Biodiesel is an eco-friendly fuel that can be made from animal fats, algae, or from recycled vegetable oils like those used by restaurants to cook up French fries and other greasy goodies. Clean, veggie-based, and carbon-neutral, this fuel can usually run in any diesel car or truck with little or no modification to the engine.
Biodiesel burns cleaner than fossil fuel diesel, expelling fewer aromatic hydrocarbons and less soot and carbon monoxide. Because the carbon dioxide released by biodiesel is the same kind absorbed by the plant (or animal) source from where the fuel came, biodiesel is called a carbon neutral fuel. Unfortunately, biodiesel releases more nitrous oxide than regular diesel, a factor in smog. In 2005, the U.S. produced around 75 million gallons of this alternative fuel and in 2006, 65 companies reported having biodiesel plants under construction.