The dynamic stock-flow and driving force analysis of the building metal and non-metal resources at a city scale: An empirical study in Macao

The construction industry is often seen as one of the most dynamic sectors, referring to large resource consumption and waste generation, and has grown rapidly in the last few decades. Under the background of "Zero Waste City, " it will be essential to understand the metabolic stock-flow process and the driving forces of urban building resources. By combining the top-down and bottom-up methods, this study establishes a dynamic material flow analysis (MFA) model to clarify the stock and flow characteristics, driving forces, and future trends of urban building resources in Macao China. The result shows that the total material stock increased from 14.13 million metric tons (Mt) in 1999 to 32.75 Mt in 2018, with an average annual growth rate of 4.29%. In 2018, metal resources accounted for 10.73% of the total building stock (steel and aluminum resources accounted for 10.30% and 0.43%, respectively), and non-metal resources accounted for 89.27%. The construction demolition waste (CD&W) increased from 0.02 Mt in 1999 to 0.69 Mt in 2018. Among metal materials, steel and aluminum accounted for 7.11% and 0.4%, respectively. The demolition quantity of metal resources increased from 1.6 kilotons (kt) in 1999 to 51.8 kt in 2018 (an average annual increase of 1.59%) and peaked at 95.2 kt in 2007. The IPAT (I-environment impact; P-population factor; A-social affluence factor; T-technology factor) method results show that the economy and population are always the driving force for urban building resources stock in Macao China. The scenario analysis shows that, by 2035, the maximum stock of urban building materials in Macao will reach 65.19 Mt, about twice in 2018. The results are expected to provide a theoretical basis for establishing scientific resource management and recycling systems for urban buildings.