How energy-positive is ethanol, really?

The Bush administration is more pro-ethanol than ever. In his latest state of the union address, President Bush called on Congress to "fund additional research in cutting-edge methods of producing ethanol, not just from corn, but from wood chips and stalks, or switch grass. Our goal is to make this new kind of ethanol practical and competitive within six years."

But can ethanol really offer the energy gains promised by the President? In July 2005 scientists David Pimentel and Tad W. Patzek published a controversial paper challenging the energy economics of ethanol and biodiesel. According to their research, the process of converting plants such as corn, soybeans, and sunflowers into fuel consumes much more energy than the resulting ethanol or biodiesel generates. Specifically, they said that corn requires 29% more fossil energy than the ethanol produced, for switch grass it's 45% more, and wood biomass requires 57% more fossil energy than the fuel produced.

Understandably, this research has been controversial, especially with ethanol supporters. The most recent return volley by researchers from UC Berkeley's Energy and Resources Group claims to find net energy benefits that Pimentel and Patzek overlooked. There's no easy answer to the ethanol economics debate, but it does pay to ask questions about it. When considering local sources of ethanol or biodiesel, crunch the numbers. The energy and environmental impacts of ethanol, and how they compare to those of gasoline, can vary substantially by region, feedstock (or petroleum source), and manufacturing process.

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