When calculating an organization's greenhouse gas inventory, footprint activity data is gathered across the organization and its value chain.
Activity data is a quantitative measure of an activity an organization engages in that results in the emission of greenhouse gasses.
Some examples include:
For each activity, the source of the data must be identified. For instance — will the data come from a utility bill or will it come from a meter on-site? The footprint source or type of activity data will affect the accuracy of the emissions calculation.
To begin the process of calculating an emissions estimate, each unit of activity data must be converted into the quantity of GHG emitted as a result of that activity.
Oftentimes, a single activity type can produce more than one type of greenhouse gas.
The combustion of natural gas typically produces carbon dioxide, methane, and nitrous oxide.
An emission factor is a factor that converts activity data — like the combustion of natural gas — into greenhouse gas emissions data.
Some examples of emission factors are shown: