The development of a novel biorefining strategy for the valorisation of textile waste

The textile industry is worth over 3,000 billion dollars, representing 2% of global GPD. However, the model of fast fashion leads to production of "single use" clothes and other textile products. Therefore, textile products have a relatively short lifetime and are often disposed after a few uses. In the UK alone, over 1 million tonnes of textile waste are generated annually, which is significant even when compared with the amount of plastic waste (2.5 million tonnes annually). The majority of textile waste ends in landfills or incineration, while approximately a fifth of textile waste was recycled and reused and only ~1% was used to generate material for producing new clothing. To tackle the textile waste issue, Waste and Resources Action Programme (WRAP) launched the Textiles 2030 initiative recently to call government, textile industry and research institutes to work together and transform the current singular textile industry towards a circular economy in the UK. One of the key targets of Textiles 2030 is to "cut carbon by 50%, sufficient to put the UK textiles sector on a path consistent with limiting global warming to 1.5C".

To increase textile waste recycling, various approaches both mechanical and chemical have been investigated. However, although mechanical recycling technology can recycle textile waste composed of a single polymer, it is not efficient to treat complex waste such as polycotton garments (a mixture of polyester (PET) and cotton), a key component of municipal solid waste. Chemical recycling methods aim to break down the textile fibres into their building blocks and then synthesis 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) will be degraded to a point that they cannot be used to generate a fibre again. Recently, researchers at the Biorefining and Bioprocessing Centre at the University of Huddersfield developed an enzymatic assisted recycling process aiming to breakdown cellulose into its constituent sugar glucose and then ferment the glucose into lactic acid, from which a biodegradable plastic polylactic acid (PLA) could be synthesised. Using this technology, the aim is to selectively breakdown cellulose into smaller units to enable its removal from the PET in polycotton. The PET can then be used to make new PET fibre which potentially can be used to make new textiles.

It is proposed that by tailoring the enzymes used to breakdown the cellulose the cellulose can be separated from the complex textile waste while maintaining the length of the molecular chains long enough to be re-converted into textile fibre. The recycled short chain cellulose will be characterised and formed into fibre at Technical Textile Centre at the University of Huddersfield. The regenerated fibre from textile waste will be explored for its novel application, such as in wound dressing. The recovered PET will also be characterised and explored for making new cloth.

The economic, social, environmental impacts of this process will be assessed. Both the carbon and water footprint in addition to the dependence on non-renewable resources will be evaluated in order to assess the potential environmental benefits. The social impact of the process to all involved stakeholders (industries, retailers, urban and rural communities) will be also examined

Textile waste is a major component of municipal solid waste. Majority of textile waste ends either incineration or landfill, creating significant environmental problem and exhausting national resources to make new textile materials. There is an increasing research focus recently on the recycling of textile waste into reusable raw material. At the Biorefining and Bioprocessing Centre, University of Huddersfield an enzymatic assisted bioprocessing method was investigated. Cellulose fibre was hydrolysed to glucose, which was then fermented into lactic acid for the synthesis of poly-lactic acid; while the polyester was separated and spun into new polyester. However, complete degradation of cellulose in the textile matrix is challenging. A hydrolysis process took >70 hours and high loading rate of expensive cellulase was used.

In this project, we aim to develop a novel biorefining process for transforming both polyester and cellulose in the textile waste into new textile raw materials. Textile waste will be used as substrate for solid-state fungal fermentation to produce cellulase enzyme in house. The fungal biomass penetrates through the gaps of fibre bindings and excretes cellulase locally to partially break the cellulose chain as a type of biological pretreatment. Then the temperature is elevated to enable on-site enzymes to hydrolyse the cellulose in the textile waste. After a short hydrolysis process, the cellulose fibre will be broken into short chain cellulose and then will be released from the textile matrix, while the polyester fibre remains in the matrix. The polyester fibre will be characterised and explored for its potential in making new textile products, while the short chain cellulose will react with acetic acid to form cellulose acetate, and then cellulose acetate fibre will be used for medical textile application. The overall sustainability of the proposed process will be evaluated.