Actually you can run a diesel engine on cooking oil. There was a news article several months ago about an arrest in the UK where an individual was running his auto on used cooking oil. Apparently his exhaust whiffed of fish & chips! He was suitably penalized for his conservation efforts by a fine for avoiding the road tax!

Biodiesel (made from soybean oil) in the US is growing rapidly and several huge ethanol plants are in operation and several more are under construction. Back when the price of oil was under $30 these renuable energy sources needed tax breaks to be competitive but with the current price of oil over $50 they have become economicaly viable. The byproducts ,'dried distillers grain', is used for livestock feed.