Shocker, I know. Who would have expected Willie Nelson on this list. It’s not just that this tour bus belongs to a celebrity with a thing for the environment; the bus actually runs on a concoction called BioWillie, a Nelson-marketed biodiesel made from vegetable oil. Now that’s keeping it green. The police of course would convince you that the bus runs on another green substance, but that’s for Willie’s lawyers to worry about.

I can't help you convert a bus to run on soy beans, but I know you can buy a Chevrolet Suburban that runs on corn.