Since I have announced myself as a defender of ethical and sustainable fashion, I am often asked the same question: Is it better to buy clothes made of cotton or polyester? This question is definitely justified, especially when we know that these fibers alone account for 80% of the world’s textile fiber production. However, there are many more materials used to make a garment, such as animal fibers (wool, silk, cashmere, angora, etc.), vegetable fibers (flax, bamboo, hemp, etc.), modified vegetable fibers (acetate, tencel, rayon, modal, etc.) and synthetic fibers (acrylic, nylon, spandex, etc.). Each of these fibers has advantages and disadvantages. This series of articles will explore some of them, in order to determine, eventually, which are the best choices from a sustainable development point of view.
Without further ado, here is the first part, which deals with polyester.
Polyester is a synthetic fiber, formed from polyethylene terephthalate (PET) polymer. This is the same polymer that is used to make water bottles. It is, therefore, plastic. Polyester is used for many purposes, but textile production accounts for half of the overall polyester production. This fiber is appreciated by the consumer because it is an easy maintenance fiber and does not cost very much. It is possible to add texture to the fiber in order to obtain different touches, to imitate wool, cotton, silk, or to modify its characteristics such as increasing absorption or preventing creasing. Since polyester is now the most widely used textile fiber on the international market, it is important to question the impact of the use of this fiber in our daily lives.
PRODUCTION OF FIBER AND TEXTILE
Polyester is a product of oil. I will spare you the details of the polymerization, but you have to know that 70 million barrels of oil are used each year to produce polyester. This is enough to drive a Volkswagen New Beetle for 61 thousand years (considering a consumption of 1L per kilometer and a usage of 20 000 km per year). That’s a LOT of oil. After the polymerization, the polyester is pressed through small holes to make filaments, and then cut or textured to make fibers.
It is difficult to accurately calculate the impacts of the polyester polymerization process since the products of each step are not necessarily used to produce polyester for textiles. On the other hand, it is known that to produce filaments, the polyester must be maintained at a temperature of 260 to 270 ºC, which therefore requires a lot of energy (about 125MJ per kg of polyester fiber). Not only is oil used as raw material, but other fossil fuels are used to maintain this temperature. Thus, greenhouse gases are produced. The impact of polyester has been estimated at 694 million tonnes of CO2 equivalents, equivalent to the production of greenhouse gas emissions from 185 coal-fired power plants for one year. A polyester t-shirt alone represents up to 7.1 kg CO2e.
In addition, the production of polyester creates pollution in the water bodies surrounding refineries. To cool the polyester, it takes huge amounts of water, which are not always treated before being released into the environment. In fact, the water surrounding 9 of the 13 largest polyester producers has significant or severe levels of pollution. This pollution, caused in particular by the oxide of nitrogen and oxide of sulfur, can create acid precipitation and contaminate the soil. It would be possible to reduce the ecological footprint of polyester on water by changing wastewater management practices, but this would increase the price.
Once you have polyester fibers, you have to make textile. You have to spin them, then weave them or knit them. They must also be dyed. In the case of polyester, it is this step that is particularly harmful. Indeed, polyester has a dense molecular structure, which makes it difficult to penetrate for ordinary dyes. As a result, this material must be dyed at 100ºC unless an accelerator is used. In one case, it is a huge amount of energy, in the other, we use toxic and harmful products, which will be released into wastewater. In addition, it is estimated that 20% of the dye used to dye polyester is found in the environment as a result of poor wastewater treatment. Thus, many dangerous chemical compounds are found in community water bodies and can make people sick.
EVERYDAY USE
When calculating whether a material is sustainable or not, one must also consider its impacts during its usual use. In the case of polyester, the most important impact occurs at the time of washing it. In fact, it has been determined that about 700,000 microfibers of plastic are produced each time one makes a load of clothes in a domestic machine. These microfibers can escape the water treatment system and end up in rivers and oceans. In fact, plastic microfibers account for 80% of American water pollution. Fish and marine animals ingest these particles, which can make them sick as a result of digestive problems, or because of the toxins present on these microfibers (for example, some plastics degrade in BPA, while others absorb pollutants like the PCB). These toxins can then be absorbed by humans during fish consumption.
Moreover, the polyester is treated to give it properties including anti-crease, anti-mold, etc. Most of these treatments consist of a resin application that often contains formaldehyde. This chemical, known as a carcinogen by the International Center for Research on Canary (IARC), can also cause irritation and contact dermatitis when in contact with the skin. Fortunately, some countries are starting to regulate the amount of formaldehyde that can be found in clothing, but there is also a need to think about textile workers, who are in constant contact with them.
DEGRADATION
As mentioned in a previous article, polyester takes a long time to decompose. It can be up to 200 years! Meanwhile, chemicals that have been used to treat and dye the polyester are released into the soil and water around the dump.
Another treatment, often used for sports and outdoor items, makes it possible to waterproof the polyester textile. This treatment, based on perfluorinated compounds (PFC), is also used to make non-stick stoves and make stain resistant carpets. When the garment breaks up, PFCs (PFOA and PFOS, among others) are released into the environment. These are harmful to the environment and health, and take several years to disappear. Thus, not only can a polyester garment take several hundred years to decompose, but, if treated with PFC, it releases toxic molecules that themselves are persistent in nature. In 2016, Greenpeace conducted a study proving that 90% of technical clothing contained PFCs. In 2017, there were PFCs in the running water of 27 US states. Exposure to PFCs can cause hormonal imbalances and cancers. Fortunately, several companies, like Helly Hansen, have started to find more acceptable alternatives to waterproof their clothes, but very few countries regulate the use of PFCs in clothing.
RECYCLING
It is now possible to recycle water and soft drink bottles and turn them into polyester fibers, as both are actually made from PET. Recycled PET, or rPET, reduces our dependence to oil and the number of plastic bottles found in landfills. In addition, it takes about 70% less energy to recycle polyester than it takes to create new. Recycled polyester is therefore considered a sustainable option to replace conventional polyester. However, the fiber produced is of lower quality and costs more. Also, people should not be encouraged to use more plastic simply because it can be recycled into clothing. PET can not be recycled many times without losing its integrity, and treated polyester is not recyclable at all.
POLYESTER VS COTTON
Although polyester is highly guilty of soil, water and air pollution, we have not yet explored the crimes of cotton. This fiber is extremely expensive to produce in water, pesticides and human lives. It is therefore impossible for the moment to answer the fateful question: What is better between polyester and cotton? Stay tuned for the next article in this series: The Fiber War!
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