I don't think there are any benefits in this case. But suppose that it really was reducing our dependence on foreign oil and in the process helping defund terrorist supporting states. That would certainly be a goal I could get behind and would support government intervention in the market place to help happen.
If Biofuel was likely to be viable alternative to oil given economies of scale and this program was helping achieve those economies of scale, then again I could support the government intervention. Especially if it meant American jobs vs overseas jobs during a time of high unemployment.
But I think there are better alternatives that have already been proven viable like Nuclear, that I'd rather see the government put it's resources behind. I just think the Biofuel, is not going to be viable unless you go to it 100% like Brazil and even then it's very questionable.
If Bio was viable why would you need subsidies to get it going? You would not. But if you consider Bio to be good then the fact that the free market wont make it or buy it is considered a failure.
I will take a free people buying and selling as they see fit over having your preferences imposed on me by government diktat.