Page 14 - Methodology to assess Net Zero progress in cities

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GHG emissions = Activity data × Emission factor (1)
II. From a community-wide infrastructure supply chain footprint a Net Zero carbon city implies
Net Zero emissions for some or all the seven provisioning systems (which are associated with
the approximately 90 per cent of global GHG emissions): energy supply, mobility, construction
materials, waste management, wastewater treatment, food systems, and the carbon sequestration
benefits of vegetation. Most current plans for a Net Zero carbon city focus on mobility, buildings
and energy systems, while others include waste (Seto et al., 2021). This approach excludes local
operational energy use by businesses (e.g., hotels, restaurants, industries) that serve tourists or
export goods and services elsewhere.

Consumption-based GHG accounting expands the seven key provisioning sectors by assigning
source-based GHG emissions from all sectors of the economy, wherever they occur, regardless of
the territory, to final consumption by households and governments within a city (Seto et al., 2021).

III. From a consumption-based perspective a Net Zero carbon city implies that all households
and government expenditures are Net Zero.

Total community-wide GHG footprinting is an emerging approach that includes upstream and
downstream supply chain emissions associated with all community-wide activities, i.e., including
local and final consumption by households, government, and exports (Seto et al., 2021).

IV. From a total community-wide supply chain footprint a Net Zero carbon city would imply that
not only imports to local households but also exports from local businesses are Net Zero. This
will require global governance of carbon embodied in trade, inside and outside cities, which
goes beyond the boundary of a city (Seto et al., 2021).

1 Activity data is a quantitative measure of a level of activity that results in GHG emissions taking place during a given
period (e.g., volume of gas used, kilometers driven, tons of solid waste sent to landfill). An emission factor is a measure of
the mass of GHG emissions relative to a unit of activity. For example, estimating CO emissions from the use of electricity
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involves multiplying data on kilowatt-hours (kWh) of electricity used by the emission factor (kgCO /kWh) for electricity,
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which will depend on the technology and type of fuel used to generate the electricity (ICLEI, 2021).

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