The prospect of painlessly growing corn and sugar cane on spare land to reduce global warming always seemed too good to be true. And so it is, write Joseph Fargione of the Nature Conservancy and four coauthors from the University of Minnesota. Switching from oil to biofuels might actually make things worse.
The problem arises because plowing up large tracts of undisturbed land to plant biofuels could release vast amounts of carbon dioxide (CO2)—between 17 to 420 times more CO2—than the fossil fuels that are replaced.
New agricultural production generates a “carbon debt” by releasing long-sequestered CO2 into the atmosphere as land is cleared—often by burning—and plants decompose. If, as is done in Malaysia, peat soil is drained to make way for palm tree plantations (palm oil is a source of biodiesel), environmental damage becomes even more severe because peat releases great amounts of CO2 as it dries out. The “carbon debt” run up by growing corn on fallow midwestern grasslands to produce ethanol would take about 93 years to erase. The debt incurred by transforming tropical peatland into palm plantations would last for 840 years, Fargione and his coauthors estimate.
As America tries to wean itself from foreign oil, the newly enacted Energy Independence and Security Act mandates the use of more ethanol and other such products. Environmentally friendly biofuels might eventually be derived from perennial grasses and woody plants grown on degraded and abandoned agricultural lands that would remain unplowed. The byproducts of sustainable forestry and the stalks and leaves of corn and soybean plants are also promising sources of biofuels. (Other specialists note, however, that the needed processing technology is not fully developed.)
Biofuel crops could someday reduce reliance on oil from the unstable Middle East. But they also might have the disadvantage of raising grocery prices and shifting food crops to more ecologically vulnerable locales. The authors’ conclusions are clear: Biofuels are no panacea.
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The Source: "Land Clearing and the Biofuel Carbon Debt" by Joseph Fargione, Jason Hill, David Tilman, Stephen Polasky, and Peter Hawthorne, in Sciencexpress, February 7, 2008.
Photo courtesy of Flickr/Steven Jurvetson