Potential assessment of biomethane fuel production from municipal sewage plant sludge: Kinetic modeling studies and Techno-economic analysis

• Providing empirical data on methane production from sewage sludge in Cameroon • Identifying optimal conditions for methane production using 8 models • The economic evaluation show that a modest-sized can achieve good profitability • The recovery of biogas containing 74% of CH 4 allows to avoid its direct release This study assesses the potential for biomethane fuel production from sewage sludge from the Cité Verte wastewater treatment plant (WWTP) in Cameroon, as well as its capacity to generate thermal and electrical energy, agronomic benefits and economic viability. Anaerobic digestion (AD) of 200 g volatile matter produced a methane yield of 399-410.9 mL CH₄/g VS over 21 days, with a biomethane fuel content of 74.14%. The modified Gompertz model proved the most effective in predicting biomethane fuel production kinetics. The economic evaluation revealed an initial investment cost of $44,848.55, with a positive net present value (NPV) of 6851. The simple payback period and internal rate of return (IRR) were 7.39 years and 12% respectively. A sensitivity analysis confirmed the project's financial robustness, with NPV remaining positive even for initial cost variations of up to 25%. The results demonstrate that biomethane fuel recovery, along with electricity, heat, and fertilizer production, presents a cost-effective waste management solution for future WWTPs. The high biomethane fuel yield, combined with favorable economic indicators, underscores AD's potential to contribute to renewable energy production, the circular economy and greenhouse gas reduction in developing regions. Nevertheless, particular attention should be paid to characterizing the microbiome to identify the inoculum responsible for reducing latency times.