CO2 Equivalent (CO2e)
A universal unit for expressing all greenhouse gas emissions on a comparable basis — by multiplying each gas's quantity by its Global Warming Potential (GWP) relative to CO2.
CO2 equivalent (written as CO2e or CO2eq) is the standard unit for expressing greenhouse gas emissions in a single, comparable measure. Because different greenhouse gases have different heat-trapping potencies, they are converted to their carbon dioxide equivalent using Global Warming Potential (GWP) values published by the IPCC.
How CO2e is calculated
CO2e = Mass of gas (tonnes) × GWP of that gas (100-year time horizon)
Using IPCC AR5 GWP values:
- 1 tonne CH4 = 28 tCO2e
- 1 tonne N2O = 265 tCO2e
- 1 tonne R-410A (HFC) = 2,088 tCO2e
Why CO2e matters for BRSR
BRSR Principle 6 requires total Scope 1 and Scope 2 emissions reported in metric tonnes CO2 equivalent (tCO2e). This means all combustion-related gases (CO2, CH4, N2O) and any fugitive emissions (refrigerants) must be converted and summed into a single tCO2e figure per scope.
GWP version matters
IPCC publishes updated GWP values with each Assessment Report (AR4, AR5, AR6). GHG Protocol Corporate Standard currently recommends AR5. Always document which GWP version was used in your GHG inventory methodology — different versions produce slightly different totals and must be consistent year-over-year.