Biodiesel is a natural and renewable domestic fuel alternative for diesel engines made from vegetable oils, mostly soy and corn. It contains no petroleum, is nontoxic and biodegradable.

Biodiesel burns clean, which results in a significant reduction of the types of pollutants that contribute to smog and global warming and emits up to 85% fewer cancer-causing agents. It is the only alternate fuel approved by the Environmental Protection Agency (EPA), has passed every Heath-Effects Test of the Clean Air Act and meets the requirements of the California Air Resources Board (CARB).

Biodiesel is made using an alcohol like methanol and a chemical process that separates glycerine and methyl esters (biodiesel) from fats or vegetable oils. Glycerine is used in many common products including soap and is highly marketable; therefore there is little waste in the process. That said, growing crops requires time and significant investment, and the fuel must be made and shipped to a local station. For these reasons biodiesel is more expensive than petroleum, gallon for gallon. This must be considered against the many economic advantages, however, that arise from a domestic form of fuel, a cleaner environment, an improvement in air quality, and a reduction of cancer-causing agents.

A "bootleg" form of biodiesel can be made from discarded cooking oils as collected from restaurants. The cooking oil must be put through a process before it can be used as fuel, but home-brewed biodiesel is not a legal form of the fuel as it isn't subject to standards.

Biodiesel has been rigorously and independently tested in virtually every type of diesel engine by a number of agencies in the laboratory and on the road. The National Biodiesel Board (NBB) reports the tests combine to account for over 50-million street miles plus intense off-road and marine use. Performance is said to rate comparably to petroleum in all areas from power to efficiency, hauling and climbing. It can be used in its pure form or blended with petroleum fuel. The most common mix is 20/80, referred to as "B20" containing 20% biodiesel by volume, and 80% petroleum.

Biodiesel can be used in any diesel engine with few to no modifications. The main effect is super-lubrication which has the benefit of acting like a solvent to clean the engine. If the engine has been previously running on conventional diesel this can result in an initial need to change fuel filters until sludge left by petroleum fuel is purged. This effect is more pronounced when using B100 (100% biodiesel), and may be less so with B20. Precautionary measures should be taken however, by checking the fuel filter after initial hours of running blended or neat fuel (100% biodiesel).

When using B100 exclusively, the lubrication could degrade certain types of rubber over time, which may require replacement of fuel hoses or fuel pump seals. This isn't as much of a concern with newer engines that contain parts designed for low-sulphur diesel (known as #2 diesel), as these parts are also compatible with biodiesel. The use of B20 did not result in the need to replace hoses or seals in the many miles of tests previously mentioned.

Like conventional diesel, biodiesel will cloud and gel at very cold temperatures, but blends like B20 are only slightly more sensitive than #2 diesel in this respect. The recommendations are the same regardless of blend: park the vehicle in or near shelter if possible; use optional fuel heaters; or mix with #1 diesel.

Biodiesel should not impact or void the manufacturer's warranty of any compression-ignition motor (diesel), however, it's always safest to check your warranty first. Call the manufacturer if unsure.

Agencies involved in the testing of biodiesel include the US Department of Energy, the US Department of Agriculture, the Lovelace Respiratory Research Institute, and the Southwest Research Institute, among others.

In the United States, biodiesel fuel is available at limited gasoline stations nationwide, usually in a B20 blend. It will likely cost a few pennies more per gallon, but the ample benefits to the environment, human health, our own economy, and the reduction of dependence on foreign oil are each powerful counterpoints. The NBB maintains a list of suppliers, distributors and public gas stations that carry biodiesel for those interested.