Unique Hydrothermal Processing Technology for Recycling Textiles

Gerard Ortiz

A Virginia, United States-based clean technology startup is applying its unique hydrothermal processing technology to treat previously hard-to-recycle textiles made out of blends of polyester and cotton. Circ’s system recovers as-good-as-virgin materials from waste clothing and could play an important role in establishing a circular economy in the sector.

hydrothermal processing, recycled textile blends, recycled textiles

Image Credit: NicoleTaklaPhotography/Shutterstock.com

Fashion’s Environmental Impact

Around the world, humans buy, wear, use, and discard clothing at an increasingly fast rate. As the world population continues to grow, so too does the demand for textiles to dress it.

As a ubiquitous industry, clothing manufacturing will always have a relatively large impact on the world’s ecosystems. But the advent of so-called “fast fashion” in the last few decades – cheap clothing made by low-paid workers in typically poor conditions in the global south – has increased the scale and impact of the sector significantly.

Clothing manufacturing doubled between 2000 and 2015. The low cost of these items made them seem disposable, and consumers in wealthy countries treated them as such. On average, everybody in Europe throws away about 15 kg (33 lb) of textiles each year, recycling less than a fifth of this. This has resulted in a surplus of waste textile material filling up landfill sites, as well as increased demand for cheap clothes.

Producing clothes consumes energy and natural resources like water (100 bn m3 of which is used by the industry each year, or 4{05995459f63506108ab777298873a64e11d6b9d8e449f5580a59254103ec4a63} of the world’s total freshwater withdrawal). The more clothes we produce, the more of these precious resources we consume.

These issues have recently received significant public attention, and the industry is moving toward more sustainable practices as a result. The European Union will require textile waste to be collected separately from other waste forms by 2025, in line with requirements for paper and glass. Recycled polyester made up 11{05995459f63506108ab777298873a64e11d6b9d8e449f5580a59254103ec4a63} of the total market in 2010, but increased to 15{05995459f63506108ab777298873a64e11d6b9d8e449f5580a59254103ec4a63} by 2020.

Circ’s Technology Means We Can Recycle More Clothing Ever

Although more clothing is being recycled today, there remains an upper limit to how much can be viably repurposed into usable material. This is because it has typically been too hard to recycle blended fabrics – those that contain a combination of materials or composite threads.

Circ, a startup that initially sought out technology solutions to biofuel production, is applying a technical solution that means blended textiles can be recycled at scale to produce as-good-as-virgin raw materials for the textile industry.

The company’s unique hydrothermal process was repurposed from biofuel production to textiles recycling. The company is operating a pilot industrial facility that has the capacity to recycle a few tonnes of textiles every day. It says it will open its first full-scaled factory in 2025, capable of processing over 1,000 tonnes of waste clothing each week. By 2030, the company’s stated ambition is to recycle 10 billion individual garments, or 10{05995459f63506108ab777298873a64e11d6b9d8e449f5580a59254103ec4a63} of the global clothing market.

These ambitions are backed by investors like Bill Gates’s Breakthrough Energy Ventures, retailer Zara’s parent company Inditex, and clothing brand Patagonia’s venture capital fund Tin Shed Ventures. It has raised €38 million in Series A and Series B funding to date.

How Does Circ Recycle Poly-Cotton Blends?

At present, there are no commercially available recycling methods that can process poly-cotton blended textiles and return materials fit for new clothing manufacturing. Although breaking down pure polyester (PET) for recycling is a well-understood process, recycling poly-cotton blends without damaging one or the other material has proved challenging.

Circ’s proprietary system uses pressure, hot water, and solvents (that the company claims are environmentally friendly) to separate polyester from cotton without damaging either discrete material. This use of hot water and pressure is known as hydrothermal processing.

The technology platform is flexible and can work with a range of waste materials including pure cotton and pure polyester.

The hot water’s pH is raised, which means that polyester liquefies quickly and breaks into monomers of terephthalic acid (PTA) and ethylene glycol (EG). At the output end of the system, a liquid stream contains only PTA and EG while a separated solid stream contains only cotton. PTA and EG are recombined to make virgin PET plastic. The cotton is dissolved in a solvent that can be pressed to create lyocell fibers, a cotton-like fiber.

Circ’s main innovation has been to rapidly depolymerize the polyester in blended textiles so that the cotton can be recovered and used before it is damaged. The company claims it can recover almost 90{05995459f63506108ab777298873a64e11d6b9d8e449f5580a59254103ec4a63} of the fabric that goes into the process.

Other Applications for Hydrothermal Processing

Hot water and pressure have a number of other clean technology applications as well.

Mura Technology, for example, is nearing completion of its first commercial-scale facility for recycling all sorts of plastic waste together to recover usable monomers in Teesside, UK. The company says that its hydrothermal system can recycle types of plastic waste that we cannot currently process at scale.

Hydrothermal carbonization (HTC) processes have also been used to convert cotton textile waste into energy sources in recent research. In one study, Iron(III) chloride (FeCl3) was used to catalyze the dehydration and decarboxylation of cotton in a hydrothermal process to produce hydrochars. Another group of researchers has employed a similar process with surfactants acting as catalysts in the HTC reaction to also make clean solid fuel from cotton textile waste.

Next Steps for Circ

Circ is now gearing up to launch its first factory (of many, according to the company) in 2025. Its major remaining challenges are market-based rather than technological. It must find industrial customers for its recycled raw textile materials, and investor brands Zara and Patagonia have not yet confirmed that they will be customers themselves.

The company must also work with actors throughout the clothes ecosystem (including manufacturing, brands, retailers, waste collectors, waste sorters, and consumers) to establish a circular economy for textiles.

More from AZoM: A to Z of Sustainable Textiles

References and Further Reading

Threading together the future of circular Fashion. [Online] Circ. Available at: https://circ.earth (Accessed on 15 December 2022).

“Ground-breaking” technology to recycle all forms of plastic waste. (2021) [Online] Circular. Available at: https://www.circularonline.co.uk/news/ground-breaking-technology-to-recycle-all-forms-of-plastic-waste/ (Accessed on 15 December 2022).

Hughes, M. (2022). px Group to operate Wilton plant for ReNew ELP. [Online] Northern Echo. Available at: https://www.thenorthernecho.co.uk/news/20760241.px-deal/ (Accessed on 15 December 2022).

Factsheet on Textiles. (2022) [Online] European Commission. Available at: https://ec.europa.eu/commission/presscorner/detail/en/fs_22_2017 (Accessed on 15 December 2022).

Hedrich, S., et al (2022). Scaling textile recycling in Europe—turning waste into value. [Online] McKinsey & Company. Available at: https://www.mckinsey.com/industries/retail/our-insights/scaling-textile-recycling-in-europe-turning-waste-into-value (Accessed on 15 December 2022).

Mount, M. (2022). Polyester-cotton blends are cheap, long lasting—and account for half of textile waste. A Bill Gates-backed startup has invented a way to recycle them into new threads. [Online] Fortune. Available at: https://fortune.com/2022/08/16/bill-gates-circ-startup-polycotton-textile-recycling/ (Accessed on 15 December 2022).

Preferred Fiber & Materials. Market Report 2021. (2021) [Online] Textile Exchange. Available at: https://textileexchange.org/app/uploads/2021/08/Textile-Exchange_Preferred-Fiber-and-Materials-Market-Report_2021.pdf (Accessed on 15 December 2022).

Qi, R., et al (2021). Clean solid fuel produced from cotton textiles waste through hydrothermal carbonization with FeCl3: Upgrading the fuel quality and combustion characteristics. doi.org/10.1016/j.energy.2020.118926.

Xu, Z., et al (2021). Conversion of cotton textile waste to clean solid fuel via surfactant-assisted hydrothermal carbonization: Mechanisms and combustion behaviors. Bioresource Technology. doi.org/10.1016/j.biortech.2020.124450.

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

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