A win-win carbon emission mitigation strategy: Exploring interprovincial collaboration in China’s building sector

The building sector significantly contributes to global warming, necessitating carbon emission mitigation strategies that balance low-carbon development with economic growth. In China, the spatial mismatch between provincial mitigation responsibilities and capacities presents an underexplored opportunity for interprovincial collaboration. This study establishes a two-stage framework that integrates an NSGA-III-based multi-objective optimization model to determine province-specific optimal carbon emission reduction targets, along with the OPTIMAL-TRANSFER model using the Sinkhorn-Knopp algorithm to identify collaborative pathways. The results reveal that: (1) The Priority Mitigation Scenario achieves the largest emission reduction at 1003.097 million tons. (2) The Priority Economic Scenario yields the highest economic gains, 2.6 times greater than the status quo. (3) The Balanced Development Scenario identifies a Pareto-improving win-win pathway, simultaneously scaling up emission reductions by 2.5 times and boosting economic gains to 1.7 times. (4) The interprovincial collaboration pathway highlights critical synergistic partnerships, such as Heilongjiang-Hebei, Qinghai-Shandong, and Guangdong-Ningxia. These outcomes demonstrate that interprovincial collaboration can deliver significantly greater environmental and economic benefits than independent efforts. The findings offer a quantitative foundation for policymakers to formulate spatially differentiated win-win mitigation strategies.