Start with the awkward chemistry, because it explains everything that follows.
Cement is made by heating limestone in a kiln. Doing that releases carbon dioxide from two separate sources. The first is the fuel burned to reach roughly 1,450 degrees Celsius, and that one is solvable in the ordinary way, with cleaner fuel or electrification.
The second is not. Limestone is calcium carbonate, and when you heat it, it gives up its carbon as a matter of chemistry. That carbon comes out of the rock, not out of the fire. No amount of renewable electricity touches it, and it accounts for the majority of the emissions. Cement is around 8 percent of global carbon dioxide, and this is why it has stayed there.
Here is what happened
A purpose-built kiln line started running on pure oxygen. The catch4climate research facility at SCHWENK's Mergelstetten plant in Baden-Wurttemberg was officially inaugurated on 8 July 2026. It is a dedicated line producing 450 tonnes of clinker per day, and it is the first cement facility built around the Pure Oxyfuel process.
Four competitors paid for it themselves. The operator, CI4C, was founded by Buzzi with Dyckerhoff, Heidelberg Materials, SCHWENK and Vicat. The cost was over 120 million euro, with no public funding. Rival cement makers do not co-fund research plants casually.
It has already made cement. First clinker came at the end of May, first oxygen supply in mid-June, and an initial operating campaign was completed before the inauguration.
The process was designed by thyssenkrupp Polysius. This is not a bolt-on retrofit. The kiln itself was redesigned around burning in oxygen instead of air.
And it is not the first cement plant to capture carbon. That distinction belongs to Heidelberg Materials' Brevik plant in Norway, which opened in June 2025 as the world's first industrial-scale cement carbon capture facility, capturing roughly 400,000 tonnes a year. Heidelberg is a shareholder in both.
How it works
The usual approach captures carbon after the fact. Post-combustion capture burns fuel in ordinary air, then treats the exhaust. Brevik does this, using an amine solvent that grabs carbon dioxide out of the flue gas and then releases it when heated.
The problem is that air is mostly nitrogen. Roughly four fifths of it. Burn in air and your exhaust is overwhelmingly nitrogen with carbon dioxide diluted through it. You have deliberately mixed the thing you want with a large volume of something you do not, and then you have to unmix it. That separation is where the energy and the cost go.
Oxyfuel removes the nitrogen at the start. Feed the kiln pure oxygen instead of air, and there is no nitrogen entering the process. What comes out is a stream of mostly carbon dioxide and water vapour. Condense the water and you have concentrated carbon dioxide without ever having separated anything.
You stop separating and start purifying. That is the whole idea in one sentence, and it is why the process is interesting rather than merely another capture plant.
The trade is that oxygen is not free. You need an air separation unit to produce it, and that consumes significant electricity. You have moved the energy penalty rather than eliminated it. Whether oxyfuel wins depends entirely on whether making oxygen costs less energy than scrubbing carbon dioxide out of diluted exhaust.
Why it matters
Cement is one of the few sectors with no substitute and no electrification path. You cannot renewable-energy your way out of chemistry. For a handful of heavy industries, process change is the only lever there is.
Concentrated carbon dioxide is a product, diluted carbon dioxide is a problem. This is the turn the headline promises. A pure stream can be sold into industrial uses or converted into fuels and materials, because the buyer does not have to pay to clean it up first. Post-combustion capture produces carbon dioxide that has already cost a fortune to isolate.
It contrasts sharply with pulling carbon out of the sky. Direct air capture works on air that is roughly 0.04 percent carbon dioxide, which is thermodynamically brutal. We covered why in the machines sucking carbon out of the sky. Capturing at the kiln, before dilution, is the easier physics by an enormous margin.
The funding structure is itself a signal. When four competing manufacturers spend their own money on a shared research plant with no subsidy, they are hedging against regulation they expect to arrive.
The honest catch
This is a research plant that has run briefly, and the claims around it need care.
No capture-rate data has been published. The figure of around 95 percent that appears in trade coverage is a design target, not a measured result. Test campaigns are described as upcoming.
It is research scale. 450 tonnes of clinker a day is a fraction of a commercial line. Brevik, at industrial scale, is a different order of operation.
The first claim is narrower than it sounds. First Pure Oxyfuel cement facility, not first cement plant to capture carbon. Getting that wrong is the easiest way to lose credibility on this story.
There is no transport or storage chain attached. Capturing carbon dioxide is one problem. Moving it and permanently storing or using it is another, and this plant does not solve it.
The energy penalty is unpublished. Nobody has stated what the air separation unit costs in electricity for this facility, which is the number that decides whether the whole approach is cheaper.
EDITOR'S TAKE
There is exactly one number that decides whether oxyfuel is a better idea than scrubbing, and it has not been published: how much electricity the air separation unit consumes per tonne of clinker. Everything else in this story is architecture, and the architecture is genuinely elegant. Do not mix a gas you will later have to unmix. But elegance has lost to arithmetic many times in industrial chemistry, and until somebody states the energy penalty, the honest position is that this is a promising process with an unfilled blank in the middle of it. Watch for the first test campaign results, and watch whether any of the four owners commits to a full-scale oxyfuel line rather than quietly building another amine retrofit.
Quick questions
Why does making cement release carbon dioxide even with clean energy?
Because the carbon comes out of the rock, not just the fire. Cement production heats limestone, which is calcium carbonate, until it decomposes into calcium oxide and carbon dioxide. That reaction is the point of the process: you need the calcium oxide to make clinker, which becomes cement. The carbon dioxide is an unavoidable by-product of the chemistry itself, and it accounts for well over half of a cement plant's emissions. Even a kiln heated entirely by renewable electricity would still release it. This is why cement, along with a small number of other heavy industries, cannot be decarbonised by cleaning up the power supply alone.
Is oxyfuel actually better than normal carbon capture?
On architecture, clearly. On economics, unproven. Conventional capture creates a dilution problem and then spends energy solving it, whereas oxyfuel avoids creating the problem. But making pure oxygen requires an air separation unit, which is itself energy intensive, so the comparison comes down to which energy penalty is smaller across a full plant. That number has not been published for this facility. There is a second advantage worth noting: oxyfuel exhaust is concentrated enough that the carbon dioxide may be usable as an industrial input rather than something to be buried, which changes the economics from pure cost to possible revenue.
Is this the first cement plant to capture its carbon?
No, and the distinction matters. Heidelberg Materials' Brevik plant in Norway began operating in June 2025 as the world's first industrial-scale carbon capture facility in the cement industry, capturing around 400,000 tonnes a year using post-combustion amine capture, with the captured carbon dioxide fed into Norway's storage infrastructure. The German facility's claim is narrower and technology-specific: the first cement plant built around the Pure Oxyfuel process, at research scale. Heidelberg is involved in both, which is a useful reminder that the industry is running several approaches in parallel rather than backing one.
Sources
catch4climate / CI4C: the 8 July 2026 inauguration release, with plant capacity, timeline and investment figures.
Heidelberg Materials: shareholder statement on the Mergelstetten oxyfuel facility.
thyssenkrupp Polysius: the process and plant design behind the Pure Oxyfuel line.
Heidelberg Materials Brevik CCS: the world's first industrial-scale cement carbon capture plant, operating since June 2025.
Frontier Signal explains frontier technology in plain English. Company and consortium figures should be independently verified. This is general information, not investment advice.
