Environment

Recycling process pulls "virgin-standard" polypropylene from carpets

Recycling process pulls "virgi...
Cleaned and shredded carpet waste, prior to the solvent treatment
Cleaned and shredded carpet waste, prior to the solvent treatment
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Cleaned and shredded carpet waste, prior to the solvent treatment
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Cleaned and shredded carpet waste, prior to the solvent treatment
"Ultra-pure" polypropylene harvested from carpets in a lab-scale version of the process
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"Ultra-pure" polypropylene harvested from carpets in a lab-scale version of the process

Discarded carpets inevitably take up a lot of space in landfills, or create a great deal of smoke when incinerated. Soon, however, it may be possible to recover high-grade polypropylene from synthetic carpets that would otherwise just end up in the dump.

The new recycling process is being developed by scientists at Germany's Fraunhofer Institute for Building Physics, as part of the European Union ISOPREP project.

It begins with a discarded carpet being cleaned, which involves removing as much of the backing as possible. The remaining material is then shredded, mixed with a proprietary ionic liquid solvent (a liquified salt, in other words), and placed inside a reactor chamber. Within that reactor, the polypropylene is dissolved out of the carpet fibers and into the solvent, leaving impurities such as dyes behind.

In a subsequent step, the polypropylene is separated from the solvent, most of which can be reused. The harvested polypropylene is described as being "virgin-standard," meaning that it could be utilized in the production of high-quality products – by contrast, many recycled plastics are limited to use in lower-quality goods.

"Ultra-pure" polypropylene harvested from carpets in a lab-scale version of the process
"Ultra-pure" polypropylene harvested from carpets in a lab-scale version of the process

The scientists are now working on maximizing the amount of solvent that can be reused (as it is rather expensive), and keeping energy requirements and greenhouse gas emissions to a minimum. "If loss rates can be kept to one percent or less, there is potential for the costs of the process to rival those of producing new polypropylene," says Fraunhofer researcher Maike Illner.

Plans call for the process to be trialled in a pilot plant, which should begin recycling 1 ton (0.9 tonnes) of carpet waste per day as of next March. The technology could conceivably also be applied to other types of polypropylene-containing waste.

Source: Fraunhofer

3 comments
3 comments
CarolynFarstrider
Promising, but needs a full life cycle analysis to be credible.
GeoffreyR.Gunning
Hope it works. I was involved in the plastics recycling movement in the 90's using XRF to separate PVC from PET from bottles. A difficult task due to all the waste plastics being co-mingled. Ultimately it became an engineering problem to debale & "singulate" each one. Wellman bought several of our systems. Now we see trucks of plastic waste in India & Bangladesh being poured into rivers, negating all our work.
Karmudjun
Chemists understand their analysis but the term "virgin-standard" has little meaning outside of the plastic manufacturing industry. But if it proves to be an unworkable solution to polypropylene rich waste stream, at least this is a sign of continued advancement in the plastic recycling technology. Scientific advancements - when repeatable - are always credible and prove valuable - if not today due to economies of scale or cheaper alternatives - one day the knowledge will be prove useful as history has shown time and again.