Carbon Sequestration and Reduction of Greenhouse Gas Emissions with Biochar

Reduction of atmospheric carbon dioxide and other even more potent greenhouse gases are required to mitigate climate change. In addition to effective reduction of fossil fuel use, active withdrawal of carbon dioxide from the atmosphere appear unavoidable to reach targets for total radiative forcing. Multiple complementary approaches are needed. One such approach is the net withdrawal of carbon dioxide from the atmosphere by photosynthesis followed by pyrolysis of the biomass to transform easily decomposable organic matter into relatively recalcitrant biochar. The biochar can be added to soil where it improves soil functions such as nutrient retention and soil fertility. Over the short term, this will lead to a positive feedback on growth of vegetation and hence additional carbon withdrawal from the atmosphere. Abandoned mines are an appropriate target for such interventions as soil organic matter is typically low and reclamation efforts may be accelerated by adding biochar. Stability of biochar-carbon relies much less on mineral protection mechanisms such as aggregation or formation organo-mineral interactions, making it a suitable reclamation strategy for organic matter-poor soils. The economic feasibility may rely on revenues from the reclamation effort in combination with emission reductions by both the lower decomposition of biochar than biomass and lower gaseous losses of nitrous oxide within a carbon trading scheme. Fossil fuel offsets appear unlikely in remote regions and the actual carbon balance depends to a large extent on the biomass source.