Frequently asked questions

What is biodiesel?

Biodiesel is the name of a clean burning alternative fuel, produced from domestic, renewable resources. Biodiesel contains no petroleum, but it can be blended at any level with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with little or no modifications. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics.

Is biodiesel the same as ethanol?

No, Biodiesel is produced from any fat or oil such as vegetable oil, through a refinery process called transesterification. This process is a reaction of the oil with an alcohol to remove the glycerin, which is a by-product of biodiesel production. Fuel-grade biodiesel must be produced to strict industry specifications (ASTM D6751) in order to insure proper performance. Biodiesel is the only alternative fuel to have fully completed the health effects testing requirements of the 1990 Clean Air Act Amendments. Biodiesel that meets ASTM D6751 and is legally registered with the Environmental Protection Agency is a legal motor fuel for sale and distribution.

Biodiesel has a couple of huge advantages over ethanol. First, it is not miscible in water, so you don't have the huge input of fossil fuels that is required to separate ethanol from water. This makes the energy balance far better than that of ethanol. A poor energy balance is the primary objection to ethanol (especially grain-ethanol).

The second major advantage biodiesel has is that it has over 1.6 times the BTU value of the same volume of ethanol. A gallon of biodiesel contains approximately 121,000 BTUs/gallon (about the same as gasoline), versus approximately 75,000 BTUs per gallon for ethanol. Diesel engines also run 35-40% more efficient than spark-ignition engines (the kind that use gasoline or ethanol). That means that 1 gallon of biodiesel has the effective energy value of 1/0.65, or 1.5 gallons of gasoline. 1 gallon of gasoline is worth around 1.5 gallons of ethanol on a BTU equivalent basis, so 1 gallon of biodiesel is effectively equivalent to (1.5*1.5) or 2.25 gallons of ethanol! The biodiesel group at UNH has conducted similar research.

Is BD efficient to produce?

Although biodiesel costs more than petroleum diesel in some places, the price gap continues to narrow. The price falls considerably when waste cooking oil is used, since 75% of the price of biodiesel comes from the oil feedstock. If waste cooking oil is used, this economic advantage can be moved to the price of the fuel at the pump.

Does biodiesel cost more than petro-based diesel?

Biodiesel saves money. Engines running on biodiesel have been shown to require less maintenance. Also, biodiesel use allows federal fleet managers to keep existing equipment on the road longer and still adhere to new, stricter emissions standards.

Will biodiesel work in my diesel-run car?

Yes! Any diesel car may be run on biodiesel with little to no modifications. Adjustments may include:

  • Rubber hose and gasket replacement. In older cars (15 years or older) rubber gaskets and hoses will need to be replaced, as biodiesel has a tendency to degrade rubber.
  • Replacement of fuel filters. When biodiesel is first used an increase in deposits within the engine system may occur, so more frequent replacement of fuel filters may be necessary.
  • Purchase and use of American Society for Testing and Materials (ASTM) compliant biodiesel. ASTM compliant fuel ensures quality fuel that meets specified alternative fuel standards.

Do I need to modify my heater, truck to run on biodiesel?

Biodiesel can be operated in any diesel engine with little or no modification to the engine or the fuel system. Biodiesel has a solvent effect that may release deposits accumulated on tank walls and pipes from previous diesel fuel storage. The release of deposits may clog filters initially and precautions should be taken. Ensure that only fuel meeting the biodiesel specification is used.

Find an alternative fueling station location near you.

U.S. Department of Energy's Alternative Fuel Station Locator

National Biodiesel Board's Retail Fueling Site

Biodiesel Hotline to find retail availability anywhere in the United States (staffed 24 hours a day, 7 days a week)
1-866-BIODIESEL (246-3437)

Is biodiesel as efficient as petro-based diesel?

Biodiesel is the only alternative fuel to have fully completed the health effects testing requirements of the Clean Air Act. The use of biodiesel in a conventional diesel engine results in substantial reduction of unburned hydrocarbons, carbon monoxide, and particulate matter compared to emissions from diesel fuel. In addition, the exhaust emissions of sulfur oxides and sulfates (major components of acid rain) from biodiesel are essentially eliminated compared to diesel.

Of the major exhaust pollutants, both unburned hydrocarbons and nitrogen oxides are ozone or smog forming precursors. The use of biodiesel results in a substantial reduction of unburned hydrocarbons. Emissions of nitrogen oxides are either slightly reduced or slightly increased depending on the duty cycle of the engine and testing methods used. Based on engine testing, using the most stringent emissions testing protocols required by EPA for certification of fuels or fuel additives in the US, the overall ozone forming potential of the speciated hydrocarbon emissions from biodiesel was nearly 50 percent less than that measured for diesel fuel.

Is biodiesel toxic, flammable or hazardous?

A 1998 biodiesel lifecycle study, jointly sponsored by the US Department of Energy and the US Department of Agriculture, concluded biodiesel reduces net CO2 emissions by 78 percent compared to petroleum diesel. This is due to biodiesel's closed carbon cycle. The CO2 released into the atmosphere when biodiesel is burned is recycled by growing plants, which are later processed into fuel.

Is biodiesel safer than petroleum diesel? Scientific research confirms that biodiesel exhaust has a less harmful impact on human health than petroleum diesel fuel. Biodiesel emissions have decreased levels of polycyclic aromatic hydrocarbons (PAH) and nitrited PAH compounds that have been identified as potential cancer causing compounds. Test results indicate PAH compounds were reduced by 75 to 85 percent, with the exception of benzo(a)anthracene, which was reduced by roughly 50 percent. Targeted nPAH compounds were also reduced dramatically with biodiesel fuel, with 2-nitrofluorene and 1-nitropyrene reduced by 90 percent, and the rest of the nPAH compounds reduced to only trace levels.

Biodiesel's flash point is over 300° F (therefore considered "not flammable")