Since "sustainability" started making an appearance in the fashion industry, fabric choice has become a hotly debated subject. Organic cotton and hemp started the conversation, claiming to be the eco-friendly alternatives to conventionally grown cotton. Unfortunately, just as quickly as they were touted as "good fabrics," environmentalists and conscious consumers retaliated, objecting to the amount of water and land it takes to grow organic cotton specifically. In more recent years, innovation and technological advancements have given rise to new fabrics like Tencel and chemically recycled polyester. Of course, each of these fabrics have critics as well. This ability to find a downside to each fabric used in fashion has given rise to the question, "Is it possible for one fabric to be more environmentally sustainable than others?"
The three main categories of sustainable fabric are recycled synthetic fabric, natural and organic fabric, and rayon. The most common type of recycled synthetic fabric is recycled polyester. Typically polyester had to be recycled manually, which is highly inefficient and limiting. Now chemical recycling is becoming more popular, making recycling a more feasible option. Still, the process remains underdeveloped and not widespread enough to completely replace the demand for virgin fabrics. Recycled polyester also doesn't stack up against natural fabrics in terms of waste production and pollution. Polyester, and other synthetics, release microfibers — microscopic pieces of plastic — when washed using high-speed washing machines. These microfibers make their way into our water supply, and they are nearly impossible to remove from the environment. Polyester also does not biodegrade once it has been disposed. Natural fabrics will return to the environment without leaving behind physical pollution, whereas plastic-based materials stay in the environment for decades or centuries. Recycling is a great way to delay some polyester clothes from ending up in landfills, but there is not enough consumer and brand support for recycling to make it an impactful option.
The obvious solution to issues presented by recycled polyester is the use of natural fabrics instead. Natural materials won't cause plastic pollution as synthetics do, and if natural fabrics are grown without chemical pesticides or other toxins, then they are even more environmentally-friendly. But growing crops, especially cotton, hemp, and other natural fibers, takes a lot of land. As the human population increases, more land is needed, and less land is available. Water is another dwindling resource required for the production of natural fabrics. Cotton is notorious for using a lot of water to grow, although it depends on the practices implemented by the farmer growing the fiber.
The last type of sustainable fabric is rayon, which comes from nature but is processed like a synthetic. Alden Wicker for EcoCult describes the process best, "Rayon is a generic term for fabrics that are made from plants that you could never imagine as soft, silky fabric: bamboo and trees. (A more accurate term would be to call them manmade cellulosic fibers.) These tough plant materials are broken down through a chemical and mechanical process involving sodium hydroxide and carbon disulfide into a viscous liquid, that is then spun into threads using sulfuric acid." Rayon seems to be the worst of both worlds, requiring a lot of land and natural resources and releasing chemical by-products. Viscose is another name for rayon and is the term that will appear more frequently on brand websites. Recently, though, brands have been going by a different name altogether, choosing Tencel, a trademarked fabric produced by Lenzing. Tencel is meant to replace standard rayon, using amine oxide in an entirely closed-loop system to prevent chemical pollution. Tencel cannot replace all types of rayon, though, since each fabric has a different composition and look. Lenzing also makes a rayon fabric called Modal as another option instead of Tencel. While Modal fabric is non-toxic, avoiding the water pollution issue, the deforestation linked to Modal production is can be an issue. If the fabric is sourced from managed forests in North America or Europe, then it is likely that it is not contributing to deforestation, but if Modal is sourced from bamboo forests in Asia — specifically China — then it is possible it is being sourced from bamboo plantations that have replaced the natural bamboo forests.
The farming practices and the chemical processes used to make fabrics can vary widely depending on where fabrics are sourced, who is producing them, and regulatory oversight. That is pretty much the only common factor between each sustainable material; fabrics can be as environmentally-friendly as the manufacturer wants them to be. As a result, no one type of fabric can be considered more sustainable than others. Natural fabrics, recycled synthetics, and rayon all have their ups and downs, but brands can choose the best option for each category by doing their research into their material suppliers and being transparent with their supply chain.