Here is an interesting summary of some biofuel:

http://www.energyfuturecoalition.org/biofuels/fact_ethanol.htm#4

Apparently it takes a gallon of oil to produce 12-20 gallons of ETOH. Since ethanol (ETOH) has 2/3 the energy of gasoline that becomes about 8-13 gallon-equivalents.

After distillation the leftovers are dried and used for cattle feed and apparently that drying uses a lot of the energy. The actual alcohol production uses much less.