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Technical, economical, and climate-related aspects of biochar production technologies: a literature review.

Author(s): Meyer S, Glaser B, Quicker P

Published: November, 2011

Publisher: Environmental science & technology

DOI: 10.1021/es201792c

Tags: Biochar, Economics

URL: http://pubs.acs.org/doi/abs/10.1021/es201792c

Abstract: For the development of commercial biochar projects, reliable data on biochar production technologies is needed. For this purpose, peer-reviewed scientific articles on carbonization technologies (pyrolysis, gasification, hydrothermal carbonization, and flash carbonization) have been analyzed. Valuable information is provided by papers on pyrolysis processes, less information is available on gasification processes, and few papers about hydrothermal and flash carbonization technologies were identified. A wide range of data on the costs of char production (between 51 US$ per tonne pyrolysis biochar from yard waste and 386 US$ per tonne retort charcoal) and on the GHG balance of biochar systems (between −1054 kg CO2e and +123 kg CO2e per t dry biomass feedstock) have been published. More data from pilot projects are needed to improve the evaluation of biochar production technologies. Additional research on the influence of biochar application on surface albedo, atmospheric soot concentration, and yield responses is necessary to assess the entire climate impact of biochar systems. Above all, further field trials on the ability of different technologies to produce chars for agricultural soils and carbon sequestration are essential for future technology evaluation.


Legitimate conditions for climate engineering

Author(s): Owen R

Published: October, 2011

Publisher: Environmental science & technology

DOI: 10.1021/es2033185

Tags: Ethics, Governance

URL: http://pubs.acs.org/doi/full/10.1021/es2033185

Abstract: On September 13th scientists announced preparations were underway for the first UK field trial of climate engineering feasibility. The proposed trial will be modest: it will pump water through a 1 km high balloon-tethered hose, to assess the feasibility of reflective particle injection high into the atmosphere, mimicking the temperature-reducing effects of volcanic eruptions. But it has stimulated considerable debate about whether research in this controversial field should be undertaken at all, and if so the conditions under which it is acceptable to proceed. Responding, the President of the UK’s Royal Society, Paul Nurse, replied that there should be research on both the efficacy and safety of geoengineering: “One would not take a medicine that had not been rigorously tested to make sure that it worked and was safe. But, if there was a risk of disease, one would research possible treatments and, once the effects were established, one would take the medicine if needed and appropriate. Similarly we need controlled testing of any technologies that might be used in the future”. His comments, and specifically this analogy to pharmaceuticals, raise important questions concerning the conditions under which we decide to deploy controversial technologies such as solar radiation management.


CO2 Mitigation via Capture and Chemical Conversion in Seawater

Author(s): Rau GH

Published: February, 2011

Publisher: Environmental Science & Technology

DOI: 10.1021/es102671x

Tags: Enhanced Weathering, Ocean Alkalinity Enhancement

URL: http://pubs.acs.org/doi/abs/10.1021/es102671x

Abstract: A lab-scale seawater/mineral carbonate gas scrubber was found to remove up to 97% of CO2 in a simulated flue gas stream at ambient temperature and pressure, with a large fraction of this carbon ultimately converted to dissolved calcium bicarbonate. After full equilibration with air, up to 85% of the captured carbon was retained in solution, that is, it did not degas or precipitate. Thus, above-ground CO2 hydration and mineral carbonate scrubbing may provide a relatively simple point-source CO2 capture and storage scheme at coastal locations. Such low-tech CO2 mitigation could be especially relevant for retrofitting to existing power plants and for deployment in the developing world, the primary source of future CO2 emissions. Addition of the resulting alkaline solution to the ocean may benefit marine ecosystems that are currently threatened by acidification, while also allowing the utilization of the vast potential of the sea to safely sequester anthropogenic carbon. This approach in essence hastens Nature’s own very effective but slow CO2 mitigation process; carbonate mineral weathering is a major consumer of excess atmospheric CO2 and ocean acidity on geologic times scales.


Life cycle assessment of biochar systems: estimating the energetic, economic, and climate change potential

Author(s): Roberts KG, Gloy BA, Joseph S, Scott NR, Lehmann J

Published: December, 2009

Publisher: Environmental Science & Technology

DOI: 10.1021/es902266r

Tags: Biochar, Economics

URL: http://pubs.acs.org/doi/abs/10.1021/es902266r

Abstract: Biomass pyrolysis with biochar returned to soil is a possible strategy for climate change mitigation and reducing fossil fuel consumption. Pyrolysis with biochar applied to soils results in four coproducts: long-term carbon (C) sequestration from stable C in the biochar, renewable energy generation, biochar as a soil amendment, and biomass waste management. Life cycle assessment was used to estimate the energy and climate change impacts and the economics of biochar systems. The feedstocks analyzed represent agricultural residues (corn stover), yard waste, and switchgrass energy crops. The net energy of the system is greatest with switchgrass (4899 MJ t−1 dry feedstock). The net greenhouse gas (GHG) emissions for both stover and yard waste are negative, at −864 and −885 kg CO2 equivalent (CO2e) emissions reductions per tonne dry feedstock, respectively. Of these total reductions, 62−66% are realized from C sequestration in the biochar. The switchgrass biochar-pyrolysis system can be a net GHG emitter (+36 kg CO2e t−1 dry feedstock), depending on the accounting method for indirect land-use change impacts. The economic viability of the pyrolysis-biochar system is largely dependent on the costs of feedstock production, pyrolysis, and the value of C offsets. Biomass sources that have a need for waste management such as yard waste have the highest potential for economic profitability (+$69 t−1 dry feedstock when CO2e emission reductions are valued at $80 t−1 CO2e). The transportation distance for feedstock creates a significant hurdle to the economic profitability of biochar-pyrolysis systems. Biochar may at present only deliver climate change mitigation benefits and be financially viable as a distributed system using waste biomass.


Crop residues: the rest of the story

Author(s): Karlen D, Lal R, Follett R, Kimble J, Hatfield J, Miranowski J, Cambardella C, Manale A, Anex R, Rice C

Published: September, 2009

Publisher: Environmental Science & Technology

DOI: 10.1021/es9011004

Tags: Marine Carbon Storage

URL: http://pubs.acs.org/doi/abs/10.1021/es9011004

Abstract: Sinking agricultural botanical and soil residues to the deep seafloor may not be a viable option for long-term carbon sequestration.


Assessment of Near-Future Policy Instruments for Oceangoing Shipping: Impact on Atmospheric Aerosol Burdens and the Earth’s Radiation Budget

Author(s): Lauer A, Eyring V, Corbett JJ, Wang C, Winebrake JJ

Published: July, 2009

Publisher: Environmental Science & Technology

DOI: 10.1021/es900922h

Tags: Air Pollution, Tropospheric Aerosols, Climate Science, Climate Modelling

URL: http://pubs.acs.org/doi/abs/10.1021/es900922h

Abstract: We apply the global climate model ECHAM5/MESSy1-MADE with detailed aerosol and cloud microphysics to study the impact of shipping on tropospheric aerosol burdens, clouds, and the radiation budget for four near-future ship emission policy scenarios for the year 2012. We compare a “No Control” scenario with global sulfur limits and regionally applied reductions. We show that, if no control measures are taken, near surface sulfate increases by about 10−20% over the main transoceanic shipping routes from 2002 to 2012. A reduction of the maximum fuel sulfur (S) content allowed within 200 nautical miles of coastal areas (“global emission control areas”) to 0.5% or 0.1% (5000 or 1000 ppm S, respectively) results in a distinctive reduction in near surface sulfate from shipping in coastal regions compared with the year 2002. The model results also show that if emissions of nitrogen oxides (NOx) remain unabated, a reduction of the fuel sulfur content favors a strong increase in aerosol nitrate (NO3) which could counteract up to 20% of the decrease in sulfate mass achieved by sulfur emission reductions. The most important impact of shipping on the radiation budget is related to the modification of low maritime stratus clouds resulting in an increased reflectivity and enhanced shortwave cloud forcing. The direct aerosol effect from shipping is small. Our study shows that one can expect a less negative (less cooling) radiative forcing due to reductions in the current fuel sulfur content of ocean-going ships. The global annual average net cloud forcings due to shipping (year 2012) are in the range of −0.27 to −0.58 W/m2 with regional cooling occurring most over the remote oceans.


Regulating Geologic Sequestration in the United States: Early Rules Take Divergent Approaches

Author(s): Pollak MF, Wilson EJ

Published: May, 2009

Publisher: Environmental Science & Technology

DOI: 10.1021/es803094f

Tags: Law, Terrestrial Carbon Storage

URL: http://pubs.acs.org/doi/abs/10.1021/es803094f

Abstract: Differences between recent state and federal regulations highlight choices that must be made to create a regulatory framework for geologic sequestration in the United States.


Ocean sequestration of crop residue carbon: recycling fossil fuel carbon back to deep sediments

Author(s): Strand SE, Benford G

Published: January, 2009

Publisher: Environmental science & technology

DOI: 10.1021/es8015556

Tags: Marine Carbon Storage

URL: http://pubs.acs.org/doi/abs/10.1021/es8015556?prevSearch=Ocean%2Bsequestration%2Bof%2Bcrop%2Bresidue%2Bcarbon%253A%2Brecycling%2Bfossil%2Bfuel%2Bcarbon%2Bback%2Bto%2Bdeep%2Bsediments&searchHistoryKey=

Abstract: For significant impact any method to remove CO2 from the atmosphere must process large amounts of carbon efficiently, be repeatable, sequester carbon for thousands of years, be practical, economical and be implemented soon. The only method that meets these criteria is removal of crop residues and burial in the deep ocean. We show here that this method is 92% efficient in sequestration of crop residue carbon while cellulosic ethanol production is only 32% and soil sequestration is about 14% efficient. Deep ocean sequestration can potentially capture 15% of the current global CO2 annual increase, returning that carbon back to deep sediments, confining the carbon for millennia, while using existing capital infrastructure and technology. Because of these clear advantages, we recommend enhanced research into permanent sequestration of crop residues in the deep ocean.


Can wetland restoration cool the planet ?

Author(s): Pelley J

Published: December, 2008

Publisher: Environmental science & technology

DOI: 10.1021/es802790q

Tags: Land Use Management

URL: http://pubs.acs.org/doi/abs/10.1021/es802790q

Abstract: Wetlands are champions at carbon storage, but they also release methane, a greenhouse gas 20 times more potent than CO2. Scientists are boosting research efforts to determine whether the cooling power of carbon storage outstrips the global warming potential of methane in wetlands. They are finding that the greatest cooling occurs from saltwater marshes.


Electrochemical splitting of calcium carbonate to increase solution alkalinity: implications for mitigation of carbon dioxide and ocean acidity

Author(s): Rau GH

Published: December, 2008

Publisher: Environmental science & technology

DOI: 10.1021/es800366q

Tags: Ocean Alkalinity Enhancement

URL: http://pubs.acs.org/doi/abs/10.1021/es800366q

Abstract: Electrochemical splitting of calcium carbonate (e.g., as contained in limestone or other minerals) is explored as a means of forming dissolve hydroxides for absorbing, neutralizing, and storing carbon dioxide, and for restoring, preserving, or enhancing ocean calcification. While essentially insoluble in water, CaCO3 can be dissolved in the presence of the highly acidic anolyte of a water electrolysis cell. The resulting charged constituents, Ca2+ and CO32−, migrate to the cathode and anode, respectively, forming Ca(OH)2 on the one hand and H2CO3 (or H2O and CO2) on the other. By maintaining a pH between 6 and 9, subsequent hydroxide reactions with CO2 primarily produce dissolved calcium bicarbonate, Ca(HCO3)2aq. Thus, for each mole of CaCO3 split, there can be a net capture of up to 1 mol of CO2. Ca(HCO3)2aq is thus the carbon sequestrant that can be diluted and stored in the ocean, in natural or artificial surface water reservoirs, or underground. The theoretical work requirement for the reaction is 266 kJe per net mole CO2 consumed. Even with inefficiencies, a realized net energy expenditure lower than the preceding quantity appears possible considering energy recovery via oxidation of the H2 produced. The net process cost is estimated to be <$100/tonne CO2 mitigated. An experimental demonstration of the concept is presented, and further implementation issues are discussed.


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