There is growing interest in compostable clothes, with some brands aiming to create garments that harmlessly degrade to nothing in your home compost heap. There are two key categories of fibres that could currently be used for compostable clothing: natural fibres such as cotton, flax (linen) and hemp, or compostable synthetic fibres. However, there is much more to think about than the choice of material. In this article, we outline 7 key barriers to creating truly compostable clothes.
1. Additives, Coatings and Auxiliary Chemicals Are Problematic
The presence of additives, dyes, coatings, glues are big barriers to the creation of compostable clothes. Together, these may make up to a few percentage points by weight in some cases. Many of these additives and auxiliary chemicals in compostable clothes would also need to biodegrade under composting conditions. Equally, any additives would also need to have low eco-toxicity if they are released into compost. It is clear that leaching of dyes, for example, based on heavy metals such as chromium or ‘legacy’ azo-dyes into compost would be problematic – they would contaminate the compost and preventing it from having any real application in the natural environment. Certain additives and coatings may also slow or prevent biodegradation from happening.
Getting around this limitation requires radical transparency into the supply chain of garments and the textiles that they are made from. This transparency is needed especially when it comes to these “auxiliary” chemicals.
2. There Is A Lack of Compostable Fibres Suitable For All Applications
Not all compostable fibres are equal. For example, it is possible to create man made synthetic fibres which are also able to compost. These may either be fully bio-based, partially bio-based, or based entirely on petroleum-derived polymers. Some of these compostable synthetics are only compostable in industrial composting facilities, such as those based on PLA (polylactic acid).
In general, there is a lack of commercially available alternatives for current synthetics such as polyester, nylon and spandex. Especially those which have exactly equivalent properties but that are also compostable in home settings or in natural environments, such as in soil or in the sea.
Natural fibres from cotton, flax and hemp as well as man-made cellulose fibres such as viscose and lyocell may be compostable, if minimally treated. However, these may not be appropriate for sports and outdoor wear applications, if breathability, waterproofing and stretch characteristics are needed.
3. Zippers, Buttons, Threads and Labels Also Need to Be Compostable
All parts of compostable clothes must be compostable, including zippers, buttons, threads, labels and other auxiliary components. If not, it may be better to make them separable so that the compostable component is isolated. However, the logistics and cost behind the manual removal of such components needs to be taken into account.
It cannot be assumed that a typical consumer or industrial composting facility will have the capability to do this themselves.
4. The Logistics and Infrastructure for Compostable Clothes Is Not Well Developed
Putting in a place a system for collection and composting of clothes on a large scale is a key part of the challenge. Two factors come into play here. One is that many consumers do not have access to their own home composting facility. The other is that many materials can only be successfully composted in industrial composting conditions, not in a typical home compost heap. Thus, a reverse-supply chain would need to be set up that is able to hand large volumes of compostable clothing and textile waste. This waste is also generated from many different sources: in garment cutting factories, from consumer kerbside waste collection, brand overstock or in store take-back schemes. Then the clothing would need to be graded (for resale), sorted (by fibre composition) and packaged for further delivery to composting facilities. The garment would in some way need to be identified as compostable during this sorting procedure.
To a large degree, the adoption of used clothing as a feedstock for composting would depend on its usefulness in making quality compost by commercial composting facilities, as well as the timeframe that it composts in – typically in under 12 weeks. Even compostable packaging, which is much more developed than compostable clothing, is tricky for composters in some regions, such as Germany.
Due to difficulty of identifying what is compostable and what is not, many may simply choose not to accept clothing as a feedstock at all unless it conforms to very strict requirements.
5. In Some Cases, It Can Be Better to Recycle Rather Than Compost a Material
In some cases, it may be more beneficial for the carbon footprint to recycle compostable clothes rather than actually compost them. This needs to be taken on a case by case basis, as it depends on the specific carbon footprint of the virgin material and the energy usage of the compared recycling process.
For example, with the biopolymer PLA it takes enough energy to turn the raw material (such as corn or sugar cane) into the synthetic fibre that it makes sense to keep the material “in the loop” as many times a possible, if we can. In this case, if the recycled material substitutes an equivalent amount of virgin material, then there will be a significant carbon saving.
The composting process itself typically has a minor carbon impact when compared to any potential recycling process. But by composting the material, however, the material is destroyed and an equivalent amount of virgin material will need to be created to fill the gap in the supply chain. This may significantly outweigh the carbon footprint of the composting process itself.
Natural fibres from cotton, flax and hemp may be compostable in home conditions but can also be recycled too, by dissolving them and turning them into regenerated cellulose fibre such as lyocell or viscose. This use of waste cotton cuts out the need for the energy intensive pulping of wood required for these kinds of fibres.
6. The Issue of Microfibres Still Remains Open
There is often an assumption that compostable clothes will be a solution to microfibres in the marine environment. However, this very much depends on whether the fibre is able to degrade in marine environments in the first place. Even if a material can be proved to be compostable, it may not degrade in marine conditions. Although there is a marine degradability certification offered by organisations such as TÜV, it does not cover every possible condition likely to be found at sea, especially cold temperatures.
There is also a growing body of research showing that cellulose based natural fibres are present in greater quantities in the ocean than synthetic fibres. Cotton clothes, for example, can’t be assumed automatically to be “marine-safe”, especially if they are heavily chemically treated with dyes and coatings. It is fair to say that there is more research in general on this issue needed, as the effect of non-plastic microfibres on the marine ecosystem is currently not well understood.
7. There Is a Lack of Certifications and Standards for Compostable Clothes
Lastly, there is lack of validation and verification of the compostability claims of compostable clothing and the fibres they are made from. There are plenty of examples of garments advertised with undefined claims of “biodegradability”. Many do not specify the timeframe or conditions in which the clothing might be said to biodegrade. Due to crackdowns by national advertising standards agencies, this may open companies to penalties and legal action if they cannot prove the claims that are being made.
Compostability certifications for home and industrial compostability are already common for packaging. Some fibres such as Tencel branded lyocell are certified as both home and industrially compostable. However, going a step further and certifying a whole piece of clothing as compostable is a much greater feat. As we have seen, there is a huge range of factors that mean in practice, the whole garment itself may not be easily compostable. In many ways this is similar to claims of recyclability: it may be difficult to substantiate that something will ever actually be recycled or composted. Fashion brands who go the extra mile to demonstrate the possibility give themselves much greater credibility.
Dr. Ashley Holding,
Principal Consultant @ Circuvate
To learn more about bio-based materials for fashion, including compostable materials, you can sign up to our comprehensive, 10 week training course “Innovation in Bio-based Materials for the Fashion Industry” which starts in September 2021.