Step 1: Collection
This step is completely reliant upon businesses, restaurants, and the public to dispose of their plastic waste in the correct place. If plastic waste is disposed of in normal trash bins, it will not be recycled, so it is extremely important to separate common waste and plastic waste.
Additionally, it is ideal for governments to have a recycling collection system that goes to people's houses or businesses to collect the plastic waste. If this is not possible, local collection points for plastic should be easy for the public to access. Making it easy and convenient for people to correctly dispose of plastic waste is paramount in promoting recycling .
Step 2: Sorting
After plastics are collected and transported to a recycling facility, the next step is sorting.
Machines sort plastics into different areas based upon a multitude of properties that are often dependent upon the recycling facility or what final product is being produced.
Plastics are usually sorted in a few common ways, such as the type of plastic (material it is made with), color of the plastic, or even how it was made. This is important because different types of plastics must be processed in different ways and some recycling facilities are only capable of recycling one type of plastic. If the wrong type of plastic is processed at the incorrect facility it can reduce the efficiency of the whole process and require the entire batch to be sent back again for resorting [1,2].
Step 3: Washing
Just like with clothes, fruits/vegetables, and many other things, plastics must be washed before they are further processed. The goal of this step is to remove impurities and everything that is not made from plastic.
Most containers and packages have labels, adhesive, or even food residue that must be removed. This non-plastic waste cannot be recycled and can cause the final product to have poor structural integrity .
Step 4: Resizing
Resizing consists of shredding or granulating the plastic waste into small particles. This increases the surface area of the plastic, making it easier to process, reshape, and transport if needed.
Additionally, it gives recycling facilities one last opportunity to remove any non-plastic waste that has made it through the first 3 steps of processing. This is often done with metal detectors or magnets that will help remove any leftover metal in the mixture .
Step 5: Identification and separation of plastics
The identification and separation of plastics is when the now small plastic particles are tested to determine their quality and class.
The first quality tested is density. This is done by floating the particles in a large tank of water. Particles less dense than water will float and more dense particles will sink.
Next their air classification is determined. Air classification is an official term for how thick or thin a particle is. This is done by dropping the particles into a small wind tunnel. The smaller pieces will fly higher up the tunnel and bigger ones will remain lower.
Two other features plastics are commonly tested for are their melting point and color. These are determined by collecting and analyzing samples from each batch of plastic particles [1,2,3].
Step 6: Compounding
The final step in the recycling process is often considered the most exciting because it is when the plastic particles are made into something usable for future production. Compounding is when the small particles are smashed and melted together into plastic pellets. The pellets can then be used in the production of other plastic products .
Throughout this process the plastic may be moved to different plants that specialize in different steps of the process. It can be energy intensive and the better educated we are about the process the more we can reduce the time and energy it requires.