1.2 What is to be measured – the boundary
Before calculating a carbon footprint, you need to decide exactly which parts of the organisation are being measured. For limited companies, it is often best to define the boundaries as being that company; for public institutions, a building- or site-based approach may be more helpful. However, if you are a tenant of an office block with common services (heating, air conditioning), it may be better to try to agree with other tenants to calculate a carbon footprint for the entire building. And if you are working for a company, do you want to bring in the carbon footprint of subsidiary companies or a share of affiliates’ energy use (and footprints)? In truth, it does not matter too much how you choose to set the boundaries: it is more important that you are consistent in your choice, so that you can measure changes to emissions over time; and it is best to concentrate on that part of the organisation over which you have some influence. Beware of adding together disparate activities that may make it hard to interpret the results: for example, if your business both manufactures a product and runs a chain of shops selling that product, it may be better to keep the two activities separate.
The Greenhouse Gas Protocol Initiative website has information about tools for calculating greenhouse gases.
The UK government’s Department for the Environment, Food and Rural Affairs (DEFRA) gives environmental reporting guidelines to help businesses convert existing data sources (e.g. utility bills, car mileage, refrigeration and fuel consumption) into CO2-equivalent emissions by applying relevant conversion factors (e.g. calorific values, emission factors, oxidation factors).
How much influence do you have over your organisation? Setting the boundaries to include only areas under your direct influence may lead to substantial parts not being assessed. Are there other parts of the organisation that can be brought into the process?