From Portland to Paris: Time to detox and build a more sustainable cement and concrete industry

By Joren Verschaeve

By Sabela González

The billions of tonnes of cement made each year account for a staggering 8% of global CO2 emissions – more than the combined emissions of aviation, trucking, and shipping! Given that the global demand for cement will continue to rise, there is no alternative: we need to act. It is essential to rapidly decarbonise the production of cement. This will only be possible if we detox from our addiction to the so-called Portland clinkers, the key ingredient and emitter of cement. This will not be an easy task as outdated cement and concrete standards, drafted by incumbent industry, force construction companies to use those cement and concrete types, which contain excessive levels of these Portland clinkers.  

Alternative solutions are available. But putting them to work requires the removal of a series of barriers. These are predominantly linked to policies, laws and standards. The question is if and how we can move towards low carbon and circular construction: are policy makers and industry finally ready to move beyond Portland clinkers? Will they work to bring product standards in line with the Paris Agreement? 

Clinker – the big grey emitter  

Cement production processes generate almost a tonne of CO2 for every tonne of cement produced. Zooming in, clinker is the main culprit of all these emissions. The production of clinkers through heating limestone releases CO2 directly (up to 60%), while the energy for fueling the kilns indirectly accounts for the remaining emissions (up to 40%).  

Clinkers are marble-sized grey balls which constitute the key ingredient of cement. They are produced through a chemical process called calcination. This involves heating up crushed rocks and other raw materials – typically limestone – in kilns at a staggering temperature of up to 1450°C. This initiates a chemical reaction in which the material is split into CO2 and calcium oxides. These oxides form clinkers, and once cooled, grinded, and mixed with other ingredients, they turn into ready-to-use cement.  

The most common type of cement is called Portland cement, representing 99% of the market. Its success can be attributed to its widespread availability at low cost, despite its high carbon intensity compared to other raw materials. Portland cement, however, uses limestone as its main ingredient in the making of clinkers – and the planet simply cannot afford to continue business as usual.  

Thinking beyond Portland clinkers  

Even though the cement industry is typically portrayed as a hard-to-abate sector, new technologies exist, and they could allow for much faster decarbonisation, if supported by all supply chain actors. 

Innovation lies at the heart of industrial production processes, with various industries having fundamentally changed the way in which they produce goods over time. Yet, cement production has changed very little since the time it was first patented 200 years ago in the UK. What is more, big cement producers seem to be rather unwilling to change their production process, often heavily betting on fuel switching or Carbon Capture, Usage and Storage (CCUS) in their decarbonisation plans. This approach is not aligned with the once-in-a-generation opportunity to accelerate the transition to a net-zero future and make low-carbon cement and concrete the norm within the next decade. 

Let’s be clear: ordinary Portland cement is far from irreplaceable – potential decarbonisation pathways exist. Detoxing from Portland cement should be at the very top of the priority list. A rapidly growing number of studies – including from the United Nations Environmental Program and the International Energy Agency– show that clinker substitution is one of the most promising levers for decarbonising the cement industry – it can rapidly bring down both direct and indirect emissions. It is common sense to first reduce the use of clinkers to the greatest extent possible, and only then look into alternative solutions such as CCUS, which also have a role to play.  

In fact, this is already beginning to happen, with a growing number of start- and scale-ups developing and placing alternative low-carbon cement on the market. This is by using a plethora of innovations, ranging from the use of microbes as alternative binders to blending small fractions of clinkers with other materials with binding properties.  

The detox starts with better stardards 

Standardisation plays a key role in greening the construction sector, as new and more sustainable standards can open the door to many more cement types and alternative binders in the near future. 

Unfortunately, low-carbon cement types today make up a tiny fraction (less than 1%!) of the global cement market. Until now, the existing standard offering technical specifications on cement composition clearly favoured outdated polluting cements over the already existing lower-carbon alternatives, which should be used more.  

Such standards are set by industry in so-called standardisation bodies, and, in theory, are intended to promote innovation as well as regulate safety and environmental concerns. Sadly, things rarely work as intended, as industry standards prefer the high emitting status quo cement types, effectively blocking the uptake of low-carbon alternatives. This is particularly relevant in the construction sector, where standards are closely linked to building codes. As a result, actors within the construction sector are obliged – be it for legal and/or liability reasons – to stick to those products that comply with the relevant standards. 

Even in those cases where alternative products might potentially be used, only a handful of big construction companies have the resources and expertise to look into these innovative products and self-insure when using them. All of this to manage potential liability issues in case damage occurs, something which is not necessary when products are covered by existing standards. 

Such cases remain an exception, not the rule, with only a few encouraging examples available. For instance, in two years’ time, the Olympic village in Paris will make environmental history: the housing accomodation is, at least partially, being made of ultra low-carbon concrete. Another example that proves that a greener construction sector is possible is the UK’s High Speed 2 railway line, whose goal is to construct the most sustainable high-speed railway in the world using a new low-carbon concrete product which emits roughly 42% less CO2 compared to standard concrete.  

A recipe for success?  

Sadly, most cement and concrete standards follow a recipe-based approach, meaning that they oblige producers to have fixed amounts of Portland clinkers blended in their different cement and concrete mixes. That means every major road, bridge and building project is legally obliged to use one of the most polluting substances on the planet. It is as if we forced every home to burn coal for heating or pushed red meat onto every plate. 

This situation is unacceptable in the light of today’s climate emergency. The cement industry must finally embrace performance-based standards, which define the final properties of a product, without locking in specific cement composition.  

Portland to Paris – now! 

We believe that in order to meet Europe’s 2050 climate goals, we should target the greatest possible uptake of alternative low carbon cement and concrete solutions. How can this be achieved?  

By transforming the sector through environmentally ambitious standards and policies. There is a clear intention from decision-makers, such as in the EU, to become the global standard setter for the transformation of energy-intensive industries for a carbon neutral world and economy, including the high-impact cement and concrete sector. But this transformation will not happen, unless we tackle traditional cements.    

Time to end, once and for all, our addiction to Portland clinkers, and finally set course for a Paris-compliant cement and concrete industry.