Optimization of Thermal Pre-treatment Temperature and Time and Material Concentration to Maximize Methane Production in Anaerobic Digestion of Organic Waste

 Anaerobic digestion of municipal organic waste faces numerous challenges. This process is often lengthy, requires a large reactor volume and produces insufficient methane to supply the process energy need, as well as uncertain digestate to be utilized in farmlands. Thermal pretreatment sometimes can be considered as an efficient method to address these problems. Many researchers, on the other hand, suggest that applying high temperature thermal pretreatment for easily biodegradable organics such as food waste will result in reduced methane production. In the current study, the contribution of the independent variables, including pretreatment temperature at 70, 90 and 110 ̊C, pretreatment duration of 30, 75 and 120 minutes as well as the digestible concentration at 8, 12 and 16% to methane production were considered. To optimize the aforementioned variables, modeling was conducted using Box-Behnken design followed by Genetic Algorithm to find the optimal quantities for mentioned parameters. The results of Genetic Algorithm revealed that the optimum pretreatment temperature and time and organic concentration to achieve the highest amount of methane from anaerobic digestion of organic waste would be 96 ̊C, 95 minutes and 12%. The predicted amount of methane applying the optimal conditions of temperature and pretreatment time and solid content resulting from Genetic Algorithm was 354 mL per gram of volatile solids. This value was in a good agreement with the actual amount of methane obtained applying these pretreatment conditions to organic wastes (354  ±4.58).