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Biodiesel Basics

05/07/2014 @ 11:35am

Biodiesel roots grow deep in the soil of American farms. Yet, despite this passion, there is a great deal of misinformation being disseminated about the fuel.

One of those misconceptions is that it always contains some level of petroleum. The amount of biodiesel in fuel is identified alphanumerically (the letter B and a number). B100 is pure biodiesel and may also be identified as neat. B20 is a blend of 20% biodiesel and 80% petroleum-based diesel. 

What is unique about biodiesel is that it is manufactured instead of refined. The majority of biodiesel is made from soybeans, but it can be made from other grain stocks, oils, or fats.


The soybean is crushed and yields approximately 80% high-protein meal and 20% oil (used for biodiesel). Soybean-based biodiesel is also very efficient; it returns 5.5 units of energy for every 1 unit consumed.

Another misconception is that burning biodiesel requires engine modifications. In fact, it is so similar to petroleum diesel that blends of up to B20 work in any engine with no modification. B100 may require modifications to the fuel-delivery system since it has the ability to degrade rubber lines and gaskets. These need to be replaced with Viton-made parts.

Due to the federal government’s renewable energy mandate, most No. 2 diesel sold at a pump or in bulk is actually B5. This would be akin to the mandate for gas to include 10% ethanol.


What becomes confusing is that you cannot group a biodiesel blend into the same category as B100. This is the major cause of bad information. In your area, there may be blends from B5 to B100 and anything in between.

Biodiesel advantages
Biodiesel has a number of advantages over conventional fuels, which include:

  • High lubricity even in blends with as little as 2%.
  • An energy content that is between 118,170 and 127,042 Btu per gallon. This is similar to #1 diesel, but it is slightly less than #2 fuel.
  • A high cetane rating. B100 is a minimum of 50 cetane compared to a national average of 40 cetane for conventional diesel. 
  • Reduction in emissions. In fact, on newer EPA tier-rated engines, biodiesel provides more efficient conversion of pollutants in exhaust system-based controls.

Good practices
Biodiesel has a natural cleaning action and will remove gunk and varnish from fuel storage facilities, equipment fuel tanks, and the engine’s fuel system. 

When switching to biodiesel, it is best to change all fuel filters (engine and storage tank), and then change them again at one half the normal interval. Follow this protocol for two filter changes, and then a normal petro-diesel fuel filter routine can be employed.

If your on-farm storage tank has a good deal of deposits from years of use, it would be wise to have it cleaned prior to the delivery of B20 or higher blends.

Biodiesel pitfalls
One pitfall to B100 is that it is too easy to make a poor-quality product. Inferior biodiesel has given the fuel a black eye in many cases. The fuel you purchase must always meet the ASTM standard 6571-12 and needs to be registered in the BQ-9000 Fuel Quality Program. Before purchasing any biodiesel fuel or blend from a bulk supplier, have it provide proof of meeting these standards. 

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