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Suggested Citation:"Summary." 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:"Summary." 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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Page 3
Suggested Citation:"Summary." 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:"Summary." 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:"Summary." 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:"Summary." 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:"Summary." 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:"Summary." 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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1 Summary The use of plastics is extensive in modern society. As synthetic materials de- signed with specific end applications in mind, plastics offer unique qualities that make them materials of choice for many products. These advantages, however, also have contributed to the growing use of plastics for short- term, single-use applications and, as a consequence, the rapid growth of plastics waste. In the United States, most plastics waste is disposed of in landfills, but a significant amount also ends up as litter on land, rivers, and oceans. Today, less than 10 percent of plastics waste in the United States is recycled annually. This amount is low when compared to the potential demand for it. Therefore, it is important to consider that the use of recycled plastics in infrastructure could divert resources from other important uses. The question of diverting recycled plastics from other high-value applica- tions prompts a series of recurring questions about assessing the most valu- able uses of recycled plastics for the effective use of this resource. The U.S. Congress directed that a study be conducted to review the current use of recycled plastics in asphalt pavements and other infrastruc- ture applications and to evaluate the barriers and opportunities for using more recycled plastics in infrastructure. In response to the mandate, the U.S. Department of Transportation (USDOT) and the U.S. Environmental Protection Agency (USEPA) asked the National Academies of Sciences, En- gineering, and Medicine to examine domestic and international examples of transportation and nontransportation infrastructure projects that have used recycled plastic materials. Based on the examination and a review of other relevant research, the National Academies was asked to identify opportuni- ties for repurposing plastics waste in infrastructure and the characteristics

2 RECYCLED PLASTICS IN INFRASTRUCTURE and qualities of the plastics waste streams needed to enable cost-effective and safe applications that provide acceptable service and environmental performance. In addition, the sponsors requested that the study take a lon- ger-term view and consider how plastics recycling processes and upstream plastics manufacturing can be made more compatible with the recycling of plastics waste for use in infrastructure. Based on the specified scope, the report includes a review of the state of research and state of practice in the use of recycled plastics in trans- portation and nontransportation infrastructure. The review identifies the characteristics and qualities of the recycled plastics needed to enable cost- effective and safe applications. To have value for reuse in infrastructure or any other application, a recycled plastic must exhibit the desired properties consistently, be available in sufficient supply, be cost-competitive with the related conventional material, not pose a greater risk to the environment, have no health and safety issues, and be socially acceptable and permitted under the law. Furthermore, in infrastructure applications, acceptable ser- vice and environmental performance of the final product fabricated with recycled plastics must be guaranteed, when considered on a life-cycle basis. The study’s findings and conclusions, presented below, point to the opportunity to expand reuse of plastics in infrastructure applications, but, because of the lack of data and essential life-cycle analyses, it is not clear that the pathway of using recycled plastics in new infrastructure products offers the greatest benefit to society. Whether the reuse of plastics waste in infrastructure is an optimal choice, compared to other plastics reuse and recycling opportunities, is dependent on many factors, including what en- vironmental and societal problem is trying to be solved, such as reduction of plastics waste disposal in landfills, reduction of plastic debris in rivers and the ocean, or reduction of greenhouse gas emissions. Approaches for achieving these policy goals can yield different and sometimes conflicting implications that life-cycle analysis can help evaluate. Specification of the problem to be solved is important for the development of policy for plastics waste management. Given the relevance of life-cycle environmental and economic per- spectives, the report also reviews how plastics recycling processes and policies and upstream plastics manufacturing influence and could improve the supply of recycled plastics compatible with their use in infrastructure. Paradoxically, there is significant demand, including from manufacturers of infrastructure products, for certain types of recycled plastics that is not being met with the current waste management and recycling system. There is ample opportunity for higher levels of collection, reprocessing, and re- use of plastics at the end of their initial use phase. However, the particular public- and private-sector incentives to pursue depend on goals, policy, and economics.

SUMMARY 3 CURRENT UNDERSTANDING OF THE POTENTIAL FOR RECYCLED PLASTICS IN INFRASTRUCTURE Opportunities for using recycled plastics in infrastructure have been ex- plored and evaluated for decades but with limited success in furthering deployment in the United States. In some cases, such as using recycled plastics as concrete additives and aggregates, laboratory evaluations and small-scale piloting have revealed potential characteristics that could be problematic. A number of applications, including use in asphalt pavement mixes, railroad ties, and marine piles, have attracted commercial interest to varying degrees. However, only one product, drainage pipe (where recycled plastic feedstocks are being substituted for virgin plastic feedstocks), has generated significant demand from infrastructure owners. In other cases, such as asphalt pavement and railroad ties, acceptance by infrastructure owners has been inhibited by factors that include high material and instal- lation costs, uncertainties about long-term performance and environmental impacts, and general lack of familiarity with the product. The factors that are inhibiting commercial interest and demand by in- frastructure owners for products manufactured with recycled plastics differ by application. For example, while in other countries, such as India, the use of recycled plastics in asphalt has been implemented extensively, the deploy- ment of new materials in U.S. infrastructure follows a very different path due to specification and standards setting prior to adoption. For recycled plastics use in asphalt pavement, key factors are uncertainties about the technical requirements for formulation, dosage, and methods of addition into the asphalt pavement mix; effects on long-term material and structural perfor- mance; pavement recyclability at end of service life; and potential for release of microplastics from the pavement as it wears. Further research and testing to increase understanding of these factors will be critically important to the prospects for use of recycled plastics as a feedstock for asphalt pavement that is commercially viable and potentially helpful in reducing the amount of plastics waste disposed of in landfills or leaked to the environment. MAKING THE BEST USE OF LIMITED SUPPLIES OF RECYCLED PLASTICS Expansion of infrastructure applications of recycled plastics will depend on plastics supplies having requisite physical and chemical properties with minimal contamination and being available in sufficient quantities and with sufficient reliability. Four types of plastics, polyethylene terephthalate, high- density polyethylene, low-density polyethylene, and polypropylene, have properties that make them conducive to use in infrastructure, such as suit- able melting point and service temperature ranges, chemical resistance, and

4 RECYCLED PLASTICS IN INFRASTRUCTURE strength. While these plastics presently are the most collected and recycled from waste streams, there are many competing, noninfrastructure uses for them, such as bottles, carpet, and clothing, and the mass flows into varied uses of recycled plastic are not well known. The quality of recycled plastic has a significant influence on demand from different sectors. Moreover, access to supplies of recycled plastics that have consistent quality can be problematic due to the post-consumer collection process that is not stan- dardized and often single stream (i.e., with all types of recyclables mixed in the collection containers), leading to contamination that can require additional processing at extra cost. Supplies are further hindered by very limited market-driven processes that encourage plastics waste collection and processing in the United States. Given the limited supplies of recycled plastics having the requisite prop- erties and quality for infrastructure applications, it will be important, from a societal standpoint, to understand the full economic and environmental benefits and costs of candidate applications to make the best use of these supplies. Ideally, this understanding will be informed by assessments made on a life-cycle basis that take into account the stream of benefits and costs associated with the complete product life, including manufacturing, instal- lation, maintenance, service life, and end-of-life management. EXPANDING THE SUPPLY OF HIGH-QUALITY RECYCLED PLASTICS Increasing the supply of high-quality recycled plastics that can be used in infrastructure and other applications will require supportive state and lo- cal policies and practices affecting the collection of plastics waste streams, their processing into recycled plastics, and incentives for their reuse. Ex- amples of supportive policies are state laws and regulations that require municipalities and counties to institute recycling programs and that specify minimum recycled content for certain plastic products in packaging. Ex- amples of policies and practices that are less supportive and potentially detrimental to increasing the supply of high-quality recycled plastics are local programs that favor single-stream recycling that is convenient to customers but also leads to contamination of plastics waste due to lack of source separation. Some cities are moving away from single-stream recycling in response to contamination of separated materials (e.g., mixed paper and glass). Another option for increasing the supply of high-quality recycled plas- tics is through the creation of new plastic products that are recyclable by design, for example, by employing novel polymer formulations that are more amenable to recycling and plastics product designs that facilitate sepa- ration and sorting in waste streams used for recycling. Promising research

SUMMARY 5 to advance such capabilities is being sponsored and conducted by multiple federal agencies including the U.S. Department of Energy (USDOE), na- tional laboratories, and the National Science Foundation (NSF). POTENTIAL CONTRIBUTION OF INFRASTRUCTURE APPLICATIONS TO REDUCTIONS IN PLASTICS WASTE IN LANDFILLS AND LITTER The potential for infrastructure applications of recycled plastics to divert plastics waste from landfills and from leakage to the environment in the United States cannot be determined with confidence due to the information gaps, including need for life-cycle analysis, that remain for some candidate applications. However, even highly optimistic scenarios of successful in- frastructure applications suggest that the contribution would be modest. If one assumes, for instance, that recycled polyethylene plastics will be used in 12 percent of the asphalt pavement produced each year in accor- dance with typical dry process dosages, the diversion would amount to 2.4 percent of the U.S. polyethylene waste. Critical to the emergence of such a scenario, and indeed any scenario in which infrastructure applications use substantial amounts of recycled plastics, is the incentivizing effect that resulting increases in demand for high-quality recycled plastics would have in promoting improvements to recycling processes and rates. RECOMMENDATIONS To reduce plastics waste litter and disposal in landfills, and to capture en- ergy and resources embodied in plastic materials, it is in society’s economic and environmental interest to expand and standardize the collection of plastics waste, increase recycling of plastics for reuse, and advance new applications for their use. In light of this societal interest, and because the collection, processing, and reuse of plastics waste in the United States is affected significantly by government policies and regulations, the public sector—at the federal, state, and local levels—will need to play a promi- nent role in furthering these outcomes. Both federal sponsors of this study, USDOT and USEPA, can help promote and sustain a broad-based, coordi- nated government response through policies and investments that support research and development, pilot and field testing, and standards setting. As the federal government’s lead environmental agency with the primary responsibility for developing and planning the implementation of the 2021 National Recycling Strategy, USEPA is best positioned to provide the over- all strategic leadership, coordination, and support for decision making through information gathering, research, and analysis. USDOT, through its research and funding efforts and other support of state transportation

6 RECYCLED PLASTICS IN INFRASTRUCTURE projects, is well positioned to advance research, field testing, and standards development for use of recycled plastics for infrastructure applications in the transportation domain across multiple modes. Recommendation 1 To promote life-cycle-based economic and environmental assessments of existing and potential new uses of recycled plastics waste, including in infrastructure, the U.S. Environmental Protection Agency should support the research and data collection that will be required to understand and evaluate each use’s potential environmental, human health, economic, and performance implications. Recommendation 2 To support assessments of how existing and new applications of recovered plastics will affect the total demand for plastics waste in relation to sup- plies, the U.S. Environmental Protection Agency should expand means for tracking and modeling the supply of recycled plastics and the demand that is generated by different applications. These means should make dis- tinctions about the demand for and supply of recycled plastics by quality and polymer type and account for geographic imbalances in supply and demand. The tracking capability should enable the ongoing documenta- tion and updates of changes in both supply and demand for the targeted polymer types and their quality grades relative to predictions and forecasts. The modeling capability should allow for predictions of how plastics waste generation affects the supply of recycled plastics having different attributes suitable for productive and socially beneficial applications. Recommendation 3 To provide specific plastics-waste-focused guidance, tools, and other sup- port for communities and private-sector organizations, the U.S. Environ- mental Protection Agency should build out the general concepts and goals of the 2021 National Recycling Strategy for improved plastics waste man- agement and reuse. There are significant challenges and needs for all five of the major objectives of the National Recycling Strategy: (a) improve mar- kets for recycled commodities, (b) increase collection and improve materi- als management infrastructure, (c) reduce contamination in the materials recycling stream, (d) enhance policies and programs to support circularity, and (e) standardize measurement and increase data collection.

SUMMARY 7 Recommendation 4 To develop best practices specifically focused on next-generation plastics that are designed for recycling and reuse, the U.S. Environmental Protection Agency should build on the tools and guidance offered in its Green Chemis- try program. The tools and guidance should assist plastics manufacturers in using plastics that will satisfy the performance and quality requirements for the products in which they are used, while also minimizing adverse effects when considered on a life-cycle basis. Recommendation 5 To explore interest in, and opportunities to bring about, the development of quality criteria and standards for recycled plastics, the U.S. Environmental Protection Agency (USEPA) should take steps to encourage and facilitate more collaboration among plastics manufacturers, suppliers, recyclers, in- dustrial, and infrastructure users. Having pledged an interest in working together and with USEPA to improve the nation’s recycling system, the 380 signatories to the America Recycles Pledge may be early candidates for the creation of a community of practice that collaborates on the development and introduction of such quality standards as well as processes for verifying and certifying compliance. Recommendation 6 To foster a policy and regulatory environment at the federal, state, and lo- cal levels that aligns with the goal of increasing the supply of high-quality recycled plastics that can be used in infrastructure and other applications, the U.S. Environmental Protection Agency should work with members of the community of practice to identify specific policies and regulations that have been shown, or hold promise, to support and incentivize plastics recy- cling in an efficient and equitable manner, including (a) the use of processes for managing plastics waste, (b) the establishment of quality standards and certification processes for materials with recycled plastic content, and (c) the development and use of next-generation plastics that are more amenable to recycling. Recommendation 7 To leverage federal government capabilities, the U.S. Environmental Pro- tection Agency should lead in strengthening interagency coordination of federal agencies, including the U.S. Department of Transportation, U.S.

8 RECYCLED PLASTICS IN INFRASTRUCTURE Department of Energy, National Science Foundation, National Institute of Standards and Technology, and the U.S. Army Corps of Engineers, that have expertise, interest, and research capabilities related to plastics waste recycling and use. An interagency working group should consider and advise on how each agency can apply its research and expertise more ef- fectively for purposes such as plastics life-cycle cost analysis, the design of next-generation plastics, and furthering applications for recycled plastics. Recommendation 8 To enable more conclusive assessments of the practicality, potential side ef- fects, and life-cycle cost and performance implications of adding recovered plastics from waste to asphalt pavement formulations, the U.S. Department of Transportation and the Federal Highway Administration should build on existing efforts that are under way to support a multiyear field testing program to assess the environmental and health impacts, overall service life, and effects of plastics additives on the use and recyclability of the asphalt pavements. Recommendation 9 To identify the research and field testing that would be needed for the poten- tial future development of standards, specifications, and design guidelines for use of recycled plastics in asphalt pavements and other infrastructure applications, the U.S. Department of Transportation should work with the states, in collaboration with the American Association of State High- way and Transportation Officials, local transportation agencies, and other standards-setting organizations. Recommendation 10 With the long-term goal of developing applications of recycled plastics in infrastructure that are viable and have economic, societal, and envi- ronmental benefits, the U.S. Department of Transportation should, with involvement of the modal agencies, inventory all current and prospective transportation applications of recycled plastics, assess their likelihood (in conjunction with the U.S. Environmental Protection Agency and the rec- ommended interagency working group) of having a significant impact on plastics waste reduction, and try to understand the factors that may be slowing or impeding their development and use and how these factors could be addressed to increase marketplace demand in infrastructure industries for recycled plastics where appropriate.

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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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