Choice of sewage sludge thermochemical disposal methods from multi‐ perspective analysis

Thermochemical conversion disposal methods for sewage sludge usually include incineration, gasification and pyrolysis. Incineration technology is relatively mature and the incineration ash can be potentially used for phosphorus (P) recovery. Gasification can be used to recover syngas which is convenient to be used for power & heat generation. While through pyrolysis, syngas of high quality, tar and char can be recovered. To make a proper choice from them, these techniques are compared from perspective of technology maturity, investment, operation cost, environmental impact and acceptability of the public. Technology maturity is evaluated by comparing industrial applications. Investment and operation cost are evaluated based on practical operation experiences; environmental impacts are evaluated based on life cycle assessment; and acceptability of the public is based on a questionnaire survey. Based on a scenario with capacity of 100 t/d in eastern China, investment are comparable for the three technologies within the range of 250,000-400,000 RMB yuan/(ton.d) with gasification close to the higher side; the operation cost varies in the range of 140 - 400 RMB yuan/ton with incineration the highest; pyrolysis corresponds to the lowest environmental impacts and the highest acceptability of the public, however the pyrolysis technology is not fully developed, especially the durable pyrolysis reactor and the application of pyrolysis char