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Cement has two problems. Neither can be engineered away.

One is carbon, and it comes from chemistry rather than fuel. The other is heat, and it comes from the material itself.

Problem one — carbon

Almost as much carbon leaves the plant as product does.

900 g
of CO₂ released for every kilogram of cement produced. A 90% emission rate by weight.
2nd
largest carbon-emitting industry on earth, at around 9% of all global emissions.

Where it comes from

A cleaner furnace does not fix it.

Roughly two thirds of cement's emissions come out of the rock, not the flame. That happens whatever the kiln burns.

Making cement Quarrylimestone Kiln, 1,450°Ccalcination Grind clinkerheavy electricity Cement 900 g CO₂ per kg Making Gau Plaster Collectdung, raw limestone Dry and millambient temperature Dry blendfixed formulation Gau Plaster No kiln. No CO₂.

Calcination is the step that releases the carbon. It is also the only step we do not have.

Problem two — heat

Then the wall lets the heat straight in.

People are comfortable between 20 and 25°C. Every material we build with is a good conductor, and we install no insulation at all.

Soaks up all day
The wall absorbs sun through the afternoon.
Gives it back at night
Releasing it inward exactly when you are trying to sleep.
So you buy a machine
And pay its electricity bill every month for fifty years.

Thermal conductivity, W/m·K

Lower is better for a wall.

Reinforced concrete1.70
Burnt clay brick0.81
Cement plaster0.72
Gypsum plaster0.38
Gau Plaster0.25

Mild steel sits at about 45 on this scale. Typical published values for natural materials vary with density and moisture, so treat these as orders of magnitude.

And a third thing

Ordinary Portland cement is being priced out of the market it built.

Nobody has banned it. What is happening is slower and more serious: the carbon in a tonne of cement is becoming a line on the invoice.

EU Emissions Trading System
Producers already pay for the CO₂ they release
The EU carbon price sat at roughly €75 per tonne of CO₂e in early 2026.
Carbon border adjustment, from 2026
Imported cement now pays that price at the border too
The benchmark is 0.83 tonnes of CO₂e per tonne of Portland cement — the highest process emissions of any sector covered. Around €62 a tonne at early-2026 prices.
The clinker factor
Pure OPC is the worst-placed product in the category
CEM I is 95–100% clinker and sits at the top of the emissions range. Slag cement runs at 5–64% and can come in as low as 0.40 t. European standards have been driving the clinker factor down for years.
What it means here
The direction of travel reaches India too
Green building certification, procurement preferences and export exposure all point the same way. A material whose value depends on roasting limestone is on the wrong side of every policy trend in construction.

Sources: EU CBAM benchmarks under Regulation (EU) 2023/956; EU ETS carbon price, Q1 2026; clinker ranges per EN 197-1. Stated as pricing pressure rather than a ban, because that is what it is.

The alternative

Skip the kiln and all three problems go away at once.

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