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Sorting and Processing
The commissioning of a recycling plant entails substantial capital investment while the economics of sustainable recycling require high collection volumes in order to contain costs through economies of scale. However, the process – the PET Flow – is easy to understand and can be represented in a simple schematic :
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| Collection : Discarded PET bottles are purchased from buy - back centres, collecters and municipal drop-off centres, baled and delivered to the recycling plant. |
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| At the recycler the collected bottles are sorted according to colour and polymer, de-labelled (where possible) and the caps and rings are removed, which are generally manufactured from polypropylene for which there is a demand in South Africa, so they get recycled too. |
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| Washing : The bottles are washed to remove any residual surface contamination as well as any incompatible polymers that float in water through a float/sink process. PET is heavier than water and will sink; any other residual material floats to the top of the tank and is separated out. In the PET washing process, caps or labels manufactured from polypropylene (PP) or high-density polyethylene (HDPE) will float and can be easily removed. |
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| Shredding : The bottles flow from the washing machine into a granulator where they are shredded and reduced to flakes before being screened. Flakes are dried and stored in silos before being conveyed to a cutter-compactor and extruder creating spaghetti like threads (shown above). |
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| After cooling and drying, the pellets are stored in jumbo bags until required as a raw material ready to be used in the manufacture of new products. |
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| The finished product, minute clear PET pellets, called Recycled PET or rPET, is sold to end markets and can be developed into various plastic products, such as fibre for duvets, pillows and sleeping bags, carpets, clothing or filling for jackets and quilts. The thin plastic has good insulation properties and is also used for roof insulation. 2010 will see rPET material being used to make PET containers. This is known as "Bottle 2 Bottle" recycling. |
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