We could use other sources to produce more ethanol. But we produce a heck of a lot more corn than we do sugar and we can't import sugar efficiently because of trade barriers. Everything from corn stalks to switchgrass can be used for celluloisic ethanol, but I think the technology for making that conversion is lagging.

And lets not forget, the same government that is making the CRP payment is also paying the subsidies/providing tax credits that make producers think about not enrolling in CRP. Seems sort of counter-productive, doesn't it? If they didn't cause the run-up in corn prices, they could make cheaper CRP payments to eligible producers. Instead they pay on both ends.