A coupling model for solid-state anaerobic digestion in leach-bed reactors: Mobile-Immobile water and anaerobic digestion model

A coupling distributed solid-state anaerobic digestion model was developed and performed considering a simplified AM2 model and a saturated Mobile-Immobile water Model (MIM). This model allows considering both microporosity and macroporosity evolutions as well as the impact on biological kinetics. This model was adapted, implemented and validated on cattle manure in mesophilic conditions and carried out in a solid-state leach-bed reactor. Three 60 L sacrificial leach-bed reactors were used to determine hydrodynamics and kinetic parameters in a calibration-validation approach. A sensitivity analysis was conducted and has shown a high value of hydrolysis kinetics on outputs variables (until 92% for accumulated methane yield and 72% for volatile fatty acids accumulation) which confirmed the necessity to identify accurately the hydrolysis parameter before calibration step. Finally, the solutes present inside each mobile and immobile region evolved in a different way confirming the model relevance. • A coupled model considering biokinetics and porosity hydrodynamics was developed. • Calibration step is very sensitive to initialization of kinetic parameters. • Hydrolysis kinetics are significant on methane and volatile fatty acid productions. • The model was implemented on cattle manure in mesophilic conditions. • Solute concentrations have a different behavior between mobile and immobile regions.