New insights into the co-locating concept on synergistic co-digestion of sewage sludge and food waste towards energy self-sufficient in future WWTPs

An innovative co-locating concept base on synergistic co-digestion of sewage sludge (SS) and food waste (FW) was proposed and verified in this study. The results showed that a biggest synergistic effect happened in the co-digestion of SS and FW in volatile solid (VS) mixing ratio of 1:1 with the highest methane yield of 415.3 mL/g VS. It is estimated that about 5.83 × 10⁹ m³ of methane (equivalent to 22.86 billion kWh electric energy) could be generated from China's SS and FW annually by adopting the proposed co-digestion strategy, which was more than enough to meet the annual electric energy demand in China's WWTPs. The analysis of the engineering feasibility and economic viability clearly suggests that the future WWTPs can be transformed to a powerful profit producer instead of consumer by adopting the proposed co-locating concept, which indeed offer a new insight for future of SS and FW management towards a great environmental and economic sustainability.