Low-carbon efforts for underground space development in Singapore

• Singapore’s low-carbon efforts on underground space development are reviewed. • Three key efforts are focused and linked to lifecycle stages of underground structures. • A systematic framework is proposed to quantify carbon emissions during lifecycle stages. Singapore, a land- and resource-scarce nation, serves as a global example of how low-carbon initiatives can drive the sustainable development of underground space in densely populated urban environments. This critical review highlights major low-carbon efforts from both academia and the industry over the past decade, along with supportive policies that integrate these efforts into governance and decision-making processes. These efforts, including cutting carbon emissions through material efficiency, shaping carbon emissions through digitalized construction, and tracking carbon emissions through sustainable operation, not only reflect the national efforts to carbon reductions across the full lifecycle of underground infrastructure but also offer valuable insights for similar urban settings worldwide. Furthermore, the review identifies the development of a well-defined framework for lifecycle carbon assessment as an overarching trend to promote carbon reductions in underground space development. However, significant challenges remain, such as the need for comprehensive data collection and integration, as well as a deeper understanding of how human behavior interacts with operational efficiency. Addressing these challenges requires interdisciplinary collaborations among government agencies, academic researchers, and industry practitioners to develop robust frameworks and dynamic models that more reliably capture the impact of low-carbon strategies on urban underground environments.