vxSmartWay
Transport Partnership
U.S. ENVIRONMENTAL PROTECTION AGENCY
EPA420-F-06-044
October 2006
Alternative Fuels:
Biodiesel
B
iodiesel is a renewable fuel produced from agricultural resources such as vegetable oils. In the United
States, most biodiesel is made from soybean oil; however canola oil, sunflower oil, recycled cooking oils,
and animal fats are also used.
How It's Made
To make biodiesel, the base oil is put through a process called
"esterificiation." This refining method uses an industrial
alcohol (ethanol or methanol) and a catalyst (substance that
enables a chemical reaction) to convert the oil into a fatty-acid
methyl-ester fuel (biodiesel).
Biodiesel in its pure form is known as "neat biodiesel" or
B100, but it can also be blended with conventional diesel, most
commonly as B5 (5 percent biodiesel and 95 percent diesel)
and B20 (20 percent biodiesel and 80 percent diesel). Biodiesel
is registered with the U.S. Environmental Protection Agency
(EPA) and is legal for use at any blend level in both highway
and non-road diesel vehicles.
Most diesel engines can run on biodiesel without needing any
special equipment. If you are interested in using biodiesel in
your vehicle or equipment, check with the manufacturer for
any recommendations and information regarding engine
warranties. In addition, once you have determined the proper
blend for your vehicle, make sure to purchase your fuel from a
reputable dealer selling commercial grade biodiesel.
Biodiesel -vs- Vegetable Oil
In 1895, Dr. Rudolf Diesel invented the diesel engine with the
intention of running it on a variety of fuels, including vegetable
oil. In fact, when he demonstrated his engine at the World
Exhibition in Paris in 1900, he fueled the vehicle with peanut
oil. However, biodiesel and vegetable oil are very different.
Raw vegetable oil or recycled greases (also called waste
cooking oil) that have not been processed into esters are not
biodiesel, and are not registered by EPA for legal use in
vehicles. In addition, vehicles converted to use these oils
would likely need to be certified by the EPA; to date EPA
has not certified any conversions. These conversions may
also violate the terms of the vehicle warranty. For more
information on the certification process, please visit EPA's
Web site at: www.epa.gov/otaq/cert/dearmfr/cisd0602.pdf.
Performance
Vehicles have similar horsepower and torque as conventional
diesel when running on biodiesel. Chemically speaking,
biodiesel has a higher cetane number, but slightly lower
energy content than diesel. To the average driver, this means
better engine performance and lubrication, but a small
decrease in fuel economy (2-8 percent). Biodiesel vehicles
can also have problems starting at very cold temperatures,
but this is more of an issue for higher percentage blends such
as B100 and easily solved the same way as with
conventionally fueled vehicles -by using engine block or fuel
filter heaters or storing the vehicles in a building.
Availability
In 2004, 25 million gallons of B100 were sold. By 2005, that
number had tripled. Today, approximately 600 fleets
nationwide use biodiesel blends in their diesel engines, and
biodiesel is available in its various blends at approximately
800 locations across the United States. A complete list of
stations is available at www.biodiesel.org.
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Affordability
Benefits
The price of biodiesel blends varies depending on geographic
area, base material (corn, soybeans, etc.), and supplier.
Although biodiesel can cost more than petrodiesel, diesel
drivers can transition to biodiesel without purchasing new
vehicles. In the case of fleets, managers can transition to
biodiesel without acquiring new spare parts inventories or
rebuilding refueling stations.
Maintenance
Generally, the use of biodiesel does not cause many
maintenance issues. However, when used for the first time,
biodiesel can release deposits accumulated on tank walls and
pipes from previous diesel fuel, initially causing fuel filter
clogs. As a result, vehicle owners should change the fuel filter
after their first tank of biodiesel. Also, biodiesel can degrade
rubber fuel system components, such as hoses and pump seals.
This is especially true with higher-percentage blends, and older
vehicles. Many newer vehicles have biodiesel-compatible
components, but it is best to consult your owner's manual or
contact your vehicle manufacturers for specific information.
Biodiesel has a number of important benefits. As an alternative
to diesel, it can help reduce U.S. dependence on foreign oil.
Biodiesel also provides significant greenhouse gas (GHG)
emission reductions. B100 reduces lifecycle greenhouse gas
emissions by more than 50 percent, while B20 reduces GHG
emissions by at least 10 percent.
In addition, biodiesel offers several criteria emissions benefits
for the existing vehicle fleet. It reduces emissions of carbon
monoxide, particulate matter (PM), and sulfates, as well as
hydrocarbon and air toxics emissions.
A 2002 EPA summary analysis of existing data suggests
vehicles using biodiesel may emit slightly more nitrogen oxide
(NOx) (about 2% for B20 and 10 percent for B100).
Subsequent studies have yielded mixed results, with some
showing small increases and others showing small decreases.
EPA plans a further investigation to fully assess this issue,
including the emissions impact of using biodiesel in vehicles
equipped with PM traps and NOx aftertreatment designed to
meet strict new emission standards.
For More Information
EPA Grow & Go Web Site: www.epa.gov/smartway/growandgo
EPA Alternative Fuels Web Site: www. epa. gov/otaq/consumer/fuels/altfuels/altfuels.htm
DOE Alternative Fuels Data Center Web Site: www.eere.energy.gov/afdc
National Biodiesel Board Web Site: www.biodiesel.org
http://www.epa.gov/smartway
EPA420-F-06-044
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