Modeling Anaerobic Co-digestion of Food Wastes and Cattle Manure in an Industrial Plant: A System Dynamic Approach

Abstract PurposeAnaerobic co-digestion is a realistic technique for organic waste management as well as biogas production. To monitor the co-digestion processes because of their high susceptibility to instability, a simple, interpretable, and accurate model is required for control design and process optimization.MethodsTherefore, a modified anaerobic digestion model number 2 (AM2) was built in the system dynamics (SD) model) for the prediction of biogas production in an industrial biogas plant fed with cattle manure and food wastes. The predictive ability of the model using the model parameters (kinetic parameters and yield coefficients) estimated in Premium Solver, was checked by comparing model results (biogas flow and compositions) with anaerobic digestion model number 1(ADMI) simulated results and the experimental data obtained from the literature. Sensitivity analysis of the modified AM2 to biogas flow and methane concentration was conducted by varying the inflow of biodegradable fractions, the initial substrate, and biomass concentrations.ResultsThe simulation results of the modified AM2 model were found to correspond with the measured values with percentage errors of 1.42% and 0.6% for methane concentration and biogas flow respectively. The process variables associated with the methanogenesis stage were obtained to be the most sensitive variables.ConclusionThis study showed that the AM2 which is tractable, reduced, and robust, built in the SD model is a vital tool for the operation of the biogas plant's digester.