Yan Zhang

To meet the global need for carbon neutrality, we must first understand the role of urban carbon metabolism. In this study, we developed a land–energy–carbon framework to model the spatial and temporal variation of carbon flows in Beijing from 1990 to 2018. Based on the changes in carbon sequestration and energy consumption, we used ecological network analysis to identify the critical paths for achieving carbon neutrality during land-use changes, thereby revealing possible decarbonization pathways to achieve carbon neutrality. By using GIS software, changes in the center of gravity for carbon flows were visualized in each period, and future urban construction scenarios were explored based on land-use policy. We found that the direct carbon emission peaked in 2010, mostly due to a growing area of transportation and industrial land. Total integrated flows through the network decreased at an average annual rate of 3.8%, and the change from cultivated land to the socioeconomic sectors and the paths between each socioeconomic component accounted for 29.5 and 31.7% of the integrated flows during the study period. The socioeconomic sectors as key nodes in the network should focus both on their scale expansion and on using cleaner energy to reduce carbon emissions. The center of gravity gradually moved southward, indicating that the new emission centers should seek a greener mixture of land use. Reducing carbon emission will strongly relied on transforming Beijing’s energy consumption structure and increasing green areas to improve carbon sinks. Our results provide insights into carbon flow paths that must be modified by implementing land-use policies to reduce carbon emission and produce a more sustainable urban metabolism.

Continuous urbanization and a coordinated regional development strategy have gradually shaped urban agglomerations as new and massive centers of resource consumption in China. Therefore, understanding the material consumption status and the underlying mechanisms for typical Chinese urban agglomerations will support efforts to promote regional resource‐utilization sustainability. In this study, we analyzed material consumption and its structure in the Beijing–Tianjin–Hebei (Jing–Jin–Ji) urban agglomeration from 2000 to 2015 and traced the sources of material consumption and underlying processes from a metabolic perspective. We also identified the main contributors and key drivers behind the changes of consumption during this period. The urban agglomeration's total consumption increased 2.2 times compared to the 2,000 level during the study period, with metallic minerals accounting for the largest proportion. Highly developed cities, including Beijing, Tianjin, Shijiazhuang, Tangshan, and Handan, consumed the largest amounts of materials and generated the most wastes. These cities also relied heavily on both internal and external resources and exchanged materials frequently among their metabolic compartments. Economic activity was the strongest contributor to the increased material consumption, followed by the population increase, whereas decreasing material‐consumption intensity (increased efficiency) restrained the growth of material consumption somewhat. Our application of the material‐flow accounting framework at the scale of an urban agglomeration provides support for future research on material consumption in other typical urban agglomerations, where it can provide support for policy development to alleviate regional resource shortages.

Summary: Regional economic development in China has resulted in an unbalanced distribution of resources and frequent exchanges of resources and products among regions. Therefore, it is necessary to understand these regional differences to support national planning to improve sustainability. In this research, we used energy data and a multiregional input‐output table for China in 2002 to analyze the domestic trade among the 30 provinces and seven regions of China. We also quantified the embodied energy flows and their patterns by means of ecological network analysis and looked at different types of relationships between the regions, such as mutualistic or competing relationships. The results show that the flows connected with the Northern and Eastern regions ranked first, and those connected with the Southwestern and Northwestern regions were the smallest. Based on the flows among provinces and regions, we determined the relationships among them. Results show that more than 95% of the total relationships among the regions were exploitation, with only one competition relationship. The Eastern region received the largest input and the highest benefits from their energy exchanges with other regions. Our study of the regional flows and relationships among the regions and provinces provides useful information on the flows and consumption of embodied energy in China, thereby providing insights into the sustainability of these flows and how to promote sustainable development through regional cooperation.

Summary: Urban energy metabolism includes processes for exploiting, transforming, and consuming energy, as well as processes for recycling by‐products and wastes. Embodied energy is the energy consumed during all of these activities, both directly and indirectly. Multiregional input‐output (MRIO) analysis can calculate the energy consumption embodied in flows among sectors for multiple cities or regions. Our goal was to address a problem apparent in previous research, which was insufficient attention to indirect energy flows. We combined MRIO analysis with ecological network analysis to calculate the embodied energy consumption and the energy‐related carbon footprints of five sectors in three regions that comprise the Jing‐Jin‐Ji agglomeration, using data from 2002 and 2007. Our analysis traced metabolic processes of sectors from the perspective of final consumption. Based on the embodied energy analysis, we quantified the indirect energy consumption implied in exchanges of sectors and its distribution and identified the relationships formed through the indirect consumption to analyze the roles of providers and receivers in the system. Results showed that the embodied energy consumption for the Jing‐Jin‐Ji region increased from 2002 to 2007 as a result of increased energy consumption in Tianjin and Hebei. Overall, consumption of Beijing decreased likely attributable to the fact that government policies relocated industries during this time in anticipation of the Olympic Games. The relationships among sectors changed: Beijing changed from a net exporter to an importer, whereas Hebei changed from a net importer of energy from Beijing to an exporter to Beijing, and Tianjin served as an importer in both years.