Cotton regenerated
Cellulose-dissolving techniques derived from viscose production are being applied to cotton waste as an alternative to mechanical cotton recycling. These processes promise to close the loop by regenerating cotton-rich used and unused textile and clothing waste into new manmade cellulosic fibres.
A long-standing practice in the industry, the mechanical recycling of cotton can be a good solution for some types of waste, but not all. The process of shredding fabrics and clothes back to fibre form results in short, low-grade cotton fibres having limited use. Dissolving cotton down to its cellulose form, a chemical recycling technique, changes the nature of the fibre as it is turned into a viscose, lyocell or any other of the manmade cellulosic fibres, but it regenerates waste into high quality fibres. Whatever the method chosen, be they re-shredded or regenerated, at the current state of research and development, these fibres are used in small proportions to make new recycled yarns, and their relative advantages with regards to energy use remains a matter of debate.The debate that is not questioned is the need to find ways to reduce and reuse the waste that the fashion industry generates in large volumes. All the more so as stocks of unsold garments pile up in factories and at retailers in a covid-19-ridden world, adding to consumers’ stacks of unwanted clothing.
In high cotton
Whether in R&D or already on the market, as is Lenzing’s Refibra, the recycling processes that turn used cotton into new cellulose pulp require a specific type of input material having a high cotton content of around 95%. While post-industrial cotton waste can be relatively easily to collect, harvesting the natural fibre from post-consumer waste calls on meticulous and rigorous sorting and grading. Composition labels are often lacking or may be outright inaccurate. Automated systems, such as the Fibresort, which optically scans fibres to identify composition, are recommended. Bales of used clothing labelled pure cotton can have up to 20% to 40% polyester content, as Stacy Flynn, co-founder and CEO of Evrnu, tells Inside Denim.
Many of the dissolving techniques in development have for this reason first started with pre-consumer waste, scraps and offcuts from factory floors, leftover bolts of fabric and such, before tackling the trickier task of processing post-consumer textiles. This was the case for Lenzing when it launched its Refibra technology in 2017. Since then, the Austrian manmade cellulosic fibre manufacturer has added used clothes to its mix. “Over the past three years we have increased the recycled pulp content in Refibra from 20% to 30% and we have added post-consumer waste. This is just the beginning as our goal is to reach 50% post-consumer waste by 2024 and we continue to develop technology for fibre separation,” says Tricia Carey, the company’s global head of denim.
Indian manmade cellulosic fibre maker Birla recently introduced its first viscose fibre made from 20% unused industrial fabric. Its goal is to incorporate 50% post-industrial and post-consumer waste.
The material that Swedish company Re:newcell can recycle into its regenerated cellulosic fibre Circulose places the bar at 98% cotton content. This is the novel material that Levi’s is using to make two jean styles as part of its Wellthread collection, which will be in stores this autumn.
Infinited Fiber Company (IFC), based in Finland, may be developing the most tolerant process, as it says it can recycle textiles with only 80% cotton or cellulose content, including cardboard and even dust. This brings to mind the raw material used to produce cupro, a manmade cellulosic fibre manufactured by Asahi Kasei, which is made from cotton linters, a cotton processing waste product. This fibre was invented in the late 19th century and is considered one of the finest of the ‘viscose’ family.
A plethora of players
Infinited Fiber Company (IFC) organised a remote open house event this June to present its cellulose recycling process. It starts with the shredding of used textiles of any colour but containing 80% cellulose, as described by Kirsi Terho, key account director. Various chemicals are used to remove contaminants, including polyester sewing threads and metals, and washing removes remaining impurities such as elastane. After drying, the resulting material is mainly cellulose. It is then transferred to a former viscose factory that closed in 2013, but is now the company’s pilot plant. Here it tests its dissolving process that uses an alkaline urea-based solvent instead of carbon disulphide to make an ammonium carbamate cellulose that can be wet-spun into 1.3 dtex fibres. This process was chosen, she points out, because its chemistry is not toxic and the resulting fibre has a high dye uptake.
When it will come to market, Ms Terho says IFC’s fibre will be labelled rayon in the United States, but it is unclear what it will be called in Europe where this term is no longer in use. “The fibre is closer to a viscose than to a lyocell, and it has more of a cotton hand feel,” she says. Looking ahead, Petri Alava, IFC CEO and co-founder, says production capacity will be trebled to 450 tonnes. He would like to see a full-scale industrial plant built in 2021 and producing fibres in 2022, anywhere in the world. The fibre is being tested by several mills, including Artistic Milliners in Pakistan and Arvind in India.
Re:newcell’s Circulose is also being tested by denim mills (Arvind, Isko, Soorty and Artistic Fabric Mills) with a fibre containing recycled material from unsold stocks of jeans or denim fabrics. The process developed by the company is being tested by Chinese manmade cellulosic fibre producer Sanyou, incorporating 50% recycled waste for its recycled fibre labelled ReVisco.
In February this year, Sanyou began conducting tests on OnceMore, another cotton-to-cellulose recycling process developed by Swedish pulp specialist Södra. Its first iterations are said to contain 3% post-consumption cotton textiles. Sanyou says it plans to raise the recycled content to 20% post-consumption textile fibre “as soon as possible”.
Increasing recycled content
Evrnu’s goal is to bring to market a cotton-based regenerated cellulosic fibre made from 100% post-industrial and post-consumer waste under its NuCycl brand. The Seattle-based R&D company is working on several processes with various input materials as well as sorting technologies. Its cotton-to-cellulose regeneration technology requires waste having a minimum cotton content of 95%, which the company says can only be obtained using an automated fibre-scanning system, currently in test in its pilot plant. “At full capacity, the technology will be able to sort eight tonnes per hour,” says Stacy Flynn. “High-speed sorting is critical for chemical recycling. It is more reliable and much faster than manual sorting that treats on average one tonne per hour.” The company is training collectors and sorters to automate their processes. “Our goal is not just to deliver pulp that works, but pulp that works more efficiently in the fibre producing process to preserve the alpha cotton content, so that it can be broken down again in the future.”
The company says it is working with several manmade cellulosic fibre manufacturers producing either viscose, lyocell, cupro or acetate. “A lot of customisation is involved in developing the right recipe for each process,” says Ms Flynn. These companies have begun incorporating recycled content in incremental stages. “They will work their way up, blending 10% cotton waste with 90% wood pulp, then 20% and 80%. Depending on their process, each fibre producer will have a different comfort level with regards to recycled content,” she says. Evrnu will not manufacture the fibre itself, but seeks rather “to work out all manufacturing kinks” and then license its IP. Once the technology is fully operational, in the next 12 to 18 months, the company will then move on to its other projects, which include recycling polycotton and depolymerising polyester. All of these future ‘regenerated’ materials will be branded NuCycl, on condition they are made from 100% recycled content. A QR code on finished products will allow consumers to see the whole process, and even request a return label to send the product back when no longer in use. The company has partnerships with Levi Strauss, Target, adidas and Stella McCartney, and these brands will in all probability be the first ones to bring these new fibres to market.
A number of companies, including Worn Again in the UK and Blocktexx in Australia, are developing techniques to separate polycotton blends and extract cellulose powder from the cotton content to make manmade cellulosic fibres.
Fixing cotton
Natural Fiber Welding (NFW), based in Peoria, Illinois, is also working on a process that turns waste cotton into a cellulosic fibre, but the company is using ionic liquids to do this, a category of solvents that melt below 100°C. Dr Luke Haverhals, company founder and CEO, has developed a specific type of ionic liquid that “unhooks” the bonds in cellulose. “Instead of fully dissolving the cotton, our Clarus process retains the original order and structure of cotton,” he tells Inside Denim. The process can furthermore “tune” the degree of “welding” to adjust the smoothness or texture of a cotton fibre, as it can also make it waterproof, stronger or dry faster. Dyes and finishes can be added during the process as well, he says.
NFW’s technology can also be used to improve the quality and performance of recycled cotton or lower-grade short fibre cotton. On other natural fibres, such as raw or waste silk, it can similarly “fix” the yarns to make higher grade silk, he says. The company is currently focusing on cotton, because of its abundance, and is conducting tests on post-industrial cotton waste. At scale, Dr Haverhals believes the “upcycled” cotton fibres could be in the same price range as extra-long Pima cotton, “while adding more features and more performance”. The Ralph Lauren Corporation has recently made a minority investment in the start-up as part of its strategy to increase its use of recycled post-consumer cotton and implement zero-waste principles.
The adoption of these new regenerated fibres will require that brands and retailers manifest interest, or better yet be willing to invest in these technologies as further research and development is needed, in the technologies themselves and in the collecting, sorting and grading processes prior to fibre manufacturing. These added costs that all recycled fibres face make it difficult to compete with virgin fibres, be they traditional manmade cellulosic fibres or cotton. Some believe that cotton or wood growers should integrate externalities that are currently not factored in, such as water usage or soil degradation, and shift to regenerative farming techniques to level the playing field. If all materials become regenerative in nature, as these cotton-based cellulosic materials say they are, the fibres of the future would all contribute to a healthier planet and industry.
Lenzing’s Refibra Technology upcycles cotton waste to make a soft, stronger and circular fibre that was featured in a capsule collection designed by Juan Carlos Gordillo with fabrics from Tejidos Royo, Spain.
PHOTO: Richard Cordero for Lenzing
