|Ogle, Stephen - Colorad0 State University|
|Mccarl, Bruce - Texas A&m University|
|Baker, Justin - Rti International, Usa|
|Del Grosso, Stephen - Steve|
|Paustian, Keith - Colorad0 State University|
|Parton, William - Colorad0 State University|
Submitted to: Mitigation and Adaptation Strategies for Global Change
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2015
Publication Date: 3/21/2015
Citation: Ogle, S.M., McCarl, B.A., Baker, J., Del Grosso, S.J., Adler, P.R., Paustian, K., Parton, W.J. 2015. Managing the nitrogen cycle to reduce greenhouse gas emissions from crop production and biofuel expansion. Mitigation and Adaptation Strategies for Global Change. DOI 10.1007/s11027-015-9645-0.
Interpretive Summary: Although nitrous oxide is the largest source of greenhouse gas emissions from production of bioenergy feedstocks, the current US Renewable Fuel Standards does not incorporate nitrogen management options. Using models to predict nitrous oxide emissions and forecast feedstock production and land management patterns, we evaluated alternative nitrogen management scenarios. We found that nitrous oxide emissions could be reduced by 5-10% depending on the crop and nitrogen management strategy used. These results demonstrate that by incorporating nitrogen management alternatives into the US Renewable Fuel Standards, there is potential to reduce nitrous oxide emissions from biofuel feedstock production.
Technical Abstract: The United States Renewable Fuel Standards (RFS2) established under the Energy Independence and Security Act of 2007 requires greenhouse gas (GHG) emissions to be lower for biofuels relative to fossil fuel combustion. However, there is an extensive debate in the literature about the potential to reduce GHG emissions with biofuels relative to equivalent emissions from fossil fuel combustion. One of the key sources of GHG emissions from biofuel feedstock production is soil nitrous oxide (N2O), which is largely driven by nitrogen (N) management. However, current the RFS2 does not incorporate options associated with N management. Our objective was to determine how much GHG emissions from biofuel feedstock production could be reduced by encouraging alternative N management practices. We estimated soil N2O emissions using the DayCent ecosystem model, and applied the U.S. Forest and Agricultural Sector Optimization Model with Greenhouse Gases (FASOMGHG) to forecast feedstock production, land management patterns and GHG emissions. The N management options included application of nitrification inhibitors and a cap on N fertilizer application to reduce the amount of fertilization. We evaluated the N management options under RFS2 scenarios with high amounts of corn ethanol as the primary feedstock, which is the current situation, and RFS2 with high amounts of cellulosic-based feedstocks, i.e., use of crop residues and switchgrass to produce ethanol. Relative to the current RSF2 with no N management, results show decreases in N2O emissions ranging from 3-4% (5.5-6.5 million tonnes CO2 eq yr-1) in response to a cap that reduces N fertilizer application, and even larger reductions with application of nitrification inhibitors, ranging from 9-10% (15.5-16.6 million tonnes CO2 eq yr-1). The results demonstrate that there is potential to reduce N2O emissions from biofuel feedstock production by incorporating N management alternatives into the US Renewable Fuel Standards.