The optical selection of plastic materials

The optical selection of plastic is an indispensable preliminary phase of the entire recycling process.

Did you know that plastics can be recycled effectively only when they are identical?

That’s right: as we mentioned in one of our articles, there are different plastic materials and each one must be adequately separated to then be recycled.

Find out with Are you R what happens during this important moment of the recycling process!

How are the materials selected?

Plastic waste must undergo a sorting process, called optical selection or ‘spectroscopy’, which separates each different material. Optical selection has the delicate but fundamental task of dividing the various types of plastic into perfectly recyclable different groups.


How does the spectroscopy work?

The plastic product is illuminated with a white light in order to allow each polymer to react differently according to the technical characteristics, reflecting a true ‘rainbow’ of colours.

This rainbow can lack one or more colours, based on the type of polymer that reflected it and therefore absorbed it. It is the task of the optical selection detection unit to verify the spectrum of colours reflected by the plastic product that passes through it, to recognize its chemical structure. In other words, the DNA of plastic!


According to the spectroscopy results for each product, then, the plastic materials are separated completely automatically thanks to a sorting machine that will be able to prepare each material for recycling.

In this video you can see the automatic selection process done by the machinery as it happens in the actual facilities.


The plastic materials ‘accepted’ by the sorting machine, based on the previously set parameters, pass the selection thanks to a jet of air that catapults them toward a conveyor belt and then toward the next recycling step.


The other materials continue their journey and by drop they are stocked in another area, where they will be taken over by the operators who will make a further selection to send each waste to its next destination.

What can you do?

Of course, having an important technology available such as the optical selection of materials facilitates the recycling process, but we consumers too can do our part, which is no less important!

Like? Paying a little more attention when we do our own recycling. For example, did you know that it is good practice to crush a plastic bottle longitudinally and not from top to bottom? This is precisely to facilitate the selection process of the different materials: if the surface of the bottle is squeezed longitudinally, the sorting machine will in fact be facilitated in identifying the material of which it is composed (PET) to send it to recycling.

A small commitment that guarantees effective recycling also thanks to our good habits!