A High-Precision Geo-Spatial-Techno-Economic Framework for CO2 Source-Sink Pairing: Land-Sea Synergy and Cross-Regional Coalitions in China.

China suffers from a severe geospatial mismatch between industrial and energy CO2 emission sources and geological storage sinks, while existing carbon storage assessments lack national-scale high-resolution and land-sea synergy analysis. This study develops a high-resolution (1 km × 1 km) techno-economic framework integrating hierarchical storage capacity, site suitability, and full-chain carbon capture and storage (CCS) source-sink matching to clarify China's geological carbon storage characteristics. The results show nearly balanced onshore-offshore theoretical (2.5 trillion tons) and P50 effective (1.5 trillion tons) storage capacities, with distinct cost gaps: onshore storage costs of 3-10 USD/t and offshore costs of 10-60 USD/t. Benefiting from regional capacity and transportation economic heterogeneity, 60-75% of China's coal-based captured CO2 achieves a levelized cost below 90 USD/t. This fine-scale framework maps national CCS distribution heterogeneities across multiple scales. We further propose cross-regional CCS coalitions via infrastructure sharing, land-sea storage integration, and cross-region carbon corridors to mitigate imbalance and could manage about 80% of coal-sector emissions, providing a scalable solution for Global South countries with unbalanced carbon development.