[edit] Biodiesel | Alternative Fuel | Diesel
Biodiesel is a type of alternative fuel which is produced through the transesterification of vegetable oils or other natural oils. This process removes the glycerin from the oil and leaves behind pure biodiesel, also known as methyl esters. This type of fuel can be used in modified diesel engines, or in a blend with regular diesel fuel in standard diesel engines. The maximum recommended ratio of biodiesel to petroleum diesel than can be used in standard diesel engines is 20%. This type of fuel is referred to as B20. B100 is pure biodiesel, although sometimes 1 percent petroleum diesel is added as an anti-mold agent to produce B99.
[edit] Applications And Environmental Impact
The use of biodiesel in the United States has more than doubled in the past 3 years. There are several reasons for its popularity. Many blends of biodiesel can be less expensive than standard diesel, making it a good choice for fleets, such as buses or city vehicles. Municipalities also appreciate the fact that pure biodiesel and biodiesel blends produce cleaner emissions than conventional diesel fuels, with B100 fuel releasing no sulfates and significantly less unburned hydrocarbons, carbon monoxide and particulate matter. Sulfur gas is a major component required to create acid rain. Biodiesel does however produce up to 10% greater emissions of nitrogen oxide. This can require some vehicles to be outfitted with specific catalytic converters in order to reduce the release of this gas.
Biodiesel is the only form of alternative fuel which has undergone complete EPA testing in terms of emissions and health effects as required by the Clean Air Act amendments of 1990.
[edit] Performance
The performance of biodiesel as a fuel compares favorably to traditional diesel. In the United States, the cetane number of biodiesel fuel, which is the ability of the fuel to resist knock (the diesel equivalent of octane) is higher than that of petroleum diesel. Extensive testing has revealed that biodiesel fuel produces almost identical performance numbers when compared to petroleum diesel in the same engines. Fuel economy is also comparable. Biodiesel has the additional advantage of increased lubricity over traditional diesel, up to 65% greater even with conservative biodiesel blends. This better lubricity can translate into less engine wear over the life of the vehicle. Since a diesel engine remains mechanically identical regardless of which type of fuel it is running, it is not necessary to stock any special parts or learn new techniques in order to service and repair engines using biodiesel.
[edit] Special Requirements To Run Biodiesel
The modifications to run pure B100 fuel are not extensive. Biodiesel is capable of eating away at some types of rubber compounds and other elastomers (plastic and other elastic fittings). This means that in certain engines, it is necessary to refit fuel delivery tubing, gaskets and seals with more modern materials. Recent diesel engines do not usually have these issues, since the lowered sulfur content in American diesel fuel has required that these changes be made from the factory. B20 fuel does not require any engine modification and can be run in any type of diesel engine.
[edit] Downsides To Biodiesel
B20 grade biodiesel can be slightly more expensive than regular diesel fuel by as much as 3 cents per gallon. For fleet managers, this extra cost can add up quickly. For B100 grade biodiesel, the catalytic converters required to reduce nitrogen oxide emissions can also add an extra cost to each vehicle.
In cold climates, biodiesel falls victim to the same types of issues that surround regular diesel engines. One such problem encountered during cold weather diesel operation is fuel gelling, which can lower viscosity. B20 blends can increase the temperature at which diesel begins to experience negative effects from the cold by between 2 and 10 degrees Fahrenheit. B100 fuel may require petroleum diesel blending in order to remain useable at similar temperatures, and fuel-tank heating may be necessary to improve B100 performance in these situations.
[edit] The Future Of Biodiesel
The continued use of biodiesel in medium to heavy vehicles looks to be assured, thanks to the pressures of reducing emissions in urban environments and the tax incentives offered by the federal and state governments to use this type of alternative fuel. Most of the extra costs associated with using certain biodiesel blends are made up for via these tax breaks. In addition, more modern diesel engines include pollution equipment already designed to reduce nitrogen oxide emissions, removing the expense of installing extra catalytic converters. Biodiesel is still in its infancy in terms of fuel additive development, and new additives which promise to increase efficiency and further reduce emissions are on the horizon.
From a passenger car perspective, the industry has been slow to embrace the use of biodiesel, although Chrysler has released several common-rail diesel engine vehicles which are advertised as being compatible with B5 blends. Private conversion to biodiesel is inexpensive and easy, and many older diesel cars are being given new life through conversion to this alternative fuel.
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