Abstract

The search for alternative renewable energy sources has mounted interest in biomethane as a viable substitute for fossil fuels. This study explores the anaerobic digestion of petroleum coke, a recalcitrant byproduct of oil refining, enhanced by coal mine-derived microbial inoculum and magnetic iron oxide (Fe?O?) nanoparticles (NPs). The Fe?O? NPs were obtained through the coprecipitation technique. A central composite design within Response Surface Methodology was employed to optimize three variables; pet coke concentration, inoculum size, and NPs dosage. Scanning electron microscopy results of the synthesized NPs showed quasi-spherical morphology, particle aggregation, and distinct crystalline. X-ray diffraction peaks indicative of spinel-type ferrites, confirming a magnetite-based structure. Analysis of variance results of the linear model present a moderate coefficient of determination (R² = 0.5799) for the model, indicating its adequacy for prediction. The optimized conditions for biomethane production were determined as follows: Feedstock (Pet coke) concentration of 8 g/L, inoculum of 8% (v/v), and 40 mg/L of magnetic iron oxide NPs. Under the optimized conditions, the model predicted a biomethane yield of 33.2%, which closely aligned with the experimentally observed yield of 32%; the difference was not statistically significant (P = 0.158) reliability. Validation experiments substantiated the model reliability. The gas chromatography analysis of the generated gas revealed a methane concentration of 55.86 wt%, thereby illustrating significant bioenergy potential. The integration of microbial consortia and NPs strategies offers a promising alternative for converting industrial residues, such as pet coke into sustainable biofuels.

Key words: Peak coke, Biomethane, inoculum size, Magnetic Iron oxide NPs, Anaerobic digestion, Response surface Methodology.