Tri-optimization of cost, power and efficiency of a waste biomass gasification integrated with a molten carbonate fuel cell by a combined approach

The integration of biomass gasification with high-temperature fuel cells represents a promising solution for sustainable energy generation. Utilizing sewage sludge as the biomass feedstock addresses critical environmental challenges, such as waste management and greenhouse gas emissions, while contributing to energy sustainability. However, there is a lack of studies optimizing such systems to simultaneously address cost, power output, and efficiency. In this study, a biomass gasification system coupled with a molten carbonate fuel cell (MCFC) was simulated in Aspen Plus, using air-steam as gasifying agents. The decision variables, equivalence ratio (ER), steam to biomass ratio (SBR), gasification temperature, fuel cell temperature, inlet air flow rate to the MCFC afterburner, and system operating pressure, were optimized to minimize the levelized cost of electricity (LCOE) while maximizing fuel cell output power and energy efficiency. Sensitivity analysis identified the influence of each variable, and response surface methodology established mathematical relationships between variables and objectives. Multi-objective optimization using a genetic algorithm indicated optimal system performance at an ER of 0.102, SBR of 0.24, gasifier temperature of 894 °C, fuel cell temperature of 776 °C, inlet air flow rate of 24.8 kmol/h, and pressure of 1.26 bar, achieving a LCOE of 0.42 $/kWh, fuel cell output power of 0.224 W/cm2, and energy efficiency of 60.1 %.