I took some time to compare the two most common biofuels pound-for-pound, just to check if what we are promoting to supplant fossil fuels, is in fact logical. Here is a excerpt from the paper entitled "Environmental, Economic, And Energetic Costs And Benefits Of Biodiesel And Ethanol Biofuels" from the University of Minnesota.

*Ethanol yields 25% more energy than the energy invested in its production, biodiesel yields 93% more energy than the energy invested in its production.

*Compared with ethanol, biodiesel releases just 1.0%, 8.3%, and 13% of the agricultural nitrogen, phosphorus, and pesticide pollutants, respectively, per net energy gain.

*Relative to the fossil fuels biofuels displace, greenhouse gas emissions are reduced 12% by the production and combustion of ethanol and 41% by biodiesel.

*Biodiesel releases less air pollutants per net energy gain than ethanol.

*Biodiesel is produced form lower agricultural inputs and more efficient feedstock to fuel conversion.

*Neither biofuel can replace much petroleum without impacting food supplies (this statement must assume that other factors remain ceteris paribus or not-changing).

*If the US devotes all of its corn and soybean to biofuel production, it would meet 12%of US gasoline demand and 6% of US diesel demand.

I hope that puts things in perspective.

Study conducted by Messer Jason Hill, Erik Nelson, David Tilman, Stephen Polasky and Douglas Tiffany