CO₂e is Carbon Dioxide Equivalence.

There are a number of "greenhouse" gases. Each contributes to the effect to a differing degree. The CO₂e value gives a measure of the effect of a given amount of a particular greenhouse gas in terms of the amount of CO₂ that would be needed to have the same effect.

The equivalence of a gas is a useful benchmark as people who are familiar with CO₂ may not necessarily understand the impacts of releasing a large quantity of methane or other greenhouse gas.
When calculating how much effect a given gas is having you need to multiply the volume by the CO₂e value.

Here are some examples of greenhouse gases and their CO₂e values.

• carbon dioxide (CO₂) = 1 CO₂e
• methane (CH₄) = 19 CO₂e
• sulphur hexafluoride (SF₆) = 21,682 CO₂e

As you can see the CO₂e value can have a vast range. One tonne methane is equivalent to 19 tonnes of CO₂, whereas one tonne of sulphur hexaflouride is equivalent to over 21 thousand tonnes of CO₂.