Life Cycle Assessment of the Energy Independence and Security Act of 2007: Ethanol—Global Warming Potential and Environmental Emissions

Strategies to reduce the dependence of the United States on foreign oil, increase the use of renewable energy, and lessen the contribution to global warming have received significant attention. National adoption of such strategies could significantly impact America’s economy and security as well as global climate change. The Energy Independence and Security Act of 2007 (EISA) mandates specific renewable energy market penetration targets for the year 2022 [1]. For liquid transportation fuels, the 2022 EISA mandate is 36 billion gallons per year (bgy) of biofuel, of which 21 bgy must come from feedstocks other than corn starch. Despite this legal mandate for renewable biofuels, many questions remain unanswered with regard to the potential environmental effects of such a large increase in the production and use of biofuels. In addition to specifying volumetric standards for these renewable fuels, EISA establishes greenhouse gas mitigation standards. The objective of this study is to use life cycle assessment (LCA) to evaluate the global warming potential (GWP), water use, and net energy value (NEV) associated with the EISA-mandated 16 bgy cellulosic biofuels target, which is assumed in this study to be met by cellulosic-based ethanol, and the EISA-mandated 15 bgy conventional corn ethanol target. Specifically, this study compares, on a per-kilometer-driven basis, the GWP, water use, and NEV for the year 2022 for several biomass feedstocks.