Biodiesel is a fuel source based on vegetable oil or animal fat. Biodiesel is meant to be used in standard diesel engines and is thus distinct from the vegetable and waste oils used to fuel converted diesel engines. You can use biodiesel alone, or blended with petroleum diesel. When you use it in combination with petroleum diesel the mixture usually contains 20% biodiesel and 80% petroleum diesel (also known as B20). The mixture can be used on standard diesel engines. Pure biodiesel, known as B100, may require certain engine modifications.
Since the passage of the Energy Policy Act of 2005 biodiesel use has been increasing in the US. In Europe, the Renewable Transport Fuel Obligation obliges suppliers to include 5% renewable fuel in all transport fuel sort in the EU by 2010.
Next to the use of biodiesel in car engines, it is used to fuel railway trains, like the Virgin Voyager train, and aircrafts, although in an experimental phase. Biodiesel can also be used as a heating fuel in domestic and commercial boilers.
This sounds al nice but what are the hard facts that make biodiesel better for the environment and you compared to regular diesel? A test of the U.S. Environmental Protection Agency (EPA) (shown here below) shows you the reductions in carbon monoxide, sulfates and other harmful elements when you drive on B100 or B20 (biodiesel). Check the complete factsheet here.
So is biodiesel the solutions to all our problems? I guess not, it is a sustainable and renewable form of energy but to produce biodiesel you still need to grow plants and you still got emissions. Nevertheless, it is a great way to go from non-sustainable way of life to a zero-emission way. So for the short term it is a good solution.