Biotechnology Journal International

This study evaluated the influence of organic fertilizers produced from spent lubricating oil (SLO) spiked aerobic composting technique on hydrocarbon degradation rate in soils. The compost windrows (Ft₂ and Ft₄), consisting of kitchen and agricultural wastes, were spiked with varying concentrations (2% and 4%) of SLO. The resultant organic fertilizers were employed as amendment in pollution simulated potted soils laid out in a complete randomized block design with three replications for 90 days. Results revealed higher counts of hydrocarbon utilizing microbes (HUB: 4.2±0.02×10⁴cfu/g in Ft₂, 3.0±0.02×10⁴cfu/g in Ft₄; HUF: 3.9±0.2×10⁴cfu/g in Ft₂, 2.5±0.02×10⁴cfu/g in Ft₄) in spiked compost compared to the control, Ft₀ (HUB: 7.9±0.02×10³cfu/g; HUF: 6.0±0.2×10³cfu/g). Mean count in amended soils reflected a dose-dependent increase which followed the trend: Ft₂ ˃ Ft₀ ˃ Ft₄ for the 5% (3.7×10⁸ cfu/g), 10% (9.2×10⁷ cfu/g) and 15% (6.9×10⁷ cfu/g) levels of fertilizer treatments respectively. There was a significant (P<0.05) reduction in the TPH content of soils after 90days treatment with organic fertilizers. Generally, remediation efficiency followed the order: Ft₂ ˃ Ft₀ ˃ Ft₄, with the highest (11.51%) achieved at 5% Ft₂ application. Spiking technique was responsible for the higher counts of hydrocarbon utilizing microbes and enhanced bioremediation associated with the use of fertilizers Ft₂.