Environmental issues are fast becoming increasingly important as humans come to terms with their impact upon the planet. One major topic of concern is our heavy reliance on plastic products, and we are encouraged to recycle as much of it as possible. But when we toss that plastic bottle into the recycling bin, what actually happens to it?
Well, to help you out, here’s a quick guide to the process:
Collection of waste plastic.
Firstly, the waste plastic needs to be collected. Sounds simple, right? But then, if the plastic is not in the correct place it won’t be collected at all. It is down to each individual, organisation or business to ensure that plastic is placed separately from other, non-recyclable waste, or it will not be collected and recycled. In all probability, this will end up in a landfill site, which, if we have any concern for our planet, is the very last thing we want..
It is also the responsibility of the government to provide a reliable service that encourages us to recycle, whether through regular roadside collections or by providing convenient collection points to enable us to drop off our plastic waste.
Once the waste plastic reaches the recycling centre it has to be sorted. This is undertaken for several reasons and initially involves separating them by colour and type. You will probably have noticed that the plastic containers you use at home have different letters on them, such as PET/E or HDPE? There are several of these, each one relating to a different type of plastic, depending on its makeup and method of production. These have to be separated at this stage as they must not be recycled together. Mixing different types may result in structural defects and weakness in the final product that may render entire batches useless. The different plastics are manufactured using a range of techniques, and therefore require different treatment at the recycling stages. Most sorting is undertaken by machines but at some point a more intensive, manual examination may be required to ensure that all contaminants are removed.
You probably rinse out your bottles and packets before recycling them, but many people do not, unfortunately. When the plastic has been successfully sorted into the correct types, it must be washed to remove any trace of substances that might affect the recycling process and therefore the quality of the end product. All traces of organic or non-recyclable material must be washed away, as well as any labels or glue, before the plastic is dried thoroughly prior to the next stage.
In order to simplify the process of recycling, once it has been sorted and thoroughly washed the different types of plastic are broken down into tiny fragments by passing them through an industrial shredder. Reducing them in size not only makes them easier to handle and transport, it also allows another check for any contaminants like metal shards which are often extracted using magnets and/or metal detectors.
Secondary identification and sorting.
Yes, that’s right – the tiny pieces will now be identified and sorted into different types again! It might seem counter-productive to wait until this stage, but there are some simple and effective methods of doing this, made all the easier due to the small size of the fragments. This is essential for the purpose of sorting them according to their quality.
The first method is to place the batch in a water tank, allowing denser fragments to sink and lighter ones to float. Similarly, the pieces are placed within a small-scale wind tunnel. The lighter the fragments, the further they will be blown down the tunnel, enabling them to be separated easily.
Batches will often also be tested for their melting point and precise colouration through more scientific methods of analysis at this stage.
Having been successfully collected, sorted, washed, shredded, identified and re-sorted, the plastic fragments will now be melted into small pellets.
These pellets are then sold to companies who will transport them to their own facilities in order to produce plastic items to suit their own business needs.
The bottle you placed in your recycling bin at the start has now been through the full cycle and is once more on the shelf, where it will be bought and, hopefully, recycled again.