Cummins Inc. has approved the use of B20 biodiesel blends in its 2002 and later emissions-compliant ISX, ISM, ISL, ISC and ISB engines. This includes the recently released 2007 products.
Cummins’ previous position on the use of biodiesel fuel was limited to the use of B5 blends only. Cummins upgraded to B20 for three main reasons. First, the American Society of Testing Materials specification ASTM D6751 now includes an important oxidation stability specification for B100 biodiesel.
Biodiesel fuels are subject to instability due to a natural oxidation process, involving a free radical chain reaction that continues until the reactive molecular links or available oxygen are depleted.
During the first steps of fuel oxidation, peroxides (hydroperoxides) form. At high concentration, these reactive oxidizing agents can damage or degrade certain plastics and elastomers, particularly at higher temperatures. Subsequent steps in the oxidation process produce acids, gums, polymers, and other insoluables that can block fuel filters.
The latest version of the standard—ASTM-D6751-07—includes an oxidative stability lower limit of 3 hours, tested by the EN14112 method, using the Rancimat or similar instrument.
The standard also has a lower acid number of 0.5 mg/KOH, down from the previous limit of 0.8 mg/KOH. The acid number is a measure of free fatty acids (FFA), which are products of the natural degradation of fats and oils. The acid number is an indicator of the initial quality of biodiesel fuel, as well as a level of fuel oxidation.
Acid number measurements greater than 0.8 mg/KOH have been associated with biodiesel that has caused fuel system deposits and reduced the operating life of fuel pumps and filters.
Cummins’s second reason is the rapid growth in the availability of quality fuels from BQ-9000 Certified Marketers and Accredited Producers is growing rapidly. Third, Cummins has completed the necessary testing and evaluations to ensure that customers can reliably operate their equipment with confidence using B20 fuel.
Recent studies predict that, by 2008, 1.2 billion gallons of B100 biodiesel will be produced in the United States. Cummins says that it will continue its efforts to ensure that future products will be compatible with biodiesel fuels, and will continue to participate in industry efforts aimed at the development of consistent quality throughout the biodiesel industry.