Don't Throw Your Future Away with Plastic Packaging — Recycle It

In a globalizing world, population growth and changing living standards have accelerated production and consumption rates each day. As global production and consumption rates increase, the use of plastics that facilitate our daily lives is also rising. After use, plastics are typically discarded into nature by people, creating environmental problems. Today, most products that are thrown away as waste mean people are disregarding their own futures as well. Consequently, nature becomes polluted, ecosystems suffer damage, and as a result of unconscious behavior, many living creatures lose their right to exist. For this reason, particularly European countries are taking various steps toward banning single-use plastics and bags. Despite such environmentally conscious approaches, it appears impossible for us to give up the comfort that plastics provide to our lives. Instead, environmental problems can be prevented by implementing more environmentally friendly regulations in plastic use and production. As long as people do not give proper value to the environment and plastics, various environmental and economic problems will continue to arise despite all bans. Of the 359 million tons of plastic produced globally, 150-200 million tons are discarded into the environment. This situation stems not from plastic itself but from people's habits after use. In recent years, Turkey has placed emphasis on recycling activities, and source-based separation efforts have been initiated with the Zero Waste project. Source-based separation of plastic increases the recycling rate while reducing recycling costs. In Europe, approximately 60% of produced plastic is used in packaging and consumer products. In Turkey, 37% of products used in the packaging sector consist of plastic packaging. Poly(ethylene terephthalate) (PET), which is used extensively in the packaging sector, is seen to create waste accumulations on a global scale. In Turkey, PET comprised 23% of the total plastic raw material produced in 2019. Commercialized by DuPont in the 1950s, PET is a polymer widely used in many industrial applications such as fibers, foams, and films thanks to its properties including low production cost, high gas barrier properties (against oxygen and carbon dioxide gases), heat resistance, and recyclability. Beginning to be used in bottle production in the 1970s, PET is the most recycled plastic packaging material in Europe. According to the 2018 OECD report, 970,000 tons of PET were recycled in the United States in 2014. [caption id="attachment_131119" align="aligncenter"] Figure 1: a) PET bottle waste discarded into nature b) Source-based separation of PET bottle waste.[/caption] Although bio-based raw materials have been used in PET bottle production recently, recycling is recognized as the most effective method for reducing PET's environmental impacts. PET recycling has become important for minimizing environmental problems and sustainable production. PET bottle recycling efforts initially began in the 1970s with the aim of improving waste management. PET waste is classified as process waste and consumer waste. Process waste is generated from sprues during PET production or as a result of production errors. Consumer waste is considered waste generated by consumers after use. PET waste is recycled through two main methods: chemical and mechanical. [caption id="attachment_131120" align="aligncenter"] Figure 2: Life cycle of a PET bottle.[/caption] PET, generally used in water, beverage, and oil bottles in the packaging sector, is mechanically recycled after its waste is collected from the environment. In 2015 in Japan, 0.51 million tons out of 0.6 million PET waste was mechanically recycled. The mechanical recycling process consists of stages: contaminant removal, shredding, washing, separation by density difference, drying, and melt processing. In the contaminant removal stage, waste PET is separated from other plastic types, metal pieces, and other materials. After this stage, PET waste is classified by color, ground, and cleaned by washing. After the washing stage, drying is applied to PET waste. Dried PET waste can be reprocessed and used particularly in sectors such as packaging, automotive, textiles, and furniture. [caption id="attachment_131121" align="aligncenter"] Figure 3: Mechanically recycled waste PET bottle.[/caption] During reprocessing and "active life," PET is exposed to various factors such as mechanical forces, aging reactions, acids, and laundry detergents, which changes its structural and physical properties. This situation limits the applications of recycled PET. To improve the structural and physical properties of recycled PET, different methods such as vacuum systems, solid-state polymerization (SSP), and chain extension are preferred. Through these methods, recycled PET raw material produced is used in place of virgin PET raw material. Chemical recycling of waste PET is a quite costly method. In this method, depolymerization of waste PET is carried out through chemical reactions such as pyrolysis, alcoholysis, hydrolysis, glycolysis, and methanolysis. As a result of recycling, the obtained chemicals can be used in PET synthesis or in the synthesis of polymers such as alkyd resins, polyurethane, unsaturated polyester resins, and epoxy resins. Through pyrolysis, PET waste is burned for energy recovery. Since burning waste PET harms the environment, this method is not widely preferred. Every recyclable waste product adds value to the economy as it can be used as raw material. It should not be forgotten that PET bottle waste is not garbage but actually a source of raw material. Recycling PET waste enables more efficient use of resources and minimizes the environmental impacts of waste left in nature. Although PET bottle waste is not high in weight, it constitutes a significant proportion in terms of volume. For this reason, source-based separation of PET bottle waste, recycling, and energy use are of great importance. As a result of reducing PET waste left in the environment, less raw material and intermediate products are used in production. Providing PET bottles with a circular life will make a significant contribution to the country's economy in terms of raw material, energy efficiency, and sustainable consumption.

Sources / References

S. Devasahayam, G. B. Raju, C. M. Hussain, Utilization and recycling of end of life plastics for sustainable and clean industrial processes including the iron and steel industry, Materials Science for Energy Technologies 2 (2019) 634–646.

Tournier, V., Topham, C.M., Gilles, A. et al. An engineered PET depolymerase to break down and recycle plastic bottles. Nature 580, 216–219 (2020).

OECD, Improving Markets for Recycled Plastics: Trends, Prospects and Policy Responses, OECD Publishing, Paris, (2018).

Turkey Plastic Sector Monitoring Report, PAGEV, (2019). https://sifiratik.gov.tr/plastik-atik

 

Aysun Ekinci

Prof. Dr. Mustafa Öksüz Yalova Üniversitesi Vocational School Materials and Material Processing Technologies Department

Prof. Dr. Mustafa Öksüz

Yalova Üniversitesi Faculty of Engineering Polymer Materials Engineering Department