Alternative fuels have dominated the headlines recently. Everywhere you look the debate on alternative energy sources rages on.
One of those alternative energy sources is biodiesel, and as in any debate, there has been much information and some misinformation generated on the topic. Simply put, biodiesel is an alternative fuel that is produced from renewable resources. It is derived from either plant or animal oils, which are processed to produce biodiesel. Pure biodiesel contains no petroleum, is biodegradable, nontoxic, and is effectively free from sulfur.
There is some confusion as to what can be called biodiesel. Is raw vegetable or animal oil the same as biodiesel? No. Biodiesel has been extensively tested for health and performance characteristics and is registered with the Environmental Protection Agency (EPA) as legal motor fuel. Fuel-grade biodiesel must be produced to meet stringent standards (ASTM D6751) to ensure proper performance.
In the field, biodiesel is most commonly blended with petroleum diesel, and labeled with a B and its biodiesel percentage. For example, B2 would be representative of a mixture containing 2 percent biodiesel and 98 percent petrodiesel. Most of the time, biodiesel in a B20 or lower blend can be used in compression ignition (diesel) engines with little or no modification.
The modern diesel engine boasts technology and complexity that would have been hard to imagine just 10 years ago. Fuel delivery systems in particular have seen sweeping changes in system pressures and mechanical tolerances. Combine this with diesel fuel that has been stripped of its lubricating properties during the removal of sulfur so that it meets tough new regulations, and the potential for greatly accelerated injector wear and premature failure increases. Laboratory studies have shown conclusively that biodiesel in concentrations as low as B2 can replace these lost lubricants and negate the potential for accelerated fuel system wear.
When preparing to convert to biodiesel blend it is important to be aware of the fact that biodiesel has a "solvent" quality which will result in the cleansing of the fuel delivery system. This typically translates to temporarily changing fuel filters more often as the system flushes accumulated contaminants. The duration of this process is dependent on the overall cleanliness of the fuel system. The amount of hours/miles the system has been in use, and the quality of fuel and the level of preventative maintenance the system has seen, are both contributing factors. After the initial clean-up, fuel filter service intervals will return to normal.
Biodiesel also has a higher cloud and pour point than petrodiesel, which impacts its usability in cold climates. Additionally, biodiesel has eight percent less energy in its pure form than petroleum diesel. Both of these factors are mostly negated when biodiesel is blended with petrodiesel.
As biodiesel use has increased, there have been growing quality concerns due to higher percentage levels of biodiesel and the many different sources of the fuel. In fact, in June ASTM International's D02 Main Committee approved changes to the existing B100 biodiesel blend stock specification (ASTM D6751); specifications to include up to five percent biodiesel (B5) in the conventional petrodiesel specification (ASTM D975); and a new specification for blends of between six percent biodiesel (B6) to 20 percent biodiesel (B20) for on- and off-road diesel.
There also is some debate on the effects higher levels of biodiesel blends and different biodiesel sources will have on engines, and the industry is continuing to research these questions.
Today, biodiesel is still primarily used in large commercial and government fleets, while distribution challenges continue to make it tough on the individual to capitalize on the benefits of biodiesel. On the positive side, as long as the industry stays at a B20 blend or below, no new changes to engines will be needed, even for meeting the 2010/2011 emissions standards.
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