Improvements in Life Cycle Energy Efficiency and Greenhouse Gas Emissions of Corn-Ethanol

Authors

Adam J. Liska, University of Nebraska - LincolnFollow
Haishun S. Yang, University of Nebraska - LincolnFollow
Virgil R. Bremer, University of Nebraska - LincolnFollow
Terry J. Klopfenstein, University of Nebraska - LincolnFollow
Daniel T. Walters, University of Nebraska - LincolnFollow
Galen Erickson, University of Nebraska - LincolnFollow
Kenneth G. Cassman, University of Nebraska - LincolnFollow

Date of this Version

1-21-2009

Comments

Published in Journal of Industrial Ecology (2009); doi 10.1111/j.1530-9290.2008.00105.x Copyright ©2009 Yale University; published by Wiley-Blackwell. Used by permission. Publisher's version available online @ http://www3.interscience.wiley.com/journal/121647166/abstract

Abstract

Abstract
Corn-ethanol production is expanding rapidly with the adoption of improved technologies to increase energy efficiency and profitability in crop production, ethanol conversion, and coproduct use. Life cycle assessment can evaluate the impact of these changes on environmental performance metrics. To this end, we analyzed the life cycles of corn-ethanol systems accounting for the majority of U.S. capacity to estimate greenhouse gas (GHG) emissions and energy efficiencies on the basis of updated values for crop management and yields, biorefinery operation, and coproduct utilization. Direct-effect GHG emissions were estimated to be equivalent to a 48% to 59% reduction compared to gasoline, a twofold to threefold greater reduction than reported in previous studies. Ethanolto- petroleum output/input ratios ranged from 10:1 to 13:1 but could be increased to 19:1 if farmers adopted high-yield progressive crop and soil management practices. An advanced closed-loop biorefinery with anaerobic digestion reduced GHG emissions by 67% and increased the net energy ratio to 2.2, from 1.5 to 1.8 for the most common systems. Such improved technologies have the potential to move corn-ethanol closer to the hypothetical performance of cellulosic biofuels. Likewise, the larger GHG reductions estimated in this study allow a greater buffer for inclusion of indirect-effect land-use change emissions while still meeting regulatory GHG reduction targets. These results suggest that corn-ethanol systems have substantially greater potential to mitigate GHG emissions and reduce dependence on imported petroleum for transportation fuels than reported previously.