GUIDELINES FOR BIODIESEL USAGE

Quality Control
Biodiesel users should always ensure that the biodiesel used in their fuel blends meets the latest ASTM D6751 specification. ASTM D6751 is based on the physical and chemical properties needed for safe and satisfactory diesel engine operation. This specification ensures the quality of biodiesel.

Storing Biodiesel Fuels
Biodiesel is best stored in tanks that do not have any residual water, sediments or other contaminants. Heat and sunlight can accelerate oxidation; therefore storage in clear totes is not advisable. Biodiesel made from feedstock high in saturated fats, i.e. Palm Oil or Tallow, tends to oxidize slower, and consequently has higher storage stability. Exposure to oxygen reduces the storage life of biodiesel fuels.

In general, B20 tends to have a longer storage life than B100. The National Biodiesel Board recommends that B20 blends be used within six months, which is comparable to current practices recommended for conventional diesel. When storing biodiesel for longer periods, the use of nitrogen blankets and anti-oxidants and/or stability additives is suggested. Since the acid level and viscosity can increase as biodiesel ages in storage, users can also perform acid number and viscosity tests before using biodiesel fuels that have been stored for lengthy periods.

Cold Weather Performance
Unlike gasoline, conventional diesel can start to gel as temperatures drop substantially. Biodiesel fuels also have cold weather performance limitations, but these limitations are more severe when using a pure biodiesel B100 fuel.

The potential for cold flow problems in biodiesel fuels can be moderated by dilution via blending with conventional diesel, which also makes the use of cold flow additives practical. Thus, a B5 fuel will generally have very few cold flow issues beyond that normally experienced with conventional diesel fuel. B20 typically has a cloud of point 10-20° F and a pour point of 5-15° F above conventional diesel. When using B20 in below freezing temperatures, cold flow performance can be managed by i) using cold-flow additives, ii) ensuring that the conventional diesel used in the blend is a ‘winter diesel’ that has a sufficiently low cloud point, i.e. some winter diesel blends achieve very low cloud points by including No. 1 diesel. However, at biodiesel levels above 20%, managing cold flow performance can be a more significant challenge and may require engine block or fuel filter heaters.

Managing the Solvent Effects of Biodiesel in Engines
Biodiesel in its pure form (B100) is a solvent, and may loosen and/or dissolve sediments in fueling systems that are left by conventional diesel fuel over time. Thus, when first using biodiesel fuel, particularly if using a B20 or higher blend, users may experience fuel filter plugging upon the first few weeks of use. It is recommended that biodiesel users monitor their filters for plugging more closely during initial use. The potential for fuel filter plugging typically goes away after the first few tanks of fuel. Some users of B20 or higher blends will take the precautionary measure of changing the fuel filters after consuming the first or second tank of fuel.

B100 is not compatible with certain hoses and gaskets because it can degrade certain types of rubber compounds, causing leaks or total inoperability. Likewise, B100 may over time permeate some types of plastics such as polyethylene or polypropylene.

Older vehicles manufactured before 1993 are more likely to contain seals, gaskets, etc. that will be affected by B100 over long periods of time. B100 is also not compatible with some metals (i.e. brass, bronze, galvanized metal surfaces), which can result in the formation of high levels of sediment. B20 or lower biodiesel blends minimize most issues associated with material compatibility. According to the U.S. Department of Energy, "Experience over the last 10 years with B20 indicates compatibility with all existing elastomers in diesel fuel systems, even those that are sensitive to higher blends [of biodiesel] such as nitrile rubber1."

Engine Warranties
Using biodiesel fuel only impacts the warranty as it relates to fuel related problems directly attributed to biodiesel. According to the U.S. Department of Energy, "Federal law prohibits, the voiding of a warranty just because biodiesel was used – it has to be the cause of the failure2." Most OEM dealers and customer service departments currently tell their customers that 5% biodiesel blends (B5) are acceptable, with the requirement that the pure biodiesel used in the fuel blend adheres to ASTM D6751. There are some OEM’s who tell their customers biodiesel blends up to B20 are acceptable, while others say anything up to B100 is acceptable. For an updated list of OEMs and their position on warranty coverage for biodiesel usage, visit the National Biodiesel website at: http://nbb.org/resources/fuelfactsheets/standards_and_warranties.shtm.