Logistics Portal
The industry has been striving to recycle textile waste since well before the European Green Deal, because the raw materials needed to produce fibers are finite.
This applies to both natural and fossil-based materials. We spoke to Michael Mächtig, process engineer for recycling technologies at Barmag, about how we can tackle and solve this problem.
- Mr. Mächtig, we read a lot about rPET; does that mean other polymers cannot be recycled at all?
When we talk about rPET today, we’re usually referring to a polymer that has been thermomechanically recycled from old PET beverage bottles. These bottles are ground into so-called flakes, sorted, washed, and then melted down in an extruder. The resulting material is processed into new products — such as new beverage bottles or polyester yarns. This process works well because beverage bottles are made almost entirely of PET and are designed to be recyclable.
This is not the case with other polymers and their applications. Many polyolefin-based products — such as polyethylene or polypropylene — are made from mixed materials or contain numerous additives due to their functional requirements, including dyes or UV-stabilizing components. Additionally, polyolefins are not as uniform as PET; there are many variants. As a result, thermomechanical recycling is only partially feasible. It often leads to reduced material properties, making the recycled output suitable only for lower-quality products — a process known as downcycling.
These and other polymers can only be transformed into high-quality products through chemical recycling. For polyolefins, pyrolysis is one such method. It produces a type of crude oil that is then refined. These are complex and energy-intensive processes.
For polyamide 6 (PA6), a different chemical process is used. PA6 is broken down into its monomer caprolactam, purified, and then repolymerized. Recycling is more challenging for polymers like polystyrene — the classic yogurt cup — or PVC.
- What is the particular challenge when recycling textiles? How, for example, can mixed fibers be separated?
Textile recycling requires a more nuanced approach due to the diversity of materials. There are more than 20 different types of yarns — from wool and cotton to polyester, polyamide, polyacrylic, elastane, and many more. Add to that the variety of dyes, prints, buttons, zippers, coatings, and so on. The material mix is so complex and variable that pre-sorting by material class is essential. Even then, it’s not possible to achieve a 100% PET content. Therefore, thermomechanical recycling — melting and reprocessing — is not viable without downcycling.
- Nevertheless, it is the declared goal of the European Union and the textile industry to recycle textile waste. Where do we stand on this?
Chemical recycling methods are currently being developed for textiles. These processes break PET down into its monomers, purify them, and rebuild them into new PET. We call this chemically recycled PET “crPET” to distinguish it from thermomechanically recycled rPET.
The special feature of chemical recycling — specifically the depolymerization of PET — is that crPET can be produced with a chemical structure and purity indistinguishable from virgin, petroleum-based PET. At least, that’s the goal of ongoing global development efforts. This is also the aim of our collaboration with Barmag and Evonik. Of course, the process must also be economically viable — crPET must not be more expensive than vPET. There’s still a lot of work to be done, as textile waste is highly variable, the processes are complex but must be robust, and investments in process technology must be economically sustainable.
