Less energy output by volume compared to petroleum, currently inefficient production means high ratio of energy put into producing biofuel versus energy yielded from fuel itself.
Ethanol from corn is a huge scam subsidized by the US government supported by congressmen from corn producing states.
Ethanol in current internal combustion engines lowers mileage (notice drop in mpg during winter? Higher ethanol content with winter formulation of gasoline)
Ethanol can damage parts of the fuel system when you get up to higher percentages than what is currently added to gas.
Besides, converting a food crop/ farm land to fuel when millions are going hungry is downright immoral.
