RECYCLING, A FOUR-STAGE PROCESS
THE LIVES OF PLASTICS
The compacted bales of PET that come from the sorting centre are taken to a recycling plant, where they are transformed into secondary raw material.
Stage one: The containers are opened and visible foreign or unsuitable objects are removed: metal wire, pieces of tin cans or fragments of labels.
Stage two: the labels are removed and the bottles are sorted for the first time. They are washed in hot water in order to remove the labels and glue, and then they are sent to an optical sensor that detects unsuitable colours and bottles that are not made of PET. They might also be subjected to a visual and manual sorting process.
Stage three: the bottles, lids and pull-tabs are crushed. The flakes produced by shredding two different plastics – PET bottles, high-density polyethylene from the HDPE lids – are put inside a sink-float tank, where they separate (high-density polyethylene is lighter and floats).
Stage four: the flakes are dried and packaged, and a sample is taken to be analysed in a laboratory.
The water used for washing the bottles is treated so it can be reused, thus closing another important recycling process for the environment.
SELECTING THE PLASTIC
The plastic material obtained from selective waste collection is taken to sorting centres.
The first step is to remove irrelevant plastic items, such as large objects, anything that is either not made of plastic or made of non-recyclable plastic. Certain obvious items (bags, pipes, chairs, sunshades) are removed before entering the facilities.
Then the articles enter a conveyor belt, where they are checked again and any foreign body is removed. Only certain products are sent to the landfill site, while others, such as fruit crates, are recovered in each type of plastic.
After the unsuitable objects have been removed, the material is sorted by size, getting rid of the smallest and lightest pieces first. A rotary screen removes small pieces and separates types of bottles (water, soft drink, detergent bottles, etc.). A second screening machine separates flat elements (films) and those with hollow parts (bottles, cans).
This stage mainly recovers a mixture of films.
The material from which small, light particles and films have been removed reaches a third stage, where the PET is separated from metals and other bottles. Metals are extracted from the flow of materials by means of a magnet and an eddy current conveyor belt for non-ferrous metals (aluminium). An optical sensor separates PET bottles from the others. The purpose of this stage is to recover metals (iron and aluminium), high-density polyethylene (HDPE) and low-density polyethylene (LDPE).
We now have a mixture of PET bottles. During stage four, the PET is sorted by colour using an optical sensor; at this point, the material is only made up of PET bottles. Stage four consists in identifying and separating light coloured PET.
This stage recovers coloured PET, blue PET and transparent PET.
Consequently, sorting centres produce compacted bales of transparent (colourless) PET, blue PET, coloured PET, metals (iron and aluminium), a mixture of polyolefins, a mixture of films, HDPE, LDPE, PE / PP (plastic boxes).
On average, a tonne of collected material recovers: 270 kg of PET for liquids, 100 kg of PE for flexible containers, 90 kg of high-density polyethylene detergent bottles, 20 kg of PE/PP for fruit and vegetable crates, 220 kg of a mixture of different plastics.
The DEMETO project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 768573.
A project co-funded by the Ministry of Industry, Energy and Tourism in the grants awarded for the 2012 Re-industrialisation Programme and ERDF Operational Programme, Autonomous Region of Valencia 2007-2013 (PET COMPAÑÍA PARA SU RECICLADO, SA. A programme for implementing new technologies and processes in order to modernise the company. File no.: REI-040000-2012-61)
PET COMPAÑÍA PARA SU RECICLADO, SAU
Polígono Industrial La Pahilla
El Blanquizar S/N
46370 Chiva (Valencia) – Spain
Tel.: +34 962 524 148
Fax: +34 962 524 259