but the amount of (for example) corn needed to meet the US's energy needs would cover to much space, and would require a decrease or even deletion in the amount of farms producing crops to feed our bellies rather than our cars etc.
shafting these fields off to 3rd world countries is just as bad an option. besides if you have a country suffering from starvation, how are you going to justify the massive growth of crops so as to fuel our material needs rather than to provide them a basic standard of living, that which we all take for granted.
and hydrogen is a bad option as it requires more energy to be put into it than it puts out.
or so im taught at the evil institution of university.