FALL/WINTER 2005-06 — Systems Assessment
Argonne Expert Addresses Energy and Environmental Impacts of Fuel Ethanol
The energy benefits of fuel ethanol result from reduced fossil energy and petroleum use during production and the absence of fossil and petroleum in the final product.
Although the United States used 3.4 billion gallons of fuel ethanol for blending with gasoline in transportation fuels in 2004 — virtually all of it produced from corn — the energy and environmental effects of using corn-based ethanol have nonetheless been questioned. A few researchers maintain that corn-based ethanol has a negative energy balance (which means that more fossil energy is required to produce ethanol than the amount of energy in the produced ethanol) and results in increased greenhouse gas (GHG) emissions relative to petroleum-based gasoline.
Since 1997, CTR researchers have been studying the energy and GHG emission impacts of fuel ethanol as part of their overall efforts to evaluate the well-to-wheels energy and emission effects of various advanced vehicle technologies and transportation fuels. They use the Greenhouse gases, Regulated Emissions and Energy use in Transportation (GREET) model, developed by CTR researcher Michael Wang. This peer-reviewed model employs the most current and accurate data to conduct life-cycle analysis for more than 100 vehicle-fuel pathways.
The results of Argonne's ethanol analysis — like those of many other recently completed ethanol studies — reveal that corn-based ethanol achieves energy and GHG emission-reduction benefits relative to gasoline. In fact, Wang and his colleagues concluded that corn ethanol requires 26% less fossil energy because it contains "free" solar energy that ends up in the corn. The fuels energy and environmental benefits accrue primarily because of:
- Improved productivity by U.S. corn farmers in the past 30 years,
- Reduced energy use in ethanol plants over the past 15 years, and
- Appropriate treatment of ethanol co-products in the analysis.
Wang, who is a leading worldwide expert in this field, presented the overall results of his research at the Ethanol Energy Open Forum, sponsored by the National Corn Growers Association, at the National Press Club in Washington, D.C., on August 23, 2005.
Conclusions from Wang's presentation include the following:
- Energy balance value alone is not meaningful in evaluating the benefit of ethanol or any other energy product. For proper evaluation, a product's energy use must be compared with that of the product it replaces.
- Compared with gasoline, any type of fuel ethanol helps to substantially reduce fossil energy and petroleum use.
- Ethanol produced from corn can achieve moderate reductions in GHG emissions.
- Ethanol produced from "cellulosic" plants (such as grass and trees) offers even greater energy and GHG emission-reduction benefits than does corn-based ethanol. In fact, cellulosic-biomass–based ethanol reduces fossil energy use by 90%. GREET also showed that cellulosic ethanol offers an 85% reduction in GHG emissions on a per-gallon basis.
The consensus of analyses by Wang and many researchers supports the premise that corn ethanol can supply some of our motor fuel needs now, and cellulosic ethanol can provide a greater portion in the future. Currently, 88 ethanol plants operate in the United States, and 16 more are being built. Approximately 50–70 new plants are anticipated to open by 2012, according to industry observers.
The growth in ethanol use is being aided by energy legislation recently adopted in the United States that will require fuel ethanol use of 7.5 billion gallons annually by 2012. The legislation contains provisions to encourage production of cellulosic ethanol.
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U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Office of Planning, Budget, and Analysis (PBA) and Biomass Program
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