Olli Hänninen, Owner and Co-founder, Moviator Oy, discusses the future of decarbonising cement through smart material utilisation.
Over the decades, the cement sector has advanced from scale to sophistication, and now it faces its most profound transformation yet — decarbonisation of one of the world’s most carbon-intensive industries.
The theme — The 3Cs: Cut, Cement, Carbon — captures a new mindset. Cutting emissions is no longer just about compliance; it is central to competitiveness. Cement, once seen as a fixed formula, is being reimagined through technology and circularity. And carbon itself, traditionally treated as waste, is emerging as a potential input. Together, these three Cs define not only a challenge but also a remarkable opportunity.
Cement’s dual carbon burden
Cement production carries a double carbon burden — from both the energy required to heat kilns and the chemical release of CO2 from limestone during clinker production. Even with modern efficiency improvements, the underlying chemistry of the process remains inherently carbon-intensive.
Traditional ‘Cut’ measures — improving thermal efficiency, using alternative fuels, or lowering the clinker factor — are vital, but not sufficient on their own. The next step lies in rethinking the materials themselves: how we process them, how we use them, and how we can capture and store carbon directly within them.
Slag: From by-product to resource
Among industrial by-products, steelmaking slag stands out as one of the most underused materials in the journey to decarbonisation. Produced at roughly 200 kg per tonne of steel, it is often stockpiled or landfilled, despite containing valuable calcium- and magnesium-bearing compounds.
Blast-furnace slag from ironmaking is already widely used in blended cements, but steel slags from basic oxygen or electric arc furnaces remain challenging. They are heterogeneous, often solidifying into massive rock-like blocks known as steel skulls, or into finer, inconsistent fractions. These forms are difficult to process and integrate reliably into cement production.
Yet this complexity conceals opportunity. Slag is abundant, stable, and — with the right processing — capable of replacing a large share of clinker while storing CO2 within its structure.
Unlocking the hidden value in slag
At Moviator Oy, we focus on two critical and often overlooked fractions of steelmaking slag that have historically been difficult to process — but which hold immense untapped potential for decarbonising cement and improving circularity in steel production.
1. Large solidified steel skulls
These massive, irregular formations solidify at the bottom of ladles or converters and have traditionally been cut apart using oxygen lances — a slow, energy-intensive, and hazardous process. Moviator has developed an innovative process that enables the efficient treatment of solidified steel skulls, eliminating the need for conventional thermal cutting and improving material recovery.
Once treated, the recovered metallic portions are returned to the steelmaking cycle, while the mineral component is directed for cementitious applications. This dual recovery approach maximises resource efficiency, reduces waste, and lowers both carbon and energy footprints across the steel and cement value chains.
2. The sub-50 mm fine fraction
At the other end of the size spectrum, finer slag particles can be further refined through advanced grinding techniques, achieving reactivity levels well above standard cement benchmarks. This transformation enhances the slag’s ability to act as an effective supplementary cementitious material (SCM), capable of replacing a substantial portion of the clinker in blended cements.
Together, these two complementary approaches — recovery and recycling of steel skulls and activation of fine slag through precision grinding — enable Moviator to transform slag from an inert by-product into a high-performance, low-carbon cement material, while simultaneously closing the loop within the steel industry.
This material transformation is only the first step. The next challenge — and opportunity — lies in what we do with carbon itself.
Beyond storage: Turning CO2 into stone
Most global attention focuses on carbon capture and storage (CCS) — compressing CO2 and injecting it underground. While CCS has value, it raises questions of permanence, cost, and long-term monitoring.
Moviator takes a different path: carbon utilisation through mineral carbonation. In simple terms, captured CO2 reacts with calcium- and magnesium-rich compounds in slag to form stable carbonates, effectively turning gaseous emissions into solid minerals within a controlled process environment.
This approach achieves two outcomes:
1. Permanent carbon binding: CO2 is locked into a solid matrix with no risk of re-release.
2. Improved material properties: Carbonated slag is more stable and can exhibit enhanced early strength and durability.
This is more than a laboratory concept. Pilot-scale work has already demonstrated that 4–5 tonnes of slag can permanently store around one tonne of CO2, confirming that industrial by-products can become long-term carbon sinks within a circular cement economy.
A realistic path to a circular, carbon-negative loop
Our vision is a circular, carbon-negative cement ecosystem — one that absorbs more CO2 than it emits. In this system, industrial waste becomes both raw material and carbon storage medium, creating a closed loop between the steel, cement, and carbon management sectors.
This concept builds on real trends already taking shape:
- Cement plants near steelworks using slag as feedstock.
- Pilot carbonation systems integrating captured CO2 from industrial exhausts.
- Early life-cycle assessments showing that mineralised slag can achieve net CO2 reductions of 70–90 % compared to conventional clinker.
However, realising a fully circular model will require more than technology. It will demand:
- Clean energy for grinding and carbonation to ensure net carbon benefits.
- Proximity and logistics between steel, cement and CO2 sources.
- Updated standards and policies that recognise mineral carbonation as a verified form of carbon removal.
Currently, most climate frameworks credit geological storage but not yet mineralised products. Changing that will take collaboration between innovators, regulators, and investors. Still, the direction is clear: CO2 mineralisation is emerging as a credible, permanent carbon sink with industrial-scale potential.
Practical optimism: Balancing vision and reality
The idea of a carbon-negative cement industry is ambitious — and it should be. Cement contributes roughly 7-8 per cent of global CO2 emissions, so any solution must be bold. But ambition must come with realism.
Scaling up slag carbonation will take time. Reactors must handle large volumes efficiently, and the economics depend on CO2 availability, energy costs, and policy incentives. Yet progress is rapid: several European plants are already demonstrating carbonated aggregates and binder materials commercially.
Moviator’s strategy reflects this practical optimism — combining proven engineering principles with forward-looking applications. Each tonne of refined, carbonated slag replaces high-emission clinker and locks away CO2 permanently, turning waste into value step by step.
The mindset shift: The 3Cs reimagined
The 3Cs — Cut, Cement, Carbon — are not separate goals but interconnected levers of transformation:
- Cut emissions by improving efficiency and material circularity.
- Cement innovation by replacing clinker with reactive industrial by-products.
- Carbon redefined as a useful input, not just a waste stream.
To truly decarbonise, the industry must embrace both radical innovation and practical integration. Every action that converts waste to raw material and emissions to mineral stability brings us closer to a sustainable cement future.
From incremental to transformative
Decarbonising cement will not happen overnight. It will take imagination, cross-sector collaboration and new standards that reward permanent carbon binding. But the tools are already here — from smarter slag processing to direct CO2 mineralisation.
Moviator’s work in refining steel skulls and utilising slag demonstrates that circular, low-carbon materials are not science fiction. They are emerging now, one pilot and partnership at a time.
The 3Cs mindset is ultimately about shifting perception — from seeing materials as static commodities to viewing them as active agents in the carbon cycle. Through this lens, cement production can evolve from a major emitter to a permanent carbon sink, helping build not only the world’s infrastructure but also its climate resilience.
ABOUT THE AUTHOR:
Olli Hänninen, Owner and Co-founder, Moviator Oy, helps industries maximise material recovery with advanced slag processing technology.