Carbon Neutrality Benefit by Developing Underground Space and Overlying Green Land: Calculation Methodology and Case Study

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The advancement of ecological civilization has heightened the urgency for urban emission reductions. Currently, there is a significant gap in the quantitative assessment of the carbon neutrality benefit of developing underground space and overlaying urban green land. To address this, this study presents a carbon neutrality benefit assessment model based on building lifecycle theory. The model quantifies the carbon emissions of typical public buildings utilizing aboveground/underground space and assesses the carbon sink impacts of green lands. Notably, it introduces the innovative parameter of characteristic time to evaluate how the comprehensive development of underground space and aboveground urban green land contributes to achieving carbon neutrality. Case analysis of a typical shopping mall in northern China revealed that, in comparison to aboveground buildings, underground buildings exhibit higher energy consumption for construction and lighting; however, they demonstrate superior thermal performance, providing warmth in winter and coolness in summer. Furthermore, urban green spaces of equivalent building area can sequester a portion of the carbon emissions produced by underground buildings, resulting in a lower overall carbon emission profile for the underground space system throughout its lifecycle compared to that of the aboveground space system. Consequently, the development of underground spaces plays a crucial role in advancing carbon neutral objectives. The study also emphasizes the importance of selecting plant communities with enhanced carbon sequestration capacities and developing corresponding green spaces to better meet carbon neutrality objectives. This research offers a novel perspective for evaluating the carbon neutrality benefits of underground space systems, providing valuable design guidance for integrating urban underground and aboveground spaces.