Integrated numerical modeling of co-anaerobic digestion using hybrid ADM1–ADM2 framework to evaluate the thermo-biochemical performance of lipid-rich food waste for enhanced biogas production

Abstract To compare lipid-rich food waste conversion through thermophilic anaerobic digestion, a nonlinear model was developed by combining ADM1 and some of the regulatory features of ADM2. The model integrates the suppression of LCFA and a fixed and pH-dependent suppression and calculates the finer details of this action using sigmoid and Hill equations. The coupled equations representing substrate degradation, microbes growth, and LCFA accumulation and methane generation were assessed with the help of a MATLAB program with the help of an ode15s routine. A study was performed on nine simulated conditions with a concentration of LCFA between 0.2 and 0.6 g/L and pH of 6.0–7.0. It was found out that the success of the process was most affected by pH. At pH of 6.0, production was 0.02 gCOD and production of methane at pH of 7.0 was 1.93 gCOD under high concentrations of LCFA. Besides, AUC analysis also showed that, during wastewater treatment process, when pH changed between 6.0 and 7.0, the AUC changed to 55.5 gCOD (day) to 0.7 gCOD (day). The model is able to present key behaviors associated with the co-digestion of lipid-rich substrates like washout of microbes and the degradation of inhibitions. The study establishes that maintenance of pH balance and the maintenance of the quantity of fatty acids or LCFAs produced in linear form improve biogas in high-fat wastes treatment systems.