Monday, March 06, 2006

A core problem with ethanol

From the Rocky Mountain News:
If you look at the facts, the spending makes no sense whatsoever. Consider how ethanol is produced. Corn is grown, harvested, then delivered to an ethanol plant. There the corn is ground and mixed with water. After fermentation, a mixture that is about 8 percent ethanol must be repeatedly distilled until it is 99.5 percent pure ethanol. Growing and harvesting the corn, and heating and reheating the fermented corn to produce ethanol of a high enough quality to replace some of the gasoline in your car requires an enormous amount of energy.

How much? A recent study by Cornell University's David Pimentel and the University of California at Berkeley's Tad Patzek added up all the energy consumption that goes into ethanol production. They took account of the energy it takes to build and run tractors. They added in the energy embodied in the other inputs and irrigation. They parsed out how much is used at the ethanol plant. Putting it all together, they found that it takes 29 percent more energy to make ethanol from corn than is contained in the ethanol itself.

It's not that corn is a bad source for ethanol. The other sources mentioned by the president look even worse. Wood biomass takes 57 percent more energy to produce than it contains. Switch grass takes about 50 percent more. Ethanol is just a highly uneconomical product. Some other authors have disputed these findings, but they invariably come up with more favorable calculations by excluding some of the costs.

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