Dr Timothy Searchinger and colleagues showed that use of croplands for Biofuels increases Greenhouse Gases through emissions from land-use change (2008): “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. By 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.” [1].