Review of the application of gasification and combustion technology and waste-to-energy technologies in sewage sludge treatment

Gasification and combustion processing is deemed reliable and feasible methods in response to concerns about landfilling – a traditional treatment due to rapid growth in disposal capacity and pollution. In gasification and combustion processing, various processes are integrated with different configurations to carry out energy conversion of the thermal treatment process and improve the energy recovery efficiency. This study aimed to propose an effective solution to waste treatment by considering the sustainability and economic perspectives. This paper provided the observation on the technical perspectives of the gasification and combustion processes: the properties of sludge, reactor, combustion or gasification media and operating conditions applied to sewage sludge treatment. In addition, the application of the thermodynamic cycle with various heat recovery strategies for electricity generation was summarized in this paper. According to the research data, sewage sludge combustion efficiency reached up to 99 % at the combustion temperature of 800–850 °C. The maximum hydrogen gas (H2) content was recorded at 40 mol% under steam/oxygen gasifying agent, and the low heating value of syngas was 6–7 MJ/Nm3 for sewage sludge gasification. The integration between air gasification, external fired gas turbines (EFGT) without carbon capture process showed the highest exergy efficiency at 37.1 %, which was higher than 35.7 % resulted from waste combustion technology.