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Frequently Asked Questions

(source: U.S. DOE, Office of Energy Efficiency and Renewable Energy)

Alternative Fuels

Q: How are alternative fuels defined?
Alternative fuels are substantially non-petroleum and yield energy security and environmental benefits. DOE currently recognizes the following as alternative fuels:

  • Mixtures containing 85% or more by volume of alcohol fuel, including methanol and denatured ethanol
  • Natural gas (compressed or liquefied)
  • Liquefied petroleum gas (propane)
  • Hydrogen
  • Coal-derived liquid fuels
  • Fuels derived from biological materials
  • Electricity (including electricity from solar energy)
  • 100% Biodiesel (B100) *

Through the Alternative Fuel Petition Program, third parties can petition DOE to add alternative fuels to this list. For more information about EPAct and its programs, download "EPAct: Alternative Fuels for Energy Security, Cleaner Air"

* Pure biodiesel (B100) is considered an alternative fuel under EPAct. Lower-level biodiesel blends are not considered alternative fuels, but covered fleets can earn one EPAct credit for every 450 gallons of B100 purchased for use in blends of 20% Biodiesel or higher.

Q: How safe are alternative fuels?
A: Most people are familiar with gasoline, so they rarely question its safety. However, people who are unaccustomed to alternative fuels may have misconceptions or doubts about their safety in vehicle applications. Some safety issues associated with the use of alternative fuels are outlined here.

Biodiesel is biodegradable, meaning it dissipates quickly after a spill. It has a high flashpoint and low volatility, so it does not ignite as easily as conventional diesel, increasing the margin of safety in its handling. Biodiesel degrades four times faster than conventional diesel and is not particularly soluble in water. It is nontoxic, so it is safe to handle, transport, and store. As with all alternative fuels, adequate training is recommended to operate and maintain biodiesel vehicles.

Compressed Natural Gas (CNG)
The fuel is odorless, and odorants must be added to ensure users can detect leaks and spills. In the event of a leak, the gas will rise to the ceiling and create a potential risk in enclosed areas. Sturdy, heavy storage tanks must be used to avoid possible hazards from the high-pressure storage.

Electrical circuits are self-contained and grounded to prevent the risk of shock from the vehicle frame. Electric vehicle battery packs store enough energy to produce a dangerous, even lethal shock. Electrolytes in the batteries may cause chemical burns, so protective gear must be worn when handling the batteries.

If used in an E85-compatible vehicle, E85 is as safe as gasoline.

Liquefied Natural Gas (LNG)
The fuel is cooled cryogenically to -2600F. At this temperature, bodily contact with the liquid fuel, cold metals, or cold gas can cause cryogenic burns (frostbite). Methane gas detectors must be installed to detect leaks because odorants cannot be added to LNG.

Liquefied Petroleum Gas (LPG)
Strong tank construction is required, but the pressure hazard is less than with CNG. LPG should be odorized, and detectors are recommended to help detect leaks or spills. The fuel is extremely volatile, and LPG fires burn twice as hot as gasoline fires.

Methanol is corrosive to several metals, rubberized components, gaskets, and seals. Low flame luminosity makes M85 fires difficult to detect in the daylight. Unhealthy exposure can occur through fume inhalation, ingestion, or direct contact with skin.

Q: How many gallons of ethanol are produced from a bushel of corn?
One bushel of corn can produce at least 2.5 gallons of ethanol. It can also make 1.6 lbs. of corn oil, 10 lbs. of high protein feed, 2.6 lb of corn meal, or 31.5 lbs. of starch to make beverages or sweeteners. For more facts about ethanol, visit the National Corn Growers Association website.

Q: How many gallons of biodiesel can you make from a bushel of soybeans?
A: According to the U.S. Department of Agriculture's (USDA) Farm Service Agency , one bushel of soybeans yields approximately 1.4 gallons of biodiesel. Soybeans contain about 20% oil, so it takes almost 7.3 pounds of soybean oil to produce a gallon of biodiesel. U.S. soybean production reached about 2.5 billion bushels in 2003, according to the USDA National Agricultural Statistics Service. The United States produces about 20 million gallons of biodiesel per year using soybeans and other feedstocks.

Soybean oil and used cooking grease are the two main feedstocks used to produce biodiesel in the U.S.

For more information about biodiesel, see the Alternative Fuels Data Center (AFDC) Biodiesel Web site, the DOE Biofuels Web site and the National Biodiesel Board Web site.

Q: Where can I refuel my alternative fuel vehicle?
The U.S. Department of Energy's Alternative Fuel Station Locator and Route Mapper can pin point and direct you to alternative fueling stations across the country. Both tools feature public and private refueling sites that offer liquefied and compressed natural gas, liquefied petroleum gas (propane), ethanol (85%), electricity, biodiesel, and hydrogen, so finding every type of alternative fuel available is easy.

How do biodiesel emissions compare to petroleum diesel?
A: 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. (source: National Biodiesel Board,




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