Prospective life cycle assessment of road infrastructure in the context of circular economy: advances, challenges, and opportunities
Main Presenter: Zhi Cao
Road infrastructure is an integral building block of our society by provisioning essential services (e.g., movement of resources and commuting) and stimulating the socio-economic development of local communities. The deterioration of road infrastructure is a dynamic process that affects such essential services through degrading the pavement durability and increasing the rolling resistance, which further influences the material and energy consumption for pavement maintenance, rehabilitation, and reconstruction. Existing life cycle assessment (LCA) studies of pavements have established a foundational framework to estimate environmental impacts but fail to include the dynamics of pavement in the system. In response to calls for a transition toward a circular economy, utilization of secondary materials through various recycling technologies (e.g., hot, warm, or cold recycling) has been increasingly considered in LCA of road infrastructure. However, it remains unclear under what conditions
one recycling technology is superior to other options. In order to understand the key methodological advances and challenges and identify opportunities for improving the utility of LCA tools of pavement, we provide a critical review of recent pavement LCA literature by conducting a semi-quantitative analysis on geographic coverage, temporal trend, time horizon, functional unit, life cycle stages, and consideration of reclaimed/secondary materials. In this review, we reflect on a variety of methodological and data issues, including inconsistencies in functional unit, ambiguity of system boundary, incompleteness of certain life cycle stages, and omission of certain important impact categories, but also highlights that due attention to the use phase of pavement can improve the utility of pavement LCA significantly. Our review finds that using more secondary materials (e.g., reclaimed asphalt pavement, recycled tire, waste glass, construction & demolish waste, etc.) in pavements can reduce
environmental impacts notably. For future research, it is recommended that knowledge gaps in the use phase of pavement, such as albedo effect, rolling resistance, and lighting, should be addressed in pavement LCAs, and more sophisticated models (e.g., mechanistic-empirical models) should be used to predict the deterioration of pavement performance to have accurate LCA results and close-to-reality estimation of location-specific effects.