Carbon emissions calculator methodology statement

Audience

The calculator has been designed to be as user-friendly as possible. It's primarily geared towards micro, small and medium businesses at an early stage of their climate journey. There is a balance between user experience and accuracy to allow a wide range of businesses to get an estimate of specific areas of their footprint in a straightforward way. User testing and human research showed that businesses needed:

• a simple-to-use calculator to get started
• to learn to become accurate over a three-year period with the goal of getting started in mind

The main purposes of the calculator are to:

• embed good practices
• for the user to have a snapshot of their emissions over a four-year period (one benchmark year, plus three consecutive years)
• estimate emissions and develop accuracy over time through knowledge and good practice
• allow for carbon calculation to become more accessible to early-stage businesses

The goals of this workbook are for businesses to:

• attempt a start with measuring their supply and value chain
• consider becoming more accurate independently of this calculator after three years
• gain the confidence to move onto a more advanced calculating tool
• start to understand and think of their emissions in relation to scopes one, two, and three on initiation and delivery of their actions over the years.

Ferries

For the ferry category, we calculated:

• the average distance travelled and duration for ferry routes within Scotland that are under 40 minutes long
• the average distance travelled and duration for ferry routes within Scotland that are over 40 minutes long

Our idea was that this would make the climate action workbook more user friendly for those just starting their climate journey.

We used timetables from all ferry companies and their routes. We only used Google Maps to calculate distances of those routes where the data is not available directly from the ferry companies.

The conversion factor used is the one averaging all foot and car passengers in the UK.

Limitations to the conversion factors

When calculating the emissions for passenger vehicles, we based this on the average vehicle size declared in the conversion factors on gov.uk. This draws an average from small, medium and large sized passenger vehicles.

We chose not to categorise passenger vehicles by size or specific category to reduce the number of details users would be required to enter on the calculator at this early stage.

Similarly, for waste we chose not to include all the methods of disposal by type of waste to keep the input required by the user to a manageable level. Flight emission calculations are using very broad averages for this version.

The UK Government conversion factors provide much more granular data on flights taken, class of flight and haul. We chose to keep a simplified version for ease of use of the calculator that were informed by those same factors.

We will explore the possibility of adding further advanced breakdowns in a future version of the calculator.

Find all conversion factors on gov.uk.

Vehicles / transport

The vehicles on the calculator also use UK government conversion factors. These include petrol and diesel passenger vehicles, planes, ferries, busses, taxis, trams, and trains.

Mileage by petrol and diesel passenger vehicles is taken from conversion factors drawn across a UK average of small, medium, and large categories.

This let us draw an estimate and reduce the number of touchpoints for a user at an early stage of taking climate action to avoid confusion or feeling overwhelmed.

Passenger vehicles that might be leased as part of scope three hires are the same as those for owned passenger vehicles by a company. So, we merged all under transport category for the purposes of this calculator.

However, businesses will require to separate into scopes one and three at a more advanced stage of their journey / at a later date of their development.

The factors considering biofuel blends are used to represent the main fuel form at standard forecourts. These are provided in litres for businesses who wish to do that instead of miles.

Find all conversion factors on gov.uk.