BioDiesel FAQ’s

What is biodiesel made from?
Biodiesel can be made from a variety of renewable sources, such as vegetable oils (soybeans or other crops), recycled cooking grease, or animal fats. These feedstocks are used to manufacture a mixture of chemicals called fatty acid methyl esters (biodiesel).

Which feedstock is best?
Each feedstock can produce a high quality B100 fuel but with slightly different properties, especially cloud point, cetane number, oxidative stability, and NOx emissions. Cost might also factor into the selection process. Most operational differences seen with B100 are reduced when B20 is produced. Most remaining differences can be managed with additives or diesel fuel blending strategies.

Does biodiesel affect how my engine operates?
Biodiesel blends of 20% or less should not change the engine performance in a noticeable way. Some users of biodiesel blends notice significant reductions in soot, and CO and HC emissions are reduced. Higher blend levels can reduce fuel economy, torque, and power but will also produce lower PM, HC, and CO emissions. NOx may also rise with higher blend levels. Less noise and a better exhaust smell have also been noticed with biodiesel fuels.

Does using biodiesel void my warranty?
OEMs provide a material and workmanship warranty on their products. Such warranties do not cover damage caused by external conditions, such as fuel. Thus, if an engine using biodiesel experiences a failure unrelated to the biodiesel use, it must be covered by the OEM’s warranty. Federal law prohibits the voiding of a warranty just because biodiesel was used—it has to be the cause of the failure. If an engine experiences a failure caused by biodiesel (or any other external condition, such as bad diesel fuel), it will not be covered by the OEM’s warranty.

How much does biodiesel cost?
The wholesale cost of biodiesel is typically higher than diesel fuel by $1 to $2 per gallon. The size of the cost difference depends on the size of the biodiesel producer, their feedstock cost, transportation costs, production incentives, tax incentives, and other local variables. Historically, the cost of B20 has been about 20 cents per gallon higher than diesel fuel. B2 is only a few cents higher than diesel fuel.

Do I need to modify my vehicle to use biodiesel?
Based on user experience, no vehicle modifications appear to be necessary for blends of biodiesel as high as 20% biodiesel mixed with diesel fuel. Higher blend levels may require minor modification to seals, gaskets, and other parts. Tank and fuel line/fuel filter heaters (arctic packages) are recommended for blends of more than 20% biodiesel. Detailed long-term engine durability data have not been established for B20 in the United States so good maintenance practices are recommended.

Do I need to modify my dispensing equipment to use biodiesel?
Dispensing equipment does not need to be modified for blends of 20% biodiesel or lower blend levels, unless there is an issue with specific elastomers that are not compatible with B20. Occasional fuel filter plugging has been reported and some people filter the biodiesel fuels entering and/or leaving the tank. Some exposed parts of the dispensing systems may need protection from freezing in cold climates. Some people recommend tank cleaning before switching to B20 fuels.

How do biodiesel (B20 and B100) emissions compare to diesel emissions?
The EPA has conducted a comprehensive study of 80 biodiesel emission tests in CI engines that are presented in an easy to read chart in Chapter 2: Biodiesel Basics. The chart shows emission benefits for different biodiesel blend levels.

Does biodiesel use raise NOx emissions?
Blends of less than 5% do not have a measurable affect on NOx. For B20 blends, vehicle testing that is ongoing at NREL is finding no significant impact on NOx, however engine test stand studies find that B20 increases NOx emissions by about 2% over conventional diesel. However, it is possible that some B100 can raise NOx above the certification limits of CI engines. Biodiesel blends used in heating oil equipment will reduce NOx by 1% for every 1% of biodiesel used in the blend. A B20 with heating oil will reduce NOx by 20%.

Can I use biodiesel in a cold climate? 
User experience with cold weather varies. B20 blends are used in some very cold climates such as northern Minnesota and Wyoming, where temperatures routinely fall below -30°F in the winter. B20 was used in an airport shuttle fleet for four years in Boston with no problems.

Some users have reported using B100 in extremely cold climates such as in Yellowstone National Park. The vehicles were equipped with winterization packages, and no other precautions were noted. Since widespread experience with B100 and higher blends in cold climates is lacking in the United States, users should be alert to potential problems and take reasonable steps to prevent them.