Textile fibers shorten and weaken with each mechanical recycling pass, so recycled fiber must be blended with virgin fiber, and heavily degraded batches drop out of the loop entirely.
quality_(n+1) = quality_n × (1 - loss_per_cycle)
if quality < min_usable_quality → landfill/incinerate
circularity = collected_and_recycled / total_garments_produced
- Collection rate — fraction of used garments actually collected for recycling instead of directly discarded.
- Fiber loss per cycle — how much quality (fiber length/strength) each mechanical recycling pass destroys — textile fibers "downcycle," unlike glass or metal.
- Min. usable quality — quality floor below which fiber can no longer be spun into new yarn and is landfilled or incinerated.
- Production rate — how quickly new garments enter the use phase, blending recycled and virgin (bright pink) fiber.
Real-world application: this quality-loss ceiling is why most "recycled" clothing today is a small % of the fiber blend, and why fashion brands are investing in chemical recycling that can restore virgin-like fiber quality instead of only downcycling.