Comprehensive evaluation of the structural characteristics of an urban metabolic system: Model development and a case study of Beijing

The resource shortages and environmental problems that cities face can be attributed to their increasing metabolic throughflow and their metabolic inefficiency. To support urban ecological management, it is necessary to identify the main metabolic actors responsible for these problems and analyze the characteristics of their metabolic structure. In this paper, we divide a typical urban metabolic system into seven components. Using material-flow analysis, we accounted for the amounts of resources and wastes transferred among the system's components and between the system and its environment, using Beijing from 1998 to 2007 as a case study. We used four indicators (metabolic scale, intensity, efficiency, and impact) to represent the inner structural characteristics of the urban metabolic system and analyzed the system based on the proposed indicators. The results provide scientific support for identifying the key metabolic actors responsible for urban metabolic disorders by accurately characterizing the city's metabolic status.

► Urban metabolic processes can be analyzed by treating cities as complex ecosystems.
► An urban network model can be divided into resource and waste metabolisms.
► Four indicators are proposed to evaluate the network structure and metabolic level.