Bamboo lyocell: how our bamboo underwear is made

From plants to fabric: How are natural fibres turned into textiles?

Most fabrics begin life in a simple way: we collect the natural fibres, spin them into yarn, and then weave or knit them into a fabric. With familiar fibres such as cotton or wool, this process is straightforward to imagine: the cotton bolls are harvested, combed, and twisted into thread; wool is shorn from sheep, carded, and spun into yarn. Since both of these fibres are already fibrous to begin with, the step from raw material to yarn feels quite natural.

But what about something less obvious? What about, for example, starting with a plant? Tall, rigid, green – those hardly seem the right characteristics for a destiny as soft, washable and wearable underwear!

So how do we get from hard stalks to silky, soft fabric?

The answer lies in carefully extracting the plant’s cellulose. This is a structural part of the plant that is then magically reworked through modern processes into smooth, spinnable fibres. This process is called “cellulosic regeneration”.

But this fibre engineering is less about magic and more about science. It turns unlikely raw materials such as plants into fabrics that are soft, strong, and sustainable. The scientific process allows us to expand the possibilities of what plants can become, turning even unlikely raw materials into textiles of exceptional softness and durability.

Understanding Cellulosic Regeneration

Cellulose is the main structural component of plant cell walls. Through “cellulosic regeneration”, the cellulose is extracted from the plant material and then re-formed into fibres. There are 4 key stages:

Step 1: The plant material is harvested and reduced into a pulp

Step 2: The pulp undergoes processing to separate out the cellulose

Step 3: The cellulose is then dissolved and reengineered into fine fibres

Step 4: The fibres (called “regenerated cellulosic fibres”) are then spun into a yarn and woven into a fabric

This method allows plants, such as eucalyptus, beech, pine, or bamboo, to be converted into soft, wearable textiles.

These regenerated cellulosic fibres are neither synthetic fibres (since they didn’t originate from petroleum), nor are they truly natural fibres. This is because they can’t be directly harvested from plants or animals in their useful form. Their properties are, however, more similar to natural fibres, such as cotton, hemp and linen.

The Traditional Method: The Viscose Process

For much of the twentieth century, the most common approach to producing these regenerated cellulose fibres was the viscose process. In this method, the plant pulp is treated with a series of chemicals to produce a viscous solution, which is then extruded and solidified into fibres.

1. The plant is harvested and then alkali chemicals (e.g. sodium hydroxide, sodium sulphide) are used to breakdown the solid material into a pulp
2. The alkali pulp is dried, processed with more chemicals (e.g. carbon disulphide) and finally dissolved again to create a solution
3. The solution is then passed through a sieve-like object called a spinneret. The spinneret separates out the key components, before depositing them into sulphuric acid to form the fibres
4. The fibres are then cleaned, spun into yarn and made into a fabric called “viscose”^[1]

Viscose is therefore described as semi-synthetic: made from natural fibres but using synthetic chemicals. Viscose fibres, sometimes marketed as rayon, can feel soft and comfortable. You might be familiar with seeing “viscose” on clothing labels, for example “bamboo viscose” products.

The viscose process carries significant environmental and social concerns. It is both chemical- and energy-intensive, and it is typically carried out in an open-loop system. This means that solvents and by-products are released as waste, rather than being recovered. As a result, viscose processing of cellulose fibres can result in highly contaminated wastewater, which can be toxic if released into the environment and harmful to workers.

Another concern with viscose production is how the raw plant material is harvested. To be truly sustainable, harvesting needs to follow responsible practices – and certifications are now available to help ensure this. For example, FSC (Forest Stewardship Council) certification guarantees that the plant comes from sustainably managed forests, protecting against deforestation of ancient or endangered forests.

Together, this means that plant-based viscose clothing and underwear, such as bamboo viscose products, while technically made from a green raw material, are not always a truly sustainable choice.

A cleaner innovation: The Lyocell Process

The lyocell process was developed as a more environmentally responsible alternative. In this method, cellulose is dissolved directly in an organic, non-toxic solvent (N-methylmorpholine N-oxide, or NMMO). This is different from the viscose process, which required additional, harsh chemicals such as carbon disulphide to extract the cellulose fibres.  Crucially, the lyocell process is carried out in a closed-loop system, in which over 99% of the organic solvent is recovered and reused.

This results in a fabric that is:

• Produced with far lower chemical emission.
• Safer for workers and surrounding communities

From TENCEL™ to Bamboo Lyocell

The lyocell process was first commercialised by the British company Courtaulds Plc in the 1980s and 1990s, under the brand name Tencel. In 2004, the Austrian company Lenzing acquired the Tencel brand and its production facilities, and today produces TENCEL™ Lyocell, most often from sustainably sourced eucalyptus wood pulp.

More recently, biotechnology has advanced to the next generation of sustainable fabrics. The market has seen bamboo becoming increasingly desirable as a raw material, due to its many desirable natural properties and environmental benefits.

Now, the lyocell process has successfully been applied to bamboo pulp and the resulting fibre known as bamboo lyocell (sometimes marketed under the trade name Monocel). This material captures all of bamboo’s natural advantages and beneficial properties – rapid growth, carbon sink, low water requirements, and minimal need for pesticides – with the highly responsible closed-loop processing system, making it one of the most sustainable fabrics currently available.

^[1] What is Viscose Fabric: Properties, How it’s Made and Where, Sewport