Dr. Dirk Schmitt, Head of Department Cement der HeidelbergCement AG, über C²inCO₂

Calcium Carbonation for industrial use of CO₂

CO₂-WIN Connect: Mr. Dr. Schmitt, the project goal of C²inCO₂ is to produce building materials with CO₂. What exactly does that mean and how did you come up with the idea?

Dr. Schmitt: The basic idea is to exploit the carbonation reaction to which concretes are naturally exposed during their life cycle. Doing so, CO₂ can be firmly reintegrated as calcium carbonate in recycled concrete components. The hardened cement paste, which is a central component of concrete along with sand and gravel, plays a decisive role. The calcium present in this "RCP" (Recycled Concrete Paste) can bind CO₂ again. The basic prerequisite for this, however, is a proper separation of these concrete components in order to have the RCP as quantitatively and purely as possible as well as in powder form with a high surface area. Under these conditions, calcium and CO₂ can again form a stable, permanent bond. This "carbonated" cRCP can then be reused as a cement constituent.

CO₂-WIN Connect: How did you go about finding suitable project partners? What expertise is needed to achieve the goals of the project?

Dr. Schmitt: As a leading global building materials manufacturer, HeidelbergCement maintains an extensive network with industrial partners as well as with research institutes and universities with a wide range of technical orientations and competences. For C²inCO₂, the two main challenges are in the area of material separation, i.e. the phase-pure separation of concrete constituents with a focus on RCP, and in the area of carbonation of RCP and its use as a main cement constituent, including the resulting binder properties. Here, we cooperate with the leading German technology companies in these areas, as well as with universities and research institutions.

CO₂-WIN Connect: What exactly is the innovation?

Dr. Schmitt: The main task and innovation are on the one hand, the development of a process technology for the quantitative separation of the recycled concrete constituents with a focus on RCP as well as the development of a related process technology for the carbonation of this material. In addition, the properties of cements produced with this material, and ultimately of the resulting concretes, are largely uncharted territory.

CO₂-WIN Connect: What role can the process play in the cement industry in the future? Which contribution will C²inCO₂ make to concepts such as the circular economy and low carbon economy by 2030?

Dr. Schmitt: The approach of targeted processing of recycled concrete components, the re-carbonatisation and the reuse in building materials will be of great importance in the future, especially against the background of the increasing scarcity of traditional cementitious materials such as granulated blast furnace slag and fly ash. Due to its high potential to bind CO₂ in a stable way, RCP plays a special role within the low carbon economy and Roadmap 2030. The quantities of recycled concrete and their content of CO₂-absorbing RCP to be expected in Germany alone would represent a significant CO₂ sink and close CO₂ cycles.

CO₂-WIN Connect: Do you foresee any external influences that could hinder or promote successful market penetration?

Dr. Schmitt: One challenge is certainly the very conservative attitude towards new technologies of the construction industry, especially in Germany. This requires a rethinking of "established" processes and production procedures. Cements with cRCP and concretes produced with it require adjustments in processing, e.g. about fresh concrete properties or in curing. Furthermore, the integration of these new binders into existing or new standards at national or European level is a challenge, especially in terms of time. The novel technologies for separation and carbonation naturally also require high investments in the German plant locations, accompanied by rising costs for such novel, resource and environmentally friendly products.

Increasing environmental awareness in Germany may also lead to market acceptance over time, coupled with the willingness of companies to accept the high investment costs through higher product prices, which is already the case in other European pioneer countries such as the Netherlands or Scandinavia. Crucial for a successful implementation of the technology is the rapid creation of necessary framework conditions. Market conditions must be politically adapted to redirect existing material flows and enable sustainable access to concrete demolition. Among other things, this means avoiding "downcycling" of the material or even final disposal in landfills. For example, approx. 80-90% of the construction and demolition waste generated in Germany is recycled, but this happens almost exclusively as so-called "downcycling". Demolition material is only used as low-value material in road construction, earthworks or for backfilling. The construction waste thus returns to the material cycle predominantly in an inferior function. However, the goal should be high-quality recycling on as large a scale as possible. Therefore, a commitment to careful deconstruction is indispensable.

In addition, public authorities can contribute to updating and harmonising outdated regulations and standards. Existing regulations neglect the technical development of the past decades and do not take into account advances in e.g. processing technology or concrete admixture technology. Furthermore, as the largest contracting authority in the construction industry, it could promote the use of recycled raw materials in tenders in the sense of the Closed Substance Cycle Waste Management Act. In order to ensure constant market demand and competitiveness, incentives for the use of recycled building materials should be created for customers. Last but not least, CO₂ capture and utilization must be scaled up and made competitive through the creation of CO₂ transport infrastructures and incentive systems..

CO₂-WIN Connect: What is your version of the cement industry in a Carbon Net Zero world?

Dr. Schmitt: In our industry, we want to be pioneers on the path to CO₂ neutrality. As an energy-intensive company, we want to make our contribution to the declared goal of the Paris Climate Agreement to keep the global temperature increase significantly below 2 °C.

We are convinced that concrete has the potential to become the most sustainable and versatile building product throughout its entire life cycle, from production to recycling. A significant part of our investments and research activities in the coming years will be directed towards achieving this goal.

We already have a significant track record in reducing CO₂ emissions and are steadily intensifying our efforts. We have brought forward our 2030 target of 30% to 2025. For 2030, we have set a new, ambitious target of less than 500 kg of CO₂ per tonne of cementitious material, or a further 19% reduction compared to 2019 - all underpinned by a clear action plan (Factsheet CO₂-strategy HeidelbergCement). By 2020, we have already achieved a 23% reduction in our specific net CO₂ emissions per tonne of cementitious material compared with 1990.

Our CO₂ reduction strategy for the next ten years is based on concrete measures at plant and product level, the implementation of which is already in full swing. To further reinforce the targets, the company is consistently anchoring its CO₂ reduction targets in the global compensation systems. Our most important emission reduction measures for the next ten years are:

- Increased use of alternative raw materials and fuels

- Substitution of CO₂-intensive clinker in cement by cementitious materials with a significantly lower CO₂ balance

- Extensive investments in plant efficiency and CO₂ reduction at plant level

- Increasing the proportion of sustainable and low-CO₂ concrete products

In order to achieve our long-term goal of offering CO2-neutral concrete across our entire product portfolio by 2050 at the latest, we are focusing on CO₂ utilisation and recycling management in addition to the above-mentioned measures - primarily on the increased use of alternative fuels and alternative cement-like secondary materials (incl. recycled materials) as well as the capture and utilisation or temporary storage of CO₂ (Carbon Capture & Usage/Storage, CCU/S for short).

By investing in various carbon capture technologies, we aim to capture CO₂ in its purest form to either recycle it or store it safely until it can be used in large quantities.

Cement and concrete companies can also support the circular economy through resource efficiency, co-processing of waste materials and concrete recycling, including its technical carbonation. We are investigating a variety of minerals with regard to their absorption potential of CO₂ and the possibility of producing marketable building materials from them. These include natural minerals, but also industrial waste products such as granulated blast furnace slag or cement fines from recycled concrete. The C²inCO₂ project is a cornerstone for this important measure.

CO₂-WIN Connect: Dr. Schmitt, thank you very much for the interview.

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