The Plastic Recycling Dilemma: Is it Truly the Ultimate Answer?
Plastic pollution has emerged as an imminent environmental concern, with nations around the world grappling with the fast build-up of plastic waste. The slow breakdown rate of plastic products, as well as social stagnation, all add to the weight of plastic waste (Miao et al., 2021). Plastic manufacturing and waste have increased dramatically over the years, reaching 359 million metric tons (MT) in 2018. As of 2018, humanity has produced a total of 8.3 billion MT of plastics (Geyer et al., 2017). Primary plastic production is expected to reach a startling 1,100 million metric tons by 2050 if present trends continue (United Nations Environment Programme, 2017). However, fewer than 10% of the world’s 8 billion tonnes of plastic garbage is recycled, resulting in enormous environmental and economic losses.
Furthermore, insufficient plastic waste management has resulted in millions of tonnes of plastic being lost to the environment or burnt and dumped in remote regions. The financial impact is significant, with an estimated yearly loss of value ranging from US$80–120 billion owing to the sorting and processing of plastic packaging waste alone (United Nations Environment Programme, 2017). Furthermore, the seas suffer a considerable load, with an estimated 75 to 199 million metric tonnes of plastic already present. Without radical changes in plastic manufacturing, use, and disposal, the annual influx of plastic trash into aquatic environments is expected to nearly treble, reaching 23–37 million metric tonnes per year by 2040.
In light of regulatory demands, rising prices, and the low biodegradability of frequently used polymers, traditional ways of dealing with plastic trash, such as incineration with energy recovery or landfill disposal, are facing shortcomings (Achilias et al., 2009). Recycling has so emerged as the favored method. These alarming patterns present a bleak picture of the plastic pollution catastrophe, emphasizing the critical need for effective solutions. As a result, innovative plastic depolymerization technologies have emerged as a potential strategy to reducing plastic pollution and ensuring a sustainable future.
The Basics of Plastic Recycling
Plastics come in a variety of forms, and their differences allow for optimum material selection for a given application (García, 2016). According to the Society of the Plastics Industry (SPI), the most extensively used plastics materials are polypropylene (PP), polyethylene (HDPE and LDPE), polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET).
Although not all plastics can be recycled, it is still conceivable. The recycling of waste polymers can be accomplished in four ways (Achilias et al., 2012):
- Primary recycling entails the recycling of clean and uncontaminated single-type waste in-plant. Because of its simplicity and low cost, it is a popular strategy, although it is restricted to recycling regulated scrap materials with a known history.
- Mechanical recycling (secondary recycling) separates the polymer from impurities and allows it to be recycled into granules using standard melt extrusion. However, the recycled product’s characteristics decline with each cycle due to a decrease in polymer molecular weight induced by water and acidic contaminants. During reprocessing, strategies such as extensive drying, degassing vacuum, and the use of chain extender chemicals can assist preserve the average molecular weight.
- Chemical recycling (tertiary recycling) encompasses complete depolymerization of polymers such as PET into monomers or partial depolymerization into oligomers along with additional chemical compounds. After that, the monomers can be repolymerized to recreate the original polymer.
- Energy recovery (quaternary recycling) is a method of recovering the energy component in polymers. Incineration is a typical method for reducing the volume of organic materials while recovering energy. It has, however, been criticized because to worries about the production of air contaminants such as dioxins, especially when chlorine-containing polymers are burnt.
Apart from the previously mentioned methods, direct reuse of plastic materials, particularly PET, is considered a “zero order” recycling approach (Achilias et al., 2012). While many countries practice the refilling and reuse of PET bottles, caution is necessary due to plastic’s higher tendency to absorb contaminants compared to glass. These absorbed contaminants may be released back into food or beverages during refilling. Additionally, refilling PET bottles with high-alcohol drinks can cause the macromolecular chains to degrade, leading to unforeseen consequences.
Rethinking the Limits of Recycling
Despite mounting environmental concerns, plastics continue to play an important part in our everyday lives, with no immediate worldwide alternatives. A critical issue, however, arises: can recycling alone successfully address the plastic pollution crisis? The Society of the Plastics Industry (SPI) categorizes plastics into seven types, of which only two, PET and HDPE, are absolutely recyclable (Miao et al., 2021). While significant attempts are being undertaken to recycle some plastics, such as PP and PS, others, such as PVC, LDPE, and PMMA and PC, presently lack feasible recycling possibilities.
Effective plastic waste management policies should focus not solely on material reuse but also on the production of raw materials (monomers) for the reproduction of plastics or the creation of secondary valuable products for industrial processes and transportation fuel, in accordance with the principles of sustainable development. As a consequence, the EU Action Plan, the Global Plastic Action Partnership, and the Ellen MacArthur Foundation (2018) have collectively recommended a path for the plastic sector’s growth: elimination, innovation, and circularity.
1. Elimination
The first priority in the plastic industry’s development plan is the removal of harmful and superfluous plastic objects. This includes minimizing the number of plastic formulations and additives, as well as detecting and disposing of additives effectively to improve recycling operations.
2. Innovation
The second objective focuses on innovation to make plastics more useful, recyclable, or compostable. Chemical recycling research, such as supercritical water depolymerization and hydrothermal catalytic depolymerization, shows promise for more effective recycling of various polymers.
3. Circularity
The ultimate objective is to achieve circularity by inventing plastic items that are reusable, recyclable, and remanufacturable. This change toward circular design principles will aid in keeping plastic objects in the economy and out of the environment, therefore fostering sustainable behaviors.
These three points — elimination, innovation, and circularity — form a roadmap for the plastic industry’s future, with the goal of addressing the difficulties of plastic waste and driving positive change in the manufacture and usage of plastics.
In a Nutshell…
Plastic pollution is a huge environmental concern that requires a multifaceted strategy. While recycling is important, it is insufficient to solve the enormity of the problem. A plan for the future of the plastic industry highlights three critical pillars to effectively tackle plastic pollution: elimination, innovation, and circularity. This includes reducing the use of unneeded plastics, supporting creative and sustainable alternatives, and designing goods with reuse and recycling in mind. To achieve these objectives, worldwide collaboration is required, as well as legislation reforms, technical breakthroughs, and enhanced consumer awareness. We can strive towards a more sustainable and plastic-free future by taking a comprehensive approach, protecting our ecosystem for future generations.
References
Achilias, D. S., Andriotis, L., Koutsidis, I. A., Louka, D. A., Nianias, N. P., Siafaka, P., Tsagkalias, I., & Tsintzou, G. (2012). Advances in the Chemical Recycling of Polymers (PP, PS, LDPE, HDPE, PVC, PC, Nylon, PMMA). In D. S. Achilias (Ed.), Material Recycling — Trends and Perspectives (1st ed.). www.intechopen.com
Achilias, D. S., Antonakou, E. V., Koutsokosta, E., & Lappas, A. A. (2009). Chemical recycling of polymers from waste electric and electronic equipment. Journal of Applied Polymer Science, 114(1), 212–221. https://doi.org/10.1002/app.30533
Ellen MacArthur Foundation. (2018). Plastics and the circular economy. https://ellenmacarthurfoundation.org/plastics-and-the-circular-economy-deep-dive
García, J. M. (2016). Catalyst: Design Challenges for the Future of Plastics Recycling. Chem 1, 813–819. https://doi.org/10.1126/science.aad1694
Geyer, R., Jambeck, J. R., & Law, K. L. (2017). Production, use, and fate of all plastics ever made. ScienceAdvances. http://advances.sciencemag.org/
Miao, Y., von Jouanne, A., & Yokochi, A. (2021). Current technologies in depolymerization process and the road ahead. In Polymers (Vol. 13, Issue 3, pp. 1–17). MDPI AG. https://doi.org/10.3390/polym13030449
United Nations Environment Programme. (2017). Visual Feature | Beat Plastic Pollution. United Nations Environment Programme. https://www.unep.org/interactives/beat-plastic-pollution/?lang=EN
