Polymers are widely used for manufacturing plastic goods in a range of industries — most notably the packaging sector, which accounts for more than 35% (or about 125 million tonnes) of all plastic product applications. Owing to low cost, light weight, and excellent properties (e.g., mechanical strength, gas/aroma barrier properties), polymers such as polyethylene, polypropylene, and polystyrene are found in many single-use packaging products, including films, bags, cups, and containers (see Table 1).
The demand for plastic packaging continues to grow, according to some estimates by nearly 3.5% per year. And since only about 14% of plastic packaging waste is collected for recycling (most is landfilled, dumped illegally, and, to a lesser extent, used for energy recovery), plastic waste management has become a salient issue. In this article, we offer an overview of the strategies and solutions for addressing plastic packaging pollution.
Problem — Extensive plastic pollution:
Plastic pollution affects the environment in three major ways:
- Degrades natural ecosystems
- Contributes to greenhouse gas (GHG) emissions
- Leads to the formation of particulates that are able to enter living systems
The gathered data show that in the last 70 years nearly 5 billion tonnes of plastic waste has accumulated in the natural environment (not only packaging) — the amount equivalent to the weight of 830 million adult elephants! Furthermore, about 8 million tons of plastic refuse end up in the world’s oceans every year, causing serious damage to aquatic and avian fauna (e.g., entanglement in plastic debris, ingestion of plastic particles).
In addition, polymer resin production, its conversion to plastic products, and end-of-life processes such as incineration account for about 5% of the annual global GHG emissions. These findings suggest that the plastic-originated GHG emissions can be reduced only through the combination of decarbonized energy infrastructure, improved recycling processes, the use of bio-based plastics, and demand management.
Also, since the decomposition rates of conventional plastics are in the hundreds and thousands of years, they do not disintegrate into molecular fragments but rather are broken into small pieces by the elements, and thus can easily enter living organisms. In fact, pieces of microplastic have been found not only in a number of marine animals and birds, but also in table salt, sugar, honey, and beverages. And another problem is that most plastics contain harmful chemical additives, with some plastic debris being inhabited by pathogenic bacteria. Consequently, this raises multiple questions about the long-term health effects of plastic micropieces to living things.
In summary, the extensive use of plastics has led to severe environmental pollution that poses tangible risks to the whole ecosystem.
Solutions — The 5 Rs:
In an attempt to curb plastic pollution, a number of consumer goods companies, including Unilever and Reckitt Benckiser, have adopted various solutions to improve plastic management. Typically, these approaches aim to reduce the amount of packaging material, replace it with a more acceptable alternative, reuse or recycle it, and make packaging recyclable so that it is environmentally friendly. As the former two are straightforward, in this section we briefly discuss the latter three strategies.
Among the various circular economy strategies, reusable packaging is considered the most attractive approach. It focuses on extending the use of packaging solutions and is suited to both business-to-business (B2B) and business-to-consumer (B2C) applications. Specifically, embracing reusable packaging in the B2B setting presents the opportunity to achieve considerable material savings, reduce the company’s carbon footprint, and improve inventory management, and it may even spur the development of the logistics industry founded upon standardized and shared containers.
As for the B2C setting, reusable packaging offers an enhanced customer experience through individualization, improved functionality, and the opportunity to attract and retain customers, particularly the ones concerned about sustainability (see Figure 1). A report compiled by the Ellen MacArthur Foundation, a charity promoting the circular economy, gives 69 examples of B2C reusable packaging solutions implemented by businesses across the beverage, shopping, home and personal care, transportation, and ready meals sectors.
Although promising, reusable packaging poses serious challenges, such as how to deal with currently non-recyclable laminated plastic materials, how to organize the supply chain, and dirty or contaminated packaging.
Recycling, as shown in Figure 2, focuses on reworking end-of-life plastic packaging to either yield the feedstock for new plastic products or give off energy through the incineration of plastic waste.
Ideally, plastic packaging waste ought to be used to yield raw materials for the production of high- or similar-quality products (e.g., polyethylene terephthalate bottles to bottles) or high-quality raw materials for the production of polymers for the same as well as different applications (e.g., polyamide 6, widely used in the automotive, electrical, and textile industries, is a notable example of commercially viable, infinite-loop recycling that yields high-quality raw material for the production of the same polyamide 6).
In reality, as a result of inadequate sorting, only a small fraction of the collected plastic packaging waste is recycled, and the majority of it is reworked to lower-value products (e.g., bag liners) that are not recycled after their use, thus closing the recycling loop after the single cycle.
Despite the inadequacies, some geographical areas have implemented serious measures towards better plastic packaging waste management. For instance, the plastic packaging waste recycling and energy recovery rates in the EU countries (plus Norway and Switzerland) have increased by 92% and 84% respectively since 2006. In 2018, out of the collected 17.8 million tonnes of packaging waste in this region, 42% were recycled, 39.5 % were used for energy recovery, and 18.5% were landfilled, and some of the countries managed to achieve either 0% (e.g., Austria, Netherlands) or minimal (e.g., Germany, Finland) landfill rates.
Though encouraging, the global average recycling rate of plastic packaging remains low due to inadequate regulations regarding plastic waste management in other geographical segments.
Make it recyclable:
Finally, replacing conventional packaging materials with bio-based polymers, such as the ones shown in Figure 3, can mitigate harmful environmental effects discussed earlier.
To avoid confusion over the terms, a distinction must be made between bio-based and durable (e.g., bio-polyethylene) versus bio-based and biodegradable (e.g., starch) polymers: Whereas the former, produced from biosources such as sugarcane, do not harmlessly disintegrate and thus have to be treated like conventional counterparts at the end of life, the latter are completely broken down into carbon dioxide and water by microorganisms. The third class of polymers, fossil-based and biodegradable (e.g., polycaprolactone), can be degraded by bacteria too; however, fossil fuel–derived compounds are used for making them.
At present, the annual production capacity of bio-based and biodegradable polymers is about 2.1 million tonnes, less than 1% of the conventional plastic output, with biodegradable polymers accounting for a little over half the annual capacity. Among the different types, biobased polyethylene and polyamide are ranked highest in the bio-based segment, while starch blends and polylactic acid are the leaders in the biodegradable segment.
Currently, biobased polymers are primarily used in packaging, wherein biobased polyethylene terephthalate and biodegradable polylactic acid constitute the biggest share in rigid packaging, and biobased polyethylene and others are used in flexible packaging. More detailed information about the properties of biodegradable polymers for packaging applications is given in Table 2.
Although biobased plastics are a highly desirable alternative, their higher production cost compared to conventional plastics, the need for separation from non-biodegradable counterparts before disposal, and specific treatment to ensure full decomposition/recycling, as well as inadequate key properties (e.g., mechanical) of biodegradable plastics remain areas for improvement.
Summary and outlook
Owing to its excellent properties, fossil-derived polymers are widely used for the manufacture of many products, especially packaging solutions. Since conventional plastic products decay at a slow rate, this has led to serious environmental pollution that poses great risk to living organisms and ecosystems. To mitigate these harmful effects, plastic packaging developers and producers have implemented a number of strategies, such as reuse, recycling, and switching to bio-based materials. As the drive toward the circular economy intensifies, it is expected that these and similar approaches will become prevalent, thus reducing environmental concerns.
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