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A consistent methodology is important to ensure an accurate result, particularly in a large organisation which depends on many individuals to help collect and interpret data.
Some organisations choose to define their own approach for carbon footprinting, however, it is usually advisable to use an existing and recognised methodology that is already widely accepted and understood. The results may be seen to be more credible, and can be compared with other organisations using the same methodology.
One commonly used methodology is the GHG Protocol produced by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD). This methodology provides detailed guidance on corporate emissions reporting and is available free of charge online. A more recent standard from the International Organization for Standardization, ISO 14064, also provides guidance on corporate footprint calculation and emissions reporting. It builds on many of the concepts introduced by the GHG Protocol; both provide explanations of the steps covered here.
- Specify the boundary and scope of coverage
Be clear about which set of emissions will be quantified. This is commonly referred to as defining your ‘boundary’. Common issues include:
- Treatment of emissions from wholly or partially owned subsidiaries
- Treatment of emissions from leased assets, such as from a van which is leased from a hire company.
It is usual to define the boundary to include the full range of emissions that the organisation controls directly and this is likely to include subsidiaries and leased assets. Established methodologies such as the GHG Protocol provide rules for allocation of the emissions to the organisation.
Having defined the boundary, consider what types of emissions will be included. Ask the following questions:
- CO2 only or all greenhouse gases?
- Direct emissions from fuel use onsite and from transport?
- Direct emissions from manufacturing processes onsite?
- Emissions from the electricity the organisation purchased?
- Emissions from the organisation’s supply chain and other activities for which the operation is indirectly responsible, such as outsourced activities or manufacture and transport of raw materials, by another company, which your organisation then uses?
The GHG Protocol and ISO 14064 provide helpful guidance and accepted standards on these questions.
- Collect emissions data and calculate the footprint
The accuracy of the footprint relies on the ability to collate and analyse data relating to as many of the defined emissions as possible.
For gas and electricity, collect consumption data in MWh or kWh . Data for other fuels can be collected in a variety of units, for example, kWh, MJ, litres and so on. For transport emissions it may be necessary to estimate the total fuel consumption based on the mileage of the vehicles and fuel economy assumptions.
GHG emission data can generally be translated into equivalent CO2 emissions data using standard emissions factors, as described above. For some emissions sources, more complex calculations may be required.
Before collecting the data, decide what level of accuracy is required, and how much margin for error is acceptable.
- Verify results (Optional)
Having a carbon footprint verified by a third party, such as a consultancy or accountancy firm can lend credibility to an organisation’s claims. Verification typically involves analysis of the methodology, data collection techniques and the calculation process that was used.
Different levels of assurance or verification of your results are available. Greater levels of assurance or verification are more onerous and expensive to achieve, but provide greater confidence in the results.
- Disclose the footprint (Optional)
Whether the footprint is disclosed in advertising material, a CSR report or other collateral, ensure that the data is presented transparently, providing full information about the process followed and what the information means.
Make the following information available:
- The methodology
- What boundary conditions were set and which types of emissions are included and excluded
- The data collection techniques, including what level of accuracy was achieved and any assumptions or estimates that were required
- The level of verification of the results provided by independent third parties.
Throughout the process of calculating a carbon footprint, always be clear, consistent and transparent.
For an indication of your carbon emissions, use our online tools:
Now read Using a carbon footprint for carbon management
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