Pyrolysis Behavior of Sewage Sludge toward Energy and Resource Recovery

Abstract

The sewage sludge energy conversion rate was only about 27% in FY2020, so there is a desire to recover more energy resources from sewage sludge to contribute to a decarbonized society. In this research, the focus was on the gasification of sewage sludge, which is an effective method for recovering energy and resources. The objective of this study was to quantify the effects of three parameters on pyrolysis products: temperature, steam, and olivine (as a bed catalyst). The following findings were obtained: The generation of char and tar decreased, while gas production increased with increasing temperature. Char gasification and tar reforming were observed at 800°C with steam. When sewage sludge was thermally decomposed with olivine under the same conditions, tar, which was not observed under other conditions, was detected, and the maximum higher heating value of the products was obtained. Qualitative analysis of GC-MS suggested a relationship between temperature and the mechanisms of tar and gas formation.