a sustainable decision support system for the demanufacturing
Transcription
a sustainable decision support system for the demanufacturing
A SUSTAINABLE DECISION SUPPORT SYSTEM FOR THE DEMANUFACTURING PROCESS OF PRODUCT TAKE-BACK BASED ON CONCEPTS OF INDUSTRIAL ECOLOGY By Sirine A. Saleem Bachelor of Industrial Engineering University of Jordan, 1997 Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in the Department of Mechanical Engineering College of Engineering & Information Technology University of South Carolina 2001 ________________________________ Department of Mechanical Engineering Director of Thesis ______________________________ Department of Mechanical Engineering 2nd Reader __________________________ Dean of The Graduate School i DEDICATION To My Mother For Your Everlasting Love, Patience, and Sacrifice I Love You To My Husband and Daughter Ayman and Yasmine For Your Continuous Support, Love, and Understanding With All My Love ii ACKNOWLEDGMENTS Throughout my master’s process the list of people who contributed to my success grew larger. First of all, I would like to thank my advisor, Dr. Wally Peters, whose guidance motivated my interest in Industrial Sustainability. He has been an excellent teacher; always there to listen to me and give me sincere advice, his confidence in LSS and in me as part of this team brought out the best in me. Working with him has been extremely valuable to me. Besides my advisor, I would like to express my honest gratitude to Dr. Bayoumi for being member of my committee and his invaluable help, guidance, support and understanding throughout my master’s process. Moreover, I would like to thank Dr. Rocheleau for being a member of my committee. And my thankfulness goes to Dr. Khan without whom I would have never been directed to Dr. Peters, and for his support and nourishing me with some very useful guidance during the course of my research work. For her invaluable help and assistance throughout my research and writing my thesis, I am forever grateful to Lynn Odom without whom all this would have never been possible, she has been a precious source of knowledge, guidance, support, she had confidence in me when I doubted my self, she was always there to talk about my ideas, to proofread and to make up my thesis, without her everlasting encouragement and help I could not have finished this thesis. More importantly, she has always been a good friend and will always be my best friend. iii I feel very fortunate to have Beth Locklear as my thesis mate who shared endless laughter and worries. Without our support for each other, belief in Industrial Sustainability, and determination to make this work come true, this work would have never been done. Beth, we made it! I would also like to thank Jamie Russell for his help in calculations and giving me good ideas and entertainment. Patience Russell, Katty Chen, David Grigg, Tara Alden for your legal help, Emily Peterson you are truly wonderful it was nice working with you, and the team of LSS. I am grateful to Excel Comfort Systems, Inc. for their financial support, especially, Mr. Johnny Johnson, for his enthusiasm and actively supporting my research. I am thankful to Gene Bishop, Midlands Tech, for arranging an air conditioner disassembly workshop that helped a lot in creating the model. I am also grateful to the faculty, students, and staff in the Department of Mechanical Engineering for your continuous help. I have saved the best for last. I could not have reached this stage without the support of my family. I am grateful to my mother for her influence, encouragement, and everlasting sacrifice .You have set high standards for me to look up to. I am grateful for everything you did in shaping me as the person who I am now. I have to mention my special appreciation for my husband Ayman El-Kattan I would not have had the courage or strength to continue working on my thesis without your support. Thanks for being a supporting husband, and making the possible to give me the chance to work on my research and finish my master’s. Finally I would like to thank my adorable Yasmine for being a good understanding patient baby, I love you all! iv ABSTRACT Industrial ecology, the science of sustainability, is an evolving concept that offers a unique approach to the design of industrial products and processes, and the implementation of sustainable manufacturing strategies. It aims to incorporate the cyclical patterns of ecosystems into the design phase in order to achieve a pattern of industrialization that is not only more efficient, but also in compliance with the laws of Mother Nature. This designed industrial system intends to generate no adverse environmental effects, since it will eliminate potential causes in the design stage. The product take-back system is a strategic industry response for moving toward sustainable development based on the concepts of industrial ecology. The concept is to shift the industry from take-make-waste system that assumes infinite sources of raw material and sinks for the industrial wastes into an industrial ecosystem, which operates successfully in a cyclical manner. It mimics Mother Nature in recognizing that “waste equals food”, and what goes “out” must finally come “in”. This system promotes and sells the functionality of the product rather than the product itself. In this thesis, three comparative scenarios are investigated for the Heating Ventilation and Air Conditioning (HVAC) industry. The scenarios are either already existing or theoretically proposed. The first is the current manufacturing process, using extracted raw materials (primary mining), the second is secondary mining (product shredding), and finally the demanufacturing process (product disassembly). The environmental, economic and social dimensions of sustainability are studied using manufacturer or hypothetical data, or information collected from literature. This work v was carried out in conjunction with a local HVAC manufacturer, thus all the generated data and conducted analysis is contributed from their manufacturing processes. At the end of this study, the most sustainable process that fulfills the requirements of industrial ecology is identified. vi TABLE OF CONTENTS DEDICATION..............................................................................................................................................II ACKNOWLEDGMENTS.......................................................................................................................... III ABSTRACT ..................................................................................................................................................V TABLE OF CONTENTS ..........................................................................................................................VII LIST OF TABLES .......................................................................................................................................X LIST OF FIGURES ..................................................................................................................................XII CHAPTER 1: INTRODUCTION ................................................................................................................1 1.1. BACKGROUND ..................................................................................................................................1 1.2. CONCEPT OF SUSTAINABILITY .........................................................................................................3 1.3. CONCEPT OF SUSTAINABLE DEVELOPMENT .....................................................................................5 1.4. INDUSTRIAL ECOLOGY .....................................................................................................................9 1.4.1 1.5. Emulating Mother Nature......................................................................................................10 INDUSTRIAL METABOLISM .............................................................................................................12 1.5.1 Types of Industrial Ecosystems..............................................................................................15 1.6. INDUSTRIAL SYSTEM MODELS OF THE 21ST CENTURY ....................................................................17 1.7. THE PRODUCT TAKE-BACK MODEL ..............................................................................................18 1.8. THE FOCUS OF THIS THESIS ............................................................................................................20 CHAPTER 2:THE PRODUCT TAKE-BACK MODEL ........................................................................21 2.1. BACKGROUND ................................................................................................................................21 2.2. DEVELOPMENT OF A PRODUCT TAKE-BACK SYSTEM ....................................................................22 2.3. DRIVERS FOR APPLYING A PRODUCT TAKE-BACK SYSTEM ...........................................................26 2.4. IMPLEMENTING PRODUCT TAKE-BACK SYSTEM IN THE U.S. .........................................................27 2.4.1 The Battery Industry ..............................................................................................................27 2.4.2 Xerox.....................................................................................................................................28 2.4.3 Interface.................................................................................................................................28 2.4.4 Siemens and Nixdorf..............................................................................................................30 2.4.5 Rheem ....................................................................................................................................31 2.5. SUMMARY ......................................................................................................................................31 vii CHAPTER 3: DECISION SUPPORT MODEL FOR THE DEMANUFACTURING PROCESS ......33 3.1. INTRODUCTION ..............................................................................................................................33 3.1.1 3.2. PRIMARY MINING PROCESS SCENARIO ..........................................................................................35 3.2.1 3.3. The Methodology for Analyzing Material Extraction............................................................39 SECONDARY MINING PROCESS SCENARIO .....................................................................................49 3.3.1 3.4. Materials Analysis .................................................................................................................34 The Methodology for Analyzing Secondary Mining Process.................................................52 THE DEMANUFACTURING PROCESS ...............................................................................................54 3.4.1 Remanufacturing ...................................................................................................................54 3.4.1.1 3.4.2 3.5. The Operations of the Remanufacturing Process............................................................................. 56 The Methodology for Analyzing the Demanufacturing Process Model .................................60 3.4.1.2 Check-in .......................................................................................................................................... 60 3.4.1.3 Disassembly .................................................................................................................................... 61 3.4.1.4 Cleaning .......................................................................................................................................... 64 3.4.1.5 Inspection and sorting ..................................................................................................................... 64 ECONOMIC COST ............................................................................................................................65 3.5.1. Direct Cost ............................................................................................................................66 3.5.2. Environmental hidden costs (external costs) .........................................................................67 3.6 SUMMARY ......................................................................................................................................67 CHAPTER 4: RESULTS ............................................................................................................................69 4.1. THE CURRENT MANUFACTURING PROCESS SCENARIO ..................................................................69 4.2 THE SECONDARY MINING PROCESS SCENARIO ..............................................................................77 4.3. THE DEMANUFACTURING PROCESS SCENARIO ..............................................................................85 4.3.1 4.4. Overhead of the Demanufacturing Process...........................................................................90 ECONOMIC COST ............................................................................................................................99 4.4.1 Calculation of Direct or internal cost ...................................................................................99 4.4.2. Calculation of the environmental hidden cost .....................................................................102 4.4.3. Total Cost ............................................................................................................................103 CHAPTER 5: DISCUSSION OF RESULTS ..........................................................................................104 5.1. INTRODUCTION ..............................................................................................................................104 5.2. ENVIRONMENTAL SUSTAINABILITY ..............................................................................................104 5.2.1 Carbon Monoxide ...............................................................................................................105 5.2.2 Carbon Dioxide...................................................................................................................106 5.2.3 Sulfur Dioxide .....................................................................................................................107 5.2.4 Nitrogen oxides ..................................................................................................................109 5.3. ECONOMIC SUSTAINABILITY .......................................................................................................111 viii 5.3.1 5.4. Economic Cost.....................................................................................................................114 SOCIAL SUSTAINABILITY .............................................................................................................115 CHAPTER 6: CONCLUSIONS AND RECOMMENDATIONS..........................................................118 6.1. RESEARCH RESULTS .....................................................................................................................118 6.2. EFFECT OF THE DISASSEMBLY OPERATION ON OTHER AREAS .....................................................120 6.3. PRODUCT DESIGN ........................................................................................................................121 6.3.1 Sustainable Product Design..................................................................................................122 6.3.2 Design for Disassembly ........................................................................................................123 6.4. GENERAL RECOMMENDATIONS ...................................................................................................124 6.5. FUTURE WORK ...........................................................................................................................125 6.6. CONCLUSION .............................................................................................................................127 REFERENCES ..........................................................................................................................................129 APPENDIX A-DERIVATION OF ENERGY RELATED AIR EMISSIONS .....................................133 APPENDIX B-TRANSFORMATION OF CO INTO CO2 EMISSIONS CALCULATIONS...........136 APPENDIX C- CALCULATIONS OF CO2 EMISSIONS OF ‘DE-BRAZING’ OPERATION........138 ix LIST OF TABLES Table 3.1: Materials Used in Air Conditioner Unit. ......................................................................................34 Table 3.2: Energy Source Percentages. .........................................................................................................41 Table 3.3: The Reduction Factor of the Secondary Mining Process ............................................................52 Table 4.1: Air Conditioner Materials Used Per Year. ...................................................................................71 Table 4.2: Materials Flow Required for the Extraction Process in Lb. .........................................................73 Table 4.3: Total Outputs for All Materials of the Extraction Process. .........................................................74 Table 4.4: Energy Consumed in the Production of the Extraction of Copper, Steel, and Aluminum. .........74 Table 4.5: Air Emissions Associated with Energy Use Required for Extracting Copper...........................75 Table 4.6: Air Emissions Associated with Energy Use Required for Extracting Aluminum. .......................75 Table 4.7: Air Emissions Associated with Energy Use Required for Extracting Steel. ..............................75 Table 4.8: Energy Related Air Emissions for Extracting Materials Used in Producing 100,200 Air Conditioner Units.................................................................................................................................76 Table 4.9: The Total Environmental Impact of the Primary Mining Process Scenario.................................77 Table 4.10: Materials That Are Sent for Secondary Mining Process. ...........................................................78 Table 4.11: Reduction Factors for Copper, Steel and Aluminum..................................................................79 Table 4.12: Secondary Mining Process Results. ...........................................................................................79 Table 4.13: Energy Consumed in the Production of Secondary Copper, Steel, and Aluminum ...................80 Table 4.14: Energy Emissions for Mining Secondary Copper. .....................................................................80 Table 4.15: Energy Emissions for Mining Secondary Aluminum.................................................................80 Table 4.16: Energy Emissions for Mining Secondary Steel..........................................................................81 Table 4.17: Utility Related Air Emissions for Secondary Mining Materials Used in the Production of 100,200 Air Conditioners. ...................................................................................................................81 Table 4.18: The Environmental Impact of Secondary Mining Materials Process. ........................................82 Table 4.19: The Amount of Extracted Raw Materials Needed......................................................................82 Table 4.20: The Environmental Impact of the Extracted Materials for the Secondary Mining Materials Scenario. ..............................................................................................................................................83 Table 4.21: The Utility Related Air Emissions Resulting from Energy Consumption for Materials Extraction Process within the Secondary Mining Scenario. ................................................................83 Table 4.22: The Total Environmental Impact for Extracting Materials for the Secondary Mining Materials Scenario. ..............................................................................................................................................84 Table 4.23: The Total Environmental Impact the Secondary Mining Materials Scenario. ...........................85 Table 4.24: Estimation of Disassembly Times for Air Conditioner. .............................................................88 Table 4.25: Utility Related Air Emissions for Disassembly One Air Conditioner........................................89 Table 4.26: Total Utility Related Air Emissions for Disassembly by Using Power Tools............................90 x Table 4.27: Utility Related Air Emissions for Lighting during the Disassembly of One Air Conditioner Manually..............................................................................................................................................91 Table 4.28: Utility Related Air Emissions for Lighting during the Disassembly of 100,116 Air Conditioner Units Manually. ...................................................................................................................................92 Table 4.29: Utility Related Air Emissions for Lighting during the Disassembly of One Air Conditioner Unit Using Power Tools...............................................................................................................................92 Table 4.30: Utility Related Air Emissions for Lighting During the Disassembly of 100,116 Air Conditioner Units Using Power Tools. ....................................................................................................................93 Table 4.31: Total Air Emissions for Manual Disassembly of 100,116 Air Conditioner Units. ....................93 Table 4.32: Total Air Emissions for Disassembly Using Power Tools of 100,116 Air Conditioner Units. ..94 Table 4.33: The Environmental Impact of Secondary Mining Materials Process of the NonRemanufacturable Products. ................................................................................................................97 Table 4.34: Environmental Impact of Extracting Materials to Be Able to Produce 100,200 Units...............98 Table 4.35: Total Enviornmnetal Impact of the Demanufacuring Scneraio Manually..................................98 Table 4.36: Total Enviornmnetal Impact of the Demanufacuring Scneraio Using Power Tools. .................99 Table 4.37: The Direct Internal Cost in U.S. Dollars. .................................................................................102 Table 4.38: External Environmental Costs in U.S. Dollars. ........................................................................103 Table 4.39: Total Economic Costs in U.S. Dollars......................................................................................103 Table A.1 : Data Gathered for Energy Consumption and its Emissions. ....................................................134 xi LIST OF FIGURES Fig. 1.1: Dimensions of Sustainable Development. ........................................................................................9 Fig. 1.2: A Linear Material Flows in Type I Industrial Ecosystem ...............................................................16 Fig. 1.3: A Quasi-Cyclic Materials Flows in Type II Industrial Ecosystem .................................................16 Fig. 1.4: A Cyclic Materials Flows in Type III Industrial Ecosystem . .........................................................17 Fig. 1.5: Typical Company of the 21st Century . ..........................................................................................19 Fig. 2.1: The Life Cycle of a Product ...........................................................................................................22 Fig. 2.2: Product Types According of the Intelligent Product System . .......................................................23 Fig. 3.1: Weight% of Materials Used in AC Unit. ........................................................................................35 Fig. 3.2: Primary Mining Scenario………………………………………………………………………….37 Fig. 3.3: Aluminum Extraction Flow Diagram……………………………………………………………..43 Fig. 3.4: Copper Extraction Flow Diagram ……………………………………………….………………..44 Fig. 3.5: Steel Extraction Flow Diagram …………………………………………………..……………….45 Fig. 3.6: The Normalized Outputs for Aluminum Extracted Flow Diagram……………..…………………46 Fig. 3.7: The Normalized Outputs for Copper Extracted Flow Diagram…………………………………...47 Fig. 3.8: The Normalized Outputs for Steel Extracted Flow Diagram……………………………………...48 Fig. 3.9: Secondary Mining Scenario……………………………………………………….………………50 Fig. 3.10: The Demanufacturing Process Scenario……………………………… ………….……………55 Fig. 4.1: A Flow Diagram of the Returned Air Conditioner Units. ...............................................................96 Fig. 5.1: The Amount of CO2 in the Three Scenarios. ................................................................................107 Fig. 5.2: The Amount of SO2 in the Three scenarios...................................................................................109 Fig. 5.3: The Amount of NOx in the Three scenarios. ................................................................................110 Fig. 5.4: The Economy as a Subsystem of the Ecosystem. .........................................................................112 Fig. 5.5: Comparison among the Amount of Raw Materials Used..............................................................114 Fig. 5.6: Comparison among the Amount of Energy Used. ........................................................................114 Fig. 5.7: The Economic Cost Per One Unit.................................................................................................115 Fig. 5.8: The Amount of Landfills in the Three Scenarios. .........................................................................117 Fig. A.1: Relation of CO2 Emissions and Energy Consumption. ................................................................135 Fig. A.2: Relation of NOx Emissions and Energy Consumption.................................................................135 Fig. A.3: Relation of SOx Emissions and Energy Consumption..................................................................135 xii CHAPTER 1 INTRODUCTION 1.1. Background Since the turn of the twentieth century, technology has been continuously revised because of the industrial revolution. The result has been a take-make-waste system that has taken on a life of its own with no regard to the laws of Mother Nature. This system assumes infinite sources of raw material inputs and sinks for the industrial wastes [ McDonough 1998]. During this period, it was not important to be concerned about the impact of industry on the environment since natural resources were thought of as inexhaustible, and nature was viewed as something to be tamed and civilized. However, the exponential growth in population, which reached six billion at the end of last year and is expected to be in excess of ten billion by the year 2030, with its associated increase in demand for consumer goods, drives the expanded use of national resources as raw material and extensive growth in energy consumption. This resulted in a negative impact on our common global environment. 1 Furthermore, we have begun to exceed the carrying capacity of the planet1, and continued growth will eventually destroy our host, the earth [Hawken 1993]. Taking these considerations in regard, some leading industrialists realized that conventional ways of doing things might not be sustainable2 for the generations to come. "What we thought was boundless has limits,” said Robert Shapiro, the chairman and chief executive officer of Monsanto, said in a 1997 interview, “and we are beginning to hit them." [ McDonough 1998]. Lester Throw [Anderson 1999]. is of the opinion that we are already in the third industrial revolution. He believes the first was steam powered; the second was electricity powered; making possible the third, which is the current information revolution, leading in the information age. However, Ray Anderson [Anderson 1999]. holds that they all share some fundamental characteristics that lump them together with an overarching common theme. They were and remain in an unsustainable phase in civilization’s development. Recently, Paul Hawken and Bill McDonough have called for the next industrial revolution. Anderson as well has called for the next truly revolutionary industrial revolution - but this time, he said, to get it right - we must be certain it attains sustainability. 1 Hawken defined the carrying capacity of the planet as the maximum level of a species or population that can be steadily and consistently supported by the resources of the planet 2 See section 1.2 2 1.2. Concept of Sustainability The concept of sustainability has been proposed in several publications. In his interesting book, The Ecology of Commerce, the author and entrepreneur Paul Hawken [ 1993, pg. 139]. described sustainability as “an economic state where the demands placed upon the environment by people and commerce can be met without reducing the capacity of the environment to provide for future generations. It can be also expressed in the simple terms of an economic golden rule for the restorative economy: Leave the world better than you found it, take no more than you need, try not to harm life or the environment, make amends if you do”. Thus, sustainability encompasses the principle of taking from the earth only what it can provide indefinitely thus leaving future generations no less than we have access to ourselves. Sustainability was also defined anthropocentrically as meeting the needs of all humans, being able to do so on a finite planet for generations to come while ensuring some degree of openness and flexibility to adapt to changing circumstances. It is interesting to note that all the definitions of sustainability researched share two common goals: · A goal of conserving irreplaceable resources. · A goal of environmental maintenance. It should be emphasized that the concept of sustainability is not a new concept. It originated in Germany during the late 18th and 19th centuries. At that time, forests upon which Germany was dependent for wood to support its growing economy were declining while the population and economy continued to grow. They started to search for a solution for the national forest resource depletion and its consequences. This resulted in a 3 rise of the sustainability concept that was viewed as a mechanism to ensure prosperity through ongoing economic growth. This concept was defined as sustained yield. In the later part of the 19th century, Gifford Pinchot, an American pioneer introduced the concept of sustained yield in the U.S. Pinchot thought that the U.S. should take an active role in managing the nation’s natural resources in order to secure a sustainable future and make economic expansion indefinite [Zovanyi 1998]. It can be speculated that the driving forces behind a move toward sustainability are: · Increasing global population · Man's environmental impact on the global commons, and · Natural resources depletion In June 1992, the United Nations Conference on Environment and Development (UNCED), popularly known as the Earth Summit, took place in Rio de Janeiro, Brazil. It was the largest UN conference ever held. Approximately 30,000 people from around the world, including more than a hundred world leaders and representatives of 167 countries, gathered in Rio de Janeiro to respond to troubling symptoms of environmental decline. Although it was difficult to get agreement among the participating countries on issues where deeply held values or economic interests were at stake, everyone anticipated that this would happen. So, many industrial participants touted a particular strategy: sustainable development. 4 1.3. Concept of Sustainable Development In 1972, the concept of sustainable development burst into visibility with the publication of Donella Meadows’ book, The Limits to Growth, and with the United Nations' Conference on Human Environment in Sweden, which coined the term "sustainable development". Since then, it has received growing attention through deliberate discussion and support via ongoing global conferences. Sustainable development, like the term sustainability, has many definitions. But first, it should be explicated as to why it is called sustainable development and not sustainable growth. Growth is a quantitative increase in the physical scale. However, development is a qualitative improvement to a greater or better state. We live on a planet with limited resources that will never grow because the earth has physical limits. However, it develops endlessly so as to improve the quality of life may achieve sustainability and create a better world via sustainable development rather than growth. Sustainable development has been defined according to the work produced by the World Commission on Environment and Development in 1987 under the title Our Common Future as, “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” [WCED 1987]. In other words, sustainable development is used for improvement that satisfies today’s needs without compromising the needs of future generations. This definition establishes that the concept of intergenerational equity is the backbone of sustainability, which means leaving an equitable share of natural resources for future generations. With sustainable development, environmental issues and concerns cannot be considered in 5 isolation - separate from economic and social development. This new sustainable development demands the integration of ecological, social, and economic interests. According to the World Business Council on Sustainable Development, "sustainable development involves the simultaneous pursuit of economic prosperity, environmental quality, and social equity. Companies aiming for sustainability need to perform not against a single, financial bottom line, but against the triple bottom line3 "Over time, human and social values change. Concepts that once seemed extraordinary (e.g. emancipating slaves, enfranchising women) are now taken for granted. New concepts (e.g. responsible consumerism, environmental justice, intra- and intergenerational equity) are now coming up the curve” [WBCSB 2000]. The International Institute for Sustainable Development, in conjunction with Deloitte and Touche, developed the following description of sustainable development for business strategy. For the business enterprise, sustainable development means adopting business strategies and activities that meet the needs of the enterprise and its stakeholders today while protecting, sustaining, and enhancing the human and natural resources that will be needed in the future. This definition falls far short of the concept of "full sustainability" or the rigorous definition of sustainable development. The conflict of stakeholder needs versus resource protection opens the door to ambiguity and interpretation. This definition also falls short by failing to provide for 3 See chapter 5 for more information. 6 measurability. Despite weakness of this definition, the existing business climate (including political and economic infrastructures and technology) does not provide a suitable environment for pursuing rigorous sustainability. The Deloitte and Touche definition is arguably the most practical definition for the short-term future. As sustainability becomes an increasingly visible issue it seems likely that corporations will find themselves facing more rigorous definitions [IISD 2000]. Herman Daly [1996]. defined sustainable development in his book Beyond Growth as “development without growth – without growth in throughput beyond environmental regenerative and a absorptive capacity. Throughput is the flow of materials and energy through the human economy. It includes everything we make and do. Throughput is calculated as the total number of people multiplied by their consumption”. In other words, the regenerative and absorptive capacity of the environment is its ability to produce raw materials for our use and to provide us a sink for discarding our wastes. To be sustainable, our throughput should not exceed the capacity of the environment; otherwise, negative consequences will be produced. So far, there is no definition for sustainable development that satisfies everyone, and perhaps there will never be such a thing. But, a practical understanding of sustainable development is easily achieved if we are going to bear in our minds the following concepts: · It is a direction rather than a “carved in stone” list of specific definitions. · It is about creating a better world through balancing environmental, social, and economic factors. 7 Accordingly, sustainable development can be symbolized as the search for an economy that can exists in an equilibrium with the earth’s limited resources and its natural ecosystems. Furthermore, sustainable development can bring the environmental quality together with economic growth into harmony rather than conflict. It is a concept that recognizes that both economic activities and environmental considerations should always be integrated for humanity’s long-term well being [Richards, et. al. 1994]. As a summary, sustainable development involves the simultaneous pursuit of economic prosperity, environmental quality, and social equity. It improves the economy without undermining the social and environmental forces upon which it depends. It focuses on improving our lives without continuously increasing the amount of energy or raw materials consumed in a manner that is faster than the natural systems can regenerate. Furthermore, it requires managing our lives in a way that ensures that both economy and society can continue to exist without destroying the natural environment upon which our lives depend. Companies aiming for sustainable development need to perform not just in accordance with the economic aspect, but in accordance with all three aspects [Vanegas 1997]. This is illustrated in Fig. 1.1 , which demonstrates that these dimensions inextricably linked. 8 focus on maximizing income while maintaining the stock of capital assets (human, natural and manufacturing capital) Economic issues of intra-generational equity issues of valuation in a global context Technology as a means to achieve economic, social and environmental goals Social focus on stability of social and cultural systems issues of inter-generational equity Environmental focus on stability of biological and physical systems Fig. 1.1: Dimensions of Sustainable Development [Vanegas 1997].4 1.4. Industrial Ecology Industrial ecology, the science of sustainability, is still a young and evolving concept that offers a unique system’s approach to the industrial design of products and processes, and the implementation of sustainable manufacturing strategies. It emerged following the National Academy of Sciences meeting in 1991 [Chertow 1998]. Graedel and Allenby defined industrial ecology as “the means by which humanity can deliberately and rationally approach and maintain a desirable carrying capacity, given continued economic, cultural, and technological evolution. The concept requires that an industrial system be viewed not in isolation from its surrounding systems, but in concert with them. It is a system’s view in which one seeks to optimize the total materials cycle 4 As cited in [Odom 2000]. 9 from virgin material, to finished material, to component, to product, to obsolete product, and finally to ultimate disposal” [Graedel and Allenby 1995]. 1.4.1 Emulating Mother Nature The principle of industrial ecology was acknowledged 500 years ago by Leonardo da Vinci when he said: “Although human genius through various inventions, makes instruments corresponding the same ends, it will never discover an invention more beautiful, nor more ready, nor more economical than does nature, because in her inventions nothing is lacking and nothing is superfluous” [Young, et. al. 1997]. Therefore, industrial ecology is about the incorporation of natural systems into our industrial infrastructures and learning from the efficiency of natural systems. It takes the model of the natural environment as a way for solving environmental problems, creating a new paradigm for the industrial system in the process. The idea of an industrial ecology is based upon a straightforward analogy with natural ecological systems. In nature an ecological system operates through a web of connections in which organisms live and consume each other and each other’s waste. The system has evolved so that the characteristic of communities of living organisms seems to be that nothing that contains available energy or useful material will be lost. There will evolve some organism that will manage to make its living by dealing with any waste product that provides available energy or usable material. Ecologists talk of a food web: an interconnection of uses of both 10 organisms and their wastes. In the industrial context, we may think of this as being use of products and waste products. The system structure of a natural ecology and the structure of an industrial system, or an economic system, are extremely similar [Frosch 1992]. In nature, all materials are reused and nothing is endlessly discarded. Nature has acquired this approach because extracting these materials from reserves is costly in terms of resources and energy, and this is always avoided whenever possible. On the other hand, our industrial system discards materials to the ecosystem at unnecessary high cost. As a result, products should be thought of as residues rather than wastes, and it should be considered that wastes are basically residues that our economy has yet to use efficiently. Characteristic features of Mother Nature that could be emulated by industry includes [Tibbs 1991]: 1. In natural ecosystems there is no such thing as "waste"; considering something that cannot be absorbed in the system. 2. Waste from one species is the food for another. 3. Concentrated toxins are not stored or transported in bulk at the system level, but are synthesized and used as needed only by the individuals of a species. (Snake venom is produced in glands immediately behind the snake’s teeth.) 4. Materials and energy are constantly circulating and transforming within Mother Nature. 5. Mother Nature runs entirely on solar energy. 6. Mother Nature is dynamic and information-driven, and the identity of each of its species is defined in process terms. 11 7. Mother Nature allows independent activity of species individuals. However, cooperation and competition interlink them and hold them in balance. In conclusion, the aim of industrial ecology is to incorporate the cyclical patterns of ecosystems into designs for industrial production processes, in order to achieve a pattern of industrialization that is not only more efficient, but adjusted to the characteristic features of Mother Nature. An industrial system of this type will have no adverse environmental effects, because it will have eliminated potential causes in the design stage. 1.5. Industrial Metabolism Metabolism, as used in its original biological definition, can be described as the process in which the organism ingests energy rich materials (food) to support its maintenance and functions, as well as a surplus to permit its own growth and reproduction. It also involves excretion of the generated waste consisting of degraded materials. With this information in mind, industrial metabolism can be defined as a complete integrated collection of physical processes that convert raw materials, energy, and labor into finished products as well as wastes in a steady state condition. The stabilizing controls of the system are provided by its human component. It is worth noting that this concept can also be applied to other self-organizing entities, such as manufacturing firms. A manufacturing firm is the economic synonym of a living organism. However, some differences prevail between a living organism and a firm. For example, biological organisms reproduce themselves. On the contrary, firms 12 produce products or services. Furthermore, the firms are not specialized and can easily change from one product or business to another depending on the market demands. By contrast, organisms are highly specialized and cannot change their behavior except over a long period of time. The life cycle of individual materials in the living organism are closed, whereas, most industrial cycles are open. In other words, the industrial system doesn’t generally recycle its wastes. However, it starts with high quality materials extracted from the earth, and returns them to the nature in degraded forms [Ayres and Ayres 1998]. The ultimate goal in industrial metabolism is to achieve advances across the horizon of industrial processes, bringing them more into line with the metabolic patterns used in the natural ecosystem. As a result of this, management of the interface between industry and the biosphere would become easier and the in-process energy demands would be reduced, process would be safer, and the industrial metabolites would be more compatible with natural ecosystems. This is the absolute longer-term objective, however, at this point and in the form of modest rationale process improvement, industrial metabolism has much to offer, as a result it is always considered as an important component of industrial ecology [Tibbs 1991]. Frosch and Gallopoulos have discussed the relationship between biological ecology and that of industrial activities: In a biological ecosystem, some of the organisms use sunlight, water, and minerals to grow, while others consume the first. Alive or dead, along with minerals and gases, and produce wastes of their own. These wastes are in turn food for other organisms, some of which may convert the wastes into the minerals used by the primary producers, and some of 13 which consume each other in a complex network of processes in which everything produced is used by some organism for its own metabolism. Similarly, in the industrial ecosystem, each process and network of processes must be viewed as a dependent and interrelated part of a larger whole. The analogy between the industrial ecosystem concept and the biological ecosystem is not perfect, but much could be gained if the industrial system were to mimic the best features of the biological analogue [Frosch 1992]. The approaches that can be used to achieve these goals are: 1. Optimizing the use of materials and embedded energy, waste reduction, reevaluation of wastes as raw material for other processes, and consideration of wastes as products so as to close the manufacturing loop. 2. Understanding the ecosystem assimilative capacity and development of indicators to quantify the environmental impact of industrial processes so as to balance the industrial input and output in relation to natural ecosystem capacity. 3. Creating metabolic pathways in industrial processes. 4. Introducing systemic schemes of energy use. 5. Opening of long-term viewpoints in analysis of industrial system development. It can be speculated that new processes (organisms) were created by the biological evolution to stabilize the inherently unstable situations and close the open cycles. This degree of stability that the biosphere reached took several billion years. However, in the case of industrial system, the time scales have been significantly shortened. Furthermore, 14 the rate of resources mobilization by human industrial activity is in most cases comparable to that of the natural rate. This is reason for concern about long term stability. [Ayres and Ayres 1998]. The aim of the industrial metabolism is to understand the circulation of materials and energy in industrial systems from their initial extraction to their inevitable reintegration into the overall biogeochemical cycles. In addition, to develop an ecosystem in which the consumption of energy and materials is optimized, waste generation is minimized, and the effluents of one process serve as raw materials for another process. Ultimately, The industrial ecosystem should end up working as a biological system [Hileman 1998]. From the above discussion, it can be seen that industrial ecology is an expansion of industrial metabolism. The industrial metabolism aims to look at the total pattern of energy/material flows from initial extraction of resources to final disposal of wastes. However, industrial ecology looks for determining how the industrial system can be restructured to make it compatible with the way Mother Nature functions. 1.5.1 Types of Industrial Ecosystems It is instructive to consider first the current state of existing industrial ecosystems, to be able to start thinking about environmentally preferable industrial systems. The evolution of industrial ecosystem is recognized in three possible stages: Type I: In this stage, the industrial ecosystem might be described as linear, one-way flows of products where the life cycle of the product occurs with no regard for reuse or 15 recovery of materials or components, and independent of all other flows. Schematically, it takes the form of Fig. 1.2. Unlimited ECOSYSTEM Unlimited Resource COMPONENET Waste Fig. 1.2: A Linear Material Flows in Type I Industrial Ecosystem [Graedel and Allenby 1995]. Type II: In this stage, the industrial ecosystem interlinking between products and related materials occurs. Although there is still an input of virgin materials and a disposal of wastes outside the system, the flows of material within the system are larger, but the flows into and out of it are smaller. Schematically, it takes the form of Fig. 1.3. The Type II industrial ecosystem is more efficient than Type I, but still it is not sustainable because it continues to have an input (virgin materials) and an output (wastes); moving linearly in one direction. ECOSYSTEM Component Energy and limited Resources ECOSYSTEM Component ECOSYSTEM Component Unlimited Waste Fig. 1.3: A Quasi-Cyclic Materials Flows in Type II Industrial Ecosystem [Graedel and Allenby 1995]. Hypothetical Type III: In this arrangement, the industrial ecosystem follows the principle “waste from one component is the food for another”. It mimics the biological ecosystem, 16 and is characterized by complete cycling of products and related materials. The energy is an exception to the cyclicity since it enters as an external resource in the form of solar radiation. Schematically, it takes the form of Fig. 1.4 [Graedel and Allenby 1995]. ECOSYSTEM ENERGY ECOSYSTEM ECOSYSTEM Fig. 1.4: A Cyclic Materials Flows in Type III Industrial Ecosystem [Graedel and Allenby 1995]. 1.6. Industrial System Models of the 21st Century Many of the current industrial systems of today operate in a linear fashion; characterized by unsustainable usage of resources and accumulation of wastes. This system model has limited resource availability and waste disposal capacity. The takeback model5 is closed; i.e. what goes out eventually returns to the process. Consumption when it proceeds linearly (Type I) requires an infinite supply of resources, which the earth cannot provide on our time scale of extraction and use. Mother Nature operates successfully in a cyclical manner (Type III). Therefore, we must strive to move in harmony with it, by likewise operating in a cyclical manner, rather than linearly. 5 Discussed in Chapter 2. 17 Hawken puts it elegantly: "Any ecological model of commerce must not only mimic nature in recognizing that waste equals food, running off of current solar income, and protecting diversity, but it must also have firmly and clearly in place feedback that allows it to recalibrate constantly and quickly adjust its costs, supply, and demand. Instead of following the cyclical paradigm, most of our resource businesses today are linear systems that by their nature receive and give out the wrong information to themselves and the greater environment." [Hawken 1993]. Instead of continuously searching for virgin resources and then disposing of process excesses when they become waste, we need to design our industrial systems so that as little waste as possible is provided to begin with, i.e. it will focus on service and value of the product instead of material throughput. And engaging external organizations to encourage sustainable practices. Fig. 1.5 summarizes all the above as a schematic diagram [Anderson 1998]. 1.7. The Product Take-Back System The product takeback system is a concept shifting from industrial economy towards a service economy. It is a system that is based on the assumption that consumers will only lease the product from the producer, who basically provides them with the product on a service basis. After the product has served its function and has to be renewed, the consumer returns it to the producer who is responsible for disassembly and recycling. 18 Fig. 1.5: Typical Company of the 21st Century [Anderson 1998]. The three dimensions of sustainability; environmental, economic, and social are considered in this system6. By closing the cycle, economically, it saves material, energy, and disposal costs. Environmentally, it saves natural resources, reduces energy consumption and minimizes pollution. And socially, it provides employment, and enhances producer-consumer relationship. The product takeback system is a typical Type III industrial ecosystem that operates successfully in a cyclical manner. Mimicking Mother Nature by recognizing that “waste equals food”, and what goes “out” must finally come “in”. More details about this system will be covered in the next chapter. 6 Discussed in Chapter 5. 19 1.8. The Focus of this Thesis This thesis provides a decision support comparison of the demanufacturing process for an industry pursuing sustainability via the product take-back model. This model views each product as a service provided to the consumer and aims to transform industry from a Type I industrial ecosystem into a Type III (cyclical one)in an attempt to mimic Mother Nature by recognizing that “waste equals food”, and what goes “out” must finally come “in”. Three comparative scenarios are investigated for the Heating Ventilation and Air Conditioning (HVAC) industry. The scenarios are either already existing or theoretically proposed. The first is the current manufacturing process, using extracted raw materials (primary mining), the second is secondary mining (product shredding), and the third is the demanufacturing process (product disassembly). The environmental, economic, and social dimensions of sustainability are studied using manufacturer or hypothetical data, or information collected from literature. This work was carried out in conjunction with a local HVAC manufacturer, thus all the generated data and conducted analysis is contributed from their manufacturing processes. At the end, the most sustainable process that fulfills the requirements of industrial ecology is identified. 20 CHAPTER 2 THE PRODUCT TAKE-BACK MODEL 2.1. Background The product take-back model is a new strategy that is being adopted by industry attempting to move toward sustainable development. It is a product-oriented approach to environmental protection that promotes and sells the functionality of products rather than the products themselves. It also encourages the reuse of the products rather than their recycling. In other words, the value of the products is more closely attributed to their performance and real use [Richards, et. al. 1994]. The concept of this approach is to close the loop of materials and component usage by reusing them in new product manufacturing. As illustrated in Fig. 2.1, in this system the life cycle of a product is changing from a linear cycle (Type I) into a cyclic one (Type III). In Type I, the first stage is designing the product according to customer’s needs; in this linear life cycle raw materials go through processing and manufacturing into products that will be used by the customers. At the end of the life cycle, the product reaches the retirement phase, which is the final stage of the linear life cycle. On the contrary, in the cyclic life cycle, the environmental factors (materials recyclability, reusability, and energy needed for assembly or ease of disassembly) are integrated in the early design of the product and the raw materials used in the product manufacturing 21 should be amply abundant and non-toxic materials. At the end of the product life cycle, the original manufacturer utilizes the old product by reusing or tearing the product down into its individual components. When the product is disassembled, then the parts are cleaned and placed back into inventory. Fig. 2.1: The Life Cycle of a Product [NCR 1999]. 2.2. Development of a Product Take-Back System The Product take-back system is based on the proposal that the manufacturer is responsible for what happens to its product at the end of the product useful life cycle. In this situation, the consumer would lease the product from the manufacturer who basically sells the service of the product. When the product has to be renewed, the consumer does “de-shopping” by returning the product to the manufacturer who is responsible for demanufacturing, reconditioning, and reusing of the product. Michael Braungart and Justus Engelfried [Braungart and Engelfried 1992]. introduced the Intelligent Product System, which comprises the basic idea for the product take-back system, as a solution of 22 the waste problem handling resources and energy in a “life-cycle” economy instead of a “one-way, no deposit, no return” economy. The system divides products into three types as shown in Fig. 2.2: · Consumption Products Products that are purchased to be consumed and suitable for only one use (i.e. food) upon which these products become waste. In such a system, these products have to be biodegradable and non-toxic. · Service Products Products that are used for their function, i.e., washing machines or any white goods. Under this system these products should only be leased from the producer who provides the product on a service basis. In the retirement stage of the product the consumer returns it to the manufacturer for remanufacturing. · Unmarketable products Products that cannot be used in an environmentally sound manner, these products should be avoided fully and replaced by biodegradable and non-toxic products. Fig. 2.2: Product Types According of the Intelligent Product System [Braungart and Engelfried 1992]. 23 As a result, according to the “intelligent product system” consumption and service products can substitute all current types of waste. The product take-back system, which aims at transforming industry into a restorative cooperation by providing food for the process, is considered as an outgrowth of extended producer responsibility (EPR). EPR was introduced early in this decade by Thomas Lindhqvist, a Swedish professor of environmental economics, who defined EPR as: “Extended producer responsibility is an environmental protection principle to reach an environmental objective of a decreased total environmental impact from a product, by making the manufacturer of the product responsible for the entire life-cycle of the product and especially for the take-back, recycling and final disposal of the product. The extended producer responsibility is implemented through administrative, economic and informative instruments. The composition of these instruments determines the precise form of the extended producer responsibility” [Lindhqvist 1993]. The concept of EPR has also evolved in the U.S. In 1996, the President's Council on Sustainable Development (PCSD) defined EPR “extended product responsibility” as the shared responsibility of government, consumers, and all industry actors in the product chain for all the environmental impacts of a product over its life cycle [Fishbein 1998]. It can be speculated that the main attribute of the product take-back system in the U.S. is that there is no emphasis on the producer's unique responsibilities or on the post- 24 consumer stage, rather it is a shared responsibility to decrease the life cycle environmental impacts of the product between of producer, consumer and government. These responsibilities are: Producer’s Responsibility · To design environmentally friendly products that directly involve: - Including materials that are readily recyclable. - Avoiding using different and a variety of materials. - Minimizing the use of non-renewable resources. - Eliminating and or reducing hazardous materials use. · To design products for reusability and remanufacturability by: - Increasing product modularity to reduce variability of parts. - Reducing the amount of products and materials to be landfilled by including durable products and materials. - Avoiding deleterious material combinations. - Protecting parts against soil and corrosion. · To design the product for ease of disassembly and reassembly. · To sell the functionality of the product rather than the product itself. · To take-back the product at the end of its life cycle. Consumer’s Responsibility · To buy Ecoproducts. · To Support product take-back systems. 25 Government’s Responsibility · To buy products with benign environmental impacts. · To reduce obstacles to recovery of take-back products. It should be emphasized that the EPR in the U.S. is not mandatory but it is a recommended policy by PCSD to "achieve national environmental, economic and social goals” [EPA 2000]. 2.3. Drivers for Applying a Product Take-Back System There are many drivers behind the application of product take-back system. This system reduces virgin materials extraction by transforming the used materials that are regarded as waste into valuable products. In addition, it minimizes the cost of the purchased parts and components by realizing a savings in raw material and spares parts costs when reusing components from end of life cycle products. This will be associated with a reduction in the energy use and its associated environmental impacts (i.e. by recovering embedded energy from reused parts). It should also be emphasized that the waste issue is becoming a priority in environmental policies in Europe and other countries, since available landfill space is shrinking thereby increasing disposal fees. Therefore the product take-back model is one of the most important solutions for this problem. Moreover, with the global concern about environment, companies may take a competitive advantage by applying a product take-back system. Remanufactured products may be introduced to the market as Ecoproducts. This type of label is appealing to the consumer. In purchasing these products, people are fulfilling a desire to do something 26 good for the environment. Furthermore, remanufactured products are cheaper and have the same guarantees against failure as new ones, which make for a good marketing argument for selling, especially to customers with budget limitations. Likewise, this system fosters customer loyalty (i.e. in returning an end of life product to the original manufacturer, the customer can be encouraged to purchase again). Finally, in some countries, legislation exist that has made product take-back system obligatory for the companies to apply it [Lindhqvist 1993]. 2.4. Implementing Product Take-Back System in the U.S. Although EPR in the U.S. is not obligatory, a number of corporations have started implementing their own product take-back systems. The industry examples in the following sections are but a few examples of the product take-back system are in existence: 2.4.1 The Battery Industry The battery industry started a product take-back system because of the inconsistent legislation of producer responsibility for nickel-cadmium rechargeable batteries. In 1995, they established the Rechargeable Battery Recycling Corporation (RBRC) to collect and recycle the batteries. Their goal is to recycle 70 percent of disposed batteries by 2001. By 1997, they reached 22 percent from 2 percent in 1993 [Fishbein, 1998]. 27 2.4.2 Xerox Xerox, a leading company in manufacturing photocopiers, used to “takeback” its products for use as service parts. However, after refurbishing the parts, they used to sell them to contractors who would recondition the old equipment. Gradually, Xerox found itself in competition with those contractors but customers continued to blame Xerox for quality problems [Ayres, Ferre et al. 1997] . To handle the “takeback” machines returning to Xerox and to standardize its take-back and remanufacturing operations, Xerox established its Asset Recycle Management (ARM) Program in 1991 [Davis 1996]. This program saved raw materials and gained Xerox a competitive edge over other manufacturers. In addition, this program has cut about $200 million in raw material and parts savings by taking back 70% of its equipment once disposed of at landfills. As for landfills, it dropped from 2500 tons in 1992 to 1000 tons by the second quarter of 1995 with annual savings of $200,000 in disposal costs by applying ARM. Total savings in 1996 amounted to about $65 million. Furthermore, the huge amount of raw materials savings interprets lowering the metal ores, coal, petroleum and other materials that would be extracted to produce them [Ayres, Ferre et al. 1997] . 2.4.3 Interface Interface, a global carpet company, has created what they refer to as theEvergreen Lease program - the leasing of carpet, rather than selling it. The customer pays monthly for the service of the carpet, not the carpet itself. Interface seeks to be the first sustainable corporation, following that, the first restorative company. In 1994, they put into practice the Quality Utilizing Employee Suggestions and Teamwork (QUEST). Then, Interface 28 Research managed a program called EcoSense, to measure their progress. They joined the two programs (QUEST and EcoSense) together so as to be able to achieve their goal. Interface emulated Mother Nature by redesigning its processes and products into cyclical material flow. They reduced the use of raw materials from the earth and tried to get best use of the materials they use. To do so, they used natural organic materials. Interface is already on the track to produce zero waste and scrap to the landfill [Interface 1997]. After three and a half years of applying their program, they reduced the waste by 40 percent, almost $67 million savings which they used in paying the costs of their new model. In addition, scrap to landfills has been reduced to 60 percent [Anderson 1999] . Being a typical company in the 21st century, Interface has taken the following steps to align itself with its sustainability goals [Anderson 1998]: 1 Zero waste. The first step is eliminating the waste, not reducing it. 2 Benign emissions. Through eliminating the emissions to Mother Nature that have toxic effects. 3 Use renewable resources. By reducing the energy needed in the processes and substituting non-renewable sources with renewable ones. 4 Close the loop. By mimicking the Mother Nature’s biological ecosystem; operating in a cyclic not a one-way system. 29 5 Resource efficient transportation. Investigating methods to reduce the transportation of products and people in favor of moving information. 6 Sensitivity hook-up. Creating a community that sees the operation of Mother Nature and our impact on it. 7 Redesign commerce. So that it will focus on service and value of the product instead of material, and engaging external organizations to encourage sustainable practices. Recall Fig. 1.5 summarizes all the above in a schematic preview. 2.4.4 Siemens and Nixdorf Siemens and Nixdorf are two companies that have an established take-back program to remarket old computers without any disassembly process. Since their merge in 1991, they started to think about closing the loop by reusing the old parts in service operations. They realized the potential that the recycling held for improving product design. By learning the design limitations during the process of disassembly, they could build newer computers that are better and more recyclable in the future. They established a centralized recycling facility in Paderborn, Germany that manages computer recycling and provides input for product designers. In 1995, they got back 5,400 tons of equipment, and 85% of this was either reused or recycled. The objective is to reduce the amount of landfill from 18% to 10% by year 2000. At this stage, the firm charges its customers when they return products. The fees are based on a sliding scale. In the future when the 30 electronic waste legislation is implemented in Germany the company is aware that they will be obligated to take-back its products free of charge. As a result, the company has started to institute a point-of-sale recycling fee on some of its products, thus increasing the total sales price of the item [Davis 1996] . 2.4.5 Rheem Disposal of used water heaters is difficult, in addition there is a $25 landfill charge. Rheem, a water heater manufacturing company instituted a National Water Heater Recycling Program. In this program, Rheem “takes-back” old products provided the contractor buys a new Rheem product. Rheem as an aside has set up a container for free disposal of any water heater made by any company. When the container is full, a scrap metal company retrieves the old water heaters and recycles them. They recycled 80,000 tons of steel, which is a huge saving in raw material use and in landfill space. In addition, this program, would solve disposal problem for plumbing contractors, create sales for Rheem since each must buy a new Rheem product after disposing an old one and helps improve environmental quality [Ferenc 1994] . 2.5. Summary Based on the previous discussion, most of the current applied take-back systems focus is on the economic profit by disassembling the returned products and reusing their parts for the purpose of service or marketing their products. Economic profit is only a part of the advantages that result from a product takeback system over other implemented systems. In the next chapter, a suggested 31 demanufacturing process model of product take-back system will be introduced. It emphasizes integrating the ecological, economic, and social dimensions of sustainability as an approach industrial sustainability attainment. 32 CHAPTER 3 DECISION SUPPORT MODEL FOR THE DEMANUFACTURING PROCESS 3.1. Introduction The product take-back system is a method that promotes the concept that the product provides a service for consumers. It is based on the premise that the manufacturer sells the functionality of products rather than the products themselves. Under this system, consumers will only lease the product from the producer who basically provides them with the product on a service basis. After the product has served its function and has to be renewed, the consumer returns it to the producer who is responsible for disassembling and reusing the product’s parts. As a result, the product, which is considered a “waste” under the current manufacture-consume-dispose industrial system, becomes actually "food" in the proposed product take-back system. As mentioned before, the aim of product take-back system is to approach industrial sustainability. It demands the integration of ecological, social, and economic interests. So the product take-back system will perform not just against a single economic aspect but against these three aspects. It can be speculated that the main objective of this system is to improve the economy without undermining the social and environmental aspects and decreasing the amount of energy and/or raw materials consumption. Taking 33 these findings into account, Interface is one of a handful of companies that applies the product take-back system seeking sustainability. However, it lacks the technology for reusing old fibers as raw material for making new carpet fiber [Anderson 1999] . In this chapter, the three comparative scenarios are investigated; these scenarios include the current manufacturing process, using extracted raw materials (primary mining), the secondary mining (product shredding), and the demanufacturing process (product disassembly). 3.1.1 Materials Analysis The product that was chosen for this thesis is a local HVAC manufacturer who manufactures air conditioners for home and light industry use. The evaluation of unit materials composition was determined in conjugation with the manufacturer’s engineering department. The main materials that are used in the manufacturing of an air conditioner unit are shown in Table 3.1 and depicted in Fig. 3.1. Material Wt / unit (lb.) Wt / unit% Copper 16.854 23.55 Steel 43.472 60.74 Aluminum 10.992 15.36 Rubber 0.248 0.35 Table 3.1: Materials Used in Air Conditioner Unit. 34 Aluminum 15.36% Rubber 0.35% Copper 23.55% Steel 60.74% Fig. 3.1: Weight% of Materials Used in AC Unit. Table 3.1 demonstrates that an air conditioner unit is manufactured from three main materials that include: Copper, Steel, and Aluminum. However, there is some rubber used but it amounts to less than one percent, which is considered as fluff that is sent to the landfill. 3.2. Primary Mining Process Scenario Primary material mining involves the extraction of non-renewable resources that are used in the production of finished goods. The extraction of primary natural resources requires processing large quantities of raw materials. This is believed to damage the environment without providing significant economic value. The primary theme of this section is to compare the suggested scenarios with the current manufacture-consumedispose system, and to understand the materials flow from extraction to disposal. This will help in managing the consumption of natural resources and finding alternatives that serve to account for the environmental and social concerns. 35 Under the current manufacture-consume-dispose system, as illustrated in Fig. 3.2, the product after production, is sold to the consumer for use. At the retirement life of the product, it is sent to the landfill or scrap yard, which is sent to the mining process and mined with the primary extracted materials, which are then sent to the manufacturer for manufacture and production. However, the analysis performed for this scenario is from the production output (products and wastes) until materials extraction, the transformation of materials into components is not considered, since it is beyond the scope of this research. As shown in Fig. 3.2, R is the total amount of raw material that is used to produce N products and wastes. In the following equation is the amount of raw material (P) used in the production of N products. Production P= n åR i ´t (1) i =1 Where, Ri is the total amount of raw material i used for production. t is the production efficiency. The waste material can be divided into two parts; production scrap SP n SP = åR i ´ m ´ (1 - t ) (2) i =1 Where, m is the secondary mining waste efficiency. 36 And production fluff generated, Fp. n Fp = å Ri ´ (1 - m ) ´ (1 - t ) (3) i =1 Consumer Use After consumer use, some units might be sent to scrap with the amount SC and others to the landfill FC. SC = q ´ N ´ X ¢ (4) Where, SC is the total amount of materials will be sent to scrap. Q is the percentage of units that will be sent to scrap. X ¢ is the weight of one unit excluding Rubber. And, ¢ F C = (1 - q ) ´ N ´ X (5¢) Where, FC¢ is the amount of units that is sent to the landfill. Scrap FC ² = q ´ N ´ R4 (5¢¢) Where, FC¢¢ is the amount of material from the returned units that is sent to the landfill. Disposal Equation (5) is the combination of Equations (5¢) and (5¢¢) as follows: 38 ¢ ² FC = FC + FC (5) Where, FC is the total amount of material that is sent to the landfill. As mentioned above, the scrap from production and consumer collection is sent for processing with the primary mining materials from which FR amount of materials is sent to the landfill is used in addition to the extracted raw materials (R) needed for the production of new products. 3.2.1 The Methodology for Analyzing Material Extraction In this part, the methodology for the analysis of outputs of extracted and processed virgin raw materials to be used in a product is evaluated. Materials extraction can be divided into four stages7: 1. Mining 2. Beneficiation 3. Smelting 4. Refining At each stage, extraction waste materials are left behind and a purified product is sent along to the next stage. There are two types of wastes in the Mining and Beneficiation stages: · Overburden, which is earth displaced in the process of searching for and removing ore. A point worth emphasizing here is that overburden yielded a total of 7 See [Ayres and Ayres 1998].]. for more information. 39 1313.5 MMT for metal ores in 1993. 1184.5 MMT contributed from non-ferrous metals and 129 MMT from iron ore [Ayres and Ayres 1998]. However, this overburden is not sent to the landfill, but is returned to the original excavation site. · Unwanted contaminants (gangue). The remaining material (concentrate) is then shipped to the next stage of processing into a downstream smelting or refining process, that generates further separation wastes such as, slags, air and water pollutants8. Copper, Steel, and Aluminum are the materials that are analyzed in depth in this research since they are the primary materials that are used in the air conditioner as shown previously. However, the methodology followed is applicable to any other material needed for other products. The Methodology: A. Data for the flow of extraction Copper, Steel and Aluminum extraction are gathered for year 1993, as shown in Figs. 3.3, 3.4, and 3.5 in that year 3.695, 1.791, and 88.8 MMT of Aluminum, Copper and Steel were produced, respectively [Ayres and Ayres 1998]. B. To get the contribution of each by-product output from the production of each material, normalization is used by dividing the whole inputs and outputs data by the amount of raw material produced9. The results are shown in Figs. 3.6, 3.7, and 3.8. Note that outputs are considered byproducts and waste, for example CO2. 8 Water pollutants were not considered in this research since focus was on solid waste and air emissions. 9 The focus in this research is on outputs. 40 C. From the above results, outputs of producing N units are calculated according the following equation: Yi j = C i j ´ N ´ X (6) Where, Yij: is the by-product output i of material j extraction. Ci j : is the normalizing factor of output i with respect to materials j extraction N: is the number of units produced. X: is the amount of material j used for producing one unit. D. All similar by-product outputs resulting from the mining of Copper, Steel and Aluminum are added together to evaluate the impact of producing N units by combining all used materials in producing such product. E. The amount of air releases resulting from the energy consumption for each mining process was determined. To evaluate these releases, some assumptions for energy source were made as shown in Table 3.2: Energy source Percentage Coal Oil Natural Gas Nuclear Large Hydroelectric Renewable 61% 1% 5% 28% 5% 0% Table 3.2: Energy Source Percentages10. 10 Based on South Carolina Energy Sources [EDF 2000]. 41 The three main air emissions resulting from energy are11: (7) CO2 = 3.72 ´ 10 -4 ´ E (8) NOX = 1.22 ´ 10 -6 ´ E (9) SO2 = 2.56 ´ 10 -6 ´ E Where, E : is energy consumed in kJ. (10) E = e´m Where, e: is energy consumed in kJ/Kg. m: is the mass of materials processed. F. The similar releases of materials extraction (e.g. CO2) and energy consumption releases (e.g. CO2) are added together. G. These results and some additional needed information are used in chapter 5 for analyzing the current manufacturing process with regard to the three dimensions of sustainability. 11 Calculations for obtaining these values are described in appendix A. 42 3.3. Secondary Mining Process Scenario Secondary Mining is a material recovery process because of its transformation of returned products into valuable resources. It manages solid waste, reduces pollution, and conserves energy. In this scenario, as illustrated in Fig. 3.9, the product after production, is leased to the consumer for use. At the retirement life of the product, it is returned to the manufacturer for shredding, sorting, processing, and reusing of materials to produce new products. However, this is a ‘downcycling’ process, i.e. after some number of uses it will not be good for reclaiming. Then extracted raw materials are needed for the production of new products. However, the analysis done for this scenario is from the production output (products and wastes) until materials secondary mining, the transformation of materials into components is not considered, since it is beyond the scope of this research. Production As shown in Fig. 3.9, N products are produced, which is leased to the consumers with P amount of materials used. n å P = W i ´ t (11) i=1 Where, Wi is raw material i used for production. t is production efficiency. The waste material from production is divided into two parts, production scrap SP n SP = åW i ´ m ´ (1 - t ) (12) i =1 49 Where, m is secondary mining waste efficiency. And fluff from production, Fp, generated is: Fp = n å W ´ (1 - m ) ´ (1 - t ) (13) i i =1 Consumer Use and Secondary Mining After consumer use, N products is returned for secondary mining, the total mined material is MR M R = (S P + P ) ´ l (14) Where, P is the amount of materials used in producing N products. l is the secondary mining efficiency. So, the total fluff, F, is F = FP + FR (15) Where, FR is the fluff that results from the secondary mining process. As for R, extracted Raw Materials are needed for production for two cases, either after N uses of the ‘downcycled’ material, or to account for ‘waste’ materials that are sent to the landfill. The methodology that is followed to find the pollutants of processing secondary materials is based on the assumption that secondary processing produces the same wastes as primary. During this methodology, the pollutants that are considered are the ones that result from the processes of the flow of primary mining process that are needed to 51 produce such secondary materials, e.g. Aluminum. To be secondary mined as shown in Fig. 3.6, it passes the smelting and refining process, so the pollutants assumed are the ones that result from this process (i.e. smelting). 3.3.1 The Methodology for Analyzing Secondary Mining Process 1. By considering the flow of primary mining process the processes that the materials pass through for secondary mining are assigned, for Copper and Aluminum, they enter the smelting and refining process. As For Steel, it is processed through smelting, refining and pickling (see Fig. 3.3, 3.4, 3.5). 2. For Steel, based on the report [ISRI 2000]. the reduction in air pollution is 86% and in mining wastes 97%. 3. As for Copper and Aluminum, a ratio method is followed to get the reductions in air pollution and mining wastes as shown in Equations (16) and (17). Thus, Copper, Steel, and Aluminum energy consumption factors are found between the current manufacturing process and the secondary mining, which are listed in Table 3.3. Material Energy Energy Reduction consumed consumed Copper 91 13 0.142857 Steel 31 9 0.290323 Aluminum 270 17 0.062963 Factor Table 3.3: The Reduction Factor of the Secondary Mining Process [Graedel 1995]. 52 · The emissions and mining wastes reduction factors are found based on the Equation (16) and (17). S Rj = S RS ´ E Rj E RS (16) Where, SRj is the solid waste reduction factor for material j. SRS is the Steel solid waste reduction factor. ERj is the energy consumption reduction factor for material j. ERS is the Steel energy consumption reduction factor. Em Rj (17) Em RS = ´ E Rj E RS Where, EmRj is the air emissions reduction factor for material j. EmRS is Steel air emissions reduction factor. ERj is the energy consumption reduction factor for material j. ERS is the Steel energy consumption reduction factor. 4. After finding all the required reduction factors, the by-product outputs of the secondary mining process are calculated according to the following equations. Yi j = Ci j ´Mj ´R j (18) Where, Yij is the by-product output i of material j extraction. Ci j is the contribution factor of output i with respect to materials j extraction. 53 Mj is the amount of material j that enters the secondary mining process, which is found by calculating the amount of materials that is needed for producing N units divided by m. Rj is the air emissions or solid waste reduction factor for material j. 5. From energy consumption of this process, we are able to determine the amount of releases resulting from each process using utility via energy Equations (7), (8), (9), and (10). 6. By adding all the results together, the total outputs will be obtained. 3.4. The Demanufacturing Process The demanufacturing process is part of remanufacturing, which is considered as an approach to reserve natural resources and accomplish sustainable development. In the this section, the concept of remanufacturing is elaborated, which is followed by the demanufacturing process and its model and methodology of analysis. 3.4.1 Remanufacturing Remanufacturing is an environmentally, economically and socially desirable approach of secondary mining. Its main objective is to accomplish sustainable development through a product take-back system (Fig. 3.10). It is a value-added recovery not just materials recovery, since it preserves the product parts identified by disassembly, sorting, cleaning, refurbishing, and reassembly and transforms durable products to serve their original function by substituting worn or damaged parts. It also recaptures most of 54 the value embedded that entered a product into its initial manufacture of the product, i.e. energy, labor, and capital equipment. Lund [1984]. described remanufacturing as “..an industrial process in which worn-out products are restored to like-new condition. Through a series of industrial processes in a factory environment, a discarded product is completely disassembled. Usable parts are cleaned, refurbished, and put into inventory. Then the product is reassembled from old parts (and where necessary new parts) to produce a unit fully equivalent or sometimes superior in performance and expected lifetime to the original new product.” Remanufacturing involves the reuse of obsolescent or obsolete products by retaining serviceable parts, refurbishing usable parts, and introducing replacement components (either identical or upgraded) [Graedel and Allenby 1995]. Fleischmann et al. [1997]. defined remanufacturing as a process of bringing the used products back to ‘as new” condition by performing the necessary operations such as disassembly, overhaul, and replacement. 3.4.1.1 · The Operations of the Remanufacturing Process Check-in This is the first stage of the remanufacturing process, in which the manufacturer receives the takeback products. An inspection is first performed to identify damages in the products and classify the product as remanufacturable or non-remanufacturable. Then, the product is conveyed to the next stage for disassembly. However, this operation can be 56 performed at the resident’s or dealer’s from where the product is taken back, this way when the product comes in will go directly for disassembly. · Disassembly Disassembling is the first step in processing for remanufacturing that requires attention in the design process for the product since it establishes a gateway for parts to the remanufacturing processes. The effect of disassembly impacts several areas in the facility, i.e. production control, scheduling, and materials planning. Robotisation may be applied in the disassembly process when large batches are processed; however, manual (low skilled) labor is the most commonly used. The two main factors of the disassembly process are the time and easiness of disassembly. These factors are the clues to the success in the remanufacturing process. In other words, if a product takes a long time for disassembly the cost will increase. Thus, it will not be cost-effective to remanufacture the products. · Cleaning This operation is essential for the removal of the dirt on the components of the disassembled product. That could alter the functionality of the component. However, this phase of demanufacturing, which damages the environment because of the chemicals used and waste generated. It may include washing, removing paint, de-greasing, deoiling, and de-rusting. Techniques vary to do the job. However, it may be as simple as using hot water to using ultrasonic cleaning. · Inspection and Sorting In this operation, an assessment to the condition of parts on their re-usability or reconditionability is done. It comes after the cleaning phase since it is hard to inspect 57 dirty parts. Consequently, The components are classified in this stage into three categories as follows: Ø Good quality They are suitable for remanufacturing. Ø Moderate Components are suitable for repairing and then they can be reconditioned and reused in newer products as spare parts. Ø Obsolete Suitable only for materials recovery, where the un-reusable components are transferred for shredding. · Reconditioning It is a pre-assembly process, which concerns the parts that have to be painted or surface treated. · Reassembly This operation depends on the number of reusable parts from the disassembly process, which is subjected to variation regarding the number and quality of “takeback” products. · Testing This is a functional inspection of remanufactured product, which aims to guarantee that the remanufactured product is of the same quality as a new one. · Packaging This operation involves the packaging of the remanufactured product. 58 To be able to remanufacture a product it requires that [Klausner and Grimm 1999].: 1. There is a high demand for the remanufactured product. 2. Parts of the product can be reused after being disassembled, and reconditioned. 3. The remanufacturing cost is low to be able to sell the remanufactured product no more than 60% of the price of the new one 4. The number of taken back products is sufficient for an efficient remanufacturing production line. 59 3.4.2 The Methodology for Analyzing the Demanufacturing Process Model The demanufacturing process is the third scenario of this research. This process preserves the products parts identity; it includes the checking in, disassembling, cleaning, inspection and sorting, and remanufacturing operations. This process is the equivalent process to raw material extraction of the current manufacturing process, and the discussed secondary mining process, which is a way to recover the material content of the retired products for product takeback. It is very important to realize that the extracted components in this scenario have embedded value. Meaning that the value placed within the component during its initial manufacture (energy, labor, and materials) is preserved and available for reuse. This is not the case for the current and secondary mining scenarios, where energy and overhead are added to the materials to produce the same component. As illustrated in Fig. 3.10, the product after production is leased to the consumer for use. At the end of the product life, it is reclaimed and returned to the manufacturer for demanufacturing where it is disassembled, parts are then sorted either for reuse, cleaning, refurbishing, and reassembly, or for secondary mining, depending on its quality and reusability condition. 3.4.1.2 Check-in According to Fig. 3.10, N products are reclaimed, and entered the check-in operation. The product might be classified as non-remanufactured or remanufactured product. However, with either classification, products are conveyed to the disassembly process as discussed below. 60 Non-remanufactured product This classification of the product at check-in will send the product to the secondary mining process, however, some parts might be reused as spare parts for repair or in other remanufacturable products if the cost of remanufacturing of these parts is lower than using new parts. In this option, the product is transferred to the disassembly process, yet it is disassembled just to the level where the required part could be taken out, and then it is directly conveyed to the secondary mining process. Remanufactured product In this process, the returned product is disassembled. To handle the disassembled parts many options are used, and they include the following: 1. Reusable parts or the parts of moderate quality are restored and then reused: · By selling the reusable parts to another manufacturer. · Sending it overseas where consumer is not insistent on buying the latest technology (that doesn’t indicate that reusable parts are of less quality). · Reassembly of the product by the same manufacturer and giving it a second life. 2. The worn-out parts are mined. 3.4.1.3 Disassembly As soon as either classification won’t affect the product since it will yield for disassembly, then N products are transferred for disassembly. After check in the product is conveyed to the disassembly process, which is the gateway to the whole remanufacturing process, and as discussed in the above the disassembly process is a 61 function of time, the longer the disassembly process the higher the cost of the remanufacturing process. Analysis of the Disassembly Process Total disassembly time T can be expressed by the following equation: k T = ån i ´ ti (19) i =1 where, ni is the number of the ith component. ti is the disassembly time for ith component. Taking into consideration joint type, all the operations that are included in the disassembly of one component, i.e. pick up, removal of the component. Where the cost of disassembly can be expressed by the following equation: As for the disassembly cost, CD, CD= E*CE + (CL+Co).T + Ct (20) Where, E is the energy consumed in disassembling N products. CE is the cost of consuming one Kilo-joule of energy. T is the total disassembly time. CL is the hourly labor cost. Co is the overhead cost. Ct is the tools cost. Disassembly can be done either manually or including power tools in the disassembly process. Therefore, the disassembly time will be: 62 T = tm + ta (21) Where, tm is manual disassembly time . ta is disassembly with power tools time. The purpose of this research is to design a demanufacturing process that is sustainable, and cost-effective. Therefore, there should be a trade-off between both tm and ta since, the higher tm the higher the cost of disassembly (labor and overhead), and the less use of powered tools, the less environmental impact, less energy consumption and as a result less emissions. The methodology · The time of the disassembly of one air conditioner is estimated, based on the results of the research of [Dowie and Kelly 1994]. and personal experience at a disassembly workshop, by applying Equation (19). · The energy consumed by the power tools is calculated according to Equation (22), which helped in evaluating the emissions of using power tools based on Equations (7), (8), (9), and (10). P =V ´I (22) Where, V is the voltage (in volts) on which the tool works. I is the electric current (in Amps) of the tool. · Estimation of power needed for lighting and emissions were also calculated based on the same air emission energy related equations. · The power-consumed form using HVAC in the plant is also considered and studied. 63 · All the results are added together to estimate the total environmental impact. 3.4.1.4 Cleaning The reusable parts must be cleaned to remove all the dirt that may alter the service of the part more discussion about this operation and its environmental impact is elaborated in chapter 4. 3.4.1.5 Inspection and sorting After the cleaning process, all parts and components are conveyed for inspection and sorting. Consequently, we will end in two streams, either reusable parts or secondary mining ability. The mass, M, of N remanufacturable products is that flows to the secondary mining k (23-a) M = N ´ å (1 - r i ) ´ ni ´ mi i =1 Where, r is the reusability probability of the ith component ni is the number of component i that will be sent for secondary mining. m is the mass of component i. k is the number of components in one unit. Or, if the calculations were per unit, then M = N´ (1- r) ´ m + SP (23-b) 64 Where, r is the reusability probability of the product m is the mass of one unit. The output of the secondary mining process, O, is (24) O =n ´ M Where, n is the secondary mining efficiency. And the fluff is calculated according to Equation (25). F = FP + FS (25) (25-a) FS =(1-n)´M Where, FS is the fluff results of secondary mining and is calculated according to Equation (25-a). 3.5. Economic Cost There are two costs that affect the total economic cost, direct meaning internalized cost that is related to the cost of primary raw materials, secondary mining, and the demanufacturing process, and hidden cost, which are the external environmental costs. 65 3.5.1. Direct Cost Primary Mining Scenario n CP = åC iP (26) ´ M iP i=1 Where, CiP is the cost of primary materials i in $/lb. MiP is the amount of primary material i used in producing N units. This direct cost includes the cost of overhead and , labor, tools, ..etc. Secondary Mining Scenario n CS = åC iS (27) ´ Mi S i =1 Where, CiS is the cost of secondary materials i in $/lb. MiS is the amount of secondary material i used in producing N units. This direct cost includes the cost of overhead and, labor, tools, ..etc. It should be emphasized that CP for the primary materials used instead of wastes generated to be able to produce N units in this stable production are added to CS to get the total cost of the secondary mining. (27¢) C T = C P+ C S Demanufacturing Scenario In the demanufacturing scenario, the use of primary and secondary materials might be included, thus, Equations (26) and (27) are applied. Besides, the cost of the disassembly should be included by applying Equation (20). The total cost will be: 66 C T = C P+ C S + C D 3.5.2. (28) Environmental hidden costs (external costs) There are numerous methods to estimate the cost of air pollutants, which are sponsored by various organizations e.g., Tellus Institute, California Energy Commission, New York Public Service Commission,..etc. For the purpose of this research, the Tellus Institute values are used because more complete data set are provided [NREL 2000]. (29) CE = MO ´CH Where, CH is the hidden cost in $/lb. MO is the output mass in lb. 3.6 Summary This chapter has introduced a methodology to compare the current manufacturing process, the secondary mining process and the demanufacturing process. The current manufacturing process uses primary natural resources and considers the product as a possess for the consumer. In the secondary mining process the consumer buys the functionality of the product and at the retirement life, it is shredded and recover its raw material. Finally, the demanufacturing process scenario the consumer buys as well the product’s service. But, at the end of life of the product, it is returned to the producer, and the products embedded value is recovered (energy, labor, raw materials,..). In the next chapter, the results for an application of HVAC industry for the suggested models are introduced. 67 Moreover, the discussion of the environmental, economic, and social dimensions of the system are described in chapter 5 so as to investigate the most sustainable scenario. 68 CHAPTER 4 RESULTS This chapter presents the results obtained from the sustainability analysis methodology applied to current manufacturing, the secondary mining, and the demanufacturing scenarios respectively, as discussed in chapter 3. It should be noted that these results do not include the manufacture of materials into components in the current and secondary mining processes, which consumes energy and materials and produces waste and emissions. Since in the demanufacturing scenario the components have already been manufactured, additional energy consumption and emissions from this production process are eliminated. 4.1. The Current Manufacturing Process Scenario Production Based on the data from a local HVAC company, which produces on average 100,20012 air conditioner units per year, the amount of production materials needed is shown in Table 4.1. Taking into account that 0.2%13 of sales (or 84 units) are sent to 12 Based on manufacturer sales information. 13 Based on manufacturer sales information. 69 scrap as a result of defects in the manufacturing process, N is assumed to be 100,116 units. By applying Equation (1), where t 14 = 0.99916 and R1, R2, R3, and R4 are 1,688,770.80, 4,355,894.40, 1,101,398.40 and 24,849.6 lb. representing the amount of Copper, Steel, Aluminum, and Rubber used respectively in the production of 100,200 units per year, the total material15 that is used in producing N units is: P= (1,688,770.80+ 4,355,894.40 + 1,101,398.40 + 24,849.6) ´ 0.99916 P= 7,164,889.63 lb. By applying Equation (2) and considering that m16 =0.99653 the amount of production materials that goes to scrap, SP is SP = (1,688,770.8 + 4,355,894.4 + 1,101,398.4 + 24,849.6) ´ (1-0.99916) ´ 0.99653 SP = 6,002.67 lb. The production fluff, FP, is calculated by applying Equation (3): FP = (1,688,770.8 + 4,355,894.4 + 1,101,398.4 + 24,849.6) ´ (1-0.99916) ´ (1-0.99653) FP = 20.90 lb. Consumer Use After consumer use, some units are sent to the landfill and others to scrap. From Equation (4), the amount of material from the units are sent to scrap, SC is determined 14 Where t= 1-Number of scrap units/Total number of units. 15 Taking into account just the main materials used. where it is assumed that all rubber will go for fluff and the rest is recyclable materials, see Table 3.1 for values. m = (1-Rrubber/Rtotal). 16 70 assuming q equals to 0.643 [EPA 2000] and 71.32 lb. is X¢17. SC = 0.643 ´ 100,116 ´ 71.32 SC = 4,591,195.62 lb. The amount of production materials in the air conditioner units that will be sent to the landfill (i.e. consumer fluff) is calculated by applying Equation (5) is: FC = (1-0.643) ´ 100,116 ´ 71.57 + (0.634 ´ 100,116 ´ 0.25)18 FC = 2,574,106.50 lb. Extraction Assuming the manufacturing system is stable (i.e. production is static), the extraction amount of Copper, Steel, Aluminum, and Rubber are listed in Table 4.1 are included to produce 100,200 air conditioner units per year. Material Copper Wt / unit (lb.) 16.85 Wt per year (lb.) (Rj) 1,688,770.80 Steel 43.47 4,355,894.40 Aluminum 10.99 1,101,398.40 Rubber 0.25 24,849.60 Table 4.1: Air Conditioner Materials Used Per Year. Table 4.2 demonstrates the materials flow required by the extraction process to produce 100,200 air conditioner units per year. The values are estimated by applying the 17 18 X¢ is X excluding rubber. Fluff that results from rubber in the units that is sent to scrap. 71 methodology described in chapter 3 (section 3.2.1) and applying Equation (6). However, the input values are provided as info only for the reader. More detailed discussion of input values is outside the scope of this research. Interested readers should refer to [Ayres and Ayres 1998]. for more detailed information. On the other hand, the scrap materials sent (of the commonly supplied in the raw materials of percentage 43% of Copper, 32 % of Aluminum [ISRI 2000], and 65% of steel [Fenton 1997]. are considered as materials produced within the extraction process as shown in Figs. 3.3, 3.4, and 3.5 is directly included in the calculations as shown in Table 4.2. The total amount of solid waste material19 from the extraction process that is disposed of at a landfill, 20FR is equal to 294,550,397.9 lbs, the total amount of outputs of the extraction materials process based on the results in Table 4.2 are shown as follows in Table 4.3. 19 Concentration Wastes, Slag, Alumina Particulate, Fluorides, and Ferrous Sulfate are considered as solid waste that is sent to the landfill. 20 See Fig. 3.2. 72 Inputs Total Outputs Total N/A Overburden Ores 538,109,971.80 288,730,771.70 Ores 288,730,772 283,697,099.70 Reverts 294,458.46 Concentration Wastes Domestic Concentration Imported Bauxite Lime Coal Caustic Soda Other water Air H2SO4 3,285,471.40 220,027.50 Mining Explosives Concentration 10,068,961.13 N/A 53,968.52 1,668,505.60 1,953,907.80 372,54284 2,149,805.20 Smelting and Refining Domestic 100,68961 Products Concentration Imports 444,301.23 N2 6,472,859.08 scrap Lime Fluxes Coke N2 O2 Limestone Silica 1,918,790.40 1,472.29 101,056.75 1,058,482.30 6,472,859.10 1,594,257.40 221,381.08 657,534.84 CO CO2 Reverts H2 Slag SO2 Gaseous Alumina Particulate Fluorides 2,966,364.09 8,313,653.52 169,879.88 98,007.62 10,449,311.51 396,861.14 396,016.75 45,157.33 H2SO4 byproduct Refining and Pickling Pig Iron 2,360,894.8 Scrap 2,545,149.1 Lime 152,456.3 Ferro Alloy 39,203.05 H2SO4 18,294.76 O2 283,133.14 Reverts Slag CO2 Ferrous Sulfate 2,081.64 3,434,959.81 196,211.46 328,870.03 435,589.44 27,877.72 Table 4.2: Materials Flow Required for the Extraction Process in Lb. 73 Output Amount (lb.) Landfills 294,550,397.90 CO2 8,749,242.96 Gaseous 396,016.75 SO2 396,861.14 N2 6,472,859.08 H2 98,007.62 CO 2,966,364.09 Table 4.3: Total Outputs for All Materials of the Extraction Process. Furthermore, based on data from Graedel et al. [1995], the energy consumed in the production of primary Aluminum, Copper and Steel is listed in Table 4.4. By applying the energy related air emission Equations (7), (8), (9), and (10) and based on the data in Table 4.4, results of the emission amounts associated with energy use as shown in Tables 4.5, 4.6, and 4.7. Material Copper Energy consumed (GJ/Mg) 91 Steel 31 Aluminum 270 Table 4.4: Energy Consumed in the Production of the Extraction of Copper, Steel, and Aluminum [Graedel and Allenby 1995]. 74 Air Emissions Amount (lb.) CO2 25,931,526.87 NOx 85,044.25 SO2 178,453.52 Table 4.5: Air Emissions Associated with Energy Use Required for Extracting Copper. Air Emissions Amount (lb.) CO2 50,179,252.92 NOx 164,566.40 SO2 345,319.59 Table 4.6: Air Emissions Associated with Energy Use Required for Extracting Aluminum. Air Emissions Amount (lb.) CO2 22,785,314.23 NOx 74,726.03 SO2 156,802.16 Table 4.7: Air Emissions Associated with Energy Use Required for Extracting Steel. By adding the results in Tables 4.5, 4.6, and 4.7 the total air emissions associated with energy use required for producing 100,200 air conditioner units are estimated and shown in Table 4.8. 75 Air Emissions Amount (lb.) CO2 98,896,094.02 NOx 324,336.70 SO2 680,575.27 Table 4.8: Energy Related Air Emissions for Extracting Materials Used in Producing 100,200 Air Conditioner Units. The total impact of extracting raw materials is determined by combining the results of materials extraction with its energy consumption emissions. Taking into account that CO will be reacted with Oxygen atoms in the atmosphere to form CO2 21. on the other hand, FC and FP should be combined and added to FR (see Table 4.3) which will give a total of 297,124,525.30 lb. The results are shown in Table 4.9. 21 See appendix B for calculations 76 Output Amount (lb.) Landfills 297,124,525.30 CO2 112,306,766.30 Gaseous 396,016.75 SO2 1,077,436.41 N2 6,472,859.08 H2 98,007.62 NOx 324,336.70 Table 4.9: The Total Environmental Impact of the Primary Mining Process Scenario. 4.2 The Secondary Mining Process Scenario This is a material recovery process, in which the product is shredded at the retirement phase; to reuse the materials in producing new products. Production To get the analysis results of this “consumer service lease-manufacture own” scenario, Equations (11), (12), (13) are applied. In this case the values W1, W2, W3, and W4 are 1,688,770.80, 4,355,894.40, 1,101,398.40, and 24,849.6 lb. representing the amount of Copper, Steel, Aluminum, and Rubber used respectively in the production of 100,200 units per year respectively are considered. In addition, the same production efficiency and production wastes secondary mining efficiency (as in section 4.1) are applied for a net production of 100,116 units, resulting in22: 22 See section 4.1 for more detailed discussion of this process and these process characteristics. 77 The amount of production raw material required, P= 7,164,889.63 lb. Production scrap, SP SP = 6,002.67 lb. And The production fluff, FP FP = 20.90 lb. Consumer Use After consumer use, all the leased units (100,116) are returned to the manufacturer for secondary mining, and the 84 scrap units are conveyed to the stream of secondary mining, which results in a total of 100,200 units. To be able to find the amounts of, Copper, Steel, and Aluminum that are sent for secondary mining, the amount of each material in one unit is multiplied per 100,200 units. as shown in Table 4.10. Material Wt / one unit Weight in lb. Copper 16.854 1,688,770.800 Steel 43.472 4,355,894.400 Aluminum 10.992 1,101,398.400 Table 4.10: Materials That Are Sent for Secondary Mining Process. Then, the reduction factors are found by applying Equations (16) and (17). The results are shown in Table 4.11. 78 Material EmRi SRi Copper 0.069 0.025 Steel 0.140 0.030 Aluminum 0.030 0.011 Table 4.11: Reduction Factors for Copper, Steel and Aluminum. By using the above reduction factors and the methodology discussed in section 3.3.1, the total results of this process are shown in Table 4.12. Outputs Amount (lbs) Landfills 489,389.06 CO2 265,113.30 Gaseous 25,274.99 SO2 25,328.88 N2 838,209.29 H2 21,998.76 CO 384,132.25 Table 4.12: Secondary Mining Process Results. Furthermore, based on data from Graedel et al. [1995], the energy consumed for the production of secondary Copper, Steel, and Aluminum, is demonstrated in Table 4.13. 79 Material Copper Energy consumed (GJ/Mg) 13 Steel 9 Aluminum 17 Table 4.13: Energy Consumed in the Production of Secondary Copper, Steel, and Aluminum [Graedel and Allenby, 1995]. By applying the energy related air emissions Equations (7), (8), (9), and (10) the results shown in Tables 4.14, 4.15, and 4.16 are produced. Air Emission Amount (lb.) CO2 3,704,503.84 NOx 12,149.18 SO2 25,493.36 Table 4.14: Energy Emissions for Mining Secondary Copper. Air Emission Amount (lb.) CO2 3,159,434.44 NOx 10,361.59 SO2 21,742.34 Table 4.15: Energy Emissions for Mining Secondary Aluminum. 80 Air Emission Amount (lb.) CO2 6,615,091.23 NOx 21,694.65 SO2 45,523.21 Table 4.16: Energy Emissions for Mining Secondary Steel. By adding the results in Tables 4.14, 4.15, and 4.16 we will get the total utility related air emissions for producing 100,200 air conditioner units as shown in Table 4.17. Air Emission Amount (lb.) CO2 13,479,029.51 NOx 44,205.42 SO2 92,758.91 Table 4.17: Utility Related Air Emissions for Secondary Mining Materials Used in the Production of 100,200 Air Conditioners. As a result, the total impact of secondary mining the 100,200 air conditioner units is obtained by adding the results of secondary mining in Table 4.12 and its Utility related air emissions in Table 4.17 as shown in Table 4.18. These results take into consideration that CO will react with Oxygen atoms in the air to form CO223, and total landfills are the landfills that result from this process FR and FP see Fig. 3.9. 23 See Appendix B for Calculations. 81 Outputs Amount (lb.) Landfills 489,409.89 CO2 14,347,779.21 Gaseous 25,274.99 SO2 118,087.79 N2 838,209.29 H2 21,998.76 NOx 44,205.42 Table 4.18: The Environmental Impact of Secondary Mining Materials Process. From Table 4.18, it is obvious that there are landfills deposits in the amount of 489,409.89 lb., which results in materials reduction that will prevent the production of 100,200 units. For that reason the manufacturer would need extracted raw material by the amount of ‘landfills’ generated from the secondary mining process. The results are shown in Table 4.19. Material Amount (lb.) Copper 5,428.17 Steel 488,908.42 Aluminum 480.64 Table 4.19: The Amount of Extracted Raw Materials Needed. 82 By applying the methodology discussed in section 3.2.1 for analyzing the impact of material extraction for materials shown in Table 4.19, the results obtained are presented in Table 4.20. Outputs Amount (lb.) Landfills 1,686,361.167 CO2 768,800.242 Gaseous 1,272.907 SO2 1,275.621 N2 419,306.8 H2 19,067.43 Table 4.20: The Environmental Impact of the Extracted Materials for the Secondary Mining Materials Scenario. The utility related air emissions for the materials extraction process for materials that are needed for producing 100,200 units are also considered. The results are shown in Table 4.21. Air Emission Amount (lb.) CO2 2,662,687.37 NOx 8,732.47 SO2 18,323.87 Table 4.21: The Utility Related Air Emissions Resulting from Energy Consumption for Materials Extraction Process within the Secondary Mining Scenario. 83 The environmental impact of the extracted materials in Table 4.20 and the utility related air emissions resulting from energy consumption in Table 4.21 are combined. Thus, the total environmental impact of materials extraction for materials needed in the secondary mining scenario are shown in Table 4.22. Outputs Amount (lb.) Landfills 1,686,361.17 CO2 3,431,487.61 Gaseous 1,272.91 SO2 19,599.49 N2 419,306.80 H2 19,067.43 NOx 8,732.47 Table 4.22: The Total Environmental Impact for Extracting Materials for the Secondary Mining Materials Scenario. Ultimately, The total environmental impact of the secondary mining scenario are calculated by combining the results in Table 4.18 and Table 4.22. The results are shown in Table 4.23. 84 Outputs Amount (lb.) Landfills 2,175,771.06 CO2 17,779,266.82 Gaseous 26,547.89 SO2 137,687.28 N2 1,257,516.10 H2 41,066.19 NOx 52,937.89 Table 4.23: The Total Environmental Impact the Secondary Mining Materials Scenario. 4.3. The Demanufacturing Process Scenario This scenario is based on the concept of selling the service of the product “consumer service lease-manufacturer own”. Hence, at the retirement stage of the product, the consumer return it to the manufacturer for disassembling and reusing of the parts. Production In this case the values R1, R2, R3, and R4 are 1,688,770.80, 4,355,894.40, 1,101,398.40 and 24,849.6 lb. representing the amount of Copper, Steel, Aluminum, and Rubber used respectively in the production of 100,200 units per year respectively are 85 considered. In addition, the same production efficiency and production wastes secondary mining efficiency are applied for a net production of 100,116 units, resulting in24: The amount of production raw material required, P= 7,164,889.63 lb. Production scrap, SP SP = 6,002.67 lb. And the production fluff, FP, is FP = 20.90 lb. The 100,116 units are leased for consumers who return them to the manufacturer for demanufacturing and then remanufacturing. · Check in This is the first stage in the demanufacturing process, in which the manufacturer receives the returned products. During this stage the products are inspected and classified as a remanufacturable or non-remanufacturable product. · Disassembly In this stage, the returned products are disassembled into parts. The methodology that is followed to study this process is described below. · Determine an estimation of the product disassembly time. Two scenarios were considered, manual disassembly and use of power tools. The results are shown in Table 4.24. 24 See section 4.1.1 for more detailed discussion of this process and these process characteristics. 86 Process Operation Time (sec) Manual Disassembly Removal screws of the top panel Pick-up tool 0.7 Time (sec) Power Tools Disassembly 0.7 Unscrewing Put down tool Pick-up tool 30 0.7 0.7 7.5 0.7 0.7 Unscrewing Put down tool Remove cover Pick-up tool 24 0.7 2.5 0.7 6 0.7 2.5 0.7 Unscrewing Put down tool Disconnect connectors Pick up tool 12 0.7 15 0 3 0.7 15 0.7 Remove Snap fits Put down tools Removal of control box Pick-up tool 4.5 4.5 0 2.5 0.7 0.7 2.5 0.7 Unscrewing Put down tool Remove capacitor Remove alternator Pick-up tool 48.6 0.7 1 1 0.7 12.15 0.7 1 1 0.7 Unscrewing Put down tool Remove lower panel Pick-up tool 24 0.7 2.5 0.7 6 0.7 2.5 0.7 Unscrewing Put down tool Remove grill Pick-up tool 24 0.7 2.5 0.7 6 0.7 2.5 0.7 Remove nuts Put down tool Remove Logo Remove Grill Disconnect connectors Pick-up tool 21.6 0.7 0.3 2.5 4.5 0.7 21.6 0.7 0.3 2.5 4.5 0.7 Unscrewing Put down tool Remove Motor Remove fan blade 0.6 0.7 2.5 2.5 0.6 0.7 2.5 2.5 Disassemble the control box Disassemble the lower cover and the control box Remove snap fits, and removal of control box Disassembly of control box Remove the lower panel of the control box Disassembly the grill of the fan Disassemble the fan and fan motor from the grill Disassemble motor fan and fan blade 87 Disassemble the two valves Disassemble valves from heat exchange and tubes Remove compressor from bottom panel Pick-up tool 0.7 0.7 Unscrewing Put down tool Pick-up tool Unscrewing Put down tool Remove valve base Pick-up tool 21.6 0.7 0.7 12 0.7 0.3 0.7 5.4 0.7 0.7 3 0.7 0.3 0.7 De-brazing25 Put down tool Remove 2 valves Remove Guard Remove Heat exchanger Pick-up tool 1260 0.7 0.5 9 2.5 0.7 1260 0.7 0.5 9 2.5 0.7 Unscrew26 Put down tool Remove compressor Remove bottom panel 26.4 0.7 2.5 2.5 26.4 0.7 2.5 2.5 Table 4.24: Estimation of Disassembly Times for Air Conditioner27. By adding the results of Table 4.24 together, the total manual disassembly time by applying Equation (19) for one air conditioner unit is 1,582.7 sec (26.37 min), and 1,436.9 sec (23.95 min) for the second scenario of the disassembly process. In this second case and according to Equation (21) ta= 49.05 sec, i.e. power tools are used for 49.05 sec (0.82 min) and tm = 1,387.85 sec. The Air Emissions Associated for Using Power Tools · It is assumed that the power tools have the specifications of 4 A and 120 V AC. The power needed is calculated by using Equation (22) as follows: P = 120 ´ 4 = 480 Watt 25 This is a hypothetical estimation of time 3 min. It includes 3 secs extra because of obstruction. 27 Calculations of disassembly of time estimation are in Appendix A. 26 88 Correspondingly, from the results obtained in Table 4.24, the total time for using the power tools in the disassembly of one unit is 49.05 sec. Then, the energy consumed in KJ can be calculated by multiplying P from Equation (22) by the time use as follows: E = 480 ´ 49.05 E = 23.54 kJ per unit by using the energy related air emissions Equations (7), (8), (9) and E are calculated, the amounts of CO2 , NOx , and SO2 produced are estimated. · The utility related air emissions for using power tools during the disassembly of one air conditioner is calculated with the results presented in Table 4.25. Air Emission Amount (lb.) CO2 8.78 ´ 10 -3 NOx 2.87 ´ 10 –5 SO2 6.03 ´ 10 -5 Table 4.25: Utility Related Air Emissions for Disassembly One Air Conditioner. All the returned units are disassembled even the ones classified as nonremanufacturable since still they include some reusable parts. Thus, the total emissions for disassembling 100,116 air conditioner units per year, which are calculated by multiplying the results in Table 4.25 by 100,116, are illustrated in Table 4.26. 89 Air Emission Amount (lb.) CO2 879.02 NOx 2.87 SO2 6.04 Table 4.26: Total Utility Related Air Emissions for Disassembly by Using Power Tools. As described in Table 4.24, one of the main disassembly operations that produce CO2 emissions because of using propane is ‘de-brazing’. This operation lasts for 21 minutes per one air conditioner unit, which means emitting 0.2422 lb. CO228. Consequently, for ‘de-brazing’ 100,116 air conditioner units per year the amount of CO2 emitted is obtained by multiplying 0.2422 lb. CO2 by 100,116, which results in 24,248.10 lb. 4.3.1 Overhead of the Demanufacturing Process The total energy consumption (including overhead) and its related air emissions are included in the environmental impact of the current manufacturing scenario (see Table 4.4) and the secondary mining scenario (see Table 4.13). To allow us to compare the three scenarios, overhead should be included in the calculations of the demanufacturing process. 28 See appendix C for calculations. 90 Lighting of the disassembly Room According To Mark’s handbook [Avallone and Baumeister III 1996], lighting of the disassembly room requires 3 W/ft2. Let’s assume that the area allotted for the disassembly process is 25 ´ 25 ft2 . The total energy consumption is therefore 1,875 W. As discussed before, one unit takes 1,582.7 sec to be disassembled manually, and then the utility requirement is obtained by multiplying the time of disassembly one unit by the energy consumption of lighting. The results are as follows: E= 1,875 W * 1,582.7 sec E = 2,967,562.5 J E = 2,967.56 kJ The air emissions related of lighting the disassembly room for the disassembly using power tools of one air conditioner are estimated by using the air emissions Equations (7), (8), and (9) are as listed in Table 4.27. The total air emissions of emissions related of lighting the disassembly room for the disassembly of 100,116 air conditioner units are calculated by multiplying the results of Table 4.27 by 100,116 are listed in Table 4.28. Air Emission Amount (lb.) CO2 1.104 NOx 3.62 ´ 10 -3 SO2 7.60 ´ 10 -3 Table 4.27: Utility Related Air Emissions for Lighting during the Disassembly of One Air Conditioner Manually. 91 Air Emission Amount (lb.) CO2 110,528.1 NOx 362.42 SO2 760.88 Table 4.28: Utility Related Air Emissions for Lighting during the Disassembly of 100,116 Air Conditioner Units Manually. As discussed before, one unit takes 1,436.9 sec to be disassembled using power tools, and then the utility requirement is obtained by multiplying the time of disassembly one unit by the energy consumption of lighting. The results are as follows: E= 1,875 W* 1,436.9 sec E = 2,694,187.5 J E = 2,694.19 kJ The air emissions related of lighting the disassembly room for the disassembly of one air conditioner are estimated by using the air emissions Equations (7), (8), and (9) are as listed in Table 4.29. The total air emissions of emissions related of lighting the disassembly room for the disassembly of 100,116 air conditioner units are calculated by multiplying the results of Table 4.29 by 100,116 are listed in Table 4.30. Emission Amount (lb.) CO2 1.00 NOx 3.28 ´ 10 -3 SO2 6.90 ´ 10 -3 Table 4.29: Utility Related Air Emissions for Lighting during the Disassembly of One Air Conditioner Unit Using Power Tools. 92 The total air emissions related to lightning during the disassembly of 100,116 air conditioner units are as follows in Table 4.30. Emission Amount (lb.) CO2 100,340.10 NOx 328.38 SO2 690.80 Table 4.30: Utility Related Air Emissions for Lighting During the Disassembly of 100,116 Air Conditioner Units Using Power Tools. HVAC of the disassembly Warehouse According to ASHRAE Handbook [ASHRAE 1995]. and based on the weather in South Carolina, the HVAC energy consumption would be negligible. Summary of results Finally, the total emissions of the manual disassembly process are estimated by combining the emission of CO2 24,248.10 lb. from the ‘de-brazing’ operation, with the results form Table 4.28. The results are listed in Table 4.31. Air Emission Amount (lb.) CO2 134,776.2 NOx 362.42 SO2 760.88 Table 4.31: Total Air Emissions for Manual Disassembly of 100,116 Air Conditioner Units. 93 Consequently, the total emissions of the disassembly process using power tools are estimated by combining the emission of CO2 24,248.10 lb. from the ‘de-brazing’ operation, with the results form Table 4.26 and Table 4.30. The results are listed in Table 4.32. Air Emission Amount (lb.) CO2 125,467.2 NOx 331.25 SO2 696.84 Table 4.32: Total Air Emissions for Disassembly Using Power Tools of 100,116 Air Conditioner Units. · Cleaning As discussed before, cleaning is a vital operation in the demanufacturing process. It is particularly important in inspecting and sorting the disassembled parts. There are many applicable cleaning methods and technologies that are applied either by current remanufacturing companies or under research. However, to apply any cleaning technology many issues should be taken into consideration, such as; the type of disassembled parts, the type of contaminant (oils, greases, particulate), and the level of cleaning the parts requires (i.e. in the sorting and inspection operation the to be cleaned to the level, which will allow appropriate inspection and sorting) [Spaal and Laintz 1995]. One of the techniques that can be used for cleaning in the demanufacturing process is supercritical CO2. It is a technique that uses the solvating power of CO2 above 94 its critical point temperature and pressure. There are many advantages for the use of CO2 as a cleaning fluid, it is environmentally non-hazardous, non-corrosive, non-flammable, readily available, and inexpensive [Bok, et al. 1992]. Furthermore, this cleaning leaves no residue, reusability of the solute and solvent by a simple mechanical expansion process, and most importantly no waste water [Fu, et al. 1998]. Moreover, this is an energy efficient process, which results in energy and fossil fuels savings [Mathews 2000]. In addition, in 1998, an evaluation of the feasibility of using supercritical CO2 they found promising technical and economical results. There are many other cleaning methods that might be used, e.g. using air, water, dry ice blasting. However, the cleaning operation is beyond the scope of this thesis. For further information return to the cleaning guide of cleaning methods and technologies [Steinhilper and Hudelmaier 1993]. and Fu et al. [Fu, et. al., 1998]. · Inspection and sorting As mentioned in the previous chapter, after this operation, products are conveyed to one of two streams, either reusable stream or the secondary mining ability stream. And as discussed before, a percentage of the returned units are non-remanufacturable meaning their parts either will flow to the reusability or secondary mining stream since they may contain some reusable parts as depicted in Fig. 4.1, Klausner et. al. [1999]. made a research for power tools that concluded a third of the returned units are nonremanufacturable, thus, in this research, it is assumed that a third of the returned air conditioner units are non-remanufacturable. Although there might be some reusable parts, but assuming the worst case scenario, the whole third of are non-remanufacturable units 95 are secondarily mined. Therefore, Equation (23-b) is used to calculate the secondary mining weight since the data available is not specified for each part only; the percentage of reusability compiled for the whole unit. 100% returned units 2/3 1/3 Nonremanufacturable units Remanufacturable units Reusable Parts Secondary Mining Fig. 4.1: A Flow Diagram of the Returned Air Conditioner Units. From the above discussion the reusability efficiency is 2/3 then, r = 0.667, m is the weight of one unit 71.57 lb., and N is the number of the units that are taken back 100,116. Then, M will be 2,386,045.606 lb. In addition, from production SP is 6,002.67 lb. Thus, the total amount that is conveyed to the secondary mining process is 2,392,048.28 lb. 96 By following the methodology applied for secondary mining (section 3.3.1) and combining the results with utility related air emissions by using Equations (7), (8), and (9), the total environmental impact of secondary mining the non-remanufacturable products are listed in Table 4.33. Outputs Amount (lb.) Landfills 193,091.95 CO2 5,337,170 Gaseous 9,853.97 SO2 43,325.21 N2 326,775.77 H2 8,576.21 NOx 15,941.13 Table 4.33: The Environmental Impact of Secondary Mining Materials Process of the Non-Remanufacturable Products. Based on the results from Table 4.33, and by applying Equation (24) the secondary mining efficiency, n is 7%. In order to produce 100,200 units per year, then, by the amount of wastes (landfills) generated 193,091.95 lb. materials should be extracted, which has an impact that combines the materials extraction outputs and utility related air emissions as shown in Table 4.34. 97 Outputs Amount (lb.) Landfills 462,871.45 CO2 1,337,767.89 Gaseous 496.27 SO2 7,640.85 N2 283,232.89 H2 7,433.43 NOx 3,404.36 Table 4.34: Environmental Impact of Extracting Materials to Be Able to Produce 100,200 Units. Accordingly, the total environmental impact of the demanufacturing process is calculated for the two scenarios. For the manual disassembly, the results in Tables 4.31 and 4.33 and 4.34 are combined together and obtained the results listed in Tables 4.35. Outputs Amount (lb.) Landfills 655,963.40 CO2 6,809,714.09 Gaseous 10,350.24 SO2 51,726.94 N2 610,008.66 H2 16,009.64 NOx 19,707.91 Table 4.35: Total Enviornmnetal Impact of the Demanufacuring Scneraio Manually. 98 As for the disassembly using power tools, the results in Tables 4.32 and 4.33 and 4.34 are combined together and obtained the results listed in Tables 4.36. Outputs Amount (lb.) Landfills 655,963.40 CO2 6,800,405.09 Gaseous 10,350.24 SO2 51,662.90 N2 610,008.66 H2 16,009.64 NOx 19,676.74 Table 4.36: Total Enviornmnetal Impact of the Demanufacuring Scneraio Using Power Tools. 4.4. 4.4.1 Economic Cost Calculation of Direct or internal cost Primary Mining Scenario By applying Equation (26), and using the materials information in Table 4.1, CP = 1,101,398.4 ´ 0.68* +1,688,770.8 ´ 0.86* + 4,355,894.4 ´ 0.35¨ CP = $ 3,725,856.84 CP = 37.18 $/unit * Based on the price of London Metal Exchange. ¨ Based on steel manufacturer information. 99 Secondary mining In this scenario, two costs should be considered, the secondary mined materials cost (CS) Equation (27) and the cost of primary materials (CP) Equation (26) used to be able to produce the required number of annual production, and using the information in Tables 4.10 and 4.19. The secondary mined materials cost based on the [Richardon, K. 1999]. the results are as follows: CP = 480.64 ´ 0.68 + 5,428.18 ´ 0.86 + 488,908 ´ 0.35 CP = $176,113.016 CS = 1,101,398.4 ´ 0.325 +1,688,770.8 ´ 0.425 + 4,355,894.4 ´ 0.0225 CS =$1,173,689.694 The total internal cost by applying Equation (27¢) is: CT = CP + CS CP = 1,173,689.694 + 176,113.016 CP = $1,349,802.71 CP = 13.47 $/unit Demanufacturing As for this scenario, the cost of using primary (CP) and secondary materials (CS) are accounted, besides the cost of energy consumption (CE) and the disassembly cost (CD) Equation (20) other than the cost of tools (CT). CP = 160.2 ´ 0.68 + 1,809.39 ´ 0.86 + 162,969.47 ´ 0.35 CP = $391,229.90 CS = 367,132.8 ´ 0.325 +562,923.6 ´ 0.425 + 1,451,964.8´ 0.0225 100 CS = $58,704.326 By applying Equation (20) the manual disassembly cost is: CD = 2,967.56 ´1/575,24429 ´ 100,116 + 1530 ´ 26.37/60 ´ 100,116 + 27.931 + 16.9532 ´ 100,116 ´ 21/60/15 CD = $700,154.985 By using Equation (28) the total direct or internal cost is: CT= CP + CS + CD CT= $1,150,089.205 CT = 11.48 $/ unit By applying Equation (20) the disassembly cost using power tools is: CP = 160.2 ´ 0.68 + 1,809.39 ´ 0.86 + 162,969.47 ´ 0.35 CP = $391,229.90 CS = 367,132.8 ´ 0.325 +562,923.6 ´ 0.425 + 1,451,964.8´ 0.0225 CS = $58,704.326 CD = (23.544 + 2,694.19) ´1/575,244 ´ 100,116 + 15 ´ 23.95/60 ´ 100,116 + +43.733 + 27.9 + 16.95 ´ 100,116 ´ 21/60/15 CD = $639,595.025 By using Equation (28) the total direct or internal cost is: CT= CP + CS + CD 29 Price of Energy per kJ based on South Carolina Rate [EDF 2000].. Assumed Labor Cost. 31 Torch Cost [Grainger 1996].. 32 Propane Cylinder Cost which lasts for 15 hours [Grainger 1996].. 33 Power Tool Cost [Grainger 1996].. 30 101 CT = $1,089,519.245 CP = 10.87 $/unit Thus, the direct internal cost is as shown in Table 4.37. Process Total Cost ($) Primary 37.18 Secondary 13.47 Demanufacturing Manual Demanufacturing Power Tools 11.48 10.87 Table 4.37: The Direct Internal Cost in U.S. Dollars. 4.4.2. Calculation of the environmental hidden cost Based on the Tellus study, the estimated values for air pollutants are 0.78, 3.40, and 0.012 $/lb. for SOx , NOx and CO2 , respectively [NREL 2000]. A landfill disposal fee of $35.79 per ton is used as an average rate for tipping fees [Ruston 1995]. To determine the total external cost Equation (29) is used, the total amount of pollutant produced in each scenario (Tables 4.9, 4.23, 4.35, and 4.36) is multiplied by the estimated value of the external cost and divided by 100,200 which is the number of units produced in the assumed stable production. Total external costs are shown in Table 4.38. 102 Air Emission CO2 Primary Mining $13.45 Secondary Mining $2.13 Demanufacturing Demanufacturing Manual Power tools $0.82 $0.81 SOx $8.39 $1.07 $0.40 $0.40 NOx $11.00 $1.80 $0.67 $0.67 Landfills $39.58 $0.29 $0.09 $0.09 Total $72.42 $5.29 $1.98 $1.97 Table 4.38: External Environmental Costs in U.S. Dollars. 4.4.3. Total Cost The total cost is estimated by adding the internal cost in Table 4.37 and the hidden cost in Table 4.38. The results are listed in Table 4.39. Process Total Cost ($) Primary 109.60 Secondary 18.76 Demanufacturing Manual Demanufacturing Power Tools 13.46 12.84 Table 4.39: Total Economic Costs in U.S. Dollars. In chapter 5, discussion of the results is explicated; including an illustrated comparison of the three processes from sustainability point of view is illustrated. 103 CHAPTER 5 DISCUSSION OF RESULTS 5.1. Introduction The main aim of sustainable development is to ensure that the economy and society can continue to exist without compromising the natural environment upon which our lives depend. In this chapter, an evaluation of the obtained results with respect to its environmental, economic, and social impacts towards sustainability are discussed. This will help in the assessment of the current manufacturing process and the proposed scenarios. 5.2. Environmental Sustainability In 1995, Goodland, et al. defined environmental sustainability as “ a set of constraints on the four major activities regulating the scale of the human economic subsystem: the use of renewable and nonrenewable resources on the source side, and pollution and waste assimilation on the sink side”. He believes that our environmental capacity has become limited because it is thought that the regenerative and assimilative capacity from source and sink sides is infinite. It is important to emphasize that industry has exceeded the capacity of the environment from both sides, where it uses nonrenewable resources and its production of emissions where it considers infinite sinks. 104 One of the interesting articles demonstrated that if the release of all substances that cause ozone depletion stopped now, it would take one century for it to return to its pre-CFC effectiveness [Goodland 1995]. Taking these findings into consideration, industry has to find a solution for its environmental unsustainability, immediately. The following discussion shows the environmental impact assessment of some conventional emissions to the grand cycle of earth associated with the three scenarios studied. 5.2.1 Carbon Monoxide Carbon monoxide (CO) is a colorless, odorless, tasteless, poisonous gas that results from incomplete combustion of fuels, i.e. coal, heating oil, or any combustible materials. When CO enters the body, it inhibits the blood from absorbing oxygen; thus, the heart and brain are not going to function appropriately. A person exposed to high levels of CO may die, or just complain of heart pains, headache, nausea fatigue, poor vision and concentration if just exposed to small amounts [CARB 1994]. CO is one of the emissions that result from the current, and proposed scenarios. However, in this case CO is emitted to the air, which will then react with oxygen and end up as CO2. That is the reason behind adding carbon monoxide to CO2. 105 5.2.2 Carbon Dioxide Carbon dioxide (CO2) is balanced in nature when oceans and plants absorb it34. It is emitted to the atmosphere by natural processes in equilibrium. Since the Industrial Revolution, the concentration of CO2 have risen about 28% and considered as the second prevalent greenhouse gas after water vapor, which contributes 70% of the effect. 80% of CO2 emissions are contributed to energy burned for transportation, heating, and power plants. Greenhouse gases are important to the earth, since they allow sunlight to penetrate the atmosphere to warm the earth, by infrared radiation, to about 63 °F. Otherwise, it would be 3 °F. Greenhouse gases work like a blanket to trap the infrared rays that warm the surface of the earth. CO2 is not the only gas that causes greenhouse effects, however, each greenhouse gas absorbs heat in the atmosphere differently. That’s why the idea of Global Warming Potential (GWP) has been “developed to compare the ability of each greenhouse gas to trap heat in the atmosphere relative to another gas. CO2 was chosen as a reference gas to be consistent with Intergovernmental Panel on Climate Change (IPCC) guidelines” [EPA 2000]. However, some gases, e.g. CO, NOx, SO2, don’t have GWP since there is no agreement upon the method to estimate its contribution to climate change. Each year, 6.6 billion metric tons of carbon dioxide is produced. In 1994, 1.65 billion metric tons of carbon equivalent were produced by the U.S. Almost 85% of greenhouse gas emissions are produced from the burning of fossil fuels [DOE 2000]. 34 Through a process called photosynthesis. 106 The industrial sector is one of the main contributors to CO2 emissions, which results either directly from the combustion of fossil fuels or consumption of electricity. CO2 is one of the main emissions that are produced in the current, and proposed scenarios. From the results in chapter four, it is evident that CO2 emissions were reduced by 84.17% between the current and the secondary mining scenarios. Consequently, it is decreased by 93.9% between the current and the demanufacturing process. Alternatively, the percent of reduction of CO2 between the secondary mining and the demanufacturing process is 61.7%. The amounts of CO2 produced in the three scenarios are shown in Fig. 5.1. Power tools Dis Manual Dis. Secondary 1.20E+08 1.00E+08 Amount 8.00E+07 6.00E+07 (lb.) 4.00E+07 2.00E+07 0.00E+00 Primary Carbon Dioxide Fig. 5.1: The Amount of CO2 in the Three Scenarios. 5.2.3 Sulfur Dioxide Sulfur dioxide (SO2) is produced during the combustion of fuels containing sulfur, metal smelting and other industrial processes [EPA 1998]. Although 70% of SO2 emissions are accounted to electric utility, approximately 96% of this value is contributed 107 to coal combustion. SO2 is the main cause of acid rain. When SO2 is emitted into the atmosphere, it reacts with water to form sulfuric acid (H2SO4), which then falls to the earth with rain, snow, fog or as gas and particles. When it falls dry (gas and particles); it corrodes what it settles on. This is then sometimes rinsed by rainstorms, contributing additional acidity to the existing acid rain. Acid rain affects water streams and lakes acidity in addition to its damage of trees, impact on public health, deterioration of building materials, paints, statues, and visibility degradation. Emissions of SO2 should be reduced to improve the environmental quality of water streams and lakes, visibility, public health, and slow the deterioration of buildings. However, SO2 emissions have decayed in recent years, resulting from the change of electric utilities from using high sulfur to low sulfur coal [EPA 2000]. SO2 is one of the emissions that result from the current, and proposed scenarios, because of the use of electric utility in such processes. From the results in chapter four, it is obvious that SO2 emissions were reduced by 87.22% between the current and the secondary mining scenarios. It is further diminished to 95.2% between the current and the demanufacturing process. Sequentially, the percent of reduction of SO2 between the secondary mining and the demanufacturing process is 66.4%. The amounts of SO2 produced in the three scenarios are shown in Fig. 5.2. 108 Sulfur Dioxide 1.50E+06 Power tools Dis Manual Dis. Secondar y 0.00E+00 Primary Amount 1.00E+06 (lb.) 5.00E+05 Fig. 5.2: The Amount of SO2 in the Three scenarios. 5.2.4 Nitrogen oxides Nitrogen oxides (NOx) is a term that is used to illustrate NO, NO2 and other oxides of nitrogen. NOx is another source of greenhouse gas emissions. NOx is produced duirng the combustion of fossil fuels, by industrial processes, lightning, and in the stratosphere from NOx, where fuel combustion produces the greatest amount of emissions of NOx. In 1997, 49% of the NOx emitted resulted from fuel combustion. NOx also contributes to the depletion of Ozone; which reacts in the presence of sunlight with Volatile Organic Compounds (VOCs) that are emitted from motor vehicles, chemical plants, and many other industrial sources. Ozone concentrations depend on changes in weather. It is of greatest concern during the summer since sunlight is its outmost effect. Because of emissions of VOCs and NOx into the atmosphere, there are a lot of health effects due to the exposure to Ozone, like respiratory symptoms, and lung problems in addition to the environmental problems e.g. harsh weather. National Ambient Air Quality Standards (NAAQS) established standards for Ozone with an 8-hour 0.08 109 parts per million (ppm) standard. NOx plays a role as well in the creation of acid rain35. Recently NOx emissions levels are relatively constant. Where, they decayed 1%, between 1988 and 1997, and increased 1% between 1996 and 1997. However, since 1970, NOx have increased 44% from power plants and 11% as a total [EPA 1998]. It can be determined from the results in chapter 4, that the emissions of NOx were reduced by 83.68% between the current and the secondary mining scenarios. In addition, it is reduced by 93.92% between the current and the demanufacturing process. Alternatively, the percent of reduction of NOx between the secondary mining and disassembly process using power tools is 62.8%. The amounts of NOx produced in the three scenarios are shown in Fig. 5.3. Power tools Dis Manual Dis. Secondar y 4.0E+05 Amount 3.0E+05 2.0E+05 (lb.) 1.0E+05 0.0E+00 Primary Nitrogen Oxides Fig. 5.3: The Amount of NOx in the Three scenarios. It should be emphasized at this point that the manufacture process of the materials into components is not studied in this research. This process would add more emissions to these two scenarios (primary and secondary mining) which is eliminated in the 35 See section 5.2.2 for more information. 110 demanufacturing process since components already been manufactured and it preserves its identity. 5.3. Economic Sustainability Economics is the second fundamental characteristic of sustainable development to be discussed in this chapter. According to the World Bank “sustainable development requires maintenance of the environmental and human resource base that is essential for long-term economic growth" [Foy 1990]. Notwithstanding, economist like Herman Daly view economic activity as “develops without growth”, in other words, it doesn’t grow beyond the carrying capacity of the earth36. From this macro view of the economy, Daly is taking into account the finite limits on the earth’s ability to provide materials to use and sinks for discarding our wastes. Based on that, the economic theory of sustainable development has evolved, the theory in which the economy is viewed as a subsystem of the ecosystem as shown in Fig. 5.4. As a result, this theory considers economic activity as bound by the constraints of the ecosystem having the characteristics regenerative and absorptive capacity, i.e. its ability to provide us with high quality raw materials to make things, and to break down our wastes. To be able to accomplish a sustainable economy, the economy must not surpass the limits of the ecosystem, since it will greatly decrease its capacity to support humans. Growth beyond these limits will result in negative rather than positive consequences [Motague 1998]. 36 See section 1.2 for the definition of carrying capacity. 111 Solar energy Ecosystem Recycle Matter Matter Economy Energy Energy How big should it get? Heat Fig. 5.4: The Economy as a Subsystem of the Ecosystem.37 Nonetheless, the question that is raised by facing the limits of the planet is: For how long and for how many humans can the economy support, and how much good can we accomplish? That is, how large should the economy be before it harms the ecosystem? Daly thinks that “sufficient good for the greatest number”, which means supporting the greatest number of people into the unlimited future. Hence, to achieve sustainable economic development we have to offer the greatest number of humans enough resources for a sufficiently good quality of life [Motague 1998]. To attain economic sustainability, reduction in the materials and energy use should be acknowledged in industrial production. The product take-back system, is an approach that looks for reusing the embedded value of the returned products including materials used and reducing energy consumption. By doing so, we are moving in a 37 [Daly 1996]. as cited in [Odom 2000].. 112 sustainable direction, one in which we are not exceeding the limits of the ecosystem’s capacity to regenerate natural resources and absorb wastes. In the current scenario, most of the materials used are raw, natural resources that consume large amounts of energy to transform them into products, leaving behind various production wastes. However, the secondary mining scenario preserves natural resources since it recovers and ‘downcycles’ the material embedded in the product, though, it consumes some energy and destroys the product. On the other hand, the demanufacturing process preserves the embedded value of the product (its energy, labor used, etc.) and doesn’t require a high-energy use. In Fig. 5.5 the amount of raw materials used in the production of the air conditioners per year considering the three scenarios are depicted. From Fig. 5.5, it is shown that there is a tremendous reduction in the use of natural resources, i.e. there is a percentage change of 93.1% between the current and secondary mining scenarios, and 97.3% between the current and demanufacturing scenarios. Conversely, there is a decrease in the energy consumption as shown in Fig. 5.6. It is shown that there is a tremendous reduction in the use of energy, i.e., there is a percentage change of 83.7% between the current and secondary mining scenario, and 94.2% between the current and demanufacturing scenario. 113 Demanufac turing Primary 8.0E+06 Amount 6.0E+06 4.0E+06 (lb.) 2.0E+06 0.0E+00 Secondary Raw Materials Consumption Fig. 5.5: Comparison among the Amount of Raw Materials Used. Energy Consumption Power Manual Secondary 0.00E+00 Primary 3.00E+11 2.00E+11 KJ 1.00E+11 Fig. 5.6: Comparison among the Amount of Energy Used. 5.3.1 Economic Cost As presented in Table 4.39 the cost calculated is on a per unit basis, for materials used in primary mining, secondary mining and demanufacturing. Fig. 5.7 shows the costs of the scenarios. Thus, it can be analyzed that there is a reduction in the cost of about 82.9% between current and secondary scenarios, 87.7% between current and 114 manual disassembly, and 88.3% between current and disassembly using power tools. Meaning, this system ensures promising economic results. Economic Cost in US Dollars/ Unit. Power Tools Dis. Manual Dis. Secondary 0 Primary 150 100 $/Unit 50 Fig. 5.7: The Economic Cost Per One Unit. This cost might even increase more for primary and secondary mining scenarios if the manufacture process of the materials into components is considered. Which consequently would increase the reduction in cost between these two scenarios and the demanufacturing process since components already been manufactured and it preserves its identity . 5.4. Social Sustainability As discussed before, development must be environmentally, economically, as well as socially sustainable. From this concept, care must be taken that the product takeback system is not socially destructive; conversely, outmost effort must be made to ensure that it is restorative. 115 From the definition of sustainable development38, “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” [WCED 1987], the concept of sustainability is based on the ethical principles of equity between inter and intra generations by meeting their basic needs for food, a healthy living, employment and most of all a better life. A social definition of sustainability is “the continued satisfaction of basic human needs¾food, water, shelter¾as well as higher-level social and cultural necessities such as security, freedom, education, employment, and recreation [Shearman 1990]. There should be intergenerational equity distribution of resources to have sufficient for meeting the human needs within and between generations. In the product take-back system, the reuse of products is urged, which equates to resource conservation now - for future generations, which satisfies the basic elements in the definition of social sustainability. Besides, as it was comprehended from the previous chapters the demanufacturing process is labor-intensive process, which means it is a system that would create jobs for humans. Lund et al.[1998]. conducted a study in which they estimated that approximately 73,000 firms provide work related to remanufacturing - employing 350,000 people. Furthermore, based on the results from the analysis of this system and as shown in Fig. 5.7, the product take-back system reduces the amount of waste that would be sent to landfills. In the current scenario, 297,124,525.30 lbs., in the secondary mining scenario 2,175,771.06 lbs., and in the demanufacturing scenario 655,963.40 lbs. are to be sent to the landfill. Thus, the amount of landfills has been reduced by 99.3% between the current 38 See Section 1.2 for more information. 116 and the secondary mining scenarios. On the other hand, it is 99.8% between the current scenario and the manual and power tools disassembly scenarios. Alternatively, the percent of reduction of landfills between the secondary mining and the demanufacturing process is 69.9%. The amounts of landfills produced in the three scenarios are shown in Fig. 5.8. Moreover, by this system we are reducing the emissions and keeping the air clean by which we are protecting public health. Therefore, by applying the product take-back system; many of the basic needs of society are satisfied by which we pursue the inter- and intra-generational equity. Demanufac turing Secondary 3.0E+08 Amount 2.0E+08 (lb.) 1.0E+08 0.0E+00 Primary Waste Sent to the Landfill Fig. 5.8: The Amount of Landfills in the Three Scenarios. 117 CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS 6.1. Research Results The product take-back system is a valuable approach towards industrial sustainability, when it is implemented with regards to the environmental, economic and social dimensions of sustainability. It can be speculated that the product take-back system is a paradigm that is needed in our society; since by reusing components, the demand for natural resources is reduced resulting in an efficient use of such resources and improvement in waste management. By this scheme, we could attain a sustainable economy that would not surpass the constraining limits of the ecosystem. Moreover, we could offer “sufficient good for the greatest number”. An analysis of the scenarios studied was presented in Chapter 3 and 4. The current scenario is based on the existing use of primary raw materials where the postconsumer product is either sent to landfills or secondary mined. However, the product take-back system conserves natural resources, either as materials recovery when the secondary mining scenario is applied, or as product embedded value recovery in the demanufacturing scenario where the reuse of components within the product is the main goal. The current system is linear, one that diminishes natural resources and degrades the environment. It produces a large amount of emissions that contribute to greenhouse gas effects and depletes the ozone. Producing one air conditioner generates 4,165,848.13 lbs. 118 of landfilled waste. Needless to say, the current system is not sustainable, i.e. it doesn’t obey the principle of “waste-equals-food”, on the contrary it moves against it. To achieve progression towards sustainability, alternative approaches must be studied and applied to replace the current system. Conversely, the secondary mining and the demanufacturing processes are scenarios for the product take-back system, which represent alternatives for the current industrial system. It gives the opportunity to recover higher value for the product. However, it requires changes in the design of the manufacturing process and the product, which results in a sustainable manufacturing process. As for the secondary mining, it is developed as a material recovery system where the product is shredded. The demanufacturing process is designed as a product embedded-value alternative. Because the demanufacturing process is less energy intensive than the other scenarios, it reduces pollutant emissions, landfills, and consumption of natural resources. It create jobs and recovers the embedded value of the post-consumer air conditioner. By applying this system, costs reductions are realized by i) avoiding waste treatment and disposal, and ii) reducing inputs of raw materials and energy, both of which result in a lower environmental impact. It should be emphasized at this point that the production and manufacture of materials into components are not included in the analysis of the primary and secondary mining process, which if added it would improve the efficiency of the demanufacturing scenario. The product take-back scenario is a near-zero waste scenario, the primary objective if industry is to achieve industrial sustainability, and accomplish massive improvements in the resource efficiency. In conclusion, the demanufacturing process 119 scenario ensures higher energy and materials savings when compared to the secondary mining scenario. Although some of the returned products are secondary mined under this new manufacturing concept, the overall performance when analyzed within the realm of sustainability is a major improvement over the current system. Therefore, based on the results of Chapter 4 and the discussion of Chapter 5, it can be concluded that the demanufacturing process is the most sustainable process among the three alternatives studied. It attempts to balance the three dimensions of sustainability. Economically, it reduces the depletion of natural resources and energy consumption. Socially, it creates jobs, provides quality goods at a reasonable price - hence a higher standard of living, and reduces the need for landfill space. And finally, environmentally, it reduces pollutant emissions. 6.2. Effect of the Disassembly Operation on Other Areas It can be argued that the main process in the demanufacturing scenario is the disassembly process. It is considered as the gateway of the parts for the remanufacturing process. Therefore, it impacts other areas in the production; e.g., inventory control, because of the uncertainty in the number and quality of the returned products. Nonetheless, the proposed system is based on a leasing program, where the manufacturer may lease the product for a predetermined (designed) time, which ensures that he will get it back to remanufacture and lease out again. Using this approach the manufacturer will be able to expect the number and quality of the ‘taken back’ products. On the other hand, there should be collaboration between the disassembly and reassembly operations to control inventory levels and prevent poor customer service. Production planning is 120 needed because of the hidden condition of the parts and the variation of the flow of the returned equipment. A recommendation that should be considered for this issue is employing a flexible workforce (part time labor). In addition, materials planning becomes necessary due to the variation in the quality of the part. However, the leasing program may solve some of these problems because the manufacturer having prepared parts reliability studies could calculate how long the product should be used. Thus he could forecast the probability of excellent, good, and bad quality of the ‘taken back’ products. At that point, he would be able to reduce the uncertainty in the materials planning. One of the main problems that might be faced is the supply and demand of the remanufactured products, which may keep the production line idle for some time and cause economic loss for the firm. Daniel et al. [R. and Jr. 2000]. conducted a survey that implied 75% of remanufactured products are not designed for disassembly, which results in higher disassembly time and more waste. Therefore, product design plays a significant role in making production sustainable, i.e., easier to disassemble; and as an approach for increasing the product take-back system efficiency. From the perspective of the analysis followed in this study, it is concluded that the more waste generated, the less the efficiency and vice versa. 6.3. Product Design This stage determines the efficiency of the life cycle of the product, even though it uses 5% of the time and resources of the manufacturing cost, it determines about 70% of the final product cost. All considerations should be taken into account as early as 121 possible, because design changes introduced later only add to the cost [Boothroyd, et al. 1994]. Therefore, resource requirements, environmental consequences and emissions of the product should be addressed in this critical phase. 6.3.1 Sustainable Product Design Maresa et al. [ 1999]. defined Sustainable Product Design as “the process which creates product designs that are sustainable in terms of the environment and resource-use whilst considering the need for the product.” Guidelines that are required in the design stage to attain sustainable products are as follows: 1. Materials choice by supply, where materials should be amply abundant (i.e. not scarce by considering the rates of use and sizes of reservoirs) and sufficiently available in the rock and soil near the surface of the earth [Graedel and Allenby 1995]. On the other hand, material choices are not only limited by supply, but also by toxicity levels. Selected materials should have very little toxicity properties. 2. Substitute hazardous with non-hazardous materials. 3. Resource-use efficiency in terms of materials and energy, by designing products that are lighter and more integrated. 4. Use renewable resources, i.e. materials and energy. 5. Sometimes, non-renewable materials should be used, designers could ensure to increase the life span of the product by designing for reuse, and recyclability. 6. Take into consideration the end life of the product where possible reuse and remanufacture may be applied, which requires disassembly (see section 6.3.2 for design for disassembly). 122 6.3.2 Design for Disassembly Disassembly is important and cannot be by-passed in remanufacturing, however, it is a non-value-added phase. To increase the efficiency of the demanufacturing process, products should be redesigned in order to simplify and accelerate disassembly. The longer it takes to disassemble a returned product, the higher the cost. Thus, reducing the time of disassembly and simplifying the process improves the remanufacturing feasibility. Guidelines that might be considered for design of disassembly are: · Avoid brute force techniques for disassembly to salvage sub-system components that are in good condition. · Design the product in order to allow technological upgrade. · Parts must be joined in a manner that makes separation easy. Permanent joining such as welding and crimping should not be used for remanufactured products, since it is either destructive disassembly or time consuming, e.g. using snap fits are suitable for disassembly. · It should be taken into consideration that the lifetime of the joints is the same as the whole product. Joints must be corrosion resistant, durable and reusable, and screw heads that can be easily damaged are not recommended. · Facilitate the accessibility to components. · Minimize the number of parts. · Minimize number of fasteners. · Leave surfaces available for tool grasping. · Provide easy access to inaccessible points. 123 · Minimization of product structure complexity by minimizing the number of parts. · Standardize and use fewer fastener types in order to use fewer tools in disassembly. One of the issues that should be considered in product design is standardization, to allow the manufacturer to make agreements to take-back each other’s products. This way a high percentage of inventory, production planning, etc. problems are solved. 6.4. · General Recommendations Consider internal reuse of scrap products instead of sending them to secondary mining. · Offer a like-new warranty (instead of repair) to the customer buying a new remanufactured product. The U.S. and Germany have high labor rates, which make products, and thus repair, more expensive. This offer is attractive to the consumer and a good option for the manufacturer since he insures that the returned product is reusable [Klausner and Grimm 1999]. · Convey an up-to-date image of the product. Some features might be added to the product, and the outer parts that determines the cognition of the product should be replaced. · Employ Total Quality Environmental Management (TQEM). Quality is equivalent to reducing the waste. Sustainability, which aims toward zero waste is then a quality concept that can be approached by TQEM. This practice facilitates the integration of sustainability and industrial ecology into the industrial production and manufacturing. The key to TQEM is not producing waste in the 124 first place; it is continually improving the environmental performance of the process. There are many tools of TQEM, e.g. Pareto Charts, Cause and Effect Diagrams, and Control Charts, can be used to identify the significant causes of the pollution problem, potential causes for the environmental problems in the process, and to determine the quantity of natural process variability respectively. Using such techniques the company might study the amount of solid waste, air emissions, and energy use. I would recommend the company might start with TQEM philosophy as a starting point to accomplish sustainability. · Investigate Reverse Logistics, a critical stage that is considered to be one of the main issues in a product take-back system. It involves the number and locations of the take-back centers and routes for transportation. Locklear [2000] developed a decision support model using geographic information systems (GIS) to design the reverse logistics of the product take-back process. In her research, she quantified the resulting effects of such a system and evaluated results taking the concept and dimensions of sustainability into account. 6.5. Future Work Issues in the product take-back system model require further research as follows: · One of the main assumptions in this research is stable production (static production line). This assumption might not be the case for many industrial manufacturing processes, since most of them are dynamic, so the results in this research might be expanded to a dynamic system rather than a stable one. 125 · The environmental impacts studied in this research were limited to the solid waste and air emissions, more research might be done to include water waste, noise, odor, etc. · The check in operation in the demanufacturing process classifies the taken back products either as remanufacturable or non-remanufacturable. More attention should be given to this operation, e.g. if the product classified as nonremanufacturable includes some reusable parts, and then full disassembly should not be performed. Efforts should be made to remove only the reusable parts, and the rest of the product should be sent directly to the secondary mining stream. This way, there will be a reduction in the disassembly time, energy consumed and its environmental impact, and thus disassembly cost. Therefore, product design plays a major role in this perspective, where attention should be given during the design stage for this issue. One of the applicable recommendations in this perspective is checking the product at the residential site, when the technician can test it when he un-installs the old product and affixes a description sticker about the product’s status. · Research should be done with regard to the number of times the product can be reused, and the materials can be ‘downcycled’. This may help in two aspects: it will help during the check in process, where a code bar that shows the number the time the product has been remanufactured, or its materials ‘downcycled’ to make the decision to which stream it would flow. Moreover, the other issue is that this study might give the manufacturer a broader image of the system and determines if it is feasible and cost-effective. 126 · As discussed before (section 4.3) research has been done for the cleaning operation in the demanufacturing process, which ensures a promising environmental and economic results, further research is needed in this area in collaboration with the Chemical Engineering department. · The demanufacturing process that includes check-in, disassembly, cleaning, inspection and sorting is only a partial creation of a product take-back system. Research should be done for the remanufacturing process which may include reconditioning, reassembly, testing and packaging and compare it to the manufacture of the raw materials and the product to complete the entire take-back system and combine the results of both studies. 6.6. Conclusion Finally, I would suggest that industry should work by operating in a cyclical manner and moving foreword not just into materials recovery but also into a value-added recovery that recaptures most of the embedded value that entered a product during its initial manufacture. As shown in this research, when comparing the current system with the demanufacturing process of a product take-back system, movement towards a zero waste system and sustainability is achieved. It was shown that the product take-back model reduced the need of ever more raw material inputs, saved energy consumption, contributed in comparison a minor environmental impact since it reduces discharges of pollutant air emissions (e.g. CO2, NOX, and SO2), and greater social consequences since it reduces amount of lanfilling and creating jobs. Consequently, the product take-back system predicts as shown in Table 4.39 an average cost of $12.84 per one unit in the 127 demanufacturing using power tools which is a gain of $96.76 or 88.35% less than the current manufacturing process. Ultimately, by product take-back system the overall resource demand and environmental impact would be diminished and industrial practice would move toward industrial sustainability. 128 REFERENCES Anderson, R. C. (1998). Mid-Course Correction. Atlanta, Georgia, The Peregrinzilla Press. Anderson, R. C. (1999). “The NEXT Industrial Revolution.” Georgia Tech Alumni Magazine: 20-28. ASHRAE (1995). ASHRAE Handbook: Heating, Ventilating, and Air-Conditioning Applications. Atlanta, GA, ASHRAE. Avallone, E. and T. Baumeister III, Eds. (1996). Marks' Standard Handbook for Mechanical Engineers. New York, New York, McGraw Hill. Ayres, R., G. Ferre, et al. (1997). “Eco-Efficiency, Asset Recovery and Remanufacturing.” European Management Journal. 15(5): 557-574. Ayres, R. U. and L. W. Ayres (1998). Accounting for Resources, 1. Cheltenham, Uk. Northampton, MA, USA, Edward Elgar. Bok, E., D. Kelch, et al. (1992). “Supercritical Fluids for single wafer cleaning.” Solid State Technolgy.: 117-120. Boothroyd, G., P. Dewhurst, et al. (1994). Product Design for Manufacture and Assembly. New York, New York., Marcel Dekker, Inc. Braungart, M. and J. Engelfried (1992). “An "Intelligent Product System" to replace "Waste Management".” Fresenius Envir Bull. 1: 613-619. CARB (1994). Combustion Pollutants in your Home, California Air Resources Board. <http://www.arb.ca.gov/research/indoor/combustf.htm> (Nov 01, 2000). Chertow, M. R. (1998). “Waste, Industrial ecology, and sustainability.” Social Research 65(1): 31-53. Daly, H. (1996). Beyond Growth: The Economics of Sustainable Development. Boston, Massachusetts., Beacon Press. Davis, J. (1996). Product Stewardship and the Coming Age of Takeback. Arlington, MA, Cutter Information Corp. DOE (2000). Greenhouse Gases, Global Climate Change, and Energy, U. S. Department of Energy. <http://www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html.> (Nov,09, 2000) 129 Dowie, T. and P. Kelly (1994). Estimation of disassembly times. Manchester, UK., Machester Metroplitan University. EDF (2000). Find out about your electricity, Environmental Defense. <http://www.environmentaldefense.org/programs/Energy/green_power/x_calculator.html> (Oct. 3, 2000). EPA (1998). 1997 National Air Quality: Status and Trends, U.S. EPA Office of Air & Radiation. <htp://www.epa.gov/oar/aqtrnd97/brochure/so2.html.>(Nov, 03, 2000). EPA (1998). Six Principal Pollutants - Nitrogen Dioxide (NO2), U.S. EPA Office of Air & Radiation. <ttp://www.epa.gov/oar/aqtrnd97/brochure/no2.html.>ct. 20, 2000). EPA (2000). , United States Environmental Protection Agency. <ttp://www.epa.gov/.>(Aug. 22, 2000). EPA (2000). Criteria Pollutants, United States Environmental Protection Agency. <http://www.epa.gov/globalwarming/emissions/national/crit-pol.html.> (Aug.13, 2000). EPA (2000). Extended Producer Responsibility. <http://www.epa.gov/epaoswer/non-hw/reduce/epr/abtover.htm.> (sep, 09, 2000). EPA (2000). Global Warming Potentials., United States Environmnetal Protection Agency. <http://www.epa.gov/globalwarming/emissions/national/gwp.html.> (Nov. 01, 2000). Fenton, M. (1997). Iron and Steel Scrap, U.S. Geological Survey (USGS): 1-18. <http://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel_scrap/360497.pdf.> Ferenc, J. (June 1994). Rheem's recycling program is hot stuff. Contractor 41(6): 5. Fishbein, B. (1998). EPR: What Does It Mean? Where Is It Headed? P2: Pollution Prevention Review 8: 43-55. Foy, G. (1990). “Economic Sustainability and the Preservation of Environmental Assets.” Environmental Management 14(6): 771-778. Frosch, R. A. (1992). Industrial Ecology: A Philosophical introduction. Proceedings of the National Academy of Sciences 89. Fu, H., M. Matthews , et al. (1998). “Recycling steel from grinding swarf.” Waste Management. WM 394: 1-9. Goodland, R. (1995). “The concept of environmental sustainability.” Annual Review of ecology and Systematics 26: 1-24. 130 Graedel, T. E. and B. R. Allenby (1995). Industrial Ecology. Englewood Cliffs, New Jersey, Prentice Hall. Grainger (1996). Industrial and Commercial Equipment and Supplies. Hawken, P. (1993). The Ecology of Commerce. New York, HarperCollins Publishers, Inc. Hileman, B. (1998). “Industrial ecology making an impact.” C&EN: 41-42. Interface (1997). Sustainability Report. ISRI (2000). Recycling Nonferrous Scrap Metals, Institue of Scrap Recycling Industries, Inc: 1-9. ISRI (2000). Recycling Scrap Iron an Steel. United States., Institue of Scrap Recycling Industries, Inc. Klausner, M. and W. Grimm (1999). “Integrating product takeback and technical service.” IEEE 8: 48-53. Lindhqvist, T. (1993). Europe's Move toward Extended Producer Responsibility: Experience in Germany, the Netherlands and Scandinavia. The Greening of Durable Products: What's the Best Route - Public Policy vs. Private Initiative, Massachusetts Institute of Technology. Locklear, B. (2000). A Decision Support System for the Reverse Logistics of Product Take-Back Using Geographic Information Systems and the Concepts of Sustainability. School of the Environment. Columbia, South Carolina, University of South Carolina. Lund, R. (1984). “Remanufacturing.” Technology Review 87(2): 19-29. Lund, R. (1998). Remanufacturing: and American resource. Proceedings of the fifth International Congress Environmentally Conscious Design and Manufacturing., Rochester Institute of Technology, Rochester, NY. Masera, D. (1999). “Sustainable product development: a key factor for small enterprise development - the case of furniture production in the Purepecha region, Mexico.” The journal of sustainable product development.: 28-29. Mathews, M. (2000). Supercritical Carbon Dioxide. University of South Carolina. Personal Communication. Motague, P. (1998). “Sustainable Development.” Rachel's Environment and Health Weekly.(624). NCR (1999). Life-Cycle Analysis and Costing in an Environmentally Conscious Manufacturing Environment, The National Center Remanufacturing. <http://www.reman.rit.educ/> , (Aug, 12,1999). NREL (2000). The Environmental Externality Costs of Petroleum. " National Renewable Energy Laboratory. http://rredc.nrel.gov/biomass/doe/rbep/ethanol/seven.html." (Sep. 05, 2000). 131 Odom, L. (2000). The Sustainable Systems Analysis Algorithm (SSAA):A Sustainable Design and Development Valuation Methodology. Department of Mechanical Engineering. Columbia, South Carolina, University Of South Carolina. R., V. d. and G. Jr. (2000). “Production planning and control for remanufacturing: industry practice and research needs.” Journal of Operations Management. 18: 467-483. Richards, D., B. Allenby, et al. (1994). The greening of industrial ecosystems. Washington DC, National Academy of Engineering. Richardson, K. (1999). Recycling Cost Rates. Mid Carolina Steel and Recycling. Personal Contact. Ruston, J. (1995). Advantage Recycle: Assessing the Full Costs and Benefits of Curbside Recycling, Environmental Defense.<http://www.environmentaldefense.org/pubs/Reports/advrec.html#table1.> (July 11, 2000) Shearman, Richard. (1990) The Meaning and Ethics of Sustainability. Environmental Management 14 (1) 1-8. Spaal, W. and K. Laintz (1995). A Survey on the Use of Supercritical Carbon Dioxide as a Cleaning Solvent. Supercritical Fluid Cleaning. Park Ridge, NJ, Noyes Publications. Steinhilper, R. and U. Hudelmaier (1993). Erfolgreiches Produktrecycling zur erneuten Verwendung oder Verwertung: Ein Leitfaden fur Unternehmen. Eschborn, Germany, Rationalisierungs Kuratorium der Deutschen Wirtschaft. Tibbs, H. B. C. (1991). Industrial Ecology: An Environmental Agenda for Industry., Arthur D. Little, Inc. Vanegas, J. (1997). Sustainable Design and Construction Strategies for the Built Environment. Building Energy: Ensuring a Sustainable Future. WCED (1987). Our common future. World Commission on Environment and Development. Oxford, Oxford University Press. William McDonough, M. B. (1998). “The NEXT Industrial Revolution.” The Atlantic Monthly: 82-92. Young, P., G. Byrne , et al. (1997). “Manufacturing and the Enviornmnet.” The international Journal of Advanced Manufacturing Technology 13: 488-493. Zovanyi, G. (1998). Growth Management for a Sustainable Future. Westport, Connecticut, London, PRAEGER. 132 APPENDIX A-Derivation of Energy Related Air Emissions 133 Calculations of obtaining Equations (7), (8), and (9). CO 2 = 3.72 ´ 10 -4 ´ E NO X = 1.22 ´ 10 SO 2 = 2.56 ´ 10 -6 -6 (7) (8) (9) ´E ´E 1. From the query of environmental defense [Defense, 1999 #29]. some data for the energy consumed and its related emissions were gathered as shown in table 1. Electricity Electricity CO2 NOx SOx (kWh) (kJ) (lb.) (lb.) (lb.) 1,598 5,752,800 2,140 7 15 3,196 11,505,600 4,279 14 30 15,979 57,524,400 21,396 70 148 159,787 575,233,200 213,959 704 1,475 119,840 431,424,000 160,469 528 1,106 Table A.1 : Data Gathered for Energy Consumption and its Emissions. 2. A Linear line was drawn as shown in Fig. 1, 2, and 3 and the best linear equations of the data given were obtained. 134 Amount of CO2 in Lbs Carbon Dioxide y = 3.72E-04x R2 = 1.00E+00 300,000 200,000 100,000 0 0.0000E 2.0000E 4.0000E 6.0000E 8.0000E +00 +08 +08 +08 +08 Energy Consumption in KJ Fig. A.1: Relation of CO2 Emissions and Energy Consumption. Amount of NOx in Lbs Nitrogen oxides y = 1.22E-06x R2 = 1.00E+00 800 600 400 200 0 0 2E+08 4E+08 6E+08 8E+08 Energy Consumption in KJ Fig. A.2: Relation of NOx Emissions and Energy Consumption. Amount of SO2 in Lbs Sulfur Dioxide y = 2.56E-06x R2 = 1.00E+00 2000 1500 1000 500 0 0 2E+08 4E+08 6E+08 8E+08 Energy Consumption in KJ Fig. A.3: Relation of SOx Emissions and Energy Consumption. 135 APPENDIX B-Transformation of CO into CO2 Emissions Calculations. 136 CO will react with Oxygen according to the following chemical reaction CO + ½ O2 ® CO2 The molecular weight of CO is 12 + 16 = 28 The molecular weight of CO2 is 12 + 2*16 = 44 The equation that will transform CO into CO2 equivalent is as follows: CO2 equivalent = CO amount * 44/28 137 APPENDIX C- Calculations of CO2 Emissions of ‘De-brazing’ Operation 138 Calculations of CO2 emissions from the combustion of Propane in the ‘De-brazing’ operation C3H8 + 5O2 « 4H2O + 3CO2 The molecular weight of CO2 = 44 Da. The molecular weight of C3H8 =36 Da. Then, 1 C3H8 « 3 CO2 The percent of the C with respect to propane is = 3*12/44 = 81.8% Assume that Propane torch produces 5,000 Btu/hr [Crainger,1996]., Heat value of propane per pound is 21,591 Btu The rate of propane combustion = 5,000/21,591 = 0.232 lb./hr As calculated before the percent of C in propane is 81.8% Then, The rate of carbon combustion = 81.8% ´ 0.232 = 0.89 lb./hour But, The percent of C with respect to CO2 = 12/44 = 27.3% The rate of CO2 combustion = 0.189/0.273 = 0.692 CO2 lb./hr = 0.0115 CO2 lb./min 139 Well, in the disassembly process the torch is used for 21 minutes per one air conditioner CO2 emissions in the disassembly process of one air conditioner= 0.0115 ´ 21 = 0.2422 lb. CO2 In our case 100,116 air conditioners are returned and disassembled, Total CO2 emissions from the ‘de-brazing’ operation = 0.2422 ´ 100,116 = 24,248.1 lb. CO2 140