Analysis of cement flow and stock of urban buildings and its environmental impact assessment in Shenzhen City

China's rapid urbanization with massive construction activities accelerated raw materials extraction and consumption such as cement. This study conducted a bottom-up material flow analysis to estimate the stocks and flows of cement in building sector, using Shenzhen (China) from 1979 to 2018 as an example. The environmental impacts measured by carbon emission equivalent was also estimated for sustainability. Results show that approximately 81.2 million metric tons (Mt) cement were consumed for building construction from 1979 to 2018 in Shenzhen, with an annual consumption of over 2Mt averagely. Moreover, cement outflows (measured by construction and demolition waste) accounted for 25%~29% of total inflows. By 2018, the cement stock in buildings amounted to 62Mt (4.7t/cap), embedding 68.8Mt carbon emissions. An estimation of 9% of this amount emissions were directly absorbed by the existed buildings, with another 11% could potentially be carbonated by recycled concrete aggregate (flow) if subject proper condition. Finally, based on the evaluation of cement flows and stocks in Shenzhen, strengthening effective cement management, promoting cement carbon reduction, and improving carbon sequestration capacity were raised for sustainable urban development. © 2021, Editorial Board of China Environmental Science. All right reserved.