Wool is partly sustainable. It is renewable, durable and biodegradable, and it sheds no plastic microfibres. But sheep produce methane, grazing needs a lot of land, and welfare standards such as mulesing vary by farm. So the honest answer depends on how the wool was farmed, whether it is certified, and how long you keep the garment.
What wool does well
Wool's strongest points come after the fibre leaves the farm. It is a protein fibre made of keratin, the same protein found in human hair, so soil micro-organisms recognise it as nourishment. A fleece also regrows each year, which is why it counts as renewable.
Durability is the other big advantage. A 2020 life cycle study of a woollen sweater by Wiedemann and colleagues found that how often a garment is worn, and how long it lasts, has the largest influence on its overall environmental impact. A follow-up study found that raising wears from 109 to 400 per garment lifespan cut impacts by 60% to 68%, depending on the impact category. The same paper notes that wool sweaters have the potential for long life, but that the best, current and worst-case scenarios differ substantially.
Wool's environmental impact: methane, land and welfare
The costs are real, and most of them sit on the farm.
- Methane. The International Wool Textile Organisation (IWTO) says greasy wool production on sheep farms produces around 50% of a wool garment's total greenhouse gas emissions. The dominant gas is methane, a by-product of sheep digestion.
- A wide range of footprints. One published summary puts virgin wool at roughly 10 to over 100 kg CO₂ equivalent per kilogram of fibre. The IWTO cautions that sheep breeds, farming systems and climate vary so much that comparisons need care.
- Land. Sheep farming needs extensive grazing land. On non-arable land this can be a reasonable use. Where it drives overgrazing, it degrades soil, reduces biodiversity and can speed up erosion.
- Animal welfare. Mulesing removes a small area of skin from the back of the sheep to prevent blowfly infestation. It is mainly an Australian merino practice, and wool from many other origins is not mulesed by default.
Processing adds further impact. In the woollen sweater study, fossil fuel energy was dominated by wool processing, with substantial contributions from retail and garment care.
How to buy wool more responsibly
- Look for a recognised standard. The Responsible Wool Standard is the best-known one (more below). Be wary of vague phrases such as "natural" or "planet-friendly" with nothing behind them. Our guide to spotting greenwashing in fashion covers this.
- Buy for decades, not seasons. Since wear count matters most, choose a classic cut you will keep reaching for.
- Care for it properly. In that same research, garment care accounted for 12–31% of the direct impacts of the whole supply chain, depending on the category.
- Consider recycled or secondhand wool where it suits you.
Related questions
Is wool better for the environment than synthetic fabrics?
It depends on what you measure. Cradle-to-gate scores such as the Higg Materials Sustainability Index have rated wool worse than polyester, at 81 per kg for wool against 36 per kg for polyester. Critics point out that the index covers only cradle to gate, so it leaves out use and disposal. The Sustainable Apparel Coalition later decided to phase out the MSI single-score on fibres in January 2021. Wool has a heavier farming footprint. Synthetics are fossil-based and shed microplastics. Wool's advantage grows with long wear and a proper end of life.
What is the Responsible Wool Standard?
The Responsible Wool Standard (RWS) is an international, voluntary standard run by the non-profit Textile Exchange. It requires farms to follow the five freedoms of animal welfare, prohibits mulesing, and audits land management, soil health and biodiversity. Chain-of-custody rules keep RWS wool separate from conventional wool through processing. It is not a guarantee of low emissions, and it does not cover all global wool production.
Is wool biodegradable?
Yes, under the right conditions. The Woolmark research body reports that 100% Merino fabrics biodegraded by 95% after 15 weeks buried in soil, though the rate varies with soil, climate and wool characteristics. A study funded by Australian Wool Innovation found wool and viscose rayon readily biodegraded in industrial composting, while synthetic fibres did not. These are industry-funded sources. Dyes and finishes can slow the process, and wool that is kept clean and dry does not readily biodegrade. That is useful in a coat, but it means a landfill is not the same as a compost heap.
Is wool better than cotton or linen?
Each fibre has different trade-offs. Wool is an animal fibre with a methane and land footprint, while plant fibres have their own water and farming impacts. For a wool-versus-plant comparison, see our honest look at whether linen is sustainable.
At ANAHIV, our wool coats, blazers and jackets are made to order, so each one is cut and sewn only after it is ordered. Our jackets, blazers and coats are designed to be worn for many winters, and our wool coat care guide explains how to keep one in good shape.