BIRTH OF RAYON (1855)

Probably the most famous chemist when it comes to the history of rayon fibers is, Georges Audemars. His groundbreaking patent describes the entire process in which to obtain a regenerated cellulose fiber. That fiber will later be known as rayon. I want to give you the basic steps of his process as they are the building blocks to everything to come.

Boil the bark from mulberry trees in water in order to separate the inner bark. The inner bark will become the soon to be fiber.

Create a pulp from the inner bark using carbonate soda, soap and nitric acid.

Soak that pulp in an ammonia-alcohol solution and bleach it with chloride of lime.

A end fiber is created. This fiber can be “hackled, combed or carded and then spun like cotton”.

He mentions the ability to use this end fiber for photographic purposes by converting it to an “explosive compound” and doing some more chemistry. He also recognizes the fiber as a substitute for silk.

The chemical solution for lyocell was first patented by Dee Lynn Johnson. He was experimenting with different acetate solutions in order to find a cheaper film alternative for Eastman Kodak. In the process, he found that dissolving cellulose in amine oxide would strengthen paper. The 1969 patent claims, the “highly preferred” amine oxide is, “cyclic mono(N-methylamine-N-Oxide) compound” or NMMO. He also claims an increased wet and dry tensile strength when certain anime oxides (including NMMO) are used. NMMO is also part of the process to dissolve blended cotton/polyester fabrics for reuse.

Neil Franks and Julianna Varga of American Enka created a process to derive “higher concentrations of cellulose” in an amine oxide solution. In the end, this new solution made the process more economically friendly as it increased the amount of fiber per batch. Another chemist at American Enka, Clarence C McCorsley III developed the commercial potential further by finding a way to feed the solution (dope) through an extruder. This made it possible to spin it into a yarn. American Enka would stop research in 1981 due to engineering concerns and economic viability. They will return to the lyocell race later but as part of Akzo Nobel.

Patrick White’s R&D team at Courtaulds was the first to fully commercialize lyocell in 1982 and reach production capacity in 1992. Courtaulds is also credited with pioneer the famous trademark name Tencel in 1990. Courtaulds developed two production plants for the fiber, one in Grimsby, England and the other in Mobile, Alabama.

Around this time, the Austrian company Lenzing starts to patent lyocell technology and production processes similar to Courtlauds. The two companies proceed into lengthy court battles of around 690 patents. It would cost both sides tremendously with one estimate of around 5-10 million pounds (in mostly legal fees) for Courtaulds. The entire court battle is a little confusing but in the end, both companies reached an agreement to share the patent rights royalty free. Lastly, in 1998, Courtaulds was acquired by Akzo Nobel in a move for dominance of the paint and coating sector. It received Tencel in the process.

From 1998 to 2004, nothing really came of Tencel or lyocell for that matter. Akzo sold the rights to Tencel to CVC Capital Partners in 2000 and Lenzing was struggling to increase lyocell’s market share. However, what transcribed in 2001 would in my eyes, decide Tencel’s fate. In 2001, the courts of the European Union denied CVC’s acquisition of Lenzing due to antitrust issues. Instead B&C Privatstiftung, funded by the Bank of Austria, bought (and currently holds) a majority share in Lenzing. The purpose of the holding was to invest in Austrian owned businesses. With the new cash infusion, Lenzing flipped the script and bought the trade name Tencel from Corsadi BV, a subsidiary of CVC, in 2004. Might seem weird but if you read the case from CVC’s potential buyout of Lenzing, you will see that lyocell had nothing to do with the EU’s antitrust decision. In the acquisition of Tencel, Lenzing also acquired both the Grimsby and Mobile plants, which had cumulative production capacities of roughly 80,000 tons of lyocell annually. Lenzing’s Heilgenkreuz plant only totalled 40,000 tons at that time.

Jumping forward to the present, Lenzing is by far the leading lyocell producer in the world. In 2017, Lezning’s Heilgenkreuz plant announced that is would increase its production capacity by 25,000 tons. It still has the plants in Grimsby and Mobile with latest production capacities of 45,000 and 51,000 tons for Tencel, respectively. It also plans to finish production in 2020 on a new state-of-the-art Tencel facility in Prachinburi, Thailand. The plant will have a production capacity of 100,000 tons.

Viscose is the most common form of rayon and often used as a synonym for rayon. It’s mainly derived from hardwood trees such as, beech, spruce and eucalyptus. The end fiber is considered 100% biodegradable. A few of the major environmental concerns with viscose include deforestation, chlorine bleach treatment, water usage/footprint and air emissions from carbon disulphide (CS2).

Deforestation can be minimized by sourcing trees from semi-forests or plantations that hold certifications such as FSC and PEFC. Currently, there are 120 million trees being cut down annually for viscose production.

Chlorine treatment, which we will discuss in depth later, can be partially mitigated by using TCF or ECF treatments.

Water usage is considered to be high and varies a lot. However, overall water footprint is significantly less compared to both polyester and conventional cotton.

One of the main chemicals needed to produce viscose is CS2. During the viscose production process, CS2 emits sulphur compounds which are hazardous to the environment. The exact amount air emissions is not well known but emissions do increase significantly with the amount of CS2 used. Companies like Lenzing, have invested in air filtration systems that curb the amount of CS2 released into the atmosphere. Unfortunately, it does not seem that we can currently capture 100% of the CS2 emissions.

We will talk about this below.

Modal has an identical process to viscose (see viscose) with the major difference being the amount of CS2 needed. Once again, the amount really depends on the production size but one study estimates the amount of CS2 needed for modal is around 10-20% higher compared to viscose. Remember, CS2 emits sulphur compounds during the production process which are hazardous to the environment. The exact air emissions are not well known but depend on the amount of CS2 used and the ability to capture those CS2 emissions at the production site.

Cupro or Cuprammonium Rayon is a complicated fabric from a sustainability standpoint. It’s made using cotton linter but don’t get that confused with cotton lint. Many call this a by-product of the cotton industry, which is not wrong, but not necessarily accurate either. It’s still cotton. Like all rayon, cupro is 100% biodegradable!

According to Asahi Kasei, the leading producer of cupro, 99.8% of the waste created during the production of their cupro is recyclable. That waste is used to power their factory through incineration. I should note, about 40% of the energy needed to power Asahi’s plants comes from renewable resources, while the remaining comes from mostly coal and natural gas... which is a great start.

Now, here’s the confusing stuff. While the process might be nearly 100% zero waste, it’s not closed looped. I don’t see this as a negative but instead, an important distinction for what follows. Since the chemical solution cannot be reused, it’s either incinerated or deemed a waste. I am not sure if a closed loop process is possible for cupro but Asahi Kasei does not claim such.

Now for that small amount (0.2%) of waste. While the environmental impact of cupro’s waste is a contentious topic, my understanding is that when treated correctly, the waste is considered to have a low environmental impact. However, the treatment of this waste (again a contentious topic), has been considered by some to not be economically feasible. In 1996, the United States government stopped the production of cupro due to the “cost of cleaning waste water to meet clean water standards”. The European Union and Japan (where Asahi Kasei is located) do not have such bans and treat cupro wastewater.

With so little waste coming from Asahi’s process, I don’t see any major environmental concerns with Asahi's process. I do not hold the same opinion with other companies cupro production processes. Laslty, I would love to see more research into the environmental profile and water footprint of cupro!

While the common conception is that all lyocell/Tencel is derived from eucalyptus trees, that is not accurate. Lenzing specifically, reports five species of trees in which they or their partners harvest from for Tencel production. They include, eucalyptus, beech, pine, birch and spruce. Lenzing does not specify a predominant wood species for Tencel production but they do provide a great breakdown of speicies of wood and regions grown, which you can view below. In our case, we will focus on eucalyptus as it makes up the majority of imported wood. Side note, Lenzing does an amazing job with locally sourced from Central European countries and we would consider the process more environmentally friendly compared to imported wood pulp.

Here are some quick facts about eucalyptus trees in general and eucalyptus trees sourced by Lenzing.

The Good:

Eucalyptus trees are a renewable resource. Eucalyptus trees have a relatively fast growth rate with about 60-70% of its overall height happening in the first 10 years. At Lenzing, no artificial irrigation is needed at any stage in the growth process. All eucalyptus trees used at Lenzing come from FSC plantations in South Africa. Trees grown at Lenzing’s plantation farms are done in regions with “sufficient natural moisture”Plantation farms do have the benefit of eliminating deforestation of natural forests. To conserve biodiversity, Lenzing claims that 25 percent of the plantations farmland is not grown on.

Need To Manage:

Even when rainfeed, eucalyptus trees can deplete groundwater resources and cause downstream problems to native ecosystems. The United Nations Food and Agriculture Organization found that eucalyptus plantations have a “heavy consumption of soil nutrients” and can inhibit the growth of other plants. Small amounts of natural fertilizers are used but since no irrigation occurs, the only environmental impact comes from the small amount of N2O emitted.

Overall, we think eucalyptus trees are a great renewable resource for fiber production with the major concern being water and soil conservation. As for eucalyptus plantations, as long as the company grows the trees in moisture rich regions and workswith environmental agencies to subside inevitable problems to native ecosystems, we find the impact minimal. Lenzing seems to be doing some of this work by teaming up with Canopy - a non-profit fighting to protect forests!

Pulp production is pretty straightforward and a dirty process. I will talk about water and energy usage in other sections. I want to focus this section on the bleaching process.

It all starts with elemental chlorine (Cl2). Simple put, elemental chlorine produces carcinogenic compounds and is hazardous to the environment. While it has declined over the years, it still persists in the industry and it might hold anywhere from 5-20% of the global market share. This amazes/frustrates me, as it should be zero!

On the other side of the debate we have ECF (Elemental Chlorine Free) and TCF (Totally Chlorine Free). While the name might be confusing, ECF does contain low doses of chlorine dioxide but is completely free of elemental chlorine. TCF is 100% chlorine free and uses an oxygen based process to bleach the pulp. While some environmentalist tend to side on the chlorine free method (including myself), some research identifies the environmental impact of both ECF and TCF as similar.

In studies done by the European Union, they concluded that, “it is now possible to demonstrate that the discharges to watercourses, from both ECF and TCF, are of no environmental concern”. The ECF process might even use less energy. The study did acknowledge that adsorbable organic halides (AOX), which are bad, were still present in the ECF process even after effluent treatment. However, they noted that the amount of AOX was insignificant. I did not see an examination or discussion of the problems at scale. Toxicity levels were present in both methods but at low levels. My point being, since ECF holds a market share of possibly 94%, compared to TCF which holds roughly a 5% market share, shouldn’t we think about diversifying our bleaching processes (ECF and TCF). This would minimize the effects of AOX exposure to the environment and provide more data. Oh, and we should just ban elemental chlorine outright!

Lastly, Lenzing only uses TCF bleaching in its internal processes. For all sourced imported pulop, ECF bleaching is used. Also, all by-products from Lenzing's internal pulp production process which include acetic acid, furfural, xylitol, magnesium lignosulfonate, soda (sodium carbonate), magnesium lignosulfonate, soda (sodium carbonate) are used in their biorefinery to produce energy for their plants in Czech Republic and Austria.

NMMOis the only chemical solvent used in the production of lyocell. The chemical and the effluent from the production process is considerednontoxic and easily regenerated. As we will see soon, the NMMO solution for making Tencel is 99% recyclable. Of the 1% waste, that waste can be easily treated using biological wastewater treatment methods. The effluent contains “only small amounts of organic chemicals and salt, mainly sodium sulphate”. Overall, the environmental of NMMO are considered low.

In 1991, enzymatic treatment was introduced into the lyocell process as a way to stop the filibratation on the yarn. Fibrillation leads to fuzz/pilling on the end fabric. The process is also called biopoliching. Biopolishing also gives a softer and more peach-skin feel to the end fabric. Biopolishing does provide a small loss in tensile strength but overall, it’s negligible as the final fiber has a higher tensile strength compared to other fibers like cotton. Enzymatic treatment is used in food production and is considered safe.

One of the major issues with lyocell production is energy usage. It’s inline with polyester, if not a little higher. Pulp production is specifically energy intensive. However, with plants like Lenzing's, which derived 100% of their energy needs from renewable resources, the effects on the climate start to mitigate.

The best up-to-date research on viscose production comes from Utrecht University in the Netherlands. It looked at the entire Life Cycle Assessment (energy, global warming potential, toxicity, water usage and land usage) of Lenzing’s modal, viscose, and Tencel production and compared it to conventional cotton and polyesters. The study seems pretty relevant however, some technologies have changed since the 2012 publication but I don’t think the results would vary a ton.

I will refer to one Tencel and one Modal used in the study. We will also provide research on Tencel's new Thailand facility.

Tencel Austria(From Study): Derived from a mixture of eucalyptus and beech wood. Eucalyptus is sourced from plantation farms in South Africa (see wood for more information) and European beech wood. The process uses 70% natural gas and 30% biomass for its energy demands.

Modal Austria(From Study): Derived from European hardwood that is sourced within the region. The entire production process is done at Lenzing’s Austria plant where energy demands are met by the biorefinery. Almost 100% of the energy needs are derived from renewable resources.

Tencel Thailand(Not From Study):Derived exactly the same way as Tencel #1 but it will be processed at Lenzing’s new facility in Thailand. All energy demands will come from the biorefinery, similar to Modal Austria. The majority of thebiorefineryinputs will come from black liquor or bark from pulp production and municipal solid waste incineration (MSWI).

Quick Asterisk:

The study did not look at the Tencel Thailand’s energy profile, as the plant was not built at the time of the study. However, I believe we can take the conclusions of Modal Lenzing’s energy profile and apply them to Tencel Thailand with one small change - Tencel Thailand will use a lot less caustic soda compared to Modal Austria. Refer to Tencel Austria’s caustic uses in the study.

Results:

Theoretically, Tencel Thailand will have the lowest overall energy profile compared to all regenerated fabrics, cotton and polyester. The amount of energy needed is still quite high however, the use of renewable resources and incineration of by-products derived from the production process benefit it tremendously.

All three regenerated fibers use less non-renewable energy compared to polyester while Modal Austria and Tencel Thailand use less non-renewable energy compared to cotton.

I would note that if this study was redone today, I am 100% sure all Lenzing fibers will have a better energy profile compared to the study, as Lenzing has become even more energy efficient.

I am not going to analyze the full water footprint associated with Tencel but I do want to provide some broad facts.

Total water usage for Tencel production has been reported at around 100 m3/t (Lenzing) to 263 m3/t (Utrecht University). Even at that higher amount, Tencel production uses less water compared to conventional cotton production. Lenzing claims Tencel production uses about a third less water compared to viscose and the Utrecht study found that the overall water usage to be about a 40% difference from viscose to Tencel - 445 m3/t and 263 m3/t respectively. Whatever the case, it seems to be less. The non-profit Water Footprint found that Tencel has a lower total water footprint compared to viscose. A lot of this has to do with the reuse of the NMMO solution and non-toxicity of the effluent. In regards to water footprint, Tencel has a comparatively low impact to all regenerated cellulose fibers in the Utrecht study and a significantly lower impact compared to cotton. Tencel’s biggest impact comes from pulp production with the growing of trees being a slight factor as well.

I want to leave it there as I don’t feel it’s appropriate to compare these stats to polyesters as there are so many variables. A common consensus is that lyocell has a lower impact on water footprint as fossil fuels and end of life play huge factor in polyesters total water footprint. However, the data is just not present.

The NMMO solution is 99% recyclable which keeps chemicals out of the landfill and aquatic systems.

The remaining 1% waste from the NMMO solution is easily broken down using a biological wastewater treatment.

When done correctly, the sourcing of wood can be a replenishable resource. The logging process at Lenzing is certified by either FSC or PEFC. This prevents deforestation and harmful impacts on local ecosystems.

Lenzing claims “Lyocell technology only requires one third of the process water needed in viscose technology.” It also uses less than cotton.

No matter the production process, the overall water footprint for Lenzing’s Tencel was found have a lower impact compared to both conventional cotton and polyester. Tencel produced at Lenzing’s state of the art facility provided the best water footprint.

Lyocell production is extremely energy intensive. However, Lenzing’s facility is almost entirely run by renewable resources. Specifically, wood pulp.

Lyocell holds anti-bacterial properties which should lead to fewer washes. This can potentially give lyocell huge water and energy savings over its lifecycle.

Enough said.

Because of its high crystalline structure, Tencel has a higher tensile strength when dry and wet compared cotton and other regenerated cellulose fibers.

Tencel production provides a greenhouse gas saving of about 1.5-5 times compared to cotton. At best is can save about 15-21 tonnes of CO2 per hectare.

While Tencel does use less water and the overall water footprint is better compared to other fibers, it still uses a good amount of water.

While deforestation impacts seem to be minimal in Lenzing's process, it should be worth noting that deforestation can cause major environmental harm. Look for brands/companies doing it right!

Even when done right, the cutting down of trees of any type for mass production will cause disruption to natural ecosystems.

The pulp production process is extremely energy intensive. While Lenzing’s internal facilities are run on almost 100% renewable energy, the 50% of imported pulp are not. This can be improved as renewable energy becomes more widely used.

This really depends on the climate and area where trees are grown. If topsoil is preserved, we see the impact as minimal.

As with most fiber production, chemicals used during the production process can cause environmental problems. For Tencel, caustic soda and sodium sulfide, which are used in pulp production are of concern. The environmental impact seems to be minimal but precaution to wastewater treatment is a necessity.

As you can see from the other cons, pulp production is energy demanding, uses a lot of water and can be chemically intensive.

Because lyocell has less surface energy, it does not take dyes easily. At times, more chemically intensive dyes are needed to dye the fabric. The problem can be solved by using GOTS or Oeko-Tex certified dyes.