Abstract:

In response to the new requirements for systematic sponge city development under China’s “carbon peaking and carbon neutrality” strategy, scientifically evaluating the carbon emissions and carbon emission reduction benefits of sponge city construction holds significant theoretical and practical value. This study took Wuhu, a national sponge demonstration city, as an example. Taking on the perspective of the whole life cycle, and combining the emission factor method and the Technical Guidelines for Carbon Emission Accounting for Sponge City Construction in Anhui Province, this study utilized the carbon emission accounting method for sponge cities that is applicable to engineering in practice, and evaluated the carbon emission and emissions reduction results of four types of typical sponge projects in 2022. Based on this, the study took a residential community as a representative example and employed the NSGA-Ⅱ algorithm to explore strategies for achieving synergistic carbon emissions reduction by optimizing the configuration of multiple types of sponge facilities. The results indicate the following. (1) The carbon emissions from sponge city projects in Wuhu are primarily concentrated in the construction phase, with total emissions of 11438.6 t. Among these, material production and transportation account for 53% and 36%, respectively, indicating considerable potential for emissions reduction. (2) During the operational phase, sponge cities largely rely on sustained natural processes to function, with the carbon reduction effects being relatively concentrated in this stage. The total carbon emissions during this phase are approximately –242.3 t. Assuming that existing operational conditions are maintained without any new facilities, sponge facilities are expected to achieve a cumulative carbon reduction of 7269.7 t in 30 years. Although the annual carbon reduction is relatively limited, long-term operation can gradually offset carbon emissions from the construction phase, demonstrating strong carbon neutrality potential. (3) In terms of specific facility types, green stormwater infrastructure such as grassed swales (4.95 kg/m²) and sunken green spaces (11.35 kg/m²) exhibit relatively low carbon emissions intensities during the construction phase. The carbon reduction benefits of sponge facilities in the operation stage are significantly influenced by their functional characteristics and the scale of implementation. (4) Taking a residential community as an example, and based on the annual total runoff control rate requirement, the coordinated carbon reduction capacity of sponge facilities can be enhanced by reasonably adjusting the scales of sunken green spaces, permeable pavements, rain gardens, and grassed swales. This study provides a quantitative evaluation of multi-facility sponge city systems from a holistic perspective, offering methodological support and a theoretical reference for the development of low-carbon urban drainage systems.

Key words: sponge city, carbon emissions reduction, life cycle assessment (LCA), non-dominated sorting genetic algorithms (NSGA-Ⅱ)