concentration forall composts in 1995 showedan interactionof rate X pH. The only rates
in all three composts whichwere inversely related to pH were 0 Mg ha-’ rates for COC and MSWC and 0 and 25
Mg ha” rates for WBC (data not shown).
*
Figure 4 shows late season upper leaf Cu concentration in COC and WBC (rates pooled) treatments. In
COC treatments. upperleaf Cu concentration &dnot decrease with increasing pH at any rate. Upper leaf Cu in
WBC and MSWC treatments was inversely relatedto pH but not related to rate (data for MSWC not shown).
Upper leaves in all compost treatments had a higher Cu concentration than lower leaves (data not shown).
Late season lower leaf Cu concentration showed a rate X pH interaction in COC treatments (data not
shown) in whch neither 50 nor 100 Mg ha” application r a t e s showed an inverse relationsiup topH, but 0 and 25
Mg ha.’ rates l d . Late season lower l e a f Cu concentration in MSWC and WBC treatments in 1995was not
related to pH or compost rate (datanot shown). Higher expected Cu concentrationat lower pH was probably not
observed in lower leaves because of translocation of Cu to upper leaves.
Cured leaf Cu concentration in 1995 in all compost treatments and atall leaf positions (dam not shown)
was not related to pH. Lower. middle and upper leaf Cu concentration was related linearly to rate in COC
treatments but n o t in WBC treatments. Lower and nuddle leafCu concentration was linearly related to rate in
MSWC treatments but not upper leaf Cu. Lower and middle cured leaves in COC treatments were sipficantly
lower in Cu concentration than upper leaves. Upper leaves had a iugher Cu concentration than lower leaves in
MSWC treatments. but WBC treatments did not vary in Cu concentration by leaf position.
Soil Cu: Mean DTPA-extractable soil Zn, Ni, Cu, Cd and Pb concentration at various samplingdates for
Mering rates of COC, MSWC and WBC application isshown in Table 4. Generally, them was no inverse
relationshp observed between DTPAemctable metal concentration and pH in September, 1994, exceptfor Ni in
MSWC and WBC treatments. No &ect of pH was observed on DTPA-extractable Zn,Cy C d , Ni or Pb
concentration in September. 1995. The response of DTPAextractable metal concentration to rate of compost
adbtion was generally linear throughout the e.xperiment. In contrast to Valdares et al. (1983) and k n g and Hajar
(199O), DTPAextractable trace metal concentration was not wellcorrelated with amountof trace metal applied.
Lindsay and Norvell (1978) reported a critical DTPAextractable Cu value of0.2 ppm. Follett and
Lindsay ( 1970) reported that DTPAextractable Cu rangedfrom 0.14 to 3.18mg kg” (while total soil Cu ranged
from 2 to 92 mg kg”). Walsh et a l . ( 1972) reported sigmficantreductions in snapbean yield at 20 mg kg-’DTPAextractable Cu concentration. DTPA-extractable Cu mncentration for compost treatments ranged from 0.44 to
9.33 pg g”.
DTPAextractaMe soil Cu concentration in September, 1994, was linearty related to pH in COC-tmted
soil (Figure 5 ) . conudcting reports in the literature ( h s c i o . 1978; Cavallaro and McBride. 1980). DTPAextractable Cu concentration was linearly related to rate and unrelated to pH in WBC treatments (Figure 6) and not
related to rate or pH in MSWC treatments (data not shown). The increasing extractabilityof Cu with increasing
cases.
X
X
A
I
t
x
I
45
-.
.
X
50
55
60
IO
65
X
X
'rn
A
X
/
,
,
,!"
X
X'm
pH could have contributed to Qfferences in leaf Cu concentration betweenCOC and WBC treatments in 1994.
DTPA-extractable Cu concentration was unrelated to pH in all compost treatments in 1995.
Table 4. Mean DTPA-extractable aoil Zn. XI. Cu. Cd and Pb concentration (Y g g.')
daummui m seplcmbcr of 1994 and 1995 for three c o m p o s t
COC. MSWC and
WBC. a p p l ~ dat 0. 25, 50 and 100 Mg ha". Witbin columna. dah followed by the m e
I&
we not significantly d i f k m t atp -0.05
treatments.
1994
0
MSWC2
25
50
3.328
,248
,348
,308
IO0
5.62b
.33a
0
25
I.lh
1.76b
1.67b
I.5Oab
,238
50
I00
WBC'
'
1.588
2.978
0.95s
1.60b
1.32ab
1.71b
318
0.808
109s
28a
1 OOa
,378
0.97a
0.84,
1 . 1 5.b
0
1.248
25
2.44h
.26r
338
50
I 00
2.65bc
3.61~
,358
1.19b
.33a
I.45b
03a
.05ab
06bc
.07c
1.IBa
1.72~
1.70a
2.54b
1.SOa
2.148
3.15b
4.23b
.34&
,338
.41&
.44b
0 . 9 1 ~ .04a
1.18ab ,048
1.62~
1.91ab
1.98ab
3.YOb
,338
,398
.43a
,710
2.01b
,358
44ab
.44ab
.52b
0.988
1.26ah
1.221,
1.77b
.03a
.O5b
.04ab
.03ab
l.38.b
,031
1.1la
1.768
.05b
.O5b
.06b
I.47b
1.31ab
1.40b
2.868
2.708
4.97b
1.08a
1.45b
1.29ab
.06h
.06b
1.338
1.72b
2.44~
2.58~
0.95a
1.030
.04a
1.351
,048
1.0h
,038
.OYb
1.56a
2.1.78
1.59~1
1.55bc
1.71~
.Ob
.04ab
.04ab
,066
1.51s
2.698
1.818
1.89a
C'c-Coa~pmted municipal s o l i d was@ and w ~ l m tbtioa
~oiib (Sevicr Co., TN)
Munioipl Solid Waste Compost (Buncombe Co., NC)
'
' WaslnvaLa Biosolidr Compost (Charlotte, NC)
C'u Comparisons .Among Comwsrs: Because i n h d u a l composts varied in trace metal content. hffering
leaf Cy nor DTPAextractablesoil
amounts of trace metals were applied at each compost application rate. Neither
Cu concentration. therefore, could be Qrectly contrasted amongcomposts by rate of compost application. When
concentration was regressed against rate of metal application for each compost. plotted regression linesQd not
overlap and a comparison of composts remained mappropriate.
Log transformation of Cu, Zn. Pb and Ni application rates and corresponding tissue or soil concentrations
of these metals allowed a &
r
e
c
tcomparison of COC and WBC treatments because log tramformed regression lines
o v e r l a p p e d . Log transformation of Cd and Ni application rates and correspondingtissue or soil concentrations of
these metals allowed a d~rectamparison of all three composts.
Compansons of leaf Cu concentration were made with log-transformed data. At equal ram of Cu
application, leaf Cu concentration was greaterin "lugher Cu" COC (215 mg kg" Cu) treatments than in "lower
Cu" WBC (173.3 mg kg" Cu)treatments in late-season and Ned l e a v e s in 1994 and in June and August upper
leaves in 1995. (data shown for 1994 cured leaves in Figure 7 and June, 1995, upper leaves in Figure 8). Th~s
suggested the Corey et al. ( 1987) conclusion that "sludges with lugher metal concentration could cause lugher
tnetal uptake by plants whenequal amount of metals were applied" could alsobe applied to composts.
The sigruficant interaction of rate X pH for September 1994 COC leaf Cu concentration shownin Figure
1 may also help to e x p h why leaf Cu concentration in COC and WBC treatments Mered sigmficantly at that
time. Leaf Cu concentration was unrelatedto pH and rate in W C treatments, whereas in 25 and 100 Mg ha"
COC treatments itwas linearly related to pH.
The difference in 1994 cured leaf Cu concentration may be exphned by examining Figures 2 and 3.
Mean cured leaf Cu concentration (Table 3) in 100 Mg ha" COC treatments (28.7mg kg-')was over twice that of
100 Mg ha" WBC treatments (10.3 mg kg-'). This M e r e m e supports the concept that in higher metal composts
me metals can occupy low energy binding sites and be more availablefor plant uptake.
Differences in I995 late season Cu concentration (Figure 4) may have occurred because leaf Cu
concentration was unrelated to pH in COC treatments and inversely related to pH in WBC treatments.
Compansons of DTPA-extractable soil Cu were made with log-transformed data and showedsigtzlficant
differences in September. 1994. DTPA-extractable Cu concentration betweenCOC and WBC treatments. Once
again at equal rates of metal application the compost with the hgher metal concentration had more "plant
161
IS
*
I6
e
I4
e
06
04
10
1
10 0 l"
90
80
.
" 70
I
$
60
50
5
6
<
40
0.
10
20
10
201
00 c
4s
*O
t
50
60
55
X
X
,
162
6<
-1
available“ Cu than a lower metal compost. Extractable Cu concentration increased with increasingpH and rate in
COC treatments and was unrelated to pH in WBC treatments (Figures5 and 6).
Zinc
LeafZn: Normal Zn concentrations in plant tissue ranges from 25 to 150 mg kg” (Adnano, 1986) and
mean Zn content in various commercial tobaccos is 51 to 84 mg kg‘’ (Ward, 1941). Mmer and Tucker (1990)
reported a North Carolina nutnent sufficiency range for Zn in the uppermost fdly developed tobacco leaves prior
to flowering of 20-60 mg kg”. Mean leaf Zn concentrations at various sampling dates forM e r i n g rates of COC,
MSWC and WBC application are shown in Table 3. Burley IeafZn concentrationat all sampling datesfell witlun
the reported ranges.
A signlficant rateX pH interaction for 1994 curedleaf Zn concentration inCOC treatments is shown in
Figure 9. At the 1 0 0 Mg h a - ] rate. Zn concentration was linearly related to pH and at the other rates of adchtion of
COC. leaf Zn concentration was unrelated to pH. Leaf Zn concentration was unrelated to pH inMSWC (data not
shown) and WBC (Figure 10) treatmentsin 1994 cured leaf samples. The lughest rate of a&tion of Zn in the
COC) resulted in increasing leaf Zn concentration as pH increased andsupported the
c..;periment (100 Mg
Adams and Sanders ( 1984) findingthat higher metal concentrations (in sludges) resulted in increased
metal
solubilit) and hence uptakeat higher pH values.
Late 1995 leaf Zn concentration was inversely related topH in lower and upper leaves in COC treatments
(data not shown). Upper leaves demonstrated a rate X pH interaction. Late 1995 leaf Zn concentration in MSWC
and WBC treatments was unrelated to rate but was inversely relatedto pH in upper leaves in MSWC and WBC
treatments and in lower leaves in WBC treatments (data not shown). There were no sigruficant &fferencesin Zn
concentration between upper and laver leaves in any compost treatment at that sampling date.
*
Cured upper, middle and lower leaf Zn concentration in COC treatments in 1995 was inversely related to
pH and linearly related to rate. A signtficant interaction (rateX rate X pH) was observed in middle leaves, with all
rates inversely related to pH. Upper leaves had sigtllficantly lugher Zn concentration than lower leaves (datanot
shown). Tlus contradicted data presentedby King and Hajar (1990) and Franket al. (1977). Upper, middle and
lower cured leaf Zn concentration in MSWC treatments was inversely relatedto pH, and no interactionswere
signlficant ( d a t a not shown). Upper cured leaves had signdicantly tugher Zn concentration than lower leaves (data
not shown). Cured upper, middle and lower leaf Zn concentration in W C treatments was inversely related to pH
and linearly related to rate
but there were no sigruficant differences inleaf Zn concentration amongleaf positions
at that time ( d a t a not shown).
Soil Zn: in COC treatments, DTPAextractable soil Zn concentrationshowed a rate X pH interaction in
September of 1994 (Figure 11). Zinc concentrationwas linearly related to pH at the 100 Mg ha” rate and was not
related to pH at other rates, contmhcting many reports including thoseof MacLean (1974), Friesen et a l . (1980)
and Gupta et al. (1971). DTPAextractable Zn concentration was unrelated to pH but linearly related to ratein
both W C (Figure 12) and MSWC treatments (data not shown). All three composts showed a linear response to
rate in 1995. but no response to pH.
Zn C‘omuarisons Among C’omuosts: Compansons of composts were made with log-transformed data.
There were signrficant Merences in leaf Zn concentrationbetween COC (737 mg kg-’Zn) and WBC (499 mg kg”
Zn)treatments in both late and cured leaves in 1994. Merences in 1994 late seasonIeaf‘Zn concentration are
shown in Figure 13 (data for 1994 cured leaf concentration not shown). At equal rates of Zn loading, leaf Zn
concentration in “lugher Zn” COC treatments was sigmficantly greater than leaf Zn in “lower Zn” WBC
treatments. Tbs suggested the Corey et al. (1987) conclusion that‘‘sludges with higher metal concentration could
cause lugher metal uptake by plants when equal amount of metals were applied” could be applied to composts.
Leaf Zn concentration was inversely related to pH in WBC treatments whde in COC treatments was
it not, and that
contributed to the difference in 1994 late season leaf Zn concentration between the two compost treatments. The
Merence in cured leaf Zn concentration may be partly explainedby the interactions of pH and rate in COC
treatments in wluch both e
la
f Zn and DTPAextractable soil Zn concentration increasedwith increasing pH at the
compost chemistry rather than soil chemistry seemed to be conuolhng plant Zn
100 Mg ha” rate. In both
uptake. However. there was no difference in DTPAextractable soil Zn concentration betweenCOC and WBC
treatments.
ha-‘
cases.
"
3 03 1
8
x
8
8
A
8
8
I4
8
I
OJ
43
JO
60
30
O3
I
X
9
!.
ii
I J
10
IO
OJ
00
00
I64
X
Am
63
i
1
I
Cadmium
With the esceptmn of t h e composite samples taken from 1994 cured burlq l e a v e s , there was little
detectable Cd in burley tissue at any samplingdate. Only 69 out of 87 1994 cured leaf samples contained
detectable Cd. For the purposes of statistical analysis, the I8 samples with Cd content below detectable limitswere
assigned values of 0.4 mg kg" (50% of the detection limit). Fewer than 15 samples at any other sampling date
conmned detectable Cd. Cured l e a f Cd concentration was mversely related to pH in COC MSWC and WBC
treatments in 1994 (Figures 14, 15 and 16, respemvely).
In contradichon to reports in the l i t e r a m (Chnstensen, 1984a; Kuo et al., 1985) extractable Cd
concentration inCOC treatments increasedsigrufiicantly as pH increased in September, 1994(datanot shown).
Available Zn Cu Ca and Mn in solution may have reduced Cd s o w o n through competition fora d s o m o n sites
(Kuo and Baker. 1980; Bittell and Miller. 1974). Considerable Zn Cu and Ca was added to the soil in COC
applications and theDyke soil contained 500 mg kg" Mn (Tables 1 and 2). DTPAextractable Cd concentration
was low in all treatments throughout thee?cperiment (Table 4).
When data was log transformed. there were significant Merences in September, 1994, DTPAextractable
Cd concentration among compost treatments (data not shown). At equal rates of Cd appbcation, DTPA-extractable
Cd concentration was sigmficantly higher in "higher C d COC (2.9 mg kg") and WBC (2.1 mg kg") treatments
than in "lower C d MSWC ( 1 . O mg kg") treatments.
Lead
No Pb was detectable In burley leaf tissue at any sampling date in either1994 or 19%.
Cox and Rains (1972) andJohn and Van Laerhoven (19726) reported that application of lime Pbto
contaminated soils reduced the foliar Pb content of plants but had little effect onPb in roots. DTPAextractable Pb
concerltration in September, 1994. soil samples taken from COC treatments showed a rate X pH interaction in
whch extractable Pb c o n c e r n o n &d not decrease with increasing pH (Figure 17). At the 100 Mg ha" rate.
DTPA-extractable pb concentration in COC treatments increased with increasing pH. Extractable Pb
concentration in W C treatments was inversely related topH but not related to rate (Figure 18). Extractable Pb
concentration was not related to either pH or to ratein MSWC treatments (data not shown).
Log-transfomed September, 1994, datashowed that at equal rates of Pb application, the "hgher Pb" COC
~
I
(203 mg kg") treatments had hgher extractable soil Pb concentration than"lower Fb" WBC ( 8 8 mg kg")
treatments.
Nickel
No Ni was detectable in burley leaf tissue at anv sampling datein either 1994 or 1995.
DTPAextractable Ni concentration was low in all compost treatments (Table 4). In contrast to reports in
the literature (Harter. 1983; Gemtse et a l . 1982), Ni extractability was unrelated to pH in COC treatments. Rate X
pH interactions were observed in MSWC treatments for DTPAexvactable Ni concentration, and extractability was
inversely related to pH. In WBC treatments, DTPAextractable Ni concentfation was inversely related to pH and
unrelated to rate(datanot shown).
When September, 1995, data was l o g transformed (datanot shown), "lower Ni" WBC (16.3 mg kg")
treatments had iugher DTPAextractable Ni concentration atequal rates of Ni application than "higher Ni" COC
(39.7 mg kg") treatments.
CONCLUSIONS
,
Trace metals appliedin COC.MSWC and WBC did not accumulate inleaf tissue in sufficient quantities
to produce toxicity symptomsin burley tobacco. Burfey leaf Pb and Ni concentration was below detectable limits
and Cd concentration only deaectable in cured 1994 leaf samples, was low. Burley leaf Zn and Cu concentration
was linearly related torate of compost a t i o n , but mean leaf Zn concentrationfell within the suf€iciency range
reported by Mner andTucker ( 1 9 9 0 ) in all compost treatments. Leaf Cu was above the sufficiency m g e reported
by Mne~
and Tucker ( 1990) in most treatments, but within the normal range for
fluecured tobacco reported by
Collins et. al ( 1961). Cured 1991 leaf Cu in 100 Mg ha" COC treatments was withm the toxicity range reported
by Robson and Reuter ( 1981). However. RO Cu toxicih symptoms were observed.
Taken together. theaidence prokided by ths experiment indmted that at the same rate of metal
application, Zn and Cu in composts are more available from composts containing tugher concentrationsof these
163
metals than from lower metal composts. Leaf Cu concentration in 1994 and 1995 and leaf Zn concentration in
1994 was generally not related to pH and the estractabilioof trace metals generally did not vary with pH (in some
cases incriased with increasing pH), even at high rates of addtion of compost. These f i d n g s indmted that
compost chemistq influenced d not controlled the availabilityof trace metals to burly tobacco.
REFERENCES
.4datns..r.%f.and J.R. Sanders. 1984. ' f i e
e f f mof pH on release to s o l u t i o n of tinc, oopper aad nickel hmetal-loaded sewage sludges. Envrron
Pollur R8.85-99
D.C. 1986.TraceEiemenrs m fhe Terrestrial Envrronmenr. Springer-Veriag. New Y a k .
D.C.. A I , . Page. A A Elseewl and A C . Chang. 1982.Journal ofEnvlronmenrulOualr~.1 I : 197-203.
BitteL J E.. and RJ. Milia.1Y74. Journal ofEnvrronmenfa1 Qualrty. 3:250-253.
B
r
m
e
r
.J . M . 19650. Inorganic -f
ofnitrogen. In C A Black d al. (ed)Methods ofsoil analysis. Part 2. Agronomy 9:1179-1237. Am Soc. Of
Adnano,
Adnano,
Agrm., Madison
ws
Cavallaro. N.. and MB. ktcBnde. 1980. Sod Scrence Society ofjlmerrcaJourna1. 44:729-732.
Chancy. R.L. and J.A Ryan. 1993. H e a w metals and IOXIC
organic pollutants in MSW c o m p o g t s . In Scrence andEngrneerrng ofCompostlng:
eds.pp. 451.489. Renaissance
Desrgn. Envrronmental,Afrcrobroioglcal and Utllnanon Aspects. Hany AJ. Hoitlnk and Harold M. K-,
Puhhcatlms, Wortlungton O H . 728 pages.
Chnstensen. T.H. 1984a. Cadmium soil sorption at l o w wncmtm~ons:1. E f f d oftime. c h u m load. pH. and calcium. Water Air SorlPolluf.
21 105-1 14.
C o l h . W.K.. G L , . Jonrs. J.A Weybrew and D.F. Matzinga. 1961. Conrparative c h a m c a l and physical composition offlue-cured tobacco varieties.
Crop Science. 1 :407.
Corey. R.B., L.D. lung, C. LueHing D.S. Farming J.J. Street and J.M. Waker. 1987. Effefts of dudge properties on acaunulatcon of trace elements
b! cmps. In: Lund Apphcanon ofsludge. AL. Page et al. Eds. pp25-5 1. Lewis Publishers C k k MI.
Cox. W.J.. and D.W. Rluns. 1972.Journal ofEnvrronmenfa1 Qualrty. 1:167-169.
Follett R.H.. and W.L. Lmdsay. 1970. ln:Profile Drstnhuhon qiZrnc. iron. .Wanganese. and Copper rn C'olorado Soils. Colorado .Agn~xItural
E q e n m e n l Station Twhtucal hlldn 11O:l-78.
Frank. F . H.E. Bran. M. Hddrinel and K.I. Stonefield 1977. Metal contents and insecticiderestdues in tobacco soils and wed tobacco leaves
c a l l e d e d in sortthem Ontario. Tobucco Scrence.2 1 :74-80.
Frken. E.K. AS.R. Juo. and M.H. Miller. 1980. SorlScrenceSocretyofilmencaJournal. 44:1221-1226.
ciemtse, R.G.. R. V r i m J.W D a l h g and H.P. de Roos. 1982. Journal ofEnvrronmenral Quality. 1 I :359-364.
Cnrpla. S E..F W. Caldcr, and I,.B. M a c l d 1971. Plonr andSorl. 35:249-256.
Harter. R.D. 1983. Sorl Scrence Soclery ofAmerrcaJourna1. 47:47-51
1992. Effects of sewage sludge cadm~umamcentration on CIIUNWI
extraaability and plant uptake. J . Emron. Qual. 21 :73Jmg, J. and T.J. 1-an
81
J o h n M.L. andC.J. Van Laemoven. 197%. Journalof~nvlronmental~alrry.
1:169-171
bg,
L.D. and I.M. Hqjar. 1990. The resldual c f f d of sewage sludgeon heavy -1
amtent o f t o b a a and peanul. Journal ofEnwronmenfai
Qualrty. 19-738-748.
Kuo. S., E.J. Jellum, and AS. Baker. 1985. E f f d of soil type.liming, and sludge lppliation on zinc and cadmium availability to swiss chard. Sorl
Science. 139:122-130.
liuo. S.. and AS. Baker. 1980.S o 1 1 Science .%wep ofAmenca Journal. 44:%9-974.
W.L.. andW.A NorveU. 1978. Developnent of a DTPA soil tesl for zn
i c, iron,
and c o p p e r . Sod Scrence SocietyOfAmerica
Journal. 42:421-428.
Locascio, S.J. 1978.Solunons. 3042.
M a c h AJ. 1974. CanadranJournal ofSol1 Scrence. 54:369-378.
McGram. S.P. and C.H. CunliEe. 1985. .r\ simplified method for the extraction ofthe metsls Fe, Z n Cu.Ni, C 4 Pb,Cr. Co and Mn fim so~lsand
"age sludges.Journal of Scrence. Food andAgnculhcre. 36:794-798.
Miner. G., aud R.Tucker. 1 9 9 0 . Plant analysls as M aid m ferfilizlngtotmum. In:So11 Tesrrng andPlant Analysrs. R.L WaAermaq ed. Pp. 645-657.
Sal science society of ,.hfXica, loc. Macbson WI.
North Carolina Coopnative ExknsKm S e w i c e . 1994. I995 Eurley Tobacco Infomanon. AG 376. North Carolina State University. Raleigh, NC.
Ray. A.4 1982. SAS user's guide: Statistics. SAS Inst.. C m , NC.
manganese.
LmQa)..
RobsonAD.andD.J.Rcuter.1981.DiagoosirofooppadeficiencyMdtoxicity.InCoppzrinSoiLFandPlards;J.F.LoneeragaRAD.Robsonand
RD.Graham F h . p ~ 287-312.
.
A ~ ~ I T Uk,
C
London.
SpDders J.R. and T.M. A d a m . 1987. The effof pH and soil type on aJncentntion of zinc,copper and nickel eby c a l c i u m chloride tiom
sewage sludge-treated soils Envrron. Pollut. A43:219-228.
S M . 1985. SAS User's Guide statistics. S M htitute,Cary. NC.
H A . and J.J. Balassa. 1961. .UnwrmnI trace metals inman: C h u m . Journal of'Chronrc Disorders. 14:236-258.
S m a S.R. 1992. Sewagesludge and r
e
k
as peat altematiws for
impoverished soils: Effect.. on the growth response and
nunerdstatu5 offerunra grandrflora. Journal
ofHortrcultrrro1 Scrence. 67(5): 703-716.
Soil CoaFervatim Service,L'SDA 1972. Soil survey lab&utory methods and proceduresfor collectmg soil -I-.
Soil Survey invest. Rep. 1. U.S.
Gov. Print. CHke. Wadungton, D C .
Tancogne, J.. Nguveo Phu Lick P. Schdtz. R Truhaut. J.D. Claude, and J. C b . 1988. Influence of various g o 4 1medim related factors on
the absurptlon ofcadmiurn. i'ORE'ST.4 Information Bull. 1988 Congress. Ocx 9-13. China.
Tiwari. R.C.. and B.Y. Kumar. 1982. PlunfandSorl. 68:131-134.
Valdares. J.M.4.S.. M.Gal. I'. Uingelgnn, and AI,, Page. 1983 Journalqf~nvrronmenfulQualrry 12:49-57.
Ward. G.M. 194 I . .Vineral absorpton studies wrtb tobacco. TheLrghter. 1I( 1):16-22.
Wuoeder.
c
o
n
d
v
t
i
i
166
USING COMPOST SUCCESSFULLY
Ron Alexander
E&A Environmental Consultants,
Inc.
Rod Tyler
BFI Organics
Oberlin, Ohio
Composts are b e i i produced out of many feedstocks with the use of various bulking agents and under various
chemical
b & d M
o
t
iu
s
.Consequently, composts exhibit a range of characteristics and finished
products are produced which possess various cphties.
,-nB
It is importadthat compost manufacturers, marketers and eod-users understand that this variability exists, and
thrt pplbcular c ~ m p ~ am
d s beLter suited for specific applications and use under specific conditions. Understanding these
frcQ can lAp u m d i & m m pmhroe
possessing appropriate characteristics, marketersdistribute their products
to the appropriate eod-users and endusers purchase and use the product best suited for their specdic use.
. In order to better addrees this concept, this article describes the major markets for compost use,
-e
of poclud uses within each particular &et
offers an
and outlines the desired compost characteristics forthose uses.
LANDSCAPERS
Landscapers have bee0 using composted products for many years and in many applications. So it should be no
great surprise that landscapers are currently using large quantities of composts produced from various municipal and
.gnarhrralby-pmdwts. Composts of various qual~tyand possessing varying characteristics have been used in numerous
ldscape applications such as soil upgrading; turf establishment and maintenance; mulching; and in the establishment
and mPideoance of ornamental plants.
Tbe type of compostused by M individual depeods oa product availability, the specific application and customer
preference.
Soil IncorporatiodUpgrading. Compost is an excellent amendment for soils low in organic matter content,
suffering from poor nutrient retention properties, highly compacted or lacking water-hoiding capacity. The addition of
compost improves the soil bath physically and chemically, dowing for bealthy growth of turf and ornamentals.
Research has shown that the application of biosolidscompost at a rate of 260 metric tons per hectare
(approximately 235 cubic ypnls/acre) enhances the establishment of turfgrass from seed. The application of 180 metric
tom per hectare (approximately 160 cubic yards/acre) of compost was adequate for the establishment of turfgrass sod.
In mwarch experimeots, compost s i g d i u d y improved the rate of establishment and general Bppearance of the turfgrass
(Angle 1981).
Tbe appllcaboa of a 1- to 2-inch layer of varioustypes of compost is often cited as a general application rate for
upgredmg soil for the edablbhumxd of turf from seed or sod. This layer of compost should then be incorporated to a depth
of 5 to 7 inches for maximum effectiveoess. Soil testresults ohen include a test for organic matter content, and
recommervi a specific quantity to apply.
Compost used in soil upgrading should be rich in organic matter (more than50 percent), free of weed seeds and
possessing a texture and moisture content which allows for easy spreading. The pH and soluble salt content of the
compost is dependent upon the characteristics of the soil being amendedand the plant materials to be established.
I67
. .
cs ~ f less
e critical tban in ganlen applications for annual or perennial
plads. In these latter applications, the soluble salt content of the compost is more critical because these crops are more
susceptible io salt damage. Excessive levels in the soil mixture may be damaging to certain species such as geraniums
and asters, however, plant species will respond differently to the application of compost.
Inhrrfgress applicatioos, thesec-
For example, it has been shown tbat various annuals and herbaceous perennials respotxi favorably to compost
applications at a rate of 10 percent to 30 percent of a garden soil mixture (Smith 1992). A l-inch application rate of
cxmpost tilled to a depth of 5 inches is a 20 percent inclusion rate. It is also important that compost used in this manner
is stable (well cured), so that nitrogen immobilization does not occur.
Higber e\alay ad mom refined campo&, up to this pod,have proven to be more poplar in soil incorporation
p
o
.j
e
d
sfor gaFdea areas ad 011 borne lawns. h mtined products, such as composts containing foreign matter and ones
which are odorous, are more acceptable in commercial d o r industrial applications. The use of compost in soil
improvemed may reduce fertilizer requiremeats and the need to lime.
Topdressing. Topdressing has long been a reliable turf maintenancepractice in the golf course industry and has
grown in popllanty for commercialand home lawn applications. The practice entails applying a thin layer (approximately
1/8- to IQ-inCh) of topdressing material over an established and usually declining turfarea. The practice is usually done
m coqundm with aeration in which s m a l l plugs of soil are removed from the soil surface. Reseeding of the area often
follows.
This process improves water mtiltration, increases the water holding capacity of
the soil and reduces soil
compaction. Compost used as a topdressing must not only be consisted in its chemical characteristics, but also in its
physical characteristics. The material used in this application should be finely screened and must have a texture which
crlbrm easy qxeadmg. It mud ais0 be free of foreign matter and objectionable odors, since much of the material will be
left on the soil surface.
This & e+
to grow witb the popllanty of b w ;oplt laodscaping d o r maintenance practices which
. .
ueeorgenicmaterials.ThecbeolicPladbiobgdchmdemtm of compost are also believed to improve the degradation
of tbatch which may be a nuisance in some established turf areas.
Pkmting Mixes. Composts have been used as a componed of various landscape growing mixes such as roof top
mixes, raised planter mixes, planter box mixes and backfill mixes. These mixes may inchde topsoil, peat moss, sand,
Styrofoam, vermiculite, perlite and compost usually at a rate of 25 percent to 33 percent of the mixture.
Cornpoet m these applications will improve drainage and water holding capacity of the mixes, encourage deep
Footing ami will supply a rich source of organic matter and nutrieds. The organic matter supplied by compostw
l
ialso
incrense the cation exchange capacity of the mix and supply valuable humic wid, which aids plant uptake of some
mtrients. The compost used in these applications must have a pH and soluble salt content which, when mixed withthe
other pWmg txqxmds, are acceptable to the growing
This matetial must be weed free, have a workable texture
and must be stable to avoid nitrogen immobilization.
plads.
Mulching. Some composts have been used as a decorative mulch in planting/garden beds with great success.
Tbgr are usually applied to the soil surface at a depth of 2 to 3 inches. Compost mulches are used to conserve moisture,
bwer soil temperature, reduce erosion, provide nutrients and discourage the establishment of weeds. Because mulches
are also used for decorative purposes, selected materials must haveM acceptable aesthetic "look".
The compostmud have a uniform Bppearance, possess an acceptable color and should readily absorb moisture.
The C001p06t f1116t also be free of weed seeds and have a pH and soluble salt content which willnot negatively affect the
growth of the plant materials being mulched. Composts producedfrom both biosolds and yard trimmings are currently
being used successfully as decorative mulches, while composts produced from municipal solid waste have not been as
popllar in this application because they often contain foreign matter, giving it a non-uniform appearance.
168
Ea& year, a large and ever expmdmgofacreage
is madaind as sports turf. New golf courses continue
to be hilt as the popllanty of the game increases. At the same time, the popularity of many other field-played sports has
forced the construction ofnew fields and has increased the use intensity of existing fields. Compost used in the
construction and maintenance of sports turf has both a proven track record and bright future in this market.
The golf course industry has a great appreciation for the importance of organic matter and for this reason the
many composted products is commonplace. New uses for compost on golf courses a m also gaining momentum,
but have not yet gained t d a l acceptance by this conservative industry. The most popular of these uses are discussed
use of
below.
T&msing. This marlcet niche is slightb dtffetent than previously noted in the landscape section. Golf courses
historically have less margin for error in the maintenance of turf as a result of high intensity management programs.
Therefore,the compost pmluds used m toplressing mixes will m d y be of high @ty,
possess a high organic matter
content, a low odor potential and be low in heavy metals and soluble salts.
Composts used in topdressing mixes may have a pH of 5.5 to 8 and will d to be stable fully mature with
minirml inert codaminaots.particle size of compost used for topdressing should be less than onequarter inch since most
mix- are screened at least to this size.
T y p d t o p d ~ ~ ~mixes
i n g for golfcoumx are comprised of 70 percent to 90 percent sand and organic material.
psrt omss is the reliable standard, but some research indicates compost may be an acceptable substitute (Nelson 1992).
Fairways, although wt curredly topdressed as frequently as greeas, comprise the largest potentialpercentage
of the total topdressing budget. Golf courses have used finelyscreened compost alone as a topdressing on fairways, or
as a mmpond m a s a d based mix. The future for compost use through topdressing mixes looks extremely promising.
Early resoprch indicates compostmay h v e disease suppressive propefiies which IUICISto overall value. Therefore,future
topdressing programs may be funded through pest/disease c o n t r o l budge4s.
ConrrnrcrioPl Mius/RcnovaciopI. The same general guidelines for product qual~tyapply to golf course
cumtm&m mixes, although larger BmouDts of product are used more quickly, especially in whole course construction.
~~as~to~yyardsofamixmaybeusedforeechgreen,indicatingalargeinitialout~yofcompostforan18bole course. Additionally, greater amouds of compost can be used in bed preparation and h h c a p i n g of the g d s
(refer to laodscape section).
Arhlcric Fie&. As the desire and need to create more resilient, more attractive and safer athletic fields has
The need for an organic product which can
be used in the maintenance, renovation and construction of athletic fields will help fill this void, and help a market
strapped by shnoiring budgets.
incFeesed,so too has the need grown for an inexpeasive, versatile product.
As discusd earlier, the eddition of compost to soils rich in sand or clay content w
liimprove the structure and
friability of the soil. Tbe use of compost w
l
i also improve the drainage in athletic field soils, and the addition of organic
matter will slow the rate of compaction. Tbe use of compost in the maiotenancs (topdressing), renovation (soil
luneadmed) and COnstNCtiOtl (mix c o m p o n e a t ) is explaioed in more detail in Table 1 (Alexander 1 9 1 ) .
The use of compost on athletic fields will continue to grow as long as the product stays price competitive aod
coosisted m qual~tym comparison to peat moss and commercially available topdressings. Compost used in athletic field
mpideopnce (topdressing) must fit the specilieations outlined earlier in the landscape section. Again, the material must
also be finely screened in order to be m i l y backfilled into aeration boles, and so as not to smother existing growth.
The compost 11116
be
t stable and free from sigdicant foreign matter since traces of the material m a y be visible
surf-. Compost used in the remvation or construction of athletic fields may be slightly coarser than material
used in topdressing.
011
the soil
169
Compost screened through a threeeighths to one-half-inch screen is acceptable for use in the renovation and
conscructionof athletic fiekls,while materials used as a turf topdressing should be screened through a one-fourth to threeeighths screen. Compost used m t
h construction of athletic fields must have a texture which allows it to be easily mixed
with other athletic field mix components like silica sands. Ratios and possible combinations of topdressing mixes are
determined on a case by case basis, depending on native soil test data.
Material with a moisture content of 55 percent or more may be difficult to spread or mix efficiently. Since the
majorih/ of ethletic fietls are loccrted at heady popllated schools and universities, the useof materials with objectionable
odors or e sipficnnt amount of foreign material is not recommended.
. .
conrtructing
Renovating
Topdreuing
1.
Heavily coreaerateentire athletic
1.
Mechanically till the entire field,
tuning the roil and destroying the
remaining vegetation. A rototiller or
farm dirk are the beat pieces of
quiprnent to uac. Killing the existing
turf cover with a non-selective
herbicide may be worthwhile if weed
infeatation in significant.
1.
Using front-cnd lorden or other bulk
blending machinery, manufacture
your field mix. To CMUE uniformity,
manufacture the mix in small,
controllable batches. Mixingahould
be done off the construction site.
2.
Applyapproximately a half-inchlayer
of compost or 50150 nndlcompod
mixture. The most uniform and
ffficient way to apply the compost is
with a topdreuing unit or manure
gruder.
2.
Apply two to three inches of compost
over the entire field. More product
can be urcd in a r u s on the field8
which have received the most w a r .
(e.g., center of football fields).
2.
Sprud the athleticfieldconatruction
mix using a grading blade over the
entire field, starting from the center of
the field and working out. For
optimum results, the mix should be
rprud to a depth of 12 inches.
3.
Smooth the surfaceusing a raking
device or using a weighted drag mat.
The rakingldmgging will break up the
roil plugs, mix it with the compost
and backfill the holes.
3.
Incorporatethe compost into the field
to a depth of six to IO inches.
Normally, the deeper you can
incorporate the product, the bcacr.
Work the mil until it is thoroughly
mixed and clump-fru.
3.
Shape and smooth the field using a
raking device. Firm the field using a
light roller. Establish a crown on the
field if desired.
Seed and water the o
tp
d
r
e
d area.
It is impottant not to leave the gmu
aced on the mil surface. It ahwld be
4.
Shapeand smooth thefieldusing a
raking device. Finn the field using 8
tight rolkr. Eatabliah a crown on the
fded if desired.
4.
Seed and water the field. To improve
I
4.
5.
reed germination, incorporate the
g n u reed into the top onequarter
inch of conatruction mix.
Seed and water the field. Make wre
the reed is incorporated into the top
one quarter inch of modified roil.
Topsoil bleeders are not a tme endusers of compost because most of the materials they purchase are resold to
other green industry professionals once blended. Lpodscapers, garden centers, nurseries and homeowners are often the
endusers of compost products which a m used after being professionally blended by a topsoil company. Many believe
that the fuhve of topsoil blending lies in the manufacturing of special blends to suit specific growing requireme& of
specific plant families.
Adding compost to soils usually reduces potential m
f
f and erosion (Kashmanian 1992). Urban soils in most
major metropolitan areas have bad their soil structure destroyed from pulverization or multiple handliag by large
equipmeat (McCoy 1990). Research has shown that the addition of organic matter to these soils in a blending situation
helps the resulting mix set up new structure whea placed on the job site (McCoy 1990).
Recommeoded inchrsicm rates of c ~ m p ~ scan
t vmy greatly depending on soil characteristics, however, a general
guideline of 20 percent has been shown to be effective in the lab and field (McCoy 1990). Many composts also exhibit
a wide particle size distribution which may or may not be b
t
i
c
i
a
l in a blend, depending on the objective of each mix.
Composts used for topsoil p r o h c h n theoretically may be coarse as long as the final mix is screened. If a blend
is made witbout final screening, compost should be supplied as three-quarter-inch or less in polrticle size. Heavy metals
PCB less of a Cancem for horticultural applications. However, considering that many homeowners wdl purchase products
for edible crop production, safety standards for food chain production should be followed.
Organic matter coded sbuuld be consistent within the source of compost utilized. If the feedstock materials do
not regularly change, the end-product s b M be consistent in organic matter conteat. Changing compost feedstocks
mideers<m may aher bleoded topsoil appeamm aod create mark& confusion unless creative blendingmeasures are taken.
canpost needs to be stable and low in soluble salts for most soil blend end-markets. The pH of composts used
in bleods may vary from 5.5 to 8. The pH of the final soil blend w
l
i depend greatly on the buffering capacity of the soil
aad tba pH of iogredieds. Many curreot topsoil mixes are manufactured to meet the growing requirements of particular,
plants, and pH may be adjusted accordingly by d i n g lime or ammonium sulfate.
Special B h a k . Tbere is a growing demand for special blends of soils for all types of horticultural applications.
ingrowing media
is also forecasterl. The co~ceptof offering blueberry mixes, azalea mixes, annual mixes, perennial mixes, etc., for future
markets is very strong. However, the amout of research and documentation that needs to be done to support these
make& is vast.
with the specialization treod that has takm place in other industries of the United States, specialization
Cumdy, Laodscape architects speclfy potential unnposi products in their plans for new construction based on
their knowledge of growing media and the existing soils. It is vitally important that my new mix be studied and the
additionof compost to this mix be compared to a standard such a8 peat moss, hardwood bark, &c.
Becausemany state hws maodate compo6.ting yard tnnnnings,biosolids, and other organic by-products it seems
only natural that local blending and specialized custom blends will some day be a large market for compost products.
Criteria for compost used m this market sector is highly variable with respect to pH and soluble salts due to the
variable requirement ofmany ddferent plant species. However, it is likely that consistent, stable, medium-textured
composts with little or no inert contamination will be ideal for marketing through special blends.
The reclamation and revegetation of highly degraded sites is m excellent use for compost. Compost has been
with great success in the reclamation of strip minea and d g r n v e l pits, and in the closure and vegetation of
canpost bas unique cbearicel, physical and biological characteristics which make it well-suited for use on sites
tbst PCB diffiarlt to re-establish with plant life. Compost has even been used to remediate soils which have been polluted
used
I.ndfils.
aadwere~letosustainpladgrowth.Thismpricetalsoshowsagreatpotentiala8ameanstouselessrefinedcompost.
Pits.
Smp Mincs/smd and Gmvcl
Tbe poteohal qumtities of compost used in rewvating of surface mines, sand
aad~velpitsistremeodous.Compostcanbeused~asoilameodmentataquantityof1~~to400cubicyanlsperacre
(approximately 1- to 3-inch layer) in order to help support vegetative growth. This vegetative growth stabilizss the soil
surface a d reduces soil erosion and runoff which may lead to surface water contamination.
Previous work has shown that the use of biosolids and other composted products applied in a large onetime
apphtnm can be used to revegetate abandoned mines (Sopper 1991). Vegetating abandoned mine sites may be difficult
because high levels of contaminants often found at many sites are toxic to plant growth.
In saod aod gravel pits, the physical characteristics of the site may also make it difficult to vegetate. Thesesites
are often low in organic matter and have a low water-holding, buffering and cation exchange capacity.
The addition of organic matter, such as compost, improves these characteristics making the area habitable for
vegetation and soil biota. When applying compostto mine sites in which high levels of heavymetals exist, the addition
of cunpost has been shown to help "tie up" these contaminants, making them less available for plant uptake and allowing
healthy plant growth.
171
A dense vegetative cover should also reduce the movement of contaminants through surface runoff. These sites
are corrsided to be a
d have long been ignored in tbe past. Keeping this in mind, and lcnowingthat these sites
are not easily accessible to the public, it seems feasible that even low quality composts could be used in the renovation
of thme si&. Evm compost codaining large quantities of foreign material, excluding large quantities of film plastic, are
probably acceptable for use.
Film plasts may remai0 on the soil wufece d be ingested by animals. Compost which contains a large amount
of WBBd seeds and is considered unstable may also be acceptable for this use. In this application, any product that is low
m cost end rich in organic matter is eccelfable. Although si@cant quantities of compost have been used on reclamation
s h , co111po6t usage has been limited in this application because of economic, regulatory and environmental constraints.
LandfilLF.Compost bas beea used successfully in landfill reclamation, closure and in daily cover. Many special
mixea have beea tested and u
sed,including compost/saod mixes, composthoil mixes and compost alone. Although qual~ty
codrd may be slightly less important for landfills due to their already stigmatized nature, the compost still has to be of
high enough Mty to support plant life. After all, establishment of vegetation is a key objective for final closure of
landfills.
some. municipal solid waste composting companies haveplanned from the outset to use their compost as daily
cover in adjeced laodfills and have oped mt to take an aggressive marketingapproach. This strategy works well because
by composting the organic fraction of the solid waste stream, a large volume of solid waste can be diverted from the
laodfill. “he composting process itself will then si@cantly reduce the volume of that organic material through
blodegredeboo. As a result, this strategy can extend the life of the landfill and create a ready market for municipal solid
W M b COmpOSb.
Consulting engineers can usually assist in identlfying and quantifying soil requirements and site conditions so
U cunpost mixtures used for closure or slope stabilizationcan be mixed accordingly. Compost still should be enough
to support plad growth, low enough in heavy metals to meet state standanls and possess physical properties which allow
it to be easily spread or blended.
Canpostswhichdomtarpportvegetationmaybeusedfor~coverormixedwithothermaterialsuchassand
or mil and used as daily cover depending on state regulations.
Greeobarse, container and field nursery growers have a long history of using organic products, such as wood
W,end peat tmss, as well as various &r organic amendments in the production of their ornamented crops. Because
research has shown that composts of various feedstocks perform well in conjunction with h e products, its use in
waunercial operations has grown.
Compost bas p v m to be a cost benefit to growers, in that it can often be purchased at a lower cost than other
organic amendments used in the industry. Many compost manufacturers have proven that they can produce a product
which is of high enough qual19and which is consistent enough for usein this industry.
The 4ualpy end consistency of the product used by growers is of the utmost importance because of the valuable
crops they grow, and because these c r o p are grown in a closed system.
G r e d e s . Greeobouse p
w
e
r
shave been using more composted materials since the industry shifted toward
using soil-less growing media several years ago. Compost is used as one of the organic components to soil-less mixes,
usunlly used at a rate of 10 percent to 25 pefesot of the mix
on the c r o p being grown. A si@cant amount
of resePrch has beem performed demonstrating the use. of biosolids compost in w i n g mixes; therefore, composted
biomlids is probably the most popular compost used in growing operations.
w
n
ig
Compost has also been used because it is a local, high qual~tysource of organic matter and is usually less
expensive than other organic components used in growing mixes. The compost used by growers must be extremely
consistent, stable, have a pH preferably between 6.0 and 6.5, be low in soluble salts and free of weed seeds.
Compost has also been found to codain nahually occuning disease suppressive properties which have the ability
to help control many soil-borne diseases. Because growing mixes are oftea adjusted to suit the pH needs of the crops being
prabced, compost which has had Lime added to it during the production process is often not used. The addition of lime
to t
b compost makes it much more difficult to buffer (its pH), and the use of this material may cause trace elements in
the growing mix to be immobilized (Gouin 1992).
Gnuahers. Compost has beeo widely used m the pduchcm of codaioer-grown nursery stock.Normal compost
inchrsion mtea vary, but generally, a 25 per~edto 33 percent inclusion rate seem to be average. It is imperative that any
extra kbor required to edd compost M an additional ingredient to the container mix be offset by savings in the overall
cost of the mix. Research with bioeolids compost indicates a good success rete in the replacement of peat moss in the
production of woody ommedals (Smith 1990).
Some suppmsion of disease associated with the production of specific plant species has also been documented
wben cxmpost has been added to codaher media (Hoitinlr 1986). Although the market potential for compost used through
cadPinerpmhrboais~asgreetasmturfapplrabons,asfPrasvohuneused,itdoesrepresentasi~canthighv~e
niche market. The possibility of provtdmg special pH and nutrient adjusted composts or fungus/disease resistant products
M components to container mixes may be a very specialized area for future market development.
Keys to using compost s u c c e s s f u y . m contaioet media include using mediumtextured, w e l l d d , low soluble
salt, stable composts. Due to the hands-on nnh~reof many container operations, contamination of composts with inerts
will
likely be tolerated in the marketplace. Composts have beea known to add valuable micronutrients and improve
plMt vigor &e to water releotioa
However, dangers of rapid material decomposition and shrinkage also exist
which play create slow draining, anaerobic growing conditions if mixes are improperly fomulated or unstable products
are wed.
Ixopemes.
Field. FieLl mntxy p
w
e
mare arrredly using compost in two ways: fieldincorporation and mulching. These
metbods are discussed in detail below.
Nurserymeo are a sqpuficant market for composts, but are quite geographically dependent. For instance, Ohio
has an approximately $1 billion nursery-related business compared tomany other states that have h t e d nursery
production.
Fiekt-barvested llusery stock (ball a d burlap) remove sigdicant nmounts of soil mass and nutrients. As much
250 toas of soil per acre may be lost at harvest (Tyler 1991). Additiody, the n
o
d soil loss from erosion
mrLee replenishing the soil (aodespecially organic matter) a necessity to maintpin productivity.
UI 50 to
often, farmers w
l
i take their fields out of production in order to grow a cover crop, a vegetative cover which
ispbwedidothesoil,mordertoretumva)usblehmusmloJtriedsbecktothesoil.Thislossisestimatedatjustuoder
3 billiontoos per year for all agncuhral erosion, or about 6.7 tons per acre, per year (Kashmanian 1992). Losses in the
nursery may be slightly less due to reduced tillage practices over the life of each crop. Costs associated with using
compo~tcover cropping are competitive whea all factors are considered (Logsdon 1991).
Applications of 2 inches of compost, plowed to a depth of 6 to 8 inches sigmticantly increases organic matter
m native soils.Native clay soils break up easier and form new aggregation as organic matter decomposition takes place.
S a d y soils geaerally hold 25 perced of their weight m water while many composts hold up to 180 percent of their weight
m water (Seattle 1990). Chmxpdy, sandy soils retain more moisture with additions of compost and give plants a better
chpnce for survival during drought conditions.
Compost apphkms p
i
t
a
b
l
y replete m d cover cropping at nurseries by allowing applications, tdlage and
plsdrog of a new crop to OCCUT m a short window of time. Approximately one full growing season can be saved by using
this approach, and the
of organic matter returned to the soil is at least 10 timea the amount delivered by cover
c r o p (Tyler 1991).
173
Compost used in field incorporation programs should be stable, high in organic matter content, low in heavy
metals curl low- in soluble salts. Concerns with heavy metals usually arise when the land may be used for future food or
animal production.
The level of acceptable contamination of the compostwith inerts willdepend on what loading limits are
ecceptable to nurserymen using multiple applications. However, since most field crops have growing cycles of two to
seven years, a build up of inert materials in their soils islessLikelyto
occur than fields receiving yearly compost
applications.
The pH of a compost may be adjusted after application to suit specific needs for various families of crops or
soils. m y nvsetymea prefer a coarse gradeproduct because they feel it help increase field soil friability and provide
adequate aeration for tender rods.
Nurseries can use large quantities of compost by mulching plant rows in field situations. Applications usually
range from 1 to 2 inches. Mulchprimarily conserves moisture, but also helps reduce weed growth, reduce soil
kaqmahm fluctuations and evenhrally add sigruficant amounts of organic matter to the native soils when incorporated
into the soil post barvest. This is especially handy when andher planting is planned for the s a m e field immediately alter
harvest.
Compost used for mulch can be coarse, but must still be able to be worked in and a r o d individual plants if
needed. Nurserymen have mticed that using compost as a mulch in place ofnormal hardwood bark mulch has increased
growth from both improved moisture retention and reduced injury to plants associated with stringier hardwood bark
mulch. Compost screened through a 2-inch screen works especially well (Hendricks 1992).
Heavy mehl cedent should to be within acceptable food chain levels unless the land is never again intended to
be used for food production. Organic contents should be high to aid in the absorption and conservation of water. The
c u t p s t should be stable and may possess a slightly elevated level of soluble salts due to the high leaching potential of
rmlch. However, many salt-sensitive crops such as those planted as bare-root cuttings, may react negatively to high salt
levels. The pH of the mulch will also depend on the requirements of tbe individualcrop being cultivated, but generally
m y be between 5.5 and 8.
The use of COIIIpoBt m roadside developned and mainteoMcs projects continues to grow as more municipal bypmlud derived Compo618 are
Composts ~ t being
e
"specified" M "approved equals" to other organic products
suchastopsoilorpeatmossusedmtbesepojeds.Tbe~i0ytocreate~~forthelargevohunesofcompostbeing
..
p r o d u c e d h a v e l e a d s o m e s t s t e s t o d e v e l o p r e s e p r c h p r o ~ a i m e d agt ~the optimal methods for using compost
on roadside projects.
pduced.
The roadside environment is often hostile. Lack of irrigation, minimum fertilization and the use of road salts
often makes it too difficult for vegetation to persist. The use of compost can improve the environment for roadside
vegelation, giving it a better chance of survival.
Currently, compost is being used on roadsides as a soil amendment in the establishment of planting beds and
a compooed of beckfill mixes for trees and shrubs. In several states, compost is incorporated to improve the organic
mstter coded of soils used on rosdside construction projects, or similarly, in the production of manufactured soils used
for the same purpose.
M
In Europe, canpost bas beene
d
a8 the growing media in "living walls" which border roadsidea and have
been shown to perform well in s o u n d minimization. Compost used in these applications should meet the specifications
d e s c n i earlier, for landscape purposes. However, characteristics which affect product handling, such as moisture
c o d e d , may not be as pertinent in projects where mechanical equipment is used to apply and incorporate the compost.
Additionally, charraderistics whichdeal with aesthetics, such as foreign rnatter content and color, may not deter
use - especially if the product is used as a soil a m e W rather than for surface application.
The application of compost for weed and erosion control on roadsides warrants more discussion becauseof the
promising results being documented on an ongoing basis.
,
Weed Control. In many states, coarse composts are approved for use on roadside maintenance projects as a
mrlch for w e d control. E v a thcugh the materials are high in organic matter and hold moisture well, they have also been
k n d to be effective in
weed growth. This is probably due to the dark color of the products which absorb heat,
causing its' surface to readily dry out (Kilbourn 1991).
codrow
This hot, dry surface & it difficult for weeds to establish aod, as long as the product is properly composted
befmits use, the umpost itself sbuukl be weed-free. Compost used in this application should be coarse in texture, weed-
free a d low in inerts, as well as aesthetically appealmg. The product should also possess characteristics which make it
easy to handle and s p d . It is possible that the product could be mechanically blown onto areas that are difficult to
access (e+, steep slopes).
Erosion Control. Compost may also be used as a surface application to slopes and embankments in order to
erosion. Once again, coarse composts have been shown to work well in this application as have some municipal
solid wpste cOmpOds because of their absorbent nature. Coarse, biosolids-based composts (containing a high percentage
of wood chips) have shown excellent results applied as a surface application on 2: 1 slopes (Rattie 1992).
A mixture of coarse compost and sand, used in similar conditions, has shown similar results. The erosion
r d x h o n capabilities of this mix have been a t t n i to its ability to allow for improved water infiltration. The erosion
c o d r o effects
~
of coarser
applied as a surface application, have been a t t n i e d to the ability of the product
to "ladtogether", creating excellent coverage over the soil surface and having the density and physical structure which
resists surface erosion.
Accordrng to research, the addition of coIIIpo6t reduces erosion m three ways (Tietjen 1%9). First, soil structural
stnm& ia inmased k l m g to beigbteoed resistance to erosional forces. Second, the compost mulch near the soil surface
absorbs the eoergy of mdmp impsd and third, soil water holding capacity is increased, providing less water for runoff
(Tietjen 1969).
In both weed control and erosion control, further research is and will be required to prove theories regarding
the effectiveness of these products in these applications.Compost used in erosion control should have similar
characteristics to products used in weed control, except for one major difference -- its ability to grow vegetation.
In specdic applications, where erosion control is desired, a compost which is considered unstableor contains
substances which may be detrimeotal to plpd growth, may actually prove to be a benefit in this application. However,
m meny erosion codrOl practc
i ee,the growth of weeds on the sod surface may not be considered negative inthat the most
practical aod effective method for controlling erosion is by densely vegetating the soil surface.
Ahhough there are m y other pdeotially large markets for compost use, two in particular may prove to be the
moat importad to develop as more organic residuals are transformed into compost. Both the agricultural sector (food
production) and the general pblic are large potential markets for composts of various feedstocks.
The potedral acreage d remums codrolled by these groups may d e them the key to solving our country's
solid waste management challenge. Composting will be used as a means to manage a large portion of the residential,
commercial aod agricultural organic waste stream. The industry's growth will be closely related to our success in
developing large, long-term markets for the resultant products.
Agriculture. The agriculture market has been considered by some to be the "dumpinggrounds" for composts
which am mt of the highest quhty. It sbould be noted that farmers are usually in tune with their soils, often working with
agronomists to determine fertilizer loading capacities, etc. Although many perceive that composts used by this market
sector may be lower in qual~tythan in other sectors, lower qual19products which contain inert materials (i.e., glass,
175
p i a s t m , etc.) w
i
l be more
recognuable in soil over t i m e . Whether American farmers will allow this to take place is yet
tobeseal.
Market potential in agriculture is by far the largest (Slivka 1992), but many farmers are also turning to
cornposting as a safe method to handle conventional farm by-products.If given the option, farmers w
l
iliterally use the
products they produce instead of buying other compost products. One thing is for sure, the value of compost as a tool
in sustainable agriculture is sighcant. It has been s h o w n that the reduction of traditional fertilizer and pesticide
applications can be attributed to the benefits associated with compost.
Composts used in agncuhm umt be safe emugh to avoid pemyrneot contamination of soils with inerts or heavy
may be applied in unstable state, however, for maximum effectiveness theywill require field
aging before plantmg. It is wise not to plant immediately following the application of unstable composts due to nitrogen
unmobdization or low oxygen concentrations that prevail in soil immediately after incorporation of such composts.
d.
Some
The use of composts in agriculture has been shown to offer a variety of benefits, one of the largest being
reduction of erosion (Kashmanian 1992). High intensity farming erodes valuable topsoil faster than it can accumulate
~ t u d l y(Kashmanian 1992). By adding compost on a regular basis, farmers can maintain healthy soils and remain
profitable.
Loeding limits need to be established for agricultural uses of ail types of composts with respect to macro- and
micronutrients, heavy metals, salts and inert contaminants. The potential amount of compost generated from source
of farm manures (and,therefore, possible
segerateed organic wastes, about 180 million tons, is dwarfed by the
c o m p o s @ which may be produced. About 1.4 billion tons of manure are disposed of annually (Kashmanian 1992).
Although m y studies have been perfortned illustrating the benefits of compost use on agricultural land, most
of the marked still refuses to pay the sigxulicad cost associated with the purchase of application of these products. In
ge.mral, normal farming practices can deplete more than 50 percent of a d i v e soil‘s organic matter over time (Lucas
1978). Also, losses of humus and other soil nutrients from erosion are sigxulicant in agriculture,but compost can help
replenish these by being added on a regular basis.
Studies show that the regular application of raw agricultural materials, such as manure, do not readily change
the organic matte+ coded m soil over many years (Lucas 1978). Soil humus is lost on a regular basis to soil erosionand
soil micro tlora, aod is also cawetted to carbon dioxide and water through natural processes. In the United States alone,
3.6 billion metric tons of topsoil are lost to erosion annually, some of that being natural humus (Luau 1978).
Most farms, m an attempL to ret@ soil b from e
ros
o
in,lsnd apply the majority of their manures. However,
mny of the m u m s currently being applied may contn’bute to non-poiat source pollution because they are more easily
emded a d leeched than products which are composted prior to application. Composted manures and farm by-products
m y help d u c e non-point source pohtion by converting nutrients into less leachable forms.
Compschoamay be reduced by the addition of compost or organic matter to the soil,thus helping reduce runoff
d erosion From farm fields. Depending on application rates, the addition of compost to agricultural laads can increase
organic mattex dmmatically, whereas applicatiam of raw manures or green manures usually add less total organic matter.
The number of benefits associated with the addition of compost to agricultural fields seem to far outweigh the
exha effort and associated costs. However, an educational system is needed to lead the way for market development in
this large market.
By lodaog at compost pwhrds BB natural resources which can be used to help offset losses of soil from erosion,
we catmot forget tbat the base soils that receive +cations are also one of our largest natural resources. The use of high
@
t
ycompost can protect this irreplaceable resource.
HcRncowncrs. As the general public has become more educated about the benefits of using compost, its usage
has increased dramatically. Public interest in organicgardening and sustainable agriculture will also improve the
176
marketability of compostedproducts. T e a c h g thegeneralpublicwhatisfact
especially when it comes to health and s a f e t y issues, is of utmost importance.
and whatis fiction about compost,
curredly, the most poplar composts being used by homeowners are yard trimmings and various animal manure
based products. These have been marketed in bulk and bagged form by nationally known companies. In many areas,
biosolids c a u p s t bas also b e a marketed to homeowners with great success, however, it can be somewhat moredifficult
at first due to the natural stigma attached.
Municipal solid waste compost will, no doubt, be more dficult tomarket to homeowners than other types of
co1IIpoBt.This is because many MSW m m p t ~
am not as nestbetically appealrng as other types of compost. Most likely,
only the MSW composts which are of the highest qual~tywill gain wide acceptance with 'John and Jane Q. Public'. It
possesses many of the same benefits as other composted materials possess and can be used in much the same manner.
composts which am marlreted to homeowners IIllst have a texture which makes them easy to work with and must
have an attractive look. They must be consistent, free of weed see& and objectionable odor. If the product is high in
sokrble sdts or is unstable and causes plant damage, homeowners will become negative to all composts for a si&lcant
length of time.
Since homeowners do not have a technical background in the production or use of compost, the product we
qddy.It is widely believed that the key to creating long-term markets for compost
depends upon creating acceptance with the general public (homeowners).
&to thean mst be of the
.
h
e
i
e e
the
Of
appllcahon grows, ibecomes increasingly more important that we understand how
various canpxts m beat used, as well as understand how specific endusers use the product and for what reasons. For
this knowledge to grow, continued monies must be made available for research to develop new uses for our compost.
ResePfch must also determine the best methods and application rate, for the use of compost in current applications.
As tbe production of compost increases, largely due to more scrutiny of our waste management practices, the
need for knowledge and plblic support becomes a national and international issue, rather than a regional one. This fact
makes it extremely importad that as more research is completed and information obtained, that the data be shared
throughad the lnrhLstry in a way which wli benefit all interested parties. Accomplishing this goal will benefit us in many
ways from avoiding the duplication of research, to improving public relations.
REFERENCES
R.A.,"SMge Compost: Can It Make Athletic Fiekis More Playable?" Lawn & Landscape Maintenance, July
1991, p p . 46-52.
&&,
Angle, J.S., D.C. Wolf and J.R. Hall III, "Turfgrass Growth Aided by Sludge Compost". Biocycle, Nov.-Dec. 1981,
pp. 40-43.
Personal Interview with Francis Gouin, 21 May 1992.
Personal Interview with Bill Herwlricks, Klyn Nurseries, Aug. 10, 1992.
Hoitink, H.J., Kuter, G.A., Effects of Compost in Growth Media on Soilborne Pathogens. The Role of Organic Matter
in Modern Agriculture, ISBN 90-247-3360-x, 1986.
Kashmanian, R.M., Composting and Agricultural Coverage: Part I, State, Local and Agricultural Activities and
Composhng and A
m Coverage: Part II, Implications for Reducing Water Pollution for Livestock Operations and
Erosion, publishing pending.
Personal Interview with Jay Kilbourn, Resource Conservation Services, Inc., 17 July 1992.
Logsdon, Gene, Plant Nurseries Cut Costs With Compost, BioCycle, May, 1991.
Lucss, R.E. aod Vitosh, M.L., Soil Organic Matter D p m ~ ~Michigan
s,
State University Agricultural Experiment Station
Research Report, Nov., 1978 32.91.
McCoy, E.L., Assessment and "Renovation of Residential Soils", Urban and Sports Turf Soil, 2ad Edition, 1990.
N e h , Eric B., the Biological Control of Turfgrass Disease, Golf Course Management, April, 1992.
f
l
d Rattie, Compost Management, Inc., 17 July 1992.
Personal Interview with A
Seattle Solid Waste Authority, Ceder Grove Compost Users Guide for Landscape Professionals, 1990.
Shka, McCkrre, Buhr, Albrecht. Potential U.S. Applications for Compost Applications. Commissioned by the Proctor
and Gamble Co. for t h e Solid Waste Composting Council, Jan., 1992.
Smith, E.M., and S.A. Treaster, Composted Municipal Sludge From Two Ohio Cities for Container Grown Woody
1990.
ornamentals,
EM.,aod S.A. Treestef 1992. Production of Annuals and Perennials Grown in Soil Amended and Mulched with
cornposted Landscape waste.
Smth,
Tw,
C., d S.A. Hart, 1%9. Compost for Agricultural Land J o u d San. Eng. Division, Proc. American Society Civil Eog. lS(SA2): 269-287.
Sopper, W.A., "Long-Term Effects of Reclamation of Deep Coal Mine Refuse Banks with Municipal Sewage Sludge,"
W National Symposium on Mining, Sept. 22-27, 1991 (Lexington, Kentucky: University of Kentucky).
Tyler, R., Benefits of Using Compost in the Nursery, The Wlckeye, January, 1991.
Copyright 1992 by Ron Alexander aod Rod Tyler
AU Rights Reserved
This &
l
eis a m o d i version which was first plblished by Lawn & Landscape Magazine in its November 1992 issue.
I78
AUTHOR’S INDEX
I70
ADDRESSES FOR PRII\fARY AUTHORS
R Allen Boyette, P.E.
E & A Environmental Consultants, Inc.
1 130 fildaire Farm Road
Suite 200
Cary, NC 2751 1
Phone: 9191460-6266
Fax:
9 191460-6798
"Biofilter Economics and Performance" 6y R. Allen
Boyeffe,PE
Ron Alexander
1 130 fildaire Farm Road
Suite 200
C q , NC 2751 1-4561
Phone: 9 I914604266
Fax:
91 914604798
"Using Compost Successfully" 6y Ron Alexander
and Rod Tyler and "Lnnovation and Update in
Compost Marketing: A Year in Review" by Ron
Alexander
Patrick Byera
SW Authority of West Palm Beach
7501 N. Jog Road
West Palm Beach, FL 334 12
Phone: 56 1l640-4OOo ext. 46 1 1
Fax:
561-683-4067
"Agitated Bin Composting, Start-up and
Operation" by PatrickD.Byers
Anita Bahe, Ph.D.
206 Beechtree Drive
Cary, NC 275 13
Phone: 9191677-9985
Fax:
9191677-9985
"Develdping and Facilitating Green Industry
Markets for Composted Organic Materials" by
rlnrta R. Bahe, Ph.D.
Keith Baldwin
75 Hawthorn Place
Chapel Hdl, NC 275 14
Phone: 9 191542-01 22
Fax:
9 191515-7494
"Trace Metal UptakdAvailability From Three
Municipal Composts" by K.R. Baldwin andJ.E.
Shellon
Chris Christenberry
Verrnicycle Organics
29 10 Selwyn Avenue
Suite 123
Charlotte, NC 28209
Phone: 704/33 1-9909
Fax:
704/33 1-0059
"The Effect of Large Scale Vermicomposting ona
Corporate Hog Farm" by Chris Christenbeny,
Michael Ehlardr and Tom Cht-isrenbeny
Ted Bilderback
NCSU
Dept. of Horticultural Sclences
Raleigh, NC 27695-7609
Phone. 9 1915 15- 1201
Fax
91
915 15-7747
"Evaluation of a Compost Based Potting Mix for
Commercial Nurseries" 6>,Frotlh- Franc~osr,Ted E.
Bilderback and Ifillianr G. Lord
Archer Christian
VA Polytechnic Institute andState University
424 Smyth Hall
Blacksburg, VA 2406 1-0403
Phone: 5401231-9801
Fax:
540123 1-3075
"Development of a Leaf Distribution Program for
On-Farm Composting" bv Archer H.Chr-ufinnand
Gregory K. Evanylo
180
ADDRESSES FOR PRIMARY AUTHORS (CONTINUED)
Philip B. L e g e
The Proctor & Gamble Company
6 I o 0 Center I411 Avenue
Cincinnati, OH 45224- 1788
Phone: 5 131634-6876
Fax:
5 1316341434
'Cornposting Process Models and Model
Applications" by Philip B. Leege
Lori Cunniff
Fibrestone T e c h c a l Affiliates, Inc.
7480 SW 127 Street
Miami, FL 33156
Phone: 305038- 1027
Fax:
305078- 1377
"The Reduction of Fish Processing Wastes to
Provide a Marketable Product Through
Composting" by Lori CunnflandJoseph M.
Edwardr
Ted Lyon
NCDEHNR Division of SW Mgrrt.
PO Box 27687
Raleigh, NC 276 1 1
Phone: 919/133-0692 e a . 253
Fax:
919/133-4810
"Changes in the North Carolina Compost Rules"
by Ted L p n
K C . Das
University of Georga
Ag. & Environmental Sciences
Dnftmeir Enpneering Center
Athens, GA 30602-4435
Phone: 706i542-8842
Fax:
. 7061542-8806
"Increasing Invessel Efliciency at a Commercial
Biosolids Composting Facility: Practical Aspectsof
Moisture Loss Estimation and Control'' by Keshav
Das, Ph.D and HaroldM. Keener, Ph.D.
West McAdams
Charleston Co. Extenslon Office
259 Meeting Street
Charletson, SC 29401
Phone: 803ff 22-5940
Fax:
Patrick DavisIJudy Kincaid
PO Box 12276
RTP, NC 27709
Phone: 9191558-9392;9191558-9343
Fa:
9 191549-939O
'Cost Savings Through Regional Biosolids
Composting in the TriangleRegion" by Patrrck
Davis and Ju& Kincaid
803n22-5944
'Compost Stability Determination" by Mannrng W.
h4cAdams and Richard K. White
Tim Muirhead
PSG
408 North Cedar Bluff Rd.
Suite 35 5
Knoxville, TN 37923-361 1
Phone: 4231693-5579
Fax:
Greg Evanglo
VA Polytechnic Institute and State Umversity
424 Smyth Hall
Blacksburg, VA 2406 1 -0303
Phone: 540/23 1-9139
Fax:
540123 1-3075
"Papermill Sludge Composting and Compost
Utilization" by Gregory K. Evanylo, W.Lee Daniels
and Ren Sheng Li
4231693-0329
'Air Emissions Testing and Odor hlodelling" by
Tim .i/uirhead, Todd Willianrs and Graham GIllqv
Brooks Mullane
NC Zoological Park
4401 Zoo Parhway
Ashboro, NC 27203-94 16
Phone: 91Oh379-70oO
Fax: 10/879-2891
9
"Case Study -TheNC Zoo MSW Pilot Composting
Project" by Brooks .Cfullane and Dr. Bob Rubin
181
E
ADDRESSES FOR PRlMARY AUTHORS (CONTINUED)
Mitch Renkow
NCSU D e p t . of Agncultural and Resource Economics
Box 8109
Raleigh, NC 27695-8 109
Phone: 91 915 15-2607
Fax:919/5
156268
"Municipal Solid Waste Composting: Does It
Make Sense?" by Mrtch R r n b w and.4. Robert Rubln
Robert Spencer
Ekdmmster Bioconversion Corp.
145 Church Street
Suite 20 1
Marietta, GA 30060
Phone:
7701422-4455
7701424-8131
Fax:
"Enhanced Biofdter Design for Consistant Odor
and VOC Treatment"by Lany Finn and Robert
Spencer
Julie Shambaugh
commandlng General
ACIS EMD
Rodney Tyler
BFI Lorain County Resource Recovery Complex
43650 Route 20 East
Oberlin, OH 44074
Phone: 2 16B70-083I
Fax:
2 l6/774-4808
"The Economic Angleof the Compost Business" by
Rodney W. Tyler
Marine Corps Base
PSC Box 20004
Camp Lejeune, NC 28542-0004
Phone:
9101451-5878
Fa:
9101451-1 I64
"Solid Waste Pilot Composting: Results and
Lessons Learned. Tbe !+larine Corps Base, Camp
Lejeune Experience" bv Julie .4. Shambaugh and
Penny A4acaro
Todd Williams, P.E.
1 130 Kildaire Farm Rd.
Suite 200
Cary, NC 27511
Phone: 91914604266
Fax:
9 1914606798
"The Big and Small of Biosolids Composting" by
Todd Williams, P.E., R. .411en Boyette, P.E.,Eliot
Epstein. Ph. D..Scott Plett and Curtis Poe, P.E.
James Shelton
NCSU Mountain Horticulture Crops
Research and Extension Center
20 16 Fanning Bridge Rd.
Fletcher, NC 28732
Phone:
7041684-3562
Fa:
7041684-87 15
"Cornposted Biosolids for Agronomic and
Horticultural Crop Production"by James E.
Shelton, J.R. Joshi and P.D. Tare
Azu Shiralipour, Ph.D.
University of Florida
130 Newins-Ziegler Hall
PO Box 1 I0410
Galnesville, FL 326 1 1-04 I O
Phone: 352/392-1511
3521392-2389
Fa..:
"Compost Effect on Cotton Growth and Yield" by
.4ziz Shiralipour, Ph.D andEliot Epstein, Ph.D.
182
TITLE INDEX
Agitated Bin Composting, Start-up and Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Patrick Bvers
71
Air Emissions Testing and Odor Modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tim Murrhead7 Todd U'illiams and Graham Gilley
33
Big andSmall of Biosolids Composting
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Todd Il'~llrarrrs,R . .4Ilen Boyette, Eliot Epsteln, Scott PIett and Curtis Poe
58
. . . . . . . . . . . . . . . . . . . . . . .
Biotilter Economics and Performance
H . .4lIer1 Uoyetre
19
Case Study - The NC Zoo MSW Pilot Compost Project
Brooks ,Lfullatle and Bob Rubm
............................
. . . . . . . . . . . . . . . . . . 35
Changes in the North Carolina Compost Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ted Lvon
34
Compost Effect on Cotton Growth and Yield
.4ziz Shirallpour and EliotEpstein
108
Compost Stability Determination . . . . . . . . . . . .
Manning It.',
,bicAdams and Richard K. White
144
Composted Biosolids for Agronomic and Horticultural Crop Production
James Shelton. J.H. Joshi and P.D. Tale
Composting Process Models and Model Applications
Philip B. Leege
.............................
................................................
116
9
Cost Savings ThroughRegional Biosolids Composting in the TriangleRegion
Patrick Daws andJudy Kincaid
80
Developing and Facilitating Green Industry Markets for Composted Organic Materials
Anita Bahe
95
Development of a Leaf Distribution Program for On-Farm Composting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Archer Christian and Gregory Evanylo
53
Economic Angle of the Compost Business
Rodney If'. Tvler
.........................................................
1
Effect of Large Scale Vermicomposting ona Corporate Hog Farm . .
Chris Christenberry,hficlttTel Edwards and Torn Christenberty
150
Enhanced Biofilter Design for Consistant Odor andVOC Treatment
Robert Spencer urd Larry Finn
28
TITLE INDEX
Evaluation of a Compost Based Potting Mix for Commercial Nurseries
Ted Bilderback, Frank Franciosi and IVilliatn G. Lord
Increasing Invessel Emciencyat a Commercial Biosolids Composting Facility: Practical
Aspects of Moisture Loss Estimation and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Keshav Das and Harold,if. Keener
Innovation and Update in Compost Marketing: A Year in Review
Ron A lesander
102
...............................
136
17
..................................
Municipal Solid Waste Composting: Does It Make Economic Sense?
.Witch Renkow und.3. Robert Rubin
87
Papermill Sludge Composting and Compost Utilization
..........................................
Gregoty K. Evaydo, If’, Lee Daniels and Ren Sheng Li
Reduction of Fish Processing Wastes to Provide a Marketable Product ThroughComposting
Lori Cunnrf/and Joseph.if. Edwards
124
.............
Solid Waste Pilot Composting Project: Results and Lessons Learned. The Marine Corps Base,
CampLejeuneExperience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Julie Shambaugh and Penty hfascaro
39
44
Trace Metal UptakelAvailability From Three Municipal Composts
K.R. Baldwin and J.E. Shellon
155
Using Cornposting Successfully . . . . .
Ron Alexanderand Rod Tder
167

Composting in the Carolinas - Proceedings of the 1996

Transcription

Similar documents

In-Vessel Composting Options For Medium

Azomite - naturesfootprint.com

Kasiche, La Parcela and Wayúumana, Colombia

Event recycling brochure

attachment - US Composting Council

EZGreen sales sheet_Dec12.indd

composting - closing the loop at home - jpspn

Kasiche, La Parcela and Wayúumana, Colombia

tifblair® centipede - Super-Sod