REG, Kemin partner in biodiesel oxidation study

By Anna Austin | February 10, 2009
Biodiesel producer Renewable Energy Group Inc. and antioxidant solution specialist Kemin Industries Inc. are analyzing test results gathered through a research collaboration that served to gain a better understanding of how to cost-effectively maintain biodiesel quality during storage.

For 10 weeks, the Iowa-based companies observed the oxidative stability characteristics in B100 made from soybean oil, and B100 made from a combination of vegetable oil and animal fats, all of which were provided by REG.

Biodiesel may initially possess oxidative stability, but the oxidation process begins immediately after production, and leads to the formation of low molecular weight acids, insoluble gums and other undesirable byproducts.

In tests simulating extreme storage conditions, oxidative stability decreased rapidly in untreated B100 as measured by the oil stability index's induction time, peroxide value, and 1,4-decadienal and hexanal content. When an antioxidant was added to B100, it appeared to ensure the integrity of the fuel throughout the fuel supply chain when stored for long

periods of time or in less-than-ideal situations.
Glen Meier, REG manager of research and development, said antioxidant treatment successfully delayed the oxidation. "Results show that dosage rates will depend on the specific biodiesel product and its feedstock composition, as well as the storage and handling protocols in place," he said.

Although results are only preliminary so far, the group determined that late "rescue" treatments did not eliminate the need for secondary oxidation products, even though the oil stability index's induction time increased. In addition, oxidation in the measured products indicated changes to B100 that may foster polymer and sediment formation in blends, suggesting the earlier use of antioxidants to preserve quality. "One of the goals in this long-term research collaboration is to help petroleum distributors prevent oxidative stability issues when handling or storage situations are not ideal," said Jennifer Radosevich, Kemin vice president of research and development. "Kemin has created an economically viable additive that can be added to B100 at the production facility to improve oxidative stability."

The study is Kemin's first in the biodiesel industry. The relationship between REG and Kemin began at the Iowa Biofuels Expo, part of the 2007 Norman E. Borlaug International Symposium in Des Moines, Iowa. The theme of that year's symposium was "Biofuels and Biofoods: The Global Challenges of Emerging Technologies," and REG organized the expo.

The two companies plan to continue the partnership to further understand oxidative stability, and to conduct educational and promotional activities with petroleum distributors and biodiesel consumers.

In similar research, the National Institute of Standards and Technology recently developed a method to accelerate the oxidative stability testing of biodiesel fuel made from soybeans and also identified additives that enhance stability at high temperatures. The paper, titled "Stabilization of Biodiesel Fuel at Elevated Temperature with Hydrogen Donors:
Evaluation with the Advanced Distillation Curve Method," concluded the method can be used to assess the combined thermal and oxidative stability of sensitive fluids such as biodiesel. Researchers used the method to test three hydrogen donor molecules for use as potential stabilizers for biodiesel.
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