Quantification of carbon savings from the reuse of existing piles in soft soils

This paper aims to develop a carbon dioxide emission model using the carbon dioxide emission factors methodology to quantify the carbon dioxide emissions during the construction of bridge substructures in soft soils. The carbon dioxide emissions calculated for two scenarios, one use of existing piles and the other non-use of existing piles, were compared. The construction of the bridge substructure is segmented into four distinct processes, such as production of building materials, logistics and transportation, construction and retrofit reuse. The carbon dioxide emission factors associated with various construction processes and materials are quantified. The quantification model developed in this study, based on soft soil engineering cases, integrates project bill of quantities data to enable cross-geological assessment of carbon reduction benefits from existing pile reuse. The findings from the case study in Shanghai indicate that the carbon dioxide emissions associated with the scheme using existing piles amount to 19,160.46 tonnes of CO2 (tCO2), which is 4,131.71 tCO2 less than the emissions produced by the scheme non-use of existing piles. The material production phase contributes the greatest reduction in carbon dioxide emissions, amounting to 3731.6 tCO2, followed by the construction phase with a reduction of 388.39 tCO2, and the transportation phase with a reduction of 88.78 tCO2. Conversely, the retrofit reuse phase results in an increase of 77.06 tCO2. Consequently, the reuse of existing piles in soft soils can substantially decrease carbon dioxide emissions, thereby mitigating environmental impacts.