Recovery of Fibres : Textiles recycling: the sorting challenge

Today, only a tiny fraction of discarded textiles are recycled. While the clothing industry has doubled production in the last 15 years, the amount of time clothes are worn has fallen by more than 30%. At the same time, the growing demand for low-cost fast fashion is driving down the quality of materials, making them harder to reuse or recycle. According to the Ellen MacArthur Foundation, an estimated 114 million tonnes of textile waste is generated each year. Of the clothing collected for recycling, 12% is down-cycled into lower-value applications such as insulation, and less than 1% is used to make new clothing in a closed-loop circular economy. The high polyester content in fast fashion also means that an increasing amount of discarded textiles are being incinerated in waste-to-energy plants due to their high calorific value.

Increasing consumption of clothing, coupled with decreasing wear time and increasing use of synthetic materials such as polyester and nylon, is exacerbating the negative impact on the environment. When textiles are washed, large quantities of plastic microfibres are released into the ocean, accounting for 35% of microplastic pollution. Improper disposal can also result in flat textiles being released into the environment, endangering wildlife on land and marine life.

Policy makers have a key role to play in driving up recycling. For example, in Europe, the Commission presented an EU Strategy for Sustainable Textiles in 2022, which includes extending the life of textiles by recycling the materials they contain into new, high-quality products. The revised Waste Framework Directive requires EU member states to have systems in place for the separate collection of textile waste by early 2025, with new collection and recycling targets coming into force at the same time. The infrastructure to collect, sort and recycle these materials will need to be expanded rapidly to meet the new regulations.

Clothes are made up of different fabrics, fastenings and accessories such as buttons or zips, and contain a variety of raw materials - combinations of natural and synthetic fibres, plastics and metals. This makes sustainable disposal a complicated matter.

“The recycling industry requires pure fractions or very specific mixtures,” explains Annika Ludes, Engineer for Digital Solutions at STADLER. “This means removing the fixtures and accessories from the fabric. The different materials in the garment – the outside fabric, the lining, the seams – need to be separated, then the different fibres in each fabric (cotton, elastane, polyester, etc.) must be sorted.”

At present, textile sorting is done manually and only a small proportion of the output is suitable for recycling. However, research is underway to automate the process to produce the high quality fractions needed to meet the recycling challenge.

STADLER - a leading supplier of sorting equipment for the recycling industry - is researching automated sensor-based solutions for textile sorting. In 2017, in partnership with TOMRA, the company designed and built a small pilot project plant in Avesta, Sweden, as part of the second phase of the government-funded Swedish Innovation Platform for Textile Sorting (SIPTex) project, which aims to develop a sorting solution tailored to the needs of textile recyclers and the garment industry. This was followed in 2020 by the third phase of the project: the world's first industrial-scale, fully automated mixed textile waste plant capable of achieving the purity and recovery levels required for recycling and reuse.

The plant, located in Malmö, processes pre-consumer waste from textile manufacturers (cuttings and rejects) and post-consumer waste, which consists of clothing and household textiles and may contain non-textile parts such as buttons and zips. The material is supplied in bales weighing between 350 and 500 kg and is sorted whole. The plant has a capacity of up to 4.5 tonnes per hour on a single line.

The method developed by STADLER in cooperation with TOMRA in the SIPTex project starts with the waste textiles entering the plant in batches, dosed and fed by conveyor belts into four sensor-based TOMRA AUTOSORT® units.

“Because of the nature of the textile material fed into the plant, the feeding system and dosing are very important to the success of the sorting process,” explains Dr. Bastian Küppers, Engineer for Digital Business Development at STADLER. “The STADLER dosing drum features mechanical components specially designed to handle the soft, flexible textile materials, of various shapes and unpredictable sizes, prone to tangling. Similarly, the design and layout of the conveyor belts, hoppers and chutes need to be designed to avoid tangling of long pieces of fabric.”

Also key to the process is the TOMRA NIR (Near Infrared) sorting technology, which is able to detect and differentiate between different types of textiles in a first step. A second optical sorter is added to further remove contaminants.

As the textile industry moves towards a circular economy, spurred on by public opinion and legislation, the demand for textile sorting equipment will grow at an accelerated rate. STADLER has already seen an increase in interest in textile sorting equipment and has been approached by companies in the recycling sector. “At STADLER we are seeing many interested parties who would like to visit the textile sorting plant we designed and built in Malmö,” comments Annika Ludes.

Thanks to its extensive know-how in the design and construction of sorting plants, the specific experience gained from the SIPTex project and the expertise of its technological partners such as TOMRA, STADLER is in a unique position to meet this new demand. Its holistic approach enables it to develop complete solutions tailored to each customer's needs.