How Quickly Do Fashion Materials Biodegrade?

The vast majority of materials on earth will biodegrade. The problem is that some, like plastic, will take a millennium to disappear.

So what does it mean when a product is labelled as “biodegradable”? It suggests it biodegrades relatively quickly, but the speed depends on who is being asked. Naturally occurring fabrics like cotton and wool tend to break down quicker than manufactured fabrics like polyester, although certain polymers, like rayon, are an exception.

Fashion is starting to pay attention to what constitutes biodegradability. Around four per cent of worldwide waste in 2015 came from the fashion industry, according to a 2017 Global Fashion Agenda and Boston Consulting Group report, and producing more clothing with man-made fibres looks set to only add to that.

But fast fashion brands like C&A and H&M have forefronted compostable and biodegradable clothing designs in recent years as a rejoinder to this, and biodegradable synthetics are growing in popularity. There has been a 42 per cent growth in searches for Tencel during 2019, per Lyst, and since 2017, the number of products containing lyocell in the US has increased by 36 per cent.

The Hohenstein Institute awards biodegradable certification to products by evaluating how quickly they break down in soil. The German research institute tested how well textiles biodegraded over a span of four weeks and found that non-woven cotton and casein samples disappeared completely. Meanwhile, woven cotton and cotton/polyester mixes proved more durable, while a 100 per cent polyester sample stayed almost completely intact.

The results don’t necessarily reflect a universal standard since soil composition and temperature both play a big role in biodegradation. Some materials break down more quickly in conditions like being placed in an industrial composting facility or when bacteria or fungi are added to the mix. The chemicals used to treat and dye materials can also last a lot longer than the fabrics - and they will all be released when the base material falls apart.

That said, some generalisations can be made about textile durability. When buried in soil, rayon and linen can degrade in just a few weeks. (This makes them more biodegradable than cotton.) Tencel, an elastane alternative, takes a bit longer – with a test showing half of the material broke down after 94 days; this is still a much shorter time than the synthetic materials it can replace.

The International Wool Textile Organisation, the industry body representing those working in the wool trade, claims most wool-only based products will almost completely biodegrade after six months in a landfill. (Nonetheless, the material can be hardy: 3,000-year-old woollen clothing was found buried in the Israeli desert in 2014.) Signs of degradation appear in silk after about four years. That is long enough that it is rarely advertised as biodegradable, but the process can be sped up, and all of the material can go in just 12 to 24 months.

The flip side of creating biodegradable apparel is that it can mean foregoing durability and therefore reuse. A material that breaks down quickly also does not necessarily biodegrade cleanly, and technically biodegradable materials could be releasing harmful chemicals as they decompose. However, some compostable standards like Cradle to Cradle certification insist that the soil is protected.