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Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities (2023)

Chapter: Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure

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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Appendix H The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure Hasini Siriwardana, Milena Rangelov, Paul Rikhter, and Sangwon Suh VitalMetrics INTRODUCTION Background The word “plastics” is a colloquial term for a wide range of synthetic or semisynthetic polymer materials that may be shaped when soft and then hardened to retain the given shape (Science History Institute 2022). Due to the heterogeneity of polymers and the versatility of their properties, plastics are used to produce a wide variety of products (Thompson et al. 2009). The production of plastics has increased dramatically over the past 70 years, from 2 million tons in 1950 to 368 million tons in 2019, and it is expected to reach about 600 million tons in 2025 (Heinrich Böll Foundation 2019). Increasing global population and average income drives the continuous escalation in the amount of plastic being used and wasted. Nearly half of the plastics waste is generated in Organisation for Economic Co-operation and Development (OECD) countries (OECD 2022a, 2022b), and it is esti- mated that only about 9 percent of the world’s plastic is recycled annually, with more than 80 percent ending up in landfills or in the natural environ- ment. Additionally, 4 to 12 million metric tons of plastics waste find their way into the oceans every year (Jambeck et al. 2015). The amount of aver- age annual plastics waste per capita varies regionally: in the United States, 325

326 RECYCLED PLASTICS IN INFRASTRUCTURE it is 221 kg, 114 kg in European OECD countries, and 69 kg in Japan and Korea combined (OECD 2022c). Packaging, buildings, and construction represent the largest end-use market of plastic, accounting for more than 59 percent of the market share, while the third biggest end-use market is the automotive industry, at 9.6 percent (Plastic Soup Foundation 2020). Though plastics have brought many benefits to human well-being and materials welfare, the production, consumption, and end-of-life manage- ment of plastics have raised concerns ranging from persistence in the en- vironment, to marine debris, to human health risks, to greenhouse gas emissions, among others (Andrady 2003; Chamas et al. 2020; Gavigan et al. 2020; Hahladakis et al. 2018; Halden 2010a; Ryberg et al. 2019; Zheng and Suh 2019). Plastic generally takes between 500 and 1,000 years to degrade into microplastics, often without fully degrading, which poses yearly economic costs of US$6 to US$19 billion by its impacts on tour- ism, fisheries and aquaculture, and cleanups (UNESCO Intergovernmental Oceanographic Commission 2022). The specific surface degradation rate for high-density polyethylene (HDPE) in the marine environment ranges from near zero to approximately 11 μm per year, while polylactic acid (PLA) degrades approximately 20 times faster than HDPE on land, but the degradation rates of HDPE and PLA are similar in the marine environment (Chamas et al. 2020). In addition to the slower pace of degradation and microplastic generation, end-of-life plastics contaminate waterways and aquifers, limit landfill areas and generate noxious odors, and emit harmful gasses and hydrocarbons during incineration (Devasahayam et al. 2019). With the rising concern over environmental effects of plastics waste, an increasing interest to find venues for a suitable reuse of end-of-life (EoL) plastics has occurred over the past years. The global recycled plastic market was valued at US$47.6 billion in 2022, and the expected growth by 2030 is US$69.2 billion (Grand View Research 2022). EoL plastics are used in vari- ous industries, such as food packaging, medical materials manufacturing, mobile components manufacturing, agricultural pipes manufacturing, and toy manufacturing (Grigore 2017). Personal hygiene products, such as elec- tric trimmers and shavers, along with automotive components and clothing products manufactured from EoL plastics, are the major application areas that are driving the segment growth (Grand View Research 2020). Recycled polyethylene terephthalate (PET) is the most widely recycled resin glob- ally and finds the highest usage in fiber applications in the textile industry (MarketsandMarkets 2022). Due to the increased consumption of plastics worldwide and with the enactment of the National Sword Policy by China that closes the borders to import waste plastics from other countries, there is a growing interest in exploring the viability of using EoL plastics in in- frastructure projects. Because of its widespread use, asphalt is especially ex- plored as a potential option for the local use of EoL plastics (Giustozzi and Nizamuddin 2022). Some types of waste plastics, such as soft and flexible

APPENDIX H 327 plastics, do not have a purpose in the end market, while rigid plastics are in much higher demand. Soft and flexible plastics continue to be a significant concern because their repurposing is challenging (Austroads 2019). Increasing plastic recycling may lower the need for virgin plastic pro- duction, and thus corresponding residual emissions of plastic manufac- turing and EoL treatment (Zibunas et al. 2022). Zheng and Suh (2019) estimated 49 MMT CO2e generation from the plastic recycling process itself. If the displacement of carbon-intensive virgin polymer production by recyclates is considered, the greenhouse gas (GHG) emissions of recycling would go down to −67 million metric tons (MMT), and the total emis- sions from the EoL stage would be reduced from 161 to 45 MMT CO2-eq (Zheng and Suh 2019). Zibunas et al. (2021) specified that the market- ready technologies of mechanical and chemical recycling (pyrolysis) can enable net-zero GHG emissions from plastic production, and in 2037, at a carbon price of US$118/t CO2-eq, incentives would be sufficient to shut down the remaining waste incineration of nonpackaging plastics waste and all nonpackaging waste is recycled via pyrolysis (Zibunas et al. 2021). Aside from chemical recycling processes, there is an increasing interest in reusing the waste plastics materials through physical recycling. Resulting plastics recyclates can be used in many sectors, including the above-mentioned au- tomotive, packaging, textile, electronics, and infrastructure. In particular, infrastructure implementation has garnered attention in the past couple of years for several applications. EoL plastics have strong competition from virgin plastics in terms of quality and application. For instance, there are some limitations of the use of EoL plastics for food-grade packaging applications because of safety concerns related to their contaminants from their previous use (MarketsandMarkets 2022). Nevertheless, there is a growing demand for EoL plastics for many purposes. PET is used in applications such as carpet fibers, geotextiles, packag- ing, and fiber fill because unlike other polymers, recycled PET can be produced and then is directly suitable for contact with food if it is submitted to fur- ther decontamination steps such as superclean processes (Nkwachukwu et al. 2013). Grand View Research (2022) also mentioned that recycled PET is used in various applications across several industries, such as in the packaging of water, oils, pharmaceuticals, and carbonated drinks. They have further stated that personal hygiene products, such as electric trimmers and shavers, along with automotive components and clothing products manufactured from EoL plastics are the major application areas that are driving the segment growth. The infrastructure sector is material- and resource-intensive, since the construction and maintenance of infrastructure elements such as pavements (highway, airports, ports) and structures (bridges, culverts, retaining walls) utilize vast amounts of materials. Infrastructure is also a big consumer of recycled materials due to cost effectiveness. Composite materials such as asphalt and concrete already use granular materials (different types of

328 RECYCLED PLASTICS IN INFRASTRUCTURE aggregates), and a portion of aggregate is often replaced by recycled mate- rials or industrial waste products (Williams et al. 2020). Asphalt materials are commonly modified by the use of different polymers, and EoL plastics can potentially provide new sources of polymer modification (Nizamudin et al. 2021). Concrete and cementitious composites are often batched with industrial wastes such as fly ash and slag cement. Because of the binding properties of Portland cement, these otherwise hazardous materials are safely incorporated into concrete with no concerns of harmful leaching. All these reasons make the infrastructure an interesting venue for repurposing some of the waste plastic streams. Accordingly, a closer look into the ma- turity of such practice along with its environmental, economic, and social repercussions merits consideration. Objectives This study aims to explore the effectiveness of EoL plastic applications in highway infrastructure through the review of the current literature. The fo- cus is placed on the evaluation of environmental benefits and repercussions of plastics reuse in highway materials and other related applications, mainly asphalt and Portland cement concrete. The study focus within the broader context of waste plastic EoL treatments is shown in Figure H-1. The three main EoL routes for plastics waste are landfilling, combustion with energy recovery, and recycling. Recycling can be closed-loop recycling (the reuse of plastics recyclates in the new plastics production) or open-loop recycling (the FIGURE H-1 End-of-life pathways of plastics. NOTE: Percent of end-of-life plastics in various routes pertain to the United States and originate from USEPA’s Facts and Figures about Materials, Waste and Recy- cling. Plastics: Material-specific. SOURCE: Adapted from USEPA (2020).

APPENDIX H 329 reuse of plastics recyclates in the production of other types of products, such as textiles, electronics, or infrastructure, which is the focus of this study). METHODS The literature review conducted for this study was based on the comprehen- sive search of the literature in sources such as Google Scholar, Web of Science, and Google. To curate a list of the most relevant studies in a comprehensive way, keyword combinations described as follows were implemented. The terms “plastics,” “plastics waste,” and “recycled plastics” were used jointly with “infrastructure,” “plastic roads,” “construction,” and “transporta- tion” to capture the recycled plastic utilization information on infrastructure. Moreover, specific terminology pertaining to types of recycling technologies, environmental impact categories, and life-cycle stages was used in the search. Select terms included “recycling,” “upcycling,” “downcycling,” “reusable,” “single-use,” “GHG emissions,” “microplastic,” “nanoplastics,” “leachate,” “acidification,” “ocean plastic pollution,” “impacts,” “supply-chain,” “lo- gistics,” “life cycle analysis (LCA),” and “life cycle cost (LCC),” as well as combinations of these words, such as “recycled plastics in infrastructure,” “recycled plastics,” “end of life plastics,” “plastics waste,” “plastics waste in pavements,” “plastics waste LCA,” “infrastructure LCA,” “waste plastic leachate,” “microplastic pollution,” “construction,” “asphalt LCA,” “con- crete LCA,” “recycled plastics in asphalt,” “recycled plastics in concrete,” “reclaimed asphalt pavement,” “recycled asphalt shingles (RAS),” “recycled asphalt pavement (RAP),” and “recycled materials.” To evaluate the geo- graphical distribution of the studies, search terms also included geographic regions (e.g., Europe, the United States, and Asia). Articles that addressed recycled plastics were considered relevant and were included in the further analysis. Selected were articles published in or after 2010; however, seminal and highly cited articles published prior to 2010 were also included based on their relevance. Reports and web-based sources that were determined to be relevant but not covered by the keyword searches were manually added to the list. The final literature list included 11 LCA studies, 24 other peer-reviewed articles, and 23 other sources from academia, government, and consultancies. See Annex H-1 for a complete list of data sources used in this review.  Each literature source was analyzed with regard to its objectives, methodology, results, and main findings. The key identified topics that were used to structure this report include feasibility and benefits of using EoL plastics for infrastructure projects (18 references), EoL plastic types and amounts used in infrastructure (9 references), challenges of using EoL plastics in infrastructure (14 references), need for further innovations (7 references), LCA studies relevant to EoL plastics in infrastructure projects (11 references), and infrastructure applications (66 references). The break- down and timeline of the relevant sources found is shown in Figure H-2.

330 RECYCLED PLASTICS IN INFRASTRUCTURE In the following sections, we will provide an overview of the current use of EoL plastics in infrastructure projects, environmental and social ben- efits of using EoL plastics, challenges of using EoL plastics for infrastructure projects, relevant LCA studies, and further innovations. More details on terms and definitions discussed in the report are in Annex H-1. We will first review the current status of use of EoL plastics in infrastructure projects all around the world. Following that, we will analyze the types and amount of EoL plastics used for infrastructure projects, purpose of using recycling plastics as an alternative, and other recycled materials currently used in the infrastructure projects. CURRENT USE OF EoL PLASTICS IN INFRASTRUCTURE PROJECTS This section provides a comprehensive overview of the types and amounts of EoL plastics used in infrastructure projects, the purpose of using EoL plastics in infrastructure, and other recycled materials currently in use in infrastructure projects. Types and Amount of EoL Plastics Used in Infrastructure Projects Annex H-1 indicates the results of research conducted using different types of plastics, their potential use for infrastructure, and waste plastic FIGURE H-2 Timeline of the types of relevant literature found on the use of EoL plastics in infrastructure applications.

APPENDIX H 331 content in each mixture. The literature sources specific to the use of EoL plastics in asphalt mixtures, which is the area with the highest availability of research studies, are shown in Annex H-1. The listed studies mainly include the evaluation of different aspects of engineering performance. Two typical ways to integrate EoL plastics into asphalt mixtures are wet and dry processes (Willis and Yin 2022). In the wet process, asphalt binder is combined with EoL plastics, while in the dry process, plastic pellets are added directly into the mix, typically as a partial replacement for the aggregate. The studies focused on the wet process of modification specify that the investigated dosages range between 0.5 and 10 percent per binder weight, while the optimal dosages are typically reported between 3 and 6 percent. In terms of dry process, literature specified percentages between 0.1 and 10 per weight of the aggregate. While the dry process of plastics incorporation into the mix enables higher amounts of waste plastics to be reused, the wet process is typically found to be favorable from the mixture performance standpoint. The literature sum- mary indicates that polyethylene (PE) is the most commonly investigated plastic type for infrastructure projects. Experimental results revealed that the addition of PE can produce performance benefits, including increase of softening point, rheological improvements of binder, as well as the increased mixture ductility, stiffness, and rutting resistance. The majority of the reported projects are at the laboratory testing stage, and only a few countries such as Australia, India, the United Kingdom, Ghana, Ethiopia, the Netherlands (Parson 2021; Sasidharan et al. 2019; Smith 2018; White and Reid 2018), and Italy (Giarrusso 2018) have used recycled waste plastics for road construction, for pavements, and in railway sleepers at a commercial scale. The Purpose of Using EoL Plastics in Infrastructure Sustainability is typically considered through the balance of the triple bottom line, which includes environmental, economic, and social con- siderations. Recycling of plastics has certain environmental benefits; however, it may have economic and engineering repercussions that can only be determined through research and the evaluation of quantita- tive performance metrics throughout the life cycle (Willis et al. 2020). Construction companies can save money while enhancing sustainability because EoL plastic may be less energy-intensive and can be cheaper than certain construction materials. Such a practice also gives plastic a new life beyond the landfill, which supports the principles of the circular economy (Acme 2022). Alternative methods and materials to repur- pose waste plastics that can be utilized in civil infrastructures, such as

332 RECYCLED PLASTICS IN INFRASTRUCTURE wood–plastic composites, concrete blocks, mortars, and incorporating plastics waste into asphalt pavements, are today possible and sustainable practice (Eskandarsefat et al. 2022). In a 1-year study, it was revealed that plastic building and construction materials save 467.2 trillion Brit- ish thermal units of energy over alternative construction materials, and that is enough to meet the average annual energy needs of 4.6 million U.S. households (ACC 2022). Even though the experience in real use of EoL plastics in infrastructure projects is quite limited, research studies demonstrated some benefits in terms of improved stiffness, strength, and durability (e.g., Sasidharan et al. 2019). It is therefore worth investigating the potential feasibility and benefits of waste plastics reuse in infrastruc- ture applications. Other Recycled Materials Currently Used in Infrastructure Projects Recycled crushed concrete, crushed brick, crushed glass, recycled steel, reclaimed asphalt pavement (RAP), reclaimed asphalt shingles (RASs), and crumb rubber products are commonly used in construction to supplement traditional aggregate and sand products extracted from quarries (ecologiQ 2022). The use of these reclaimed and recycled materials may decrease the incentives of adding waste plastics as a substitute to conventional materi- als. Figure H-3 summarizes the current utilization of RAP in each U.S. sector. Reclaimed nonplastic materials are already highly utilized in the infra- structure sector, and their use is continuously increasing, with the average percent RAP used by all sectors increased to 21.3 percent (NAPA 2020). FIGURE H-3 RAP use and the average percentage of RAP utilization by sector.

APPENDIX H 333 ENVIRONMENTAL AND SOCIAL BENEFITS OF USING EoL PLASTICS FOR INFRASTRUCTURE PROJECTS Life-cycle assessment (LCA) is a method to quantify the environmental im- pacts of products and processes throughout their life cycle, including ex- traction of raw materials, manufacturing, transportation, consumption, and disposal. LCA has been defined in accordance with the ISO standards 14040 (ISO 2006a) and 14044 (ISO 2006b). Overall, LCA is considered a suitable tool to elucidate the processes with critical environmental contributions and provide insights into the potential for the reduction of environmental impacts. In the domain of the use of EoL plastics in infrastructure, the literature commonly identifies the “environmental friendliness” of such a solution, particularly the associated reduction of plastics waste, as the key motiva- tion. However, while multiple studies investigate the effect of EoL plastics addition on different aspects of material performance (most commonly mechanical performance), comparable assessment of environmental impacts is less common in the literature. The findings of review studies indicated that the assessment of sustainability-related indicators, both economic and environmental, is a notable future research need (Brasileiro et al. 2019; Pouranian and Shishehbor 2019; Willis et al. 2020). A summary of LCA studies on the topic conducted to date is presented in the following sections. LCA Studies on Using EoL Plastics in Asphalt Integration of plastic into asphalt is the most common application of EoL plas- tics in infrastructure and has been studied most thoroughly. Yu et al. (2014) performed a comparative analysis of cradle-to-gate greenhouse gas emissions and energy consumption of asphalt mixtures modified with recycled polypro- pylene (PP) and rubber to the mixture with a polymer-modified binder. Their results showed that the mix with rubber and recycled PP has lower impacts than the conventional polymer-modified mix (Yu et al. 2014). This study also mentioned the difference in performance between the two mixes; however, since the analysis was cradle-to-gate, the mixture performance was not part of the assessment. Santos et al. (2021) investigated the impacts of recycled PE in modified asphalt binder and asphalt mixtures as a partial aggregate replacement for the Australian context using LCA. Their results indicate that the asphalt binder modified with EoL plastics is environmentally preferential compared to the binder modified with virgin polymer (Santos et al. 2021). For in- stance, binder modified with EoL plastics have a global warming potential (GWP) 1 to 2 percent higher than the virgin binder and 1 to 19 percent lower than polymer-modified binder (Santos et al. 2021). This study was conducted for the Australian context and utilized the primary data for waste plastics recycling into pellets collected directly from the recycling

334 RECYCLED PLASTICS IN INFRASTRUCTURE facilities in Victoria, Australia. Asphalt mixtures with PE added through the dry process have higher environmental impacts relative to the hot-mix asphalt (HMA) baseline (e.g., 5 to 139 percent increase in GWP). How- ever, the identified advantage of the dry process is that it can help consume higher amounts of waste plastic (Santos et al. 2021). Rangelov et al. (2021) performed LCA of asphalt mixtures and pave- ment sections with recycled PE added into the mix via dry process. Their results indicated that the environmental impacts of PE-modified mixtures are higher than that of conventional HMA and lower than that of polymer- modified mixes (Rangelov et al. 2021). The same study evaluated what changes in pavement thickness or maintenance cycles of pavements with re- cycled plastics (artifacts of the improved performance that can be achieved in specific contexts) can make them comparable to conventional asphalt or polymer-modified pavements (break-even analysis). In doing so, this study sheds light on potential trade-offs between cradle-to-gate impacts and life- cycle performance (Rangelov et al. 2021). Lastra-González et al. (2021) performed LCA of asphalt mixtures with binder modified with 25 percent of PE from copper cables and flexible packaging film. The end-point environmental indicators calculated in their study demonstrated that the modified mixtures could be environmentally beneficial compared to conventional asphalt mixture, while the improved performance and extended service life have a potential to increase achieved benefits (Lastra-González et al. 2021). One methodological choice from the study by Lastra-González et al. (2021) that may have an influence on these results is the allocation method—namely, this study utilized the avoided burden of plastic incineration for PE recycling when it is used as an asphalt modifier. The use of recycled PE is associated with the benefits of avoided incineration, resulting in lower impacts of mixtures with recycled PE. Oreto et al. (2021) performed LCA of four types of asphalt mixtures with binder modified with EoL plastic pellets and the addition of different types of recycled aggregates. This study mapped all the mixtures onto a four-quadrant scheme based on (a) environmental impacts and (b) service life estimated based on the experimental results, thereby identifying the trade-offs (or a lack thereof) between environmental impacts and longevity (Oreto et al. 2021). The results of their study indicated that the mixture with PE binder modification has extended service life without significantly aggravating the environmental profile (Oreto et al. 2021). Praticò et al. (2020) analyzed environmental impacts of asphalt mixtures with various combinations of recycled materials and compared them to the polymer-modified asphalt baseline. Their results show that the impacts of the mix with RAP and mixed plastics waste granules added through the dry process are somewhat lower than that of a reference mix (Praticò et al. 2020). Their study, however, does not provide any commentary as to how recycled material addition impacts mixture performance (Praticò et al. 2020).

APPENDIX H 335 A summary of the revised literature on the LCA of asphalt mixtures with EoL plastics is provided in Table H-1. As shown in Table H-1, most identified studies were published after 2020, indicating the increasing interest in this topic. Most studies agree with the findings that asphalt mixes with the addi- tion of EoL plastics typically have higher impacts than the mixtures using neat (virgin) asphalt binder. However, in comparison with the mixtures that utilize the virgin polymers as asphalt binder modifiers, mixtures with EoL plastics can be environmentally favorable. Most LCA studies investigated recycled PE. From the perspective of cradle-to-gate assessment, getting accurate data on plastics processing is an important need. Presently, the primary data for many of the polymer additives including different types of EoL plastics is lacking in general. Santos et al. (2021) utilized the primary data collected from plastics recycling facilities in Australia, which is the data of the high- est granularity and specificity. Rangelov et al. (2022) advocated for the creation of Environmental Product Declarations (EPDs) for recycled plastics additives to provide for the specific, standardized data for asphalt LCA. From a cradle-to-grave perspective, mixture performance is an impor- tant aspect needed to outline LCA. The advances in asphalt material sci- ence, as well as the testing of long-term performance via laboratory tests TABLE H-1 Summary of LCA Studies on Asphalt Materials with EoL Plastics Name of the LCA Study Scope Plastics Type Wet or Dry Process Allocation Protocol Evaluated Environmental Impacts Lastra- González et al. (2021) Cradle-to- gate PE Wet Avoided burden (incineration) End-point indicators: human health, ecosystem diversity, resource availability Oreto et al. (2021) Cradle-to- grave PET Wet and dry Cutoff AP, EP, GWP, ETOX, HT, IR, PM, SCP Praticò et al. (2020) Cradle-to- grave Mixed municipal waste Dry Cutoff AP, EP, ETOX, HT, GWP, ODP, SCP Rangelov et al. (2021) Cradle-to- grave PE Dry Cutoff AP, EP, GWP, ODP, SCP Santos et al. (2021) Cradle-to- grave PE Dry Cutoff AP, EP, GWP, ODP, SCP Yu et al. (2014) Cradle-to- gate PP Wet Cutoff GWP NOTE: AP = acidification potential; EP = eutrophication potential; ETOX = freshwater ecotoxicity; GWP = global warming potential; HT = human toxicity; IR = ionizing radiation; ODP = ozone depletion potential; PM = particulate matter; SCP = smog creation potential.

336 RECYCLED PLASTICS IN INFRASTRUCTURE and in situ test sections, would enable more reliable LCA results and sup- port for life-cycle thinking. Future recyclability of asphalt with the addition of EoL plastics is another area that necessitates future research. Lastly, while most LCA studies to date are attributional (i.e., focused on assessing the impact of product or process attributed to the functional unit), there is also a need for the consequential LCA in this domain (Santos et al. 2022). Consequential LCA focuses on estimating consequences of a deci- sion—in this case, a decision to utilize EoL plastics in the infrastructure, as opposed to the use of EoL plastics elsewhere. Such a study would demand the use of economic data and the knowledge of how increased demand for EoL plastics products in one sector would impact the supply and demand in the re- mainder of the market (Santos et al. 2022). As EoL plastics are not commonly utilized in the infrastructure at this point, such data may not be available or possible to generate with certainty (Santos et al. 2022). Nevertheless, such study would be beneficial to elucidate different possible routes for effective management of waste plastics. Presently, there are several consequential LCA studies in the literature investigating plastics recycling protocols (e.g., Bishop et al. 2021; Cornago et al. 2021; Zhao and Yu 2021); however, no studies to date include infrastructure application of plastics recyclates. LCA Studies on Using EoL Plastics in Concrete and Cementitious Composites In concrete mixtures, EoL plastics are typically utilized as a partial aggre- gate replacement or in the form of fibers that enhance the tensile strength of concrete. As is the case with asphalt, for concrete, most available studies in- vestigate mechanical and other technical properties of concrete, while the envi- ronmental profile is the motivation but not explicitly assessed in the literature. The several available LCA studies are described and summarized as follows. Yin et al. (2016) compared recycled PP fibers from domestic (Austra- lian) waste and industrial sources with steel and virgin PP fibers for concrete reinforcement. The results have shown that recycled PP fibers exhibit lower environmental impacts compared to the new PP fibers, while the industrial recycled fibers are less environmentally intensive relative to the fibers pro- duced using domestic waste PP (Yin et al. 2016). Demirel et al. (2019) performed LCA of self-consolidating mortar with the addition of fly ash and waste glass PET (GP), which is the type of heavy PET that resembles glass and is used for bottle production. GP from the mu- nicipal waste was ground and used as a partial cement replacement along with the fly ash (Demirel et al. 2018). Their results indicated that mixes with the partial cement replacement with GP have lower impact compared to the mix with plain Portland cement. However, it is not recommended to use more than 9 percent cement replacement with GP because otherwise strength and workability can be compromised (Demirel et al. 2018).

APPENDIX H 337 Tahanpour Javadabadi (2019) conducted a study to evaluate the use of recycled PET as a fine aggregate replacement in concrete. His results in- dicated that, when no avoided burden is accounted for, the environmental advantage of concrete with recycled PET as aggregate is in land use (Tah- anpour Javadabadi 2019). When the benefits of the avoided burden are considered, namely, avoiding incineration, environmental benefits of the alternative with recycled PET aggregates are more pronounced (Tahanpour Javadabadi 2019). Goh et al. (2022) investigated the environmental impacts of concrete made with the use of electronic waste (e-waste), which is a mixture of different types of plastic with a low recovery value, as a partial replacement for the coarse aggre- gate. The implemented replacement rates were 20 percent, and mixes included different combinations of cement and supplementary cementitious materials (Goh et al. 2022). The results of this study indicated a reduction in environmen- tal impacts of approximately 4 percent when 20 percent of coarse aggregate is replaced with e-waste at equal cementitious content (Goh et al. 2022). A study by Signorini et al. (2022) focuses on the reuse of synthetic fi- bers obtained from recycling artificial turf consisting of polyolefin synthetic fibers for the application in concrete. The LCA part of the study focused on the fiber production and yielded the conclusion that recycled fibers are more environmentally friendly than the virgin fibers (Signorini et al. 2022). These studies are summarized in Table H-2. TABLE H-2 Summary of LCA Studies on Concrete and Cementitious Composite Materials with EoL Plastics Name of the LCA Study Scope Plastics Type Application Allocation Protocol Evaluated Environmental Impacts Goh et al. (2022) Cradle-to- gate e-waste Aggregate replacement Cutoff AP, EP, GWP, ETOX, HT, IR, PM, SCP Demirel et al. (2019) Cradle-to- gate PET Cement replacement Avoided burden (landfilling) AP, EP, GWP, ETOX, HT, IR, PM, SCP Javadabadi (2019) Cradle-to- gate PET Fine aggregate replacement Avoided burden (incineration) AP, EP, GWP, HT, ODP, PM Signorini et al. (2022) Cradle-to- gate Polyolefins Fiber Cutoff AP, EP, GWP, SCP Yin et al. (2016) Cradle-to- gate PP Fiber Cutoff GWP, EP NOTE: AP = acidification potential; EP = eutrophication potential; ETOX = freshwater ecotoxicity; GWP = global warming potential; HT = human toxicity; IR = ionizing radiation; ODP = ozone depletion potential; PM = particulate matter; SCP = smog creation potential.

338 RECYCLED PLASTICS IN INFRASTRUCTURE FEASIBILITY AND CHALLENGES OF EoL PLASTICS USE FOR INFRASTRUCTURE PROJECTS The increasing interest in the use of EoL plastics in infrastructure has accelerated the rate of related research and development. In terms of de- ployment, however, the efforts are still limited. The report published by National Asphalt Pavement Association (NAPA) identified approximately 200 projects of asphalt pavements with recovered plastics (Willis et al. 2020). Novophalt was the product most typically utilized in these projects, primarily from the late 1980s to the early 2000s. However, the systematic tracking and overview of the long-term performance of these sections was not conducted (Willis et al. 2020). Some limited assessment revealed that the addition of plastics improved the rutting performance, while the cracking performance was comparable to that of the conventional asphalt. Newer test sections constructed in various countries, including Australia, Canada, Indonesia, the Netherlands, New Zealand, the United Kingdom, and the United States, exhibit satisfactory performance; because they were new, claims about the longevity and long-term performance cannot be made with certainty. The following sections summarize the specific aspects of feasibility and challenges. Plastics Recycling Collection of plastics waste can be done by “bring-schemes” or through curbside collection. For instance, in terms of the overall consumption, 30 to 40 percent of post-consumer plastic bottles are recovered, as a lot of this sort of packaging comes from food and beverage consumed away from home (Hopewell et al. 2009). The effective “on-the-go” and “office recycling” col- lection systems if overall collection rates for plastic packaging are to increase were recommended as a feasible strategy (Hopewell et al. 2009). Supply chain instability has become a challenge for businesses since the beginning of the COVID-19 pandemic, and plastics recyclers had to adjust on short notice (Hockensmith 2022). Additionally, a lack of functional integration, financial constraints to reverse logistics, managerial support and leadership style, poor teamwork and communication with supply chain members such as local manufacturers, and product quality control problems are the major challenges in implementing reverse logistics (Abdissa et al. 2022). Asphalt Mixture Design Currently, there are no established specifications determining the source of plastics waste, recycling process, and properties of plastics recyclates that would make them suitable for use in road pavement applications (Santos

APPENDIX H 339 et al. 2022). Post-consumer waste plastics typically have high levels of contaminants and intentionally added substances that require innovative decontamination and segregation technologies to prepare recyclable mate- rial for suitable applications (da Silva et al. 2021). The complex composi- tion of some types of plastics such as expanded polystyrene (EPS) makes conventional recycling methods unsuitable. Soft and flexible plastics are not often used in the end market, while rigid plastics are in higher demand (Austroads 2019). At this point, there are no recommendations on the most suitable plastic types and products that can be repurposed in the infrastruc- ture, since the research efforts are not done in coordination. From the perspective of both asphalt mixture design and pavement de- sign, it is not known whether or not conventional methods used for asphalt mixtures and pavements also apply when EoL plastics are integrated into the mix. Some authors indicate that the use of high-modulus mixtures such as the ones with the addition of EoL plastics could be associated with the reduced pavement thickness from the structural design standpoint (Range- lov et al. 2021; Willis et al. 2020). However, further research on asphalt mixture design and pavement design when EoL plastics are used merits consideration in the future. Materials Production In addition to a small-scale production of asphalt mixture with EoL plas- tics in the laboratories, asphalt with RP was produced in the plants at the scale necessary for paving. However, for such production there are a few key considerations. First, there are different types and qualities of EoL plastics available that should be sorted. For instance, post-industrial and post-consumer plas- tics differ in terms of composition, properties, and consistency, uniformity, level of contaminants and other physicochemical characteristics, which should be taken into account (Willis and Yin 2022). The differences in the above-mentioned properties of plastics affect asphalt mixture, but there is no systematic research knowledge to document in which ways (Willis and Yin 2022). Additionally, the EoL plastics must be in a form suitable for addition into the mix. The recyclate must be extruded in a form such as plastic pellets, flakes, or chips, which requires additional processing (Chin and Damen 2019). A critical challenge of the wet process in asphalt mixtures is the pos- sibility of phase separation between asphalt binder and plastics (Qian et al. 2019). To mitigate that effect, producers have used the mobile high-shear blending unit consisting of an agitation tank and mixing tank (White and Magee 2019; Willis and Yin 2022). This blending unit maintains the ho- mogeneity of the modified binder, which is then pumped into the drum mix

340 RECYCLED PLASTICS IN INFRASTRUCTURE with aggregates for the on-site preparation (Willis and Yin 2022). While the blending unit is not difficult to set up, its transport to the site adds to the transportation expenses and complexity with the project scheduling (Willis and Yin 2022). For the dry process, there are several key recommendations regarding the introduction of EoL plastics into the asphalt mix. Inclusion of EoL plastics from the cold conveyor line with the remainder of the aggregate can be associated with hazards because the plastics can reach the flash point and ignite, which is unsafe (Willis and Yin 2022). The inclusion of plastics on the conveyor with RAP is recommended as safer (Willis and Yin 2022). Compared to the wet process, the dry method is simpler and less expensive, but the modified asphalt mixture produced by the dry method can have poor performance (Ranieri et al. 2017). Construction There is concern about lower mixture workability in concrete with EoL plastics due to the addition of plastomers, which are making the mixture stiffer. Addition of warm mix additives is mentioned as a potential solu- tion that can serve as a compaction aid and enable improved construction quality (Willis and Yin 2022). A field case study by Angelone et al. (2022) demonstrated the importance of worker’s training, as the pilot section that was paved first with the mix with EoL plastics exhibited some premature rutting and spalling. Another critical aspect related to construction feasibility is the workers’ safety because of the toxic fumes that can be released during asphalt produc- tion at high temperatures. The emissions spectrum from asphalt at elevated temperatures includes reactive organic gases (ROGs) and particulate matter (PM). Volatile organic compounds (VOCs), such as toluene, 4-ethyltoleune, xylene, 1,3,5-trimethylbenzene, ethylbenzene, benzene, 2-dibromoethane, and semivolatile organic compounds, which include several polycyclic aro- matic hydrocarbons (PAHs) and alkanes are included in the ROGs cat- egory. These compounds can cause health risks to workers; however, the severity of health risks may also be due to ambient conditions on the site (e.g., wind speed, wind direction, working temperature). The addition of EoL plastics into asphalt mixes poses additional concerns because plastics release various fumes when heated and not combusted. When polymers are processed under high temperature, they can release toxic emissions such as chloride, formaldehyde, toluene, and ethylbenzene (Austroads 2019). The presence of perfluoroalkyl and polyfluoroalkyl substances (PFASs) has also raised health and safety concerns regarding the use of certain types of EoL plastics in asphalt (Willis et al. 2020). Workers exposed to asphalt mixtures incorporating waste plastic materials complained more of irritation to their

APPENDIX H 341 eyes, throat, and skin than workers exposed to conventional asphalt mix- tures (Väänänen et al. 2006; Wu and Montalvo 2021). Several laboratory studies investigated the difference between various types of asphalt binder. For example, Boom et al. (2022) compared the PAH release between as- phalt binder with and without the addition of PE, both virgin and recycled. Their results indicate that the inclusion of PE yields decrease in PAH fumes release (Boom et al. 2022). However, it is noteworthy that the duration of the tests were 4 hours, which is markedly shorter than the typical 8- to 10-hour workday at the asphalt construction site (Boom et al. 2022). On the other hand, laboratory emissions are concentrated and therefore may be unrepresentative of that at the site (Boom et al. 2022). White (2019) reported that the released fumes mainly originate from the asphalt binder; therefore, the addition of EoL plastics is not expected to have detrimental effects. The production at high temperatures makes some plastic types such as PVC unsuitable for use in asphalt because of the associated chloride emissions (Chin and Damen 2019). Use and Maintenance During the pavement use phase, the pavement is exposed to the traffic and environmental loading over the service life. Potential impacts of concern in the use phase include plastics release through the process of abrasion and exposure to sunlight and stormwater. As a result, road dust typically con- tains a variety of particles, including microplastics in addition to microrub- ber particles that originate from tire wear and tear, making up the majority of road dust (Vogelsang et al. 2020). However, some particles are generated due to the road abrasion and consist of asphalt materials, bitumen polymer modifier, and roadway markings (Vogelsang et al. 2020). Therefore, there are concerns that the addition of plastics in the road materials may lead to increased risk of microplastics release through road abrasion. A study by Enfrin et al. (2022) compared the laboratory-scale abrasion tests of asphalt with EoL plastics added via wet and dry processes. This study concluded that plastics addition through the dry process yields higher microplastics release (Enfrin et al. 2019). Aside from the laboratory-scale tests, the constructed test pavement sections are still relatively new, and the compre- hensive evaluation of the use phase impacts is yet to be undertaken. Some limited research indicated that the leachate from the conventional asphalt pavement and pavements with EoL plastics does not differ (White 2019). Leaching of harmful materials and pollutants such as phthalates, bisphenol A, and microplastics are additional environmental concerns (Willis et al. 2020). Chamas et al. (2020) investigated the degradation of plastics on land and in the marine environment; however, degradation of plastics included in pavements is yet to be researched.

342 RECYCLED PLASTICS IN INFRASTRUCTURE The cycles of pavement maintenance are mainly contingent on the pavement performance, which depends on multiple variables, including the material performance, construction quality, local conditions, and subgrade. Because implementation of the use of plastics has been relatively new and assessed mainly in the laboratory, the field performance, especially long term, is not known with certainty. Overall, there is an agreement in the literature that EoL plastics addition improves mixture stiffness and rutting resistance, while the cracking performance (fatigue and thermal) may be compromised. Since cracking is the dominant failure mechanism in the United States, the change in mixture performance brought about by the introduction of plastics may not be the best suited for the current needs (Willis et al. 2020). New research on hybrid mixture design, including both elastomers and plastomers, promises an improved performance and has the potential to leverage the benefits of both additive types simultaneously (Nizamudin and Giustozzi 2022). End of Life Closed-loop recycling is a common practice in the asphalt industry. With more than 87 million tons utilized in 2020, RAP is one of the most recycled materials by mass in the United States (Williams et al. 2020). The use of RAP provides economic benefits because it reduces the consumption of virgin materials, namely asphalt binder, which is the most expensive com- ponent of asphalt mixtures, and virgin aggregates. It is not known if the addition of EoL plastics will have an influence on the future recyclability of asphalt mixtures or how it would impact the quality and utilization of RAP (Willis and Yin 2022). Santos et al. (2022) raised the concern that the recyclability of mixtures with plastics could accelerate the release of microplastics and nanoplastics into the surrounding ecosystems during the asphalt pavement milling operation (Santos et al. 2022). Before wide-scale implementation, the concerns of the future recyclability and RAP quality and management should be addressed. Economic Aspects Even though plastic is often considered inexpensive, lightweight, and du- rable, chemically recycled plastic may not be cost effective without signifi- cant subsidies because of the low price of petrochemical feedstock (Patel et al. 2000). WRAP (Waste & Resources Action Programme) reports the prices of waste plastics in the range £50 to £490 per tonne in July 2019, with prices increasing in recent years. Specific prices included clear PET bottles (£222.50 per tonne), colored PET bottles (£50 per tonne), natural HDPE bottles (£490 per tonne), mixed HDPE bottles (£385 per tonne),

APPENDIX H 343 mixed polymer bottles (£115 per tonne), and LDPE 98:2 film (£275 per tonne) (Coopland and Winter 2021). Unless the bulky and voluminous waste plastics are baled or shredded first, they are costly to transport plus, with a rebate of US$100/tonne, the recycling (HDPE and PP) could cost in the range of US$300/tonne to US$600/tonne of waste material, and the freighting cost may depend on the location of the recyclers and the volume and quality of plastics (Rawtec & EconSearch 2013). Typically, these costs significantly surpass that of the construction industry materials, which may make the use of EoL plastics in infrastructure not cost effective. The pavement industry often functions based on the low-bid principles (Willis et al. 2020). The winning bid is typically selected based on the low- est costs, while the materials have to satisfy specifications and quality assur- ance protocols defined by the agency that is requesting bids. The addition of the plastics in mix designs is associated with cost increases for various reasons. First, plastic pellets suitable for inclusion in the binder or mixture are commercial products and are typically more expensive than typical asphalt mixture constituents, primarily aggregates. Second, the addition of plastics adds complexity to the mixture preparation process, as described later in the appendix. When mixed with asphalt binder, the binder modifica- tion process requires energy and time, as well as the agitation equipment to ensure the homogeneity of the binder (Willis and Yin 2022). Accordingly, mixtures with the addition of EoL plastics may not be cost-competitive with conventional hot-mix asphalt mixtures. However, such mixes could be com- petitive with the polymer-modified mixtures and specialty asphalt mixtures. It is not known, however, if the production rates of specialty mixes could consume EoL plastics in a significant way. From the life-cycle perspective, the cost effectiveness of asphalt mix- tures with EoL plastics depends on the mixture performance after the pave- ment is constructed. Even though the upfront costs may be higher than that of the conventional mixtures, with improved performance and less need for maintenance, asphalt mixtures with EoL plastics can be economically advantageous over the long term. Yao et al. (2022) argued that the durabil- ity of mixtures with EoL plastics is the key to their cost effectiveness over the life cycle. However, with many unknowns related to long-term perfor- mance, economic feasibility cannot be assessed with certainty. Environmental and Social Risks Waste plastics recycling and reuse have been considered a beneficial waste management strategy for reducing environmental impacts and helping pre- vent resource depletion. However, there are direct and indirect social and environmental impacts of waste plastics recycling and utilizing them for other uses. The plastics recycling process is associated with some workers’

344 RECYCLED PLASTICS IN INFRASTRUCTURE safety concerns. Huang et al. (2021) have developed a skin exposure model to assess the health risks of heavy metals in pellets of recycled plastic. Their study revealed that the workers at plastics recycling plants are more likely to get cancer, as the possible carcinogenic risk levels of arsenic and chro- mium in the facilities that recycle plastic are, respectively, 2 and 38 times greater than the unacceptable risk level of 10–4 proposed by USEPA (Huang et al. 2021). The abovementioned health risks of construction workers when exposed to plastics recycling, asphalt production and placement when EoL plastics are used, as well as the potential for microplastics leaching, are examples of other environmental/social risks that are not known with certainty. NEEDS FOR FURTHER INNOVATION With plastics waste pollution leading to calls to actions from a wide range of stakeholders, there is heightened desire to make further innovations to address the waste stream, and infrastructure is one of the industries that may have more application for waste plastics, depending on the feasibil- ity and economic factors discussed above. Despite these limitations, there still exist great prospects for application and technological advancement in all areas, including technological, economic, and operational innovations (Awoyera and Adesina 2020). Furthermore, increased innovations of EoL plastics applications are likely to increase the investments and economic feasibility of different approaches (McKinsey 2020). Technological Innovations Many of the issues faced by EoL plastics applications in infrastructure and other industries are due to feasibility issues, change to detrimental effects to the quality of the material or the lack of effective treatment of the plastic to be suitable for the application. An increase in technological innovations is likely to drive more effective cost reductions and logistics and promote the possibility of these applications (McKinsey 2020). However, a large issue with the current lack of initial investment is the resulting lack of techno- logical innovations for plastic recycling and treatment methods that can be effectively brought to scale. To best address environmental impact reduc- tions, innovation reducing the impact of the current biggest contributors to emissions associated with recycling processes must be addressed. Based on Santos et al. (2021), the pelletization process has the highest contribution to the five environmental impact categories (~93 percent), while shredding and sorting jointly add up to 7 percent. Hence, the im- proved efficiency and innovation in pelletization should induce the improve- ment to the environmental impacts of recycling.

APPENDIX H 345 Another route for innovation focuses on the disposal and allocation of impacts of plastics along with technical feasibility. One innovation dis- cussed in the literature explores the upcycling of waste plastic into waste graphene. Its cradle-to-grave LCA found that the upcycling of plastics waste in this way may lower some of the environmental impacts while maintain- ing some of the technical properties needed in conventional material (Wyss et al. 2022). The study found that high-quality flash graphene can be pre- pared though a rapid and solvent-free synthetic method through the design of a flash Joule heating reactor (Wyss et al. 2022). The graphene can then be incorporated into composites for infrastructure and other applications with improved mechanical properties (Wyss et al. 2022). This process also highlighted the importance of upcycling and the ability to upcycle the mate- rial repeatedly, which is typically not the case for other EoL plastic appli- cations. Further exploration of the ability to upcycle waste plastics would provide reduced environmental impacts across applications. Finally, there is also technological innovation available in sorting. Sort- ing of rigid EoL plastics occurs by both automatic and manual methods (Hopewell et al. 2009). Automated sorting is typically sufficient to sepa- rate plastics from nonplastic materials. Automatic sorting of containers is now widely used by many plastic recycling facilities (Hopewell 2009). The innovations in recycling technologies are represented by detectors and recognition software that collectively increase the accuracy and productiv- ity of automatic sorting such as Fourier transform near-infrared detectors (Hopewell 2009). Other sorting technologies are also advancing and could provide more efficient sorting along with higher-quality EoL plastic output more applicable for industry applications. There is further space for innova- tion to optimize sorting even more than available in current facilities, which sometimes still heavily rely on manual sorting and outdated technologies for their logistics. Innovations in terms of asphalt technology include hybrid mixtures, which leverage the benefits of elastomer and plastomer modifiers and im- prove the overall mixture performance (Nizamudin and Giustozzi 2022). Investigation of new types of compatibilizers aims to overcome the prob- lems of phase separation between the binder and plastics (Nizamudin and Giustozzi 2022). Lastly, the development of accelerated loading test sections and pilot studies with extended performance monitoring were highlighted as the activities that can bridge the gap between research and deployment (Willis and Yin 2022). Cost-Reduction Opportunities There are several areas affected by the substitution of infrastructure and construction materials for EoL plastics, mainly including logistics and the

346 RECYCLED PLASTICS IN INFRASTRUCTURE cost of the materials themselves. However, the majority of innovation is focused on the technical rather than the economic lens. Currently, the cost of EoL plastics ranges from 3 cents to 75 cents per pound depending on the plastic type and treatment condition (Resource Recycling 2021), while the cost of construction materials such as cements is low at about 4 to 6 cents (IBIS World 2022). The cost of each material is increasing, but the cost of EoL plastics is increasing at a higher rate, doubling for some plastic types in a single year (Resource Recycling 2021). However, much of the cost in- crease is not due only to an increased demand for high-quality EoL plastic, but also the lack of investment in recycling facilities (McKinsey 2020). Even though the EoL plastics cost may sometimes be higher than the cost of conventional infrastructure materials, this does not account for the alternative, cost-intensive waste treatment such as incineration or landfilling rather than recycling. The use of plastics waste in infrastructure may result in significant cost savings from reduced waste treatment, as the plastic is stored for a long period of time (Awoyera and Adesina 2020). Furthermore, the application of plastics waste as a mix for insulation can help reduce en- ergy consumption and cost for any piece of infrastructure that may require heating (Awoyera and Adesina 2020). The potential use of EoL plastic as a binder, aggregate, or fiber makes it a viable alternative to conventional con- struction composites (Awoyera and Adesina 2020). While there are some detrimental effects on the performance of the composite, the cost benefits as well as application of waste material can outweigh these effects. Despite the limitations of the application of plastics waste for construction applications there still exists a great prospect of its use with the progression of research and technological advancement (Awoyera and Adesina 2020). Innovation for Logistics and Better Collection In addition to cost benefits resulting from the change in materials used, there is also potential cost reduction through logistics. Because much of the plastics waste may be sourced locally, the transportation distances are lower than those of virgin construction materials, and logistics costs are reduced (Awoyera and Adesina 2020). Further innovation and coordination of lo- cal treatment and sourcing of plastics waste for infrastructure applications can drive logistics and operational costs down. However, this is not always possible owing to a lack of recycling facilities and may require more wide- spread and effective waste plastic treatment. Another potential operational cost-reduction method includes a mixed integer linear programming model, which would minimize both the transportation cost and environmental impact through the use of sustainable reverse logistics network designs for household waste (Bing et al. 2014). This system optimized the placement of plastics waste treatment facilities to reduce initial investment for the

APPENDIX H 347 construction and use of these facilities, while also creating a benefit in the logistics involving plastics waste and EoL plastics. However, this model de- pends on the effective application of these EoL plastics to infrastructure and other industries, and would require significant demand and collaboration. CONCLUSIONS As plastics production remains high and the demand for utilization of waste plastics increases, storing the plastics waste in infrastructure materials and components is one of the available options to deal with the waste generated. The majority of literature covers the EoL plastic applications on pavement materials, primarily asphalt and cement composites. While there is more literature that covers the topic of plastics waste used in infrastructure over the past decade, and especially over the past few years, the literature mainly investigates the engineering performance and does not always provide clear conclusions on the feasibility and different sustainability-related benefits of applications in infrastructure. Table H-3 summarizes some of the key recommendations, challenges and unknowns related to the feasibility of the plastics use in infrastruc- ture. Notably, case studies performed on the laboratory and test section scale have shown the feasibility in general, but further deployment on a broader scale is still associated with many unknowns. Uncertainties related to workers’ safety during production, compaction, and microplastics release through the leachate and stormwater, as well as the future recyclability are the critical questions to address in the future. Additionally, long-term engineering performance and what contexts would be the most suitable for implementations of mixtures modified with EoL plastics are also the examples of notable knowledge gaps. Long-term performance, in particular, has a direct impact on different aspects of sustainability and cost effective- ness, which can substantially influence the extent to which the investigated practice will be implemented in the future. While many articles reviewed implicitly assume sustainability-related benefits of using EoL plastics in infrastructure, quantitative assessments of environmental benefits have rarely been reported. The key takeaways of literature findings pertinent to sustainability are summarized in Table H-4, based on the rating scale given in Annex G-2. The finding in LCA studies vary, but generally the inclusion of EoL plastics increases material-related environmental impacts and infrastructure performance determines if there are benefits over the life cycle. Altogether, there is no clear consensus on the environmental consequences, and several articles bring up the challenges of using plastics waste in pavements, primarily due to human health concerns from leachates, the efficiency of transportation and waste treatment and refinement, and other indirect impacts. From an economic standpoint, there

348 RECYCLED PLASTICS IN INFRASTRUCTURE may be a need for additional incentives for plastics waste use, as it does present some challenges technically and is often more expensive than con- ventional materials used. Furthermore, the infrastructure already has a rela- tively high rate of closed-loop recycling, and increasing EoL plastics used in construction and infrastructure materials may compromise the recycling of other materials. To that end, a consequential LCA investigating different TABLE H-3 Summary of Findings on Feasibility of EoL Plastics in Infrastructure Applications Life-Cycle Stage Key Findings Challenges Unknowns Production Best to introduce into the asphalt mix with RAP and not with the aggregates Possibility of incineration and fume release How to make mix cost-competitive in the low-bid environment Construction Workers’ training is important for the construction quality Workers’ safety due to fumes Construction best practices Use and maintenance Typically improved rutting and aggravated cracking performance Microplastics release through stormwater runoff Long-term performance EoL Accelerated testing facilities may provide useful insights Reuse possibilities at EoL Future recyclability TABLE H-4 Summary of Findings on Sustainability of EoL Plastics in Infrastructure Applications Criteria Environmental Impact of EoL Plastics Social and Economic LCA Studies GHG Impacts Micro- plastics Leachate Social Economic Availability of literature Medium Medium Low Low Low Low Confidence in conclusion Medium Medium Low Medium Low Medium Overall consensus Medium Medium No Medium- High Medium Medium Recommendations Uncertain Typically, higher cradle-to- gate impacts than conventional materials None None Beneficial for waste reduction Uncertain

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APPENDIX H 353 Kishchynskyi, S., Nagaychuk, V., and Bezuglyi, A. 2016. Improving quality and durability of bitumen and asphalt concrete by modification using recycled polyethylene based polymer composition. Procedia Engineering 143:119-127. Kumar, P., and Garg, R. 2011. Rheology of waste plastic fibre-modified bitumen. International Journal of Pavement Engineering 12(5):449-459. Lastra-González, P., Calzada-Pérez, M. A., Castro-Fresno, D., Vega-Zamanillo, Á., and Indacoechea-Vega, I. 2016. Comparative analysis of the performance of asphalt concretes modified by dry way with polymeric waste.  Construction and Building Materials 112:1133-1140. Lastra-González, P., Lizasoain-Arteaga, E., Castro-Fresno, D., and Flintsch, G. 2021. Analysis of replacing virgin bitumen by plastic waste in asphalt concrete mixtures. International Journal of Pavement Engineering 1-10. MarketsandMarkets. 2022. Recycled Plastics Market Global Forecast to 2026. https://www. marketsandmarkets.com/Market-Reports/recycled-plastic-market-115486722.html McKinsey. 2020. Helping Build the Circular Economy for Plastics. https://www. mckinsey.com/industries/chemicals/our-insights/plastics-recycling-using-an- economic-feasibility-lens-to-select-the-next-moves Moghaddam, T. B., Karim, M., and Soltani, M. 2012. Polyethylene terephthalate (PET) rein- forced asphalt mixtures. 7th International Conference on Maintenance and Rehabilita- tion of Pavements and Technological Control, MAIREPAV 2012. Moghaddam, T. B., Soltani, M., Karim, M. R., Shamshirband, S., Petković, D. and Baaj, H. 2015. Estimation of the rutting performance of polyethylene terephthalate modified asphalt mixtures by adaptive neuro-fuzzy methodology.  Construction and Building Materials 96:550-555. Murphy, M., O’Mahony, M., Lycett, C., and Jamieson, I. 2001. Recycled polymers for use as bitumen modifiers. Journal of Materials in Civil Engineering 13(4):306-314. Nasr, D., and Pakshir, A. H. 2019. Rheology and storage stability of modified binders with waste polymers composites. Road Materials and Pavement Design 20(4):773-792. https:// doi.org/10.1080/14680629.2017.1417152 National Asphalt Pavement Association (NAPA). 2020. Asphalt Pavement Indus- try Survey on Recycled Materials and Warm-Mix Asphalt Usage. https://member. asphaltpavement.org/Shop/Product-Catalog/Product-Details?productid={9BC71 D4C-2307-EA11-A812-000D3A4DBC41} Nizamuddin, S., and Giustozzi, F. 2022. The role of new compatibilizers in hybrid combina- tions of waste plastics and waste vehicle tyres crumb rubber-modified bitumen. In Plastic Waste for Sustainable Asphalt Roads (pp. 165-178). Woodhead Publishing. Nizamuddin, S., Boom, Y. J., and Giustozzi, F. 2021. Sustainable polymers from recycled waste plastics and their virgin counterparts as bitumen modifiers: A comprehensive review. Polymers 13(3242). https://doi.org/10.3390/polym13193242 Nkwachukwu, O. I., Chima, C. H., Ikenna, A. O., and Albert, L. 2013. Focus on potential en- vironmental issues on plastic world towards a sustainable plastic recycling in developing countries. International Journal of Industrial Chemistry 4(34). http://www.industchem. com/content/4/1/34 Okhotnikova, E. S., Ganeeva, Y. M., Frolov, I. N., Yusupova, T. N. and Firsin, A. A. 2018. Plastic properties and structure of bitumen modified by recycled polyethylene. Petroleum Science and Technology 36(5):356-360. Onyango, F. O. 2015.  Rubber tyre and plastics waste use in asphalt concrete pave- ment (Doctoral dissertation). Vaal University of Technology, South Africa. Oreto, C., Russo, F., Veropalumbo, R., Viscione, N., Biancardo, S. A., and Dell’Acqua, G. 2021. Life cycle assessment of sustainable asphalt pavement solutions involving recycled aggregates and polymers. Materials 14(14):3867.

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APPENDIX H 357 ANNEX H-1 TABLE H-5 Amounts and Types of EoL Plastics Used in Infrastructure Reference Types of EoL Plastic Used Type of Infrastructure Amount of Waste Plastic Content Abdel Bary et al. (2020) PET Mixture 4% and 8% by weight of binder Abdel-Goad (2006) Polyvinylchloride (PVC) Binder 0-11% by weight of binder Abdullah et al. (2017) Polyethylene terephthalate (PET) Asphalt mixture for roads ~6% of the bitumen content Abu Abdo and Khater (2018) PET Binder 0.2-0.5% by weight of binder Ahmadinia et al. (2012) PET Mixture 0-10% by weight of binder Ahmedzade et al. (2014) LDPE Binder 1-9% by weight of binder Al-Hadidy and Yi- qiu (2009) LDPE Mixture 2-8% by weight of binder Al-Jumaili (2018) PET Mixture 3-12% by weight of aggregate Angelone et al. (2022) Polyethylene (PE), Polypropylene (PP) Mixture 2-6% by weight of the mixture Aschuri and Woodward (2010) HDPE Mixture 0.75-5% by weight of binder Ashoor et al. (2019) PET Binder 0-15% per weight of binder Baker et al. (2016) Polystyrene (PS) Mixture 0-15% by volume of binder Behl et al. (2012) PVC Asphalt mixture for roads 5% of the bitumen content Bilal et al. (2013) HDPE Mixture 8% per weight of binder Brasileiro et al. (2019) Ground tire rubber (GTR) Ethyl vinyl acetate (EVA) PVC PP PE Asphalt mixture for roads 1.75% to 25.0% by weight of bitumen 1% to 8% by weight of binder 1% to 20% by weight of binder 3% and 5% by weight of binder 1% and 10% by weight of binder continued

358 RECYCLED PLASTICS IN INFRASTRUCTURE Reference Types of EoL Plastic Used Type of Infrastructure Amount of Waste Plastic Content Casey et al. (2008) Various, HDPE, PE, PVC, LDPE, etc. Binder 4% by binder weight Costa et al. (2015) HDPE Mixture 5% of 6% of combined Costa et al. (2019) EVA, high-density polyethylene (HDPE) Asphalt mixture for roads 5% of the bitumen content Dalhat et al. (2019) Mixed Mixture 5% aggregate replacement Devasahayam et al. (2019) EoL plastics (not specified) Usage for aggregate 3,130 kt El-Naga and Ragab (2019) PET Mixture 0-12% per aggregate weight Fang et al. (2008) PE + Rubber Binder 0-8% per weight of both Fang et al. (2014) PE Mixture 0-10% per weight of binder Farahani et al. (2018) LDPE Binder 3-7% per weight of binder Fuentes-Audén et al. (2008) PE Binder Up to 50% per weight of binder García-Travé et al. (2016) LDPE Binder 0-7% per weight of binder Giarrusso (2018) A blend of rubber collected from ELTs (end-of-life tires) and plastic from urban waste Railway sleepers For every kilometer of rail, 1,670 of Greenrail sleepers use up to 35 tonnes of ELTs and plastic from urban waste Goh et al. (2022) e-plastic Concrete 15-20% of the binder mixture Grenfell (2020) All kind of plastics Bitumen and asphalt for road pavement ~48,000 tons Hassani et al. (2005) PET Mixture Up to 60% aggregate replacement Hu et al. (2015) PE Binder 0-8% per weight of binder Jan et al. (2017) PET Asphalt mixture for roads 15% of the bitumen content Kamada and Yamada (2002) PE, PET Mixture Replaced certain aggregate fractions TABLE H-5 Continued

APPENDIX H 359 Reference Types of EoL Plastic Used Type of Infrastructure Amount of Waste Plastic Content Khan and Sharma (2011) Nitrile rubber and PE combined Mixture 8% per weight of binder Khan et al. (2016) HDPE, LDPE, PET Binder 0-10% per weight of binder Kishchynskyi et al. (2016) PE Binder 3-4% by the weight of binder Kumar and Garg (2011) PE Mixture 0.1-0.9% per weight of binder Lastra-González et al. (2016) PE, PP, ELT Mixture 1% aggregate replacement per volume Lastra-González et al. (2021) Cable plastic and film fraction from household packaging waste Asphalt mixture Feasibility of replacing 25% of mixture with waste plastics Moghaddam et al. (2012) PET Mixture 0.2-1% per aggregate weight Moghaddam et al. (2012) PET Mixture 0.1-1% per aggregate weight Moghaddam et al. (2015) PET Mixture 0.2-1% per aggregate weight Moghaddam et al. (2015) PET Mixture 0.5-1% per aggregate weight Murphy et al. (2001) PE, PP, PU, GTR Binder 0-6 % per weight of binder Nasr and Pakshir (2019) PET & Crumb rubber (CR) (CR/ PET 60/40 Asphalt mixture for roads 15% of the bitumen content Nizamuddin et al. (2021) PE Asphalt mixture 4% by weight of bitumen Okhotnikova et al. (2018) PE Binder 7% per weight of binder Onyango et al. (2015) LDPE Mixture 0-10% per weight of binder Panda and Mazumdar (2002) LDPE Mixture 0-10% per weight of binder Parson (2021) PE, PET Asphalt mixture for roads Roughly 1.1 million tons—by 2030 TABLE H-5 Continued continued

360 RECYCLED PLASTICS IN INFRASTRUCTURE Reference Types of EoL Plastic Used Type of Infrastructure Amount of Waste Plastic Content Punith and Veeraragavan (2007) LDPE Asphalt mixture for roads 0-10% per weight of binder Punith et al. (2011) LDPE Binder 0-10% per weight of binder Rahi et al. (2019) Not specified Binder 0-8% per weight of binder Rahman et al. (2013) PE, PVC Mixture 2.5-20% per weight of binder Reddy and Venkatasubbaiah (2017) HDPE, CRM (crumb rubber modifier) Mixture 3-6% per binder weight Sasidharan et al. (2019) PE, polypropylene (PP), polystyrene (PS) Asphalt mixture for roads 12% of the bitumen content Shankar et al. (2013) Polyvinyl chloride (PVC) Asphalt mixture for roads 5% of the bitumen content Singh et al. (2013) LDPE Binder 0-10% per weight of binder Smith (2018) PE Asphalt mixture for roads 3,000 km of road using 15,000 tonnes of waste Sojobi et al. (2016) PET Mixture 1-5% per weight of aggregate Usman et al. (2016) PET Mixture 0.3-1% per weight of the mixture Vasudevan et al. (2012) PE, PP, PS Mixture 5-10% per binder weight Widyatmoko et al. (2006) Not specified Mixture 20% aggregate replacement Yan et al. (2015) LDPE Binder 2-5% per weight of binder Yu et al. (2014) PP Mixture 20% modifiers (rubber and PP 40:1), so 0.5% PP TABLE H-5 Continued

APPENDIX H 361 ANNEX H-2 TABLE H-6 Availability of Literature Level of Availability Number of References Low 0-7 Medium 7-20 High >20 Confidence in Conclusion The scale in Figure H-4 depicts the evidence and agreement statements and their relationship to confidence. Confidence increases toward the top-right corner as suggested by the increasing strength of shading. Generally, evi- dence is most robust when there are multiple, consistent independent lines of high-quality evidence (IPCC 2010). FIGURE H-4 Evidence and agreement statements and their relationship to confidence.

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Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities Get This Book
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In the U.S., most plastics waste is disposed in landfills, but a significant amount also ends up as litter on land, rivers, and oceans. Today, less than 10 percent of plastics waste is recycled in the U.S. annually. The use of recycled plastics in infrastructure applications has potential to help expand the market and demand for plastics recycling.

These are among the findings in TRB Special Report 347: Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities from the Transportation Research Board of the National Academy of Sciences, Engineering, and Medicine.

The report emphasizes that pursuing the recycling of plastics in infrastructure depends on goals, policy, and economics. To that end, life cycle economic and environmental assessments should be conducted to inform policies on plastics waste reuse.

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