Sustainable approach to energy recovery from sewage sludge

摘要

Sewage sludge-to-energy approach was evaluated from the perspective of energy efficiency. Two conversion technologies including anaerobic digestion (AD) for biogas production and fast pyrolysis either targeting bio-oil or pyrolytic gas production were investigated. Use of the AD process can commonly give a specific energy production around 11.6 MJ/kg VS input. On average, the pyrolysis scenario for oil production recovered 62 % of the energy in sludge, while the pyrolysis scenario for gas production recovered 67 %. The results also suggest that the oil-targeted pyrolysis scenario favors the feedstock with High VS content, while the gas-targeted scenario possesses distinct potential for energy recovery from low VS content of sludge. Two parallel conversion pathways were comparatively studied. Pathway-1 is based on the AD followed by pyrolysis conversion, while pathway-2 based on pyrolysis process alone. Pathway-1 had higher energy conversion efficiency than pathway-2.