A Life-Cycle Analysis of the Greenhouse Gas Emissions from Corn-Based Ethanol

This report has analyzed the current GHG profile of U.S. corn ethanol and two projected emissions profiles for 2022. The starting point is the GHG life-cycle analysis (LCA) done by the U.S. Environmental Protection Agency (EPA) in 2010 for U.S. corn ethanol as part of its Regulatory Impact Analysis (RIA) for the Revised Renewable Fuel Standard (RFS2). In the RIA, EPA projected that in 2022, the life cycle emissions associated with ethanol would be 21 percent lower than those of an energy equivalent quantity of gasoline.

We assessed each of the 11 emissions categories in the 2010 EPA LCA in light of new data, technical papers, research studies and other information that have become available since 2010. Aggregated across the 11 categories, we found U.S. corn ethanol is developing along an emissions pathway significantly lower than what EPA projected in 2010. Our analysis indicates the current GHG profile of U.S. corn ethanol is, on average, 39 percent lower than gasoline. For natural gas powered refineries, this value is almost 43 percent lower. Finally, current trends in the ethanol industry and actions refineries could take to reduce emissions offer opportunities to lower the GHG profile of corn ethanol between 47.0 and 70.0 percent relative to gasoline.

This analysis is timely because many countries (e.g., Colombia, Japan, Brazil, Canada and the European Union) are now developing or revising their renewable energy policies. These policies typically require biofuel substitutes for gasoline to reduce GHG emissions by more than 21 percent. Our results could help position U.S. corn ethanol to compete in these new and growing markets.