To save water, servers are bathing in a forever chemical

A tank, some motherboards, and a liquid that boils

The technique is called two-phase immersion cooling: servers are lowered into a tank of liquid with a low boiling point. Against the hot components the fluid boils, and the vapor condenses back on a water-cooled coil.

Almost no water lost to evaporation, no cooling tower: the sales pitch is real. The liquid itself belongs to the PFAS family, the fluorinated compounds known as forever chemicals because the carbon-fluorine bond doesn't come apart in nature.

We spent the summer showing that data center water use is badly measured. Here's the technology sold as the way to stop using it.

So how much of the stuff gets made? Nobody knows. The Swedish NGO ChemSec, which publishes its ranking of the world's ten biggest producers this morning, says so in black and white in its methodology: volumes aren't available anywhere.

The report that set off the week

Its survey describes ten groups, nearly all of them announcing expansions in Europe, Asia and North America. Executive director Anne-Sofie Bäckar puts it this way: "These companies' expansion plans show that unless governments and regulators insist on a rapid phaseout, we will face a new tidal wave of forever chemicals."

Three demand drivers get named: AI and data centers, semiconductors, batteries. Several producers explicitly frame their investments around the "AI revolution."

What the ranking actually counts

Three screens down sits the methodology section. Here's what it says. The list rests on "the number of PFAS substances chemical companies produce or import in the European Union or the United States," and, the industry being extremely opaque, "there is unfortunately no available information on production volumes." Next sentence: "Companies are sorted in alphabetical order."

ChemSec does not stop there, and that deserves quoting. In the same methodology, the NGO writes that "through our own data sources that we have built up over many years, as well as digging into public company documents, ChemSec is confident in saying that the companies named below are the biggest PFAS producers in the world." The organisation claims a conviction built on years of groundwork, even as the published ranking can only be alphabetical.

So it isn't a tonnage league table. It's a count of regulatory filings in two jurisdictions. Chemours declares 57 substances, Arkema nine, Daikin five in the EU. Nothing in there tells you which of the three makes the most material.

The demonstration comes from ChemSec itself. A "(dis)honourable mentions" section names China's Dongyue, Russia's HaloPolymer and India's Gujarat Fluorochemicals separately, as companies that "would probably make the list if everything were 100% transparent." The map leaves out the places where nothing is declared: a radar that only picks up the planes flying with their transponders on.

One more detail: of the seven companies whose count can be compared with three years ago, all seven declare fewer substances today. Without that proving any retreat either, since a plant can put out more tonnes of fewer molecules. The number says nothing about a rise or a fall, because it says nothing about production.

What is on the record, though

Arkema, the French group, is on the list. Its press release of August 28, 2025 announces a 15 kt unit at Calvert City, Kentucky, for roughly $60 million. The Guardian quotes half a sentence: the investment "will enable us to follow the rapid expansion of data centers cooling needs."

The full sentence, from senior vice-president Laurent Tellier, starts somewhere else: "This investment confirms our commitment to support the transition of the foam industry towards low GWP solutions, and will enable us to follow the rapid expansion of data centers cooling needs." Forane 1233zd is an HFO, first of all a blowing agent for insulation foam, made on a converted HFC line and sold on a 99% cut in GWP. Data centers come afterwards, introduced by an "in addition."

One climate rule pushes toward this product, one chemicals rule targets it, and nobody has settled that.

The heaviest number in the file

To weigh the social cost of PFAS, ChemSec cites a European Commission estimate: 440 billion euros "for Europe alone." We went and opened the document: 606 pages, delivered in January 2026 to the environment directorate-general by the consultancies WSP, Ricardo and Trinomics.

The figure is in there, and here is what it says. The 440 billion is the total present value over 2024-2050 of quantifiable costs, in the first of four scenarios studied, the business-as-usual one. Stopping production and use altogether still costs 330 billion. The annual cost, for its part, is a different order entirely: 39.5 billion for health in 2024, and 3.8 billion for clean-up.

Three caveats, all written by the authors themselves. The study priced "only four of potentially 10,000 substances," hence their conclusion that the values "likely represent a lower bound" on the real damage. The sensitivity range on health runs from 0.05 to 5,750 billion, a thermometer hesitating between 0 and 80 degrees. And the document notes that it "reflects the views only of the authors."

Last point, checked across the 606 pages: the phrase "data center" doesn't appear once. This number measures legacy pollution. AI-driven expansion isn't part of it.

The tank isn't the real story

So how much does PFAS two-phase immersion actually weigh? Not much. Per the Uptime Institute, 22% of operators were running some form of direct liquid cooling in early 2024, on 10% of their racks or fewer. Among those, water cold plates dominate by a wide margin, with the other technologies trailing well behind. Single-phase immersion, meanwhile, runs on mineral or vegetable oil, no PFAS involved.

More to the point, the incumbent supplier walked away: 3M announced in December 2022 that it would exit all PFAS manufacturing by the end of 2025, which takes Novec and Fluorinert, the reference fluids for the process, with it. LiquidStack's chief executive reckoned at the time that the blow landed elsewhere, on chip etching.

That's where the dependency gets heavy. An investor note from Danske Bank, quoted by the Guardian, describes PFAS as essential ingredients in "as many as 1,000 distinct steps" of making a microprocessor. The tank of servers makes the picture; the cleanroom makes the volume.

Europe's restriction won't be settled on tonnage

Will that demand sweep away the European PFAS restriction? That isn't how the procedure works.

ECHA's Committee for Risk Assessment issued its final opinion on March 3, 2026: it backs a universal ban. The Committee for Socio-Economic Analysis has held since March that a short transition wouldn't be proportionate and that further derogations might be needed. Its final opinion is expected by the end of 2026.

What decides things, sector by sector, is whether an alternative exists. Demand that explodes sweeps nothing away: it feeds a derogation case. Electronics and semiconductors got a dedicated option back in August 2025, before the cooling argument ever showed up.

In this whole file, one number rests on actual samples. ChemSec sent finger-prick blood tests to the European executives on its list, recalling that PFAS have been detected in the blood of more than 99% of people. Nobody takes samples at the factory gate.