THERMAL HYDROLYSIS PROCESS FOR ENHANCED BIOMETHANATION OF OFMSW AND SEWAGE SLUDGE

Abstract

This study explored the optimization of biogas production through thermal hydrolysis pretreatment of co-digested Organic Fraction of Municipal Solid Waste (OFMSW) and dewatered Sewage Sludge (SS). The study identified an optimized mixing ratio of 80:20 (on a Volatile Solids basis) and a carbon-to-nitrogen (C/N) ratio of 24 as effective for enhancing pretreatment efficiency. Among the various conditions examined, the optimal pretreatment was found to be at 140°C for 60 minutes. This specific condition resulted in a cumulative biogas volume of 4524.15 ml, a biogas yield of 603 ml/g VS added, a cumulative methane volume of 3795.30 ml, and a cumulative methane yield of 506 ml/g VS added. Additionally, it achieved a maximum Volatile Solids reduction of 58.76% and a maximum soluble chemical oxygen demand (sCOD) removal of 71.30%. However, at temperatures above 140°C, there was a notable decrease in methane yield, biogas volume, biogas yield, and methane volume. This decline was attributed to the formation of inhibitory byproducts, such as Maillard reaction products and furfural acids, during the pretreatment process. Therefore, maintaining the identified optimal conditions is crucial for maximizing biogas yield and overall process efficiency in the thermal hydrolysis pretreatment of co-digested OFMSW and SS.