Biodegradability of biodiesel in the aquatic environment

The biodegradability of various biodiesel fuels was examined by the CO2 evolution method (EPA 560/6-82-003), BOD5 (EPA 405.1), COD (EPA 410), and gas chromatography (GC) analyses in an aquatic system. The fuels examined included the methyl- and ethyl-esters of rapeseed oil and soybean oil, neat rapeseed oil, neat soybean oil and Phillips 2-D law sulfur; reference petroleum diesel. Blends of biodiesel/petroleum diesel at different volumetric ratios including 80/20, 50/50, and 20/80, were also examined. The results demonstrate that all the biodiesel fuels are "readily biodegradable". Moreover; in the presence of REE, the degradation rate of petroleum diesel increased to twice that of petroleum diesel alone. The pattern of biodegradation in the blends and reasons why biodiesel is more readily degradable than petroleum diesel are discussed The biodegradation monitoring results from both CO2 evolution and GC methods are compared.