Cellulose technology enables swift scaling up of cotton recycling enterprise
Ethanol production was the aim when two KTH Royal Institute of Technology professors first developed their method for breaking down plant cellulose about 10 years ago. Now the technology has enabled the two researchers to become the clothing industry’s latest change agents.
Equipped with new methods for disintegrating and reconstituting cotton, Mikael Lindström and Gunnar Henriksson have become key figures in the start-up, Re:newcell , which reclaims cotton on an unprecedented scale – producing about 7,000 tons of material annually for suppliers to the global fashion industry.
Their material, Circulose, which is 100 percent recycled cellulose, will be on the market in March, as part of H&M’s Conscious Collection. Meanwhile, the new operation is preparing to supersize itself.
Recovered denim is popping up more often in retail, in response to a growing awareness about waste and the intensive consumption of resources needed to produce virgin cotton fabric. This modest market has been fed by mechanical recycling technology, which literally consists of tearing up old material and then reconstituting it for another cycle of production.
But this method results in material that suffers in durability – the shortened fibers are difficult to spin and it must be blended with virgin cotton. That’s why about five years ago Lindström received a call from an entrepreneur driving back to Stockholm from a meeting with Swedish clothing brands. “Malcolm Norlin, the former owner of a wood pulp biorefinery facility in Domsjö, was sitting in a car with Johan Sundblad, a representative of the Swedish brands, and they asked, ‘Is there any research at KTH for chemical recycling of textiles?’”
The seeds of an enterprise were thus laid, as Lindström referred back to a method he and colleagues Henriksson and Yan Wang had developed for disintegrating the impermeable fibrils that cellulose consists of – without damaging them, and without relying on expensive and environmentally unsustainable chemicals.
Lindstrom says the basic science at the root of ethanol production works as well for breaking down cotton fibers. “You can break cellulose down and ferment it into alcohol,” he says, “You can also change the properties of cellulose.”
Cellulose is the building block of plant cell walls – polysaccharide chains of glucose units that are arranged in impermeable crystalline structures known as fibrils. Cellulose excludes water almost entirely, but less ordered chains have no crystalline structure to protect them, and as a result they are more susceptible to dissolution.
But it had been established earlier that polysaccharide chains can be disordered with cold caustic soda. The team’s method took hold of that concept and refined it into a scalable, industrial method.
With the support of KTH Innovation, Lindstrom and Henriksson formed a company with investors and refined their methods, while developing technology to reassemble the cotton fibrils into fiber that can be ultimately be spun into new fabric.
“What’s unique here in Sweden is the deep knowledge of cellulose that we have, and then our experience of building large mills for pulp technology,” Lindström says.
The company built up its pilot plant in Kristinehamn in 2017, branded itself, and scaled up its production from kilogram to multi-tonscale within a few years. With the capacity to meet large orders, and its partnership with H&M, the company now is planning future plants around the world.
“It’s really an interesting case in how you can scale something up.”
Increased degradability of cellulose by dissolution in cold alkali
Wang, Y., Lindström, M.E., Henriksson, G.
Profile pages: Mikael Lindström and Gunnar Henriksson