Black plastics recycling: towards a circular economy

Reciclaje de plástico negro: hacia una economía circular

Black plastics have been notoriously difficult to detect, but recent technological developments have made it possible to sort them not only by color but also by polymer, unlocking economic value for recycling companies.

Plastic packaging serves important functions in modern life, and we have come to rely on it heavily. It is an exceptional product that, however, has a significant end-of-life problem. This is especially true of black plastic, which until very recently couldn’t be detected with the available technology, Near Infrared (NIR).

“The emitter shines a light on the material and the sensor takes a reading of the energy that is reflected back,” says Enrico Siewert, Director of Product and Market Development at STADLER. “However, carbon black absorbs the light, so the signal doesn’t bounce back and the sensor doesn’t get a reading. This means that black plastic is undetectable with the technology that is widely deployed in the recycling infrastructure.”

Why recovering black plastics matters

Black plastic makes up a significant part of household waste which, if not recovered, will be incinerated or sent to landfill. This has not only environmental implications but also financial, as Enrico Siewert explains: “If recycling companies can’t recover black plastics, they can be losing as much as 15% of the value of their inbound material. When they are able to mine this material out of the waste stream, they can create economic value and positively impact their bottom line.

Different industries involved in the plastics value chain have been researching solutions to the black plastics issue, and today there are different ways of recovering these materials. A first solution is a sensor-based dry sorting system, which uses NIR sensors with detectable black additives to detect the different types of polymers. There are also other types of sensors capable of sorting black materials, also by polymer. With this sensor-based dry sorting system, it is possible to accurately sort black polyethylene, polypropylene, PET and polystyrene.

También existe un sistema húmedo de clasificación por densidad que se basa en el principio Another solution is a wet density sorting system based on the flotation principle. The ligher polyethylene and polypropylene float, while the heavier PET, PVC and plystyrene tend to sink. The drawback of this system is that, not only is it costly due to the filtration process, the need for water, cleaning, etc., it is not capable of sorting by polymer, so that a circular process is impossible.

New opportunities for contributing to a circular economy

The ability to detect black plastics means that there will be more of them in the recycling chain. “We have to create a demand for these post-consumer black materials. Obviously, there are limitations: they can’t be used to produce white products, and they can’t always make food-grade packaging. We have to collaborate across the industry value chain to find other ways to use black plastics”.

Chemical recycling companies are an excellent example of operations that could make good use of these materials: “They are looking for polyethylene and they don’t care if it has black because they break it down into a gas and convert it into oil, which is transformed into virgin plastic – closing the loop of a circular economy.”

Black plastics processing: a demand set to continue to grow

The latest technological developments and the consumer pressure for more recycled content in packaging are bound to drive continued growth in demand for sorting plants capable of recovering all blacks out of the waste stream.

STADLER has experienced a sharp increase in the interest in these solutions and it is at the heart of this evolution in the industry: “We now have multiple partners that have developed technology to detect black plastics, so we have the ability to design systems to recover these materials tailored to our individual customers’ operational requirements and capital investment,” says Enrico Siewert. “We have completed several projects for some of the most advanced light packaging recycling plants in Europe, and we are working to develop many more.”

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