Urban industrial solid waste metabolism based on ecological network analysis: A case study of Tianjin

Socioeconomic metabolism (SEM) is seen as a useful analytical tool to characterize the flows of materials and energy that occur between nature and our various societies. This tool has been widely applied in waste management. Based on a case study in Tianjin, which is one of the most structured industrial cities in China, a citylevel waste input-output (WIO) model is established, and a series of ecological network indicators are estimated and analyzed. The results show that (1) The indirect generation of industrial solid waste (ISW) in Tianjin was 1.6 times higher than the direct generation in 2017, with Smelting and pressing of metals sector topping in direct generation and construction in indirect generation. (2) The most important control on the solid waste metabolic system in Tianjin in 2017 was the smelting and pressing of the metals sector, which corroborates the fact that Tianjin is an essential steel production base in northern China. (3) The dominant intersectoral metabolic relationships in Tianjin are exploitative relationships, accounting for 54% and 62%, followed by competitive relationships accounting for 36% and 30% and mutualism relationships accounting for 10% and 13% of common industrial solid waste (CISW) and hazardous waste (HW) generation, respectively. This study investigates the solid waste metabolic characteristics of typical industrial metropolitan areas from the perspective of metabolic network relationships and provides suggestions for identifying management hotspots.