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Abstract Rapid urbanization along the west side of Taiwan straits (WSS) has driven extensive infrastructure expansion and massive consumption of construction materials, raising urgent concerns over their environmental impacts and long-term sustainability. Yet, the carbon reduction potential embedded in infrastructure material metabolism at the urban agglomeration scale remains poorly quantified. This study applies the IMAGINE materials model to quantify the life-cycle stocks, flows, and greenhouse gas (GHG) emissions of seven bulk materials across nine cities in the urban agglomeration on the WSS from 2000 to 2060. Results show that total material stocks increased from 44.2 Mt in 2000–228.7 Mt in 2020, dominated by sand (∼60.2%), gravel (∼31.6%) and cement (∼6.3%). Logistic modeling reveals a clear saturation relationship between per capita infrastructure stocks and built-up area, with most cities expected to reach stock saturation between 2030 and 2045. Material demand is projected to peak at 287.8 Mt in 2036 before declining to 235.4 Mt by 2060. Scenario analysis shows that cumulative GHG emissions under the frozen progress scenario reach 30.4 Mt CO ₂ e by 2060, whereas the circular economy (CE) scenario can reduce emissions by 5.5 Mt CO ₂ e (∼18%). Among the three CE strategies, intensive use (∼12.2%) offered significantly greater cumulative mitigation potential from 2021 to 2060 than improved scrap recovery (∼0.9%) and lifetime extension (∼5.0%). These findings reveal a regional transition from infrastructure expansion to stock optimization and highlight that deep decarbonization depends on demand-side circularity rather than end-of-life recycling. The study provides quantitative evidence and policy insights for formulating differentiated CE strategies to advance China’s carbon neutrality goals in rapidly urbanizing regions.
Zhao et al. (Fri,) studied this question.