Investigating technologies and practices that accelerate natural processes to remove carbon from the atmosphere and store it in solid forms (soil carbon, biochar, and carbonate mineralization) that are stable over time scales of hundreds, if not thousands of years.
Learn more in BEI concept paper, “Advancing Agriculture’s Role in Carbon Dioxide Removal and Reliable Sequestration” (PDF).
Soil carbon management
Agricultural land use can both increase and decrease carbon in soils. The emerging question is how to balance carbon storage and farmers’ profitability. We are addressing this challenge with a well-calibrated, comprehensive farming systems model that considers short- and long-time scales and the multiple factors involved in soil carbon dynamics to predict and explain complex interactions between soil-crop processes and climate patterns in soil carbon. Crop options being evaluated include corn and soybean as well as strategically expanding rotations and perennializing land cover through cover crops, small grains, sorghum, alfalfa, miscanthus, switchgrass, and prairie. Our perspective on removing carbon is that quantifying the results will lead to economic incentives, thus developing an approach that motivates adoption.
Biochar incorporation into agricultural lands
Biochar is produced by thermally decomposing biomass in a low or zero oxygen atmosphere, a process known as pyrolysis, which also produces bio-oil and flammable gas. While the bio-oil and gas can be used in energy applications the biochar has potential for carbon removal from the atmosphere. Biochar resists microbial degradation in soils and hence sequesters carbon in agricultural lands for hundreds or even thousands of years. Iowa State is a leader in biochar research and now seeks to launch pilot-scale pyrolyzers and biochar cropping models to assess agronomic and environmental impacts of biochar applications. Producer partnerships will help secure the field-scale data needed to recommend and build the infrastructure for large-scale implementation.
Microbial carbonate precipitation (MCP) in soils
Microbial carbonate precipitation occurs in nature when water and carbon dioxide react with calcium silicate minerals to form calcium and bicarbonate ions. These ions are subsequently converted by microbial action into a precipitate of calcium carbonate (limestone), which can be stable over millennia. We propose to identify the biogeochemical processes in soils that result in microbial carbonate precipitation, and to develop practical methods of enhancing this natural process of carbon removal from the atmosphere.
Microbial carbonate precipitation (MCP) in anaerobic digestion
Anaerobic digestion (AD) is a natural process in which organic matter is decomposed by a consortium of microbes in the absence of oxygen. By capturing methane, AD reduces greenhouse gas emissions associated with decomposing organic matter from manure lagoons or landfills. Separating CO2 from biogas and sequestering it represents a promising agriculturally based CDRRS strategy. We propose the direct capture of CO2 during AD to produce a solid that is more amenable to long-term storage. While typically achieved by adding silicate minerals to AD, we propose ash-rich biochar for this purpose, which also buffers pH and absorbs ammonia, improving AD performance. Although still in its infancy, we recently launched a research program that can help move this concept to wide-spread practice.