University of Minnesota, Twin Cities: Global Warming
Converting pristine lands to biofuel farms worsens global warming - 02/07/08
Yet that's what happens when native ecosystems are converted into "farms" for biofuel crops, according to a study by the University of Minnesota and the Nature Conservancy published online today in Science. The researchers document how the act of turning rainforests, peatlands, savannas, or grasslands into biofuel-yielding croplands emits large amounts of carbon that add to the atmosphere's already heavy burden of greenhouse gases.
In places like Brazil, Southeast Asia, and the United States, land is being planted with corn or sugarcane to produce ethanol, or with palm trees or soybeans to produce biodiesel. The carbon, stored in the original plants and soil, is released as carbon dioxide when that organic matter decays, which can go on for 50 years or longer.
The land conversions pump out 17 to 423 times more carbon than the annual savings from replacing fossil fuels with the biofuels. This constitutes a "carbon debt" that the biofuels produced on the land must pay off before they can begin to have the effect of cutting greenhouse gas emissions.
In the worst case the researchers examined, converting peatlands in Indonesia into palm oil plantations ran up a carbon debt that would take 423 years to pay off.
The next worst was soybeans in the Amazon, which wouldn't "pay for themselves" in renewable soy biodiesel for 319 years. The conversion of U.S. grasslands for corn ethanol and Indonesian rainforests for palm biodiesel also ran up big carbon debts.
"The research examines the conversion of land for biofuels and asks the , 'Is it worth it?,'" says lead author Joe Fargione, a scientist for the Nature Conservancy.
