My uncle owns like 10 tractors that he uses for construction. He was telling me that in 2009 (IIRC) he'll have to have most of his heavy equipment updated for new smog laws, if that's even feasible...he may have to just sell his old equipment for pennies on the dollar and buy new or maybe retire.
Anyway, FWIW, he was telling me that it takes more than a gallon of diesel to make a gallon of biodiesel.
Any idea if that's true?