Guidelines for the Assessment of Carbon Dioxide Emissions in Infrastructure Construction: A Case Study of the High-Speed Rail Tunnel Construction Project, Khlong Phai Section, Bangkok–Nakhon Ratchasima Route (Phase 1)

Abstract

The construction of high-speed rail systems represents a new and large-scale infrastructure initiative in Thailand, necessitating a comprehensive assessment of environmental impacts. However, there is a lack of specialized research on carbon dioxide (CO ₂) emissions from construction activities, particularly for tunnel construction. This research aims to evaluate CO₂eq emissions throughout the construction phase of the Khlong Phai Tunnel, a major component of the High-Speed Rail Project, Phase 1: Bangkok–Nakhon Ratchasima. The assessment applies the Life Cycle Assessment (LCA) methodology to estimate carbon dioxide equivalent (CO₂eq) emissions, encompassing three key stages: material production, material transport, and construction. The results reveal that tunnel construction generates significantly higher CO₂eq emissions compared to other types of high-speed rail structures, primarily due to the complexity of excavation techniques and the substantial quantity of materials required. To ensure analytical precision, CO₂eq emissions were categorized into three main work types: excavation and blasting, structural works, and track works. The study found that the total CO₂eq emissions from the Khlong Phai Tunnel construction amounted to 125.49 million kilograms, with an average intensity of 30,609.17 kgCO₂eq per meter. Among these, structural works were identified as the largest emission source, accounting for 99.08 million kgCO₂eq or over 78 percent of the total, followed by excavation and blasting (13.45 million kgCO₂eq) and track works (12.95 million kgCO₂eq). These findings underscore the critical importance of prioritizing emission reduction strategies and technological improvements in material production and utilization within the structural phase. The outcomes of this study provide a valuable foundation for setting carbon reduction targets and formulating effective environmental management strategies for future complex infrastructure projects in Thailand.