Wool's keratin protein can be broken down by microorganisms in suitable environments. Woolmark explains that warm, moist conditions support the fungi and bacteria involved, while clean, dry wool is much more resistant to deterioration. That contrast helps reconcile everyday durability with the fibre's potential to biodegrade.

Wool Breakdown Depends on Moisture, Temperature and Microorganisms

The rate varies with soil, climate and the material itself, so one test duration should not become a universal disposal promise. Blends and other garment components also need consideration. A fibre's end-of-life property describes particular conditions, rather than removing the need to collect and manage worn textiles responsibly.