Evaluation of mitigation potential of GHG emissions from the construction of prefabricated subway station

In an attempt to mitigate greenhouse gas (GHG) emissions from the transport sector, urban rail transit (URT) has been given high priority by the Chinese government. However, the GHG emissions associated with the operation and construction of URT systems are of public and scientific concern. Although some efforts have been made to reduce GHG emissbions owing to URT, the mitigation potential of construction-related GHG emissions is yet to be exploited. To achieve this potential, innovations and optimization in construction methods and management are required. In this study, the mitigation potential of GHG emissions from prefabricated structures in subway stations is investigated. The results show that the construction of a unit length prefabricated section generates 12.59% less GHG emissions than those of the cast-in-site section. In particular, embodied emissions from building materials drop by 14.38% in prefabricated structures, which is achieved by structural optimization and a lower attrition rate. Moreover, off-site prefabrication enables the adoption of cleaner fuel. In the case station, GHG emissions from natural gases account for 83.86% of the total fuel-based emissions at a prefabrication site; therefore, the fuel-based emissions of prefabrication have been significantly mitigated. Another mitigation source comes from the contribution of reduced labor; it is estimated that an extra 0.780t CO2.eq. is saved for the construction of a 1-m prefabricated section through the saved living facilities of on-site workers. In addition, the adaptability of prefabricated structures is checked under different service levels, and results indicate that the proposed widening scheme loses its mitigation efficiency when the width increment exceeds 2 m. (C) 2019 Elsevier Ltd. All rights reserved.