Integrating Rheology into ADM1: A Viscosity-Driven Model (ADM1_Visc) for Dry Anaerobic Digestion

Dry anaerobic digestion (DAD) is gaining industrial relevance as a sustainable technology for converting solid biomass and organic waste into renewable energy. Unlike wet anaerobic digestion, where the Anaerobic Digestion Model No. 1 (ADM1) successfully represents biochemical processes, there is no validated model capable of accurately predicting DAD performance. High total solids (TS > 15%) induce rheological constraints that limit mass transfer and substrate accessibility, which are not considered in existing ADM1 extensions. This study proposes a new model, ADM1_visc, incorporating a viscosity dependent correction factor (Kηi) into the combined hydrolysis-acidogenesis kinetic term (KmXi) of ADM1_Bollon. The model was calibrated and validated against batch DAD data at 37˚C and 55˚C using crushed potato residues (TS 18% - 35%). ADM1_visc reproduced the dynamics of pH, VFAs, biogas, and CH4 with Nash-Sutcliffe Efficiency > 0.6 for all cases. Comparative analysis showed ADM1_visc outperforms ADM1 and ADM1_Bollon under high-viscosity conditions. Viscosity is therefore a key driver of DAD performance, and ADM1_visc offers a robust predictive tool for optimizing DAD and improving biomethane yield.