Numerous cities around the world have been exploring their carbon footprint using consumption-based emissions inventories (CBEIs). These inventories differ from the territorial (or “sector-based”) approach typically used to calculate urban greenhouse gas (GHG) emissions, because they include emissions generated outside city borders to produce goods and services for urban residents.

These upstream emissions can be significant, and they are often commensurate with the amount of emissions created within the city itself. A CBEI can lead to insights about where local consumption gives rise to emissions outside a city’s borders, and suggest additional opportunities for reducing emissions.

This report provides an overview of what CBEIs are and how they can be used (i.e., the kinds of insights they can generate, as well as their limitations). It also describes the primary methods for constructing a CBEI, including “rough approximation” methods that can be used where more intensive methods are impractical.