Accounting for Greenhouse Gas Emissions of Materials at the Urban Scale-Relating Existing Process Life Cycle Assessment Studies to Urban Material and Waste Composition

Although many cities are engaged in efforts to calculate and reduce their greenhouse gas (GHG) emissions, most are accounting for “scope one” emissions i.e., GHGs produced within urban boundaries (for example, following the protocol of the International Council for Local Environmental Initiatives). Cities should also account for the emissions associated with goods, services and materials consumed within their boundaries, “scope three” emissions. The emissions related to urban consumption patterns and choices greatly influence overall emissions that can be associated with an urban area. However, data constraints and GHG accounting complexity present challenges. In this paper we propose one approach that cities can take to measure the GHG emissions of their material consumption: the solid waste life cycle assessment (LCA) based approach. We used this approach to identify a set of materials commonly consumed within cities, and reviewed published life cycle assessment data to determine the GHG emissions associated with production of each. Our review reveals that among fourteen commonly consumed materials, textiles and aluminum are associated with the highest GHG emissions per tonne of production. Paper and plastics have relatively lower production emissions, but a potentially higher impact on overall emissions owing to their large proportions, by weight, in the consumption stream.