Converting Recycled Textiles Into Sugar Will Become Valuable Products

Many of us are trying to recycle old textiles, but few of us know that they are actually very difficult to reuse and will end up in landfills anyway. Now scientists at Lund University in Sweden have developed a way to convert cotton into sugar, which in turn can be converted into valuable products including spandex, nylon and ethanol.

It is estimated that 25 million tons of cotton textiles are discarded every year around the world. If the different types are added up, a total of 100 million tons of textiles are discarded. In Sweden, most of the material goes directly into the incinerator to provide district heating. In other places, it's even worse because old clothes usually end up in landfills.

"Given that cotton is a renewable resource, it's not particularly energy efficient," said Edwin ruuth, a researcher in chemical engineering at Lund University, "Some fabrics still have such strong fibers that they can be reused. It is done today, and more may be done in the future. But many of the discarded fabrics are too short to be reused, and all cotton fibers will become too short sooner or later to undergo a process called fiber regeneration."

The Department of chemical engineering in Lund, where Edwin ruuth works, has accumulated a lot of knowledge about the use of microorganisms and enzymes to convert "harder" carbohydrates in biomass into simpler molecules. This means that everything from biological waste and black liquor to straw and sawdust can be bioethanol, biogas and chemicals.

Now, researchers have also succeeded in breaking down the plant fiber in cotton, cellulose, into smaller components. However, no microorganism or enzyme was involved this time; Instead, the process involves soaking the fabric in sulfuric acid. The result is a transparent, dark, amber sugar solution.

"The secret is to find the right combination of temperature and sulfuric acid concentration," ruuth said. It is understood that he worked with Miguel Sanchis Sebasti á, a doctoral student, and Ola Wallberg, a professor, to fine tune the "formula".

Ruuth says glucose is a very flexible molecule and has many potential uses. "Our plan is to produce chemicals, which in turn can become various types of textiles, including spandex and nylon. Another use could be ethanol."

From an ordinary sheet, they extracted 5 liters of sugar solution, each liter containing the equivalent of 33 pieces of sugar. However, you can't turn this liquid into a soft drink because it also contains corrosive sulfuric acid.

One of the challenges is to overcome the complex structure of cotton cellulose.

In addition, it's very different from the fabric of the cotton towel that it's very different from the fabric of the old towel, and it's very difficult to get rid of the fabric from the fabric, and it's very different from the fabric of the cotton towel, "Therefore, finding the right acid concentration, the right number of treatment stages and temperature is a very delicate process."

Ruuth said the concept of hydrolyzing pure cotton is not new in itself, it was discovered as early as the 19th century. The difficulty is how to make the process effective, economically viable and attractive.

"Many of the people who tried didn't use a lot of cotton in the end, while others did better, but the costs and environmental impact were unsustainable," ruuth said

When he started making glucose out of fabric a year ago, the returns were paltry three to four percent. Now he and his colleagues are up to 90 percent.

Once the formula is completed, it will become relatively simple and cheap to use.

However, to make this process a reality, logistics must play a role. At present, there is no established method to manage and sort various textiles that are not sent to general clothing donation sites.

Fortunately, a recycling center is being built in Malmo, unlike anywhere else in the world, where sensors are used to automatically classify clothes. Some clothes will be donated, rags can be used for industry, and textiles thick enough to be made into new fabrics, and the rest will be used for district heating.