Corn to fuel is a poor gain, but other crops do better. Brazil is almost completely self sufficient on fuel because of bio-fuel. Sugar cane and other s work better.
I do agree there should be no subsidies. Make a mandate that so many cars/filling stations/whatever have to be produced. If you create a market and demand it will sustain itself. Fine the snot out of the oil companies with record profits to force them to come up with renewable clean fuels.