BTW, biodiesel is intriguing....and clean (more so than "normal diesel.)
It is until you start looking at the acreage required to supply the equivalent of 30 billion gallons of diesel per year. Even if biodiesel made up 2% of the total, it's tens of millions of acres.
Biodiesel isn't an end-all. I like the idea of making it from all the used cooking oil that needs treatment or disposal. Using fifty-jillion acres to make fuel isn't what I have in mind at all. It's more waste reduction.