Carbon Dioxide Equivalent (CO2e)
- Carbon dioxide is not the only greenhouse gas; there are other key greenhouse gases that contribute to global warming, these are: Methane, Nitrous Oxide, Fluorinated gases (e.g. Hydrofluorocarbons, Perfluorocarbons and Sulphur Hexafluoride) and Water Vapour.
- Even though water vapour is the most common greenhouse gas, it is a natural part of the atmosphere and water cycle, so monitoring is not necessary.
- Each Greenhouse Gas varies in potency, which relates to their ability to trap heat in the atmosphere measured against the time they are present in the atmosphere. Carbon dioxide is the most common greenhouse gas, but it is not the most potent or powerful.
- For example, over a timescale of 20 years methane is around 80 times more potent than carbon dioxide. This is because the lifetime of methane in the atmosphere is about 12 years, and so its global warming potential reflects this. Longer lasting gases such as nitrous oxide can stay in the atmosphere for over 100 years and so its global warming potential remains high over a longer period, about 265 times more potent than carbon dioxide over 100 years.
- To make things easier to measure and compare the values shown in a carbon footprint are standardized relative to carbon dioxide and expressed as a single value termed the carbon dioxide equivalent (CO2e).
- CO2e accounts for the seven main Greenhouse Gases that contribute to climate change, as detailed in Table
- 2CO2e conversion factors are set by the Department for Business, Energy & Industrial Strategy (BEIS) on an annual basis.
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Greenhouse Gases |
Main Sources of Greenhouse Gases |
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Carbon Dioxide (CO2) |
Coal, Oil and Gas (Fossil Fuels) Manufacturing Cement Production Deforestation |
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Methane (CH4) |
Livestock Organic waste/Landfill escape Emitted during production of fossil fuels |
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Nitrous Oxide (N2O) |
Agriculture fertiliser Waste management Fossil fuel burning |
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Fluorinated Gases (F-Gases): -Hydrofluorocarbons (HFCs) -Perfluorocarbons (PFCs) -Sulphur Hexafluoride (SF6) -Nitrogen Trifluoride (NF3) |
Refrigeration Aerosols
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