Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
Civics & Politics The Environment Health Economics Social Issues Full Archive
NOW on Demand
Week of 1.12.07

Biodiesel 101

Below are answers to basic questions about biofuels, including biodiesel and ethanol. This information was collected a variety of sources, including the Department of Energy.

Biodiesel sample
Biodiesel sample
What is biodiesel?
Biodiesel is the name of a cleaner burning, alternative kind of diesel fuel. Biodiesel is made from organic sources, such as vegetable oils extracted from soybeans, sunflowers, and canola. Those vegetable oils are refined in a way that allows them to be used in a diesel engine. Biodiesel can be used in diesel cars and trucks either in its pure form, or be blended with regular petroleum diesel. Diesel vehicles using pure biodiesel require some slight modification. Vehicles using the blend do not. There's more on that distinction later in this fact sheet. Unlike regular diesel fuel, pure biodiesel is biodegradable and largely non-toxic.

If you're interested in modifying your vehicle to use the pure form of biodiesel, more information can be found here. But remember, if you use the blend, no modification may be required.

When was biodiesel first used?
Vegetable oil was used in diesel fuel as early as 1900. The inventor of the diesel engine, Rudolf Diesel, originally designed the engine for use with peanut oil. The production of biodiesel processes the oil to make it more acceptable to modern diesel engines.

How is biodiesel different than ethanol?
Both biodiesel and ethanol are biofuels, but biodiesel may only be used in diesel-running engines, while ethanol can be used in most gasoline burning engines. While both biodiesel and ethanol are made from renewable resources, biodiesel is made from vegetable oils from soybeans, sunflowers and the canola plant while ethanol is made in one of two ways: corn-based ethanol is made from corn crops, while cellulosic ethanol is produced from materials like switch grass or wheat straw.

How many cars use ethanol?
According to, approximately four million cars currently on the road in the United States are already compatible with E85, a blend of 85 percent ethanol and 15 percent gasoline, with more being created every year. Also, gasoline-powered cars can run on a 10 percent ethanol/90 percent gasoline blend. The state of Minnesota, in fact, requires that all gasoline sold there is of that balance. Most auto manufacturers only guarantee their warranty services on regular/non-flex-fuel cars for up to 10 percent blends.

To see if your car or truck can take ethanol, consult the list here

How do the benefits of ethanol and biodiesel compare?
According to the National Academy of Sciences, biodiesel produces more usable energy and reduces greenhouse gases more than corn-based ethanol.

Is biodiesel used as a pure fuel or is it blended with petroleum diesel?
Biodiesel contains no petroleum, but, like ethanol, it can be blended at any level with petroleum diesel in any percentage to create a biodiesel blend. Biodiesel containing no petroleum is called "Neat" biodiesel. In reference, biodiesel is designated by the letter B and a number representing the percent of the fuel that is biodiesel. The rest of the fuel is petroleum diesel. For example, a mixture of 20% biodiesel and 80% petroleum diesel, a commonly used ratio, would be labeled B20. B20 has demonstrated significant environmental benefits with a minimum increase in cost for consumers.

Is biodiesel production efficient?
Biodiesel actually has the highest "energy balance" of any transportation fuel. For every unit of fossil energy it takes to make biodiesel, 3.2 units of energy are gained, making it one of the most efficient alternative fuels.

Is biodiesel approved for use in the U.S.?
Biodiesel is registered as a fuel and fuel additive with the Environmental Protection Agency (EPA) and meets clean diesel standards established by the California Air Resources Board (CARB). Neat (100 percent) biodiesel has been designated as an alternative fuel by the Department of Energy (DOE) and the U.S. Department of Transportation (DOT). Additionally, biodiesel is the only alternative fuel to have fully completed the health effects testing requirements of the Clean Air Act.

Biodiesel can be made from soybean oil
Biodiesel can be made from soybean oil
Is biodiesel good for the environment?
Biodiesel is as biodegradable as sugar and ten times less toxic than table salt. This makes biodiesel ideal for use in environmentally sensitive areas. Additionally, biodiesel reduces net CO2 emissions by 78 percent, according to a 1998 biodiesel lifecycle study, jointly sponsored by the U.S. Department of Energy and the U.S. Department of Agriculture. This is because the CO2 released into the atmosphere when biodiesel is burned is recycled by growing plants, which are later processed into fuel. Biodiesel also reduces tailpipe exhaust emissions, minimizing black smoke and smog-causing particulate matter, odor, and harmful carcinogens. It also does not contribute to sulfur dioxide emissions (acid rain). Even 20% biodiesel blended with petroleum (B20) has demonstrated significant environmental benefits with a minimum increase in cost for consumers.

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 potentially carcinogenic compounds.

How does biodiesel performance compare to diesel fuel?
Biodiesel shows similar fuel consumption, horsepower, torque and haulage rates as conventional petroleum diesel fuel. In cold weather, however, it will gel, just as the common #2 diesel does. However, blends of 5% biodiesel and less have virtually no impact on cold flow.

Who's using biodiesel?
Biodiesel is widely used and available at the pumps in Europe and is rapidly gaining popularity in North America as an environmentally-friendly alternative to petroleum diesel. Currently, the key markets for biodiesel are mass transit, marine use, and usage in environmentally sensitive areas.

What is the cost of biodiesel?
While biodiesel is more expensive than other petroleum-based fuels, conventional fuels do not have the same conservation, energy security, environmental, and economic benefits as biodiesel. Low level blends of biodiesel (B5) are about the same cost as conventional diesel. In a B20 blend, biodiesel typically adds less than one cent per liter to the cost of the fuel.

How much biodiesel is currently being used?
The National Biodiesel Board, an industry group, reports that biodiesel sales in the United States have increased from 500,000 gallons in 1999 to 75 million gallons in 2005.

What are some other advantages of Biodiesel?
  • It reduces our dependence on a 100% imported fuel source.
  • Biodiesel is safer to handle and transport than petroleum.
  • Biodiesel fuel can generally be used in existing diesel engines and oil heating systems without modification, and it can be distributed through existing diesel fuel pumps. This is an advantage over other alternative fuels, which can be expensive to use initially due to high cost of equipment modifications or new purchases.
  • Biodiesel is an economic way to utilize the surplus of soybeans in the United States.

What are some disadvantages of biodiesel fuel?
  • Biodiesel is currently about one and a half times more expensive than petroleum diesel fuel. Part of this cost is because the most common source of oil is the soybean, which only is only 20% oil.
  • It takes energy to produce biodiesel fuel from soy crops, including the energy of sowing, fertilizing and harvesting.
  • Biodiesel fuel can damage rubber hoses in some engines, particularly in cars built before 1994. You should check with the manufacturer before using biodiesel to see if you need to replace any hoses or rubber seals.
  • Dirt cleaned from the engine and tank through the use of biodiesel collects in the fuel filter, which can clog it. Clogging occurs most often when biodiesel is first used after a period of operation with petroleum diesel, so filters should be changed after the first several hours of biodiesel use.
  • Biodiesel is not distributed as widely as traditional, petroleum diesel.
  • 100 percent biodiesel can't be used in winter because it becomes too thick in cold temperatures.