U.S. Department of Energy - Energy Efficiency and Renewable Energy

Tribal Energy Program

Biomass Energy - Biofuels

"Biofuel" is short for "biomass fuel." The term usually applies to liquid fuels used for transportation, such as ethanol and biodiesel. These fuels can be made entirely from biomass, such as B100, or blended with conventional fuels, such as E10. The number after the letter represents the percentage of biodiesel or ethanol in the fuel. Biofuels can also be used to produce electricity.

Unlike gasoline and diesel, biofuels contain oxygen. Adding biofuels to petroleum products allows the fuel to combust more completely, reducing air pollution.

The market for biofuels is growing. Existing production methods typically use relatively high-priced common crops — oil-rich seeds such as soybeans; sugarcane, corn, and other cereals — as feedstocks. All of these crops have other uses in our economy, driving up their cost. Future production methods will use cheaper feedstocks: the biodegradable portion of municipal solid waste, low-cost biowastes such as straw, or fast-growing, dedicated energy crops such as switchgrass, for example. Woody biomass, such as forest thinnings, can also be used to produce biofuels.

Ethanol

Photograph showing the exterior of an ethanol production plant, with metal cylinders and piping in the foreground and fields in the background.

An ethanol production plant in Nebraska. (Image credit: Chris Standlee)

Ethanol is the most widely used biofuel today. In 2003, more than 2.8 billion gallons were added to gasoline in the United States to improve vehicle performance and reduce air pollution.

Ethanol is an alcohol, and most is made using a process similar to brewing beer: starch crops are converted into sugars, the sugars are fermented into ethanol, and then the ethanol is distilled into its final form. Ethanol made from cellulosic biomass materials (plant fibers) instead of traditional starchy feedstocks is called bioethanol. Most existing ethanol production is in the hands of large companies, such as agricultural giant Archer Daniels Midland.

Ethanol is used to increase octane ratings and improve the emissions quality of gasoline. The Clean Air Act Amendments of 1990 mandated the sale of oxygenated fuels in areas of the country with unhealthy levels of carbon monoxide. Since that time, there has been strong demand for ethanol as an oxygenate blended with gasoline. The other once-common oxygenate, methyl tertiary butyl ether (MTBE), has been causing water pollution and is being phased out across the nation. Ethanol is the primary substitute for MTBE, helping to further increase demand.

In some areas of the United States today, ethanol is blended with gasoline to form an E10 blend (10% ethanol and 90% gasoline), but it can be used in higher concentrations, such as E85, or in its pure form. Fuel ethanol blends are successfully used in all types of vehicles and engines that require gasoline.

See the following for more information:

Renewable Diesel Fuels

Photograph showing a bus whose exterior has been painted with images of soybeans and the words: Soybean powered — this bus runs on soybean biodiesel.

This biodiesel-powered bus runs on fuel derived from soybeans. (Image credit: Nebraska Soybean Board)

There are a variety of fuels that can be used in diesel engines and that are made from renewable resources such as vegetable oils, animal fats, or other types of biomass such as grasses and trees. These renewable diesel fuels can be used in place of, or blended with, petroleum diesel.

Biodiesel is an example of a renewable diesel fuel that is used all across the United States today. Biodiesel is typically manufactured from vegetable oils, animal fats, or recycled restaurant greases, which are all renewable. In fact, Rudolf Diesel demonstrated his engine over 100 years ago using peanut oil. While petroleum has been the dominant fuel for diesel engines since then, the use of biodiesel has grown rapidly in the last several years in transportation fleets.

Biodiesel consists of fatty-acid alkyl esters. Fatty-acid alkyl esters are long chains of carbon molecules (12 to 22 carbon atoms long) with an alcohol molecule attached to one end of the chain. Biodiesel is made by a process called transesterification. Organically derived oils are combined with alcohol (usually methanol) and are then chemically altered to form fatty esters such as methyl ester. The biomass-derived esters can be blended with conventional diesel fuel to reduce emissions or used as a neat fuel (100% biodiesel).

E-diesel may be the next new renewable diesel fuel. E-diesel is a blend of ethanol and diesel fuel with other chemicals to improve the performance of the blend. The ethanol portion of E-diesel is renewable because it is made from grains like corn.

Another new renewable diesel fuel is Fischer-Tropsch diesel fuel. Fischer-Tropsch diesel is made from coal and natural gas today, but in the future we could make it out of grasses, trees, or anything organic.

See the following for more information:

  • Biodiesel Technology and Use (PDF 694 KB) — K. Shaine Tyson, Rocky Mountain Biodiesel. Presented at a workshop on Biomass Energy Opportunities in Indian Country; Denver, Colorado; September 15, 2004. Download Adobe Reader.

  • National Biodiesel Board — A trade association for biodiesel producers.

  • Biodiesel — In-depth information from DOE on all aspects of producing, distributing and using biodiesel.

Biofuels in Electricity Production

In recent years, there has been growing interest in using biodiesel to run backup generators for emergency power and demand response purposes (helping to meet transmission peak loads).

A principal benefit of biodiesel is reduced air emissions. Except for nitrogen oxides, which increase about 2%, emissions decline for B20 (20% biodiesel) compared to diesel. In addition, should a spill occur, biodiesel is not hazardous and degrades rapidly.

In generators, fuel consumption for B20 is comparable to petroleum diesel, although the delivery cost is about 20-30 cents higher.

As a drop-in fuel, B20 presents relatively few problems for storage tanks, fuel lines, or engines. An emissions permit will, however, be needed for standby generators when they are switched from emergency to demand response operations.

See the following for more information: