Cellulosic ethanol has been hailed as the next frontier in renewable fuels. After all, most ethanol in the U.S. comes from corn, a staple product in the food chain. Use more corn for ethanol, and you’re bound to drive up food prices. If you’ve seen “King Corn,” you know the score. Corn ethanol also has its problems with energy inputs versus energy outputs. In other words, the benefits can be sketchy.