Last week I started the “On habitats” series to take a moment and reflect on where the fiber in our yarn comes from. Part One of this series looked at Natural Plant Fibers, which brings us to part two: Synthetic Plant Fibers. These include tencel, bamboo, corn, soy, rayon, and modal. In the interest of keeping these posts readable, I’m going to focus on tencel, bamboo, and corn this week.
Tencel (Lyocell): Tencel is derived from the cellulose of hardwood trees. The trees are logged and trucked to a mill where they are cut, debarked and fed to a chipper. The hardwood chips are then turned into a pulp through the assistance of chemical digesters, which is then washed (and sometimes bleached). After the pulp is washed, it’s layed out in a large sheet and left to dry. Once dry, the sheets are rolled onto a large spool.
Next, spools are unrolled and broken into one-inch squares so that they can be loaded into a heated pressurized vessel filled with amine oxide. After a short time in this solvent, the cellulose dissolves into a clear solution and is pumped through a filter to ensure that all of the chips have been dissolved. From here, fibers are pumped through a spinneret, which leads to the creation of long strands of fiber. These strands of fiber are then immersed in a diluted solution of amine oxide (this sets the strands) and washed in demineralized water. Fibers are then lubricated (detangled), allowed to dry, run through a crimper and then carded. Once carded, they are ready to be spun.
The amine oxide solvent is non-toxic and is almost completely recycled during manufacturing, so it is not released into the environment. Additionally, the principal ingredient in this yarn is obtained by managed tree farms (no deforestation), the process uses less water and energy when compared to other manmade fibers and tencel (lyocell) is naturally biodegradable.
Bamboo: There are two methods that can be used to get bamboo fiber: mechanical and chemical. The mechanical method involves crushing the plants into a mush and using natural enzymes to break it down before spinning it into yarn. This method is labor-intensive (expensive) and the fiber produced is not very soft.
The chemical method, a “chemical cocktail”, contains primarily sodium hydroxide and carbon disulfide — both are known to be bad for human health and are harmful to aquatic life when released into the water supply — which produces a very soft fiber (ie the fiber used to make bamboo underwear). While companies claim this a minute part of the process, a factory producing a lot of bamboo fiber/fabric will expose their workers and the environment.
Although Bamboo itself is a sustainable resource, there is a lack of transparency and true sustainability — the soil association has not certified bamboo at this time. In addition to the process of turning bamboo into a fiber, there are concerns around it becoming a mono-crop grown only in China. This is leading to a decrease in biodiversity and an increase in pests (more pesticide needs to be used).
Corn: Corn is grown worldwide and used for food and fuel, leaving behind the husks as farm waste. These husks contain a fiber called lignocellulose which is soft and strong. Lignocellulose is separated from the husk via a patented biochemical process. This biochemical process contains common non-toxic chemicals (acetic acid, sodium chloride, sodium hydroxide, surfactants, and softeners) and is combined with water in a rotator for about a half-hour. The clumps of coarse fibers are then washed (with water) and dried before another biochemical treatment is applied to reduce the diameter of the fiber strands. Finally, the fibers are bleached, dyed and spun into yarn.
The downside? A lot of corn is genetically modified, which unfortunately means that something in the pollen is interfering with the monarch butterfly’s breeding cycle. Interesting. Essentially, while the corn fiber itself is not terrible for the environment, there are a lot of aspects (mono crop, etc) of the farming process that is.
Main Takeaways: I poked around and there isn’t a lot of corn yarn on the market yet, it looks like this could be a growing trend if the demand for the fiber increases. In terms of tencel; I don’t mind it in blends, but have not worked with a pure tencel fiber before. That being said, it’s nice to know that even though the fiber is manmade from a tree (which is a little mind-blowing) the process is both sustainable and eco-friendly. As for bamboo… I think I’m going to have to pay attention to what happens in the industry and abstain from using bamboo yarns for a little while. While I enjoy the way bamboo takes dye, I find it hard to support an industry that doesn’t have a problem exposing their employees to harsh conditions.
Stay tuned for synthetic plant fibers part two (soy, rayon, modal, and ramie), coming next week!