Recycling a fibre usually means making it shorter or breaking it down

Mechanical recycling shreds and respins

The older and cheaper route is mechanical. Fabric is sorted by colour and composition, cut up, and torn apart by rotating drums covered in wire teeth until it returns to loose fibre. That fibre is then spun into new yarn, usually with a proportion of virgin fibre added.

The tearing is the problem. Fibres that were long enough to spin into a strong yarn come out of the process broken into shorter lengths, and yarn strength depends heavily on fibre length, because longer fibres grip each other over more of their surface. Recycled fibre is therefore weaker, and blending in virgin fibre is not generosity but necessity.

This is a genuinely old practice rather than a modern one. Reclaimed woollen fibre has been made this way for well over a century, and the resulting cloth has a long history in workwear and blankets. It works. It just does not produce the same material it started from.

Chemical recycling goes back to the building blocks

The other route breaks the polymer down to its constituent molecules, purifies them, and repolymerises. Because the material is rebuilt from monomers rather than reused as fibre, the resulting polymer can be effectively identical to virgin material, with no penalty in fibre length or strength.

It is also far more demanding. Depolymerisation requires energy, chemical inputs and clean feedstock, and it only works on polymers that can be broken down cleanly, which in practice means principally polyester. Cellulosic routes exist that dissolve cotton and regenerate it as a viscose-type fibre, though the result is a different fibre rather than cotton again.

Cost is why mechanical recycling still dominates in volume. Chemical processes are expensive per tonne and depend on a supply of well-sorted material, which the clothing waste stream does not readily provide.

Most recycled polyester in clothing did not come from clothing

A widely used feedstock for recycled polyester is post-consumer drinks bottles, because bottle polyester is a clean, well-sorted, single-polymer material collected at scale. Garments are none of those things. They contain blends, dyes, elastane, sewing thread of a different fibre, and trim.

That distinction matters more than it first appears. Turning bottles into fleece is not closing a loop in clothing; it is diverting material from one recycling stream, where bottles could have become bottles repeatedly, into another where the fibre is unlikely ever to be recycled again.

Genuine textile-to-textile recycling is much harder and much rarer, precisely because of blends. A garment that is one hundred per cent of a single fibre has a plausible route onwards. A shirt of cotton, polyester and elastane, sewn with polyester thread, does not.

What recycled content does to the cloth in your hand

For chemically recycled polyester, honestly, very little. If the polymer is rebuilt properly it behaves like virgin polyester, and no reasonable test in ordinary wear would distinguish them.

For mechanically recycled fibre, the effects are visible. Shorter fibres mean more ends at the yarn surface, which means more pilling and a slightly hairier hand. Yarns are usually spun thicker to compensate for lost strength, so cloths tend to be heavier and less fine. Colour is often muted, since recycled feedstock carries its old dye and can only be overdyed into darker or duller shades.

None of that is disqualifying. A heavier, slightly fuzzier cloth in a muted colour is a perfectly good cloth. It is simply not the same cloth, and expecting it to be leads to disappointment that gets blamed on the wrong thing.

Reading recycled claims without cynicism or credulity

A percentage of recycled content tells you about one input, not about the garment’s life. A recycled fibre in a garment that falls apart in a season is worse in every respect than a virgin fibre in one worn for a decade, because the dominant cost of clothing is spread across the number of wears it delivers.

It is also worth asking what the recycled content displaced. Recycled fibre that replaces virgin fibre in a product that would have existed anyway is a real saving. Recycled fibre used to justify making more product is not, and the difference is invisible on a label.

The most useful questions are unglamorous. What is it made of, how many fibres are in it, is it built to be repaired, and will the thing still be wearable in five years? Those decide more than the recycled percentage does, and they are all answerable in a shop.