Textile waste refinery for the production of recycled plastic, cellulose and dye

Textiles for clothing are a major user of plastics, in which the plastic component is frequently combined with natural fibres such as cotton and wool. Globally, 438 million tonnes of plastic were produced in 2017, of which 62 M tonnes were used in the textile industry (compared with 158 M tonnes used in plastic packaging). Plastics in textile waste are thus a major, but hidden, contributor to the plastic waste issue. In the UK, 2.5 M tonnes of plastic packaging and >1 M tonnes of textile waste are generated annually.

While plastic packaging has attracted attention and concern worldwide for some time, textile waste has only become prominent recently, in part because separating the plastic from the natural fibres and other components makes recycling textile waste a challenging task. A 2016 UK survey showed that textile waste goes to landfills 55%, incineration 26% and recycling/reusing 16%, with <1% textile waste used to generate material to be used for producing new clothing. Apart from old clothes recycled or reused via charity organisations, the majority of the plastic used in the textile industry is not recycled, contributing to plastic pollution and depletion of raw materials.

If the plastic component (mainly polyester) can be separated from cotton, dye and other components in the textile waste, it can be recycled into reclaimed fibres using the same method for recycling plastic bottles into textile products. Existing mechanical recycling technology can recycle textile waste composed of a single polymer, but is not able to treat complex textiles such as polycotton garments (a mixture of polyester and cotton). Chemical recycling methods break down the textile fibres into their building blocks and then synthesise new polymers and subsequently new fibres via appropriate spinning techniques. But chemical recycling is energy intensive and natural fibres, such as cotton (formed of cellulose) and wool (protein fibre), are degraded to a point that they cannot be used to generate new fibre, therefore losing their intrinsic value.

Researchers at the University of Huddersfield have recently developed an enzyme-assisted textile waste valorisation process that breaks down cellulose into glucose for biofuel fermentations, allowing recycling of the remaining polyester. The proposed project will modify this enzymatic approach to only partially break down cellulose to enable its separation from the polyester in polycotton, such that both components can be recovered and re-spun into new textile fibres.

The project will also apply ionic liquid extraction for the separation of cellulose from plastics, separately and in combination with enzyme processing. Ionic liquids can dissolve cellulose, but the high price of commonly used ionic liquids have limited their commercial application. Researchers at Imperial College London have pioneered the development of more sustainable and cost effective ionic liquid extraction processes using much cheaper ionic liquids. The ionoSolv process for sustainable cellulose production was selected by Scientific American as one of the Top Ten Emerging Technologies of 2019 and is currently being commercialised for the fractionation of waste biomass by Lixea Ltd. (www.lixea.co) at a £4 million bespoke pilot plant in Sweden. In this project, ionoSolv technology will be applied to recover both the natural cellulose fibres and the dyes from waste textiles, in forms suitable for reuse in new textile products.

The recycled polyester and cellulose will be re-spun into fibre at the Technical Textile Research Centre at the University of Huddersfield. The regenerated fibre will then be used by the industrial partner to demonstrate its suitability for making new textile products. The economic, social and environmental impacts of the novel process will be assessed for its benefits to stakeholders throughout the value chain - recyclers, manufacturing industries, retailers, consumers and society as a whole.