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It’s Carbon Payback Time

July 22, 2008
A recent study from researchers at the University of Wisconsin takes another look at the “carbon debt” models proposed by Searchinger and Fargione in ScienceXpress earlier this year. Searchinger and Fargione argued that biofuel development in the United States and Europe would lead to the destruction of rainforests and grassland in Brazil and other tropical climates, which would of course release massive amounts of carbon into the atmosphere (See earlier posting).

The new study takes into account some factors that other researchers criticized Fargione and Searchinger for ignoring. Bringing crop yields in the developing world up to the production level in the United States would increase biofuels’ carbon recycling benefits by up to 50 percent, according to the study authors. Further, if biofuels displace future production of oil from tar sands, their climate benefit will increase by another 25 percent. The researchers conclude that “future carbon payback times could be substantially shorter with increases in crop yields, changing petroleum sources and improved biofuel technology."

Biofuels could have immediate benefits, the study authors conclude, if they are grown on degraded farm land. As another recent study from Stanford University shows, there are nearly 1 billion acres of abandoned farm land around the world. Some of this former agricultural land was once pasture grazed by cattle, and some was cropland that was abandoned for greener fields or because of changing needs. The study’s principle author calculates there is enough land in the United States to supply 9 percent of U.S. transportation energy, using current crop yield data.