Recycling with NIR Pectroscopy

Efficient textile recycling with NIR Spectroscopy

Published 20.09.2020

 

We are sure that most of us don’t know that the textile industry is the world’s second-largest industrial polluter after the oil and petrochemical industry. Textiles account for 10% of global carbon emissions, use vast amounts of water and energy and get produced with highly toxic chemicals. Petrochemical textile materials such as acrylic, modacrylic, polyester, nylon, and spandex are immensely toxic and pollutive to the environment, as their production requires significant amounts of energy, water and chemicals, not to mention being a massive source of microplastics.

 

This combined with rapid fashion culture and the short lifetime of clothing, on the average of about three years, causes an immense waste problem: 85% of clothes end up in a landfill. Once in landfills, natural fibers can take hundreds of years and synthetic fibers thousands of years to decompose. They also release methane and COgas into the atmosphere. Additionally, synthetic textiles are designed not to decompose at all. In a landfill, they release toxic substances into groundwater and surrounding soil.

 

Do you know what happens to your old clothes when you throw them away?

 

Globally

  • 87% of disposed textiles are sent to a landfill or incinerated
  • 12% are mechanically recycled by cutting or shredding into fibre, insulation material or rags
  • Less than 1% are chemically recycled
  • In U.K, 50% of collected textiles are re-used, about 50% are recycled and 60% of recovered wearable clothes are exported to other countries

 

There is an obvious need to recycle our textiles better. Fortunately, NIR spectroscopy could be an enabling technology towards more ecological recycling processes.

 

Different ways of textile recycling

Textile fabrics and clothing commonly consist of composites of synthetic plastics and cotton, which is a biodegradable material. The composition influences the method of recycling and durability. Since fiber production requires huge amounts of energy and resources, re-using the textiles is highly recommended from an ecological point of view. It can also increase the lifetime of clothing as our clothes get to have multiple lives before getting recycled.

 

Incineration, i.e. burning waste, is one of the most common solutions for managing textile waste. Incineration costs are quite high, and the amount of reclaimable energy is low compared to the total energy consumption during the manufacturing process. Additionally, burning textile waste increases the amount of CO2 released into the atmosphere thus making it an unsustainable solution.

 

More sustainable alternatives are the re-use of second-hand textiles by consumers and recycling the textiles properly. Mechanical recycling is done by cutting and shredding, and it produces weaving and non-woven materials. Thermal recycling, which is applicable to meltable synthetic fibers, produces raw materials for extrusion or lower value products, and chemical recycling of synthetic fibers, mainly PET, transforms the fibers back to their original monomers which then get recycled by synthesizing to similar polymers. Recycling textile fibres saves both raw materials and energy.

 

NIR spectroscopy to the rescue

For natural textiles, incoming items get sorted by color and material. By segregating colors, the need for re-dying can be reduced or even eliminated, reducing pollutants and energy usage. The item is then shredded into sloppy fibers and combined with other selected fibers, depending on the planned end use. Once cleaned and spun, fibers can be compressed for re-use. Textiles sent to the flocking industry are used to produce, for example, filling material for furniture padding, panel linings, loudspeaker cones, and insulation materials. Currently, there are new innovations with emerging solutions and products using cotton, polyester, cotton-polyester blends and recycled paper board, to develop technical innovations for producing high quality materials and innovative design products.

 

Collected clothing is, for the most part, sorted and graded manually. These sorted items are sent to different destinations. Currently efficient solutions for automated sorting of textiles are missing from the textile value chain completely. To be able to operate efficiently and profitably, automated solutions are needed to manage high material throughput and to meet quality requirements (purity, fiber types and colors, among others). The precision of manual sorting is generally insufficient for higher quality textile recycling. Efficient sorting forms a crucial link between collection and adequate use of collected materials and is an important step in closed textile loops.

 

NIR spectroscopy is based on molecular absorptions measured in the near infrared part of the spectrum. The infrared light from a light source is partially and selectively absorbed by the target surface, and the reflected light creates a characteristic spectrum of each fibre type or blend combination. The spectrum is then compared with a predefined database and thereby it is possible to identify the material.

 

NIR technology can be used to identify garments made of pure cotton, polyester, acrylic, wool, polyamide, silk and man-made cellulosic (viscose, modal and lyocell) fibres as well as cotton/polyester blends. An interesting finding is that at least 2% of the garments used in a research study using NIR testing were incorrectly labelled. This further proves that manual sorting is an inadequate way of recognizing different materials.

 

Solving the problem world-wide

There are several initiatives around the world attempting to solve the textile waste issues. In Finland, one example is the Telaketju project which facilitates textile recycling and simultaneously creates added value and new business opportunities around textile recycling and circular economy. One of the project’s participants is LSJH, a regional waste management company in Southwest of Finland. LSJH has successfully tested and demonstrated how a NIR spectroscopy-based textile scanner identifies and sorts textiles at Ruisrock festival.

 

Spectral Engines offers unique solutions to textile recycling and enables more efficient textile sorting with hand-held scanners at the source end of the value-chain. This makes manual sorting faster and improves the quality of raw materials with more accurate recognition of textile fibers used in garments.

 

Additionally, Spectral Engines’ scanners and sensors can be used in the design and manufacturing of textile sorting machinery to automatically identify garment and fiber types and run automated sorting processes with higher accuracy and efficiency. Furthermore, Spectral Engines’ sensors can be applied to a variety of manufacturing processes in process control functions and can be integrated into industrial IoT-solutions.