Metal waste is valuable – if it is separated correctly. The following overview provides an insight into typical waste streams and shows what characterises each of them.
Metallic waste streams are among the most valuable fractions in recycling – at the same time, they place high demands on processing technology. Different grain sizes, varying material compositions and increasing quality requirements make precise and flexible sorting necessary.
Material flows vary considerably depending on their origin and composition. From coarse mixed fractions to metal-rich fine particles and complex composite materials, different requirements arise for separation technology and process control. Efficient processing therefore requires a precise understanding of the respective material flows and their physical properties.
The most typical metal waste streams
Aluminium
Aluminium is one of the most commonly recycled metals. This versatile non-ferrous metal is characterised by its low weight and high corrosion resistance.
Compared to primary aluminium production, recycling requires only a fraction of the energy – around 5 % – that would be needed to extract it from ore. Aluminium can be recycled multiple times with virtually no loss of quality. This requires sorting by type and processing according to alloy.
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Alloying elements such as magnesium or copper cannot be removed during remelting and, when different types are mixed, lead to downcycling, which degrades the material properties of the aluminium.
Precise sorting using eddy current, density and sensor sorting enables high-purity aluminium to be recovered.
Innovative sensor sorting systems with LIBS help to separate aluminium according to alloy.
Non-ferrous metal mixtures
Non-ferrous metal mixtures such as Zorba or Zurik, consist of metals that do not contain any significant amount of iron and are characterised by properties such as non-magnetism, good conductivity and corrosion resistance. The most common non-ferrous metals include aluminium (Al), copper (Cu), brass (Cu + Zn), bronze (Cu+Sn) and zinc (Zn) – materials that occur in almost every waste stream and are among the most valuable secondary raw materials.
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Global demand for non-ferrous metals has grown significantly, as recycling them requires considerably less energy than primary production and contributes to reducing CO₂ emissions.
Since non-ferrous metals are somewhat difficult to separate from one another due to their similar properties, various sorting techniques are used, such as density sorting to separate light metals from heavy metals, XRT or colour camera sensor technology to detect various characteristics, or Laser-Induced Breakdown Spectroscopy (LIBS) to separate metals based on their alloy.
Shredder Scrap
Shredder Scrap is produced during the shredding of bulky waste in shredding plants. These typically consist of:
- End-of-life vehicles (ELVs)
- Electronic waste (white goods, small electrical appliances and mixed electronic waste)
- Mixed scrap / bulky waste
- Industrial and commercial waste containing metal
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After initial shredding, the shredder scrap fractions are first classified into defined grain sizes. The material flow is then passed through a magnetic separator, where FE (E40) is recovered.
The remaining material flow still contains a variety of different materials such as non-ferrous metals, plastics, rubber, wood, etc.
This fraction should be further processed using suitable sorting technology in order to obtain reusable components and market them profitably.
ash
When waste is incinerated, energy is produced along with solid residues in the form of ash.
The targeted separation of recyclable materials not only reduces the amount of material that has to be sent to landfill, but also enables the recovery of valuable raw materials such as metals, glass and other recyclable components.
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The composition of slag and ash depends heavily on the type of waste incinerated and the incineration process used.
Although mineral components generally make up the largest proportion, the residues may still contain significant amounts of metal. Through targeted separation and processing, these can be recovered economically and returned to the material cycle.
E-Waste
Electronic scrap (PCs, smartphones, household appliances, etc.) is one of the fastest growing waste streams.
This fraction consists of a very diverse composition: metals (including copper and aluminium), printed circuit boards, plastics, glass and other non-metallic materials are sometimes closely intertwined.
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The challenge in e-waste recycling is to separate valuable metals from non-recyclable components in a targeted manner and to return recyclable materials as sorted as possible.
Sensor sorting systems are indispensable in this process for efficiently separating e-waste based on a wide variety of characteristics (colour, shape, conductivity, material composition, etc.).
Cable Scrap
Cable Scrap usually consists of a metallic conductor – usually copper or aluminium – and surrounding insulation made of plastic or rubber.
The high metal content makes cable scrap a particularly valuable recycling material. However, clean separation of metal and insulation material is a prerequisite for economical recycling.
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Depending on the cable type, cross-section and material composition, different processing and separation methods are used.
The recovered metals can then be returned directly to the recycling cycle, while the remaining plastic components are sent for further recycling or disposal.
Shear Scrap
Shear Scrap consists of a wide variety of materials, including unwanted components such as soil, stones, wood and plastics, but also valuable metals such as iron (Fe), aluminium (Al), stainless steel (VA) and copper (Cu).
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The recovery of metals is both economically relevant and necessary in order to comply with statutory landfill regulations, and usually begins with the separation of the non-valuable fine fraction.
This fine fraction can be efficiently screened out using a coarse particle sieve like SCREEN HEAVY At the same time, any remaining iron from this fine fraction can be recovered using an overband magnet.
Foundry Residue
Foundries produce various types of waste that may contain valuable metallic components. These include moulding sand, slag, filter dust and metal-containing residues from melting and cleaning processes.
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These residues often consist of a high mineral content, but at the same time contain iron or non-ferrous metal residues that can be recovered economically. The challenge lies in the fine grain structure and the often close connection between the metal and mineral content.
Targeted processing and suitable separation methods not only enable raw materials to be recovered, but also significantly reduce disposal volumes and costs.