Black plastics recycling: towards a circular economy

Photo: Stadler

This is a turning point in the rapidly developing plastic packaging sector. Stadler is seeing increasing demand for systems that can recover all black plastic from the waste stream. A financially and ecologically advantageous circular economy is possible through effective cooperation of all actors in the value chain of the industry.

Plastic packaging performs important functions in modern life and we rely heavily on it. It’s an exceptional product, but it has a significant end-of-life issue. This is especially true for black plastic, which until recently could not be detected with available near-infrared (NIR) technology. “The emitter illuminates the material and the sensor measures the energy reflected back,” says Enrico Siewert, Head of Product and Market Development at Stadler. “However, soot absorbs the light so that the signal is not reflected and the sensor does not get a reading. This means that black plastic is undetectable with technology that is widely used in recycling infrastructure.”

Why black plastic recovery is important

Black plastic accounts for a significant portion of household waste which, if not recovered, is incinerated or sent to landfill. This has not only environmental but also financial implications, as Enrico Siewert explains: “If recyclers cannot recover black plastic, they can lose up to 15% of the value of their incoming material. If they are able to remove this material from the waste stream, they can create economic value and have a positive impact on their bottom line.”

“Another important consideration is that more and more packaging is made of black plastic as more recycled material is used. When recycling post-consumer packaging, if it is not sorted strictly by color, the result is a gray resin. This cannot be traced back to white, so many fabricators add carbon black to get a very even, more pleasing color. We as a society want more recycled material, we will see more and more black material in the waste stream. As a result, packaging will continue to trend toward darker colors.”

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A groundbreaking technological development

Various industries involved in the plastics value chain have been looking for solutions to the black plastics problem and today there are various ways to recover these materials. A first solution is a sensor-based dry sorting system that uses NIR sensors with detectable black additives to identify the different types of polymers. There are other types of sensors that can sort black materials, including by polymer. With this sensor-based dry sorting system it is possible to sort black polyethylene, polypropylene, PET and polystyrene accurately.

Another solution is wet density sorting based on the flotation principle. The lighter polyethylene and polypropylene float while the heavier PET, PVC and polystyrene tend to sink. The downside of this system is that not only is it costly due to the filtration process, water needs, cleaning, etc., but it also lacks the ability to sort by polymer, so cyclical processing is not possible.

“The greatest progress, however, was in the sensors,” says Enrico Siewert. “The situation has evolved to such an extent that today we are able to separate black not only by color but also by polymer. This is very important because if the sorter ejects all the black materials together, there could be up to 15 different polymers in the mix that cannot be easily recycled.”

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“This is a very recent development: 5-6 years for black color detection and polymer sorting. This is a real game changer as it creates economic value and makes it possible to recycle those materials that would otherwise end up in landfill or incineration.”

New ways to contribute to a circular economy

The ability to detect black plastic means there will be more of it in the recycling chain. “We need to create demand for these black post-consumer materials. Obviously there are limitations: they can’t be used to make white products, and they can’t always make food-grade packaging. We need to work together across the industry value chain to find other ways to use black plastics. It won’t necessarily be for consumer oriented products, but they could be used to craft items like pallets, buckets, or railroad ties, etc. It’s about effectively sorting the plastic and making it available as a feedstock for the advanced recycling sector.”

Chemical recyclers are a great example of operations that could put these materials to good use: “They look for polyethylene and they don’t care if it’s black because they break it down into gas and turn it into oil, which gets turned into virgin plastic – the cycle of a circular economy is closed.”

It is also important to extend this cross-industry collaboration to packaging designers and manufacturers. “We need a conversation between manufacturers and recyclers, in which they jointly consider things like: Does the consumer really need or want black packaging? What is most important to the consumer if the material cannot be recovered? Do they want a close-loop solution for the package they buy, or do they care more about how it looks? Such an approach will help address the black plastic problem and achieve better valorization of the waste stream.”

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Processing of black plastics: a demand that will continue to grow

Recent technological developments and consumer pressure for more recycled content in packaging will inevitably result in continued growth in the demand for sorting equipment capable of recovering all black matter from the waste stream.

Stadler has noticed a sharp increase in interest in these solutions and is at the center of this development in the industry: “We now have several partners who have developed technologies to detect black plastics, so we are able to develop systems for the recovery of these materials , tailored to the operational requirements and capital investments of our individual customers,” says Enrico Siewert. “We have completed several projects for some of the most advanced lightweight packaging recycling plants in Europe and are developing many more.”

“The demand for this technology is extremely high and I see this trend continuing in the future. More black plastic is entering the waste stream and the technology to break down these materials is catching up fast,” concludes Enrico Siewert.

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