CO2 vs CO2e: What’s the difference

A footprint surrounded by flowers

Today we’re taking another look at the terms, tactics, and technicalities that we see in discussions of environmental sustainability, and we’re getting down to basics. 

How should companies measure and report on their environmental impact? 

We’re currently in the process of revising our climate footprint numbers to account for the introduction of electrified rail into our logistics network (don’t worry, the numbers are going down!) So, we wanted to take the time to say why we say “climate footprint” rather than “carbon footprint” and why our numbers are in CO2e rather than CO2. 

What is the difference between CO2 emissions, and CO2e emissions, and why do some companies report their emissions differently? Time to unpack the numbers. 

A power plant burning fossil fuels

What Is CO2?
Carbon dioxide (CO2) is a colourless, odourless gas that’s released into the atmosphere through things like burning fossil fuels, deforestation, and agriculture. When it’s released into the atmosphere CO2 traps heat in what has been called the “greenhouse effect.” This is the process that’s changing our climate.

The role of CO2 in atmospheric heating is well established. In 1896, the Swedish physicist Svante Arrhenius discussed the possibility that carbon dioxide released into the air by human activity could have an effect on the temperature. By 1938 the possibility was being tested. Amateur scientist Guy Callendar collected temperature reports from weather stations all over the world, and, calculating the numbers by hand, discovered that temperatures were rising. As a steam engineer, Callendar was part of an industry that was burning huge amounts of coal, and so he was well placed to conclude that the two were related; CO2 released by human industry was changing the climate, just as Arrhenius predicted it could.

It took decades for Callendar’s findings to become widely accepted in the scientific community, but by now we have so much evidence that it’s indisputable. We know that man-made emissions are changing our climate, and we know that it’s critical that we reduce these emissions as rapidly as possible. 

But climate change is bigger than just CO2. As climate science has progressed we have started to see a much fuller picture of how human activity is warming the planet, and we’ve found that carbon dioxide is not the only gas trapping atmospheric heat and causing the greenhouse effect. 

A glacier melting

What are the other greenhouse gases? 
The machines and processes we currently use in transport, manufacture, agriculture and energy are generating six other main gases, along with carbon dioxide, that are contributing to the greenhouse effect. These include:

Methane (CH4): Methane is much more effective at trapping heat in the atmosphere than CO2—about 28-36 times more potent over a century. It’s released from various sources like natural gas and oil production, the digestive processes of livestock (especially cows), and decomposing organic waste in landfills.

Nitrous Oxide (N2O): Nitrous oxide is even more powerful than methane, around 298 times stronger than CO2 at warming the atmosphere over a 100-year period. Major sources include agricultural activities, such as the use of fertilizers, as well as the burning of fossil fuels.

Fluorinated Gases: These synthetic gases include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). They are often used in industrial applications like refrigeration and air conditioning. Despite being released in smaller amounts, fluorinated gases can be thousands of times more effective at trapping heat compared to CO2 and can stay in the atmosphere for a very long time. 

A greenhouse with lots of succulents

Why does it matter? 
That’s a lot of names and numbers! It boils down to this: it’s bigger than just carbon dioxide. 

If we want to understand how human activity is contributing to climate change, we need to account for all of these gases. And if we want to understand the impact of a particular company, we need totals for all of them.  

But that’s a tall order. Giving counts for all seven of the main greenhouse gases would mean each company reeling off a long list of chemical names and numbers that wouldn’t mean much to anyone other than climate scientists.

So how do companies report on their total greenhouse gas emissions in a way that’s simple and succinct? Time to meet a little “e”. 

A green laptop next to a tablet and an open book

What is CO2e?
CO2e stands for carbon dioxide equivalent. It’s a way of expressing the impact of all greenhouse gases in terms of the amount of CO2 that would have the same global warming effect. 

Let’s do a really simple example with the fictional toilet roll company Green Roll. 

Green Roll have calculated the total for all the greenhouse gases that are emitted as they manufacture their products. They’ve found that the raw material supply, transport, manufacturing, and general operations of Green Roll emits 100 tonnes of CO2, 1 tonne of methane, and half a tonne of nitrous oxide. 

We know that methane is at least 28 times more potent than CO2 when it comes to heating the planet; every tonne of methane will have the same heating effect as at least 28 tonnes of CO2. Nitrous oxide is even more potent, half a tonne of nitrous oxide has the same heating effect as 149 tonnes of CO2. 

So to get a single number that gives us an idea of how much the emissions of Green Roll are heating the planet, we take the 100 tonnes of CO2, and add another 28 tonnes for the methane, and another 149 tonnes for the nitrous oxide.

The final number is 277 tonnes CO2e. All of the greenhouse gases, added together, are warming the planet as much as 277 tonnes of carbon dioxide would.

This fictional example shows two things:

-The totals for CO2 (100 tonnes) and CO2e (277 tonnes) are completely different.

-and if the goal of the exercise is finding out how much Green Roll is contributing to climate change, CO2e is the number that matters. 

This is why CO2e is used, instead of CO2. In this fictional example, Green Roll could report a “carbon footprint” number of 100 tonnes of CO2, and if you didn’t know about the other greenhouse gases, you wouldn’t see how much was being left out.

A magnifying glass over an orange light

Climate science has moved on since the days of Guy Callendar’s calculations. We now know that carbon dioxide is an important part of global warming, but it is far from the only part of it.

If you’re only seeing numbers in CO2, you’re not seeing the whole story. At Naked Sprout, we know we have a responsibility to report on our impact as thoroughly and accurately as possible. This is why we talk about our “climate footprint,” rather than our “carbon footprint,” and why we report in CO2e, not CO2. By reporting our emissions in CO2e, we provide a comprehensive and accurate picture of our environmental impact, considering all greenhouse gases and their full life cycle, from cradle to grave. 

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