The stretch that breaks recycling

Stretch has become so normal that it’s almost invisible. It’s in the waistband that doesn’t dig in, the sports top that keeps its shape, the denim that moves with you, the workwear that still feels wearable at the end of a long day. A few percent of elastane can turn a garment from “fine” into the one you reach for again and again. It’s also one of the quiet reasons textile recycling so often stalls.

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Because the moment you add stretch, you’ve stopped making a single material and started making a system. A cotton–elastane blend (or any cellulose–elastane blend) isn’t just “two fibres together.” It’s two fibres chosen precisely because they behave differently (one giving structure, one giving resilience) and then bound into a fabric designed to survive sweat, friction, heat, detergent and time. Recycling asks them to do the opposite.

This is where the gap opens between the idea of “recyclable” and the reality of a worn, washed, dyed, finished garment. In principle, cellulose fibres can be recycled into new cellulose-based materials. In practice, a small amount of elastane can complicate the entire route, because you can’t simply wish it away. If it remains in the stream, it can interfere with processing and the quality of what comes out the other side.

That’s why BioSusTex puts blended textiles, specifically post-consumer cellulose blends containing elastane, at the centre of its circularity work. Not as an edge case, but as the test that matters.

What makes the project’s approach feel grounded is that it doesn’t treat recycling as one magic step. It treats it as a chain of problems that have to be solved in the right order.

Before you can talk about fibre-to-fibre recycling, you have to deal with what real garments carry: dyes, finishes, impurities and the “unhelpful” fibres in the blend. BioSusTex frames this as a pre-processing challenge for post-consumer textiles, i.e. developing methods to remove elastane from cellulose blends, and pairing that with colour stripping so the cellulose fraction can be recycled into higher-quality outputs.

In a lab, you can prove concepts with clean swatches: known composition, known dye load, no unknown finishes, no wear. It’s useful science, but it’s not the waste stream. Real garments arrive with variation. They arrive with the things that made them desirable in the first place. If a recycling route only works when the input is “perfect,” it won’t become normal.

BioSusTex is explicit that it’s working on post-consumer textiles and designing its recycling route to cope with that messy reality, starting by targeting elastane removal using selective processes and building from there.

Closed-loop doesn’t just mean that you can recover something. It means the recovered cellulose isn’t merely a technical success; it’s a usable one. It has to be clean enough and consistent enough to become a new fibre with performance people will accept, and it has to do that repeatedly. The project sets its ambition around fibre-to-fibre outcomes for cellulose, which is a higher bar than downcycling into lower-grade applications.

This matters because textile recycling has a well-known trap: you can recycle almost anything if you’re willing to accept a big drop in quality. Shred it, blend it, turn it into insulation or stuffing. That has value, but it’s not the kind of loop that meaningfully reduces the demand for new fibres at scale. The hard work is keeping value in the system, i.e. keeping fibre quality high enough that “recycled” can re-enter the same kinds of products.

There’s also a tension here that’s worth saying plainly: blends exist for a reason. Elastane is often part of what makes clothing last longer in use: better fit, better comfort, less “bagging out,” more willingness to keep wearing the garment. If recyclability is treated as the only design goal, it’s easy to end up trading away features that reduce replacement and overconsumption in the first place. The challenge isn’t “stretch or circularity.” It’s whether we can build systems where textiles don’t have to choose between being good to wear and possible to recover.

That’s the logic running through the BioSusTex project: tackle the bottleneck that blocks circularity in real wardrobes, and do it in a way that aims for industrial relevance rather than lab perfection, by designing pre-processing (elastane removal, colour stripping) as part of a route to high-quality cellulose recycling.

Stretch won because it solved everyday problems brilliantly. Now circularity has to catch up and solve the problem stretch creates at end-of-life, not by asking people to stop wanting comfort, but by making “second life” as intentionally engineered as the first.