Textile Recycling

A T-shirt for four euros, pants for ten: The fast fashion trend continues unabated. No sooner worn than forsworn, these mostly low-quality items quickly end up in the trash. The textiles have been largely unrecycled – until now.   

Nearly 11 million tons of textile waste are generated in the EU every year. Most of it is incinerated or ends up in landfills. Previously, less than one percent has been recycled into new textiles. Thomas Fehn and his team at the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT intend to change this. In the EU Autoloop project, they are working with 14 partners from 7 countries to route textiles through a closed-loop system. While recycling processes for cotton fibers are already established, there are none for synthetic blended fabrics, which make up about half of the clothing produced worldwide. “Polyester and cotton fibers are so tightly intertwined that it’s extremely difficult to separate them,” says Fehn.

Textile Recycling of Blended Fabrics: An Innovative Process for Fiber Separation

Finnish project partner Aalto University in Helsinki has now successfully achieved this separation. The polyethylene terephthalate (PET) recovered in this innovative process and from which most polyester fibers are made is not a single type. Instead, it consists of various types of PET. It also contains dyes, impregnating agents, plasticizers and stabilizers. Fehn explains: “We can’t simply reuse this PET to produce new fibers. Instead, the basic chemical building blocks have to be extracted individually.” He and his team are accomplishing this with pyrolysis, a high-temperature decomposition process in the absence of oxygen. In this process, the starting material is not destroyed but rather is broken down into its molecular components. 

Pyrolysis with steam enables high-purity recycling

Breaking down PET produces crystalline terephthalic acid which often forms tough, waxy deposits in combination with other decomposition products. These can clog pyrolysis reactors or pipes. The Fraunhofer research scientists have developed a solution to this problem. They add steam to the reaction system at a temperature of roughly 400 degrees Celsius. “The steam cuts the molecules apart like a pair of scissors,” says Fehn. “We are thus able to break down the PET polymer chain into its individual building blocks and completely separate out the terephthalic acid to a very high degree of purity – nearly 100 percent – without anything sticking together.”

Terephthalic acid is a main component of PET. It plays a key role in determining the strength, stability and quality of the synthetic textile fibers and is produced almost entirely from petroleum-based raw materials. “Recovery is therefore especially important for the environment.” After cleaning and repolymerization into PET, the material can again be spun into fibers. 

Textile recycling requires smart collection and sorting systems

However, the actual conversion of worn-out sweaters or pants with holes into new goods also requires an intelligent collection and sorting system. The EU has established a key prerequisite for this in the form of mandatory separate collection of used textiles, which has been in effect since January 1, 2025. Under this regulation, these items can no longer be disposed of with general waste and must be sorted separately to promote recycling and reuse. Textile waste is then separated from wearable clothing in sorting facilities. British start-up Zori Tex, another partner in the Autoloop project, uses AI-supported image processing to sort used clothing by fiber type. Fehn explains: “The textiles are transported on a large conveyor belt. The AI detects blended fabrics with a high PET content. A directed air jet blows these specific items off the conveyor belt.” This automated procedure could yield a tenfold increase in sorting throughput and simultaneously reduce costs by 50 to 75 percent. 

Tracer technology for precise material detection

To further simplify and refine sorting in the future, the Autoloop team is joined by German company TLX in working on an intelligent tracer technology. Lasers will be used to etch invisible markers into the fibers. These will later provide information on the exact composition of the material. Fehn is convinced: “The ideas and technologies are already available; they just have to be implemented to give us a working closed-loop system.”