Over the last decade, the trend for sustainability has led to a considerable increase in the consumption of paper-based alternatives such as paper cups, straws, milk cartons and other packaging materials (Foteinis, 2020). Despite the conventional wisdom that these products are recyclable, as they contain lamination of additional materials, such as polyethylene (PE), per- and polyfluoroalkyl substances (PFAs) and aluminum (refer to Table 1), they are in fact not recyclable. These additional layers are source of microplastic that affect the efficiency and the machinery of traditional paper mills and the value of the paper pulp (Yuhui, 2018). Hence, they are typically disposed of into the landfill or incinerated, which are non-sustainable.

In the landfill, estimates have shown that paper cups take 20 years to decompose, with the possibility of microplastics in the leachate (Triantafillopoulos & Koukoulas, 2020). Additionally, considering paper cups alone, Yuhui (2018) has estimated Mainland China distributes 10 billion cups annually. Australia, UK, and Taiwan, respectively, consume 2.5 billion, 2.52 billion, and 1.5 billion cups per year (Foteinis, 2020; Yuhui, 2018). Moreover, there are 400 million plastic and paper cups being consumed every year in Hong Kong (SCMP, 2022). With this amount of waste generated and lack of specialized waste processing facilities, using these products, thus, doesn’t alleviate the burden of landfills.

In the above table, it is observed that the typical coatings are PE and PFAs. Both are known for their resistance to degradation due to the chemical stability (Emblem, 2012; Krafft & Riess, 2015). Apart from chemical stability, PE is also known for its low cost, durability, chemical inertness, and flexibility, which makes them highly suitable and a popular choice for packaging materials (Emblem, 2012). In 2019, PE had a demand of 100 million metric tons, which accounts 63% of the “global plastic resins demand”(Chitalia, 2020).

PE can be either mechanically or chemically recycled. Mechanical recycling involves remolding of old PE products to form new products or pellets (Schyns & Shaver, 2020). The obvious disadvantage to this method is that it isn’t sustainable. The properties of continuously recycled PE will be degraded over time until it must be completely disposed of (Schyns & Shaver, 2020). It also can’t handle mixed and contaminated plastic waste streams (Vollmer et al., 2020). In contrast, chemical recycling can upcycle diverse plastic waste into various fuels, monomers/oligomers (ready to be polymerized again) through pyrolysis, solvolysis, dissolution, etc. (Vollmer et al., 2020). However, their recycling rates of these technologies must still be improved (Vollmer et al., 2020).

On the other hand, PFAs are common in food packaging due to their heat resistance and water-oil repellency properties (Krafft & Riess, 2015). Hence, due to its usage, it is estimated that in the last six decades, more than 47, 000 tons were released from consumer products into the environment (‘About PFAs,’ n.d.). This is concerning as PFAs can bioaccumulate in the food chain, consequently affecting human health, particularly on development and reproduction(George et al., 2023). Apart from bioaccumulation, PFAs residues can directly migrate on food and drinks (Carnero et al., 2021). In America alone, Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey (NHANES) found PFAs in the blood of 97% of Americans, resulting in reduced blood levels of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) (U.S. Department of Health and Human Services, n.d.). Despite these risks, the current proposed disposal is through chemical breakdown in high temperature or incineration, which is not sustainable as it can release some of the compounds through the vapor (Verma et al., 2023).