A Combined Urban Metabolism and Life Cycle Assessment Approach to Improve the Sustainability of Urban Hardscapes

Streets, sidewalks, parking areas, plazas, and other paved surfaces cover large portions of urban areas. These urban hardscapes contribute significantly to cities’ resource consumption. Although urban hardscapes enable people and goods to move freely, they also have profound impacts on cities’ water, air quality, energy, and material use. Reducing the environmental impacts of hardscapes will be an important component of making cities more sustainable. The necessary first step is to quantify those impacts.

UC Davis and Tongji University researchers developed a methodology that combines urban metabolism and life cycle assessment to examine the life cycle impacts of hardscapes at the urban scale rather than at the product or project scale. Urban metabolism (UM) is a method that accounts for the flow of resources such as energy, materials, and water into an urban area, their processing and consumption within the urban area, and their subsequent flows out of the area. Life cycle assessment (LCA) is a quantitative environmental assessment method that considers the total supply chain and life cycle impacts of a product or system from “cradle to grave.”