Glycolysis Method Breaks Down Mixed Textiles for Recycling | Research

A new chemical recycling strategy breaks down polyester and spandex into usable monomers while keeping cotton and nylon intact and ready for reuse. The method could provide a way to increase the amount of textile waste being recycled while minimizing the need for sorting and separation.

About 100 billion items of clothing are sold each year. Since the turn of the century, “fast fashion” trends have increased textile production. However, the production and short lifespan of cheap clothing items has a serious impact on the environment.

“Fast fashion increases waste because clothes are thrown away more quickly, contributing to an estimated 92 million tons of textile waste globally each year,” says Erha Andini from the University of Delaware in the US.

Currently, less than 1% of this waste is recycled, with most going to landfill or being incinerated. That’s because while there are technologies for mechanical and chemical recycling, most clothes contain complex mixtures of fibres and additives that are notoriously difficult to separate and sort. “Separating different fabrics requires unpicking seams that are designed to be durable,” says Alice Payne, a fashion and textile expert at RMIT University in Australia. “Solving these challenges requires significant labour and logistics, and the payoff is relatively small,” she adds.

Now, Andini and her colleagues in the US have shown how a simple and fast chemical recycling method can be applied to the most common components in mixed textiles. The technique uses microwave-assisted glycolysis with a zinc oxide catalyst to separate polyester, cotton, nylon and spandex in mixed waste streams.

The team first applied the catalytic conditions to pure samples of polyester and cotton, because these are the best-selling fibers on the market. The researchers found that the polyester degraded into monomers, 90% of which was bis(2-hydroxyethyl)terephthalate (BHET), a useful component of yarns, resins and fibers. The cotton experienced a mass loss of about 8% but was otherwise unaffected. The team then applied the same technique to T-shirts made from a 50:50 blend of polyester and cotton at different temperatures and times. Higher temperatures accelerated the degradation of the polyester, with complete depolymerization achieved at 210°C in less than 15 minutes.

Because real textile waste is diverse and contains many additives and contaminants, the team then tested the process on textiles containing different dyes and finishes. This reduced the efficiency of BHET, suggesting that the additives may be hindering the performance of the zinc oxide catalyst.

Finally, the team looked at blends containing other common textile fibers. When the researchers treated a 90% nylon/10% spandex blend, the nylon remained structurally unchanged. But the spandex broke down into monomers, including 4,4′-methylenedianiline, a key component of polyurethane foam and glass-fiber plastics.

By applying the process to blends containing polyester, cotton, spandex and nylon, the team managed to depolymerize both the polyester and spandex while separating the intact cotton and nylon.

“We need more research like this that acknowledges the inherent complexity of modern textiles and develops valorisation processes to regain their utility,” says James Clark, an expert in green chemistry at the University of York in the U.K. “Combining known methods in ways that aren’t currently being used is key, because this approach should be more attractive to industry than creating new methods,” he adds.

“The scalability of the microwave-assisted glycolysis process for depolymerization of blended textiles is promising, but there are challenges,” says Andini. “These include managing the impact of dyes and finishes, ensuring economic viability, and optimizing reaction conditions for different textile compositions,” he adds.

The team suggests that an improved version of their process could enable up to 88% of the world’s textiles to be recycled. But Clark believes the real hurdle will be widespread adoption of such methods. “Once these methods are proven, more will emerge, and we could move towards a scenario where the valorisation of waste textiles at a material and molecular level is built into the textile market,” he says.