It’s 2050. And you’re on your way to a cement plant somewhere in sub-Saharan Africa. Thirty years of rapid urbanization and economic development has changed this part of the world almost beyond recognition. The construction industry has boomed and, with it, the need for building materials. But unlike the urban and industrial revolutions experienced elsewhere, the concrete that underpins life here is made not with Portland cement, but calcined clay.
Or perhaps you are in Chile, where the cement plants now process the region’s massive deposits of mine tailings – over a century’s worth – into enhanced cementitious materials.
Even when you visit plants that most resemble the cement plants of yesteryear, new technologies have made their mark. Electrochemical and acid leaching processes are much more likely to be used for breaking down limestone than old-fashioned preheater towers. And then there’s carbon capture, which has finally reached maturity. Although not nearly as ubiquitous as some might have expected back in the early years of the century – when it was often touted as a panacea for all of the world’s climate woes – it has nonetheless found its niche.
Wherever you are in the world however, all cement plants have one thing in common: they no longer emit CO₂.
A strange new world
If you read the roadmaps to a zero-carbon cement industry published by various industry organisations, the vision outlined above may come as a surprise: for the most part, these roadmaps portray an industry continuing in much the same way – just with more alternative fuels, more supplementary cementitious materials, and carbon capture thrown in. But for Thomas Petithuguenin, Head of Research and Partnerships for Cement at FLSmidth, the future is a lot more exciting.
“I see these roadmaps as an invitation to see things differently,” explained Thomas.
“We have these traditional visions, but they leave a significant chunk of emissions unaccounted for. In a sense, they highlight the uncertainty and therefore give permission for us to be imaginative in our solutions.”
Talk with Thomas and, before long, this passion for creative, radical thinking becomes obvious. “There is no reason why cement should continue to be produced as it is today – and as it has been for almost two centuries – via the calcination of limestone. There is a huge range of cementitious materials out there: some are available today; others we know will be available in the future. Crucially, however, there are many that don’t result in the same large-scale release of CO₂ that results from the production of clinker.”
According to Thomas, this should be the starting point of any discussion about the cement plant of the future. It’s a vision summed up in a simple question: what if the calcination of limestone for the production of cement can be avoided altogether? It may be a surprising thing to hear from the man in charge of innovation at one of the world’s leading cement equipment suppliers – a company that made its name by building just the sort of plants that would be obsolete in his vision of the future. But it’s the question that drives Thomas.
“Let’s look at what has happened in the energy sector in recent decades,” Thomas continued. “It used to be large-scale power plants, producing gigawatts of electricity, ramping up and down to meet grid demand. But slowly the picture has changed. The focus is now on decentralised energy production, cleanly generated using local resources and responsive to local needs. This transition is not only making the power sector greener; it is also enabling communities to be more independent and resilient.”
A similar transition could also happen in the building material sector. Instead of large-scale cement plants located near to limestone resources and using a globally-standardised process, “what you could see happening is the development of decentralised, even mobile, production sites that use the raw materials available in the local area,” Thomas explained. “That could be mine tailings, clay, waste materials from various industrial processes, even old concrete.”
It’s a trend that is already creeping into the building materials sector: for example, with concrete recycling, where a small-scale facility is built on the periphery of a municipality to process local concrete waste into secondary aggregates for use in local construction projects.
But what about the plants of today?
A key question and challenge to Thomas’s scenario is what happens to the existing fleet of traditional cement plants, particularly newer ones that still have decades of operational life. At these plants, clinker production may continue but it could only do so in a much cleaner way: which means dealing with the process emissions.
“If we imagine a cement plant that’s still making clinker, as it’s doing today, then we would have to conceive of different processes: for example, calcination via an electrochemical reaction, which could eliminate the combustion emissions. Much of the equipment at the cement plant would remain the same in this case; only the preheater and calciner would be exchanged for an electrochemical reactor. You would still need to extract and prepare the raw meal – so you would still need crushers and conveyors – and you would likely need a kiln to produce the final clinker.”
Another option could be to recarbonate the CO₂ onto the calcium oxide (CaO), but in such a way as to produce a reactive calcium carbonate (CaCO₃); a process that is already in use in the US. “Whether or not all cement plants could be converted to this process, in a way that is commercially viable, is yet to be seen,” noted Thomas. “But it’s definitely a potential vision for the future of cement production.”
“Another idea that has been floating around is to extract calcium oxide out of the limestone via acid leaching,” continued Thomas, after initially warning that continuing with a centralised production model was “not optimum.” Acid leaching has the advantage of being flexible in terms of feedstock: “the process can be applied to waste concrete or mine tailings and you can make a good-quality supplementary cementitious material from it, although handling acid is not necessarily an ideal option”.
It is only at this point in the discussion that Thomas broaches the technology that is so often mentioned when discussing decarbonising – well pretty much any industry: carbon capture. Here, he makes the case for oxyfuel, which involves firing the kiln with a pure oxygen atmosphere to produce a concentrated CO₂ stream at the stack. Cryogenic capture technology is then used to remove the CO₂ as a liquid, an ideal form for geological sequestration and remineralisation.
“It makes the cement plant much more expensive to operate, which is why it’s not top of my list,” admits Thomas. “But it may be easiest to implement as it allows cement companies to continue to operate existing assets with only relatively minor adjustments to the process and equipment, without changing the product output. Of course, it also raises the issue of how to dispose of the captured CO₂. In my view and for the most part, this would have to be done underground, as we will simply produce too much of it to sequester any other way.”
This latter point brings the conversation to electrification, which in Thomas’s opinion makes more sense when applied to alternative processes than the traditional clinker production line. “I think it’s a much better fit for the production of alternative cementitious materials, such as activated clay. If you electrify the clay activation process, you basically eliminate the CO₂ emissions, as there is no CO₂ released from the material (unlike limestone). It’s also a much cleaner, quieter, and more controllable process with the potential of getting the needed energy directly from renewable power generation skipping any steps needed for power to fuel conversion. All this together leads to a process nicely fitted for the future with tight regulations on all pollutants and a high cost of CO₂ emissions coupled with flexible power consumption”
So, what’s slowing us down?
Up to this point, the conversation has kept to the technologies that we may see in the cement industry of 2050. But as Thomas now pointed out, the major roadblock to realising the vision of a zero-carbon cement industry is not technological. Nor is it building standards and regulations, another typical scapegoat when talking about progress (or lack thereof) in the industry.
According to Thomas, the challenge is both more structural – and more human. “What slows down the shift toward new technologies and new ways of building is the lack of vertical integration in the sector. Each link in the chain – from the quarry through to the smallest subcontractor on the building site – is striving to be profitable. Each has their own vision of what the future looks like. But they are visions that are not necessarily compatible.”
“I see when I work on projects that involve a range of partners, each with a slightly different vision, each trying to remain relevant, each with their own customer base to appease,” continued Thomas. “If anything is slowing down progress, it is this.”
A driver change
Despite this, Thomas is optimistic about the future – and FLSmidth’s place in it – although he also acknowledges the uphill struggle ahead. “My sincere hope is that FLSmidth will be a driver for this transition. But to decarbonise by 2050, cement producers are going to have to make decisions in the next few years about the route they are going to take to get there. That means technology suppliers like us need to be ready with the solutions now.”
Thomas also foresees a changing role for the venerable Danish company, away from making machines (although there will remain a need for much of the company’s portfolio of products, even in 2050) to become more of a facilitator of change.
“Today, we are primarily a company that develops technology and supplies equipment. In 2050, we may still do some of that, but I believe our role may be much more about offering our process knowledge and engineering expertise as a service, and then pulling in relevant partners to implement solutions. It’s a catalytic role. One that will change the culture of the company. But one that could make a real difference to how the industry advances.”
What then is the overall message from Thomas? The cement industry of 2050 is, first and foremost, zero emission. It is also much less reliant on large-scale, centralised production facilities; it is local, using locally-available materials and responsive to local needs.
“It’s going to be a patchwork quilt of different processes, all determined by what’s available nearby,” concluded the FLSmidth innovation chief. “This may sound daunting – maybe even a little fantastical – but it should also be liberating. We have a lot of clever people working in the industry: it’s time to let them get creative and see what sort of future we can build together.”
This article was first published in Global Cement, January 2022.