Towards a circular economy: A comprehensive study of higher heat values and emission potential of various municipal solid wastes

Abstract

Maximizing resource recovery from waste streams (e.g., energy) is a critical challenge for municipalities. Utilizing the ultimate analysis and high heat value (HHV), we investigated the energy recovery and emission characteristics for 252 solid wastes of a diverse range of geographical origins classifications (e.g., 30 paper, 12 textile, 12 rubber and leather, 29 MSW mixture, 34 plastic, 61 wood, 20 sewage sludge and 53 other wastes) under the thermal waste-to-energy operation. Given the significance of wastes' HHV data, we proposed a rapid and cost-effective methodology for filling the gaps in the experimental data by prediction of the missing or uncertain wastes' HHV. We further employed wastes' nitrogen and sulphur contents to assess their atmospheric emissions. The results from this analysis show the highest energy content belonged to plastic waste, but higher levels of air pollution (mainly due to nitrogen and sulfur) could be emitted during thermal energy recovery of sewage sludge, rubber, and textile wastes. Also, we demonstrated more significant potential for recovering energy from plastic, wood, and paper wastes, while emitting less nitrogen and sulphur compounds to the atmosphere. Finally, our presented HHV models outperform concerning generalizability, validity, and accuracy when comparing the obtained results to those of previously published models. The results from this present study are particularly advantageous in designing sustainable thermal waste-to-energy systems to facilitate cities' transition into a circular economy.

Keywords: Circular economy; Energy performance analysis; High heating value (HHV); Municipal solid waste (MSW); Waste-to-energy systems.