Plastic recycling is the means by which waste plastic is recovered and reprocessed into useful products. Here is a general overview of how plastic is recycled. From collection and sorting, to cleaning and shredding as well as to melting, filtering and reprocessing.
Collection
The first step in the recycling process is the collection of plastic waste. This comes from various sources such as households, commercial establishments or manufacturing facilities.
Plastic can be collected from the curbside, or individuals can drop off their plastic waste at a collection point. Volunteers and specific organisations also collect waste from beaches, shorelines and waterways in an effort to reduce plastic pollution. Plastic waste that has been discarded or blown onto streets and pavements is collected by road sweepers.
Sorting
Once collected, the plastic waste is then sorted based on type and colour. This is really important as different types of plastics have different chemical properties and require specific recycling methods.
Common methods of plastic sorting include:
- Manual inspection – Workers at a recycling facility sort plastic items based on their shape, colour and markings.
- Automated sorting – Machines use sensors and optical scanners to sort plastic by colour, shape and size.
- Magnetic sorting – Magnetic fields separate magnetic plastics, such as those made from PET or HDPE, from non-magnetic plastics.
- Density sorting – Water, air or other liquids are used to separate rigid plastics, such as those made from HDPE (e.g. shampoo bottles), from more flexible plastics, such as those made from LDPE (e.g. milk bottles).
- Near-infrared sorting – This method uses near-infrared technology to detect the chemical properties of different plastics and then sorts them accordingly.
- Sink-float separation – A water bath separates plastics based on their density, with rigid plastics sinking to the bottom and more flexible ones floating on top.
Cleaning
After sorting, the plastic waste is washed and cleaned to remove any contaminants or impurities that could compromise the quality of the recycled material.
The first step is to remove any non-plastic materials – such as paper, food or metal – from the plastic stream.
The items are then washed using water, detergents and specific cleaning agents to remove dirt, food residue and other contaminants.
Shredding
After washing, the plastic is then shredded into small pieces to improve the efficiency of cleaning and drying.
This process may involve granulators, hammer mills, shredders or grinders – depending on the type and quantity of the plastic. Regardless of the method used, plastic shredding is a critical step in recycling as it helps to break down plastic into smaller pieces that can be more easily processed and turned into new products.
Melting and filtering
The plastic is then melted down into a liquid form, which can be moulded or extruded into new products.
The next stage is to filter the plastic to remove any contaminants or impurities that may be present.
The molten plastic is then cooled and solidified into pellets or beads.
Reprocessing
The recycled plastic pellets are now ready to be used as raw material in the production of new products. The manufacturing processes for this purpose include injection moulding, extrusion and blow moulding.
It’s important to be aware that not all types of plastic can be recycled, and even those that can be recycled may have limitations due to their quality or contamination. Additionally, recycling plastic does not eliminate the need for reducing plastic waste and using sustainable alternatives to plastic.
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