Cement production and its decarbonization

Whether roads, bridges, residential buildings or skyscrapers – without cement, our cities as we know them would not exist. This is because cement is the binding agent that combines sand, gravel and water to create one of the most important building materials of our time: concrete. But the production of the gray powder has its downsides – the cement industry is responsible for around 7-8% of global CO2 emissions. We want to change that! As a pioneering technology partner, thyssenkrupp Polysius delivers innovative solutions to help cement producers decarbonize.

Cement production: an energy-intensive process

The decarbonization of cement production is nothing less than a revolutionary turning point in its millennia-old history. And this goes back further than you might think: as early as the 3rd century BC, the Romans developed opus caementitium, a building material for which lime was burned. Today, natural raw materials such as limestone, clay, sand and iron ore are ground into raw meal for cement production, heated and then fired in huge rotary kilns at around 1,450 degrees Celsius. This not only consumes an enormous amount of energy, but also releases CO2 – both through the burning of fossil fuels to generate the high temperatures and through the chemical reaction of limestone decomposition itself.

Calcination is one of the processes during cement production where there is great potential to reduce CO2 emissions with the help of innovative technologies from thyssenkrupp Polysius.

After the burning process, the components of the flour fuse together through the sintering process. The resulting cement clinker is then cooled to below 100 degrees Celsius and, with the addition of gypsum, ground into Portland cement – the most commonly used type of cement worldwide as the basis for concrete, mortar and stucco.

Decarbonization of the cement industry on several levels

CO2 emissions in cement production come from two main sources. Around 40% comes from the combustion of fossil fuels to heat the kilns, while 60% is released during the thermal decomposition of limestone into carbon dioxide and lime. In addition to the possibility of using alternative fuels, another option for reducing CO2 is to replace part of the clinker in the cement with supplementary cementitious materials (SCM) with a lower carbon footprint.

polysius® meca-clay for more climate-friendly cement production

The innovative polysius® meca-clay process from thyssenkrupp Polysius involves the production of activated clay as such a complementary cementitious material. The raw materials, all types of clay, are not activated by high temperatures but instead by a mechanical-chemical process, their 'inner energy' is 'charge', so to speak. The polysius® charger developed for this purpose requires only renewable electrical energy, which means that up to 70% of the thermal CO2 emissions from clay calcination can be avoided.

polysius® meca-clay technology uses renewable energy instead of fossil fuels to activate the clay for cement production.

polysius® pure oxyfuel: CO₂ capture through oxygen combustion

An even greater lever for avoiding CO2 is the polysius® pure oxyfuel process. The principle of the promising carbon capture technology (CCT) is to use pure oxygen instead of air in the clinker production combustion process in order to remove the nitrogen from the air and concentrate the CO₂ in the flue gas to over 90%. With a downstream purification system, the CO2 can be further concentrated to over 99.5%, which facilitates transportation and storage.

polysius® pure oxyfuel technology produces purer CO2 during cement production, which can be captured more easily and processed in other industries. This will make the production process climate-neutral in the future. In 2028, cement manufacturer Holcim will commission the world's first climate-neutral cement plant with polysius® pure oxyfuel technology.

Together on the path to decarbonizing cement production

Despite the great potential of sustainable cement technologies, there are still challenges that need to be overcome. As a supplier of innovative plants and equipment, thyssenkrupp is aware of both the challenges of the regulatory framework and the cost factor involved in implementing sustainable technologies. That is why we work in close partnership with our customers to make cement production more sustainable and digital, without losing sight of economic efficiency. The focus is on optimizing plant performance and availability and thus reducing total operating costs, in line with the polysius® guiding values of reliability and future orientation.

You can find more exciting insights into our research and technologies for decarbonizing cement production and other industries in our stories.