The use of certain technologies in the sorting of end-of-life textiles could increase the amount of discarded clothing and textiles that is recycled in a financially viable way, according to a report from WRAP, Defra and Manchester Metropolitan University. The report builds on previous work on textile recycling commissioned by the Waste and Resources Action Programme (WRAP) and Defra, and the authors identify four approaches with the most potential: manual sorting; Fourier transform infra-red spectroscopy (FTIR); radio frequency identification (RFID) tags; and traditional bar codes.
The underlying premise of the study is that the ability to accurately identify textiles by a variety of attributes might provide a route to a more circular textile economy and improved sustainability in this area. It is TRG’s experience that technologies of this sort are particularly useful in the traceability and provenance of responsibly sourced raw materials (particularly timber), but it is interesting to see its potential at the end of a product’s life cycle in recycling.
Manual sorting is the incumbent approach. It currently operates successfully, but at a small profit margin ‘because sorting criteria are not aligned with the markets for recyclates’. According to the authors of the report, using this method it is only possible to separate textiles by parameters that humans can detect by sight and touch, meaning that the description of the output bins is limited to: ‘colour; fabric; quality; style; brand; complex textiles; unusual’.
FTIR is one of a family of hyperspectral imaging techniques that can determine the colour and fibre content of a textile. However, it is identified as not yet having been developed to the point where it discriminates significantly better than a skilled manual sorter. When this technical ability is realised, FTIR could be viewed as a useful augmentation to manual sorting, ‘since it can refine some of the steps of sorting by fibre type and colour, and hence add value to those output streams’.
An RFID tag is a small wireless device that can carry data and which can be remotely read. The tag travels with the textile throughout its life and contains a precise description of it and its properties. At the end of the product’s life cycle, the tag can be read, permitting sorting of the textile to an appropriate recycling bin. This allows for a high specificity of textile sorting, which means that the waste stream can be processed to achieve best value. However, low cost RFID tags that can survive multiple laundry cycles do not yet exist, and tag readers will require modification to guarantee association of one tag with one textile during interrogation of the tag.
A 2D bar code label is another approach to carrying information about the textile to instruct sorting in the recycling process – the black and white pattern of the label is read by camera and decoded by computer – as with RFID, product data can be encoded onto this label. FTIR, on the other hand, can only sort by fibre type and colour, whereas RFID tags and 2D bar codes can sort by any level of description that can be encoded. Economic models suggest the capital and running costs of sorting by RFID and 2D bar codes could be easily recouped through reduced operating costs and by targeting higher value markets for recyclates once the proportion of marked textiles in the waste stream is very high. According to the report, although work is required to identify the most appropriate data format for the bar code and to verify labels will remain machine-readable at the end of the use phase of the textile, both 2D bar codes and RFID tags are economically favourable compared with manual sorting and FTIR.
Recycling and responsible sourcing are both important aspects of improving sustainability and reducing our impact on the environment – at TRG we know from years of experience that robust approaches to the identification and tracking of products throughout their lifecycle are an important part of this process. Identifying the most effective ways of doing this is an important first step towards achieving a more circular economy in the global textile industry.
Read the full report here.