Addressing the Plastic Waste Problem with Chemical Upcycling BY ANNA KÖLLN '22 Cover image: A display of plastic bottles. Image Source: Tony Webster, Wikimedia Commons
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The Plastic Waste Problem Since their development for large-scale production around 1950, plastics have become a vital part of daily life and are used in a wide spectrum of applications, including food packaging, healthcare, and construction. Due to the widespread usage of plastics, an estimated 8300 million metric tons (Mt) of virgin plastics have been produced in total as of 2017 (Figure 1). Many plastic products are designed for single use, so a significant proportion enter the waste stream shortly after their consumption, resulting in the generation of a cumulative 6300 Mt of plastic waste (Geyer et al., 2017). A large amount of plastic waste is mismanaged, meaning it is openly incinerated, discarded at a dumpsite, or allowed to enter terrestrial or aquatic ecosystems as pollution (Lau et al., 2020). In 2016, it is estimated that 19-23 Mt of plastic waste entered aquatic ecosystems, a figure that could more than triple by 2030 under business-as-usual scenarios (Borrelle et al., 2020). Because the majority of these plastics are not biodegradable and can be harmful to animals when ingested, their entry
to these aquatic environments causes extreme detriment. In order to tackle this global problem, a multifaceted approach involving both pre- and post-consumption mitigation strategies will be necessary (Lau et al., 2020). Structurally, plastics are polymeric materials made primarily of carbon, with some varieties containing other elements such as oxygen or chlorine (Figure 2). The stability of carbon-carbon bonds makes plastics durable but difficult to break down, rendering them nonbiodegradable. Their repetitive structure also results in thousands of virtually identical chemical bonds in a single macromolecule, making it challenging to differentiate between specific bonds. Mechanical recycling, the conventional method for repurposing plastic waste, involves the subsequent separation, sorting, washing, grinding, and pelletizing of plasticsfor reuse based on their designated recycling code. The thermal and mechanical stressors present during a plastic’s lifetime and throughout the mechanical recycling process causes the polymers to undergo DARTMOUTH UNDERGRADUATE JOURNAL OF SCIENCE
