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Stabilizing force

Marshall, Minn. — Antioxidants not only keep humans healthy, they could extend the life of biodiesel.


As part of an alternative-fuel evaluation, AURI chemist Ranae Jorgenson tested various soybean oiland biodiesel samples to determine shelf life — how long they could be stored before breaking down. “Fuel breakdown will affect performance,” Jorgenson says. “As renewable-fuel standards call for increased use of biodiesel, long-term stability needs to be addressed.” Jorgenson evaluated oxidative stability, fatty acid composition, calculated iodine value, calculated free fatty acid and moisture. The biodiesel and oils were tested for six months, the maximum length that fuels are typically stored. Jorgenson added tertiary-butylhydroquinone (TBHQ), an antioxidant stabilizer, to some of the samples. Stabilizing agents are generally added to fuels by refiners, not consumers.

“The addition of stabilizing agents in both the oils and biodiesel significantly inhibited degradation,” and may increase the length of optimal use, Jorgenson says.

“Untreated oils can be highly oxidative,” says Max Norris, AURI director of projects and technology. “The use of TBHQ has been promoted in the industry and these tests confirm that it works. That’s important because we want to ensure that vehicle performance won’t be impacted when consumers use biodiesel.”

Shelf-life testing results will be presented at the American Oil Chemists Society annual meeting in Seattle, Wash. in May.