Introduction of biofuels to the fuel matrix poses new questions and challenges. The present study investigates
the microbiological stability of biodiesel blends in small scale microcosms. The study presents
results from incubations of diesel–biodiesel blends with contaminated inoculation water collected from
diesel storage tanks to ensure the presence of relevant fuel degrading bacteria. DAPI and qPCR analyses
has subsequently shown an increased bacterial growth and activity in the microcosms containing biodiesel
blends as the carbon source compared to those microcosms where neat fossil diesel made up the
carbon source. Several anaerobic microorganisms have been identified after incubation. Presence of
methanogens, sulfate-reducing bacteria and nitrate reducing bacteria has furthermore been confirmed
by chemical analyses, supplemented by observations of methane formation in biodiesel incubations.
The findings will contribute to the knowledge base for a safer introduction of biodiesel in the fuel matrix
by employment of proper house-keeping and monitoring methods.