Dynamic modelling of continuously stirred tank reactors for performance prediction of anaerobic cattle manure digestion at mesophilic conditions

The role of anaerobic digestion to stabilize animal waste for production of energy and fertilizer has received growing attention during the recent years in Iran. Large-scale anaerobic digestion of cattle manure is extensively carried out in continuously stirred tank reactors. A structured mathematical model was used for the simulation of the dynamic behavior of this type of reactor. The model included multiple-reaction stoichiometry, microbial growth kinetics, conventional material balances for an ideally continuous-flow mixed reactor and liquid gas interactions. The model showed good agreement with the existing experimental studies in anaerobic reactors. By using computer simulations under different conditions, we were able to predict the effect of operational parameters such as hydraulic retention time, organic loading rate and the feed composition on the reactor performance. In addition, the stability of the process and the optimum performance of the reactor could be evaluated by the dynamic model.