Physico-chemical Characterization of sewage sludge for thermochemical conversion processes.

Thermochemical conversion of sewage sludge has the advantage of being a ‘waste to energy option’ enabling sustainable waste disposal. Among the different methods of waste to energy conversion, the thermochemical route has many advantages over the other methods, such as high reduction in volume of feedstock and lower process time. However, sewage sludge is a non-conventional type of biomass whose characteristics and behavior under various operating conditions are quite different from the conventional type of biomasses because of its distinct composition. The various complex reactions occurring during the thermochemical conversion process depend on the physical and chemical properties of the feedstock. It is essential to have a proper understanding of the physical as well as chemical characteristics of feedstock for better processing and utilization. Accurate and reliable information about the feedstock is required for the design, operation, and optimization of the thermochemical conversion processes. Detailed studies on lignocellulosic biomasses are available in the literature, but only limited works are reported on non-lignocellulosic biomasses such as sewage sludge. This paper provides a comprehensive analysis of physical and chemical characteristics of sewage sludge influencing the thermochemical conversion processes. The results for furnace-dried sludge showed that the volatile matter (49.82% by weight), fixed carbon (7.46% by weight) and higher heating value of sewage sludge (12.26 MJ/kg) samples are comparable to that of conventional biomasses. However, higher moisture and ash contents, presence of heavy metals, sulfur, and acidic oxides revealed its distinct nature and indicated the need for additional primary processing and additives for its suitability in thermochemical conversion. [ABSTRACT FROM AUTHOR]