Corn ethanol is not looking as promising as it once was. Corn ethanol requires a lot of corn fields, and these produce carbon emissions. So even if the corn ethanol is better on the environment, the production of it is not. Dedicating fields toward corn for fuel also takes away necessary space for crops that will be consumed. Lastly, it's now believed that corn ethanol can potentially be damaging to car engines. So, as it stands now, it does not appear that corn ethanol is a superior fuel.
Corn ethanol will eventually start encroaching on the world food supply. Because if a farmer would receive more money for producing their corn for the corn ethanol versus a low end profit of corn production for human and livestock consumption. The farmer will choose to produce for the making of the corn ethanol for bigger profit. Not to mention waste greases or oils from fast food restaurants would be better alternative since the waste oils can be converted into other uses than just disposed of. Making a batch of used frying grease a reuseable resource more than a one and done solution.