Dynamic analysis method to open the “black box” of urban metabolism

Urban metabolism is a complex system problem that takes into account urban dynamic behavior such as material, energy, and capital flows. The available methods for urban metabolism are all approaches that consider an urban system to be a “black box”, accounting the input and output flows of energy and material, but lacking an analysis of internal elements and the metabolic processes. This study introduced a system dynamics model to study the stocks, flows, activities, and drivers within an urban system, and developed a double-layer model to implement metabolic modeling at two spatial scales. The system dynamics model is built from the perspective of demand-driven to simulate the input of different resources and materials in the urban metabolism. Emergy analysis was used to calculate the value of variables and evaluate metabolic status. A detailed case study for Jing-Jin-Ji agglomeration of China is used to validate the model and identify major drivers. Results show that the system dynamics approach is suitable for the research of urban metabolism. In future work, more metabolic details should be developed in the model to reduce the impact of data limitations, and more component drivers that affect urban metabolism and relationships within the system should be considered.