Tech Tips
Biodiesel At-A-Glance
Many fleets across the country and internationally have been using biodiesel blends as part of their fueling options for several years, while some fleets are still in the process of considering its use. There are many compelling reasons to consider the use of biodiesel, among which are that it is renewable, displaces the use of petrodiesel, and reduces global warming gas emissions. Here is a primer on biodiesel as a vehicular fuel, with a focus on the use of the blend called B20. The primary sources for this information are the U.S. Department of Energy and the National Biodiesel Board.
Biodiesel: What It Is and How It’s Made
Biodiesel is a renewable fuel manufactured from vegetable oils, animal fats or recycled cooking oils. Biodiesel is manufactured by converting these oils and fats into mono alkyl esters or fatty acid methyl esters (FAME). The process includes having the oils or fats react with an alcohol, usually methanol, in the presence of a catalyst. The result is biodiesel (B100), with glycerin as a co-product. B100 is used as a vehicular fuel in some applications, but most often it is used as a fuel in a blend with petrodiesel.
Biodiesel Standards
ASTM International is an organization whose standards are recognized by most governmental entities. ASTM D6751 is the specification for B100. Any and all biodiesel used for blending should meet this standard. Biodiesel is a legally registered fuel with the U.S. Environmental Protection Agency, which stipulates that all B100 meet this ASTM standard.
The biodiesel industry has developed the BQ-9000 program, which is a voluntary quality assurance program for producers and distributors to help ensure that biodiesel meets the ASTM specifications and that contamination or degradation does not occur during distribution, storage or blending. It is highly advised that biodiesel purchases are made from accredited producers and certified marketers. There are currently 19 accredited producers and seven certified marketers.
According to the National Biodiesel Board (NBB), the regulation of standards for biodiesel and blends is primarily left to each state and varies from one state to another. The NBB’s website includes a catalog of information about each state’s authority to regulate fuel standards, their status in adopting ASTM D6751 as the fuel specification for biodiesel, and enforcement procedures.
Biodiesel Benefits
There are many benefits to using B100 or any blend of biodiesel. Because biodiesel contains oxygen, it burns more completely, reducing hydrocarbon, particulate matter, and carbon monoxide emissions. Biodiesel also improves the lubricity of diesel fuels.
B20, a blend of 20% biodiesel and 80% petrodiesel, is the most commonly used biodiesel blend in the United States today for several reasons. As opposed to other blends, B20 achieves a balance of cost, emissions, cold weather performance, materials compatibility, and solvency. In addition, B20 is easy to use – it can be stored in diesel fuel tanks and pumped with regular diesel fueling equipment. Finally, especially important to many fleets, B20 is the minimum blend allowed for the Energy Policy Act of 1992 (EPAct) compliance.
Biodiesel Drawbacks
There are a few drawbacks to using biodiesel. Because it is denser than diesel fuel, B100 contains 8% less energy per gallon than No. 2 diesel. This impact is minimal when using B20 – the difference in power and fuel economy is statistically insignificant. In addition, biodiesel can start to gel or freeze at lower temperatures. This can cause filters to clog and, in the most severe case, prevent the fuel from being pumped to the engine. Finally, although there are conflicting results, some studies have shown an increase in nitrogen oxide emissions for biodiesel.
Using B20
Cold flow properties usually cause the largest concern for blenders, as well as users. The cold flow properties of B20 will vary with the composition of the biodiesel and the diesel fuel, as well as with the effectiveness of any cold flow additives that may be used. Although it typically costs more, using No. 1 diesel (kerosene) as a portion of the diesel in the blend lowers the overall cloud points. Cold flow additives, which inhibit or reduce the size of crystal formation work, but vary in their effectiveness.
For B20 purchased from petroleum distributors, distributors should take care of ensuring the proper blend and that cold flow properties are appropriate for the climate. Users often include specifications in their purchase contracts to address these concerns.
If you blend your own fuel, it is important to review guidelines included in literature on this subject. Just a few of the key considerations include the need to test the blended fuel to ensure it is thoroughly mixed and to consider the various temperatures in the blending process and during storage.
It is extremely important that B20 be stored in thoroughly clean tanks. Water and other contaminants must be removed. This is especially important for biodiesel produced from recycled cooking oils.
Filters should be checked for at least the first 6 months of biodiesel use. If filters clog more frequently with B20 than with petrodiesel, the fueling system should be checked for oxidizing metals, e.g. brass, bronze, or copper, or galvanized surfaces. These metals cause biodiesel to degrade more quickly and the sediment may cause filters to clog. Diesel systems do not usually contain these metals, but on occasion are found in them.
It is recommended that B20 be used within six months, according to the National Biodiesel Board. Stability additives are available for situations when long-term storage is a concern. As biodiesel ages, the acid increases which may cause gums and varnish to form and viscosity to increase.
Vehicle Warranty Issues
Federal law prohibits a warranty being voided just because biodiesel was used. Biodiesel has to be shown as the cause of the failure. If, however, an engine fails because of biodiesel, the original equipment manufacturer’s warranty will not cover the damage. The damage should be covered by the fuel supplier’s general liability insurance. The same is true with any fuel, including petrodiesel. Biodiesel users should ensure that suppliers provide this coverage.
Although biodiesel is exempt from some states’ excise taxes, it is not exempt from federal excise taxes. There are some biodiesel incentives, as well as tax credits available. The most prominent is a federal excise tax credit that makes biodiesel more affordable.
Sources for more information:
ATTEND AFVi’s Biofuels Drive Economic Solutions one-day Forum
September 20, at The Orleans Hotel in Las Vegas, Nevada
For more information or to register, click here.
Biodiesel Handling and Use Guidelines
DOE/GO-102006-2358, Third Edition, September 2006 www.nrel.gov/vehiclesandfuels/npbf/feature_guidelines.html
The National Biodiesel Board
www.biodiesel.org
U.S. Department of Energy
www.eere.energy.gov
U. S. Environmental Protection Agency
www.epa.gov
BQ-9000
www.bq-9000.org
Your local Clean Cities representative
Check for one in your area at
www.eere.energy.gov/cleancities/coordinators.html
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