Textile recycling: technologies and perspectives

Jun 1, 2022 | GreenWeave

Why talk about textile recycling? What does it mean?
Is the textile industry currently sustainable? How to make it so? What are the future perspectives?

If you are looking for an answer to these questions, you are in the right place.
World textile production has been steadily increasing for decades and is expected to increase even more rapidly in the near future.
In the past clothes were basic necessities and textile production was limited to responding to this primary need. Today they have instead become fashion items and as such they have an increasingly shorter life span. At the same time, their material composition is more and more complex: in fact, 63% of the fibers derive from petrochemical products whose production and disposal generate significant emissions of carbon dioxide. The remaining 73% is dominated by cotton, whose cultivation requires huge quantities of water and is often accompanied by the intensive use of pesticides.
Fabrics are then subjected to treatments such as finishing, dyeing and printing, which cause further exploitation of natural resources and further CO2 and particulates emissions.

These rhythms have now become unsustainable for our planet, and this is why it is necessary to increase reuse practices and textile recycling technologies, aimed not only at reducing the production of virgin fibers but also at optimizing the use of dyes and productive resources.

Raccolta differenziata, riciclo tessile: stato dell'arte - Textile recycling: state of the art

Recycling in the textile industry: state of the art

According to the European Commission, every year 38% of textile products (around 2.1 million tons) are collected separately and destined for recycling or reuse, while 62% are disposed of with mixed waste. A percentage that is still too low and must increase exponentially immediately before it is too late. For this reason, in 2018 the EU adopted a circular economy package requiring separate collection of textiles in all Member States by 2025. On 31 March 2022, the Commission also published the new EU strategy for the textile, which will soon be accompanied by a set of minimum standards and criteria that aim to make textile products sustainable and circular.
But what are the recycling practices currently in place? And what are the limits to overcome?

Current recycling techniques

The primary goal of textile recycling is to transform end-of-life products into new fibrous material that has properties similar to virgin material. Current technologies are able to recover fibers from those textile scraps composed of a single type of filament. However, problems arise when trying to work with multi-material textiles.
The first and most immediate solution is to avoid producing this type of fabrics from a recycling point of view, but in the new EU strategy there is also the intention to collaborate with the industry in order to implement recycling techniques as to succeed to work also with multi-materials.
So let’s have a look at the main technologies currently used for textile recycling.

Attuali tecnologie di riciclo tessile - current textile recycling technologies

MECHANICAL RECOVERY OF FIBERS

The fabric is disintegrated to obtain new loose fibers for new yarns. It usually takes place through the Garnett machine that with its rotating drums and metal pins destroys the textile structure to get shorter fibers than the originals. For this reason, a preliminary and careful selection of the material by composition is necessary: blends of different fibers and colors result in a low quality yarn.

RE-SPINNING OR THERMAL RECYCLING

Fabrics composed of thermoplastic fibers and fibers that can be dissolved in solvents are melted or dissolved to produce a solution used for re-spinning. Not only end-of-life fabrics, even plastic bottles can be recycled with this process and it is in fact a much more widespread practice than thermal recycling. This is also because, as with other recycling technologies, there are major processing limits on multi-material fabrics.

In any case this is a useful process to treat also natural fibers as cotton, in this case it is called Lyocell process. Through this virtuous technique the cellulosic material is first dissolved in NMMO-monohydrate (an organic compound) and then subjected to a water or NMMO aqueous solution centrifuge, where it coagulates and forms a new fiber. With this, an ecological and biodegradable fabric is created so that in certain environments it can decompose in just 8 days.

FEEDSTOCK RECYCLING AND CHEMICAL RECYCLING

The polymeric structure of the tissue molecules is broken into smaller pieces, called monomers or oligomers. They are then re-polymerized and the obtained polymers reunite into new fibers. This process can actually be both nonspecific with thermal processes – such as pyrolysis, hydrocracking and glazing – and very specific with chemical reactions such as alcoholysis, glycolysis and hydrolysis.

Compared to other recycling techniques, this offers particular advantages: pyrolysis, for example, can be used with multi-material textile or with a mixture of different textiles without a preliminary selection.
However, these are processes that are potentially not very ecological or very difficult to manage.

In this sense, the emerging biochemical processes, such as enzymatic recycling, are of particular interest. Cellulase enzymes, for example, can be used in the treatment of cellulose-based textiles (cotton, viscose, lyocell) as biocatalysts to accelerate chemical reactions and break down fiber polymers faster.
There are already some attempts to have multi-material tissues undergo biochemical processes through the use of other types of enzymes, but they are still being tested.

Tecniche di riciclaggio tessile: chimica e biochimica - textile recycling: chemical and biochemical

However, the categorization of the techniques illustrated so far has to be taken very carefully: in most cases not only are none of these used, but rather they are mixed together.
For example, the thermal recycling referred to the conversion by melting of pellets or PET into fibers is actually carried out on materials treated first of all by mechanical means, therefore it is more precise to speak of thermomechanical recycling.

OTHER FORMS OF RECYCLING

As already pointed out several times, the biggest limitation of these technologies is the treatment of multi-material fabrics. While there are promising new technologies capable of separating the most common blend of cotton and polyester, currently the only truly environmentally friendly methods that can overcome this limitation are composting and vermicomposting. These two processes do not give life to a new textile material but are nevertheless noteworthy because they eliminate waste by giving waste a new function.
With composting, different types of fungi and bacteria are used to break down organic waste into a very nutrient-rich fertilizer. With vermicomposting, this process is accelerated by adding living creatures such as earthworms. The fertilizers obtained from both these processes will not generate new fibers but can close the circle by feeding the land dedicated to cotton production.

Another valid operation that does not require the use of any technology is the reduction of textile waste to mops for cleaning and drying. Obviously, only fabrics with high water absorption capacity can be recycled in this way, and it is a practice that only partially meets the sustainability needs of the textile industry, anyway iit is a simple and effective process to take into account.

Altre forme di riciclo tessile - compostaggio e compostaggio verminale - other forms of textile recycling

Conclusions

Textile recycling is ultimately still too little widespread, albeit increasingly investigated and tested in its various forms. In fact, in the EU only 1% of waste becomes new fabric. It is true, however, that the differences between countries are substantial, even between geographically neighboring countries. In Germany, for example, 75% of textile waste is already collected separately, which is a much higher rate than the European average 38%.

However, the mobilization of the institutions, especially the EU bodies, seems promising: with the introduction of new rules for the textile industry in the second half of 2022, we are confident in a strong ecological boost. After all, the goal is to make all EU textile products sustainable and circular by 2030.

Recycling techniques exist, as well as useful innovative ideas. The fundamental step is now to give the chance to develop and implement them through incentives and investments for Research.

Meanwhile, reuse practices are spreading: rental, second-hand shops and e-commerce, flea markets, charities and clothing bookstores are all booming businesses.

Moreover, a very important habit that is too neglected and needs to be urgently resumed is repair. This is, in fact, the first step towards a radical change of paradigm: returning to conceiving textiles as durable products and not as disposable products of fast fashion. It is essential to raise awareness: information on products and their environmental impact, labels and transparency are indispensable means to educate consumers to buy only what they need and to make more sustainable choices.

Changing a habit is never easy, but often the mistakes of the past seem obvious to us. Let’s become aware of it right now, let’s make fast fashion our past right away.

Do you want to study the EU disciplines relating to the textile sector in depth?
Read also: Sustainable textile: the new EU strategy

 

REFERENCES:

Textile recycling processes, state of the art and current developments: A mini review
Benjamin Piribauer and Andreas Bartl
Waste Management & Research
2019, Vol. 37(2)

Circular economy indicators for organizations considering sustainability and business models: Plastic, textile and electro- electronic cases
Efigenia Rossi, Ana Carolina Bertassini, Camila dos Santos Ferreira, Weber Antonio Neves do Amaral, Aldo Roberto Ometto
Journal of Cleaner Production 247 (2020) 119137

Environmental impact of textile reuse and recycling – A review
Gustav Sandin, Greg M. Peters
Journal of Cleaner Production 184 (2018) 353e365

Environmental impact of the textile and clothing industry – What consumers need to know
EPRS | European Parliamentary Research Service
Nikolina Šajn, Members’ Research Service, PE 633.143 – January 2019

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