We all know that carbon dioxide (aka CO2) is bad, yes? That has been drilled into us for well over 20 years. CO2 is a greenhouse gas, and therefore CO2 emissions should be avoided at all costs, at least if we want life to continue without increasingly frequent droughts, floods, storms or [insert favourite natural disaster here].
This is probably why people tend to look at me funnily when I argue that CO2 can actually help save the planet from the disaster we are hurtling towards.
Enter CO2 as a refrigerant!
Say again? A what? Most people have never stopped to consider exactly how their beer (or favourite snack) stays cold in the fridge, or how limited-life-span veggies stay fresh on their trip halfway around the world. But, in order for these things to happen, we need refrigerants.
What is a refrigerant?
A refrigerant is a substance that evaporates when absorbing heat – and in the process cools down whatever it absorbs the heat from, like the food in a refrigerator. This evaporated gas can then be condensed back into its original form using a compressor and some electricity. And, voila, it is ready to absorb more heat. This cycle, called a vapour-compression cycle, is what drives most refrigeration and air-conditioning equipment.
All refrigerants used in such equipment have an impact on the climate. Therefore they have been given a so-called Global Warming Potential (GWP) value. The GWP indicates the magnitude of a refrigerant’s greenhouse gas effect, making it easier comparing the climate-effects of different types. CO2 — which is also called R744 when used as a refrigerant — has a GWP value of 1.
Why is CO2 not just bad?
Now we are arriving at the crux of the matter, because synthetic refrigerants (f-gases) have GWP values that, in many cases, are thousands of times higher. Two of the most popular f-gas refrigerants over the last 20 years around the world are called R410A and R32. R410A has a GWP of 2,100 and R32 has a GWP of 771. In other words, R410A’s effect on the climate is more than two thousand times bigger than CO2’s. So, just to hammer home the message… 1kg of R410A released into the atmosphere is 2,100 times as bad for the climate as 1kg of CO2!
So, in conclusion: CO2 refrigerant has a small effect on the atmosphere, and is contributing to climate change if it escapes the refrigeration equipment. BUT, when it comes to refrigerants the alternatives are thousands of times worse.
We need CO2 for cooling
Why is this important? Could we not just stop using cooling? No, I don’t think so. I’m pretty sure the world at large is not willing to give up its cold comforts, especially not with the climate getting hotter all the time. We also need to cool medicines like COVID-19 vaccines.
So, if we can’t live without cooling, we need to choose refrigerants (like CO2) with the smallest possible climate effect to avoid making the situation even worse.
In 2016, the Kigali Amendment to the Montreal Protocol was adopted. The Kigali Amendment is an international agreement that calls upon countries to phase down the use of f-gases called HFCs. The UN has calculated that if the amendment is fully implemented, we can save up to 0.4°C of global warming in the 21st century.
That may not sound like much. However, when we consider that we are currently on track for more than a 3°C increase in temperature, and we are trying to reduce that to 1.5°C, then suddenly a 0.4°C reduction is a big deal.
In other words, replacing the hugely impactful f-gas refrigerants with CO2 can actually help save us from the climate crisis, not make it worse.
So, as usual, life is not purely black and white. When it comes to the climate it is a nice muddy brown. CO2 is not just the bad guy mucking everything up. It could be a useful tool when used to phase out even worse gases while continuing to enjoy a cold beer or running the AC on a hot day.
NOTE on CO2 emissions!
This doesn’t mean that CO2 emissions from burning fossil fuels are suddenly unproblematic, most certainly not. It’s a matter of choosing the least bad option, and in the case of refrigeration, that means choosing CO2.