Both established and startup apparel brands look to recycled textiles as a way to stand out in the marketplace. That said, many also assume that all recycled fabrics are equally “eco-friendly” – which is not necessarily the case.
In this article, written by Shufen Lee, you will learn what clothing brand owners and designers must know about chemical recycling, mechanical recycling, polyester, cotton, rPET, brands and new innovations.
Textile recycling is an important approach that addresses the textile waste and pollution issue caused by the rise in consumption and mass production in fast fashion.
Across the industry, there is an increasing awareness of the environmental, social and economic impacts of the current linear system of take-make-dispose. The take-make-dispose model has resulted in large volumes of waste in every area from raw material extraction to distribution and usage.
The Ellen MacArthur Foundation estimated that less than 1 percent of material used to produce clothing is recycled into new clothing. This represents a loss of more than 100 billion USD worth of materials each year.
In recent decades, there has been an increasing call for action among stakeholders, which have led to, and continue to, drive developments in improved practices and innovative technology.
The goal is to shift from a linear model to a regenerative circular system in which material usage are kept and maintained within closed-loop cycles, and associated waste, energy and emission are minimized or gradually phased out.
Recycling plays an important role in transitioning to a circular system. Although recycling technologies have long existed, textile recycling has only started to gain more awareness and popularity in the last decade.
Frequently targeted fibres for recycling
Did you know that the most frequently targeted fibres for recycling are polyester and cotton?
This is because both fibres are the most common fibres produced globally. Based on the 2018 preferred fibre materials market report, polyester and cotton both account for 51% and 24.5% of global fibre production in 2017.
Polyester is a synthetic fibre and Polyethylene terephthalate (PET) is the most common subclass. The raw material components of PET are generally derived from petrochemicals. Cotton, on the other hand, is a natural fibre that grows around cotton seed and contains mainly cellulose, an organic compound mainly found in plants.
Open Loop vs Closed Loop
The terms open and closed loop recycling are frequently used in the context of circular economy. Open-loop recycling means materials are flowing to a different product value chain. Post-consumer PET bottles that are being recycled to make filling materials or polyester fibres is an example of open loop recycling. Whereas, closed loop means that materials are being recycled back into the original products they served (e.g bottle-to-bottle, fibre-to-fibre).
Typically, open loop recycling presumes that materials will be cascaded to lower value uses due to degradation in quality but this may not be true in the future. With ongoing developments and innovations, waste materials can flow to where there is the greatest demand and market value.
Types of recycling
Generally, there are two types of recycling which are mechanical recycling and chemical recycling.
Mechanical recycling involves breaking down post-industrial waste (materials arising from industrial and commercial processing and manufacturing of textiles) or post-consumer waste (items returned or disposed of by consumers) mechanically into products of different physical properties.
Chemical recycling includes processes in which the chemical structure of the waste material is depolymerized or broken down into its constituent components (monomers, oligomers or other intermediates), and followed by re-polymerization into virgin material.
This is the most common recycling approach. The technology has long been well established for recycling PET bottles to polyester fibre and cotton recycling.
The process generally includes the following steps:
1) Material and colour sorting
Mechanical recyclers often prefer homogenous or near homogenous feedstock in terms of fibre type and colour (i.e 100% cotton).Therefore, manual sort by fibre type and colour is required to ensure that textiles received from textile merchants meet feedstock specifications. Sorting by colour also eliminates the need for re-dyeing.
2) Pulling or Shredding
Metal accessories that might interfere in the recycling process, such as buttons and zippers are removed. Then the fabric passes through several cylinders filled with sharp points to break the fabric down into fine cotton flock.
Recovered fibres are often shorter than its virgin counterpart fibre because of degradation of fibre during the pulling and shredding process. Therefore, they are combined with virgin fibres to improve the properties of the final recycled yarn.
The process of aligning fibres using a combing process to produce a cotton ribbon called sliver, which can then be spun.
This is the process to produce yarn. Some fibres are not spun into yarns as they are compressed as nonwoven products for production of insulator pads and filling materials. This practice of recovering and reusing as a lower-value product is called downcycling.
This is the process to convert yarn to fabric.
In the case of synthetic fibres such as polyester, post-consumer PET bottles are the most common feedstock for mechanically recycled polyester. PET bottles are shredded, melted into pellets and subsequently undergo melt extrusion to be processed as new fibres
As easy as mechanical recycling may sound, most present-day recovery systems for post-consumer waste textiles is actually a downcycling process. For example, PET bottles, which generally have higher intrinsic viscosity (IV), a physical property that reflects the material’s tensile strength, are most often recycled into PET yarns with lower IV value.
Degradation of fibre also occurs with fibre-to-fibre mechanical recycling. Therefore, mechanically recycled material may not be able to be recycled a very large number of times since each time the quality degrades further. As a result, it is often cascaded down to “lower” value materials (materials that are less sensitive to shorter fibres), such as nonwoven products used for filling materials and insulations.
However, it is reported that mechanical recycling methods have gradually been refined to produce fibres of sufficient quality to be regarded as closed loop fibre-to-fibre processing rather than downcycling.
Some of the more refined mechanical fibre-to-fibre processes for recycling cotton can deliver cotton fibre that are about 25% to 30% shorter than virgin fibre.
One of the setbacks is that majority of the consumer waste is made of blended materials and the different blends need to be segregated before being recycled. At this moment, it is not possible to segregate the fibre types mechanically. Therefore, most recyclers only accept 100% homogenous materials (from collectors for closed-loop mechanical recycling. However, if the goal of recycling is to produce nonwoven products, such requirement may not be applicable.
This process can be performed on cellulosic fibres (plant-based fibres such as cotton), or synthetics (polyester and nylon) or a blend of cotton and polyester (polycotton).
Chemical recycling has the ability to return synthetic waste materials to the same physical quality as its counterpart virgin fibre. Chemical recycling of natural fibre, however, does not convert waste materials back to virgin material. It often involves converting cotton waste into dissolved pulp and then blending with other plant-derived pulp products before processing them as regenerated yarn. This results in man-made cellulosic (MMC) materials with increased physical properties thus allowing the upcycling of post-consumer materials in addition to waste diversion from landfills.
Currently, the chemical recycling performed on cellulosic fibres is progressing towards scaling-up, while chemical recycling of synthetics (polyester and nylon) already includes some full-scale developments, even though it is limited to a few suppliers.
The earlier stages of chemical recycling is very similar to mechanical recycling which includes sorting, preparation and shredding or fragmentation. The subsequent steps are:
1) Fibre Dissolution
Propriety solvent is used to selectively target cellulosic and/or synthetic fibres solvents. Where two outputs are recovered, two solvents are used – one per fibre type for each of the polyester and cellulosic fractions.
Separation of cellulosic solvent and/or synthetic fraction from other fractions for further processing. Other fractions may contain any fibre types not targeted by the chemical recycling process, and other materials, including finishing chemicals and dyes. Some dyes are currently disposed of in the waste fractions and sent to landfills although recently there are more developers seeking to recover dyestuffs from the process.
a) Synthetics recovery process
Recovery requires repolymerization followed by further processing. Recovered polymers can be then processed in the form of solid state (resins) or fibres. The benefit of recovering polymer is that its physical properties can be retained or altered to enable upcycling materials.
b) Cellulosic recovery process
Cellulosic fibres are recovered as dissolving pulp, which may be used directly in a wet yarn spinning process or dried for sale to regenerated yarn producers. Cellulosic recovery produces viscose-like fibres however, and does not return the material to its counterpart virgin fibre.
c) Solvents recovery
The solvents are recovered to be used in future cycles. For environmental and cost reasons, chemical processes have been designed to capture and conserve solvents and to minimize waste and emissions. Solvent loss is reported to be as low as between 0.6% and 1% per cycle in batch processing.
4) Repetition of the above processes (step 1-3)
Repeated cycles of dissolution and recovery may be needed to fully remove contaminants and increase the purity/quality of the recovered fibres. Some reactive and dyestuffs may remain chemically bonded to the fibre during the dissolution process.
This is the process to produce yarn.
This is the process to convert yarn to fabric.
It is quite prevalent in the textile community to define the ideal recycling system as one where reclaimed textiles are converted back into virgin quality yarns to make new textiles via fibre-to-fibre recycling.
Chemical recycling is the only technology that can truly achieve this vision because it is able to remove all unwanted constituents, colorants, surface treatments, and other auxiliary chemicals used in textile production.
Waste materials with a high degree of contamination and physical degradation that were previously rejected by mechanical recyclers can now be recycled chemically.
For PET materials, chemical recycling can also address one of the challenges of mechanical recycling: meeting higher IV requirements. It hits the “reset” button to start the cycle over, producing virgin quality recycled resins that can be solid-stated to meet the IV necessary for any specific end application.
Furthermore, recycled PET is agnostic about the form or function the polymer serves. Recovered polymer can be in the form of solid state to be converted back to bottles, or in PET fibres to be processed into polyester yarns.
Chemical recovery process also has the potential to take in various fibre blends from the post-industrial or post-consumer textile waste, although this is still in the development phase. Majority of the textiles are of polycotton blends. Being able to deal with blended fibres to produce more than one output is very important.
Currently, the minimum feedstock required for fibre-to-fibre chemical recycling of polyester is at least 70-80% for PET materials and 100% unblended fibre for cotton and nylons. It is just a matter of time before chemical recovery process will be able to separate any amount of blended fibre, thus allowing a higher proportion of the textile to be recycled.
Not all fibres can be chemically recovered however. Chemical recovery of animal based fibre such as wool or cashmere is not practiced. The wool fibres are relatively long, and therefore, well suited for mechanical recycling. There is ongoing research on the recovery of keratin protein from animal fibres, but the aim is to convert for use in other applications such as biomaterials, resins and adhesives.
Furthermore, Nylon 6-6, which is one of the most common polymer found in Nylon fibre cannot be chemically recycled. Nylon 6-6 and Nylon-6 comprise approximately 85% of nylon material used. Nylon 6-6 is a more complex monomer than Nylon 6 and chemical recovery is more challenging as it may require larger volume of reagents. Currently Nylon 6-6 can only be recycled mechanically whereas either of the above methods can be used to recover Nylon 6.
Examples of commercially available suppliers for mechanical and chemical recycling
|Fibre||Mechanical Recycling||Chemical Recycling|
|Polyester||Hyosung (Korea): RegenTM polyester yarn that is recently given Eco-Mark from the Japan Environment Association and is also GRS certified||Far Eastern New Century (Taiwan): Topgreen® recycled products that are GRS & Oeko-Tex Certified, processed from 100% Post-Consumer Recycled Polyester|
|Ganesha Ecosphere Limited (India): Leading rPET supplier in India and continues to expand its rPET production capacities in other areas in India||Polygenta (India): ReNewTM patented technology that can depolymerize post-consumer PET bottles to filament yarns. In full-fledged production since 2012|
|Polylana (USA): Polylana® staple fibre comprises of a proprietary blend of innovative modified polyester pellets and modified rPET chips||Teijin (Japan): ECO CIRCLETM recovery system can separate and eliminate additives and colorants not only from PET bottles but also from other polyester products|
|Cotton||Hilaturas Ferre (Spain): Recover® yarn made from no added dyes. 50% recycled cotton blended with other materials(rPET ,acrylic, virgin organic cotton, TENCEL®)||Lenzing (Austria) : TENCEL x RefibraTM lyocell fibre made with 30% reclaimed materials from post-industrial cotton scraps|
|Giotex (Mexico,USA) :Pre-coloured post-industrial cotton waste is used to produce GiotexTM yarn with 75% recycled cotton blend||Asahi Kasei’s Bemberg (Japan) : BembergTM cupro fibre made from 100% cotton linter, a post-industrial residue of the cotton processing|
|Nylon||Unifi (USA): 100% post industrial waste is used to produce Nylon-6 REPREVE® chips via propriety chip extrusion and texturizing process||Aquafil (Italy): ECONYL® yarn is a 100% recycled nylon created by processing post-industrial and consumer waste (fishing nets, carpets and textile waste) to its base monomer called caprolactam|
|Wool||Geetanjali Woolens (India) : Yarns made of primarily recycled wool with blends of virgin wool or virgin synthetic fibres||Not commercially available yet|
Challenges of Mechanical and Chemical Recycling
Chemical recycling technologies are not currently in the commercialization phase. Mechanical recycling, on the other hand, has long existed and been practiced, especially for PET and cotton. Despite that, textile recycling is not widely adopted. One of the reasons is the difficulties in demonstrating cost effectiveness at scale.
To remain competitive in the market, recycled textiles should not be seen as premium outputs. Virgin materials are often cheaper than recycled materials, thus creating a weak market of recycled materials.
This is further exacerbated by the ban on importing different types of solid waste such as plastic bottles and textile waste to China in 2018. Since China has the highest capacity in producing PET, this ban has resulted in lower recycled polyester production and increased the availability of virgin PET production.
Many companies have already relocated recycling production to other Asians countries and the prices for recycled polyester have already been increasing as a reaction to the ban. In the long run however, this may help accelerate companies to seek better solutions, expand on domestic recycling infrastructure and change consumer behavior.
Besides, it is challenging to get funding for innovations for large-scale commercialization, especially when the demand for recycled fibre is still low. Consistent high quality of outputs, demand for recycled fibres and competitive pricing for cost-effectiveness at scale are critical in determining the success of this undertaking. It requires a leap of faith from investors because if one of the factors is missing, the likelihood of success of the implementation will be affected.
Another common issue is the difficulty faced by recyclers in aggregating waste materials from a variety of sources and obtaining the volume of feedstock necessary to achieve economies of scale. Therefore, it is important for coordination across the supply chain to stimulate the adoption and development of textile recycling systems. Coordination includes determining where feedstock comes from and setting a supply chain infrastructure with networks of suppliers.
Having a robust network of suppliers can also ensure that collectors know whom to turn to in order to transfer unwanted waste materials. Recyclers can also aggregate multiple sources of feedstock available within a given region in order to reduce the cost of material transportation.
To create more demand, it is important to increase awareness among industry and consumers. In order to do so, it is important to get everyone on board to advocate for this good cause.
Knowledge transfer among the expertise and different stakeholders is a great start to increase understanding surrounding the progress and constraints with current recycling technologies.
For example, the rPET round table organized by Textile Exchange (a global non-profit organization that works closely with members to drive industry transformation in sustainable practice) is a global multi-stakeholder network comprising individual members, companies and organizations. Members meet virtually every month as well as annually during the Round Table conference with the aim of facilitating greater levels of understanding and solution building towards higher uptake of recycled polyester.
Ongoing research and developments towards economies of scale
Innovations in Sorting
Recycling currently depends on enormous labour to separate and manage the various textile waste streams. This includes the characterization, identification and separation of constituent components (i.e. trims, buttons, zippers, and threads), fibre blends, as well as dyes and chemicals. For more efficient recycling, there is an increasing need to develop automated sorting and fibre identification to maximize the value of the recyclable fraction.
Various optical sorting technologies, such as a spectroscopic-based approach, have been explored and are currently being developed, or are very close to commercial adoption phase. For example:
Fibersort Project: Fibersort is a technology which uses near infrared spectroscopy (NIRS) to automatically sort large volumes of mixed post-consumer textiles in 45 different fractions based on their fibre composition and colour. The sorting technology can now sort at a rate of about 900kgs of post-consumer textiles per hour. Circle Economy, Valvan Baling Systems, ReShare, Procotex, Worn Again and Smart Fibersorting are collaborating in commercializing Fibersort.
The Hong Kong Research Institute of Textiles and Apparel (HKRITA): Colour sorting is automatically performed by SCARA robot that uses Advanced Vision Algorithms. The technology can be used to sort up to ten colours and place them into different containers. The Automated Guided Vehicles (AGV) will then transport the containers of different colour to a smart storage system. The smart storage system can retrieve the corresponding number of containers automatically whenever an order is received for further processing.
Innovations in separating fibre types
Many fabrics in the market are in fact blends of two or more different fibre types tightly woven together. Polycotton, the most common blended fibre, combines cotton and polyester. To recycle both the polyester and the cotton components of this blend, the recycling process must first separate them. This is not easy mechanically, but can be achieved chemically. However, there is still much research and testing to be completed before the full-scale launch. If the technology to separate different fibre types is viable, recyclers could buy a higher volume of feedstock since they do not have to rely exclusively on 100% cotton/polyester. Here are a few examples of innovations in this area:
Worn Again (UK): Propriety dissolution process can selectively target and dissolve the polymers it is after (PET and cellulose from cotton). The feedstock can have up to 20% of other fibre i.e. wool, nylon, elastane etc. Contaminants such as dyes, chemicals are also removed in the process.
HKRITA (Hong Kong): HKRITA has developed a chemical hydrothermal treatment that uses only heat, water and less than 5% of biodegradable green chemicals to selectively decompose cotton into cellulose powders, thus enabling the separation of the polyester fibres from the blends. A recovery rate of over 98% of polyester fibres can be achieved in 0.5-2 hours.
CARBIOS (France): CARBIOS has developed an innovative approach to use enzymes to enable specific depolymerization of a single polymer (e.g. PET) contained in various plastics to be recycled. At the end of this stage, the monomers resulting from the depolymerization process will be purified, with the objective to repolymerize them.
Shufen Lee has been residing in Toronto since 2007 and holds a BMath at the University of Waterloo.
She is currently an independent research collaborator with Asiaimportal (HK) Limited.