Cities start with defining an inventory boundary. This identifies the geographic area, time span, gases and emission sources covered by a GHG inventory. Any geographic boundary may be used for the GHG inventory. Depending on the purpose of the inventory, the boundary can align with the administrative boundary of a local government or a combination of administrative divisions, a metropolitan area, or another geographically identifiable entity. Calculations are designed to account for GHG emissions in a single reporting year.
GHG emissions from city activities shall be classified into six main sectors:
- Stationary energy
- Industrial processes and product use (IPPU)
- Agriculture, forestry, and other land use (AFOLU)
- Any other emissions occurring outside the geographic boundary as a result of city activities.