Submitted on October 17, 2007
Accepted on January 28, 2008

Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land Use Change

¹ Woodrow Wilson School, Princeton University, Princeton, NJ, USA. German Marshall Fund of the U.S., Georgetown Environmental Law and Policy Institute.
² Agricultural Conservation Economics, Laurel, MD, USA.
³ Woods Hole Research Center, Falmouth, MA, USA.
⁴ Center for Agricultural and Rural Development, Iowa State University, Ames, IA, USA.

^* To whom correspondence should be addressed.
Timothy Searchinger , E-mail: tsearchi{at}princeton.edu

Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. Using a worldwide agricultural model to estimate emissions from land use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products.