. . . it's energy diversity. Right now, we're dependent on one source for fuel: oil. As such, we're totally vulnerable to its risks and shortcomings. Replace it with ethanol, we'd STILL be vulnerable, just to a different set of risks and shortcomings. You can replace ethanol with any other proposed alterna-fuel and come up with the same conclusion.

EVERY source of energy has its risks and limitations. The solution isn't picking one ideal source to research and subsidize, but how to bring as many of them online as possible, with as great an efficiency as possible, to limit our exposure to the different sets of risks.