The fashion industry is on a mission to find a more circular path for textile waste, but one of the challenges standing in recycling’s way has been blended materials.
Processing post-consumer clothing that has more than a single fiber type is complicated. As a result, textile waste is often sent to landfills or relegated to purposes other than apparel.
Research conducted by the Fraunhofer Institute for Applied Polymer Research IAP on behalf of recycling technology firm Re:newcell points to a potential solution to this problem. The chemists at the institute adapted a cellulose fiber production process so that recycled cotton could be used as a feedstock in place of wood.
Typically, cellulosic materials such as viscose, lyocell and modal are made by first turning wood into pulp. This pulp is then dissolved through a chemical process, and the resulting solution is sent through a spinneret to create fibers.
Re:renewcell, which produces 7,000 tons of Circulose-branded pulp out of cellulose materials per year at its plant in Kristinehamn, Sweden, asked the scientists to test whether a sheet of its recycled cotton could be made into a viscose rayon.
Even though Re:newcell’s recycling process separates cellulose content from other materials, such as polyester, the researchers had to devise a method for chemically separating the fibers. “We were able to extract the foreign fibers from the pulp by setting the right parameters for both the dissolving and spinning processes, for example, with effective filtration stages,” said André Lehmann, head of the fiber technology department at Fraunhofer IAP.
The Fraunhofer IAP team created a multi-kilometer-long filament yarn that contains 100 percent pure cellulose material, making it biodegradable.
“The starter material for viscose rayon fibers has been wood-based cellulose,” Lehmann said. “By optimizing the separating processes and intensifying the filtration of foreign fibers in the spinning process, we will eventually be able to establish recycled natural cotton fiber as a serious alternative source of cellulose and base raw material.”
One hurdle on the path to wider recycling adoption has been quality concerns. Researchers say this yarn can be used in mass textile manufacturing, and it has properties in line with commercial viscose rayon.
What differentiates this development for Anthony Schiavo, senior analyst at LuxResearch, is the fact that it is able to drop into the existing viscose rayon production process. “A lot of the activity that we’ve seen in the textile recycling space in general, as well as materials development and recycled materials a bit more broadly, doesn’t really take into consideration ultimately how that material is going to end up being used,” he told Sourcing Journal. “And as a result, it tends to run into a lot of challenges.”
Schiavo has also seen interest from viscose producers for recycled rayon solutions, which hadn’t been as available in the past. “The existing viscose players are very much going to co-opt this kind of technology,” he said, adding that it is less of a threat to viscose manufacturers than it is to cotton producers.
However, about 20 to 25 million tons of cotton is produced per year, so recycled materials are unlikely to fully displace cotton growers. “The global fiber market is slightly bigger than 100 million tons per year and will be continuous growing,” Lehmann told Sourcing Journal. “That growth will be partially covered by recycled materials, but virgin raw material will be by far the dominating source for creating new textiles.”
Lehmann does see the recycled cotton viscose process as scalable, since approximately 5 million tons of viscose is produced each year.
While production-level technology seems to be less of an obstacle, scaling up cotton recycling will likely come down to sourcing. Schiavo noted that companies that have consumer-facing production, such as Aditya Birla, may be better equipped to add waste collection to their operations than those that solely act as fiber suppliers.
“I think the challenge for these viscose rayon existing players is to build the infrastructure to actually get enough waste,” said Anthony. “That, to me, is the real bottleneck.”