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.
