Post 49. Carbon accounting - what is carbon dioxide equivalent?

 

What is carbon dioxide equivalent or global warming potential?

Carbon dioxide equivalent” or “CO2e” is used in carbon calculations for combining and summarising the 'overall global warming impact' of different greenhouse gas emissions to a single metric in terms of CO2. 

The global warming potential or GWP is a measurement to determine the ability of each greenhouse gas to absorb heat in the atmosphere, so GWP is the amount of energy, the emissions of 1 ton of a gas will absorb over a given time period, usually a 100-year averaging time, compared with the emissions of 1 ton of CO2. [1] However some gases although they absorb more heat in the atmosphere they do not have such a long residency period in the atmosphere, e.g. methane, so this is taken into account with the GWP.

The greenhouse gases most commonly considered are carbon dioxide (with a 100 year GWP or GWP100 of 1), methane (GWP100 of 25) and nitrous oxide (GWP100 of 298) and chlorofluorocarbons where the GWP100, depending on the chemical is in the thousands.[2] 

Which sectors have the highest methane emissions?

Globally

Agriculture 141 mt (t = tonnes)

Energy        135 mt  

Waste.           73 mt [3]

But.... this ratio varies by country .... and also agriculture sequesters carbon too so has the opportunity as a business it it follows certain practices to be carbon-neutral...

Sources

[1] https://doi.org/10.1016/C2017-0-02742-8 

[2] https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10-2.html

[3] https://www.iea.org/articles/methane-tracker-database