Submitted to: Elsevier
Publication Type: Book / Chapter
Publication Acceptance Date: 11/12/2011
Publication Date: 6/8/2012
Citation: Adler, P.R., Del Grosso, S.J., Inman, D., Jenkins, R.E., Spatari, S., Zhang, Y. 2012. Mitigation opportunities for life cycle greenhouse gas emissions during feedstock production across heterogeneous landscapes. In: Liebig, M., Franzluebbers, A.J., Follet, R.F., editors. Managing Agricultural Greenhouse Gasses: Coordinated agricultural research through GRACEnet to address our changing climate. New York, NY: Elsevier Inc. p. 203-219. DOI: 10.1016/B978-0-12-386897-8.00012-7. Interpretive Summary: Crop production can contribute more than 50% of the total carbon footprint of biofuels and due to management, soil texture, and weather, it can vary across the farming landscape. Through a combination of both review of scientific literature and new model analysis of greenhouse gas emission from soil, we identified 3 key farm operations, N fertilizer use, N2O emissions, and tillage impact on soil carbon, which have significant potential to reduce the carbon footprint of biofuels when best management practices are used. This analysis could help policy makers identify a strategy to reduce the carbon footprint of biofuels without increasing the regulatory burden on farmers.
Technical Abstract: Feedstock production can contribute greater than or equal to 50% of the lifecycle global warming intensity (GWI) of a biofuel. Variability exists within and among high-leverage components of the biomass production phase. GWI variability within feedstocks has gone unrecognized by regulatory agencies. We present results of a meta-analysis of select feedstock production life cycle assessment(LCAs). System levers with the most potential to reduce feedstock GWI are N fertilizer use, N2O emissions, and tillage practices. The median feedstock GWIs span an order of magnitude from 50 to 500 kg CO2e per Mg of feedstock produced. Uncertainty in the GWI of the various LCA components is a function of the methods used and the availability of input data required by the respective methods. Including entity-level measurements of the GWI of feedstock production could incentivize feedstock producers to use lower GWI practices. Results of this study are a starting point from which more rigorous and perhaps regionally specific data on key leverage points and production systems should be collected to help guide biomass producers toward minimizing the GWI of their particular biomass production system.