Geoengineering potential of enhanced dissolution of olivine on land

Geoengineering potential of enhanced dissolution of olivine on land

Geoengineering potential of enhanced dissolution of
olivine on land and in the open ocean
P. Köhler1 , J. Hartmann2 , J.F. Abrams1 ,
C. Völker1 , D. A. Wolf-Gladrow1
1: Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
2: Institute for Biogeochemistry and Marine Chemistry, KlimaCampus, University of
Hamburg, Germany
slides revised 25th July 2012
Peter Köhler
1
London, 27/03/2012
Geoengineering
Geoengineering schemes
SRM: Solar radiation managemant techniques
CDR: Carbon dioxide removal techniques
(Royal Society 2009)
Peter Köhler
2
London, 27/03/2012
Geoengineering
CDR act via the Global Carbon Cycle
Enhance Weathering by 10×: from < 0.2 Pg C yr−1 to > 1 Pg C yr−1
(IPCC 2007)
Peter Köhler
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London, 27/03/2012
Geoengineering
Summary on selected geoengineering techniques
Enhanced weathering is considered effective & safe, slow & difficult to
afford. No numbers on CO2 sequestration available in 2009.
(Royal Society 2009)
Peter Köhler
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London, 27/03/2012
Chemistry of olivine weathering
Olivine
Olivine is:
a silicate (Si) containing mineral (Mg2 SiO4 ).
found in dunite, one of the major constituents of the Earth’s upper
mantle and accessible at the Earth’s surface.
highly dissolvable compared to other silicate minerals.
dissolves within 1-2 yr if grinded to 10–30 µm.
Peter Köhler
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London, 27/03/2012
Chemistry of olivine weathering
Silicate (olivine) Weathering
Weathering includes input of HCO−
3 into the ocean (+DIC, +alkalinity).
All C in silicate weathering is derived from the atmosphere.
(Ruddiman 2001)
Peter Köhler
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London, 27/03/2012
Chemistry of olivine weathering
Olivine Dissolution on Land
Mg2 SiO4 + 4 CO2 + 4H2 O ⇒ 2 Mg2+ + 4 HCO−
3 + H4 SiO4
olivine + carbonic acid ⇒ cations + bicarbonate + silicic acid
1.4
theoretical limit
1.3
0.35
1.2
1.1
0.3
1.0
pCO2 = 385 atm
pCO2 = 700 atm
0.9
0.8
0
1
2
3
4
0.25
5
6
7
8
9
C : Olivine [Pg:Pg]
CO2 : Olivine [Pg:Pg]
Theoretical limit: 1 mol olivine sequesters 4 mol CO2
similar to 1 t olivine sequesters 1.25 t CO2 (0.34 t C)
Realization: about 20% smaller depending in detail on chemistry
because carbonate system is changed due to HCO−
3 input
10
Sequestered CO2 [ atm]
Peter Köhler
(after Köhler et al., 2010, PNAS)
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London, 27/03/2012
Estimating global potential
Global Potential of Olivine Dissolution on Land
Limitation: Saturation concentration of silicic acid (H4 SiO4 ) limits the
CO2 sequestration in the humid tropics to about
1 Pg C yr−1 = 1015 g C yr−1 = 0.5 µatm CO2 yr−1 .
Effort: Distribute and dissolve 100–300 g m−2 yr−1 of olivine
over large areas in the humid tropics (logistic challenge!).
In total dissolve about 3 Pg olivine per year.
Costs: 70 e to 150 e per t C sequestered.
20 − 50× todays EU’s CO2 emissions right.
Risks: River pH will rise significantly.
Health risk of small particles unclear.
Dissolution of heavy metals possible.
Efficiency: Energy consumption for mining, grinding and
transportation reduces sequestration efficiency by ∼10%.
(after Köhler et al., 2010, PNAS)
Peter Köhler
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London, 27/03/2012
Estimating global potential
Terrestrial versus marine dissolution of olivine
∆(pCO2 )
Zoom-in: years 2010-2060
∆(pH)
0.03
3Pg olivine/yr@land
3Pg olivine/yr@ocean
-10
0.02
-20
0.01
-30
2010
theoretical limit 3Pg olivine/yr
2020
2030
2040
2050
2060 2010
Time [yr AD]
2020
2030
2040
2050
(pH) [-]
(pCO2) [ atm]
0
0.0
2060
Time [yr AD]
Difference land / ocean:
Ocean dissolution: CO2 NOT from atmosphere, but from marine pools
Ocean: higher effect on pH (against ocean acidification)
3 Pg olivine / yr = 150 Pg olivine in 50 yr:
pCO2 : less than −20 µatm
A2 emission: +220 µatm
pH: less than +0.02
A2 emission: −0.15
Simulations with carbon cycle boxmodel BICYCLE (after Köhler et al., 2010, PNAS)
Peter Köhler
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London, 27/03/2012
Estimating global potential
Marine Biology — REcoM-2 (open ocean dissolution)
3 Pg olivine dissolution per year
0.9
0.3
0.8
0.25
0.7
0.6
S1 (silicic acid+alkalinity input) 0.2
S2 (only silicic acid input)
0.15
S3 (only alkalinity input)
0.5
0.4
0.1
0.3
0.2
0.05
0.1
0.0
2000
2002
2004
2006
2008
0.0
2010
-1
1.0
normalized (Pg C yr per Pg olivine)
-1
changes oceanic CO2 uptake (Pg C yr )
Simulations with the marine ecosystem model REcoM-2
embedded in ocean general circulation model MITgcm
Time (yr)
Silicic acid input changes biology, increases CO2 uptake by 8%.
(Abrams et al., submitted)
Peter Köhler
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London, 27/03/2012
Estimating global potential
Marine Biology — REcoM-2 (open ocean dissolution)
1.0
0.8
2
0.6
0.4
1
0.2
0
0.0
-0.2
-1
-0.4
-0.6
-2
total NPP
-3
2000
2002
diatoms: NPP + 14%,
non-diatoms: NPP −4%,
total NPP +2%,
Peter Köhler
diatom NPP
non-diatom NPP
2004
2006
Time (yr)
11
2008
-0.8
-1.0
2010
-1
3 Pg olivine dissolution per year
-1
changes in C fluxes (Pg C yr )
3
normalized (Pg C yr per Pg olivine)
Silicic acid input in REcoM-2 @ MITgcm (Abrams et al., submitted)
Olivine dissolution of 1 Pg equals natural Si input through rivers!
from 16.6 to 19.0 Pg C yr−1
from 33.6 to 32.3 Pg C yr−1
from 50.2 to 51.3 Pg C yr−1
London, 27/03/2012
Estimating global potential
Marine Biology — REcoM-2 (open ocean dissolution)
REcoM-2 @ MITgcm (Abrams et al., submitted)
Even distribution of olivine, whole ocean, all year (upper limit)
Non-diatom NPP: −4%
Diatom NPP: + 14%
Red: increase, Blue: decrease
Peter Köhler
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London, 27/03/2012
Estimating global potential
Marine Biology — REcoM-2 (open ocean dissolution)
REcoM-2 @ MITgcm (Abrams et al., submitted)
Even distribution of olivine, whole ocean, all year (upper limit)
export production : +1% Relative changes (%) CaCO3 export: −5%
Red: increase, Blue: decrease
Peter Köhler
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London, 27/03/2012
Estimating global potential
Global Potential of Open Ocean Olivine Dissolution
Effort: For a distribution of 3 Pg olivine per year (to sequester
1 Pg C yr−1 ) it needs the full-time commitment of more
than 300 large ships with net tonnage of 300,000 t.
Pragmatic approach: Dissolution of olivine in ballast waters of
existing global fleet of cargo ships. This is again limited
by the saturation concentration of silicic acid (H4 SiO4 )
and therefore restricted to the distribution 0.7 Pg of olivine
per year (sequestering 0.2 Pg C yr−1 ).
Dissolution kinetics: Grinding to grains of 1 µm necessary to avoid
sinking of undissolved olivine. Aggregation might lead to
larger sinking velocities.
Risks: Impact on marine biology. Potential for extension of
anoxic or suboxic region.
Peter Köhler
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London, 27/03/2012
Conclusions
Conclusions of Olivine Dissolution
1
Enhanced olivine dissolution is ocean fertilization.
2
Bottleneck is the saturation concentration of silicic acid H2 SiO4 .
3
Land potential: 3 Pg yr−1 of olivine sequester 1 Pg C yr−1 .
4
The same sequestration rate can be achieved in open ocean with
the year-round use of 300 large ships.
5
Dissolution in ballast water of commencial ships has the potential
to sequester 0.2 Pg C yr−1 .
6
Range of present day coal production (6 Pg coal in 2009).
Peter Köhler
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London, 27/03/2012
Conclusions
References
Abrams, J. F.; Völker, C.; Köhler, P.; Hauck, J. & Wolf-Gladrow, D. A.
submitted. Geoengineering impact of open ocean dissolution of
olivine on the global carbon cycle and marine biology. Global
Biogeochemical Cycles.
IPCC 2007. Climate Change 2007: The Physical Science.
Contribution of Working Group I to the Fourth Assessment
Report of the Intergovernmental Panel on Climate Change,
Editors: S. Solomon and D. Qin and M. Manning and Z. Chen
and M. Marquis and K. B. Averyt and M. Tignor and H. L. Miller,
Cambridge University Press.
Köhler, P.; Hartmann, J. & Wolf-Gladrow, D. A. 2010. Geoengineering
potential of artificially enhanced silicate weathering of olivine.
Proceedings of the National Academy of Science, 107,
20228-20233.
The Royal Society 2009. Geoengineering the climate: science, governance
and uncertainty. www.royalsoc.ac.uk.
Ruddiman, W. F. 2001. Earth’s Climate, past and future. Freeman.
Peter Köhler
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London, 27/03/2012