Designing cross-city symbiosis strategy in urban agglomeration by trading off decarbonization, health and economic benefits

Leveraging the hyperconnectivity, geographical proximity, and comparative advantages of industrial structures among cities within urban agglomerations to promote cross-city symbiosis offers an effective and affordable approach in facilitating sustainable transition in cities to achieve the Sustainable Development Goals (SDGs). However, the effects of cross-city symbiosis featuring substantial plant diversity remain unknown. Focusing on the typical Beijing-Tianjin-Hebei urban agglomeration in China, our analysis reveals significant spatial mismatch between solid waste generation and co-consumption capacity across cities. The trade-offs among multiple SDGs across 160,875 symbiotic pathways under 322,772 constraints are fully considered to address pollution transfer issues stemming from cross-city symbiosis. Results show that in the optimized strategy, transboundary cooperation can further unlock 26.5% of waste co-consumption ability, contribute an additional 30.6% reduction in CO2 emissions, avoid 24.7% disease cases from air pollution, and increase 35.5% of economic profits. The benefits vary significantly among cities, with industrial cities benefiting more than service-oriented ones. Even in the optimized strategy, pollution transfer among cities cannot be entirely avoided, highlighting the need for a top-down cross-city compensation mechanism. Subsequently, we propose a locally adapted (city-by-city and plant-by-plant) cross-city symbiosis plan. It provides scientific foundations for promoting refined and actionable symbiosis strategies for urban agglomerations worldwide.