Conserving resources, closing cycles: Process engineering for industrial recycling

Material-specific recycling processes

Not every process is suitable for all material flows. Depending on the material, operators must choose specific processes in order to further process their materials to a high standard.

Paper and fiber recycling: Secondary fibers instead of fresh wood

In paper recycling, shredded waste paper is broken down in water in a pulper. Screening and cleaning stages remove coarse materials, impurities, and fine particles. In deinking processes, printing inks are separated by flotation or washing, producing bright secondary fibers.

These fibers replace fresh pulp, saving wood, energy, and chemicals. For paper and cardboard producers as well as the packaging and printing industry, this is a key contribution to resource efficiency and climate protection—especially for corrugated cardboard, cardboard packaging, and graphic papers.

Glass and laminated glass: recycling for containers and flat glass

Glass recycling begins with crushing the glass into cullet, followed by the removal of impurities such as metals, ceramics, or organic residues. In the case of laminated glass, for example from vehicles or buildings, films and coatings must also be separated. Color sorting ensures that cullet can be returned to glass production with a precise fit.

This allows container glass and flat glass to be produced with a high proportion of recycled glass, which significantly reduces the energy required for the melting process. This is important for industries such as the construction and window industries, automobile manufacturers, and beverage and food producers that use glass packaging.

Metal recycling: high-quality scrap as a raw material

Metals can be recycled almost indefinitely, as long as the quality of the scrap is right. After shredding, magnetic separators separate ferromagnetic components, while eddy current separators separate non-ferrous metals such as aluminum. Further processing steps such as sorting, briquetting, or paint removal prepare the scrap optimally for melting processes in steel mills and foundries.

There, tinplate packaging and aluminum scrap replace primary ores and bauxite, for example. This saves energy and reduces the carbon footprint of metal production. Steel mills, foundries, the automotive industry, and mechanical engineering, which use large volumes of metal, benefit particularly from this.

Closing cycles for water and process media

In addition to solids, water and media cycles also have a major impact on the resource efficiency of recycling plants. Processes such as flotation, sedimentation, filtration, membrane processes, and biological purification stages treat process water so that it can be recycled and reused multiple times.

In the paper industry, for example, fine particles, fillers, and dissolved substances are separated from white water, significantly reducing the demand for fresh water. In the chemical, food, and beverage industries, too, it is worth taking a look at water and media cycles—not only for environmental reasons, but also for cost reasons.

Conclusion: Recycling as a process engineering challenge and opportunity

For industrial operators, recycling is a complex interplay of mechanical, thermal, physical, and chemical processes. The challenges are complex: heterogeneous input materials, fluctuating qualities, high quality requirements for recyclates, economic pressure. However, with the right combination of shredding, sorting, cleaning, particle technology, and material-specific processes, these challenges can be overcome.

Investing in suitable process technology and process know-how secures access to secondary raw materials, reduces dependence on primary materials, and meets growing regulatory requirements. Above all, however, recycling thus becomes an integral part of sustainable, resource-efficient production.