ABSTRACT
Gasification of sewage sludge (SS) is a promising technology to produce energy sustainably and offers environmental and economic benefits over other thermal treatments. The syngas produced can be used in gas turbines to produce electricity. SS is a potential energy source, mostly disposed of without any treatment. This book chapter covers SS properties and composition, gasification mechanism, chemistry, operating conditions, technologies, and practical implications, specifically in the light of life cycle assessment (LCA) and circular economy. The case studies of fluidized bed gasification and fixed bed gasification plants in Italy and Poland have been discussed. Different techniques, such as palletization, combinations of different materials blends, steam gasification, and supercritical waster gasification, have been discussed to improve the yield of the syngas, efficiency, energy, and quality. For commercial applications of gasification process, co-conversion of waste blends is already designed, which seems practical approach in implementation of the process. Some challenges in the SS gasification process include high capital investment, huge power consumption for mechanical dewatering of SS, and blockage of pipelines, nozzles, and valves with tar. These issues can be solved by solar drying and catalytic gasification. Furthermore, catalyst modification could be performed to acclimatize the extreme working conditions, pressure, temperature, agglomeration, and mechanical destruction. Nutrient recovery from the remaining ash of SS gasification, LCA, and implications is also primely important in the circular economy approach. The environmental and economic performance of SS gasification can be determined by performing more LCA-based studies.
