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Frequently Asked Questions :: Alternative Fuels

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

Alternative Fuels

Q: How are alternative fuels defined?

A: 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?

A: 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 website, the DOE Biomass website, and the National Biodiesel Board website.

Q: Where can I refuel my alternative fuel vehicle?

A: The U.S. Department of Energy's Alternative Fuel Station Locator and Route Mapper can pinpoint 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.

Q: 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,

Q:What is a flexible fuel vehicle?

Flexible fuel vehicles (FFVs) are capable of operating on gasoline, E85 (85% ethanol, 15% gasoline), or a mixture of both.

Unlike natural gas and propane bi-fuel vehicles, flexible fuel vehicles contain one fueling system, which is made up of ethanol compatible components and is set to accommodate the higher oxygen content of E85. E85 should only be used in ethanol-capable FFVs.

Other than fueling capability and ethanol compatible components, FFVs are similar to their conventional gasoline counterparts. Their power, acceleration, payload, and cruise speed are comparable whether running on ethanol or gasoline. The only noticeable difference: fuel economy is lower when FFVs run on ethanol.

Q: What is "biomass to liquids?" technology?

Biomass to liquids is a term describing processes for converting diverse biomass feedstocks into a range of liquid fuels. These processes are usually distinguished from enzymatic/fermentation processes and processes that use only part of a biomass feedstock, such as those typically used to produce ethanol, biobutanol, and biodiesel.

To learn about biomass to liquids, choose from these links:

Q: What is the impact of biofuels on the environment?

A: Global Warming. The combustion of fossil fuels such as coal, oil, and natural gas has increased the concentration of carbon dioxide in the earth's atmosphere. The carbon dioxide and other so-called greenhouse gases allow solar energy to enter the Earth's atmosphere, but reduce the amount of energy that can re-radiate back into space, trapping energy and causing global warming.

One environmental benefit of replacing fossil fuels with biomass-based fuels is that the energy obtained from biomass does not add to global warming. All fuel combustion, including fuels produced from biomass, releases carbon dioxide into the atmosphere. But, because plants use carbon dioxide from the atmosphere to grow (photosynthesis), the carbon dioxide formed during combustion is balanced by that absorbed during the annual growth of the plants used as the biomass feedstock—unlike burning fossil fuels which releases carbon dioxide captured billions of years ago. You must also consider how much fossil energy is used to grow and process the biomass feedstock, but the result is still substantially reduced net greenhouse gas emissions. Modern, high-yield corn production is relatively energy intense, but the net greenhouse gas emission reduction from making ethanol from corn grain is still about 20%. Making biodiesel from soybeans reduces net emissions nearly 80%. Producing ethanol from cellulosic material also involves generating electricity by combusting the non-fermentable lignin. The combination of reducing both gasoline use and fossil electrical production can mean a greater than 100% net greenhouse gas emission reduction. In the case of ethanol from corn stover, we have calculated that reduction to be 113%.

Vehicle Emissions. Petroleum diesel and gasoline consist of blends of hundreds of different hydrocarbon chains. Many of these are toxic, volatile compounds such as benzene, toluene, and xylenes, which are responsible for the health hazards and pollution associated with combustion of petroleum-based fuels. Carbon monoxide, nitrogen oxides sulfur oxides and particulates, are other specific emissions of concern. A key environmental benefit of using biofuels as an additive to petroleum-based transportation fuels is a reduction in these harmful emissions.

Both bioethanol and biodiesel are used as fuel oxygenates to improve combustion characteristics. Adding oxygen results in more complete combustion, which reduces carbon monoxide emissions. This is another environmental benefit of replacing petroleum fuels with biofuels. Ethanol is typically blended with gasoline to form an E10 blend (5%-10% ethanol and 90%-95% gasoline), but it can be used in higher concentrations such as E85 or in its pure form. Biodiesel is usually blended with petroleum diesel to form a B20 blend (20% biodiesel and 80% petroleum diesel), although other blend levels can be used up to B100 (pure biodiesel).

What is Fischer-Tropsch diesel?

Fischer-Tropsch (F-T) diesel is synthetic diesel fuel produced by converting gaseous hydrocarbons, such as natural gas and gasified coal or biomass, into liquid fuel.

Fischer-Tropsch diesel can be substituted directly for conventional (petroleum-derived) diesel to fuel diesel-powered vehicles, without modification to the vehicle engine or fueling infrastructure.

To enhance energy independence in the face of apartheid-related embargoes, South Africa satisfied most of its diesel demand with natural gas- and coal-derived F-T diesel for decades and is still using the fuel in significant quantities. More recently, global concerns about energy supplies and costs and the environment have created interest in F-T fuels elsewhere. For example, Shell markets F-T diesel as a premium diesel blend in Europe and Thailand. In the United States, F-T diesel has been used in demonstration projects.

For more information on Fischer-Tropsch fuels, see DOE's Gas to Liquids, Coal to Liquids, and Biomass to Liquids pages.

Q: What are the pros and cons of ethanol?
Pros: Ethanol pollutes less than regular gas. And we already know how to make it in large volumes. Brazil uses ethanol made from sugar cane extensively. Investors are pouring billions of dollars into ethanol refineries in the U.S. There are 109 ethanol plants in the U.S. and 40 new projects coming on line, according to Michael Eckhart, president of American Council on Renewable Energy (ACORE).

Cons: Where to begin? First, food crops aren't an ideal fuel source. An acre of corn produces 480 gallons of ethanol, according to Paul McCroskey, chief financial officer at Ceres, which makes enzymes for the fuel industry. That's a lot of land.

Ethanol only puts out two-thirds the energy of gas, so car mileage is lower on ethanol. Ethanol production also generates tons of carbon dioxide, which, if it's not captured turns into greenhouse gases. Producing ethanol also requires lots of energy. It's popular, say some, because farmers love it, and they tend to show up on Election Day.

To top it off, the price of corn is climbing, while gas prices are declining. In January 2006, ethanol sold for $3 a barrel, while a bushel of corn cost $2. Now, ethanol sells for $2 per barrel and corn goes for $4.20 a bushel, according to ACORE. "We have seen the most profitable space in the fuel business disappear in a year," said Eckhart. OPEC, he added, will lower oil prices to put pressure on the ethanol industry. (Source: CNET News)

Q: What are the pros and cons of biodiesel?
Pros: It's got far fewer economic and environmental hurdles than ethanol, says Martin Tobias, a former Microsoft exec who now runs Imperium Renewables, a biodiesel maker. Diesel cars are very popular in Europe, and several manufacturers make high-mileage diesel cars. Some truck and bus makers already produce diesel hybrid trucks. Biodiesel could be sold to those people right now. And since industrial diesel users buy their fuel directly, they don't have to worry about corporate service stations snubbing biodiesel altogether.

Finally, biodiesel puts out far less carbon gases. Sulfur can be a problem with soy-based biodiesel, but Tobias says it can be contained.

Cons: Farming sometimes isn't the most eco-friendly activity, and some worry that a surge in demand for palm oil will lead to slash-and-burn agriculture and pollution in the tropics. Advocates, though, say that farmers are tackling this problem. One group in Colombia is growing biodiesel feedstock on old coca plantations. The rising popularity of biodiesel is expected to impact the cost of food oil.

Even after the new facilities get built, biodiesel is a drop in the bucket of the world's fuel needs. There are only 150 million gallons of the stuff produced a year in the U.S. and, although that number will climb to 250 gallons this year, the U.S. consumes about 62 billion gallons of diesel a year. (Source: CNET News)

Q: Where can I find biodiesel retailers in Montana?
The Montana Department of Environmental Quality (DEQ) provides a list of Montana biodiesel retailers on its website.

Q: How can I produce biodiesel on the farm?
A: Biodiesel is fairly simple to make. However, safety is key; would-be biodiesel producers are encouraged to watch this Biodiesel Safety Video.

The basic ingredients of biodiesel are vegetable oil or animal fat; alcohol (typically ethanol or methanol); and a catalyst (typically sodium hydroxide or potassium hydroxide). Put very simply, the ingredients are mixed in a reactor and stirred. After the reaction (called transesterification) takes place, the heavier glycerol component settles to the bottom and the resulting esters are pumped off. These esters are purified, usually by water washing, and then the biodiesel is suitable for use as fuel.

Methanol and strong bases like sodium hydroxide (NaOH) and potassium hydroxide (KOH) are hazardous. Use extreme caution when working with these materials.

For more information on biodiesel processing, see Biodiesel Production Principles and Processes. For information on extracting oil from oilseeds, see Oilseed Handling for Biodiesel Production. For information on the types of oilseed crops that you might grow for biodiesel production, see Oilseed Crops for Biodiesel Production. (source: MSU Extension)

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