Three inputs—ammonium bicarbonate, a non-toxic solvent and heat—promise to revolutionise sustainability in the apparel industry by depolymerising polyester and simultaneously recovering cotton on a scale of hundreds of grams.
- In what could be a game-changing research, a bunch of young chemists from Europe have come up with a traceless, environmentally friendly and practical approach for polyester recycling and cotton recovery, representing a significant step toward sustainable, closed-loop production and textiles.
THE STUDY: The research was conducted by Yang Yang, Shriaya Sharma, Carlo di Bernardo, Rodrigo Lima, Fadhil S. Kamounah, Margarita Poderyte and Ji-Woong Lee from the Department of Chemistry at the University of Copenhagen, Denmark; Elisa Rossi and Gianluca Ciancaleoni from Università di Pisa, Italy and Kasper Enemark-Rasmussen from DTU Chemistry, Denmark.
- The research article has been published in the journal ACS Sustainable Chemistry & Engineering.
- The new recycling method based on hartshorn salt (ammonium bicarbonate) works on PET plastic as also PET and cotton blended materials.
HOW IT WORKS: In a simple and cost-effective process, take a polyester dress, cut it up into small pieces and place it in a container. Then, add a bit of mild solvent, and thereafter hartshorn salt, which many people know as a leavening agent in baked goods.
- Then heat it all up to 160 degrees Celsius and leave it for 24 hours. The result is a liquid in which the plastic and cotton fibres settle into distinct layers.
- In the process, the hartshorn salt, also called ammonium bicarbonate, is broken down into ammonia, CO2 and water.
- The combination of ammonia and CO2 acts as a catalyst, triggering a selective depolymerisation reaction that breaks down the polyester while preserving the cotton fibres.
- Although ammonia is toxic in isolation, when combined with CO2, it becomes both environment-friendly and safe for use.
- Due to the mild nature of the chemicals involved, the cotton fibres remain intact and in excellent condition.
- While the method has only been tested at the laboratory level thus far, the researchers point to its scalability and are now in contact with companies to test the method on an industrial scale.
WHAT THEY SAID:
With our newly discovered technique, we can depolymerize polyester into its monomers while simultaneously recovering cotton on a scale of hundreds of grams, using an incredibly straightforward and environmentally friendly approach. This traceless catalytic methodology could be the game-changer.
— Yang Yang (Lead Author)
Post-doc, Department of Chemistry
University of Copenhagen
At first, we were excited to see it work so well on the PET bottles alone. Then, when we discovered that it worked on polyester fabric as well, we were just ecstatic. It was indescribable. That it was so simple to perform was nearly too good to be true.
— Carlo Di Bernardo (Co-Author)
Doctoral student, Department of Chemistry
University of Copenhagen
