A concrete future: KHD’s CTO Matthias Mersmann delivers CUSCIT’25 keynote

Key takeaways:

• Current decarbonization efforts fall drastically short of Paris Agreement targets, mainly due to insecurity in decision-making driven by uncertain carbon costs, production values, and bureaucracy.
• KHD’s Cement Beyond Carbon strategy delivers proven technologies, including flash calcination for diverse clay types, Pyrorotor® alternative fuel systems, and advanced process control—with carbon capture as the path to complete decarbonization after 2030.
• Cement has a future, but it needs to be decarbonized. We have to act now to achieve this.

 

At the CUSCIT’25 Cement Olympics conference in Turkey, Matthias Mersmann, Chief Technology Officer of KHD Humboldt Wedag International AG, delivered the keynote address, outlining the urgent need to decarbonize the cement and concrete industry.

 

The Scale of the Challenge: Building the Future

Mersmann opened his presentation with words from UN Secretary-General Antonio Guterres: three-quarters of the infrastructure of 2050 still needs to be built. This oft-repeated statement is sometimes expressed as the need to build “the equivalent of another New York City every day.” But what do these figures actually mean in concrete terms?

 

According to recent research published in the journal Nature, the world had installed about 550 gigatonnes of concrete by 2020. Taking Guterres’s position would require an additional 1,650 gigatonnes of concrete over the next 25 years. This translates to an annual production requirement of 65 gigatonnes of concrete per year—more than double current production levels.

 

Mersmann acknowledged the uncertainties inherent in such projections, noting that the UN’s assumptions are based on societal development trajectories that may not fully materialize. However, he emphasized that high demand for concrete infrastructure is virtually guaranteed. Climate change alone will drive massive concrete consumption, as coastal cities around the world—Istanbul, Sydney, Amsterdam, Kuala Lumpur, Jakarta, and Mumbai among them—will require extensive protection against rising sea levels through seawalls, dikes, and other defensive infrastructure.

 

Industry Projections and the Clinker Conundrum

The Global Cement and Concrete Association (GCCA), which represents about 80% of worldwide cement production, has made its own estimates of the industry’s future. The GCCA projects a 143% increase in concrete growth by 2050 under current practices. This concrete growth must be decoupled from clinker consumption to meet decarbonization goals. This can be partly achieved through strategies such as binder optimization (-14%) and the use of alternative binders (-5%). However, reducing the clinker-to-cement ratio from 0.62 to 0.52 using other cementitious materials will play the most prominent role.

 

Traditionally, the industry has relied on fly ash from coal power plants and slag from steel production. As the power and steel industries transform and decarbonize, the availability of these materials will decline dramatically. According to Mersmann, only one material is available in sufficient quantities worldwide to fill this gap: calcined clay, which can replace up to 50% of clinker in cement without compromising strength.

 

The Urgency of Action: Falling Short of Paris Agreement Targets

Despite the clear technological pathways available, Mersmann stressed that current industry activities fall far short of what is necessary to achieve the Paris Agreement targets and reach net-zero carbon emissions by 2050. The presentation highlighted two particularly sobering reports:

 

• The European Environmental Agency recently published findings showing that decarbonization activities across Europe are proceeding much too slowly to meet Paris Agreement requirements.
• Even more striking, the German Advisory Council on the Environment (SRU) calculated that Germany’s available CO₂ budget—the amount the country can still emit while remaining consistent with Paris Agreement goals—will be exhausted by 2033. That’s only eight years away, after which Germany would need to be completely carbon neutral to stay on track.

 

While cement production in Germany accounts for only 2% of the country’s carbon emissions, this shortfall illustrates that heavy industries across the board are far behind their necessary decarbonization trajectories. Mersmann identified several reasons for this procrastination:

 

• Overbearing bureaucracy.
• Uncertainties in financing.
• Uncertainties about future carbon costs.
• Lack of clarity around the EU’s Carbon Border Adjustment Mechanism (CBAM).

 

These uncertainties make it extremely difficult for cement producers to calculate future carbon costs and justify the necessary investments in decarbonization technologies.

 

The Paris Agreement: Will It Hold?

Given these challenges, Mersmann posed a critical question: Will the international community stick to the Paris Agreement, or will countries begin to abandon it? He expressed skepticism that countries would withdraw, noting that, for most signatories, the commitments are now deeply embedded in national policies and international obligations. This leads to an unavoidable conclusion: decarbonization must happen, whether or not individual companies or countries believe they can afford the necessary investments.

 

At KHD, the conviction that there is a future for cement, but that this future must be decarbonized, has been encapsulated in the strategic vision: Cement Beyond Carbon.

 

Cement Beyond Carbon: A Two-Phase Decarbonization Strategy

KHD’s Cement Beyond Carbon initiative represents both a statement of possibility—that the cement industry can be decarbonized—and a roadmap for achieving it. Mersmann outlined the two-phase approach of the Cement Beyond Carbon vision.

 

The first phase focuses on drastically reducing emissions through proven and emerging technologies. The biggest lever, aligned with GCCA estimates, is to dramatically reduce clinker content in cement by increasing the use of calcined clay, while also reducing fossil fuel consumption through alternative fuels, optimizing plant operations, and implementing efficient advanced control systems.

 

Flash Calcination Technology

An oft-cited challenge to increasing calcined clay production is finding suitable clay deposits. Many search exclusively for kaolinite because it’s considered the highest-quality clay and the easiest to calcine. However, KHD has developed a highly efficient flash calcination technology designed to process various types of clay, including illitic, montmorillonitic, and chloritic clays, into high-quality supplementary cementitious materials. The key to this technology lies in precisely adjusting two critical parameters—retention time and temperature—to each clay type.

 

In KHD’s flash calciner design, very finely ground clay powder is created in an impact mill and flows evenly through the flash calciner. This ensures controlled retention time and controlled temperature exposure. Unlike rotary kilns, where temperature exposure varies depending on where exactly in the kiln a particle travels, the flash calciner provides uniform conditions for all particles. This precision prevents both recrystallization (from excessive temperature exposure) and agglomeration (from excessive retention time), resulting in an optimal product with minimal carbon footprint.

Alternative Fuels: The Pyrorotor Technology

The cement industry has pursued the substitution of fossil fuels with alternative fuels for decades, and KHD has longstanding experience in this area. The company has developed solutions enabling fossil fuel substitution rates ranging from 10% to 99%.

 

A centerpiece of KHD’s alternative fuel technology is the Pyrorotor rotating gasification reactor capable of substituting up to 95% of fossil fuels. The Pyrorotor can handle fuels that are hard to burn, require longer retention times, and have a high moisture content, all without the need for expensive pre-processing. This makes it economically viable to use low-grade waste and biomass fuels.

 

The technology has been proven in practice, with 15 installations operating worldwide. Client feedback has been excellent, with operators successfully using low-cost, minimally processed alternative fuels to fire their cement kilns.

 

Plant Optimization and Energy Efficiency

Another crucial lever for reducing emissions is optimizing the entire plant for maximum energy efficiency. KHD has been a pioneer in this approach since its inception, continuously developing technologies to increase process efficiency. The latest key innovation is the KHD ProMax® RTO, an advanced control system that optimizes cement and clinker production in real-time. This software system combines artificial intelligence with experienced-based human intelligence. It utilizes multiple neural networks that are trained online on actual plant operations, augmented by human expert knowledge, to achieve permanent self-learning and optimized production operations.

 

Operator Training: Simulex® VR

The educational level of plant operators significantly impacts a plant’s carbon emissions. Well-trained operators can identify and resolve inefficiencies that automated systems might miss. To address this, KHD developed the Simulex training simulator. The German Cement Manufacturers Association (VDZ) has used Simulex simulators for its certified training programs for many years, establishing it as a tried-and-true solution.

 

Simulex covers the entire clinker and cement production process, from raw materials to finished product silos. The simulation incorporates a complete distributed control system interface with all signals and alarms, just like a real control room. Critically, Simulex operates in real-time, allowing trainees to learn how problems develop gradually and how to intervene effectively.

 

KHD has recently enhanced Simulex with three-dimensional virtual reality capabilities. Trainees can now walk through the plant in virtual reality, identify problem locations, solve issues hands-on, and return to the control room to restore optimal operations. At the CUSCIT conference, KHD hosted a Simulator Challenge, where participants tackled operational problems with the fastest, most effective operators receiving certificates.

 

Phase Two: Carbon Capture (After 2030)

Even with maximum efficiency improvements and alternative materials, some CO₂ emissions from cement production are unavoidable—specifically, the emissions from the chemical decarbonization of limestone. To achieve true carbon neutrality, these remaining emissions must be captured.

 

Mersmann acknowledged that many in the industry consider carbon capture too expensive today. However, he argued that when the industry reaches the point where further emission reductions are impossible, carbon capture will become mandatory for achieving carbon neutrality—”there is no way around it,” Mersmann said.

 

Various carbon capture technologies are currently available or under development. Mersmann emphasized that KHD’s core competency lies in engineering cement plants that optimally incorporate these capture technologies with the highest possible process efficiency, regardless of which specific capture technology ultimately proves most practical and economical.

 

A Call to Action

Mersmann closed his presentation with a direct appeal to the cement industry: “Let’s believe cement has a future, but it needs to be decarbonized. It’s on us, and we have to act now.” This statement encapsulates KHD’s position: cement and concrete remain indispensable materials for building the infrastructure and buildings that societies need. There is no prosperous future without concrete. However, the types of concrete and cement must change. The industry must decarbonize, and the window for action is rapidly closing.

 

The Cement Beyond Carbon vision represents KHD’s commitment to empowering the industry’s decarbonization journey through comprehensive technological solutions—from calcined clay processing and alternative fuels to advanced process control and, ultimately, carbon capture. With 197 countries committed to the Paris Agreement and the physical reality of climate change becoming increasingly undeniable, the question is no longer whether the cement industry will decarbonize, but how quickly it can deploy the necessary technologies at scale.

 

KHD’s message is clear: the technologies exist, the pathway is defined, and the time to act is now. The journey to carbon-neutral cement production has begun, and KHD is positioning itself as a key technology partner for cement producers worldwide as they navigate this essential transformation.