Issue 07/2022 Special Edition

Fibres / Textiles /

Fibres / Textiles / Nonwovens From cotton rag to modern functional textiles Every year, an estimated 25 million tonnes of cotton textiles are discarded around the world. In total, 100 million tonnes of textiles are thrown out. In Sweden barely 5 % is recycled, most of the material goes straight into an incinerator and becomes district heating. In other places, it is even worse, as clothes usually end up in landfills. “Considering that cotton is a renewable resource, this is not particularly energy-efficient”, says Edvin Ruuth, a researcher in chemical engineering at Lund University. “Some fabrics still have such strong fibres that they can be reused. This is done today and could be done even more in future. But a lot of the fabric that is discarded has fibres that are too short for reuse, and sooner or later all cotton fibres become too short for the process known as fibre regeneration”. Now the researchers succeeded in breaking down the plant fibre in cotton – the cellulose – into smaller components. The process involves soaking the fabrics in sulphuric acid. The result is a clear, dark, amber-coloured sugar solution. “The secret is to find the right combination of temperature and sulphuric acid concentration”, explains Ruuth, who fine-tuned the recipe together with doctoral student Miguel Sanchis-Sebastiá and Professor Ola Wallberg. Glucose is a very flexible molecule and has many potential uses, according to Ruuth. “Our plan is to produce chemicals which in turn can become various types of textiles, including spandex and nylon. An alternative use could be to produce ethanol”. One advantage of this step would be to keep the value of the original biobased material, cotton, within the textile industry value chain. This would reduce the waste produced by the industry, while at the same time reducing the amount of raw material needed for textile production. One of the challenges is overcoming the complex structure of cotton cellulose. “What makes cotton unique is that its cellulose has high crystallinity. This makes it difficult to break down the chemicals and reuse their components. In addition, there are a lot of surface treatment substances, dyes, and other pollutants which must be removed. And structurally, a terrycloth towel and an old pair of jeans are very different”, says Ruuth. The concept of hydrolyzing pure cotton is nothing new per se, the difficulty has been to make the process effective, economically viable, and attractive. When Ruuth started making glucose out of fabrics a year ago, the return was a paltry 3–4 %. Now he and his colleagues have reached as much as 90 %. Once the recipe formulation is complete, it will be both relatively simple and cheap to use. However, for the process to become a reality, the logistics must work. There is currently no established way of managing and sorting various textiles that are not sent to ordinary clothing donation points. Fortunately, a recycling centre unlike any other in the world is currently under construction in Malmö, where clothing is sorted automatically using a sensor. The aim is to use recycled textiles to make padding, insulation, and cloth for industrial cleaning, slowly increasing the amount of textiles recycled from 3,000 to 16,000 tonnes over five years. The project marks the third phase of the Swedish Innovation Platform for Textile Sorting (Siptex), coordinated by IVL Swedish Environmental Research Institute, and comes after a successful pilot project in Avesta. Once the technology from Lund is in place, it may be possible to not only reduce the proportion of fabrics going to district heating but also increase the quality of the recycled fabrics, avoiding down-cycling as much as possible. The research was recently awarded EUR 590,000 (SEK 6 million) in funding by the Swedish Energy Agency. AT Reference: Miguel Sanchis-Sebastiá, Edvin Ruuth, Lars Stigsson, Mats Galbe, Ola Wallberg. Novel sustainable alternatives for the fashion industry: A method of chemically recycling waste textiles via acid hydrolysis. Waste Management, 2021; 121: 248 DOI:10.1016/j.wasman.2020.12.024 https://www.ivl.se/ | https://www.lunduniversity.lu.se/ Edvin Ruuth of Lund University (screenshot from the video clip © Lund University) Cotton waste (left), clear, dark, amber-coloured sugar solution (right) (screenshot from the video clip © Lund University) Info See a video-clip at: https://youtu.be/B1V- -prLs08 28 bioplastics MAGAZINE [02/21] Vol. 16

Enzymatic degradation of used textiles for biological textile recycling The competence centre Bio4MatPro is part of the Bioeconomy Model Region initiative in the Rhenish Mining Area and funded by the German Federal Ministry of Education and Research (BMBF). The ambition of Bio4MatPro is the biological conversion of different industries such as chemicals, consumer goods, and textiles to become an essential part of a circular (bio)economy. The project EnzyDegTex focuses on the biological transformation of textile recycling using enzymatic degradation and microbial synthesis of chemical base materials and (bio)polymers. Safeguarding economic resources and capacities in the Rhenish Mining Area, Germany, and Europe, the development and expansion of circular economies will be an important aspect in the future. Textile waste is currently disposed of in a linear rather than circular manner. Thus, there is a very high, almost entirely untapped potential for establishing circular economic processes for textiles. More than 1.5 million tonnes of post-consumer textile waste are generated annually from private households in Germany [1]. Recycling textiles poses challenges due to the complexity of textile constructions with diverse, often unknown manufacturer-dependent mixes of different fibre materials, extensive use of additives and dyes, and multi-layer constructions with mechanically inseparable layers. Therefore, recyclin widely used textiles such as polyester-cotton blends is challenging with the recycling approaches available today. Instead, the majority of textile waste is currently downcycled once into low-quality products like painting fleeces or insulation materials, which are disposed of later at the end of their second use phase. The aim of project EnzyDegTex is to close the loop of textile recycling and to provide renewed raw materials from textile waste for the chemical, plastics, and textile industries. The use of enzymes enables selective degradation of materials present in textiles, e.g. polyesters in polyester-cotton blends. Thus, custom-fit recycling processes can be designed using the enzymatic approach, so that complex textile constructions can be treated and respective raw materials returned. For the development of the EnzyDegTex recycling process, process chains with the following sub-steps are being investigated: • Selection and preparation of the textile waste • Development and implementation of the enzymatic degradation • Enrichment and purification of suitable degradation products • Microbial synthesis of chemical base materials and polymers • Development and validation of suitable spinning processes • Development of textile products The development of enzymatic degradation processes includes the screening and engineering of promising enzymes that can specifically degrade synthetic polymers or typical additives and dyes from textile material blends. The degradation products are subsequently used as feedstock for the microbial synthesis of textile raw materials. Target raw materials are, for example, mono – and oligomers for the synthesis of melt – or solvent-spinnable polymers. The spinnability of the purified polymers is first evaluated through polymer characterisation measurements and spinning trials on lab-scale spinning plants. Subsequently, melt and solvent spinning processes at a pilot scale are developed for suitable polymers. The resulting yarns are further processed into textile demonstrators as nonwovens, weaves, or knits using classic textile surface manufacturing processes. In addition, the yarn and textile properties are characterised and compared to benchmark products from clothing applications. After three successful project years, the feasibility of biological textile recycling into new chemical base materials and textile products is demonstrated. The implementation of developed products and processes in the Rhenish Mining Area has great potential to play a key role in transforming the linear textile disposal into a circular (bio)economy. With the high availability of textile waste and the local biochemical industry, the region has excellent conditions for creating valuable products from textile waste and new jobs. Moreover, in terms of sustainability, a contribution towards resource efficiency will be made and the amount of incinerated or exported and landfilled textiles will be reduced. www.ita.rwth-aachen.de Project partners from RWTH Aachen University: Institute of Biotechnology (BIOTEC) Institute of Applied Microbiology (iAMB) Institut für Textiltechnik (ITA) By: Ricarda Wissel, Stefan Schonauer, Henning Löcken, Thomas Gries ITA Institut für Textiltechnik of RWTH Aachen University, Aachen, Germany Fibres / Textiles / Nonwovens Enzyme for polyester degradation from textile waste [1] bvse e.V: Bedarf, Konsum, Wiederverwendung und Verwertung von Bekleidung und Textilien in Deutschland, 2020, URL: https://bit.ly/ bvse-studie2020 bioplastics MAGAZINE [02/21] Vol. 16 29