The target of carbon capture and utilisation is to separate CO₂ from the flue gas to produce new valuable products. Various technologies which are capable of capturing CO₂ from cement flue gases have been developed in the past years. Now the industry needs to find applications with a high demand for the captured CO₂. 
 

Scaling up carbon capture technologies

With different types of integrated technologies (such as Oxyfuel, Indirect Calcination or Ca-Looping) and a broad spectrum of post-combustion solutions (for example amine technology), capture technologies can be adjusted to fit the respective site-specific conditions and requirements. Developing a site-specific CCUS strategy is complex, due to various factors like the availability of renewable energy having to be taken into account. Especially those cement plant locations offering no direct access to a CO₂ transport system may require a strategy which includes the utilisation of CO₂.
 

Production of e-fuels, chemicals and syngas

The conversion of CO₂ to several other molecules offers the greatest possibilities for circular value chains. The potential of synthetic fuels for those transport sectors, where e-mobility is limited (for example, sea transport and air traffic), is high. Basically, electrochemical or catalytic processes are not limited to one type of CO₂ product. Nevertheless, only a few projects and topics have been developed to TRL 6 or higher. The Fischer-Tropsch synthesis (FTS) for production of synthetic fuels offers a huge potential as it has been a well-proven technology for many years. In particular, the direct conversion of CO₂ to methane, methanol and longer hydrocarbons unlocks access to several follow-up fields of application. Sunfire’s breakthrough development in a Kopernikus project produces H₂ and CO from CO₂ and water in one Co-Electrolysis. This dramatically increases efficiency and decreases effort and costs. The produced Syngas (a mixture of H₂ and CO) is used by Ineratec technology (Fig. 1) in the FTS to produce a mixture of hydrocarbons which can then be hydrocracked to desired synthetic fuels.
 

Figure 1: Modular reactor system by Ineratec for syngas production © Sunfire GmbH

Polycarbonates and polyurethanes can be produced by CO and CO₂ from gases from metallurgical processes as proven by Carbon2Polymers, a sub-project of Carbon2Chem from the German steel industry. Since polymerisation reactions tend to be sensitive to impurities, the gas purification process has a special meaning in this context. With every new product application, such as mattresses made from Cardyon®, the circular economy comes closer one step at a time, offering new potentials for the cement industry as CO₂ customers. This utilisation path is gaining importance in the cement industry due to its high demand for CO₂. Various projects, such as Westküste100, Vicat’s Montalieu project, C2PAT or catch4climate are preparing the ground for commercial applications.
 

Direct use of CO₂

Among others, the ECCO2 joint venture plans to use the captured and treated CO₂ in a process known as carbon fertilisation in regional greenhouses. This process is known to improve crop productivity by enhancing natural photosynthesis. At commissioning, the project is planned to use 10% of the cement plants CO₂ emissions and will thereby fulfil an important milestone in 2023. Using the gas to feed microalgae which then can be fed to fish is the concept behind HeidelbergCement subsidiary Ciments du Maroc (Fig. 2).