Gasification of sewage sludge within a circular economy perspective: a Polish case study

Sewage sludge (SS) is a by-product of wastewater treatment plant (WWTP) operation. Due to fast rates of urbanization and industrialization, and rapid population growth, the world community faces a serious challenge associated with its disposal. There is an urgent need to explore low cost, energy efficient, and sustainable solutions for the treatment, management, and future utilization of SS. Thermal conversion of SS is considered the most promising alternative for sustainable SS management. Among three main thermochemical processes, it seems that gasification (GAS) of SS has the most advantages. The aim of this paper is a presentation of the gasification process as a sustainable method of SS management that takes into account the idea of a circular economy (CE). Gaseous fuel production, phosphorus recovery potential, and solid adsorbent production during the gasification process are analyzed and discussed. Result of this study shows that the lower heating value (LHV) of the gas from SS GAS process is up to 5 MJ/m³_n and it can be effectively utilize in an internal combustion engines. The analysis proved that solid fraction after the SS GAS process can be treated as a valuable phosphorus source and perspective adsorbent materials. The amount of P₂O₅ in this material was equal to 22.06%. It is similar to natural phosphate rocks (28.05%). The maximum of the adsorption capacity of the phenol was comparable with commercial activated carbon (CAC): 42.22 mg/g for solid fraction after SS GAS and 49.72 mg/g for CAC. Graphical abstract.