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BIODIESEL

Biodiesel, a renewable fuel derived from animal fats and vegetable oils, is a diesel fuel substitute that can be used in heavy-duty diesel vehicles like trucks and buses with no engine modification. The main feedstock for biodiesel can be domestically produced from agricultural commodities like soybeans and rapeseed, or refined from used frying oil and unwanted animal fats. It commonly is mixed at a ratio of 20 percent biodiesel to 80 percent diesel, referred to as B20.

TABLE 1: BIODIESEL EMISSIONS (B20) COMPARED TO CONVENTIONAL DIESEL

Hydrocarbons	20% reduction
Carbon Monoxide	12% reduction
Carbon Dioxide	16% reduction over lifecycle[1]
Nitrogen Oxides	2% Increase
Particulate Matter	12% Reduction
PAH & nPAH compounds	16% to 18% reduction
Fuel Economy	2% reduction[2]

The costs associated with converting to biodiesel are relatively low. Diesel fuel storage tanks already in place can just as easily store biodiesel. Greater costs can be incurred when a fuel mixture containing a high ratio of biodiesel is used[3]. Pure Biodiesel has a tendency to act as a solvent, releasing fuel tank deposits accumulated under conventional diesel use. Costs are incurred when these deposits clog engine filters (filter clogging occurs in less than 3% of vehicles). The filters must be replaced periodically until all significant deposits have been removed.

Compared to petroleum diesel, B20 increases nitrogen oxide emissions of 2 percent. This may raise concerns for local decision makers working to decrease concentrations of ozone in their area. Research is underway to develop technical fixes to reduce these emissions. Researchers at the National Renewable Energy Laboratory in Boulder, CO have learned that additives which increase the cetane rating of biodiesel can reduce NOx emissions by 4 percent in older vehicles. The same researchers question whether the NOx increases associated with biodiesel are attributable to the fuel or to the age of the engine. Further research is underway to clarify this issue. Click here to access the latest NREL study on Biodiesel and NOx.

In October 2002, the Clark County School District serving Las Vegas, Nevada and surrounding areas became the largest biodiesel fleet in the world with over 1200 vehicles. The primary source of the fuel is used frying oil taken from Las Vegas hotels and casinos. The Medford Township School District in New Jersey began using biodiesel in 1997 and has done so longer than any other fleet in the United States.

[1] National Renewable Energy Laboratory, Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in an Urban Bus, May 1998

[2] National Biodiesel Board (800) 841-5849

[3] The price of biodiesel has historically been higher than petroleum diesel, but this price is likely to decrease as production and distribution capacity improves. Current domestic production capacity of biodiesel stands at around 15-20 million gallons a year and is expected to grow. According to the nation’s clean cities coordinators, the average price of B20 varied between $1.46 and $1.73 in October and November of 2002.

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