WASHINGTON (Reuters) - Alternative fuels made from corn, soybeans, sugar cane and palm trees can in some cases increase the amount of climate-warming carbon dioxide that goes into the atmosphere, U.S. researchers reported on Thursday.
These so-called food-based biofuels can actually hurt the environment if they are produced on land that was formerly grassland, rain forest or savanna, the scientists said in the journal Science.
Industry groups took issue with the findings, calling them simplistic and noting the use of environmentally sound techniques to cultivate biofuel crops. At the same time, academic environment experts wrote to President George W. Bush and congressional leaders calling for new policies to make sure biofuels do not come at a prohibitive ecological cost.
Nonfossil fuels -- ethanol made from corn or sugar cane and biodiesel made from palm trees or soybeans -- are meant to lessen dependence on petroleum products, which release the greenhouse gas carbon dioxide when they burn.
But biofuels can release carbon even before they are burned, depending on how they are made, said study co-author Jason Hill of the University of Minnesota.
As demand for these alternative fuels grows, farmers are plowing under forests and grasslands that used to store carbon and keep it from getting into the atmosphere, and using these lands to grow the food crops that now can be used for ethanol or biodiesel.
Biofuels grown this way come with a "carbon debt," the researchers found. Instead of cutting greenhouse pollution, the net effect is to increase it.
CENTURIES OF CARBON DEBT
For example, the scientists wrote, Indonesia's conversion of peatlands for palm oil plantations had the world's greatest carbon debt, one that would take 423 years to repay.
The next worst case was the planting of soybeans in the Amazon, which would not pay for itself in renewable soy biodiesel for 319 years.
There are biofuel sources that do not rack up these formidable carbon debts, Hill said, citing nonfood plants including perennial grasses that only have to be harvested, without plowing under existing species that hold on to carbon.
"Our group has looked at using diverse mixtures of native species ... (on) prairie land, land that's restored back into prairies," Hill said in a telephone interview. "We essentially have no native prairies left in this nation but we can restore land into prairies, thereby restoring an ecosystem that was natural and also getting the biofuel benefit from it."
Ten academic experts -- including Steve Hamburg of Brown University, David Wilcove of Princeton University and Stuart Chapin of the University of Alaska -- cited the study in a letter to Bush, House of Representatives Speaker Nancy Pelosi and other leaders on Capitol Hill.
"There is an urgent need for policy that ensures biofuels are not produced on productive forest, grassland or cropland," the said in the letter.
The Renewable Fuels Association, which represents the U.S. ethanol industry, called the study a "simplistic view of land use change," adding: "Biofuels alone are not the silver bullet to the energy or environmental challenges our planet faces. But they do offer a pathway forward."
The Biotechnology Industry Organization cited its own study that indicated farmers could produce enough feedstock for biofuels through environmentally sustainable no-till agriculture.
Biofuels, whether made from prairie plants, corn or soybeans, lack the potential to satisfy U.S. fuel needs, Hill said.
"If we take every corn kernel we produce in this nation and convert it to ethanol, we would offset only 12 percent of our gasoline use," he said. "And that doesn't include the energy it took to produce that ethanol in the first place.