Biodegradability of soy biodiesel in microcosm experiments using soil from the Atlantic Rain Forest

Biodiesel is a promising alternative energy source to diesel fuel and determining its biodegradability is an important aspect of addressing potential environmental spills. The aim of this study was to compare the biodegradability of biodiesel and its effect on soil microbial diversity with that of normal diesel using blends of biodiesel with diesel in microcosm experiments with soil from the Atlantic Rain Forest. Degradation was monitored by respirometry and GC analysis of the substrates. The highest respiration rates were observed in soil contaminated with the B50 (41.47 mg CO2/kg) and B100 (42.35 mg CO2/kg) blends. Soil contaminated with blends B5, B20, B50 and B100 showed higher numbers of culturable heterotrophic microbes than control soil. Chromatographic analyses showed that microcosms contaminated with diesel fuel and the B5 blend had less biodegradation than soil contaminated with the B20, B50 and B100 blends (80%, 62% and 84% of biodegradation, respectively). DGGE analysis showed that samples contaminated with the B5, B20, B50 blends and D100 showed changes in microbial community after the incubation period. Interestingly, soil contaminated with B100 decreased the microbial community compared with the other contaminated samples. While the degradation of pure biodiesel (B100) was efficient, microbial diversity of soil was reduced, which could compromise the overall activity of microorganisms involved in the bioremediation of contaminated soils.

► Pure biodiesel and blends biodiesel/diesel increased microbial activity.
► Increasing the concentration of biodiesel in blends biodiesel/diesel favors biodegradation.
► Biodiesel affects the soil bacterial community.
► Pure biodiesel despite being highly biodegradable reduces microbial diversity.