Re:How many calories can we grow? (Score 0)

Well, the unique thing about biodiesel is that you don't actually need to use fresh crops; you can actually use waste vegeteble oil:

As of 2000, the United States was producing in excess of 11 billion liters of waste vegetable oil annually, mainly from industrial deep fryers in potato processing plants, snack food factories and fast food restaurants. If all those 11 billion liters could be collected and used to replace the energetically equivalent amount of petroleum (a rather utopian case), almost 1% of US oil consumption could be offset.[citation needed] However, usage of waste vegetable oil as a fuel competes with already established usages.

- http://en.wikipedia.org/wiki/Waste_vegetable_oil#W aste_vegetable_oil