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Biodiesel
Benefits
Biodiesel is a domestically produced, clean-burning, renewable substitute for petroleum diesel. Using biodiesel as a vehicle fuel increases energy security, improves public health and the environment, and provides safety benefits.
Emissions
Compared with using petroleum diesel, using biodiesel in a conventional diesel engine substantially reduces emissions of unburned hydrocarbons (HC), carbon monoxide (CO), sulfates, polycyclic aromatic hydrocarbons, nitrated polycyclic aromatic hydrocarbons, and particulate matter (PM). The reductions increase as the amount of biodiesel blended into diesel fuel increases. B100 provides the best emission reductions, but lower-level blends also provide benefits. B20 has been shown to reduce PM emissions 10%, CO 11%, and unburned HC 21% (see graph). Learn more about Biodiesel Emissions.
Average emission impacts of biodiesel for heavy-duty highway engines (Source: U.S. Environmental Protection Agency, A Comprehensive Analysis of Biodiesel Impacts on Exhaust Emissions (pdf).
Using biodiesel also reduces greenhouse gas emissions because carbon dioxide released from biodiesel combustion is offset by the carbon dioxide sequestered while growing the soybeans or other feedstock. B100 use reduces carbon dioxide emissions by more than 75% compared with petroleum diesel. Using B20 reduces carbon dioxide emissions by 15%.
Manufacturing
Biodiesel can be produced domestically and used in conventional diesel engines, directly substituting for or extending supplies of traditional petroleum diesel. (Remember to consult with your auto manufacturer and engine warranty statement before using biodiesel in your vehicle.) It also has an excellent energy balance: biodiesel contains 3.2 times the amount of energy it takes to produce it.
Biodiesel can be made from new or used vegetable oils and animal fats, which are nontoxic, biodegradable, and renewable. Fats and oils are chemically reacted with an alcohol (methanol is most commonly used in the United States) to produce chemical compounds known as fatty acid methyl esters. Biodiesel is the name given to these esters when they are intended for use as fuel. Glycerin (used in pharmaceuticals and cosmetics, among other markets) is produced as a co-product.
Biodiesel can be produced using a variety of esterification technologies. The oils and fats are filtered and preprocessed to remove water and contaminants. If free fatty acids are present, they can be removed or transformed into biodiesel using special pretreatment technologies. The pretreated oils and fats are then mixed with an alcohol (usually methanol) and a catalyst (usually sodium hydroxide). The oil molecules (triglycerides) are broken apart and reformed into methyl esters and glycerin, which are then separated from each other and purified.
Enough virgin soy oil, recycled restaurant grease, and other feedstocks are readily available in the United States to provide feedstock for about 1.7 billion gallons of biodiesel per year (under policies designed to encourage biodiesel use). This represents roughly 5% of on-road diesel used in the United States.
Safety
Biodiesel is nontoxic, so it causes far less damage than petroleum diesel if spilled or otherwise released to the environment. It is also safer than petroleum diesel because it is less combustible. The flashpoint for biodiesel is higher than 150°C, compared with about 52°C for petroleum diesel. Biodiesel is safe to handle, store, and transport.
Costs
Just like gasoline prices, the cost of biodiesel fluctuates. For the latest biodiesel price analysis, see the Alternative Fuel Price Report.
Availability
Biodiesel is distributed from the point of production via truck, train, or barge. Pipeline distribution of biodiesel, which would be the most economical option, is still in the experimental phase. Biodiesel is distributed to retail fueling stations and directly to end users such as large vehicle fleets. Most biodiesel distributors will deliver pure or pre-blended (with petroleum diesel) biodiesel depending on the customer's preference. For more information, see the National Biodiesel Board's Guide to Buying Biodiesel.
Biodiesl Fueled Vehicles in DAS Fleet
- Chevrolet Silverado
- Ford F250
- Ford F350
- Ford F450
- Ford F550
- Freightliner Sprinter
- Dodge Ram
- Dodge Sprinter
- Volkswagen Jetta TDI
Source: US Department of Energy, Energy Efficiency and Renewable Energy, Alternate Fuels & Advanced Vehicles Data Center: http://www.afdc.energy.gov/afdc/
Updated: 02/12/2009
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