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Tuesday, September 11, 2007

Environment - Alternative Energy Sources


Also from Vol. 170 of Science News:
Corn-grain ethanol and soybean biodiesel are the two major alternative transportation fuels in the United States.


Both biofuels yield energy, but with corn-based ehtanol, "it takes so much energy to grow the corn and convert it into a fuel, you don't gain very much energy in the overall process," says ecologist David Tilman at the University of Minnesota in St. Paul. While ethanol provides 25% more energy than it consumes, [...] soybean biodiesel (yields) 93% (more energy).


Per unit of energy, biodiesel requires 1% of the nitrogen, 8.3% of the phosphorus and 13% of the pesticides that corn ethanol does.
Moreover, producing and using corn ethanol decreases greenhouse gas emissions by 12% compared to gasoline. Soybean biodiesel produces 41% less greenhouse gas emissions than corn ethanol.

I'm waiting for them to move to switchgrass, which requires no pesticides or fertilizers and is expected to provide a larger energy gain than either of the other alternatives mentioned. According to the article, if the entire corn and soybean crop of the U.S. were used for fuel, it would only provide 12% of the gasoline and 6% of the fuel.

Apparently, Americans haven't yet heard that the first crucial step in recycling is reduce.

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