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Corn Ethanol Energy Sources

Energy is required to grow and harvest corn, to process it into ethanol, and to transport the product to market. Most of this energy at corn-to-ethanol facilities todaycomes from fossil fuels like coal, oil and natural gas. A 2006 paper in the journal Science carefully analyzed diverse earlier studies about the fossil fuel inputs for making corn ethanol. They found that only 5-26% of the energy content in corn-ethanol is renewable, meaning that it is not ultimately derived from fossil fuel.1  Also in 2006, Hill and colleagues published their own detailed analysis and found that about 25% of the energy in corn-ethanol is renewable.2

In 2007, Wang and colleagues updated the widely-cited GREET (Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation) model to reflect the latest understanding of the process used to create corn-based ethanol. They found that approximately 23% of the energy in corn-ethanol is renewable energy. Considering all of these analyses, an approximate value of 20% might be considered representative for today's corn ethanol industry.

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References
  1. Farrell, Alexander E., Richard J. Plevin, Brian T. Turner, Andrew D. Jones, Michael O'Hare, and Daniel M. Kammen. “Ethanol Can Contribute to Energy and Environmental Goals.” (PDF) Science 311, no. 5760 (January 27, 2006): 506-508.
  2. Hill, Jason, Erik Nelson, David Tilman, Stephen Polasky, and Douglas Tiffany. “Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels.” (PDF) Proceedings of the National Academy of Sciences 103, no. 30 (July 25, 2006): 11206-11210.