Material Circularity and Waste-Management GHG Emissions of Construction and Demolition Waste in Bangkok: A Dynamic Material Flow Analysis

Construction and demolition waste (CDW) is a major urban material flow whose long-term generation depends on the age structure of the building stock. This study develops an inflow-driven, cohort-based dynamic material flow analysis (dMFA) for Bangkok that integrates reconstructed pre-2004 building cohorts, CDW generation, a system-level Material Circularity Indicator (MCIsys), and waste-management greenhouse gas (GHG) accounting. Six scenarios, representing a business-as-usual baseline and single and combined applications of waste prevention, recycling, and lifetime extension, were evaluated through 2100. Demolition waste dominated the modeled CDW stream, with concrete as the largest urban-mining stream. Total CDW reached a mid-century maximum of 13.8 Mt/yr around 2062, ranging from 12.1 to 14.6 Mt/yr in 2055–2066 across the reconstruction and inflow sensitivity cases. MCIsys increased from 0.128 under the baseline to 0.290 under Circular Routing and 0.313 under Ambitious Circular Economy by 2100. Within the direct waste-management boundary, which excludes avoided virgin-material production, higher recycling increased cumulative GHG emissions by 3–30% over 2025–2100 across all tested inflow cases because of recycling processing and longer transport, whereas lifetime extension lowered them by 9–22% within the horizon by delaying demolition. The MCIsys contrast remained robust under parameter uncertainty, and the GHG increase under circular routing occurred in all paired simulations.