Researchers have developed a technique that converts cotton into sugar, which might then be became spandex, nylon, or ethanol.
Many of us attempt to recycle our outdated textiles, however few of us know that they’re truly very troublesome to reuse, and sometimes find yourself in landfills anyway. Now, scientists at Lund University in Sweden have developed a technique that converts cotton into sugar, that in flip may be became invaluable merchandise together with spandex, nylon, and ethanol.
It is estimated that 25 million tons of cotton textiles are discarded around the globe yearly. When you add up the differing types, a complete of 100 million tons of textiles are thrown out. In Sweden, a lot of the materials goes straight into an incinerator and turns into district heating. In different locations, it’s even worse, as outdated garments normally find yourself in landfills.
“Considering that cotton is a renewable resource, this is not particularly energy-efficient,” says Edvin Ruuth, a researcher in chemical engineering at Lund University.
“Some fabrics still have such strong fibers that they can be re-used. This is done today and could be done even more in the future. But a lot of the fabric that is discarded has fibers that are too short for re-use, and sooner or later all cotton fibers become too short for the process known as fiber regeneration.”
Where Edvin Ruuth works, on the Department of Chemical Engineering in Lund, there may be a substantial amount of collected data about utilizing micro-organisms and enzymes, amongst different issues, to rework the “tougher” carbohydrates in biomass into easier molecules. This implies that all the pieces from organic waste and black liquor to straw and wooden chips can grow to be bioethanol, biogas, and chemical substances.
Now the researchers have additionally succeeded in breaking down the plant fiber in cotton — the cellulose — into smaller elements. However, no microorganisms or enzymes are concerned this time; as an alternative, the method includes soaking the materials in sulphuric acid. The result is a clear, dark, amber-colored sugar solution.
“The secret is to find the right combination of temperature and sulphuric acid concentration,” explains Ruuth, who fine-tuned the ‘recipe’ together with doctoral student Miguel Sanchis-Sebastiá and professor Ola Wallberg.
Glucose is a very flexible molecule and has many potential uses, according to Ruuth.
“Our plan is to produce chemicals which in turn can become various types of textiles, including spandex and nylon. An alternative use could be to produce ethanol.”
From a normal sheet, they extract five liters of sugar solution, with each liter containing the equivalent of 33 sugar cubes. However, you couldn’t turn the liquid into a soft drink as it also contains corrosive sulphuric acid.
One of the challenges is to overcome the complex structure of cotton cellulose.
“What makes cotton unique is that its cellulose has a high crystallinity. This makes it difficult to break down the chemicals and reuse their components. In addition, there are a lot of surface treatment substances, dyes, and other pollutants which must be removed. And structurally, a terrycloth towel and an old pair of jeans are very different,” says Ruuth.
“Thus it is a very delicate process to find the right concentration of acid, the right number of treatment stages, and temperature.”
The concept of hydrolizing pure cotton is nothing new per se, explains Ruuth; it was discovered in the 1800s. The difficulty has been to make the process effective, economically viable, and attractive.
“Many people who tried ended up not utilizing much of the cotton, while others did better but at an unsustainable cost and environmental impact,” says Ruuth.
When he started making glucose out of fabrics a year ago, the return was a paltry three to four percent. Now he and his colleagues have reached as much as 90 percent.
Once the recipe formulation is complete, it will be both relatively simple and cheap to use.
However, for the process to become a reality, the logistics must work. There is currently no established way of managing and sorting various textiles that are not sent to ordinary clothing donation points.
Fortunately, a recycling center unlike any other in the world is currently under construction in Malmö, where clothing is sorted automatically using a sensor. Some clothing will be donated, rags can be used in industry, and textiles with sufficiently coarse fibers can become new fabrics. The rest will go to district heating.
Hopefully, the proportion of fabrics going to district heating will be significantly smaller once the technology from Lund is in place.
Reference: “Novel sustainable alternatives for the fashion industry: A method of chemically recycling waste textiles via acid hydrolysis” by Miguel Sanchis-Sebastiá, Edvin Ruuth, Lars Stigsson, Mats Galbe and Ola Wallberg, 31 December 2020, Waste Management.
DOI: 10.1016/j.wasman.2020.12.024
