Biodegradation of Spent Automobile Engine Oil in Soil Microcosms Amended with Coconut Shell

Food insecurity and low yield have resulted from the detrimental effects of petroleum hydrocarbon pollution on agricultural soils over time. This study was carried out to determine the bioremediation efficacy of coconut shell on microbiological composition and total petroleum hydrocarbon degradation in spent engine oil polluted soil. Top soil (0-15 cm depth) samples were randomly collected from areas with history of spent engine oil pollution within Anyigba, Kogi State, Nigeria. One kilogram of the polluted-soil was measured into each of nine plastic containers. Coconut shell collected from the Prince Abubakar Audu University, Anyigba, was standardly prepared and mixed with the soil at the rate of 0, 50 and 100 g kg-1 soil in triplicate. The experiment used a completely randomized design. Soil samples were taken from each container at 0 and 28 days for hydrocarbon utilizing bacteria and total petroleum hydrocarbon determination using standard methods. Data obtained from the experiment were subjected to descriptive and inferential statistics. The species identified were Enterobacter sp and Escherichia coli, with Enterobacter sp being the most predominant isolate. The total petroleum hydrocarbon (mgkg-1) of the soil on day 0 was 59.78 ± 1.85. After the amendments (at control, 50 and 100 g kg-1), the total petroleum hydrocarbon (mgkg-1) values were 44.92 ±2.26, 34.82 ± 1.78 and 31.49 ± 0.87 at 28 days respectively. Coconut shell and the high level carbon utilizing bacteria, Enterobacter sp, significantly enhanced the biodegradation process as an impressive 47.32% remediation efficiency was achieved 28 days after amendment in soil treated with 100g of coconut shell. It is recommended that a biostimulation strategy that uses coconut shell and Enterobacter sp be employed in the remediation of spent engine oil and petroleum hydrocarbon polluted soils.