Plastic recycling is immensely important. Plastic products have extremely long lives – taking hundreds of years to biodegrade if allowed to pollute our environment. It is vitally important that plastic is not seen as a single-use material. Plastic is a synthetic material made using fossil fuels, so it damages the environment in more ways than just by lying around. Plastic recycling plants are part of the solution. Here are the stages that plastic goes through in a plant when it is recycled.
Plastic entering a recycling plant needs to be correctly sorted. Plastic is usually sorted according to its resin content. In order to be effectively made into recycled products, a uniform resin content needs to be present in all of the constituent plastic. The technology used to sort plastics by resin content is changing. AI is being developed that can automatically sort plastic at recycling plants instead of manual pickers being used.
Once the plastic has been sorted, it usually gets compacted into bales. These are made by powerful recycling balers, which use hydraulic rams to force plastics into cubes. Bales are far more efficient and safe to store and transport than loose materials. The fact that bales are made to a standard size means that all other machines in a recycling plant can be made to accommodate them.
The plastic is then washed to remove any non-plastic waste such as labels or food. Any non-plastic waste that is accidentally left behind after this stage can worsen the structural integrity of recycled products.
The plastic is separated from the bale used to transport or store it and shredded into fine particles. Shredding increases the total surface area of the plastic, which makes it much easier to process.
The shredded plastic is then carefully tested for its density. This helps workers determine what the materials can be recycled into. Certain products need high-density plastic source material. The initial sorting process should have been sufficient for grouping plastics by density, but a final classification check before melting is definitely needed.
The plastic – now finely shredded, cleaned, and classified – is melted down in a furnace that then deposits liquid plastic into a hopper or container. This melted plastic can either be made into new products on-site or processed into granular pellets that can be sold to manufacturing companies.
If the plastic is destined for manufacturing off-site, it needs to be made into pellets – which are the standard medium in which plastic is bought by manufacturers. The tiny pellets – adorably known as nurdles officially – are made by smashing together tiny particles. Nurdles are extremely efficient because they can be melted down by manufacturers very easily and tested without too much destructive sampling. Nurdles need to be carefully contained. If they are allowed to enter the environment, they can last for many years and become almost impossible to collect and remove from fragile ecosystems. Charities like The Great Nurdle Hunt in the United Kingdom have been highlighting this issue for years.