Cotton’s Tricky Problem in a Circular Economy
Updated: Nov 22, 2021
Cotton has long been one of the most important fibers in the textile industry. Cotton fiber, which accounts for about 25 percent of global fiber production, ranks second after polyester in terms of market share. Humans have been using cotton for thousands of years, and the earliest known archaeological findings of (wild) cotton are estimated to date back 6,500 to 8,000 years ago.
Cotton has always been a favorite of consumers in terms of its properties.
It is a natural fiber, absorbs sweat very effectively and is breathable, ideal for hot climates and sports. Most people prefer the feel of cotton on their skin, which is why socks and underwear are usually made from cotton.
Cotton is a natural fiber mostly made up of cellulose (the material that forms the cell wall in plants). It comes from different species of the Gossypium plant, where its main function is the remote dispersal of the plant's seeds. Botanically, it is part of the broader Malvaceae family to which cocoa belongs.
Cotton in the Spotlight
With sustainability awareness gaining more and more momentum, consumers are increasingly critical of the second most popular textile material. Cotton has long been criticized for its impact on the environment, as it requires an enormous amount of water to grow and has devastating effects for the habitats from which this water is taken.
Take, for example, the Aral Sea.
It was once the fourth largest sea in the world.
Tragically, its disappearance has been so clearly documented that it has been described by the UN Secretary-General as "possibly the worst ecological disaster of our time".
The main reason for its disappearance is intensive cotton production in Kazakhstan and Uzbekistan, where water is diverted from Syr Darya and Amu Darya.
On the other hand, the increasing global demand for textile fibers, including cotton, is challenging the textile industry. Cotton production is a highly resource-intensive process. Not only does it need large amounts of water to grow. Normally 10,000 to 20,000 liters are used to produce one kilogram of cotton. It also needs large farmland and pesticides. It is often used in a way that pollutes the environment in the region and can cause serious health effects.
With a growing global population, this is contributing to the increasing scarcity of clean drinking water and farmland for growing food, especially in highly populated underdeveloped countries. So, besides the ethical aspects, these raises the question of what will happen to increasing cotton demand when sources of production reach a breaking point.
The textile industry invests heavily in cotton recycling research. But what many people do not realize is the fact that cotton has no place in a circular economy, at least forever. But why is that?
To understand this puzzle, we must investigate what happens when you recycle cotton.
First of all, there are generally two different ways to recycle cotton.
One is mechanical recycling and the other is chemical recycling. During mechanical recycling, textiles used to regenerate yarn are broken down. The problem with this is that the cotton fibers are damaged during this process. They will shorten with each repetition. This consistently lowers the quality of cotton fibers and ultimately they become too damaged to be used. This process can be slowed by mixing shorter and longer cotton fibers, but if you stop or significantly reduce the production of new virgin cotton in favor of a closed-loop circular economy, you will eventually have fibers that are too short to be used. And this will be the end of cotton in textiles.
This major disadvantage of mechanical textile recycling is the reason why chemical textile recycling is best positioned to recycle all textiles in a circular economy. Chemical textile recycling technologies can create fibers that are of the same quality as new fibers, ready for reuse. This makes technologies indispensable in a circular economy.
But the trick is, they can't turn cotton into cotton.
Why You Can’t Recycle Cotton Into Cotton
This must be one of the biggest surprises:
When the input is cotton, the output is not cotton.
As mentioned earlier, at chemical level, cotton is mainly composed of cellulose. So when we talk about recycling cotton, we are technically talking about recycling cellulose. Cellulose is basically a biopolymer that is a long chain of glucose molecules linked together. Most of these chains are put together and ultimately this is what creates the true fiber we can see. So when recycling cotton, cellulose is dissolved in a solvent that produces a thick, sticky solution, and then this is pushed under high pressure through small holes to produce new fibers.
When you chemically recycle cotton, the output is a type of Rayon.
There are many technologies that can turn cellulose into fibers on a large scale in a chemical process. Although most use wood pulp, the mechanism is the same. All use cellulose as input, but the output is always what is called Rayon.
Rayons are man-made cellulosic fibers. The most famous example of artificial silk is probably viscose, which doesn't intuitively feel like an organic fiber. Another popular rayon is lyocell, also known under the brand name Tencel, and there is also a handful of lesser known rayon. Each is different from each other because of the different chemical processes they go through.
The reason why all these chemical processes are not cotton is that they result in a fiber with a different physical structure than cotton. They are still composed of cellulose, but their properties vary. While natural cellulose has the specific structure and properties of a natural material, artificial silks are man-made fibers that have undergone some physical changes in certain chemical processes. A simpler way to think about this is that a chemical process cannot completely replicate a plant's natural functioning.
Towards a Circular Economy
For the reasons stated, cotton has no place in the closed loop circular economy. Mechanical recycling cannot maintain its quality in the long term, and chemical recycling turns it into a different fiber. However, since the cellulose itself can be recycled, the value of the fibers can be preserved. And protecting the value of resources in this way is the spirit of a circular economy.
Unless companies agree to use rayon instead of cotton, new virgin cotton will have to continue to be produced. So, to pave the way to a circular economy, textile companies need to rethink the composition of their textiles.
The gradual transition from cotton to rayon will allow people to continue to wear natural fibers in a closed-loop circular economy. This is the way to make circular fashion come true.