Michel Gimenez is a Chemical Engineer with a Doctorate in Physical Chemistry. His career has covered both the chemical and cement industries, and has been split roughly equally between operations and R&D/industrial transfer. At LafargeHolcim, his main focus is CO2 mitigation, sustainability and industrial innovation. He is currently involved in numerous projects and partnerships, primarily in the areas of CO2 capture and use and sustainable development as well as in technological & product innovation.
© iStock/Alexander Kosev
Worldwide anthropogenic emissions of CO2 are estimated at 37 Gt in 2013. The cement industry accounts for 2 to 2.5 Gt CO2/year i.e. between 5.5 % - 6.5 % of total emissions. Our industry represents an important share of greenhouse gas emissions worldwide and the consumption of cement and concrete is going to increase in the coming years due to both economic development and growth in the global population. It is therefore very important that our industry develops new products and new technologies in order to mitigate its CO2 emissions. LafargeHolcim has been leading or participating in several projects on this subject over the last nine years, in an attempt to find ways to reduce its CO2 footprint.
The Cement Industry
Portland clinker is produced through a combustion process: first calcium carbonate from the quarry is calcined to lime; then this lime is combined with clay to produce clinker. This process requires thermal energy, e.g. 2.9 GJ/tclinker with the best available technology (BAT). The CO2 emission related to both calcination and combustion is ~ 830 kg CO2/t clinker produced.
Unlike combustion industries, only 1/3 of the CO2 emitted by the cement industry comes from combustion, while 2/3 come from the limestone calcination. Limestone calcination (i.e. CO2 removal) is highly endothermic and occurs at 850°C in the precalciner of the cement plant while clinkerisation is slightly exothermal.
Producing 1 metric tonne of clinker emits 830 kg CO2, of which 540 kg come from the limestone calcination and 290 kg from the combustion itself. Once produced, the clinker is augmented by several “cementitious” materials so that the production of 1 metric tonne of Portland cement in our company finally emits around 600 kg of CO2.
The usual performance levers applied in our cement plants are well managed. In particular, these are saving programs that deal with both kWh of electricity and thermal energies. In addition, our product mix has also evolved towards more complex products using cementitious product additions as clinker extenders. Today, 1.35 tonnes of cement is produced from 1 tonne of clinker compared to 1.1 tonnes only 30 years ago. All these levers have led to considerable progress over the last 30 years: a reduction of about 30% in CO2 emissions in 1990-2014.
Nevertheless, although the performance levers are still very efficient, we have developed a new approach in designing low-CO2 products able to substitute Portland cement. AETHER Cement™, a new binder allowing a 30% reduction in CO2 emissions (www.AETHER-Cement.eu) and SOLIDIA Cement,™ may make it possible to reduce CO2 emissions by up to 70% as compared to ordinary Portland cement.
SOLIDIA Cement™ and Concrete
This new product is a complete breakthrough for Portland cement and concrete. Although its mineralogical and chemical composition differs from Portland (less limestone), it sets and hardens through a carbonation process and not through hydration. This means that the CO2 emissions related to the burning process of this new product are reduced by 30%, and it captures additional CO2 during the curing process i.e. ~ 250 kg CO2/t binder. Altogether, the emissions per tonne of binder will be reduced by at least a factor of 2, i.e. to under ~ 400 kg CO2 instead of 840 kgCO2/t for Portland clinker (for some applications a CO2 reduction of up to 70% is possible).
© Solidia Concrete™ pavers and stones
This cement develops as much strength in 24 hours as Portland cement in 28 days and can already address several market segments such as precast (pavements, blocks, railroad crosses, road sleepers…) and some structural and concrete ready mix applications. LafargeHolcim is currently developing this new product with the North American start up SOLIDIA®, the inventor of the product.
It is too early today to make a precise forecast on the overall CO2 reductions linked to SOLIDIA® which is related to its market development. However, we can say that this product combines direct CO2 reduction during the production process with CO2 recapture during material setting and it inscribes fully into the circular economy and industrial ecology concepts. In addition, it combines mineral carbonation (dealing with CO2 uses) and production of a useful product for the construction business.
The industrial feasibility of this product was demonstrated through two production campaigns: 5000 tonnes of SOLIDIA® clinker at a North American plant in April 2014 and 3000 tonnes in Hungary in June 2015.
We expect this lever can contribute to significantly reducing the cement industry’s CO2 emissions. However, although emitted in a huge quantity worldwide, the CO2 market is quite small today and we could paradoxically encounter supply shortages for mass mineral carbonation applications.
The capture of CO2 from diluted flue gas is still expensive when compared to the cement market price and the current supply shows over quality for emerging applications in construction materials. Indeed, the liquid CO2 price is today ≥ 100 EUR/t, whereas the cement market price in Europe and North America ranges from 50 to 100 EUR/t. It may additionally be subject to high shipping costs. Therefore, local access to cheap CO2 supply will determine the future of CO2 utilisation to produce new low-CO2 binders and, to a certain extent, the future of most of the other carbon dioxide technologies also.
In summary, we think that this type of product is a good example of a CO2 application adapted to our industry. We do produce and sell mineral products and we know how to market them, and are able to develop them for numerous application segments. The CO2 capture through mineral carbonation is therefore tailor made for our core business.
Altogether, the global impact of our industry is reduced through incremental levers linked to performance management of our industrial sites, but also through breakthroughs in developing innovative products, i.e. new cements and concretes. The development of a holistic approach with new solutions embedded into the construction industry is equally important.