This year, trucks and other heavy-duty motors in America will burn some 3 billion gallons of diesel fuel that's made primarily from vegetable oil. They're doing it, though, not because it's cheaper or better, but because they're required to, by law.
The law is the Renewable Fuel Standard, or RFS. For some, especially Midwestern farmers, it's the key to creating clean energy from American soil and sun. For others — like many economists — it's a wasteful misuse of resources.