Biodiesel offers renewable alternative to petroleum

Fuels derived from renewable biological resources for use in diesel engines are known as biodiesel fuels. Animal fats and virgin and recycled vegetable oils derived from soybeans, canola, corn, sunflowers and other seed crops can be used to produce biodiesel fuel. Tall oil, produced from wood pulp waste, is another feedstock source. Biodiesel can either be used in its pure state or blended with conventional diesel fuel derived from petroleum.

Rudolf Diesel first demonstrated that a diesel engine could run on peanut oil in 1900. Vegetable oil as a fuel attracted little attention except in times of crisis such World War II and the energy shortages of the 1970s. However, increasing environmental concerns, expensive overproduction in European agriculture and changing government policies are sparking new interest in this renewable fuel.

Because its specific gravity is nearly identical to petroleum diesel’s, biodiesel can be mixed with the conventional fuel in any proportion. Commercial grades of biodiesel are usually rated by the percentage of renewable fuel the mixture contains. Consequently, B100 is 100 percent or “neat” biodiesel. A 20 percent blend of biodiesel with 80 percent petroleum diesel fuel is called B20.

Neat biodiesel has a BTU content of 121,000 BTU per gallon, compared to the average for No. 2 diesel fuel of 131,000 and 126,000 BTU per gallon for No. 1 diesel. It contains 11 percent oxygen by weight, which accounts for its slightly lower heating value, less than 15 ppm sulfur and no nitrogen or aromatics. This results in a fuel that burns more cleanly than petroleum, with characteristically low carbon monoxide, particulate soot and hydrocarbon emissions.

Fuel economy, power and torque are proportional to the BTU content of the biodiesel or biodiesel-blend fuel. For example, B20 tends to reduce power, torque and fuel economy by slightly less than 2 percent.