Fashion’s Big Bet on Textile Recycling, Explained

Every year, the global fashion industry churns out billions of jeans, T-shirts, dresses and sneakers. And every year, as consumers replace old trends with new, more clothes wind up in the global waste system.

Globally, approximately 92 million tonnes of textiles are thrown away every year — roughly triple the total amount of waste Canada generates annually. Most end up incinerated or in landfills. The staggering volumes have attracted the attention of regulators, with policymakers in China, the EU and US states like California demanding the industry do more to clean up the mess.

The result has been a big push to promote textile recycling, a solution brands have presented as a way to both curb their carbon emissions and tackle the industry’s waste issues. The problem? Textile recycling at any kind of scale doesn’t really exist yet.

How does textile recycling work today?

Today, only a tiny fraction of the world’s textiles are recycled back into new materials. That’s partly because of technology and partly because of the fashion industry’s janky infrastructure.

Textile recycling involves undoing the complex and detailed series of steps that go into making clothing. The process starts with getting unwanted products back from consumers. That’s easier said than done; most countries don’t collect textile waste separately, or have only recently started to do so.

Once they come back, clothes then have to be sorted and prepped, a manual and therefore expensive process. Most recycling techniques can only handle very specific types of material, which means garments that aren’t up to spec need to be sifted out. Zippers, buttons and fasteners all need to be removed before recycling. Unidentifiable and invisible challenges also lurk on the surface of fabrics in the form of dyes, coatings and treatments designed to provide functionality like water, crease and stain resistance.

Partly as a result of such barriers, today textile recycling is “almost non-existent,” said textile expert Lutz Walter. In the fashion industry, recycled cotton has a market share of around 1 percent or less and the 12 percent or so of polyester supply that’s recycled comes from plastic bottles, not old clothes, he added.

To the extent that textiles are currently being recycled, it’s mostly through mechanical recycling, a well-established process that involves shredding unwanted old materials into fibres to be spun back into new fabrics. The process is relatively cheap, but the end product is also generally lower quality. Chopping fibres up shortens them, making them more fragile and prone to breaking. The process doesn’t work on polyester — fashion’s most widely used material — because instead of shredding, the plastic-based material just turns to melted globs.

Cotton can typically only undergo one round of mechanical recycling, experts say, after which the cotton fibres are too short to be remade into textiles. The quality of the cotton matters, too. Cotton textiles from factories, such as cut-offs from new garments, are more desirable than cotton textiles from consumers, which have already undergone unknown amounts of washing and wear-and-tear.

New lower-impact techniques that tear cotton at slower speeds to keep the fibres longer are being developed, but there are still serious limitations to this approach.

The holy grail for the industry, advocates say, is chemical recycling. It’s a much more nascent approach, but if perfected, it holds out the promise to make the fashion industry truly circular, allowing old clothes to be recycled back into good quality new materials again and again, according to its backers.

What is chemical recycling and how does it work?

Chemical recycling is the process of breaking down textiles using chemical solvents, often helped along by heat and catalysts like enzymes. The exact process varies from start-up to start-up, depending on the proprietary “recipe” each innovator has developed and the materials they aim to recycle.

The plastic packaging sector has employed similar techniques for years, but the application is relatively new for textiles, with technologies still jockeying to prove they can commercialise and scale.

Innovators tend to fall into two camps, those that focus on cotton textiles and those that focus on polyester textiles — the two most commonly used materials in the fashion industry. A select few accept blends, a more complex proposition because the process for recycling the two materials is quite different and an additional step is required to separate them before they can be independently broken down.

To date, fashion’s highest-profile efforts to bring chemical recycling to scale have focused on cotton. Circulose, the Swedish recycler previously known as Renewcell, had built a plant capable of processing thousands of tonnes of cotton before running into financial difficulties and going bankrupt last year. While the company has had to reset, it remains one of the only textile-to-textile recycling companies to have reached industrial scale.

The process for chemically recycling cotton relies on acids or bases to relax the bonds between fibres, allowing them to be pulled apart and formed into a pulpy mixture of cellulose — the material that forms cell walls in plants and the fibres in cotton. Other chemicals can be used to strip dyes. Once dried, what’s left is a pulp of recycled cellulose that can be used to make viscose or lyocell, just like virgin cellulose harvested from trees.

The process of breaking down polyester is more intensive than recycling natural fibres. This is by design. Polyester textiles “are, on purpose, very stable,” said Lars Krause, chemical recycling expert at the renewable carbon think tank, nova-Institut. That means more energy is required to break them down. This chemical back-tracking, known as depolymerisation, can be achieved using a number of different methods, each with their own pros and cons.

Hydrolysis; water-based depolymerisation

Many innovators, such as Inditex-backed Circ, French green chemistry business Carbios, and Swiss company GR3N have opted for a water-based approach to depolymerisation, known as hydrolysis. The method is generally considered low cost because water is a cheap solvent, experts say. It also produces the favoured precursor for polyester manufacturers around the world, terephthalic acid.

But hydrolysis is energy-intensive, requiring high heat and pressure to work. That adds emissions to a process that is meant to be green. The end product is also relatively impure, requiring extra steps to remove contaminants before the resulting TPA can be remade into polyester.

Innovators say the temperatures and pressures they use are lower than standard for chemical industries thanks to the proprietary technologies they use. For instance, Carbios uses enzymes from bacteria instead of acids or bases. The output from such enzyme-assisted hydrolysis is cleaner, experts say, because enzymes can be disposed of at the end of the process by simply blasting them with heat. Acids and bases, on the other hand, form a chemical soup that has to be treated to avoid polluting the environment at the end of the process. But enzymatic recycling is also more expensive and the process takes longer because enzymes can be blocked by contaminants.

GR3N uses microwave technology as a catalyst to speed up chemical reactions, reducing energy use, while Circ says it lowers energy consumption with its proprietary process of purifying TPA.

Glycolysis and Methanolysis; alcohol-based depolymerisation

Chemical recyclers can also opt for alcohols instead of water to facilitate depolymerisation. Reju, a textile recycler owned by French engineering company Technip Energies, and H&M-backed Syre both use glycol to break down polyester into the monomer BHET, also known as bis(2-hydroxyethyl) terephthalate. Glycolysis is a well-established process for recycling plastic bottles and is considered low energy compared to hydrolysis and other forms of alcohol-based depolymerisation.

The tricky issue here, experts say, is that BHET is difficult to purify because it is very soluble in water. That means the yield of recycled raw material can be relatively low. The process also requires a catalyst to work at large scale, which adds a mandatory cost to the process. Whereas catalysts speed up the hydrolysis reaction time, the glycolysis reactions can only complete with a catalyst. Companies can opt for a greener metal or an organic catalyst, used by Reju, over toxic solvents.

Finally, companies like textile recycler Eastman, one of the early creators of polyester in the 1950s, have chosen to use methanol instead of glycol to stimulate depolymerisation. The process can handle larger amounts of polyester than hydrolysis and glycolysis, and the purification process is easier, resulting in better quality monomers, experts say. But its output, dimethyl terephthalate, requires one further step to get to the preferred polyester monomer, TPA, increasing the cost of the technique.

A silver bullet solution?

Despite ambitious commitments by brands including Zara, H&M and Puma to transition large chunks of their material mix to recycled content by the end of the decade, getting textile-to-textile recycling to a place where it can service that demand will take substantial investment and concerted work throughout the supply chain.

Whether textile-to-textile recycling lives up to its green promise also depends on exactly what processes and ingredients make it to commercial scale. For instance, plastic packaging recyclers, who pioneered many of the techniques innovators are aiming to bring to the fashion industry, have faced criticism for their use of harsh and toxic solvents and energy-intensive processes. There are lots of complicating factors, not least the fact that there’s no single benchmark for what “good” looks like.

“It’s not like there’s some objective standard that people can use to look at a process and say, ‘Well, this one makes more sense than that one,’” said chemical engineer Paul Martin of the chemical process development consulting firm Spitfire Research. Secondary processes can cause additional problems too. If the output of the recycling process is contaminated, for instance, “you’re really not helping anybody, because it might take as much energy to purify that stuff” as making first-generation TPA,” Martin said.

Textile recyclers say they are committed to developing less polluting processes that deliver on recycling’s environmental promise, rather than causing more pollution. Ultimately, they argue, there’s no other alternative if the industry is to really deal with the mounting piles of unwanted old clothes.

“We can’t mechanically recycle them all and we aren’t single-use products,” said Rachel Kibbe, chief executive of the trade association American Circular Textiles that represents some US-based textile recyclers. “We are durable products that can be used over and over.”