Following on from our previous blog which looked at what climate change is, we’re looking at a term the majority of you will have seen, but not always understood – CO2e.
It is often assumed that the ‘e’ in CO2e stands for ‘emissions’ – carbon dioxide emissions sounds perfectly plausible, right? But this is not correct.
In fact, CO2e actually stands for ‘carbon dioxide equivalent’, and it is the standard ratio used to measure greenhouse gas (GHG) output by areas, industries and nations across the globe.
What does CO2e mean?
As mentioned, the term stands for carbon dioxide equivalent. But what, exactly, does this mean?
As we know, CO2 is the largest culprit in terms of GHGs. However, it is important to note that other gases such as methane, nitrous oxide and F-gases also play large roles in climate change – and it is vital that we are able to measure the GHG output accurately and easily.
Each GHG has a specified global warming potential (GWP), and this is measured by two-factors: How effective the gas is at trapping heat while in the atmosphere, and the length of time the gas remains in the atmosphere before breaking down.
So, CO2e is the measure that was first created by the United Nations’ Intergovernmental Panel on Climate Change (IPCC). The gauge was set up in order to make the effects of different greenhouse gases comparable. Due to each gas having its own GWP, it isn’t possible to directly compare them, but with the CO2e measure, it is.
Essentially, CO2e describes the impact of different GHGs, but expresses it in terms of the amount of CO2 that would result in the same amount of warming. Basically, it provides a single metric that groups all GHGs together.
For example, in 2009, the UK released 474 million tonnes of CO2. But if you include its emissions of methane, nitrous oxide and F-gases, the country’s total emissions work out at 556 million tonnes of CO2e. IN other words, those extra gases added the equivalent of 92 million extra tonnes of CO2.
How is CO2e Calculated?
Now for the (slightly) more complicated bit. How are these various GHGs bundled together and calculated as one?
It all has to do with the type of gas, and what its global warming potential (GWP) is. Below is a table that shows some of the main GHGs and what the GWP of each gas is:
As the table shows, the GWP number is an index. CO2 has an index of 1, whilst the GWP index number for other GHGs is the number of times more warming they cause when compared with CO2. For example, one tonne of methane causes 25 times more warming over 100 years when compared to one tonne of CO2 – explaining why the GWP of methane is 25.
In other words, a quantity of GHG can be expressed as CO2e by multiplying the amount of the GHG by its GWP. i.e., if 1 tonne of methane is emitted, this can be expressed as 25 tonnes of CO2e.
As we can see here, CO2e is a very useful term for a number of reasons. Not only does it allow multiple GHGs to be stated as a single number, it also permits different GHGs to be compared in terms of their total global warming impact.
It is also worth noting that CO2e is also sometimes written as “CO2eq”, “CO2equivalent”, or sometimes “CDE”.
Is Your Organisation Doing Enough?
As organisations, we have to ensure we are doing all we can to lower our CO2e emissions, and ultimately make sure that we become neutral in our CO2e output.
Large, and even smaller, organisations are always going to produce more emissions than the individual, and therefore real change needs to start with the corporate and business world.
At BioHygiene, not only are our products kinder to the environment, but we are certified by The Carbon Trust as being carbon neutral, whilst we have recently been certified by Planet Mark – a sustainability accreditation that verifies and measures carbon and social data to reduce emissions and achieve the UN sustainable development goals (SDGs).
| Greenhouse Gas | Global Warming Potential (GWP) |
| Carbon Dioxide (CO2) | 1 |
| Methane (CH4) | 25 |
| Nitrous Oxide (N2O) | 298 |
| Hydrofluorocarbons (HFCs) | 124 - 14,800 |
| Perfluorocarbons (PFCs) | 7,390 - 12,200 |
| Sulfur hexafluoride (SF4) | 22,800 |
| Nitrogen trifluoride (NF3) | 17,200 |
As the table shows, the GWP number is an index. CO2 has an index of 1, whilst the GWP index number for other GHGs is the number of times more warming they cause when compared with CO2. For example, one tonne of methane causes 25 times more warming over 100 years when compared to one tonne of CO2 – explaining why the GWP of methane is 25.
In other words, a quantity of GHG can be expressed as CO2e by multiplying the amount of the GHG by its GWP. i.e., if 1 tonne of methane is emitted, this can be expressed as 25 tonnes of CO2e.
As we can see here, CO2e is a very useful term for a number of reasons. Not only does it allow multiple GHGs to be stated as a single number, it also permits different GHGs to be compared in terms of their total global warming impact.
It is also worth noting that CO2e is also sometimes written as “CO2eq”, “CO2equivalent”, or sometimes “CDE”.
Is Your Organisation Doing Enough?
As organisations, we have to ensure we are doing all we can to lower our CO2e emissions, and ultimately make sure that we become neutral in our CO2e output.
Large, and even smaller, organisations are always going to produce more emissions than the individual, and therefore real change needs to start with the corporate and business world.
At BioHygiene, not only are our products kinder to the environment, but we are certified by The Carbon Trust as being carbon neutral, whilst we have recently been certified by Planet Mark – a sustainability accreditation that verifies and measures carbon and social data to reduce emissions and achieve the UN sustainable development goals (SDGs).
