Biodiesel Addition Influences Biodegradation Rates of Fresh and Artificially Weathered Diesel Fuel in Alaskan Sand

Abstract

Biodiesel is increasingly used in transportation and heating as an alternative to diesel fuel, furthering sustainability by reducing fossil fuel use and posing lower risks when spilled. The bioremediation of soil contaminated with a 20% fish biodiesel blend or heating diesel (HD) was studied in laboratory microcosms. Fresh fuel and artificially weathered fuel were compared by placing activated carbon (AC) in the microcosms to remove volatile fuel fractions, accelerating hydrocarbon weathering. After a brief lag phase, during which all microcosms behaved similarly, microbial respiration increased exponentially. In general, biodiesel blend was biodegraded faster than HD and high degradation rates were sustained substantially longer for biodiesel blend than for HD. Cumulative mineralization was considerably higher for biodiesel blend than for HD fuel. The weathering induced by activated carbon suppressed mineralization rates for the first three weeks, resulting in lower cumulative mineralization and nitrogen use. As calculated from nitrogen consumption, about 10% of the carbon from hydrocarbons was incorporated into biomass. After four weeks, approximately only half of the fuel hydrocarbons remained in the soil. Overall, accelerated fuel weathering, caused by AC addition, especially when frequently changed, resulted in decreased fuel mineralization, decreased nitrogen use, and lower respiration values during the exponential phase compared with controls without AC.