What Is a Biodiesel Engine?

David Bishop

A biodiesel engine is a compression engine that has been manufactured or converted to use fuels derived from biological sources rather than petroleum. This is attractive from an environmental standpoint and, as regular gas prices rise, a financial standpoint. Converted biodiesel engines are sometimes used in automobiles and home generators, and most regular diesel engines can use refined and blended biodiesel fuel.

Commercially available biodiesel often costs more than other fuel, and not many stations sell it.
Commercially available biodiesel often costs more than other fuel, and not many stations sell it.

Diesel engines are different from the internal combustion engines with which most drivers in the U.S. are familiar. These engines do not use spark plugs to ignite fuel; instead, they compress the fuel until it heats up to its combustion point. Diesel fuel is heavier and oilier than regular gasoline and usually has a separate pump at a filling station. This density allows it to be more efficient and produce more miles per gallon. In the U.S., diesel engines are most commonly used in larger trucks and locomotives, although some automobiles are manufactured with these engines.

Diesel vehicles may also use biodiesel.
Diesel vehicles may also use biodiesel.

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A biodiesel engine may be less fuel efficient than one using regular diesel. The engine may also have problems in colder weather, because biodiesel fuel has the tendency to gel if the temperature gets too low. Biodiesel does have the advantage of being a renewable energy source and can be produced locally in most areas. A biodiesel engine produces much less carbon dioxide (CO2) than a standard engine, although mass production can lead to increased deforestation.

Biodiesel engines typically suffer less wear and tear than regular engines because of the lubricating effects of the fuel. When converting an older engine to biodiesel, some hoses and seals may need to be replaced because of their reaction to the new fuel. One should always use high-quality fuel in a biodiesel engine to avoid engine deposits and clogging. Converted engines may need to have their tuning adjusted.

When purchasing a vehicle with a biodiesel engine, it is important to note the engine's fuel rating. The engines are graded based on what percentage of biodiesel fuel can be used. A B100 engine can use pure biodiesel, while a B20 engine is limited to 20 percent biodiesel or less. Engines for fleet vehicles are often designed to have higher fuel ratings. Using a higher concentration than the vehicle is designed to handle can damage the engine and void the manufacturer's warranty.

The biodiesel engine has become more popular in the wake of rising oil prices. As of 2011, many European nations are adopting biodiesel for transportation and shipping. Along with solar, nuclear and wind energy, biodiesel is seen as an important alternative energy source for the future. While the 2011 production of biodiesel fuel is not enough to compensate for petroleum usage, the biodiesel engine is considered by many advocates as an important step away from society's dependency on oil.

Some diesel-electric locomotives have been converted to run on biodiesel fuels.
Some diesel-electric locomotives have been converted to run on biodiesel fuels.

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