As petroleum refining went beyond kerosene for lighting the ‘by-products’ such as gasoline and gasoil/diesel became significantly more available and cheaper than vegetable oil, thus dominated the motor fuels market.  However, in today’s insecure energy world (more than 60% of the crude oil used in the United States is imported) the role of biodiesel as a primary motor fuel is reemerging.  Other forces behind increasing biodiesel production include low commodity prices for feedstocks, environmental concerns with continued petroleum diesel use, a broad desire for truly renewable fuels from sustainable resources, and the recognition of significantly higher life-cycle costs for other alternative fuels.

How does biodiesel differ from conventional petroleum diesel?  Due to its raw material make-up, biodiesel is essentially free from sulfur and aromatics.  The emission of Particulate Matter is reduced 55% from petroleum diesel and Carbon Monoxide is reduced 43% when B100 is used.  Biodiesel contains no nitrogen or aromatics and typically contains <15ppm sulfur.  Biodiesel contains 11% oxygen by weight, which accounts for its slightly lower heating value (energy content) and its low Carbon Monoxide, Particulate Matter, soot and hydrocarbon emissions.  The energy content of biodiesel is roughly 10% less than No.2 diesel, however the fuel efficiency is the same as petroleum diesel fuel.  Biodiesel has a higher Cetane than petroleum diesel.

When compared with the other significant renewable fuel, biodiesel has two distinguishing, important characteristics.  Biodiesel has a very positive net energy gain, with a 3-4 to 1 ratio, which is much higher than that of ethanol.  Also, using biodiesel in diesel engines has always been a very positive experience with no concerns expressed about engine problems.  The higher lubricity characteristic than Ultra Low Sulfur Diesel, which is being produced in anticipation of the national, 15ppm sulfur standard to be imposed in the middle of this decade, make biodiesel a superior performing fuel.  While biodiesel has yet to capture a large portion of the 55 billion gallons/year of petroleum diesel consumed in the USA, in the European Union more that 900 million gallons of biodiesel was consumed in 2002.

Biodiesel is considered a qualified Alternative Fuel by both the US-EPA and the US-DOE and a fuel additive under Section 211(b) of the Clean Air Act.  As such it may be used to meet the EPACT vehicle standards imposed on federal, state and agency fleets.  Federal Mandate 13149 requires a 20% reduction in  fossil fuel use by federal fleets by 2005.  Biodiesel represents the easiest method for fleets to meet this mandate.

A key consideration in the choice of an alternative fuel by a fleet operator is the overall life-cycle cost of the fuel.  The following graph, Booz Allen Hamilton 2002, reflects the basis upon which biodiesel should be the fuel of choice for fleets which operate diesel engines.