Bioelectrogenic valorization of sugarcane bagasse: role of sewage addition and substrate pretreatment on power generation and substrate utilization

Sugarcane bagasse (SCB), a recalcitrant lignocellulosic biomass, necessitates pretreatment to enhance the release of soluble organics for effective utilization. This study evaluated three pretreatment methods including alkaline (ALK), acid (AC) and hydrothermal (HTL), to extract sugars from SCB, subsequently evaluating these hydrolysates as substrates for bioelectricity generation in dual-chamber microbial fuel cells (MFCs). The study was conducted in two phases. Phase I utilized tap water to dilute the SCB hydrolysate, while Phase II replaced tap water with sewage. Results from Phase I indicated that ALK hydrolysate yielded the highest current density (414.00 mA/m²), followed by AC (339.00 mA/m²) and HTL (316.13 mA/m²). The corresponding chemical oxygen demand (COD) degradation rates were 57.60% for ALK, 46.67% for AC, and 37.30% for HTL hydrolysates. Phase II introduced sewage as a diluent, enhanced HTL hydrolysate performance (415.05 mA/m²; 53.50% COD removal) due to improved ionic conductivity and nutrient availability, which fostered better biofilm formation and electron transfer. The blending of AC and ALK hydrolysates facilitated in-situ pH neutralization, optimizing substrate complexity and buffering stability, culminating in a peak specific power yield of 1011 W/kgCOD. Cyclic voltammetry (CV) confirmed the development of an electroactive biofilm, indicating effective electron mediation. The study demonstrated that integrating optimized pretreatment with cost-effective methodologies, such as sewage repurposing can amplify energy recovery from SCB. This approach not only improves green energy production but also aligns with circular bioeconomy principles by valorizing agricultural residues and wastewater, presenting a scalable model for sustainable bioenergy systems.