Thermophilic Biodegradation of Diesel Oil in Food Waste Composting Processes Without Bioaugmentation

In this study, 26,315 mg/kg of diesel oil was mixed with food waste; the mixture was subjected to composting and monitored for temperature, pH, and moisture content to assure a normal composting process. Variation of total petroleum hydrocarbon (TPH) in the compost was monitored to better understand the progress of diesel decomposition. Samples were also collected for identifying Oleiphilus species. Results showed that food waste composting is effective in decomposing diesel oil, as the TPH was reduced to 2000 mg/kg with about 90%-92% removal efficiencies at the 24th day. Eleven Oleiphilus species were isolated during various composting stages: five from the initial stage, two from the temperature-rising stage, one from the thermophilic stage, one from the temperature-recovering stage, and two from the maturing stage. These observations reveal that the food waste composting pile contained a wide variety of microorganisms, and microorganisms with different oil-decomposing capabilities developed during the various stages of the composting process. After isolation and enrichment, these microbial consortiums may be developed to improve the novel biological method for treating oils in contaminated environment using food waste composting process. It was observed that major decomposition occurred in the thermophilic stage, a divergence from conventional biological treatment approaches conducted in mesophilic environments. Therefore, the proposed composting process involving various diesel-degrading thermophiles facilitated the biodegradation of diesel oil without bioaugmentation, reducing the bioremediation time and cost.