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 today comes 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.