Sofia Martinez
Plastic is a highly versatile material that we use a lot of. It is important to recycle plastic to reduce our need to create new plastic. However, before plastic can be recycled, it must be sorted. Sorting plastic is crucial because it ensures that polymers can be reused and retain their value. Sorting plastic by type can be done at Material Recovery Facilities (MRF) and Plastic Recovery Facilities (PRF). These facilities use sorting equipment such as optical sorters, sink-float separators, and infrared systems to distinguish between different types of plastics. Once sorted, the plastic can be washed, shredded, and melted into new recycled plastic pellets, which are then sold to be used in new products.
| Characteristics | Values |
|---|---|
| Importance of sorting plastic | To recycle plastic, it must be sorted into separate streams to eliminate cross-contamination of polymers that would render a batch unsuitable for reprocessing |
| Sorting plastic into separate streams helps improve sorting output and maximise recycling volumes | |
| Sorting plastic into separate streams helps ensure the quality and reliability of the supply of recycled polymers | |
| Sorting plastic into separate streams helps polymers to be reused and retain their value | |
| Sorting plastic into separate streams helps ensure that all contaminants have been removed | |
| Sorting plastic into separate streams helps ensure that all adhesives, inks, dirt, and other impurities have been removed | |
| Sorting plastic into separate streams helps ensure that metals and any other non-plastic waste have been removed | |
| Sorting plastic into separate streams helps ensure that wood, rubber, foil, and other contaminants have been removed | |
| Sorting plastic into separate streams helps ensure that the final products are of high quality and purity | |
| Sorting plastic into separate streams helps ensure that the plastic is ready for collection and recycling | |
| Sorting plastic into separate streams helps ensure that the plastic is ready for further processing | |
| Sorting plastic into separate streams helps ensure that the plastic is ready for re-use | |
| Sorting plastic into separate streams helps ensure that the plastic is ready to be transformed into new products | |
| Sorting methods | Sorting machines, optical sorting machines, sink-float separators, magnets, washers and water baths/tanks, infrared systems, optical detection systems, manual sort |
| Sorting criteria | Type of plastic, density, colour, size, thickness, food contact |
| Collection | Plastic is deposited by users into a recycling container; local authorities collect plastic for recycling; plastic is collected from homes, businesses, and local recycling centres |
| Sorting facilities | Material Recovery Facilities (MRF), Plastic Recovery Facilities (PRF) |
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What You'll Learn
Different types of plastic require different recycling processes
There are several methods used to separate different types of plastics. One method is a wet process called a sink-float separator, where high-density plastic sinks and low-density plastic floats in a tank of water. Another method involves sorting machines that use infrared, x-ray, or other cutting-edge sensors to recognise a polymer's unique signature and, in some cases, colour. Light plastics like polyethylene (PE) and polypropylene (PP) films are filtered off in an airstream, while heavier and rigid plastics are sorted using near-infrared systems that distinguish between the reflectivity of different polymers. Optical detection systems can also be used to separate colours.
Once the plastics have been sorted, they are washed to remove impurities such as dirt, glue, ink, paper, and grit. This is followed by resizing, where shredders and granulators break down the plastic into smaller particles or flakes. The plastic is then melted and extruded into new recycled plastic pellets, which can be moulded into new products.
The recycling process for different types of plastic varies, and some plastics are easier to recycle than others. For example, plastic bottles are usually made from PET and HDPE, two types of plastic that are easy to recycle. On the other hand, some types of plastic, such as compostable plastics, cannot be recycled in the same way as non-biodegradable plastic and require special handling. Additionally, black plastic, plastic sleeves on PET bottles, and products with multiple layers can complicate the sorting process, leading to valuable materials being discarded.
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Sorting plastic reduces contamination
Plastic is a highly versatile material that is used extensively in our daily lives. Sorting plastic before recycling is crucial to the process, as it reduces contamination and ensures the final recycled product is of high quality and purity.
The sorting process involves separating plastic from other materials and then sorting the different types of plastic. This is done at Material Recovery Facilities (MRF) and Plastic Recovery Facilities (PRF). Sorting is done manually and with the help of advanced technology. Near-infrared systems, for example, distinguish between different polymer types by identifying their individual wavelength signatures. Optical detection systems separate colours, and some facilities use float tanks to separate plastics by density.
Sorting plastic by type is important because it reduces the contamination of polymers, which would otherwise render the batch unsuitable for reprocessing. The more pure the sorted plastic is, the more valuable it is. This means that the polymers can be reused and retain their value. Sorting also helps meet stringent standards, such as separating plastics intended for food contact from the rest.
Additionally, sorting plastic by type makes it easier to shred, melt, and mould the plastic into new products. This is because different types of plastic have different properties, and sorting them ensures that the recycled product is of consistent quality. This also helps reduce the amount of plastic waste that ends up in landfills or is incinerated.
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Sorting plastic increases the value of recycled polymers
Plastic recycling is a multi-step process that involves collecting, sorting, and reprocessing plastic to be used in new products. Sorting plastic is a crucial step in the recycling process as it increases the value of recycled polymers.
The sorting process involves separating plastic from other materials and sorting different types of plastic. This can be done manually or using advanced sorting machines that can identify and separate large amounts of plastic based on their unique signatures. Sorting plastic by type ensures that the recycled polymers are of high purity, which is essential for maintaining their value. Mixed or contaminated polymers can render a batch unsuitable for reprocessing, leading to wastage. Therefore, effective sorting ensures that valuable materials are not thrown away.
The sorted plastic is then transferred to a reprocessor for further processing. The plastic is washed to remove contaminants such as dirt, glue, ink, and other impurities. This washing process helps improve the purity of the polymers, further increasing their value. After washing, the plastic is shredded into flakes or melted down and extruded into new recycled plastic pellets. These pellets are then sold to be used in new products.
The quality and reliability of recycled polymers are crucial factors considered by potential users. By sorting plastic to a high degree of purity, recycling facilities can increase the value of the final product and make it more attractive to buyers. This, in turn, can help promote the use of recycled polymers over virgin plastics, reducing the need to create new plastic.
Overall, sorting plastic plays a vital role in the recycling process by increasing the value of recycled polymers. It ensures that the polymers are free from contamination, maintaining their purity and making them more desirable for reuse in new products.
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Sorting plastic by hand ensures purity
The process of sorting plastic by hand typically involves trained operators overseeing conveyor belts in recycling facilities. Objects whizz by at a rapid pace of around three metres per second, requiring quick and efficient sorting techniques. This manual labour is essential to guarantee the purity of the sorted materials.
One of the critical aspects of sorting plastic by hand is the removal of non-plastic waste. Trained operators are adept at identifying and segregating metal, wood, rubber, foil, and other contaminants from the plastic stream. This meticulous process ensures that only pure plastic continues on to the next stages of recycling.
In addition to removing contaminants, sorting by hand allows for the separation of different types of plastic. This is crucial because most plastics are recycled separately, and mixing different polymers can hinder their reusability. By sorting plastics by hand, operators can distinguish between various polymer types, colours, and densities, ensuring that like plastics are processed together.
Furthermore, hand-sorting allows for the removal of impurities such as adhesives, inks, and labels. This step is essential in achieving the desired purity of the recycled plastic. Once sorted and cleaned, the plastic can be processed into new products, contributing to a more sustainable future.
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Sorting plastic by colour and type
The sorting process typically begins at Material Recovery Facilities (MRFs), which separate plastic from non-plastic items. The plastic is then sent to Plastic Recovery Facilities (PRFs) for further sorting into different types of plastic. This step is crucial, as different types of plastic have distinct melting points and properties, which affect their recyclability. Optical sorting machines, sink-float separators, and magnets are used to separate plastics by thickness, colour, size, and type. For instance, a sink-float separator distinguishes high-density plastic, which sinks, from low-density plastic, which floats.
Colour sorting is another critical aspect of plastic recycling. While it offers more marketing options for plastic containers, it also increases the complexity and cost of recycling. Automated colour sorting machines use visible reflectance spectroscopy and identification algorithms to rapidly identify and sort plastics by colour. This technology has been proven effective in sorting polypropylene (PP) resins, which can be blue, red, green, white, or yellow.
Sorting plastic by type and colour is essential for safety, efficiency, and maintaining the value of recycled materials. It ensures that dangerous chemical reactions are avoided, and the correct types of plastic are used to create new products. Proper sorting also increases the value of recycled plastics, benefiting both recycling companies and consumers.
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Frequently asked questions
Sorting plastic by type is crucial as it ensures that polymers can be reused and retain their value.
Plastic is sorted at Material Recovery Facilities (MRF) and Plastic Recovery Facilities (PRF) using various techniques, including optical sorters, sink-float separators, magnets, and advanced sorting machines that can identify polymers using infrared, x-ray, or other cutting-edge sensors.
After sorting, the plastic is washed to remove contaminants such as dirt, glue, ink, and other impurities. It is then processed into new products through methods such as shredding, melting, and extrusion into pellets or moulding.
