Wednesday, March 31, 2021
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Old cotton fabrics can become ethanol

Most textiles that are thrown away in Sweden are not completely worn out, almost 60 percent could have gone to second hand instead. The clothes that are actually so broken that they can no longer be used are usually not recycled but are burned up and become district heating, according to the Swedish Environmental Protection Agency.

Old technology, now with increased returns

A research group at Lund University has used a technology that has existed since the 19th century to chemically recycle cotton textiles. They have now succeeded in getting higher yields, as much as 90 percent glucose, ie sugar.

The cotton found in our clothes is a natural fiber and consists almost exclusively of cellulose. Cellulose in turn is a long chain of linked sugar molecules, that chain is extremely durable. By breaking down the chain, you get out glucose, which can then be built up to something else. For example, the fabrics spandex and nylon, or ethanol.

– Glucose can be used for almost anything. Among the easiest things would have been to make ethanol from it and create vehicle fuel, says Ola Wallberg, professor of chemical engineering and project leader.

The sulfuric acid starts the process

The technology is such that sulfuric acid acts as a catalyst to break down the cotton into its components. Then the decomposed components are mixed with water and the solution is placed in a pressure cooker. Then the cotton is completely dissolved. The end result is a high concentration glucose solution.

– What we optimize is the relationship between temperature and acidity in the two steps to get as high a sugar concentration as possible, says Ola Wallberg.

One last step in the recycling ladder

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When something is to be recycled, the process is usually divided into different steps. The lowest step is the one that requires the least energy, usually reuse, such as when an old glass jar becomes a pen stand. The more energy that is used in the recycling process, the higher you get up the stairs.

Ola Wallberg is careful to point out that this method is one of the top steps.

– The first step is that we should avoid throwing away well-functioning clothes. The second is that if we are to get rid of clothes, we will get them to a second-hand market and not to incineration, he says.

But when our clothes and textiles are so broken that they can no longer be used, this technology may in the future make it possible to use the cotton molecules again before they go to incineration.

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Want to see more about how we can turn old clothes into new ones? See The World of Science – E-commerce: The shopping of the future on Monday 29 March at 20.00 on SVT2 or on SVT Play .

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