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Suggested Citation:"9 Major Findings and Recommendations." 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:"9 Major Findings and Recommendations." 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:"9 Major Findings and Recommendations." 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:"9 Major Findings and Recommendations." 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:"9 Major Findings and Recommendations." 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:"9 Major Findings and Recommendations." 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:"9 Major Findings and Recommendations." 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:"9 Major Findings and Recommendations." 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 200

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193 9 Major Findings and Recommendations This study of the current and potential use of plastic waste in infrastructure or other applications has yielded a number of major findings and conclu- sions, with interlinkages and themes among them, and has led the commit- tee to offer recommendations related to these findings and in response to the statement of task. One theme among the findings, and implied in the statement of task, is that plastics at end of use comprise a resource that is being underutilized. The current management of plastics at end of use in the United States results in much (greater than 90 percent) of this plastic being disposed of in landfills, and a portion escapes management and re- sults in pollution of land, water, and air with plastic materials. Paradoxi- cally, there is significant demand for certain types of recycled plastics that is not being met with the current management system. Manufacturers of plastic products being used in infrastructure are the source of some of this demand. Thus, there is ample opportunity for higher levels of collection, reprocessing, and reuse of plastics at the end of their initial use phase, but the priority to pursue reuse depends on goals, policy, and economics. There is opportunity to expand reuse of plastics in infrastructure applications, for example, but it is not clear that this reuse pathway offers the greatest benefit to society. Recycling plastic into infrastructure may well not be a major contribution to diverting plastic wastes from landfills or reducing un- controlled plastic disposal and associated pollution, but it could contribute. Determining which plastic reuse pathways—or reduction of plastics use in the first instance—offer the greatest benefit to society requires clarifica- tion of goals as presented in policies at the local, state, and federal levels.

194 RECYCLED PLASTICS IN INFRASTRUCTURE Life-cycle economic and environmental assessments are needed to inform these policies. MAJOR FINDINGS AND CONCLUSIONS Current Understanding of the Potential for Recycled Plastics in Infrastructure 1. Opportunities for using recycled plastic waste in infrastructure have been explored and evaluated for decades but with limited suc- cess 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 po- tential engineering 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, 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 installation costs, uncertainties about long-term performance and environmental impacts, and general lack of famil- iarity with the product. 2. The factors that are inhibiting commercial interest and demand by infrastructure owners differ by application. 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 ma- terial and structural performance; pavement recyclability at end of service life; and 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 of re- cycled plastics being a feedstock for asphalt pavement that is com- mercially viable and potentially helpful in reducing the amount of plastics waste disposed in landfills or leaked to the environment. Making the Best Use of Limited Supplies of Recycled Plastics 3. An expansion of infrastructure applications of recycled plastics will depend on a supply of plastics with the requisite physical and chemi- cal properties with minimal contamination. This supply must be

MAJOR FINDINGS AND RECOMMENDATIONS 195 available in sufficient quantities and with sufficient reliability. Four types of plastics, polyethylene terephthalate, high-density polyethyl- ene, low-density polyethylene, and polypropylene, have properties that make them conducive to use in infrastructure, such as suitable melting point and service temperature ranges, chemical resistance, and strength. While these plastics are the most collected and recycled from waste streams, there are many competing, noninfrastructure uses for them, such as bottles, carpet, and clothing. Moreover, ac- cess to supplies of recycled plastics that have consistent quality can be problematic because of a post-consumer collection process that is not standardized and is often single stream (i.e., with all types of recyclables mixed in the collection containers), leading to contamina- tion that can require additional processing at extra cost. Supplies are further hindered by the absence of market-driven processes that en- courage plastics waste collection and processing in the United States, where less than 10 percent of the plastics waste stream is recycled. 4. Given the limited supplies of recycled plastics with requisite prop- erties and quality for infrastructure applications, it will be impor- tant, from a societal standpoint, to understand the full economic and environmental benefits and costs of candidate applications to make 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, installation, main- tenance, service life, and end-of-life management. Expanding the Supply of High-Quality Recycled Plastics 5. Increases in the supply of high-quality recycled plastics that can be used in infrastructure and other applications will require sup- portive state and local policies and practices affecting the collection of plastics waste streams, their processing into recycled plastics, and incentives for their reuse. Examples 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. Examples of policies and practices that are less supportive and potentially det- rimental to increasing the supply of high-quality recycled plastics are local programs that favor single-stream recycling that leads to waste stream contamination. 6. Another option to increase the supply of high-quality recycled plastics is through the creation of new plastic products that are

196 RECYCLED PLASTICS IN INFRASTRUCTURE recyclable by design, for example, by employing novel polymer formulations that are more amenable to recycling and designing plastic products that facilitate separation and sorting in waste streams used for recycling. Promising research to advance such capabilities is being sponsored and conducted by multiple federal agencies, including the U.S. Department of Energy, national labo- ratories, and the National Science Foundation. Potential Contribution of Infrastructure Applications to Reductions in Plastics Waste in Landfills and Litter 7. The potential for infrastructure applications of recycled plastics to divert plastic waste from landfills and leakage in the United States cannot be determined with confidence due to the information gaps that remain for some candidate applications. However, even highly optimistic scenarios of successful infrastructure applications sug- gest that the contribution could be modest. If one assumes, for instance, that recycled plastics will be used in 12 percent of the asphalt pavement produced each year in accordance 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 applica- tions use substantial plastic waste, 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 collection of plastic 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 plastic waste in the United States is affected signifi- cantly by government policies and regulations, the public sector—at the fed- eral, state, and local levels—will need to play a prominent role in furthering these outcomes. Both federal sponsors of this study, the U.S. Department of Transportation (USDOT) and the U.S. Environmental Protection Agency (USEPA), can help promote and sustain a broad-based, coordinated govern- ment response through policies and investments that support research and development, pilot and field testing, and standards setting. As the federal

MAJOR FINDINGS AND RECOMMENDATIONS 197 government’s lead environmental agency and having primary responsibil- ity for developing and planning the implementation of the 2021 National Recycling Strategy (USEPA 2022a), USEPA is best positioned to provide the overall 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 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. Recommendations for USEPA Recommendation 1 To promote life-cycle-based economic and environmental assessments of existing and potential new uses of recycled plastic 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 plastic 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 support for communities and private-sector organizations, the U.S. Environmental Protection Agency should build out the general concepts and goals of the 2021 National Recycling Strategy for improved plastic waste management

198 RECYCLED PLASTICS IN INFRASTRUCTURE and reuse. There are significant challenges and needs for all five of the ma- jor objectives of the National Recycling Strategy: (a) improve markets for recycled commodities, (b) increase collection and improve materials man- agement 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. Recommendation 4 To develop best practices specifically focused on next-generation plastics that are designed for recycling and reuse, the U.S. Environmental Protec- tion Agency should build on the tools and guidance offered in its Green Chemistry program (USEPA 2022b). 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 (USEPA 2022c) 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 plastic 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.

MAJOR FINDINGS AND RECOMMENDATIONS 199 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. 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. Recommendations for USDOT 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

200 RECYCLED PLASTICS IN INFRASTRUCTURE 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. REFERENCES U.S. Environmental Protection Agency (USEPA). 2022a. National Recycling Strategy. https:// www.epa.gov/recyclingstrategy –––. 2022b. Green Chemistry. https://www.epa.gov/greenchemistry –––. 2022c. America Recycles Pledge. https://www.epa.gov/recyclingstrategy/forms/america- recycles-pledge

Next: Appendix A: Study Committee Biographical Information »
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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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