Everything You Need to Know About Wool

Wool is a protein that grows from the skin of sheep, goats, and other similar animals. Wool also refers to a textile that is made from the animal's fleece once the wool is shorn, spun, and woven into cloth. Because fleeces regrow every year after shearing, wool is a natural, renewable fiber source, making it one of the most sustainable sources of clothing.

How Wool Is Made

Wool comes from many different animals. Sheep are the most common producers, as they are a docile and widely domesticated species, but wool can also be shorn or gathered from goats, llamas, yaks, rabbits, musk oxen, camels, and bison. 

Sheep are typically shorn once per year in springtime. When shorn correctly, a fleece comes off the sheep in a single piece and the animal emerges unharmed from the procedure. The fleece is then scoured, which is a cleaning process that removes dirt, twigs, leaves, and excessive lanolin (a naturally produced oil that is kept for use in cosmetics and ointments). 

The cleaned wool is prepared for spinning. There are two ways to do this, either by carding or worsting. In her book, "Putting On The Dog: The Animal Origins of What We Wear," Melissa Kwasny explains the difference. The carding method pulls fibers apart, creating a "fluffier, warmer product because of the air pockets it creates," and results in woolen yarn. Worsting, by contrast, combs and straightens the fibers, aligning them in a way that's similar to combing our own hair. Kwasny writes that worsting "results in a tighter-spun thread that is more durable than woolen fabrics but not as warm."

Both woolen and worsted yarns are woven into fabrics on large horizontal looms, most of which are now computerized machines that work at high speeds. Patterns can be incorporated into the cloth during weaving, or the cloth can be dyed after weaving. Some finishing procedures are used to alter the consistency of the final product, such as brushing to make it fleecy or coating with resin to make it machine-washable.

New Zealand and Australia have the most sheep per human population, but China and Australia have the most sheep overall. According to Kwasny, China is both the largest importer of raw wool and the largest producer of wool textiles.

Benefits of Wool

Wool is made of a protein called keratin held together by lipids. It differs from plant-based fabrics, such as cotton, which are comprised of cellulose. Wool grows in clusters called staples and has a crimped texture, which makes it easier to spin because the fibers stick together. The Campaign for Wool explains that the crimped texture makes it breathable:

"This unique structure allows it to absorb and release moisture — either in the atmosphere or perspiration from the wearer — without compromising its thermal efficiency. Wool has a large capacity to absorb moisture vapor (up to 30 percent of its own weight) next to the skin, making it extremely breathable."

This capacity makes wool a "hygroscopic" fiber. This means it is constantly reacting to the wearer's body temperature, cooling the body in warm temperatures and warming it in cool temperatures – the original "smart" fabric, one might say.

The Campaign for Wool goes on to explain that wool fibers can bend back on themselves up to 20,000 times without breaking. This natural elasticity gives wool garments "the ability to stretch comfortably with the wearer," but then "return to their natural shape, making them resistant to wrinkling and sagging."

Wool is a highly versatile material that is used for a range of products, including clothing, socks, shoes, insulating base layers, home insulation, mattresses, bedding, carpets and rugs.

Environmental Impact

Wool comes from animals, most of which are domesticated and therefore have a significant impact on the environment they inhabit. Sheep are ruminants, which refers to their specialized digestive process, but for the purposes of answering this question means that they release methane gas. Roughly 50 percent of wool's carbon footprint comes from the sheep themselves, whereas other fabrics have larger emissions from their production processes. After hemp, wool consumes less energy and has a smaller carbon footprint than other textile fibers. This is partly because sheep can be raised on non-arable lands and rough terrains.

There is concern that increasing flock sizes is causing overgrazing in Mongolia, India, and the Tibetan Plateau. Kwasny writes that the domestic goat population of Inner Mongolia has risen from 2.4 million to 25.6 million animals over the past 50 years, driven by demand for cheap cashmere. "This exorbitant growth has led to overgrazing a very dry, fragile landscape and, in some places, to desertification of native grasslands," Kwasny explains. Displacement of native wildlife, such as Bactrian camels, ibexes, and gazelles, is another problem. 

From a sustainability perspective, wool is an entirely natural product that is fully biodegradable. It breaks down quickly, returning its nutrients to the soil without releasing plastic microfibers into the environment, as its synthetic rivals do. 

Many wool products do, however, contain harmful chemical dyes or finishes which can be released into the environment while a discarded item biodegrades. Commercial dyeing is a chemical-intensive process that relies on heavy metals and produces toxic waste. Since much of it is done in developing countries with minimal oversight and regulation, heavy metals and toxic waste are a frequent byproduct of all textile finishing.

Wool is said to be the most reused and recyclable fiber of the major apparel fibers (via Woolmark). An increasing number of companies are making beautiful clothes from recycled wool, such as these sweaters from prAna, which use textile waste that's been respun without redyeing. 

Impact on Animals

There is legitimate concern over the conditions in which many sheep and goats, in particular, are kept for their wool. As industrial production scales up to meet growing global demand, many sheep are being kept in increasingly cramped conditions on overgrazed land. Video footage, released by PETA in 2018, revealed cruel treatment by shearers in South Africa.

A controversial procedure called mulesing has caused many fashion brands to boycott wool in recent years. Mulesing is the process of removing folds of skin from around a merino lamb's anus to prevent flystrike, when flies lay eggs and burrow into the animal's flesh. Mulesing is painful and bloody and has been banned in New Zealand, but is still practiced in parts of Australia. People shopping for wool should look for non-mulesed products.