Ethanol Not So Green After All?

High gas prices, the threat of shrinking oil reserves, and global warming guilt are driving interest in ethanol, biodeisel, and other biofuels—energy sources produced from agricultural plant matter rather than fossil fuels such as oil and coal.

(Photo: Gas station charges "an arm and a leg.")

But can biofuels really replace petroleum products? And are they really better for the environment than fossil fuels?

Soybean-based biodiesel is more environmentally friendly than fossil fuels, a new study says.

Corn-grain ethanol, however—currently touted in a General Motors ad campaign titled "Live Green, Go Yellow"—is not.

"There are surprisingly large environmental impacts for corn-grain ethanol," said Jason Hill, a biologist with the University of Minnesota in St. Paul.

(Related: "Ethanol More Energy Efficient Than Thought, Study Says" [January 26, 2006].)

Hill is the lead author of the analysis reported today in the journal Proceedings of the National Academy of Sciences.

The study evaluated what Hill and colleagues call the three E's of biofuels—their environmental impact, the energy recovered from them, and their economic viability in the marketplace.

According to the analysis, significantly less fertilizer and pesticide are required to grow soybeans than corn.

In addition, soybean biodiesel produces 93 percent more energy than is expended in its creation. Corn-grain ethanol produces only 25 percent more.

And when compared with fossil fuels, biodiesel produces 41 percent less greenhouse gas emissions, while ethanol produces 12 percent fewer.