The term Carbon Dioxide Equivalent, or CO2e, is a standard unit for measuring carbon footprints. Ecometrica explain that “for any quantity and type of greenhouse gas, CO2e signifies the amount of CO2 which would have the equivalent global warming impact”.

In order to convert greenhouse gas emissions to CO2e, these are multiplied by the gas’s Global Warming Potential (GWP).

Quick note on GWP: this takes into account that all the different types of greenhouse gases will have different levels of warming impact on the Earth, compared to CO2, per unit mass. To get to a standard unit of measurement, i.e. CO2e, this warming impact needs to be considered. A full list of greenhouse gases and their global warming potential can be found here.

CO2e is very useful as it allows any greenhouse gas to be expressed as a single unit, and allows comparison across the different gases.

The main way that Sage Earth calculates CO2e is by what the Greenhouse Gas Protocol refers to as the ‘spend-based’ approach to carbon accounting. This means we calculate a carbon footprint (in tonnes of CO2e) by multiplying an amount of expenditure (in £) by a carbon dioxide conversion factor - which tells us the CO2 emissions emitted over the production of particular good or service. A carbon conversion factor is produced by an extensive data analysis, which can vary across countries, industries, suppliers and even transactions.