Concerns around climate change and the environment have motivated the adoption of low impact development (LID) techniques for urban infrastructure. Permeable pavements are one type of LID technique that do not necessitate land use changes, making them particularly suitable for urban environments. This study aims to estimate the global warming potential (GWP) impact of replacing existing concrete sidewalks with permeable pavement systems through a case study in Vancouver, British Columbia. A consequential process-based life cycle assessment (LCA) is proposed to estimate embodied impacts while accounting for reduced downstream effects on the sewer system (i.e., the emission savings brought about by reduced energy consumption in the sewer system due to reduced runoff volumes). Embodied emissions include those created by material manufacturing and their transport, as well as sidewalk construction and maintenance. Emissions savings from the sewer system are estimated by forecasting precipitation and calculating the reduction in runoff volumes in different sewer system configurations (i.e., combined or separate system, with or without pumping). The results suggest that the use of permeable sidewalks will result in a higher GWP impact than conventional concrete sidewalks, on average, across most contexts for Vancouver, British Columbia. The higher GWP attributed to permeable sidewalks stems from literature-based assumptions regarding their durability; specifically, the model assumes a slightly more frequent reconstruction cycle than conventional concrete. Furthermore, the potential operational savings from reduced runoff are marginalized in the Vancouver context due to British Columbia’s low- carbon energy grid, which limits the emissions offset by reduced sewer processing. The results suggest that, for locations with more carbon intensive energy grids, permeable pavements are potentially attractive from a GWP perspective due to their ability to offset energy requirements associated with the sewer system. As a general guiding rule, the results suggest that the use of permeable sidewalks should be attached to other benefits such as flood control or urban heat reduction rather than solely the reduction in carbon releases to the environment.
Storay Otmankheil (Thu,) studied this question.