A bit of background
PET or polyethene terephthalate is highly recyclable and used in the manufacture of new bottles and containers, strapping, and thermoform packaging. PET is essentially polyester and is also used in fibre applications like apparel and carpet. PET is created by combining two monomers, modified ethylene glycol and purified terephthalic acid and was first synthesized during the 1940s in North America by Dupont.
PET plastics in many countries are labelled with the resin identification code number ‘1’, inside the universal recycling symbol, near or on the bottom of the containers and bottles. It is used for packaging a variety of products like peanut butter, beverages, frozen goods, cosmetics, produce, bakery goods and household cleaners. As PET is known for its strength, transparency, light-weight, shatter-resistant, inexpensive, recyclable and thermos-stability, it is a popular choice for packaging.
What is PET Recycling?
RPET also is known as recycled polyethene terephthalate is the widely recycled plastic around the globe. According to the PET Resin Association or PETRA, the recycling rate in the US was 31 per cent in 2012 while it was 52 per cent in the European Union. The US Environmental Protection Agency or EPA had estimated that around one per cent of municipal solid waste in the US is attributed to PET containers.
In India, PET bottles even after their use, carry a lot of value, and the RPET is used in a variety of applications. Waste traders bring the waste PET bottles, and employ people for segregating, sorting and selling them to larger vendors or recycling stations.
RPET serves as raw materials for a variety of products such as:
- Fibre for polyester carpet
- Long underwear
- T-shirts for fabric
- Athletic shoes
- Upholstery and luggage
- Fiberfill for sleeping bags, winter coats and sweaters
- Industrial strapping
- Film and sheet
- Parts for automotive
- New PET containers
After replacing PET in place of virgin resin resulted in reduced energy consumption, less cost decreased impact on the environment and carbon dioxide emissions in the atmosphere.
Collecting and Sorting of PET
PET packaging that is empty and discarded by the consumer after use becomes PET waste and in terms of the recycling industry is referred to as ‘post-consumer PET”. By involving both single and dual-stream approach, post-consumer PET materials are collected through curbside recycling programs. Other PET recycling arrangements are devised to divert empty PET bottles of high accumulation locations like large events. PET materials that are recyclable are sorted from other recyclables at material recovery centres and baled for shipment to a recycling PET facility. For minimizing product contamination with other scrap material, the focus should be on proper bale handling and storage practices.
After arriving the recycling facility, the packages are then staged before they are located on the conveyor belt and served to the bale breaker. After that, bales are split open, and the bottles are singulated. The materials are then washed away, and labels are removed via steam and chemicals. Before the washing stage, any PVC or polyvinyl chloride bottles sent through hot water or hot air trammel turns slightly brown and provides easy identification and removal during the manual sorting stage.
For easy identification of material using near-infrared (NIR) sorting equipment to remove other materials, the pre-wash and label removal process is conducted. Other technologies like manual sorting belts and metal detectors are implemented. Manual sorting techniques include sorting results like removing the PET from the material flow or negative consequences like removing the non-PET materials from the material flow.
Recycling Process of PET
After sorting the PET waste, the materials are grounded into flakes particles. The purity of flake is central to preserving the value of the reclaimed plastic. Further separation techniques include washing and air classification along with water baths, where material may sink or float, and this helps to separate the residual foreign materials. At a standard or elevated heat levels, washing is undertaken, and for achieving a complete cleaning, disinfectants and detergents are used.
After grinding, washing and separation are completed, the materials are rinsed for eliminating any remaining contaminants or agents of cleaning. The RPET then is dried before reintroduction as a manufacturing material or before further processing. For further purifying, melt filtering is carried out by removing any non-melting contaminants that might have survived in any of the previous steps. For forming pellets, extruded material passes through a series of screens, and the non-melted particles are blocked. The pelletized plastic serves a uniformly sized material for the reintroduction into the manufacturing process.
PET bottles and containers are repurposed for a wide variety of users such as in school projects and for the use in solar water disinfection in developing countries. The empty PET bottles are filled with water and left under the sun to allow disinfectant by the sun’s ultraviolet radiation. Many other materials like window glass that are transparent to visible light, PET is useful for this purpose as they are opaque to ultraviolet radiation of the sun.
Another use of PET bottles is as building materials in third-world nations. The bottles are filled with sand by intensive labour process and stacked and then are either mudded or cemented together for building a wall. Some of the bottles are filled with water or air to allow light into the structure.
Conclusion- The Outlook of PET Recycling
Industries are recognizing the increasing urgency to recycle PET into food-grade products like new beverage containers. Food-grade processing has been established, and efforts are being made to improve the efficiency of processing technologies by different companies.
Because the availability of post-consumer PET material is a challenge, one way for improving it would be through the use of vessel deposit methods. More on it will come, but that isn’t a discussion for today!
Also, while we appreciate all the efforts that are being put in PET recycling, one thing that we can do with immediate effect is- avoid using plastics! The circular economy will take some time to come into existence fully!
Till that time, we can push the jute, hemp, bamboo, cotton and even coffee industries. How so, again, that thing is for another time!
So, stay tuned