UPDATE 1-Food-based biofuels can spur climate change-study

(Adds industry reaction, letter to Bush, paragraphs 3, 12-15)

By Deborah Zabarenko, Environment Correspondent

WASHINGTON, Feb 7 (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 U.S. 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.