Optimization of Biogas Production from Biomass Feedstocks Through Anaerobic Digestion: A Statistical Approach

The growing global population underscores the urgent need for effective waste management protocols and sustainable energy systems. This study used Aspen Plus process simulations to evaluate biogas production from three biomass feedstocks—pig manure, cow manure, and sugarcane bagasse—through anaerobic digestion. A full factorial design of computational experiments (48 simulation runs) was used to evaluate the influence of feedstock type, biomass flow rate, and feed inlet temperature, with the digester held at 55 °C, on the methane (CH4) mole fraction, carbon dioxide (CO2) mole fraction, lower heating value (LHV), and Gibbs free energy of the biogas. Variance contribution analysis showed that feedstock identity was the dominant factor governing biogas composition and energy performance, accounting for more than 99.99% of the variation in every response, with pig manure yielding the highest methane concentration (53.8 mol%) and calorific value (21,782.9 kJ/kg). The best-performing biogas stream was then subjected to dry methane reforming (DMR) in a Gibbs reactor, producing at thermodynamic equilibrium a synthesis gas with an H2/CO molar ratio of 1.45, a value below the ratio of approximately 2 generally targeted for cobalt-based Fischer–Tropsch synthesis. A comparative analysis against seven recent experimental and simulation studies supported the physical plausibility of the predicted biogas compositions and, together with the reforming literature, identified critical engineering challenges, including gas cleaning and the risk of carbon deposition under steam-free reforming conditions. These findings provide a simulation-based screening of residual feedstocks for biogas production and upgrading.