Alexei Volkov
Plastic is one of the most popular and useful materials of modern times, with 300 million tonnes produced each year. However, the plastic industry depends on non-renewable resources and creates a massive waste management issue. While many people are already recycling plastic, the actual recycling of plastic makes up a very small share of the global waste market. The process of recycling plastic involves several steps: collection, sorting, and reprocessing. Plastic is collected from homes, businesses, and schools, then sent to Material Recovery Facilities (MRFs) or Plastic Recovery Facilities (PRFs) to be sorted by type. After sorting, the plastic is washed, shredded, and sorted further before being melted and formed into pellets, which are sold to producers of recycled plastic products. These pellets are then moulded into new products.
| Characteristics | Values |
|---|---|
| Plastic waste types | Consumer waste, industrial scrap |
| Plastic waste composition | Polyolefins make up nearly 50% of all plastic waste, more than 90% of waste is made of thermosoftening polymers |
| Plastic waste sources | Homes, businesses, schools, local recycling centres |
| Plastic waste collection | Directly by local authorities or using a waste management contractor |
| Plastic sorting | Manual, optical, AI, machine learning |
| Plastic cleaning | Quick rinsing, extensive washing |
| Plastic processing | Shredding, grinding, melting, extrusion |
| Plastic recycling rates | 9% of 9.2 billion tonnes of plastic waste produced since the 1950s was recycled as of 2019 |
| Plastic recycling challenges | Complexity of recycling different types of plastics, inefficient systems, plastic contamination |
| Plastic recycling solutions | Biodegradable plastics, compostable plastics, reusable systems, non-plastic alternatives |
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What You'll Learn
Sorting plastic from other materials
The first technique is manual picking, which involves sorting by hand. Large items, non-recyclables, and obvious contaminants are removed and sent for further processing or disposal. After non-recyclables have been removed, the waste is fed into trommels. Trommels are cylindrical drums with holes that allow finer materials to fall through. Optical sorting is another popular method, where recyclable material is spread out on a conveyor belt and passed under a bright light. Sensory measurements determine which part of the spectrum the material absorbs and reflects. A spectrometer identifies each material based on this signature, and compressed air is used to transfer each item into an appropriate receptacle for additional inspection.
Robots are also used in the sorting process, with AI able to recognise an increasing number of diverse recyclable materials. These robots can pick, separate, and sort recyclable plastics from other materials. They are particularly useful for dealing with construction and demolition waste, extracting recyclable content from other debris. Symbols on plastic packaging can help explain which type of plastic they are made of and how to recycle them. However, these can often be confusing, and it is important to know what they mean to recycle effectively.
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Washing and shredding plastic
Plastic shredders are an essential tool for sustainable plastic recycling. They reduce the size of plastic waste, preparing it for further recycling processes. These machines can handle various plastic materials, including rigid items like bottles and containers, as well as flexible plastics like films and bags. The shredding process transforms bulky plastic items into smaller granules or flakes, making them easier to handle, transport, and process in downstream recycling steps.
Washing plastic is an important step in the recycling process. It helps to remove contaminants and ensure that the plastic is clean before it is processed further. Rinsing plastic waste or recyclable materials before disposal is beneficial, as it can prevent the loss of material that could have been recycled. While quick rinsing is generally preferred to save water, the washing process typically involves sending the shredded plastic through a rotating, heated wash and rinse process. Vent hoods are used to extract excess moisture from the plastic.
Shredded plastic is then dried using a drum dryer with a high-volume hot air blower. The hot air is recirculated to ensure an optimal operating temperature is achieved in a short time. This step is crucial in removing any remaining moisture from the plastic before it undergoes further processing. The dried plastic is then ready for the next stage of the recycling process.
After shredding and washing, the plastic undergoes further sorting and processing. This may include separating different types of plastics or removing contaminants. Techniques such as manual picking, float sink tanks, and optical sorters are used to separate and sort the plastic further. Once the plastic is clean and sorted, it can be shredded into flakes or melt-processed to form pellets or granules. These pellets are then sold to manufacturers to be moulded into new products.
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Melting and reforming plastic
The first step in recycling plastic is to collect the plastic waste. This is done by local authorities or waste management contractors, who pick up plastic waste from homes, businesses, and schools. The plastic waste is then taken to a Material Recovery Facility (MRF) or a Plastic Recovery Facility (PRF). These facilities sort plastic from other materials and separate different types of plastic. This can be done manually or through more sophisticated methods such as optical sorting, where recyclable material is spread out on a conveyor belt and identified by sensors.
Once the plastic has been sorted, it is washed and shredded into flakes or ground into pellets. These pellets are then melted and reformed into new products. This process is called mechanical recycling and is the most common form of recycling plastic. It is a simple and economical technique that has a lower carbon footprint than other processes. However, it can be time-intensive and expensive to properly sort and clean the plastic, and some types of plastic may only be recycled once without acquiring defects and contaminants.
The melted plastic is then extruded into new recycled plastic pellets, which are sold to be used in new products. These pellets can be moulded into various shapes and used to create a wide range of products, from park benches and decking to new plastic bags and packaging.
It is important to note that not all plastic is recyclable, and some types of plastic may require complicated and expensive processes to recycle. Additionally, some plastic may be deemed unrecyclable by certain facilities due to the cost or complexity of the process.
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The future of plastic recycling
Plastic recycling is an essential part of creating a circular economy and reducing our environmental impact. The future of plastic recycling holds many promising advancements and trends that will shape the way we manage and recycle plastic waste.
One significant trend is the increasing capacity and commitment of the recycling industry. Organizations like the Association of Plastic Recyclers (APR) have played a pivotal role in advocating for sustainable practices and influencing policies. APR members have the capability to significantly increase their recycling rates for materials like PET, HDPE, and PP if they can secure more supply. This highlights the importance of strengthening collection programs and ensuring a steady stream of plastic waste for recycling.
Another key aspect of the future of plastic recycling is the development of innovative materials and technologies. The invention of poly(diketoenamine), or PDK, a type of plastic that can be recycled indefinitely without any loss in quality, offers a promising solution to the waste crisis. PDKs are expected to become commercially competitive with conventional plastics, driving down costs and promoting sustainability. Additionally, the replacement of PVC with substances like PHA (polyhydroxyalkanoate), a biodegradable bio-polyester, can help address the issue of toxic components in conventional plastics.
To further enhance the effectiveness of plastic recycling, policymakers and industry leaders are emphasizing the importance of proper sorting and cleaning of plastic waste. This mechanical recycling process can be time-intensive and expensive, but it ensures that recycled materials are free from defects and contaminants. Local policies and initiatives, such as those implemented in Maine and Oregon, have proven successful in increasing recycling rates and reducing plastic waste.
Public awareness and demand for sustainable alternatives have also played a crucial role in shaping the future of plastic recycling. Viral moments, such as the widely circulated video of a turtle with a straw stuck in its nose, have sparked conversations about plastic straw bans or alternatives. This has prompted manufacturers to reconsider their use of plastic and explore reusable packaging, refillable bottles, and take-back services.
In conclusion, the future of plastic recycling holds great potential. With advancements in technology, increased industry commitment, and supportive policies, we can significantly reduce plastic waste and create a more sustainable planet. The actions taken today will shape the environmental legacy we leave for tomorrow.
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Plastic recycling symbols
- PETE/PETG or just PET: This symbol, often found on soft drink bottles, mineral water containers, fruit juice containers, and cooking oil containers, stands for polyethylene terephthalate. It is easily recyclable and can be reused to make new containers, carpets, and furniture.
- HDPE: This symbol represents high-density polyethylene, one of the most commonly used plastics in the United States. It is widely recycled and used for containers like milk cartons, detergent bottles, and cleaning agents.
- PVC: This symbol stands for polyvinyl chloride. PVC is used in bubble foils, trays for sweets and fruit, and expanded PVC foam boards for commercial applications. It is rarely recycled and usually burned.
- LDPE: This symbol indicates low-density polyethylene, a flexible plastic used for shopping bags, carry bags, and plastic wraps. LDPE is not commonly recycled through curbside programs, but some communities are starting to accept it.
- PP: This symbol stands for polypropylene, a durable and lightweight plastic. It is used for ketchup bottles, medicine bottles, car parts, and furniture. PP is increasingly accepted in recycling programs.
- PS: This symbol represents polystyrene, a plastic commonly used in toys, cosmetic bags, refrigerator trays, and vending cups. It is not widely accepted in recycling programs but can be recycled into egg cartons and takeout containers.
- OTHER: This category includes various plastics such as acrylic, polycarbonate, nylon, and fiberglass. It is a residual category, and plastics labelled with this symbol are typically burned rather than recycled.
It is important to note that understanding these symbols is crucial for effective recycling. Placing the wrong items in a recycling bin can contaminate recyclable materials and negatively affect the recycling process. Additionally, some plastics are more difficult to recycle than others, and their potential toxicity should be considered.
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Frequently asked questions
Plastic recycling is the process of turning plastic waste into other products.
Plastic recycling involves six steps: collection, sorting, shredding, melting, extrusion, and moulding.
Six types of commodity polymers account for about 75% of plastic waste, with the rest made up of other polymers such as polyurethanes and synthetic fibres. The most common types of plastic are PET, HDPE, and PP.
Check your local recycling guidelines. Rinse your plastic waste and separate it according to the type of polymer. You can then either put it in your household recycling bin or take it to a recycling centre.
Plastic recycling can reduce dependence on landfills, conserve resources, and protect the environment from plastic pollution and greenhouse gas emissions.
