Climate change inducing emissions that are in the remit of cities can be largely categorised into three main areas: stationary energy, transport and waste. These emissions come about due to the consumption of fuels, either directly like gas and petrol, or indirectly through electricity consumption, or via the production of waste. In order to model an emissions projection we consider how the city is expected to grow, what impact that will have on the consumption of resources and production of waste, and how emissions intensive that consumption/production will be.
Activity in cities is broken into “sectors”, three residential sectors and five non-residential:
- Residential:
- Attached housing
- Detached housing
- Multi unit housing
- Non-residential:
- Commercial
- Retail
- Industrial
- Health
- Education
Climate change causing emissions result from consumption or production of various resources which, for each of the above sectors, depends linearly on their size, measured by resident population for residential sectors and jobs for non-residential sectors. These resources include:
- Electricity
- Gas
- Internal combustion car kilometres travelled
- Electric car kilometres travelled
- Train kilometres travelled
- Bus kilometres travelled
- Ferry kilometres travelled
- Kilometres travelled by other transport modes
- Landfill waste
- Recyclable waste
- Food and organic waste
Each sector produces or consumes a constant amount of the above resources per unit of land use (population or jobs). This is called the “intensity” of consumption for the resource/land use pair.
Finally, each resource produces a constant amount of climate change inducing emissions per unit known as the “emissions intensity” of the resource.
To project the emissions of a city we must gather data on
- Land use and how it is expected to change over time
- The consumption/production intensities of the land use categories for all activities that result in carbon emissions, and
- The emissions intensities of the above resources
Scope of emissions
Projecting emissions in this way models full scope emissions, that is, scopes 1+2+3. The scope of emissions are incorporated into the emissions factors.
Since emissions are computed for particular locations (LGAs or suburbs) emissions due to commuting are assigned to the residential sector in order to avoid double counting.
Finally, the “industrial” land use does not include businesses that generate emissions as part of their industrial processing, only via their consumption of electricity, gas and via their vehicle fleet. For example, large scale electricity generators, mines and grazing land are not included. This is to ensure emissions are, again, not double counted and as these land uses are rare in metropolitan areas this is a valid simplification.