Grease Cars

another interesting fact from eco-energy crowd:

you can use old vegetable oil to run a diesel powered car. yet another opportunity to turn the waste products of industry into economically useful energy sources. a restaurant giving it away for free cuts costs because they normally have to pay someone to haul it away as trash. the person who takes it saves money in fuel costs and helps minimize the damage that our car culture does to the environment.

i am betting that the economies of scale in densely populated cities with lots of restuarants would make it possible to support a business that specializes in collecting and refining the oil for re-sale.