Volume 12: Low Carbon Cities and Urban Energy Systems: Part I

Enhancement of energy recovery from synergetic treatment of sewage sludge and food waste Chunxing Li, Jie Li, Shengyu Xie, Xinyu Zhu, Xiaonan Wang, Yin Wang, Irini Angelidaki

Abstract

Waste-to-energy is one of the feasible approaches to reduce the dependence of fossil fuel. Sewage sludge and food waste, as main municipal wastes from water and food consumption, have potential to be converted into energy (methane and biochar) to alternative non-renewable energy. In the present study, sewage sludge was hydrothermally treated to improve its dewaterability. The separated filtrate and food waste were applied for mesophilic anaerobic digestion for biogas generation with methane yields of 253 and 510 mL/gVS, respectively, at organic loading of 20 gVS/L. The food waste digestate was used for co-pyrolysis with separated filter sludge cake for improving flammable gas, oil, and biochar generation. Additionally, Cu and Zu in biochar were significantly immobilized after co-pyrolysis, and higher pyrolysis temperature and more digestate addition led to better immobilization performance. In brief, the present work paves the path for friendly treatment of sewage sludge and food waste with energy recovery and improved biochar production, and provides valuable guidance for the operation of our pilot-scale and full-scale reactors to realize the energy self-sufficiency and net energy generation.

Keywords Sewage sludge, Food waste, Energy recovery, Pyrolysis, Anaerobic digestion, Heavy metals