Recycling technologies that make plastic sustainable

"Plastic makes our world more sustainable." This is the sentence pronounced by Markus Steilemann, CEO of Covestro. Instead, it is widely believed that plastic is one of the main causes of pollution on the planet. We read news of masses consisting of plastic that float in the oceans and is under the eyes of all the plastic waste abandoned on the land that, ingested by fish or animals, become part of the human food chain.

But here is the real point of the question: don't let plastic become waste.

The essential role of plastic in sustainability

Plastic is the material of our time. Its ductility, malleability and lightness allow you to create safe, light and low-consumption means of locomotion. Plastic creates biomedical devices that save lives every day. Every object that improves daily life, increases the efficiency of buildings, makes our cities more livable, has polymeric components inside.

Only if you design products with a view to the circular economy can you turn waste into a resource? The circular economy teaches us to design a product thinking first of all about what we can do with this object when we will no longer use it.

Innovative recycling: getting to recover all plastic products

At the end of its life, plastic should not become waste but should be recycled and return to being a valuable raw material. In this sense, disposal systems and recycling technologies are making huge strides.

Mechanical recycling of plastic

The best known and most widespread method is mechanical recycling. It is estimated that in Europe 99% of the recovered plastic is subjected to this type of recovery. It is one of the simplest ways for the enhancement of thermoplastic polymers. It is a method that implies minimum work ability requirements of the material and in which the ownership of the products obtained will be highly dependent on the quality of the selection made on the product to be recycled.

Homogeneous recycling

In this type of plastic recovery, the selection process that takes place upstream of the entire waste processing process is very important to obtain increasingly "cleaner" fractions of homogeneous materials. The selection of the material is achieved with different separation processes including:

• magnetic or electrostatic
• by flotation or by density
• with floating
• with a sieve by blowing air.

Once separated, the different polymers are sent to the next stages of shredding, washing, grinding, drying and reduction in granules.

Heterogeneous recycling

When it is not possible to make a selection of the plastic waste, it is possible to proceed with a mixed material processing such as polythene or polypropylene films, cans, trays and PVC cans. In this case, we proceed with a selection to eliminate metallic material and then the recycling proceeds according to four phases: shredding, coarse crushing of the material - extrusion. The difficulties present in heterogeneous recycling are linked to the different processing temperatures of the mixed polymers. This excludes the possibility of use for the production of products with a complex shape or requiring small thicknesses.

Depending on the type of plastic waste recovered, it is possible to obtain thermoplastic polymers ground in granules or flakes to be used in the production of new products or which integrate virgin polymers or even fillers for other products because they are no longer workable. Mechanical recycling often implies a devaluation of the raw material that no longer has the same characteristics as the virgin one.

Advanced chemical recycling of plastic polymers

The best way to bring plastic waste back to life is through chemical recovery. An innovative and high-tech way that is channeling the efforts of researchers and companies.

The plastic waste is subjected to a series of chemical processes which decompose the polymer into the original monomers. Due to their chemical nature, some plastics lend themselves better to this treatment. This is the case of PET (polythene terephthalate), PA polyamides, commonly called nylon, and polyurethanes: all these materials can be effectively depolymerized. The chemical decomposition processes, unlike the mechanical ones, also allow isolating the components extraneous to the polymer: dyes, metals, impurities are removed and a virgin plastic is obtained which is indistinguishable from the new one. With chemical recycling, elements that previously underwent a down cycle, that is, were destined for lower value products, can be transformed into high-quality raw material and therefore can be recycled indefinitely without loss of quality or performance.

• With innovative chemical processes, all plastic waste can be subjected to chemical recycling through different processes that transform them into mixtures of liquid hydrocarbons with absolutely the same value as the raw material. Among the main processes there are: pyrolysis: vacuum heating at high or low temperature
• hydrogenation: degradation treatment with hydrogen and heat
• gasification: high-temperature process in the absence of air.

The most important solutions are those that are allowing the recovery of the polythene film. Polythene is the most produced plastic, over 100 million tons per year, but has a recycling rate that is less than 10%. Recovering polythene means recovering that huge amount of plastic that is indispensable for our daily life: bags, packaging, wrappers for pallets, films used in agriculture and much more. Thanks to chemical recycling, even plastic waste can be transformed into a raw material with dyes and inks or with labels and adhesives.

Working together for innovative waste recovery

Giving value to waste is a complex technology that can be realized only if all the subjects of the productive and social world work together. The chemical industry plays a leading role in this recovery process. Covestro is working in all possible directions to push the pedal of innovation and sustainable development with over 20 research projects and many initiatives to promote giving voice to new ideas and young people. Partnerships with university research centers or participation in producer associations, such as the Pure Smart consortium which unites nine partners from six European countries, are heading in the same direction. The project financed with 6 million euros by the European Union realizes the treatment of polyurethane and removes 220,000 tons of PU foam from landfills.

On June 25, 2020, Markus Steilemann, on the occasion of his appointment as president of Plastic Europe, which brings together over 100 plastic manufacturers, said he wanted to use:

the greatest possible effort to make the circular economy a reality. To ensure that people can say with great confidence now and in the future: 'Plastic makes our world more sustainable'.