Textile recycling is one of the primary solutions identified to address the textile-waste problem, apart from avoiding waste generation and extending the life of garments. A group of recycling technologies can potentially recycle 70% of Europe’s textile waste into fibers for closed-loop applications.
With the potential to reduce the carbon footprint of certain fiber types by up to 90% compared to virgin material counterparts, lower land and water usage, and chemical pollution, the environmental incentives to pursue textile recycling are substantial.
Recycling technologies differ in several ways, including their energy efficiency and ability to return to or maintain virgin quality. In general, however, the equally desirable traits of returning to virgin quality while remaining energy-efficient are inversely related. As a result, there is a trade-off between recycling the textile waste in an energy-efficient (cost-effective) process and producing virgin-quality output.
This post presents four recycling technologies available in textile waste management.
1. Mechanical recycling
Mechanical recycling converts textiles into usable fibers using physical forces such as cutting and grinding. It is a low-energy, low-cost recycling method that has been commercially proven. Under the “what goes in, comes out” principle, all fiber types are addressable, meaning that the textile waste’s fiber composition will become the fiber composition of the recycled fiber. There are “open-loop” (primarily downcycling) and “closed-loop” applications in mechanical recycling. Open-loop applications (such as cleaning rags, shoddy fibers, and padding) are currently the most mature markets for mechanical recycling, with a wide range of end uses. Automotive, furniture stuffing, wall or floor coverings, and apparel applications are a few examples.
This technology currently faces the challenge of recycled fiber quality degradation, with a fiber-length reduction of up to 30 to 40%, limiting closed-loop applications. However, mixing recycled, shorter fibers with virgin fibers results in higher quality. This is already present in several existing products on the market today. Furthermore, an emerging “soft” mechanical recycling technology can achieve a fiber-length reduction of only 10 to 15%, as well as other innovations to improve mechanical recycling that can overcome this problem. Purfi and Recover are two companies looking into higher-quality mechanical recycling and other innovative solutions.
2. Thermo-mechanical recycling
Pressure and heat are combined in thermo-mechanical recycling to melt synthetic textiles (polyester and polyamide) and recover polymers. Natural fibers (such as cotton or wool) and MMCF cannot be processed using this technology (such as viscose). It consumes less energy and may result in less quality degradation than most mechanical recycling technologies. Thermo-mechanical recycling is a mature technology with commercial applications for non-textile waste (such as PET bottles) and a demonstration-scale application for textiles. Textiles face specific technical challenges (for example, viscosity issues with PET), and feedstock requirements are very strict today (more than 99% single or compatible polymers), limiting feedstock availability.
3. Chemical recycling
Chemical recycling encompasses various technologies that use chemical processes to break down fibers to the polymer or monomer level. Back to the “polymer level,” technologies include a pulping process that recycles cotton and MMCF to a pulp similar to dissolving wood pulp (DWP), which can then be used to create MMCF. They also include solvent-based and hydrothermal processes for recycling polyester and polycotton fibers back to PET melt (cellulosic material), which can then be spun into PET polyester fiber. Recycling polyester and polyamide is the focus of technologies that return to the monomer level (for example, methanolysis, glycolysis, hydrolysis, and enzymatic).
These recycling processes necessitate going from the monomer level (for example, mono-ethylene glycol [MEG] and purified terephthalic acid [PTA]) back to the polymer level, such as PET before they can be respun to fibers. Chemical recycling processes use more energy than mechanical recycling but have the distinct advantage of returning to (almost) virgin-quality fibers. Chemical recycling of textiles does not yet exist commercially. Nonetheless, many companies are constructing pilot and commercial plants for cellulosic (such as Lenzing, Renewcell, Södra, and Infinite Fiber) and synthetic (such as Eastman, Erema, Worn Again, Ambercycle, Gr3n, and Circ) recycling.
4. Thermo-chemical recycling
Thermo-chemical recycling generates syngas through the partial oxidation reaction of polymers and is compatible with all types of fibers. This technology, however, is not a closed-loop application for textiles. Methanol, ammonia, synthetic fuels, and oxo-alcohols for plasticizers, adhesives, and construction materials are the primary applications for the recovered virgin-quality syngas. At the commercial scale, thermo-chemical recycling is a core technology; however, this technology requires some adaptation or development to treat textile waste.