Decarbonisation Technology - February 2025 Issue

Construction and Demolition waste (CDW) comprises all waste produced by the construction and demolition of buildings and infrastructure as well as road planning and maintenance. CDW covers a variety of materials, including concrete and building rubble, and accounts for more than one-third of all waste generated in the EU. Following the introduction of the Waste Framework Directive in 2008, most countries in the EU have established practices for separation, recovery, and reuse of CDW waste, with the best achieving recycling rates of up to 90% ( European Commission, 2024 ).

discarded waste concrete rubble continues to be sent to landfill. Based in the Netherlands, C2CA (concrete to cement and aggregates) has developed an industrial-scale solution that transforms waste concrete into high-quality aggregates and sand, which are valuable raw materials for construction (see Figure 2 ). This circular approach facilitates concrete-to-concrete recycling, eliminating the need for virgin materials and reducing the amount of concrete rubble going to landfill as well as carbon emissions. The recycling process begins with density- based separation to remove contaminants and extract reusable aggregates. This is followed by a thermal separation stage to refine the materials further. Finally, advanced quality control and tracing technologies, such as laser- induced breakdown spectroscopy (LIBS) and radio frequency identification (RFID), are used to guarantee material consistency and traceability, ensuring it meets industry quality standards. By 2023, C2CA demonstrated its ability to scale this process, processing more than 1,000 tons of waste annually. The resulting materials, including coarse aggregates, fine aggregates, and ultra fines, are then used to produce new concrete, supporting a closed-loop system. This innovation not only reduces reliance on virgin resources but also provides a practical pathway to integrate circularity into the construction sector, significantly lowering its environmental impact. Circularity in the metals sector Steel is the most widely used metal, followed by aluminum. Both materials are readily recycled, with 90% steel and 37% aluminium reaching end-of-life now recycled in the EU. In their Net Zero Roadmap, the IEA requires the widespread

MacArthur Foundation, 2021 ) and up to 56% of the carbon reductions needed to achieve net zero in the EU ( McKinsey & Co, 2024 ). By reusing materials and minimising waste, circular systems reduce dependency on virgin resources and align with decarbonisation goals. They also create operational efficiencies and new opportunities for growth. Beyond recycling, circularity involves redesigning systems to eliminate waste entirely. Secondary raw materials can replace primary inputs, significantly lowering emissions. Negative emission technologies, such as nature-based solutions and carbon capture, further address emissions that cannot otherwise be avoided. Circular concrete Every year, the world produces 4.1 billion tonnes of cement, which accounts for 8% of global CO 2 emissions. At the same time, 3 billion tonnes of concrete waste is downcycled or discarded each year. Previously, no scalable or affordable technology existed to process waste concrete beyond downcycling, in which the material is downgraded or reused in lower-value applications like roadbeds. Globally, much of the

Figure 2 C2CA system for turning waste concrete into high-quality materials