Biodiesel

Biodiesel (mono alkyl esters) is a renewable liquid fuel produced from new or used vegetable oils or animal fats. A chemical process called transesterfication, which relies on an alcohol, such as methanol, and a catalyst, typically makes biodiesel. The main form of biodiesel in the United States is soydiesel, or methyl soyate, which is made from soybean oil. It can also be made from cottonseed, peanut, canola (a variety of rapeseed), sunflower oils, waste animal fats, and used cooking oil. The City of Chicago has made waste oil from restaurants into biodiesel fuel for use by the city’s transit buses and marine police boats.

The concept of using vegetable oil as a fuel dates back to 1895, when Dr. Rudolf Diesel developed the first diesel engine to run on vegetable oil. Diesel demonstrated his engine at the World Exhibition in Paris in 1900, using peanut oil as fuel. Before World War II, biodiesel was introduced in South Africa to power heavy-duty vehicles.

Recently environmental and economic concerns have renewed the interest in biodiesel throughout the world, especially in Europe, where it has been used for 20 years. Diesel-powered vehicles such as transit buses, heavy-duty trucks, and marine engines use biodiesel.

Biodiesel can be used alone or mixed in any ratio with petroleum diesel fuel. Biodiesel in its pure form is called "neat biodiesel." It is used in stationary generators in hospitals and police stations.

A number of fleets across the United States have adopted biodiesel blends. B20, a blend of 80 percent diesel and 20 percent biodiesel, is widely used in transit systems and in federal and municipal fleets such as postal vehicles, snowplows, road graders, and other highway maintenance vehicles. It is powering school bus systems in some U.S. cities and mass transit systems in national parks such as the Grand Canyon. Biodiesel blends are available in most marinas, where replacing diesel normally used in boats can help keep lakes, bays and estuaries cleaner.

France is the world’s largest producer of biodiesel, using it as heating oil and also in 50 percent blends with petrodiesel. Currently all the biodiesel used in the United States comes from domestic feedstocks. The price varies greatly depending on the type and cost of the feedstock and the scale of production. (Prices are high when biodiesel is produced in small quantities.)

A variety of people are interested in developing biodiesel and in finding better, less-expensive feedstocks. Some food producers are interested because health-conscious Americans are eating less high-oil food and biodiesel could provide another market for their products. Scientists with the U.S. Departments of Energy and Agriculture are trying to develop soybean hybrids with a higher oil content. (Soybeans contain about 20 percent oil, whereas some oil seeds contain 50 percent; rapeseed used in Europe contains 40 percent.) The National Renewable Energy Laboratory (NREAL) is researching the production of oil from aquatic plants, such as microalgea, a source that may greatly lower the cost of biodiesel.

Biodiesel can be stored anywhere that petroleum diesel fuel is stored; neat biodiesel begins to freeze at about 25° F, however, so it needs to be used or stored at temperatures above that. (Underground storage tanks are usually about 50° F.) Biodiesel has a high flash point and does not produce explosive vapors, making it safer to store and handle than diesel, but biodiesel has a shelf life of a bout six months, after which its fuel properties should be reanalyzed.

Biodiesel fuel can be distributed through the existing diesel supply infrastructure. Because it softens and dissolves some substances, fuel hoses may need modification. Biodiesel can also dissolve certain types of paints.

Neat biodiesel is biodegradable, degrading four times faster than diesel and at the same rate as dextrose (a sugar). Compared with diesel, it has substantially lower toxic, mutagenic, and carcinogenic emissions; it is relatively nontoxic to mammals.

In the late ‘90s, Yellowstone National Park conducted a "bear attraction test," successfully dispelling the notion that the french fry smell of biodiesel would attract bears to cars.

The energy content, viscosity and phase changes, horsepower, torque, and fuel economy are similar to those for conventional and low-sulfur diesel. Biodiesel has a significantly higher cetane number, a number that rates its starting ability and anitknock properties.

At higher temperature extremes, biodiesel is advantageous because its flash point is over 300° F, compared with 125° F for low-sulfur diesel and 176° F for conventional diesel. Compared with regular diesel, biodiesel is more susceptible to cold-weather fuel-flow problems. These problems can be overcome by installing engine or fuel-filter heaters, storing vehicles near or in a building, or blending biodiesel with conventional diesel.

Fueling is the same as with diesel fuel.

An engine using biodiesel requires little modification. But since biodiesel is a natural solvent that an dissolve some rubber, vehicle fuel lines and fuel pump seals that come in contact with the fuel could be affected by pure or high-percent blends. For many new cars, the recent switch to low-sulfur diesel fuel has caused most original engine manufacturers to switch to components that are already suitable for use with biodiesel. Because the fuel clouds and stops flowing at higher temperatures than does diesel, fuel heating systems may be needed in cold climates.

The use of biodiesel, even in small percentages, can extend the life of diesel engines because it is more lubricating than petroleum diesel fuel.

A 1998 biodiesel life-cycle, jointly sponsored by the U.S. Department of Energy and the U.S. Department of Agriculture, concluded that producing and using biodiesel reduces net CO2 emissions by 78 percent compared with petroleum diesel. This is due to biodiesel’s closed carbon cycle. Growing plants that are later processed into fuel recycles the CO2 released into the atmosphere when biodiesel is burned.

In the late ‘90s, Yellowstone National Park tested biodiesel by successfully driving a park truck more than 92,000 miles. Compared with diesel trucks, toxicity, emissions, smoke, and unpleasant odors were reduced; safety and biodegradability were increased.

Other tests comparing biodiesel with diesel show these results:

Carbon monoxide: 50 percent reduction

Total unburned hydrocarbons: 93 percent reduction

Ozone-forming potential due to reactive hydrocarbons: 50 percent reduction

Toxic hydrocarbons: most were reduced by 75 to 85 percent.

Nitrogen oxides: Either slightly reduced or slightly increased, depending on the engine family and testing procedures. The National Biodiesel Board reports that a 13 percent increase can be remedied through changes in ignition timing and the use of proper catalytic converter technology.

Particulate matter: 30 percent reduction

Sulfur: 100 percent reduction.

Thanks to the Northeast Sustainable Energy Association (NESEA) for providing this information.

To learn more about biodiesel, http://www.biodiesel.org/.
Easy Breathers also has a profile of biodiesel guru Joshua Tickell and his Veggie Van.