Functionality and sustainability of merino wool

ROTAUF - Nachhaltigkeit von Merinowolle

Schweizer Merinoschafe auf der Weise am Mont Soleil

Merino Wool

The term "Merino" refers to a specific breed of sheep that originated in North Africa. In the Middle Ages, the first Merino sheep reached Spain and from there, at the end of the 18th century, Spanish settlers brought them to Australia and New Zealand. Today, these two countries are by far the largest exporters of Merino wool, followed by South Africa and Argentina.

Merino sheep are shorn every 8-10 months and give - depending on breed and breeding - between 2 and 4 kilograms of wool per sheep per year.

Schweizer Merinoschaf auf der Weise am Mont Soleil

Merino wool functionality

Merino wool is a miracle fibre. Its functional properties, which are highly valued by outdoor athletes - and which we will discuss in more detail in this section - are based solely on the structure of the merino fibres. These are very fine, soft, strongly crimped, scaled and elastic. But let's take it one step at a time:

High wearing comfort

Merino wool is known for its high wearing comfort and for the fact that, unlike regular wool, it does not scratch. The reason for this lies in the very fine fibres. Merino wool has an average fibre thickness of 16.5 to 24 microns (= micrometres = thousandths of a millimetre). For comparison: human hair has a diameter of about 30 microns.

"Normal" sheep's wool is about twice as thick as merino wool. The very fine merino fibres do not stand up on the wearer's skin, which means that merino wool does not scratch.

Insulates well against cold and heat

Merino fibres are highly crimped and can have up to forty crimps per centimetre. This means that the individual fibres in a fabric lie relatively loosely on top of each other and air is trapped in the resulting gaps. This trapped air is a super insulator against cold and also against heat.

Due to the many waves of merino wool, there are also fewer contact points between the fabric and the skin, which means that less heat is dissipated from the body.

Regulates the moisture balance and body temperature

Merino wool can absorb up to 30% of its dry weight in moisture without feeling wet. The merino fibres can bind moisture in the form of water vapour and thus wick moisture away from the skin. The moisture is stored in or between the fibres, while the fibre surface remains dry.

If the moisture evaporates in warm temperatures, cooling evaporative cooling is produced. This makes wearing merino clothing very comfortable in summer too.

Warms when wet

Even in cold temperatures, the merino fibres' ability to absorb moisture proves to be very positive. While the water vapour is bound inside the fibre, the fibre surface remains dry and repels water. A dry wearing sensation is an important prerequisite for high climate comfort.

Through a so-called exothermic process, merino fibres also generate heat when they absorb moisture (so-called absorption heat). This process works until the fibres are saturated and can no longer absorb water molecules.

Neutralises odours

Another relatively well-known property of merino wool is its odour-neutralising effect. Wool fibres have a scaly surface on which bacteria, which are responsible for the formation of bad odours, can only cling with difficulty. In addition, the fibre protein in wool, called keratin, breaks down bacteria on the skin. Less bacteria = less odour.

Self cleaning

Merino wool has a built-in self-cleaning function. The interior of the wool fiber consists of two different cell types that can absorb different amounts of moisture. This causes the two cell types to swell to different degrees when they absorb moisture, which causes a mechanical friction process. This friction process allows the merino fiber to clean itself, especially in humid weather. For this reason, merino clothing does not need to be washed as often as "normal" clothing and you can wear it for a long time.

Flame retardant

Merino wool is flame retardant compared to synthetic textiles. Therefore, in contrast to a quickly flammable synthetic fiber, it is less delicate if a piece of embers hits the shirt at the campfire.

High UV protection

Merino wool protects the sheep and thus the wearer of merino clothing well from UV radiation and a sunburn.

Not very tear resistant

When we think of the functional disadvantages of merino wool, only one thing comes to mind: the fiber is not very tear-resistant. Therefore, care should be taken when putting it on and taking it off, especially when wet. Also, when washing, we recommend keeping merino clothing in a wash bag away from zippers of other garments, etc.


From a functional point of view, merino wool gets almost the maximum score due to all the above properties. Merino wool is a miracle of nature, which even the most modern technology and chemistry can not hold a candle to.

But what about the sustainability of merino wool? In the next section, you'll find out whether the natural fiber performs as well as it does in terms of functionality and how much nature is actually still in merino wool.

Schweizer Merinoschaf auf der Weise am Mont Soleil

Sustainability of merino wool

Let's start with the positive:

Low energy and water consumption

Making a T-shirt from wool uses about 20% less energy than a comparable synthetic T-shirt and 70% less water than a cotton T-shirt. In this day and age of widespread energy and water scarcity, this is very valuable.

Easy to dye

Merino wool is relatively easy to dye, which reduces the use of chemicals and energy. The ROTAUF Bio Merino series is dyed according to the strict Global Organic Textile Standard (GOTS) and is therefore free of harmful substances even after dyeing.


As a natural material, wool is 100% biodegradable and thus theoretically does not contribute to microplastic pollution of the environment. But watch out: In practice, merino wool is often so heavily chemically treated and mixed with synthetic fibers that it can no longer really be called a natural material.... More about this below at the negative.


Wool is recyclable and can be used for new yarns or filling materials. In Europe, the Italian textile district of Prato in particular has made a name for itself with the recycling of wool products.

Needs to be washed less often

As described above in the Functional Properties, merino wool is self-cleaning and odor-neutralizing. Merino clothing therefore needs to be washed less often than conventional clothing. This saves water and energy.

Renewable raw material

Unlike petroleum-based synthetic fibers like polyester or polyamide, merino wool is a renewable resource. All it takes to "produce" merino wool is a sheep, fresh air, water and grass. Quite simply.

Unfortunately, these positive aspects are also countered by many negative ones. Let's take a closer look at these:

Poor climate balance

Compared to other textile raw materials, merino wool has a relatively poor carbon footprint. One sheep produces just under 5 kilograms of methane per year. Methane, in turn, has 28 times the climate impact of CO2 over 100 years. The production of merino wool thus leads to twice as high greenhouse gas emissions as the production of synthetic fiber.

Fun Fact: About 12% of New Zealand's greenhouse gas emissions come from sheep.

Use of chemicals

Natural wool felts and shrinks when washed in the washing machine. Therefore, merino wool must be specially treated to make it machine washable. In this process, the wool is subjected to a so-called "superwash" finish as standard. In order to prevent the wool scales from interlocking during washing and thus the wool from felting, the natural scales are etched away with chlorine compounds. However, these chlorine compounds are highly explosive and leave residues of dangerous AOX compounds in the wastewater. AOX is a group of many special chemical compounds that are dangerous for humans and nature.

After treatment with chlorine, the wool is additionally coated with a plastic layer to make it as robust as possible. The most common superwash finish uses a plastic called "polyamide-epichlorohydrin" for this purpose. As the "-chloro-" part in the name of this plastic suggests, it too is partly made of chlorine. Therefore, toxic AOX compounds can leak out of the clothing through this plastic coating even while it is being worn.

Since the introduction of the Bio Merino series in 2017, ROTAUF has dispensed with a superwash finish with chlorine treatment and plastic coating for these reasons. Instead, we use a gentle process called EXP. So our wool can also be washed in the washing machine - but "only" at 30°C and with a good wool detergent.

Mulesing and Sheep Dipping

Certain breeds of merino sheep are bred with as many skin folds as possible so that the skin surface is as large as possible and more wool grows on it per sheep. Fly maggots can nest in these skin folds, especially around the sheep's tail. To prevent this fly maggot infestation, the sheep's skin folds around the tail are often removed without pain relief. This cruel practice to animals is called mulesing and is now practiced primarily in Australia. In New Zealand, mulesing has been banned since 2018 and South America is also considered mulesing-free because the pesky flies are not found there. 

Another common practice to prevent parasite infestation of sheep is so-called "Sheep Dipping". This involves using specially designed machines to force sheep under water or through pesticide baths in a tank containing pesticides/disinfectants.

To ensure that the sheep that "donate" their wool for ROTAUF clothing can live under species-appropriate conditions and without cruel treatment, we use merino wool from controlled organic animal husbandry (kbT). This standard is based on the European guidelines for organic farming and prohibits both mulesing and sheep dipping.

Land consumption and soil degradation

In many regions of the world, forests are cut down to create grazing land for animals. If there are too many animals per available grazing area, overgrazing can lead to soil degradation, erosion and a loss of biodiversity.

Here, too, the organic standard provides a remedy by regulating the size and regeneration of the grazing areas.

Merino wool is often mixed with synthetic fiber

Due to the relatively low robustness of merino fibers and to facilitate care, they are often blended with synthetic fibers. This can have a positive effect on the robustness and durability of merino textiles, but contributes to microplastic pollution of the environment and prevents the textiles from remaining biodegradable or recyclable.

Long transport distances

Merino wool, as described above, usually comes from far away: Australia, New Zealand, South Africa and Argentina are the largest merino exporters in the world. With the various processing stages, this quickly adds up to 40,000 transport kilometers per T-shirt. 

Due to the regional processing of merino wool (knitting, dyeing, sewing in Switzerland), these values are significantly lower at ROTAUF, but our merino silk clothing also accumulates around 10,000 transport kilometers over the entire value chain. To shorten this distance, we are always on the lookout for more local merino alternatives. With Swiss merino wool and Spanish merino wool, we now offer two such alternatives in individual products and we hope that we can further increase the share of local merino wool over the coming years.


The undisputed functional and ecological advantages of merino wool are offset by a number of ecological disadvantages and animal cruelty methods.

While we can address many of these drawbacks through the use of merino wool from certified organic livestock and environmentally friendly finishing and dyeing processes, some key challenges remain, particularly with regard to merino wool's poor carbon footprint and long transport distances.

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