Synergistic anaerobic caffeine degradation and bioelectricity production using microbial fuel cell

Caffeine is considered a pollutant that threatens aquatic life and human well-being, and its anaerobic treatment is typically a slow process. Microbial fuel cells (MFCs) present a sustainable alternative by enabling caffeine degradation while simultaneously generating electricity. This study investigates the anaerobic degradation of caffeine using MFCs as a sustainable wastewater treatment approach under various operational conditions. A two-chambered MFC was established employing synthetic wastewater, sodium acetate as the carbon source, and anaerobic sludge as inoculum. Various concentrations of acetate (0.375 and 1 g/L) and caffeine (10 and 20 mg/L) with and without an external nitrogen source, ammonium chloride, were evaluated for power generation and caffeine degradation efficiency. Results demonstrate that caffeine degradation achieves 100% in 5 days when coupled with external nitrogen sources, whereas degradation without external nitrogen achieves the same within 3 days for both caffeine concentrations. Furthermore, increasing the caffeine loading concentration results in a maximum power density of 5.64, 9.37, and 11.83 mW/m², respectively, for 10 and 20 mg/L caffeine concentrations. Additionally, when the acetate concentration was increased to 1 mg/L without external nitrogen, degradation of 10 and 20 mg/L caffeine requires 3 and 5 days respectively, with a maximum power density of 12.8 mW/m². This investigation underscores the potential of anaerobic bacteria to degrade caffeine utilising it as a nitrogen source while also contributing to power generation in MFCs. Moreover, the results highlight the significant influence of operational parameters on caffeine degradation efficiency and power generation.