CHARACTERIZATION OF FUNGAL CONTAMINANTS IN B20 BIODIESEL STORAGE TANKS AND THEIR EFFECT ON FUEL COMPOSITION

Abstract

The liquid transportation fuel B20 biodiesel is an 80:20 blend of petroleum-derived ultra-low sulfur diesel (ULSD) and biodiesel. Although B20 biodiesel represents a fungible fuel with a reduced carbon footprint compared to petroleum diesel, it is more susceptible to microbial contamination and biodegradation. The research described in this thesis characterized the numerically abundant fungi responsible for fouling in B20 biodiesel storage tanks. This work also investigated the effect of microbial contamination and proliferation on B20 biodiesel composition. Fungi from the genera Wickerhamomyces and Byssochlamys were abundant in the B20 storage tanks that were monitored in this study. Members of the yeast Wickerhamomyces anomalus SE3 and the filamentous fungus Byssochlamys sp. SW2 that represent the major taxa in B20 storage tanks were isolated and characterized for their ability to degrade components of B20 biodiesel. Both Wickerhamomyces anomalus SE3 and Byssochlamys sp. SW2 were able to use B20 biodiesel as sole carbon and energy source. We show that the presence of Byssochlamys sp. SW2 can alter the composition in B20 biodiesel in storage tanks, and we offer a model for predicting the severity of biodegradation. Byssochlamys sp. SW2 preferentially degraded palmitic and linoleic acid methyl esters, and our in situ model supports the hypothesis that palmitic and linoleic acid methyl esters are the most susceptible components to biodegradation. We suggest the use of alternative feedstocks containing less palmitic and linoleic acid for B20 biodiesel production to increase fuel stability in storage tanks.