CO2Cycle: Resource-saving use of CO2 for the production of calcium carbonate

The construction sector has a significant impact on society's consumption of resources and is a major source of greenhouse gas emissions. One of the main reasons for this is the energy-intensive conversion of raw materials into high-quality building materials such as cement. Carbon dioxide emissions are unavoidable during these processes. In addition, large quantities of construction waste are produced during renovation and demolition. New processes are therefore urgently needed to improve the CO₂ balance and resource efficiency in the construction sector. The "CO₂Cycle" project aims to use calcium from mineral waste to convert CO₂ from CO₂-containing process gases into easily transportable and versatile calcium carbonate (CaCO₃ or Recycled-Precipitated Calcium Carbonate). The CO₂Cycle approach combines the topics of CO₂ capture, material CO₂ utilization and upcycling of construction waste.

Extraction technology for slag transferred to construction waste

The main aim of the project is to develop and validate a process for recycling CO₂ for the production of R-PCC. CO₂ from wood-fired power plants, municipal solid waste incinerators and biogas production plants will be used for this purpose. The most widely used technology is gas scrubbing for the separation of CO₂ from gas streams. The resulting product, R-PCC, is a valuable raw material used primarily in the paper, plastics and paint industries.

The project aims to transfer the already patented Ca extraction technology from slag (see NuKos) to construction waste, to further develop the recycling methods for the process solutions such as acetic acid and amine and to analyze the energy efficiency of the entire process. Concrete waste is a valuable source of calcium and its use as a raw material helps to conserve resources. The optimized recycling process for the reagents acetic acid and amine is also of central importance, as efficient recycling can close material cycles and this in turn maximizes the efficiency of the process.

The application of the "CO₂Cycle" technology offers considerable ecological and economic advantages. On the one hand, the use of CO₂ from exhaust gases for the production of R-PCC achieves long-term CO₂ storage, as the carbon remains bound in the R-PCC for decades. This reduces CO₂ emissions and supports the goals of the European Green Deal. Secondly, the recycling of construction waste as a source of calcium reduces material consumption. The high efficiency of the process enables other by-products such as sand and gravel to be recycled in addition to R-PCC.

At the same time, the use of R-PCC reduces the costs for the procurement and processing of primary raw materials. The process also reduces disposal costs for construction waste that would otherwise end up in landfill sites. The use of recycled PCC can also lead to cost savings in the paper, plastics and paint industries, where there is a need for high-quality fillers. The process helps companies to improve their CO₂ balance.