Chapter 07 · Materials & footprintsCircular Economy & Materials
Cement
Definition
A fine mineral powder, typically Portland cement produced by calcining limestone and clay into clinker and grinding it with gypsum, that hardens with water to bind sand and aggregate into concrete. Its production is among the most carbon-intensive industrial processes: the sector accounts for roughly 7–8% of global anthropogenic CO₂ emissions.
References
~7–8% of global anthropogenic CO₂; calcination as primary source; accounting methods (IPCC 2006, WRI-WBCSD).
Calcination ≈2/3 of process CO₂; cement = 27% of direct industrial CO₂; 2.2 GtCO₂/yr (2014); demand growth outlook.
Overview
What it means
Cement's carbon problem is structural: about two-thirds of process CO₂ comes from the chemical calcination of limestone (CaCO₃ → CaO + CO₂), which no fuel switch can eliminate, with the rest from kiln fuels. The IEA estimates cement accounts for ~27% of direct industrial CO₂, and demand keeps growing with urbanisation.
Decarbonisation pathways: clinker substitution with supplementary cementitious materials (SCMs — slag, fly ash, calcined clays), alternative fuels, kiln electrification, carbon capture on process emissions, and novel chemistries (e. g. LC3). Cement is therefore a flagship "hard-to-abate" sector in industrial-transition policy, embodied-carbon regulation and green public procurement.
How it is used
Producers report sector emissions under WBCSD/WRI cement protocols; LCAs quantify concrete's embodied carbon; green-procurement rules and building codes set clinker-factor and carbon limits; innovators market low-clinker and carbon-cured products.
Why it matters
Concrete is the most-used material on Earth after water; cement decarbonisation is a pacing constraint on net-zero construction and a test case for process-emission abatement.