SOE banner

What is CO2e?

CO2e is an abbreviation of 'carbon dioxide equivalent' and is the internationally recognised measure of greenhouse emissions.

There are many types of greenhouse gases. Six such gases are controlled by the Kyoto protocol. These include:

  • carbon dioxide (CO2),
  • nitrous oxide (N20)
  • methane (CH4)

and a range of synthetic (industrial) gases including

  • perfluorocarbons (PFC)
  • hydrofluorocarbons (HFC),
  • sulphur hexafluoride (SF6).

Each of these gases has a different capacity to heat the atmosphere. This is referred to as their global warming potential (GWP).

CO2 is the standard bearer for GWP - it has been assigned a GWP = 1. Other GWPs include:

  • methane GWP = 21.
  • nitrous oxide GWP = 271
  • perfluorocarbons GWP = 6,000-9,000
  • hydrofluorocarbons GWP = 1,000-10,000
  • sulphur hexafluoride GWP = 23,900

Clearly, CO2 is not a potent greenhouse gas compared to the others. However, because CO2 is produced in such huge quantities, its effect dwarfs all the other greenhouse gasses combined.

For the sake of ease, when an organisation calculates its greenhouse emissions these are reported as though they were equivalent to a given volume of CO2. This is the CO2e.

For example, greenhouse emissions from a landfill of 100 tons of methane are recorded as 2,100 tons CO2e.

Using CO2e as a measure of greenhouse emissions allows for comparing the greenhouse impact of a variety of greenhouse emissions sources.

Calculate your own CO2e
with the SEA O2 Greenhouse Calculator (.xls)

Read More

International Emissions Trading Association
Science of Global Warming

Framework Convention on Climate Change
Climate Change Information Kit

Supply of fuels and energy with a reduced environmental impact