Kinetic study of high-solids anaerobic co-digestion of pre-treated organic waste in terms of methane production

Wet anaerobic digestion is the most used stabilisation method in the world. However, it has some limitations resulting from the high hydration of the feed, which requires the construction of large-volume anaerobic digestion chambers, difficulty in managing of digested sludge (digestate), which requires dewatering and drying. For this reason, more worldwide attention is paid to the development of dry technologies, which is supported primarily by the possibility of working with higher organic loading, smaller reactor volume, and the minimum need for digestate dewatering. This study aimed to conduct mesophilic and thermophilic batch high-solids anaerobic digestion (HSAD) of sewage sludge (SS) with grease trap sludge (GTS) and algae biomass (AB). Additionally, to shorten the long digestion time, which is the bottleneck of the process, in this study, various pre-treatment methods were used. The effectiveness of the conditioning methods was assessed based on the results of the biochemical determination of the methane potential and the analysis of the kinetics of the process with the use of five kinetic models. The thermochemical pre-treatment method observed the most pronounced pre-treatment effect on the studied SS/GTS/AB mixture at mesophilic temperature. Its methane yield was 109.48 +/- 0.00 N center dot mL-CH4/g-VS, which was 110% higher in comparison to the control (52.21 +/- 0.00 N center dot mL-CH4/g-VS). High-solids co-digestion significantly increased lag phase time (more than 30 d). However, thermochemical pre-treatment improved that parameter by 26.3% compared to the control.