Microbial Effects on Biodiesel Fuel Properties

by Jessica Sorensen & Nestor U. Soriano, Jr.
Partly supported by NSF through the Major Research Instrumentation Grant

Growing concerns over global warming and diminishing petro fuel supplies have caused an increased interest in the use of biofuels, including ethanol and biodiesel. Biofuels are more biodegradable and produce fewer toxic emissions than petro fuels, making this renewable resource especially desirable. While biofuels are more ecologically friendly, it is known that biodiesel is more susceptible to microbial degradation than conventional diesel fuel, which can result in poor cold flow performance and filter clogging. The bacterial degradation of FAME may also have adverse effects on other fuels properties of biodiesel.

Biodiesel made from three different feedstocks including soybean, camelina and coconut were synthesized via the conventional base-catalyzed transesterification. The biodiesel samples were infected with three types of bacteria that are commonly found in soil, air and on plants. These bacteria include Pseudomonas aeruginosa, Bacillus subtilis, and Micrococcus luteus. Every two weeks a portion the individual samples will be drawn off and tested for Cold Filter Plugging Point, Cloud Point, Viscosity, Flash Point, Oxidation Stability and Acid Number based on established ASTM protocols. Gas chromatography and FT-IR analyses will be performed before bacterial inoculation, every week after inoculation and at the final week.  Monitoring of the samples will be performed for at least three months. 

Coconut, Camelina and Soybean Biodiesel

Jessica Sorensen testing a biodiesel sample for flash point at the Bio-Energy Center Fuel Chemistry Lab