Evaluation of Composting with ‘Spent’ Mushroom Substrate and Sawdust for Remediation of Petroleum Hydrocarbon-Polluted Soil

Abstract

Aim: To evaluate the capacities of composting ‘spent’ mushroom substrate and sawdust with crude oil polluted soil to enhance degradation of petroleum hydrocarbon. Study Design: The degradation of petroleum hydrocarbon contents of crude oil polluted treatments composted with ‘spent’ mushroom substrate, sawdust and a mixture of ‘spent’ mushroom substrate and sawdust were compared with that of crude oil polluted-not-composted treatment to determine the influence of the compost amendments.  Place and Duration of Study: The Centre for Ecological Studies, Department of Plant Science and Biotechnology, University of Port Harcourt, Nigeria, from March - July 2015. Methodology: Five buckets were each filled with 1500 g of top alluvial soil and labelled T1 – T5. T1 (i.e. control) was not polluted while the other buckets were each polluted with Bonny Light crude oil at 6.7% (v/w). T2 was not composted with any material after pollution. T3 was mixed with 200 g of ‘spent’ mushroom substrate and T4 with 200 g of sawdust while T5 was composted with a mixture of 200 g of ‘spent’ mushroom substrate and 200 g of sawdust. Results: Final pH of 8.4±0.1 and 6.4±0.2 were recorded in T1 and T5 respectively. The pH of T2 decreased from 8.8±0.1 to 7.1±0.1 and from 8.7±0.1 to 7.1±0.4 in T3, but increased from 5.3±0.0 to 8.5±0.0 in T4. Percentage total petroleum hydrocarbon contents decreased by 75.5% in T3 and T5 and 64.9% in T4. Average phosphorus contents increased from 0.33±0.0 to 52.60±0.23 mg/kg in T5, 0.33±0.03 to 1.81±0.35 mg/kg in T4 and from 0.36±0.01 to 1.34±0.62 mg/kg in T3 but decreased from 0.35±0.01 to 0.14±0.60 mg/kg in T2. Total nitrogen contents recorded reduction in T2, T3, T4 and T5 and total organic carbon increased in T2, decreased in T4 and was constant in T5 during the experiment. Conclusion: ‘Spent’ mushroom substrate, sawdust and a mixture of ‘spent’ mushroom substrate and sawdust composted with crude oil polluted soil significantly enhanced removal of soil hydrocarbon content.