Cement decarbonization: the levers that matter, from clinker factor to carbon capture

Cement is one of the hardest sectors to decarbonize, because most of its emissions come from chemistry rather than energy. Yet plants that understand their process in detail can cut emissions and cost at the same time. This guide sets out the main levers and how to prioritise them.

Where cement emissions come from

Cement production is responsible for a significant share of global carbon dioxide emissions, commonly estimated at around seven to eight percent. Most of those emissions come from making clinker, the main ingredient of cement.

Roughly 60 percent of clinker emissions are process emissions: when limestone (calcium carbonate) is heated in the kiln, it releases carbon dioxide as it turns into lime. No fuel switch can avoid this. The remaining emissions come mainly from burning fuel to reach kiln temperatures of around 1,450 degrees Celsius, with a smaller share from electricity used for grinding, fans and conveying.

That breakdown explains the strategy. To reduce emissions, a plant must use less clinker per tonne of cement, produce clinker more efficiently with lower-carbon fuels, use cleaner electricity, and eventually capture the process emissions that remain.

Lever 1: lower the clinker factor

The clinker factor is the share of clinker in cement. Replacing clinker with supplementary cementitious materials such as fly ash, ground granulated blast furnace slag, natural pozzolans, limestone and calcined clay reduces both process and fuel emissions per tonne of cement.

The limits are product standards, customer acceptance and local availability of materials. Blended cements and new formulations such as limestone calcined clay cement (LC3) can achieve substantial reductions while meeting performance requirements. Close quality control is essential, because strength and setting time must stay consistent.

Lever 2: alternative fuels

Replacing coal and petcoke with alternative fuels lowers combustion emissions. Options include refuse-derived fuel, biomass such as agricultural residues, used tyres and industrial waste. Biomass carbon is generally treated as biogenic, which further reduces reported fossil emissions.

Higher substitution rates require investment in storage, handling and feeding systems, and careful process control, because alternative fuels vary in calorific value, moisture and chlorine content. Plants that model the effect of fuel mix on kiln stability can push substitution rates further without upsetting production.

Lever 3: thermal and electrical efficiency

Modern dry-process kilns with multi-stage preheaters and precalciners are far more efficient than older designs. Even in modern plants, operating conditions make a big difference. Stable kiln operation, optimal excess air, good cooler performance and fewer stoppages all reduce specific thermal energy consumption.

On the electrical side, grinding is the largest consumer. Vertical roller mills, high-efficiency separators, variable speed drives and optimized mill operation reduce kilowatt-hours per tonne. Small percentage improvements across many hours of operation add up to large savings in energy cost and emissions.

Lever 4: waste heat recovery and renewable electricity

Waste heat recovery systems use hot gases from the preheater and cooler to generate electricity, often covering a meaningful share of a plant's own power needs. Combined with on-site solar or renewable power purchase agreements, they reduce Scope 2 emissions and exposure to grid electricity prices. In the Gulf and India, abundant solar resources make this lever especially attractive.

Lever 5: carbon capture

Because process emissions cannot be avoided through efficiency or fuel switching, deep decarbonization of cement will rely on carbon capture, utilisation and storage (CCUS). Several pilot and first commercial projects are under way worldwide. For most plants, CCUS is a longer-term lever, but planning for it now, including space, energy needs and potential storage or utilisation routes, keeps the option open.

Prioritising with data

The right sequence differs by plant. A practical approach is to:

1. Establish an accurate baseline of emissions per tonne of clinker and per tonne of cement, split by process, fuel and electricity.
2. Identify operating improvements that need little capital, such as kiln and mill optimization.
3. Evaluate clinker factor and fuel substitution options against quality and supply constraints.
4. Plan capital projects such as waste heat recovery and renewables.
5. Keep longer-term options such as CCUS on the roadmap.

The EU Carbon Border Adjustment Mechanism adds a commercial incentive for exporters of clinker and cement: lower verified embedded emissions mean lower costs for EU customers.

How NCV works with cement producers

NCV works with cement producers in the UAE, Saudi Arabia and India. Our consultants include cement process engineers who build decarbonization roadmaps grounded in how plants actually run. SustainOS connects to kiln and mill systems, tracks energy and emissions in real time, and its Twin & Optimize product recommends operating settings that reduce specific energy consumption. For one cement client, the roadmap identified a CO2 reduction potential estimated at 70,000 to 100,000 tonnes per year.