First, the bad news. Companies that make PFAS “forever chemicals” believe the explosive growth of data centres gives them a big new market. As ChemSec revealed this week, they are already expanding production accordingly.
The good news is that data centre development is still at a relatively early stage and there is still time to put this toxic genie back in its bottle. Better still, the majority of data centres don’t use PFAS cooling systems at all — or at least not yet.
Commercial alternatives already exist that can cool AI technology just as efficiently and much more safely. Plus, there are natural refrigerants that tick all the boxes for truly sustainable cooling. With all the talk in Brussels this week about “clean” AI, we need a clear focus on PFAS-free technology.
As part of our series of expert interviews on PFAS, ChemSec spoke to Marc Chasserot of ATMOsphere, an independent market accelerator with a mission to clean up data centre cooling.
There is still time to put this toxic genie back in its bottle
Marc, why do data centres need to be cooled in the first place? How big is the problem?
A data centre is basically a warehouse full of servers. They use a lot of electricity. For example, Ireland’s data centres already account for close to a quarter of the country’s electricity consumption, up from just 5% a decade ago.
Lots of energy means lots of heat. Up to now, building your data centre somewhere cold, like Ireland, has been enough to keep the temperature down.
But the industry is experiencing incredible growth thanks to the rise of AI. This has led to more servers packed closer together, which in turn means the heat cannot dissipate in the air nearly as effectively.
As a result, more companies have begun investing more in liquid cooling technologies. Liquid cooling is growing faster than any other segment and industry insiders estimate they will make up around 30% of the data centre market by 2028.
‘News flash! PFAS-free cooling is far and away the most used method’
So where do PFAS come into all this?
When air alone cannot do the job, liquids are used instead. This is where PFAS producers are hyping their solutions.
For data centres, there are two types of liquid cooling technologies:
- “Direct-to-chip” cooling, which works rather like a home refrigerator: liquid circulates through sealed pipes or channels around the server and carries away the heat.
- “Immersion cooling”, where the entire server is submerged in liquid, like running a boiled egg under cold water.
One more detail: when the liquids in these systems evaporate, this is known as two-phase cooling. When the liquid remains a liquid, it is called single-phase cooling.
News flash! Single-phase, PFAS-free cooling is far and away the most used method (whether immersion or direct-to-chip). It will remain so for considerable time. It is the easiest to retrofit, the cheapest to deploy, and most of all it has proven reliable.
Single-phase cooling relies on liquids such as water, glycol (a kind of alcohol), and synthetic fluids derived from oil and gas. Moreover, big companies already service this market, including some of the major players like Shell, ExxonMobil, Castrol, TotalEnergies, Petronas, Cargill and others.
Certainly no need for PFAS here.
So where do PFAS come in? Why use them at all in data centre cooling?
Two-phase technology does have its advantages on paper. It can offer better heat transfer, and lower water and energy use. PFAS chemicals evaporate at much lower temperatures, which make them the go-to solution for two-phase cooling.
These compounds belong to a category of PFAS known as F-gases. Producers are hyping a new generation of F-gases that have low global warming potential, which, together with energy and water efficiency, allows manufactures to dress them up as “sustainable”.
It is important to stress that two-phase PFAS cooling is still a niche technology. The vast majority of data centres still rely primarily on air-cooling, and use of single-phase PFAS-free liquid-cooling is growing quickly.
And there are excellent reasons not to use PFAS-based cooling systems. They use huge quantities of these chemicals, leak PFAS into the environment, the factories that make them pollute rivers, air and soil, and they present significant problems at end of life when it is necessary to dispose of them. There is nothing “sustainable” about PFAS.
This is a fast-moving market. Single-phase immersion cooling is becoming more efficient. The search is on for hydrocarbon solutions for two-phase cooling. Data centres therefore need to install cooling systems that can be updated as the technology develops, otherwise they risk making PFAS solutions permanent by default.
(Continues below…)
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Are there efficient cooling technologies that don’t use PFAS?
I already mentioned how liquids derived from oil and gas are far more widely used than PFAS in data centre liquid cooling solutions. Also, a substantial portion of data centre demand for cooling includes the mechanical cooling done by chillers and air conditioning units. The heat-rejection loops that move the heat out of the building also require liquid cooling, as do any heat pumps that capture waste heat.
Natural refrigerants such as CO2, ammonia, isobutane and propane can satisfy these cooling requirements. The technology is proven and already running at commercial scale. Here are some examples:
- Penta Infra’s Hamburg data centre runs on propane chillers that beat synthetic alternatives on efficiency and cost.
- Zudek’s ammonia unit at a German data centre cut cooling energy use by 43%.
- M&M Carnot reports that CO2-based data centre cooling can cut energy use by up to 70%.
- Advansor’s CO2 system in Spain was among the first anywhere to use CO2 for data centre cooling.
- Fenagy’s hydrocarbon heat pumps in Finland are recovering enough waste heat from a data centre to warm roughly 3,500 homes.
More detail about these and other projects can be found in ATMO’s recent report on clean cooling for data centres.
Is AI possible without massive damage
to the environment?
The scale of the challenge is considerable, but it does not depend on how much AI the world uses — it is determined by the choices we make through democratic control of the technology.
Three things, done together, can decouple AI’s growth from environmental harm:
- Power new capacity with clean, green, low-carbon energy rather than backfilling with fossil fuels.
- Re-use waste heat to make homes warmer.
- Get the cooling technology right so it becomes part of the solution instead of a second, far more permanent, liability.
Widespread AI adoption without massive environmental damage is achievable. Single-phase and closed-loop natural-refrigerant engineering is already running at commercial scale today, and it is ready and waiting for the rest of the industry to build on.
But this cannot be an afterthought. Once PFAS is in water and soil, there is no realistic way to clean it up. That is why it deserves the strictest attention now, while the choices are still ours to make.
This interview is Part 4 of a series. Read also:
- Part 1 on the scale of the PFAS problem
- Part 2 on substituting PFAS with safer alternatives
- Part 3 on why F-gases are obsolete.
