From waste to carbon benefits - A dynamic spatiotemporal model for assessing carbon reduction potential in urban concrete recycling systems

Abstract

Urbanization has intensified the challenge of managing waste concrete, thereby making recycling essential for sustainable resource management. However, the absence of a methodology to assess the carbon reduction potential of municipal waste concrete recycling limits the accurate quantification of emission reduction potential. This study integrates material flow analysis and life cycle assessment to develop a dynamic model that captures regional spatial variations alongside temporal changes in energy consumption and technological advancement. Taking Shanghai as a case study, we project that waste concrete generation will peak at 18 million tons in 2052, with cumulative unrecycled waste reaching 290 million tons by 2060. Over the period 2023–2060, central districts generate 37.82% of waste but rely on peripheral processing, a spatial mismatch requiring cross-regional facility planning and phased capacity expansion strategies. Through scenario analysis, technological optimization (TO) scenario, which achieves a 48% reduction in baseline emissions, yields greater cumulative carbon benefits than the energy transition (ET) scenario; the synergistic optimization (SO) scenario yields the lowest cumulative carbon benefits, 95.4 kt CO₂e. The scenario results indicate that deeper decarbonization may shrink carbon mitigation potential of recycled waste. This model developed in this study provides a practical tool to evaluate waste recycling benefits under different future scenarios and to inform regional decisions such as coordinated facility siting and capacity expansion.