Waste to resource conversion from lime-dried sewage sludge particles

As a semi-solid residue from wastewater treatment plants (WWTPs), sewage sludge is soaring worldwide along with the rapid development of WWTPs. It contains valuable resources, such as abundant nutrition and high calorific value, which can be recovered for diverse economic, social, and environmental purposes. However, there are also some drawbacks limiting the wide utilisation of sewage sludge, such as high moisture content, pathogens, odour, and hazardous substances. Lime drying technique has been demonstrated to effectively reduce the moisture content, destroy pathogens, eliminate odour, and stabilize hazardous substances. Nevertheless, it is highly challenging to directly utilize the lime-dried sewage sludge due to its strong alkalinity and corrosion. Given sewage sludge has the potential to be used as an energy source through pyrolysis and the presence of lime in sludge matrix can capture carbon dioxide, the pyrolysis of lime-dried sludge can result in significantly higher yield of valuable gas, e.g. syngas. Therefore, it is of great significance to investigate the pyrolysis performance and gasification characteristics of lime-dried sewage sludge particles. This proposal will investigate the thermodynamic behaviour and the gas composition produced from pyrolysis of lime-dried sewage sludge particles. Syngas yield will be further improved by optimizing pyrolysis temperature, lime contents in sewage sludge, and addition of steel slag catalysts. Moreover, elemental composition of the pyrolysis residues will be analyzed in order to seek a harmless disposal way. Success of this proposal to develop an efficient pyrolysis technology of lime-dried sewage sludge for syngas production would in itself bring new regional industries to both Australia and China.