Ethanol More Energy Efficient Than Thought, Study Says

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The enhanced use of biomass for transportation fuel would address several societal needs, scientists say.

"Two concerns drive the world's energy scene right now," said Steven Koonin, chief scientist for British Petroleum in London, England. "One is security of supply, primarily oil and gas. The second is concerns over [carbon dioxide] emissions and effects they could have on the climate system."

"Ideally, one would like to find technologies that address both problems," said Koonin, who wrote an accompanying editorial in Science. "For transportation, biofuels are perhaps uniquely suited to do that … with plausible evolutions of technology."

Studies show that with such technology developments, biofuels could supply some 30 percent of global fuel demand in an environmentally responsible manner, according to Koonin.

Boosting Performance

At least two previous ethanol studies concluded that the production of ethanol required more energy, including petroleum energy, than the energy stored in the ethanol.

But Farrell and his colleagues found that those previous studies were flawed. They used outdated information on production methods and failed to account for the many energy benefits of ethanol byproducts, including things like animal feed.

By correcting for those factors, the scientists found that corn ethanol actually reduces petroleum use by about 95 percent per gallon of fuel, though it only reduces greenhouse gas emissions by about 13 percent.

"These claims that ethanol is no good, period, do not stand up," Farrell said.

Many things can and should be done to boost ethanol's environmental performance, he says, including improving agricultural practices that require fewer energy inputs, such as less use of tractors, and lessen environmental impacts like soil erosion.

However, large-scale use of ethanol for fuel will almost certainly require so-called cellulosic technology, Farrell says. This involves applying new chemical techniques to break down and convert the raw material of a biofuel resource.

In the future, ethanol may be derived from energy crops, which require a lot less energy than food crops to cultivate. (Energy crops are plants cultivated not for food but for environmentally friendly fuels.)

"The big advantage then is that you don't have to grow food to make ethanol," Farrell said. "You can grow willow trees or you can grow prairie grass to make ethanol."

Driving Habits

Scientists say greater ethanol use would not significantly change our current vehicles or the way we buy fuel.

"The average driver in some U.S. states already uses [2 percent] ethanol in the gasoline he buys," Farrell said.

"Our study suggests that in the future, consumers may have a better chance not only to buy ethanol domestically, but to buy ethanol that is better for the environment than the ethanol that we buy today."

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