| Grass is now drawing attention for its high potential for biogas production. Existing anaerobic digesters in wastewater treatment plants can be used for producing biogas by processing grass without having to invest in the construction of new treatment facilities. In this study, batch and continuous digestion experiments were conducted to assess the feasibility of anaerobic co-digestion of sewage sludge and grass. The focus was on a thermophilic condition, starting-up from exiting mesophilic anaerobic digestion of sewage sludge only. The batch and continuous co-digestion experiments used two different sewage sludges. Results demonstrated a methane generation of approximately 0.2 NL-methane/g VS-grass. Furthermore, the addition of grass did not affect the ammonia concentration and improved the dewaterability of the digested sludge. The start-up performance from mesophilic anaerobically digested sewage sludge to thermophilic co-digestion with grass was confirmed. The application of co-digestion in wastewater treatment plants was evaluated by energy and greenhouse gas balances. |
