A study published in "Science" has found that increasing the use of ethanol will actually INCREASE global warming. The study, from researchers at Princeton and Iowa State University, found that ethanol production from corn could double the amount of green house emissions. The reason for this is that plowing up the land will release much of the carbon formerly stored in plants and soils through decomposition or fires. The researchers state that the previous studies on ethanol were "one-sided" because they only counted the carbon benefits of using land for biofuels but not the carbon costs of diverting land from its existing uses.
This is why nuclear, solar and wind are the way to go.