Cement, Steel & the Hard-to-Abate Build: The Emissions of Infrastructure Itself
The smith could choose a different fire, and did, and his iron was the better for it. The lime-burner had no such choice: the stone gave up its breath in the burning, as it had since the world was made, and no change of fuel could persuade it otherwise. They were called by the same trade, and they were not in the same trade at all.
The Materials Everything Else Is Made Of
Every asset in this section — the reactors, the transmission towers, the data centres, the pipes beneath the street — is built from concrete and steel. That makes these two materials the substrate of the entire infrastructure decade, and it makes their emissions a peculiar kind of problem: the more infrastructure the world builds to decarbonise, the more of these materials it consumes.
The scale is substantial. Steel production alone accounts for roughly 7 to 9% of global CO₂ emissions, with cement contributing a similar order of magnitude. Together they sit near a seventh of the global total — not as a by-product of energy use that a cleaner grid will eventually fix, but as an intrinsic feature of making the physical world.
They are almost always discussed jointly, under the banner of “hard-to-abate” industry. That grouping is understandable and analytically misleading, because the two sectors face problems with entirely different structures — and therefore entirely different investment characteristics, timelines and probabilities of success.
Two Opposite Problems Wearing One Label
The distinction comes down to where the carbon dioxide comes from, and it is worth stating precisely because everything else follows from it.
In steelmaking, the emissions arise from the energy and the reductant. Coal does two jobs in a blast furnace: it provides heat, and it chemically strips oxygen from iron ore. Both jobs can, in principle, be done by something else — hydrogen as the reductant, electricity as the heat. The chemistry permits a substitute.
In cement, roughly 60% of emissions come from the calcination reaction itself — heating limestone drives off carbon dioxide as a matter of chemistry, converting calcium carbonate to calcium oxide. That CO₂ is released regardless of what fires the kiln. A cement plant running entirely on renewable electricity would still emit the majority of its carbon. There is no substitute reaction, because the reaction is the product.
Steel has a capital problem with a known technical answer. Cement has a chemistry problem with no complete one.
Steel can be decarbonised by changing the production route — the technology exists and is being built — but doing so means replacing the plant, which is a discrete, enormous, all-or-nothing capital decision. Cement cannot be fully decarbonised by any known route, because the majority of its emissions are the chemical reaction that makes the product. But cement plants can be improved incrementally, in small increments, at modest capital cost. One sector faces a large cheque and a clear answer; the other faces small cheques and no complete answer. Those are opposite investment propositions.
Steel: The Answer Exists and Costs 20–40% More
The technical pathway for steel is well established. Replace the blast furnace and basic oxygen furnace route with hydrogen-based direct reduced iron feeding an electric arc furnace: hydrogen strips the oxygen from the ore instead of coal, and renewable electricity melts the result. The emissions reduction is dramatic.
Real plants are being built on this basis — conversions and greenfield projects across Sweden, Germany, Spain and elsewhere are in construction or commissioning. The technology is not speculative.
The obstacle is cost. Hydrogen-based steel currently runs 20 to 40% more expensive than the conventional route at prevailing hydrogen prices, and the reason traces directly back to the previous piece in this thread: green hydrogen at $4–6 per kilogram cannot deliver competitive steel. The threshold usually cited for commercial viability is hydrogen below roughly €2 per kilogram. Analysts project cost parity somewhere in the 2035–2040 window on current trajectories — potentially 2033–2035 in jurisdictions with strong carbon pricing.
There is a second, cheaper route that deserves more attention than it gets: the scrap-fed electric arc furnace. It is deployable today, needs no hydrogen at all, and delivers 0.3–0.5 tCO₂ per tonne. Its constraint is scrap — availability, quality and traceability — not technology. In a world that has been accumulating steel in buildings and vehicles for a century, the recycled stream is a genuinely underrated asset, and the pre-processing and sorting technologies that improve scrap quality are a quieter investment theme than the hydrogen headlines.
Cement: Chipping Away at an Irreducible Core
Cement’s strategy is necessarily different. Since the calcination emissions cannot be eliminated by changing energy inputs, the sector attacks the problem from three directions at once — none of which is complete, and all of which are cumulative.
| Lever | What it does | Capital & verdict |
|---|---|---|
| Clinker substitution | Replace a share of clinker with supplementary materials — slag, fly ash, calcined clays. Blended cements reach roughly 0.40–0.65 tCO₂/t against ~0.83 for ordinary Portland. | Minor capex, fast, high impact. The single best return in the sector — constrained by supply and quality of substitute materials, not by technology. |
| Efficiency & alternative fuels | Modern kilns, waste heat recovery, efficient grinding, and substituting waste-derived fuels for coal. Addresses the ~40% combustion share. | Moderate capex, incremental. Reduces operating cost as well as emissions, which is why it happens without subsidy. |
| Carbon capture | The only route that addresses the calcination emissions themselves. Cement flue gas is relatively concentrated, which helps. | Large capex, unproven at scale. The only complete answer, and entirely dependent on capture economics and storage access. |
The strategic implication is that cement decarbonisation is a portfolio of partial measures rather than a single conversion. That makes it less capital-intensive per plant than steel’s route change, more incremental, and considerably less likely to reach zero. It also makes cement the anchor customer for carbon capture — and the reason the CCUS piece and this one are structurally linked: without capture, cement has a floor it cannot go below.
The Arithmetic Changed in January
Both sectors have spent a decade with the same problem: a cleaner product that costs more, sold into markets where buyers compete on price. Voluntary green premiums were never going to move commodity volumes. What changes that is policy — and on 1 January 2026 the European Union’s Carbon Border Adjustment Mechanism moved from a reporting exercise to a financial obligation.
Importers of steel, cement, aluminium, fertilisers, hydrogen and electricity into the EU now accumulate carbon costs on every shipment, settled through certificate purchases from February 2027. At an EU carbon price around €75 per tonne, ordinary Portland cement at roughly 0.83 tCO₂/t carries a gross cost near €62 per tonne of product. For steel, the spread between blast-furnace and low-carbon routes is far wider still, so the cost differential scales accordingly.
CBAM converts a green premium into cost avoidance — which is a different product entirely.
A premium is something a buyer pays voluntarily for a preference, and it evaporates under margin pressure. Cost avoidance is something a buyer pays to escape a charge they would otherwise incur, and it survives exactly as long as the charge does. That is the shift: low-carbon steel and cement stop being a sustainability purchase and become a hedge against a border levy. This is the purest form of policy manufacturing a cash flow anywhere in the Carbon thread — and it explains why capital decisions being made in 2026 are not optimising for 2026 costs at all, but positioning for 2030 and beyond.
Two qualifications keep this honest. First, the mechanism reduces rather than eliminates cost gaps: gas-based production in the Middle East and North Africa retains a meaningful cost advantage even after CBAM is applied — roughly 24% against 35% before it. Second, CBAM is a European instrument, and its incidence falls substantially on exporters elsewhere. That is a live fairness argument, and it is the subject of its own piece in the Global South thread.
Reading It Through the Frameworks
Where does policy become the cash flow? Directly and unusually explicitly. Absent a carbon price, low-carbon steel and cement are simply more expensive versions of commodities. With CBAM and the EU emissions trading system, the carbon intensity of a tonne of product becomes a line item in the buyer’s landed cost. The investment case for a conversion project is, quite literally, a forecast of the carbon price.
What kind of asset is this? Not infrastructure in the primer’s sense — these are industrial manufacturers with commodity price exposure, not toll-takers on a protected flow. The relevance to this section is as a supply chain: the cost and carbon intensity of steel and cement flows into every asset built downstream. A rising carbon cost on materials raises the capital cost of the entire build-out described in the Build thread.
Where is the moat? In three places. Scrap access and quality, which lets an electric arc furnace deliver low-carbon steel today with no hydrogen at all. Proximity to cheap hydrogen and clean power, which determines which conversions ever pencil. And supplementary cementitious material supply — slag and calcined clay are locally-sourced, and access to them is a genuine constraint on the cheapest decarbonisation lever in the cement industry.
Cement and steel are the materials the infrastructure decade is made of, and they are filed together under a label that hides the only fact that matters about them. Steel’s emissions come from its energy and its reductant, both of which have substitutes — so steel faces a large cheque and a known answer. Cement’s come mostly from the chemistry of the product itself — so cement faces small cheques and no complete answer.
That asymmetry should drive the analysis. In steel, watch the hydrogen price, the carbon price and the scrap stream, and note that the cheapest low-carbon route requires no new technology at all. In cement, watch clinker substitution first and carbon capture second, and accept a floor that will not go away. And in both, note what changed in January: a border levy turns a preference into a cost, and a cost is the only thing a commodity market has ever reliably responded to.
They asked the lime-burner why he did not simply do as the smith had done, and change his fire. He answered that he would gladly change it, and had; but that the stone did not burn for the heat’s sake, and would give up its breath in any fire that was hot enough — and that this was not a matter for craftsmen, but for the world as it was made.
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