WASHINGTON (AP) -- Ethanol is far from a cure-all for the nation's energy problems. It's not as environmentally friendly as some supporters claim and would supply only 12 percent of U.S. motoring fuel - even if every acre of corn were used.
As far as alternative fuels are concerned, biodiesel from soybeans is the better choice compared with corn-produced ethanol, University of Minnesota researchers concluded in an analysis Monday.
But "neither can replace much petroleum without impacting food supplies," the researchers concluded in the paper published in the Proceedings of the National Academy of Sciences.
The paper said development of nonfood materials such as switchgrass, prairie grasses and woody plants to produce cellulosic ethanol would be a major improvement with greater energy output and lower environmental impacts.
But creation of cellulosic ethanol remains in the laboratory research stage. And even nonfood sources of ethanol would fall far short of replacing gasoline, most researchers agree.
Biofuels such as ethanol are "not a practical long-term solution," and their widespread use - even from nonfood crop sources - could have a "devastating" impact on agriculture, two researchers at the Magleve Research Center of the Polytechnic University of New York, argued recently.
"Ethanol from 300 million acres of switchgrass still could not supply our present gasoline and diesel consumption, which is projected to double by 2025," the researchers, James Jordan and James Powell, wrote in an op-ed article in the Washington Post. "The agricultural effects of such a large-scale program would be devastating."
As a motor fuel, ethanol from corn produces a modest 25 percent more energy than is consumed - including from fossil fuels - in growing the corn, converting it into ethanol and shipping it for use in gasoline.
While often touted as a "green" environmentally friendly fuel, corn-based ethanol's life cycle environmental impacts are mixed as best, the researchers said.
Compared with gasoline, it produces 12 percent less "greenhouse" gasses linked to global warming, according to the study. But the researchers also said it has environmental drawbacks, including "markedly greater" releases of nitrogen, phosphorous and pesticides into waterways as runoff from corn fields. Ethanol, especially at higher concentrations in gasoline, also produce more smog-causing pollutants than gasoline per unit of energy burned, the researchers said.
"There's a lot of green in the money that's going into ethanol, but perhaps not so much green is coming out as far as the environment," said Hill, the lead author, in a telephone interview.