Fashion for the Earth
Viscose, Rayon, Modal, Lyocell, Cupro: Decoding Man-Made Textiles
January 22, 2025
As the demands of the fashion industry surpasses the maximum global production capacity of cotton – an estimated 26 million metric tons – and concerns over unethical labor practices and high water and pesticide usage make virgin cotton less appealing, Man Made Cellulosic Fibers (MMCFs), currently accounting for 6% of the global fiber market are expected to fill the cellulosic gap.
MMCFS, also known as regenerated cellulosic fibers and partially synthetic fibers, are fibers derived from and regenerated into cellulose, differing by process and sometimes specific cellulosic sources. You may recognize the names of common MMCFs such as Rayon, Viscose, Modal, Lyocell, and Cupro, but what are they and how do they impact our environment?
Viscose Rayon
Process
Viscose Rayon is the most popular and longest established MMCF, accounting for 80% of MMCFs. The process begins with mechanical breakdown of cellulosic materials (mostly trees) into cellulosic pulp, which is then dissolved in caustic soda (sodium hydroxide). After steeping for a specified time, it is shredded and allowed to age. The pulp is then treated with carbon disulfide to form an orange-coloured cellulose xanthate. It is then put in a caustic soda of lower concentration. An acetate dope is added to the alkali cellulose stage which is necessary for the yarn luster. Purified cellulose is chemically converted into a soluble compound. A solution of this compound is passed through a spinneret into a coagulation bath usually containing sulfuric acid compounds regenerating the cellulose into solid fibers.
Impact
In the viscose fiber process, steam, pulp, chemical pollution are the main contributors to the process’s environmental impact. Toxic chemicals involved such as carbon disulfide, zinc, and sulfuric acid escape the process, contaminating the air, water, and local food sources, endangering workers and local communities. Carbon disulfide has been linked to higher levels of coronary heart disease, birth defects, skin conditions, and cancer. Repeated exposure to zinc can cause skin cancer. A zinc free process was patented in 1983, however zinc sulfate is still commonly used in the process today.
It is possible to produce rayon more sustainably through responsible pulp sourcing, careful waste water management and water recovery systems (closed system), and clean energy usage, however the process is inherently toxic, and water and energy intensive.
Cuprammonium Rayon (Cupro, Bemberg silk)
Process
Cupro involves a similar process to viscose rayon, alternatively using cotton linters (the fuzz around cotton seeds supplied by the oil mills that make oil from cotton seeds) as their cellulosic source and different, yet still harmful chemicals in the dissolution process. Cellulose is dissolved in a solution of copper salts and ammonia, then extruded into a coagulation bath of dilute acid, alcohol, and concentrated cresol solution. It then goes through several more chemical baths, eventually reconstituting into cellulose.
Impact
As Asahi Kasei is the sole remaining producer of Cupro, we can assess their practices for an accurate depiction of Cupro’s impact. Although the process inherently uses harmful chemicals, their system is closed loop, dealing with chemical pollution responsibly. The company’s OEKO-Tex certification ensures that the fiber doesn’t pollute the environment during wear or degradation.
Cotton linters as a cellulosic pulp source is more sustainable than hardwood, as a high cellulosic-content pre-consumer byproduct as opposed to a valuable carbon sink.
Asahi Kasei appears to be on top of sustainable innovation and transparency, disclosing their partner oil mills, and setting goals for carbon neutrality by 2050, however they still use unclean energy (48% coal), for their intensive process.
Modal (subcategory of Rayon)
Process
Modal production follows the Viscose Rayon process with additional steps and chemicals and is typically derived solely from beech trees. The wet spinning process is adjusted for example by increasing the amount of zinc sulfate in the precipitation bath, or using an increased load of CS2 in dope preparation, spinning solutions with higher DP values, different spinning bath composition and with addition of modifiers, resulting in a modified internal structure.
Impact
The environmental impact of Modal fiber resembles that of Rayon, heavily relying on the sustainability of individual companies’ practices. Modal relies entirely on Beechwood, a hardwood tree. Beech trees are relatively slow growing, growing 1-2 feet per year, and living for 250 plus years. However, when harvested by the coppicing method, they easily and quickly regenerate after being cut. They are often grown on tree plantations, which can contribute to a loss of biodiversity.
Lyocell
Processing
Compared with the viscose process, Lyocell is prepared by directly dissolving cellulose pulp in a non-toxic, non-derivative organic NMMO solvent, and without the need for sodium hydroxide, carbon dioxide, or zinc. The process doesn’t involve a chemical change, making it simpler than Viscose Rayon and has a 99.8% chemical recovery rate.
Impact
Lyocell is considered the most environmentally friendly process among MMCFs.
As chemical pollution and water usage is not a concern with a closed loop system, the electricity, pulp, and steam in lyocell fiber are the main contributors to lyocell’s environmental impact. Like all other MMCFs, the impact of the fiber relies on the individual practices of producers.
Lyocell’s processing method is compatible with other, lower grade cellulose sources, presenting opportunities for chemical fiber recycling as demonstrated by Aditya Birla* with the development of LIVA REVIVA, which uses 30% consumer textile waste and Lenzing with REFIBRA™ technology that uses a minimum of 30% recycled pre/post consumer cotton textile waste.
Using alternative cellulosic sources like bamboo, hemp, byproducts (cotton linters), waste materials or recycled textiles can further reduce the impact of Lyocell production on the environment.
Environmental Impact across all MMCFs
Although MMCFs are a more sustainable alternative to fossil fuel derived fibers, it is important to consider the impact of the industry’s use of energy, water, and raw material sourcing. Producers can implement methods that effectively reduce their energy impact, such as deriving thermal energy from their own byproduct pulp (only 40% of tree matter is used in the process), and substituting additional needs with cleaner energy sources such as wind and solar. To address water consumption and water waste management, closed loop systems are necessary for producers to protect the environment and local communities.
As the main raw material source used are trees — valuable carbon sequesters and habitats which contribute to soil erosion prevention and biodiversity — it is important to consider whether years of carbon sequestration are worth the production of clothing at all. Sustainable harvesting methods when dealing with trees are vital. According to Canopy, roughly a third of rayon comes from materials sourced from ancient and endangered forest and according to their Hot Button Report, one-sixth of the world’s biggest viscose producers are described as “high risk.” As the industry grows, if irresponsible tree harvesting practices continue, we may effectively trade the exhaustion of one natural resource, for another.
Conclusion
Every garment represents water, air, soil, and other natural resources extracted from the earth. According to Textile Exchange, 116 million tonnes of fiber were produced in 2022, and this figure is expected to grow to 147 million tonnes in 2030.
The real answer is degrowth. As long as companies continue to overextend natural resources and produce at scale, alternative raw material sources may effectively exchange one problem for another. The realistic answer is policy. The fashion industry has historically been under-regulated and opaque, making ethical and environmentally conscious practices largely voluntary. Although some materials are more sustainable than others by nature, much of a material’s impact depends on factors determined by the producer, making it difficult for consumers to make ethical decisions based solely on a material tag.
Understanding the nuance of where your clothing comes from is important in understanding its environmental and ethical impact.
You deserve to know what you’re buying. Use your voice to demand transparency from brands. Read EARTHDAY.ORG’s Fashion Legislation Report to learn about all the recent laws enacted in the European Union, The United States and around the world that intend to control fast fashion and its adverse impacts on the natural world and all living things.
