Understanding Plastics Recycling

"For the last 150 years, plastic materials have been key enablers for innovation and have contributed to the development and progress of society." [1]. This quote from PlasticsEurope portrays the importance of plastics in today's industrialized society. Imagining today's world without plastics is virtually impossible. Compared to every other engineered material in the world, plastics have the highest growth rate, which is related to their unique properties. Plastics have become the most important raw material for a variety of products and applications. This includes healthcare (medical devices, PPE), packaging (food preservation), construction, electronics, and transportation. Their versatility, durability, high strength-to-weight ratio, and cost-efficient manufacturing methods result in many benefits [2, 3]. For example, plastics are critical in reducing food waste, with plastic packaging extending shelf life by 2-3 times [4, 5]. Furthermore, plastic-based components have reduced the weight of modern vehicles, improving fuel efficiency by 25-30% [6].

These benefits led to a twentyfold exponential growth in their production in the past half-century. Between 2010 and 2023, worldwide plastics production increased by over 50% from 270 Mt to 414 Mt [7]. By 2030 their production is expected to increase to 600 Mt [8].

Increasing production consequently results in higher amounts of plastic waste. In 2024, 360 Mt of plastic waste were generated worldwide, with packaging waste accounting for the highest amount (156 Mt) [9, 10]. Figure 1.1 shows the plastic waste distribution of the different geographic regions.

The growing volume of plastic waste, combined with increasing environmental awareness, highlights the urgency of addressing plastic pollution: Every minute, the equivalent of a garbage truck's worth of plastic enters our oceans; an estimated 8-12 million tons of plastic enter the oceans annually [13]. Furthermore, carbon emissions from plastic production are projected to contribute to 19% of global carbon budget by 2040 [14]. Plastic waste generation is projected to triple by 2060 if current trends continue, which increases the described environmental problems [15].

Figure 1.1 Postconsumer plastic waste worldwide in 2024 (Remark: Europe covers both EU and non-EU countries) [10, 11, 12]

However, despite the growing amount of plastic waste, the share of recycled plastics does not significantly increase. In 2022, only 9% of plastic waste was recycled globally. The remaining waste was predominantly sent to landfills (49%), incinerated (19%), or mismanaged (22%) [15].

Thereby, circular strategies - including plastics recycling - are key for the environment. Circular strategies are projected to reduce plastic waste by up to 80%. By keeping plastics in a closed loop, circular strategies prevent plastics from entering landfills, waterways, and ecosystems. This minimizes the harmful effects of microplastics on marine life and biodiversity. By reusing and recycling plastics, circular strategies reduce reliance on finite resources like fossil fuels. This enhances resource efficiency and reduces greenhouse gas emissions associated with virgin plastic production. Circular approaches can significantly lower greenhouse gas emissions - by up to 40% according to some estimates - helping industries align with global climate goals. Besides the environmental benefits, transitioning to a circular economy reduces material costs, enhances supply chain resilience, and creates new business opportunities. By 2040, these new business opportunities could save $200 billion annually and create 700,000 additional jobs globally [16, 17, 18, 19].

Therefore, Section 1.1 describes circular strategies for plastic waste, including their impact on circularity and an example. Section 1.2 focuses on recycling, as this has the highest impact in the next decades due to all plastics already produced.

Figure 1.2 9R Framework prioritizing the circular economy strategies according to their levels of circularity [20]

Various approaches, known as R-strategies, have been developed to achieve less resource and material consumption in product chains and make the economy more circular. The 9R Framework presents 10 circular strategies ordered from high circularity (low R-number) to low circularity (high R-number). A higher level of circularity of materials in product chains means that, in principle, smaller amounts of natural resources are needed to produce new (primary or virgin) materials. Therefore, whenever possible, strategies with lower numbers should be prioritized to minimize waste and maximize resource efficiency [20, 21].

Figure 1.2 presents the 9R Framework as applied to plastics. It outlines each R-strategy, describing its general concept, its specific impact on plastics, and providing a relevant example for each strategy.

The application of reduction and reuse strategies for plastics is the most favorable in the context of circular economy. However, for plastics specifically, there are certain limits when it comes to reduction and reuse. As described in the introduction of this chapter, plastics have become the most important raw material for a variety of products and applications and are partially irreplaceable. Not all plastic can be eliminated without compromising safety, hygiene, or efficiency (e. g., medical syringes, food preservation). Furthermore, many plastic products are designed for single use, making reuse impractical or unsafe. Packaging in the food industry is often non-reusable due to contamination risks.

If plastic waste cannot be prevented, three ways of handling plastic waste exist, which are landfilling, incineration with energy recovery (waste-to-energy - WTE), and recycling. Compared to landfilling and WTE, recycling conserves resources, reduces energy consumption, and minimizes carbon emissions compared to producing new plastics [22].

The general cyclic recycling process involves three main steps:

1. Collecting the recyclables

2. Processing the recyclables (mechanical or chemical)

3. Turning the recyclables into new products

After collecting the recyclables via curbside collection, drop-off programs, buyback operations, and container-deposit systems, they are transported to material recovery facilities (MRFs), mixed-waste processing facilities, or mixed-waste composting facilities [23, 24]. High-tech MRFs are characterized by the automated separation of unsorted recyclables using eddy currents, magnetic pulleys, optical sensors, and air classifiers, reducing manual sorting, see Section 2.3.2. Automatic sorting supports and simplifies recycling and enhances its economic profitability [23].

Despite this necessity for recycling, only 9% of plastic waste is recycled globally. There are three major reasons for this: contamination, downcycling, and sorting. First, the contamination of mixed plastics and impurities hinder recycling efficiency. Second, recycling lowers the quality of plastics and their properties, limiting their applications. Third, sorting of certain plastic types can be technically challenging or is economically not feasible yet.

To close the loop and achieve the advantages of circular economy and plastics recycling, new recycling technologies, including chemical recycling, offer potential solutions to both increase the recycling rates and the economics behind the process, but require further development. Furthermore, effective regulations (e. g., extended producer responsibility, waste sorting mandates) can boost recycling rates. Countries with advanced recycling policies, like Germany, have achieved plastic recycling rates of 68% for packaging waste in 2023 [25].

Therefore, this book summarizes in Chapter 2 the most relevant plastic recycling techniques, as well as plastic characterization methods (Chapter 3), analyzes both economic and environmental aspects of different recycling methodologies (Chapter 4), gives insights into global policies and processes (Chapters 5 and 6), and gives an outlook regarding the future of plastics recycling (Chapter 7).

References

[1] PlasticsEurope. Plastics - The Facts 2015: An analysis of European plastics production, demand and waste data. PlasticsEurope. 2015. pp. 1-30.

[2] Niessner, N. Recycling of Plastics: Hanser: Munich. 2022.

[3] Baur, E., Drummer, D., Osswald, T. A., and Rudolph, N. Saechtling Kunststoff-Handbuch: Eigenschaften, Verarbeitung, Konstruktion: Hanser: Munich. 2022.

[4] Matthews, C., Moran, F., and Jaiswal, A. K. A review on European Union's strategy for plastics in a circular economy and its impact on food safety. Journal of Cleaner Production. vol. 283. 2021. 125263.

[5] Ncube, L. K., Ude, A. U., Ogunmuyiwa, E. N., Zulkifli, R., and Beas, I. N. An overview of plastic waste generation and management in food packaging industries. Recycling. vol. 6. 2021. p. 12.

[6] Bailo, C., Modi, S., Schultz, M., Fiorelli, T., Smith, B., and Snell, N. Vehicle Mass Reduction Roadmap Study 2025-2035. Center for Automotive Research: Detroit, MI. 2020.

[7] PlasticsEurope. Plastics - the...