Peanut shell biochar/polypyrrole composite anode for enhanced treatment of vegetable oil wastewater in microbial fuel cells

Adopting a “waste treatment with waste” strategy, peanut shell-an agricultural waste from the upstream oil industry-were used to fabricate a composite anode for treating vegetable oil wastewater from the downstream industry. The anode was fabricated by coating ZnCl₂-activated peanut shell biochar onto carbon cloth and subsequently electrochemically polymerizing polypyrrole (PPyPSBC_ZnCl2/CC). The obtained PPyPSBC_ZnCl2/CC anode exhibited an enormous specific surface area and a significant fraction of pyrrolic nitrogen, resulting in a maximum power density of 533.97 ± 10.56 mW/m² with synthetic wastewater. When a 15% (v/v) vegetable oil wastewater was applied, the microbial fuel cell incorporating the PPyPSBC_ZnCl2/CC electrode attained a highest power density of 441 ± 9.45 mW/m², a COD removal efficiency of 81.44 ± 1.82%, and an oil removal efficiency of 89.03 ± 1.68%. Analysis of the anode effluent revealed a low total volatile fatty acid (VFA) concentration (68.31 ± 10.46 mg/L), dominated by propionic, acetic, and isobutyric acids, indicating efficient degradation of macromolecular organics to VFAs and their subsequent utilization. Microbial community analysis showed enrichment of electroactive and oil-degrading genera, notably Blvii28_wastewater-sludge_group, Acinetobacter and Syntrophomonas , which promoted extracellular electron transfer and pollutant degradation. The PPyPSBC_ZnCl2/CC anode offers a sustainable and cost-effective approach for valorizing agricultural waste into high-performance MFC anodes, enabling efficient treatment of vegetable oil wastewater with concomitant bioenergy recovery.