Case Study Comparing Embodied Carbon Emissions in Two Road-Over-Rail Bridge Foundation Designs

This paper examines and compares the embodied carbon emissions in the earthworks and foundation design for two road-over-rail integral bridges in Western Australia. The first bridge is supported on gravity footings and constructed using bottom-up methods, the second on load-bearing contiguous piles constructed using top-down methods. A Life-Cycle Assessment (LCA) for embodied carbon emissions was carried out for each bridge using the framework of PAS 2080. Construction-stage design information was used in the assessment, representing a bottom-up LCA approach to retrospectively identify carbon hotspots to inform future designs. The results are presented in total tonne CO_2e per bridge and tonne CO_2e per bridge deck area to allow direct comparison of the embodied carbon emissions of the two foundation systems. The carbon hotspots in each design are identified. The paper closes with the authors’ assessment of opportunities in the design process for geotechnical designers to have influence on embodied carbon over the design life of these bridge types.