A mass diffusion model on the effect of moisture content for solid-state anaerobic digestion

The methane production rate increases with a decrease in moisture content up to the optimum threshold level and diminish in a batch reactor fed with the lignocellulosic material in solid state anaerobic digestion. The interpretation on two-faceted effect of moisture content could not be elucidated by the conventional anaerobic digestion model no 1. This study proposed that the decreased moisture content causes augmented mass diffusion resistance by the accumulation of hydrolytic product. This could lead to the reduced production of methane gas. Based on the hypothesis, a new solid state anaerobic digestion model was developed based on mass diffusion limitation and hydrolysis inhibition. The better degree of agreement between model simulation and the literature as well as experimental data verified that the deterioration in the volumetric rate of methane production. This could be attributed to hydrolysis inhibition as a result of limited mass diffusion in solid state anaerobic digestion.