ARB Research Seminar

This page updated July 25, 2013

Greenhouse Gas Emissions from Fuel Ethanol: Separating the Confusion from the Uncertainties

Photo of Alex Farrell, Ph.D.

Alex Farrell, Ph. D., Energy Resources Group, University of California, Berkeley

May 16, 2006
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA



Resource depletion, energy security and climate change imperatives will require a large-scale substitution away from conventional petroleum over the next several decades, as well as improved vehicle efficiency. In California, these imperatives led to Executive Orders S-3-05 and S-06-06 setting statewide targets for greenhouse gas (GHG) reductions and biofuel use, respectively. At the national level, the Energy Policy Act of 2005 aims to double the use of renewable transportation fuels. However, the energy and environmental implications of biofuels are hotly debated and the literature contains studies with conflicting results. Comparing across published studies to evaluate how these assumptions affect outcomes is difficult owing to the use of different units and different system boundaries across studies. Finding intuitive and meaningful replacements for net energy as a performance metric would advance our ability to evaluate how to meet these pressing imperatives.

To better understand the energy and environmental implications of ethanol and to investigate better performance metrics, we surveyed the published and gray literature and compared six studies illustrating the range of assumptions and data found for the case of corn-based ethanol. To permit a direct and meaningful comparison of the data and assumptions across the studies, we developed the Energy and Resources Group (ERG) Biofuel Analysis Meta-Model (EBAMM). This talk will discuss the analysis we performed with EBAMM and the implications of the results for both future research and public policy.

A paper reporting some of these results, as well as the EBAMM model with all of the data are available online at

Speaker Biography

Alex Farrell, Ph.D., is an Assistant Professor in the Energy and Resources group at the University of California Berkeley, and a research affiliate of the Institute of Transportation Studies, the Global Metropolitan Studies Initiative, and the Science, Technology, and Society Center at UC Berkeley. He is also an Investigator and Executive Committee member of the Climate Decision Making Center at Carnegie Melon University. He holds a B.S. in Systems Engineering from the U.S. Naval Academy and a Ph.D. in Energy Management and Policy from the University of Pennsylvania. Prof. Farrell's research focuses on improving our understanding of the environmental and social aspects of energy systems, and in the development of energy systems that support the world we desire to live in.

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