Reading a 3 volume series called "Alternative Energy". In Volume 1, the use of biofuels is defended (p. 63):

Bioenergy is less polluting than fossil fuel-produced energy in respect to carbon dioxide. Biofuels contain carbon that only recently was in the Earth's atmosphere, so the carbon dioxide released through burning them does not add to the total carbon dioxide in the air. Fossil fuels, however, contain carbon that was removed from the atmosphere millions of years ago, and they emit large amounts of extra carbon dioxide when they burn. Replacing some fossil fuels with biofuels may help ease global warming, lessen air polution, and clear the world's air.

Schlager, N., Weisblatt, J. (Eds). Alternative Energy: Volume 1. U-X-L: Detroit, 2006.