Using Biodiesel as a Fuel


For many farmers, the task of manufacturing high quality biodiesel fuel is more than they really want to take on. Some farmers opt to provide their oilseed or pressed oil to a professional biodiesel processor, who either pays in cash or in fuel for use on the farm. Others may choose to purchase biodiesel from a nearby producer rather than growing their own. Regardless of whether it’s made on site or obtained from a nearby plant, good quality biodiesel is a reliable fuel that runs well, reduces pollution and supports the local farm economy.

The University of Idaho Vandal Trolley is fueled with biodiesel.


Where can I buy biodiesel?

For a map of biodiesel retail locations, see the National Biodiesel Board’s Retail Locations.

The U.S. Department of Energy’s Alternative Fuels and Advanced Vehicles Data Center has an interactive map of biodiesel retail locations (B20 and above): Alternative Fueling Station Locator.

If you would like to buy B100 (pure biodiesel), here is a link to a map you can purchase: Biodiesel Smarter B100 Map.

Energy Content

Biodiesel has lower energy content than petrodiesel. On a volume basis it has 8 percent less BTU’s/gallon so users of B100 tend to experience about an 8 percent drop in power or an 8 percent rise in fuel consumption.

Biodiesel is slightly denser than petrodiesel. However, it contains about 11 percent oxygen, whereas petrodiesel contains no oxygen. The oxygen doesn’t contribute to the energy content, although it does help the fuel to burn more efficiently and with lower tailpipe emissions.

Energy Balance

Biodiesel produces more energy than is consumed in its manufacture. The latest study from the United States Department of Agriculture (USDA), Energy Life-Cycle Assessment of Soybean Biodiesel, found that soy biodiesel yields more than four and one-half times the fossil energy needed to produce it. For more information on biodiesel energy balance, see Energy Life Cycle Analysis of Biodiesel.

Vehicle Compatibility

Biodiesel and biodiesel blends can be used in any modern diesel engine made after 1991. Cold temperatures can be a problem for high-percentage blends of biodiesel. Pure biodiesel made from soybean oil can clog fuel filters due to crystallization if the temperature drops below 28˚F. To reduce filter plugging problems during cold weather, biodiesel can be blended with fossil diesel.

Because biodiesel is a strong solvent, it will probably loosen debris in pipes and tanks, clogging filters initially. Remedy this problem by changing filters soon after first use. Sometimes rubber hoses and gaskets on older vehicles don’t hold up well with pure biodiesel. Pre-1991 vehicles should be monitored for hose degradation or seal weepage. If these conditions occur, the hoses and seals should be replaced with viton-based parts.


Biodiesel is a relatively safe product. It is considered nonflammable and biodegradable. Pure biodiesel (B100) can be transported without displaying warning signs in most states. Biodiesel blends require warning signs if the flash point of the blended fuel is lower than 200°F because the petrodiesel portion is flammable.

However, the chemicals used to make biodiesel are hazardous. For more information, see Safe Chemical Handling in Biodiesel Production.

Tax Rebates and Incentives

Biodiesel that is used on public roads is subject to federal, state and local taxes. However, the federal government and many state governments offer a variety of tax rebates and incentives to promote the adoption of biodiesel.

For an overview of federal laws, see Federal Incentives and Laws for Biodiesel.

For an overview of state laws, see Biodiesel Incentives and Laws.

Engine Warranties

Engine warranties are not affected by the use of biodiesel, although dealers are frequently confused on this point. Manufacturers’ warranty statements only cover the parts and assembly of the engines and never cover problems caused by the fuel, regardless of whether the fuel is petroleum-based diesel or biodiesel. Questions about liability for damages caused by a specific fuel should be addressed to the fuel supplier. See the National Biodiesel Board’s Standards and Warranties page for more information.

Also see this summary chart: Automakers’ and Engine Manufacturers’ Positions of Support for Biodiesel Blends.

Engine Performance When Using Biodiesel

Since 2006, petrodiesel fuel used for highway transportation in the United States has been required to contain less than 15 parts per million of sulfur. The processing to remove the sulfur from petrodiesel decreases the fuel’s lubricity. Biodiesel is an excellent lubricator. As little as 1 percent biodiesel added to petrodiesel will improve the fuel’s lubricating properties and thus could extend the life of various diesel engine components. Biodiesel also has a high cetane value and can be blended with petrodiesel to improve the burning characteristics of lower quality petro-diesel. In older diesel engines, the use of biodiesel in blends of 20% and higher will reduce black smoke. It also helps to quiet noisy engines.

Proper Storage of Biodiesel Fuel

Biodiesel should be kept in a cool, clean, light-proof container that is filled to the top and semi-sealed, allowing minimal air exchange to prevent pressure-buildup.

Biodiesel should not be stored or transported in aluminum, copper, brass, bronze, lead, tin or zinc because these metals will hasten degradation of the fuel. Instead, choose containers made from aluminum, steel, fluorinated polyethylene, fluorinated polypropylene, Teflon® or fiberglass.

Tanks designed to store and transport petrodiesel can be used to store biodiesel with few if any problems. However, do not use an old diesel storage tank for biodiesel unless it is first cleaned and dried thoroughly, since biodiesel can degrade due to contact with water and will dissolve sludge that can plug fuel filters.

As much as possible, keep only a small air space above the fuel — 2 percent air space is recommended in order to allow for thermal expansion. More air space may allow the biodiesel to accumulate more water from the air. If possible, drain free water off the bottom of storage tanks on a regular basis.

Heat, sunlight and oxygen will cause biodiesel to degrade more rapidly, so storage should minimize exposure to these conditions.

If biodiesel will be stored for longer than about six months, a stability additive should be used, especially in more southern climates due to increased temperature and humidity.

One final tip: When possible, top off the vehicle’s tank at the end of the day rather than letting it sit partly full. This reduces the risk that water will condense in the fuel tank and contaminate the fuel.

More Topics on Use and Storage of Biodiesel

For Additional Information

  • Biodiesel Handling and Use Guide. This 50-page publication from the National Renewable Energy Laboratory is considered the definitive resource on the issue of biodiesel handling and use. It is intended for those who blend, distribute and use biodiesel.

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