A process-based carbon accounting framework for public building-attached green space construction: a China case study

Despite their ecological value and operational carbon sinks, the large-scale construction of public building-attached green spaces remains an overlooked source of urban carbon emissions. This study develops a process-based carbon accounting framework integrating quota-based emission factors, applied to three attached green space types (rooftop gardens, green squares, and sunken yards) in a representative public building in Wuhan, China. Construction activities were decomposed into 6 sub-projects and 22 unit processes. Results reveal total emissions of 2,080,646.86 kg CO 2 (95% CI: 1,946,777–2,244,308 kg CO 2 ), with an emission intensity of 95.12 kg CO 2 /m². Road engineering (808,761.21 kg CO 2 , 38.9%) and the base subproject (672,634.38 kg CO 2 , 32.3%) are the primary sources, while granite driveway construction and planting activities are the most emission-intensive unit processes. Emission intensity varied substantially, from 650.3 kg CO 2 /unit for permeable asphalt driveways to 0.32 kg CO 2 /unit for stone ball barriers. Scenario analysis shows that a 10% reduction in material consumption achieves the greatest reduction (137302 kg CO 2 ), with road engineering and the base subproject contributing 75,990.68 kg CO 2 and 61,311.49 kg CO 2 , respectively. LCA verification confirms the framework’s reliability (relative difference: 3.54%). The framework supports activity-level emission management and mitigation strategy selection for low-carbon urban green infrastructure planning.