Three Birds with One Stone...
Reduce Dependance on imported oil. Create more demand for farmed goods. Use a potentially hazzardous waste for fuel.
My father is a crop farmer and he is subsidized every year by the fedral government to plant, not plant, or just given money in general.
If we had more support for bio diesel, you could fill up those dirty desiels with cleaner (not zero emmisions mind you) burning bio diesel. At the same time we could push up the price farmers get paid for their crops and possibly reduce the subsidies they recieve from the governement.
BioDiesel does have a pit fall. It gels at a higher temprature than petro diesel. You can get around that buy making blends of the two.
There is a catch on older diesel cars. many of the rubber parts need to be replaced so the biodiesel doesn't eat through them. Probably a good idea on an older car anyway though.
I was almost ready to buy a VW Golf TDI, but VW said that using US version of BioDiesel in it would void the warranty.
Well here's hopeing Big Oil doesn't try to bury yet another potential competitor.