Cement
The kiln-made glue of concrete, produced at nearly 4 billion tonnes a year and a major source of industrial CO2.
Construction · No. 78
- Not on a critical list
The world bakes nearly 4 billion tonnes of cement a year, and China alone makes almost half of it.
Chart: Illustration: Cement
Where it comes from
Chart: Map of where it comes from
Limestone and clay are quarried beside the plant and roasted in a rotary kiln that must never stop turning, releasing CO2 and forming clinker.
Three things to know
- China made about 1.7 billion t of cement in 2025, roughly 45% of the world total, with India next at 470 million t.
- World cement and clinker exports were worth only about $9.9 billion in 2024, because cement is heavy and mostly used locally.
- Each tonne carries about 0.63 t CO2e, and curing concrete reabsorbs only about 17% of the CO2 released by calcining.
The journey
- 1 QuarryLimestone or chalk with clay or shale
- 2 Raw mealCrushed and ground into fine powder
- 3 Rotary kilnLimestone gives up CO2, forms clinker
- 4 Finish grindingClinker milled with gypsum, slag or ash
- 5 ConcreteReady-mix, blocks and mortar