The significance of measuring embodied carbon dioxide equivalent in water sector infrastructure

Abstract

For the water sector to cope with rising populations and the anticipated impacts of climate change, increasing amounts of construction output are needed to build water-related infrastructure. Amidst emerging operational energy efficiencies and gradual grid decarbonisation, the relative impact and extent of embodied carbon dioxide equivalent (embodied CO2e) effected from the construction and maintenance of water sector infrastructure is likely to rise. For practitioners in the water and construction sectors, there is a growing need to be able to understand and account for embodied CO2e. However, the contribution of embodied CO2e as part of the whole life cycle impacts of water related infrastructure is disputed in the current literature, and with only a handful of studies suggesting it is important its significance is not established. This work aims to explore this issue, and provide clarity. This paper shows the calculations involved to measure the embodied and operational CO2e of Old Ford Water Recycling Plant, a small blackwater recycling treatment facility producing 574 m3/day of reclaimed water. For the analyses, embodied carbon dioxide coefficients (ECCs) are used that were provided by the water operator Thames Water Utilities Ltd (TWU), and based on its supply chain, and datasets from Ecoinvent v3.1, a commercially available assessment tool. The final aggregated carbon footprint values calculated are 1.430 kgCO2e (TWU in-house analysis) and 1.566 kgCO2e (Ecoinvent) per cubic metre of recycled water. The results show that the contribution of embodied CO2e is significant, making up 50.7% (TWU) and 77.3% (Ecoinvent) of the total carbon footprint value in each analysis. The research identified that assessments could be improved if there was higher-quality data provided by manufacturers and suppliers on the embodied CO2e content of materials, components, and equipment. This paper further illustrates differences between calculations using generic data (Ecoinvent) and supply chain data, and the difficulties involved in producing functionally equivalent life cycle inventories.