A team of researchers, including from Fraunhofer IBP, has now developed a new recycling process as part of an EU project named ISOPREP. "For the first time, this is making it possible to recover polypropylene from carpet waste — and the outcome is virgin-quality," says Maike Illner, a researcher at Fraunhofer IBP. Not only does this allow the recovered polypropylene to be used in lower-quality products (in a process known as downcycling), but it also means that the quality is similar to that of newly manufactured polypropylene, making the material suitable for high-quality products too.
The process is based on a special solvent in the form of an ionic liquid. With the right components, it is able to selectively extract polypropylene from carpet fibers. Before the team of experts applies the solvent, the carpet waste is cleaned — something which involves removing as much of the backing as possible — and broken down. Once the pretreatment is complete, the waste is fed into a reactor in which it undergoes treatment using the solvent. The polypropylene is selectively dissolved in the solvent, a method that provides an effective way of removing dyes and other additives. The process is already being used on an extensive laboratory scale involving several liters of the solvent — and now, the research consortium has set its sights on scaling the process up to a pilot plant with the ability to recycle a ton of carpet waste per day. The pilot plant is set to commence operation by the end of the project in March 2022.