Ethanol can be produced from a lot of stuff that is simply wasted right now. Things such as corn/rice stalks and straw that currently yield nothing and are a waste product can be used to make an obscene amount of ethanol. Not to mention there are plants out there with higher yields by corn at a level of many multiples that just aren't being used yet. If the system is optimized and farmers work on efficiency by using those waste products for ethanol production as well, it could definitely be a viable fuel source, maybe not for 100% of the market share, but a significant enough portion to help stem the gasoline demand.