The better the coordination of shredding, sorting, cleaning, particle technology, and material-specific process steps in recycling, the higher the yield, quality, and cost-effectiveness. POWTECH TECHNOPHARM also recognizes the growing importance of recycling for industry: in the Recycling-in-Focus pavilion, visitors can experience how innovations in mechanical engineering are shaping the future of recycling. If you don't want to wait until the next POWTECH TECHNOPHARM, the following overview provides an overview of key technologies that can transform linear economies into a true circular economy.
- 03/09/2026
- Article
- Circular economy & recycling
Conserving resources, closing cycles: Process engineering for industrial recycling
Raw materials are becoming more expensive, supply chains more vulnerable, and regulatory requirements for circular economy and CO2 reduction more stringent. This presents companies in the manufacturing industry with a strategic question: How can they design their own material flows in such a way that waste becomes a valuable secondary raw material instead of causing costs and risks? The answer lies in process engineering: It determines which material flows end up as lost residues and which can be recycled.
Written by Marius Schaub
Basic mechanical operations: From mixture to defined material flow
In general terms, virtually all process engineering methods can be summarized in four processes: separating or combining, heating or cooling. This also applies to the various recycling processes.
Grinding as initial digestion
Many recycling processes begin with shredding. Shredders, cutting mills, or hammer mills reduce the particle size of bulk materials, films, and loose materials to a defined size. The aim is to break down heterogeneous input materials so that they are suitable for subsequent steps such as sorting, washing, or melting processes.
A typical example is plastic recycling: defective batches, sprues, and unused packaging (PIR = post-industrial recyclates) are processed into regrind, which can be recompounded and extruded as recyclate. This reduces the need for virgin material and lowers the carbon footprint. This step is particularly relevant for plastics processing, the packaging industry, and producers of consumer goods, which generate large amounts of plastic waste.
Sorting and separating: Quality through selectivity
However, shredding alone is not enough: it is crucial to separate the waste into fractions that are as pure as possible. This is where screening machines, air separators, magnetic and eddy current separators, or optical and NIR-based sorting systems (NIR = near-infrared) come into play. They separate material according to grain size, density, magnetic properties, or spectral characteristics.
In packaging recycling, for example, mixed streams of household waste (PCR = post-consumer recyclates) are separated into plastic, paper, glass, and metal fractions. The more selective this sorting process is, the higher the quality of the secondary raw materials that can be used later, for example in new packaging or technical applications. Operators of sorting plants, the food and beverage industry, and manufacturers of branded goods benefit directly from these quality gains.
Washing and wet processing: Cleanliness as a lever for quality
Contaminants are one of the main reasons why recycled materials are not used in higher-quality applications. Drum and friction washers, friction scrubbers, and float-sink tanks remove adhesions such as labels, fillings, organic residues, or dust. At the same time, density separation separates floating fractions from sinking fractions.
A classic application is film and hard plastics from the packaging industry, such as food or household packaging. Consistent wet processing allows the resulting recycled materials to be used in significantly higher-quality applications, such as non-food packaging or technical components. For plastics recyclers, the food, household, and cosmetics industries, this step is a key lever for resource efficiency.
Particle technology: From waste material to marketable product
The smaller the residual materials are, the more challenging it is to recycle them. Modern process technology offers possibilities for recycling small particles and even dust.
Agglomeration and granulation: making fine dust usable
Many recycling processes produce fine powders or dusts that are difficult to transport, dose, or handle safely. Agglomeration and granulation processes combine these fine particles into larger, mechanically stable granules or pellets, for example in mixers, drum or disc granulators, often with a binding agent and controlled moisture content.
One example is zinc-containing steel mill dust: instead of being landfilled, it is pelletized and then used in blast furnaces or rotary kilns. This allows metallic recyclables to be recovered and primary raw materials to be replaced. Significant users are steel mills, non-ferrous metallurgy, chemical, and building materials industries that want to transfer their by-products into internalized cycles.
Fluidized bed technology: drying, agglomerating, coating
Fluidized bed systems suspend particles in an air stream, creating an intense flow around each individual particle surface. This enables highly efficient drying, cooling, agglomeration, or coating. For powdered secondary raw materials in particular, this opens up product-related options that go beyond simple waste management.
Dusty secondary raw materials from chemical or pharmaceutical processes can be processed into free-flowing, low-dust granulates that can be safely dosed and further processed. In this way, production residues are turned into marketable products. The technology is particularly interesting for chemical and pharmaceutical companies, food manufacturers, and other powder-processing businesses.
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.
Mechanical plastic recycling: from regrind to regranulate
After sorting and washing, plastics are plasticized, filtered, and processed into regranulate using extruders. Melt filters remove any remaining solid particles, while degassing reduces volatile components. The better the pre-cleaning and purity of the materials, the closer the recycled materials come to the properties of virgin materials.
Polyolefin packaging made of PP or PE can thus be recycled into new bottles, canisters, films, or technical molded parts. For plastics processors, packaging manufacturers, and distributors, this is the key to increasing the recycled content in their products and meeting regulatory requirements without compromising properties.
Thermal and chemical processes as a supplement
“Thermal recycling” is often considered a euphemism, as it ultimately involves burning material flows. However, the process does generate energy. How chemical recycling will develop in the future remains to be seen.
Thermal recycling: When material recycling ends
Not every material stream can be recycled in a meaningful way in terms of materials or raw materials. Heavily contaminated, heterogeneous, or pollutant-containing fractions are often used for energy, for example in waste-to-energy plants or cement kilns. The energy they contain replaces fossil fuels such as coal or gas, and some of the mineral residues can be used in clinker or road construction.
Such processes are part of a holistic recycling strategy, particularly for the cement industry, energy suppliers, and waste management. The incineration of residual waste is also often seen as a pollutant sink that removes substances harmful to the environment or health from the cycle.
Chemical plastic recycling: Raw material recovery from problematic waste streams
Multi-layer composite films, heavily filled plastics, and material mixes push mechanical recycling to its limits. Chemical processes such as depolymerization, pyrolysis, and hydrothermal processes aim to break down polymers into monomers, oils, or gases. These products can then serve as feedstock for the chemical or petrochemical industry—just like primary fossil products.
This means that plastic waste is used as a material at a different stage of the value chain and can be returned to high-quality applications. For the chemical industry, refineries, and plastics manufacturers, this opens up new sources of raw materials – provided that the processes are or become technically and economically manageable.
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.
Author
Marius Schaub