Employee Commuting Emissions

Customers are increasing asking for this data as part of their sustainability questionnaire. If you supply the UK government with £5m or more of goods or services per annum, you will need to submit a “carbon reduction plan”. As part of the tender or retender, you will need to calculate and report your employee commuting emissions. This reporting requirement is defined in the UK Government’s PPN 06/21, and is part of Scope 3 as defined by the GHG Protocol Corporate Standard.

How can you do the calculations?

Carry out a survey

You conduct a survey to your employees, either paper based or electronically using word document or even a spreadsheet. The survey would need to ask how many days they travelled to work and how often they worked from home during specific period. They would need to tell you the mode of travel they use and the distance travelled.

Some will have used multiple modes of travel, for example car to the station, train to the city and tram to the workplace. They will need to provide the distance for each leg. For some forms of transport finding the actual distances can be difficult. You would then need to collect the responses and analyse them.

Carry out the calculation

For each mode of transport, you will need to work out the emissions. So, for train journey you will need to work out the kilometres travelled by train and then multiply by the appropriate factor from the UK Government GHG conversion factors for company reporting.

That will give you the “combustion emissions” for that mode of transport. You will then need to add the “well-to-tank” (WTT) emissions to give the total GHG emissions for that segment of the journey. A lot of people commute by car. There are various ways of calculating the GHG emissions for cars.

Using the Vehicle Registration Number

The most accurate method uses the Vehicle Registration Number (VRN) to obtain the grams of CO₂ per kilometre and fuel type from the DVLA database.   Then apply the WLTP (Worldwide Harmonised Light Vehicle Test Procedure) real world uplift factor, which is based on the vehicle’s year of manufacture. This is necessary because the manufacturers gamed the emissions calculations. The WLTP aims to adjust for this.

Then you need to convert the grams of CO₂ into grams of CO₂e. This is done by converting the grams of CO₂ into litres of the fuel used by the vehicle and then converting the fuel litres into CO₂e. You use the litres of fuel to calculate the WTT emissions.

For electric cars, it is assumed that the cars are charged from the electricity grid and so they do have GHG emissions associated with the electricity they use. The Government factors have a page of these factors. This also includes plug-in-hybrids.

Using the UK Government Factors

If the VRN is not supplied, then the government factors have emissions factors analysed by 9 market segments. For example, Lower medium, upper medium and executive. Just allocate the vehicle to the correct market segment and use the relevant factor.  However, do not forget the WTT and the emissions associated with the electricity used by electric cars and plug-in-hybrids. It is feasible to do the calculations on a spreadsheet, if rather time consuming.

GHGi Commuting the Easier Alternative

Alternatively, you could use GHGi Commuting. This is our online system where each employee completes a short series of questions about their commuting journey. After confirming the details, the system displays the weekly emissions resulting from their commute. Emissions resulting from any homeworking are also displayed. This immediate feedback is additional motivation for employees to complete the survey, which will result in a higher response rate.

Those with “administrator access” will be able to see the overall data analysed in different ways. For example, by transport mode. These results can be scaled up to account for missing responses, and used as the basis for total commuting emissions of the organisation in the period.  You can also be assured that these rather complex calculations are carried out accurately using the correct factors for the relevant period.