Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Pawan Patil • Natalya Stankevich • Nina Tsydenova • Zoie Diana Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Pawan Patil Natalya Stankevich Nina Tsydenova Zoie Diana South Asia’s mountain economies of Afghanistan, Bhutan, and Nepal join the region’s ocean economies of Bangladesh, India, Maldives, Pakistan, and Sri Lanka to curb marine plastics pollution. This report is part of a larger series of stocktaking and analytical products on plastic pollution in South Asia. This work is un- dertaken as part of the World Bank’s work program on South Asia Marine Plastics Pollution, which aims to promote circular plastic economy solutions, advance related country-level policy and investment dialogues, and raise awareness of the del- eterious impacts of marine plastics pollution on people’s lives and livelihoods. It supports the Bank’s commitment to work with countries of South Asia to pursue and scale-up policies and programs that help them move toward a circular plastic economy and, in partnership with civil society and the private sector, harnesses the power of innovation to bring viable and sustainable solutions for plastic waste reduction and management across the region. Plastic pollution is a widespread and pressing environmental crisis in South Asia. Although we need to turn off the tap on plastic pollution, we must find ways to deal with the existing mountains of plastic waste, much of which is not recyclable. Meanwhile, some roads may be a potential application of this plastic waste as discussed in this new report, but much more research needs to be conducted moving forward to ensure any negative externalities are properly understood and addressed. Christophe Crepin, Practice Manager, South Asia Environment, Natural Resources and the Blue Economy Roads, and particularly rural roads, are essential for connectivity, economic development, and poverty reduction across South Asia. One of our objectives is to support our clients in building roads and other infrastructure more sustainably. This report is another important step on the pathway toward understanding the sustainable development of connectivity with roads. Shomik Raj Mehndiratta, Practice Manager, South Asia Transport Our new report, Plastic Waste in Road Construction: A Path Worth Paving? provides a first close examination of the technology and process that enables the use of difficult to recycle plastic waste material in road construction. With thousands of kilometers of so called “plastic roads” slated for construction across the world, including South Asia, it’s a good time to put a spotlight on the technology and kick-start a discussion on its pros and cons. John Roome, Regional Director for Sustainable Development, South Asia As the global community coalesces to draft an international, legally-binding treaty to reduce plastic pollution by 2024, we need to think about what to do with the plastic waste we have already generated. The use of plastic waste in roads may be one possible option to apply this waste in a manner that may also reduce carbon emissions. Valerie Hickey, Global Director, Environment, Natural Resources and the Blue Economy The use of plastic waste in roads is an emerging technology spreading worldwide, through either pilot projects or roads that are in use. This first of a kind World Bank report, Plastic Waste in Road Construction: A Path Worth Paving? puts a spotlight on the possibility of incorporating plastic waste in road construction. Nicola Peltier, Global Director, Transport Plastic pollution is a significant issue in South Asia, threatening human and environmental health. I’m happy to hear of this emerging method to construct roads using plastic waste, which may otherwise end up in open dumps or the environment. Of course, there is no silver bullet, and we need to ensure that we do no harm if applying such technologies. Guangzhe Chen, Vice President, Infrastructure Disclaimer © 2023 International Bank for Reconstruction and Development / The World Bank 1818 H Street NW Washington DC 20433 Telephone: 202-473-1000 Internet: www.worldbank.org This work is a product of the staff of The World Bank with external contributions. The findings, interpretations, and conclu- sions expressed in this work do not necessarily reflect the views of The World Bank, its Board of Executive Directors, or the governments they represent. 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Because The World Bank encourages dissemination of its knowledge, this work may be reproduced, in whole or in part, for noncommercial purposes as long as full attribution to this work is given. Any queries on rights and licenses, including subsidiary rights, should be addressed to World Bank Publications, The World Bank Group, 1818 H Street NW, Washington, DC 20433, USA; fax: 202-522-2625; e-mail: pubrights@worldbank.org. Cover photo: © Atk Work / Priya Ranjan /Shutterstock.com Cover design: Inti Alonso Suggested Citation: Plastic Waste in Road Construction: A Path Worth Paving? World Bank (2023). Table of Contents Glossary of Terms  12 Acronyms and abbreviations 15 Acknowledgements 16 Abstract 16 Executive summary 17 1 3 4 Introduction 2 22 Road construction overview: the use of virgin Use of plastic waste in polymer road construction 26 28 Methods 24 Conventional road construction 26 Plastic waste 28 5 6 Key findings and knowledge gaps 38 References52 Annexes61 Annex A.  Annex B.  Annex C.  61 66 70 Annex D.  70 Environmental sustainability 38 Annex E.  71 Way Forward Annex F.  77 Regulatory and policy landscape: Annex G. 81 examples from India 42 48 Annex H. 83 Engineering performance 42 Short-term research 49 Annex I.  83 Annex J.  85 Economic analysis 44 Long-term research 50 Annex K. 88 List of figures and tables Table 1. Table 4. Technology readiness of plastic roads and level of Results of sample engineering performance studies. 43 uncertainty in existing knowledge gaps. 19 Table 5. Figure 1. Plastic waste costs for plastic road construction. 45 Plastic RICs and amount consumed in kilotons in South Asia in 2018. 29 Table 6. Cost of non-plastic materials and related processes for Figure 2. plastic road construction. 45 Process of building a conventional road or plastic road (wet and dry process). 31 Table 7. Search strings used to identify those who are building Figure 3. plastic roads and geographic locations constructed or Timeline of key events. Sources include patents and planned plastic roads 61 Denning and Carswell (1983); Mercer (1997); Willis, Yin, and Moraes (2020). 32 Table 8. Keywords queried in brief business descriptions in Table 3. Standard and Poor’s (S&P) Capital IQ 63 Wet and dry process of plastic road construction. Sources include Gill and Abid (2019); Willis, Yin, and Moraes (2020); Table 9. and the IRC (2013) specifications. 33 Web of Science search string 65 Figure 5. Table 10. Plastic roads use status. 35 Plastic recycling categories 66 Figure 4. Table 11. Map of plastic roads. 35 Sample of plastic additives 67 Box 1. Figure 6. Sample of companies and research institutes 36 Number of patent applications in our sample filed Figure 8. annually (non-cumulative) from 1935 to 2021 68 Use of Marshall Stability Test and/or Superpave Performance Grading 87 Table 12. Percentages of bitumen substituted by plastic waste 69 Table 18. Modeling assumptions 90 Figure 7. Number of scientific articles in our sample studying Table 19. each plastic type 69 CEA Results based on economic prices of 1 km of constructed road considering the lower and upper Table 13. bound of CO2* pricing (in INR and US$, respectively) ** 92 Geographic locations of plastic roads 71 Figure 9. Table 14. Shadow prices of CO2 and volume of CO2 included Businesses using plastic waste in road construction in the CEA 93 identified in S&P Capital IQ database 76 Table 20. Table 15. Recycled Plastic Price Sensitivity Analysis 94 Summary of LCA studies reviewed 78 Table 16. Examples of standardized tests by the American Society for Testing and Materials (ASTM) and American Association of Highway and Transportation Officials (AASHTO) associated with laboratory binder characterization84 Table 17. Common laboratory tests and tests standards to assess asphalt mixture properties. 86 Glossary of Terms Aggregate gradation: The particle size emulsified (or cutback) asphalt binder. place). Cold mix asphalt can be produced distribution from the largest through It can be plant-mixed or mixed in-place. and stored for usage at a later date. finest materials. Asphalt pavement: Pavement consist- Concentration: The amount of a sub- Aggregate: A hard inert material of min- ing of a surface course of asphalt con- stance expressed as a proportion of the eral composition such as sand, gravel, crete over supporting courses such as water, air, or solid in which it resides. slag, or crushed stone of various sizes, asphalt concrete bases, crushed stone, Usually expressed as mass of sub- used in pavement applications either by slag, gravel, Portland Cement Concrete, stance per volume of liquid or as mass itself or for mixing with asphalt binder. brick, or block pavement. of substance per mass of solid. Air pollutants: Those impurities which Asphalt: Mixture of aggregate and Concrete: A material formed of aggregate cause the atmosphere to become con- fine particles held together in a bitu- bound together with Portland cement. taminated. These include carbon mon- men-based binder. Also known as as- Also known as Portland cement concrete. oxide, nitric oxides, sulfur dioxides, phaltic concrete in many countries. particulates, and hydrocarbons. Construction and Demolition (C&D) Asphalt(ic) cement: Brownish black, Waste: Material including concrete, Alternative material: a material to those solid or semisolid mix of bitumen bricks, lumber, masonry, road paving ma- traditionally used in construction, typical- from native deposits or a petroleum terials, rebar and plaster generated from ly it may be an industrial by product, a by-product used in the manufacturing both homeowners’ and contractors’ con- recyclable, a treated material, and so on. of asphaltic concrete. struction or demolition projects. Asphalt binder or asphalt cement: A Average daily traffic: Measurement of Contaminant: A chemical, microorgan- dark brown to black cementitious ma- the number of vehicles using a highway ism, or particulate component that is terial which predominantly constituted over a year divided by 365 to obtain normally absent from the environmental of bitumen which occurs in nature or is the average for a 24-hour period. compartment in which it resides, or which obtained in petroleum processing. As- is present at an elevated concentration. phalt is a constituent in varying propor- Base: The main structural layer of a tions of most crude petroleum. pavement. Crack: An approximately vertical ran- dom cleavage of the pavement caused Asphalt binder: Asphalt cement that Bitumen: A natural asphalt or substance by traffic loading, thermal stresses and/ is classified according to the Standard found in a natural state or a residue or aging of the binder. Specification for Performance Grad- by-product from petroleum refinement. ed Asphalt Binder, AASHTO Designa- Deflection: A load-induced, downward tion MP1. It can be either unmodified or Bituminous: Containing bitumen. movement of a pavement section. modified asphalt cement, as long as it complies with the specifications. Cement: A powdered product made by Dispersion: The three-dimensional re- grinding clinkers of limestone, clay, and distribution of a substance dissolved Asphalt concrete: A high quality, thor- other materials, and which reacts with or suspended in a fluid that is caused oughly controlled mixture of asphalt water to form a rock-like substance used by local variations in movement of that binder and high-quality aggregate, to bond aggregates together in concrete. fluid usually resulting from inhomoge- which can be compacted into a uni- neity in the pathway. formly dense mass. Cold mix asphalt: A mixture of emulsi- fied or cutback asphalt and aggregate Dry process: Plastic waste is shredded Asphalt emulsion mix (cold): A mix- produced in a central plant (plant-mixed) and mixed with preheated aggregates ture of unheated mineral aggregate and or mixed at the road site (mixed-in- prior to adding bitumen at 160°C. Durability: The property of an asphalt Modified asphalt rubber binder: Con- Plastomer: Type of modifier used to paving mixture that represents its abil- ventional asphalt cement to which prevent rutting and increase viscosity ity to resist disintegration from the en- recycled ground tire rubber and com- of modified binder. vironment and traffic. pounds have been added, that when reacted with the hot asphalt cement Poise:   A centimeter-gram-second Elastomer: Polymer that displays elastic causes a dispersion of the tire rubber unit of absolute viscosity equal to mechanical properties. particles and compounds. the viscosity of a fluid in which a value of stress one dyne per square Emulsifying agent or emulsifier: The Patching: When the pavement begins centimeter is required to maintain a chemical added to water and asphalt to deteriorate due to the influences of difference of velocity of one centime- that keeps the asphalt in stable suspen- the environment and traffic, holes, ruts ter per second between two parallel sion in water. The emulsifier determines and cracks are usually localized at ex- planes in the fluid that lie in the di- the charge of the emulsion and con- isting pavement joints. The repair of rection of flow and are separated by trols the breaking rate. this type of failure consists of sawing a distance of one centimeter. out, removing and replacing the mate- Fatigue and Cracking Resistance: The rial with new Portland cement concrete Pollutant: A substance existing at suffi- ability of asphalt pavement to resist crack or bituminous concrete. cient concentration such that its effects initiation caused by repeated flexing. are harmful to human health, other liv- Pavement: Any layer added to the nat- ing organisms, or the environment. Flexibility:  The ability of an asphalt ural ground surface, The part of a road- pavement structure to conform to set- way having a constructed surface for Polymer-modified asphalt binder: A tlement of the foundation. the facilitation of vehicular movement. conventional asphalt cement to which a styrene block copolymer or styrene bu- Hot mix asphalt:  High quality, thor- Penetration: The consistency of a bitu- tadiene rubber latex or neoprene latex oughly controlled hot mixture of as- minous material expressed as the dis- has been added to improve performance. phalt binder (cement) and well-graded, tance (in tenths of a millimeter) that a high quality aggregate, which can be standard needle penetrates a sample Post-consumer plastic waste: The sta- compacted into a uniform dense mass. vertically under specified conditions of tus after an item has been used for its loading, time and temperature. intended purpose. Postconsumer mate- Human carcinogen: Substance that pro- rial may be generated by households or motes the formation of cancer in humans. Performance grading: Asphalt binder commercial establishments. grade designation used in Superpave. Liquefaction: Process of making or be- It is based on the binder’s mechanical Post-industrial plastic waste: Materi- coming a liquid. performance at critical temperatures al that has been processed initially and and aging conditions. failed to meet specifications or otherwise Mechanical recycling: Operations that not sold as prime material and sold to an- recover plastics through mechanical Phase separation: Separation between other party for reuse or reprocessing. processes, including grinding, wash- the recycled plastic and binder in road ing, separating, drying, re-granulating construction that occurs under static Pyrolysis: Thermal degradation of and compounding. heated storage conditions which can plastic waste to produce liquid oil. affect road performance negatively. Microplastics: Plastic pieces less than Raveling: The progressive separation 5 millimeters (0.2 inches) in length that Plasticizer: Substance added to syn- of aggregate particles in a pavement occur in the environment as a conse- thetic resin to promote plasticity and from the surface downward or from the quence of plastic pollution. flexibility and to reduce brittleness. edges inward. Reactive polymer: A polymer hav- gate with a rough surface texture are Waste nitrile rubber: Synthetic rubber ing chemical groups that can be trans- the greatest contributors. The aggre- made from a copolymer of acrylonitrile formed into other chemical groups gate must not only have a rough sur- and butadiene. under the specific conditions required face texture, but also resist polishing. for a given reaction or application. Wearing Course: Top layer of an as- Solubility: A measure of the purity of phalt structure that is designed to Re c l a i m e d a s p h a l t p ave m e n t asphalt cement. The ability of the por- accommodate traffic load and resist (RAP): Excavated asphalt pavement tion of the asphalt cement that is solu- skidding and adverse weather. that has been pulverized, usually by ble to be dissolved in a specified solvent. milling, and is used like an aggregate Wet process: Recycled plastics in the in the recycling of asphalt pavements. Stability: The ability of an asphalt pav- form of powder are added to bitumen, ing mixtures to resist deformation from heated at 160–170°C, mechanically Reclaimed asphalt shingles: Discard- imposed loads. Stability depends on mixed, and then the aggregate is added. ed roofing shingles that are used like both internal friction and cohesion. an aggregate in the recycling of asphalt pavements. Superpave Mix Design: An asphalt mix- ture design system that integrates the Recycled asphalt mix: A mixture pro- selection of materials (asphalt, aggre- duced after processing existing asphalt gate) and volumetric proportioning with pavement materials. The recycled mix the project’s climate and design traffic. may be produced by hot or cold mixing at a plant, or by processing the materi- Superpave™: Short for “Superior Per- als cold and in-place. forming Asphalt Pavement” – a per- formance-based system for selecting Recycling: Separating, collecting, pro- and specifying asphalt binders and for cessing, and reprocessing, often either developing an asphalt mixture design. chemically or mechanically, of a mate- rial for use in a new material or product. Virgin polymer: Polymer resin produced from petrochemical feedstock, such as Rutting: Channeled depressions that natural gas or crude oil, which has never sometimes develop in the wheel paths been used or processed before. of an asphalt pavement. Viscosity grading: A classification sys- Shoving: A type of pavement distortion. tem of asphalt cements based on viscos- These distortions usually occur at points ity ranges at 60°C (140°F). A minimum where traffic starts and stops, on hills viscosity at 135°C (275°F) is also usual- where vehicles brake on the downgrade, ly specified. The purpose is to prescribe on sharp curves, or where vehicles hit a limiting values of consistency at these bump and bounce up and down. They two temperatures. Approximately 60°C occur in asphalt layers that lack stability. (140°F) is the maximum temperature of an asphalt pavement surface in service in Skid resistance: The ability of an as- the United States. Approximately 135°C phalt paving surface, particularly when (275°F) is the mixing and laydown tem- wet, to offer resistance to slipping or peratures for hot mix asphalt pavements. skidding. The factors for obtaining high skid resistance are generally the Viscosity: A measure of the resistance same as those for obtaining high stabil- to flow of a liquid. It is one method of ity. Proper asphalt content and aggre- measuring the consistency of asphalt. Acronyms and abbreviations AASHTO: American Association of State LAST: Laboratory Asphalt Stability Test PV: Present value Highway and Transportation Officials LCA: Life Cycle Assessment PVC: Polyvinyl chloride ABI: Abstracted Business Information LLDPE: Linear low-density polyethylene PWD: Public Works Department ABS: Acrylonitrile–Butadiene–Styrene LDPE: Low-density polyethylene RAP: Reclaimed Asphalt Pavement APP: Ammonia Polyphosphate LSGD: Local Self Government Depart- RET: Reactive elastomeric terpolymer ASTM: American Society for Testing ment, Kerala, India and Materials RIC: Resin identification codes MMT: Million metric tons Cd: Cadmium S&P: Standard and Poor MoEFCC: Ministry of Environment, Forest, CO2: Carbon dioxide and Climate Change, Government of India SAR: South Asia Region Cr: Chromium MoRd: Ministry of Rural Development, SDBC: Semi-dense bituminous concrete Government of India Cu: Copper SBS: Styrene–Ethylene–Butylene MoRTH: Ministry of Road Transport and CEA: Cost-effectiveness analysis Highways, Government of India SLRM: Solid liquid resource management CSIR: Central Road Research Institute, NCAT: National Center for Asphalt SWIS: Solid Waste Institute for Sustain- India Technology ability EEE Index: Energy, Environmental and NHAI: National Highway Authority of SIS: Styrene–Isoprene–Styrene Economic Index India SWaCH: Solid Waste Collection and EVA: Ethylene Vinyl Acetate Ni: Nickel Handling GMA: Glycidyl Methacrylate NJDOT: New Jersey Department of TxDOT: Texas Department of Transpor- Transportation tation HAP: hazardous air pollutants Pb: Lead UK: United Kingdom HDPE: High-Density Polyethylene PC: Polycarbonate UNEA: United Nations Environment IDT: Indirect Tensile Test Assembly PE: Polyethylene INR: Indian rupee US: United States PET: Polyethylene terephthalate IRC SP: Indian Roads Congress Special USHRP: United States Strategic High- Provision PP: Polypropylene way Research Program KHRI: Kerala Highway Research Institute PPA: Polyphosphoric acid Zn: Zinc KPMG: Klynveld Peat Marwick Goerdeler PS: Polystyrene Acknowledgements This report was prepared by Pawan Pa- tal Engineer, World Bank; and Kreme- University for their interviews and ex- til, Task Team Leader and Senior Econo- na Ionkova, Lead Urban Specialist; and pert review. Additionally, we would like mist, Natalya Stankevich, Co-Task Team Reenu Aneja, Senior Transport Spe- to thank Jane Day, Associate Director/ Leader and Senior Transport Specialist, cialist. Further thanks to the following Manager of Public Services at Ford Li- Nina Tsydenova, Environmental Spe- World Bank staff for their technical ex- brary in Duke University’s Fuqua School cialist, and Zoie Diana, Plastic Waste pertise and discussions, which informed of Business for her help in determining Management Consultant and Ph.D. the report: Nagaraja Rao Harshadeep, search strings. Lastly, we thank Erik Candidate in the Marine Science and Lead Environment Specialist, Indranil Kievit (Plastic Roads), Petko Krastev Conservation Division and Integrated Bose, Consultant, Balakrishna Menon (Dow), Sean Weaver (Neopave), Ekk- Toxicology and Environmental Health Parameswaran, Lead Urban Specialist, asit Lakkananithiphan (Dow), Uyen Mai Program at Duke University. We would Elif Ayhan, Senior Disaster Risk Man- (Dow), and Son Nguyen (Dow) for par- also like to acknowledge Bushra Nishat, agement Specialist, Deepak Singh, ticipating in interviews and sharing their Environmental Specialist, World Bank, Lead Disaster Risk Management Spe- feedback on the initial draft of this re- and Kate Pankowska, Economics Con- cialist, and Arnab Bandyopadhyay, Lead port. We would also like to express our sultant for their contributions. Transport Specialist. thanks to Charles Engrem (Wenger), The team is grateful to Christophe Special thanks are extended to the Dan Gaston (Wenger), and Kenneth Crepin, Practice Manager, South Asia following people for their extensive Hutman (KBH Global Enterprises, Ltd.) Environment, Natural Resources and discussions, technical expertise, and for sharing their technical expertise. Blue Economy, and Shomik Mehndiratta, invaluable contributions to the study The team would like to acknowledge Practice Manager, South Asia Transport, which have informed this report: Anand the generous financial support of the as well as to Cecile Fruman, Director for Singh, Indian Administrative Service, of Human Rights, Inclusion and Empow- Regional Integration, and John Room, Re- the Government of Kerala; Devesh Ti- erment (HRIE) Trust Fund and South gional Director for Sustainable Develop- wari and Ambika Behl, Central Road Asia Water Initiative (SAWI) Trust Fund ment, for their leadership and guidance Research Institute; Sankar V Assistant without which this study would not have provided to us in the course of this study. Director, and Thomas John, Assistant been possible. The HRIE is supported by This report benefited extensive- Director, Kerala Highway Research In- Canada, Finland, Germany, Iceland, the ly from comments and suggestions stitute. We would like to thank Ama- Netherlands, Norway, Sweden, and the provided by the several peer review- lia Cymrot-Wu, World Bank Intern and United Kingdom. SAWI received contri- ers—Dr. Sahadat Hossain, Professor, Short-Term Temporary for research as- butions from the United Kingdom’s For- University of Texas; Pratap Tvgssshrk, sistance. We also thank Dr. Cassie Cas- eign, Commonwealth and Development Senior Transport Specialist, World Bank; torena, Associate Professor at North Office, Australia’s Department of For- Tracy Hart, Global Lead, Environmen- Carolina State University and Dr. Fan eign Affairs and Trade, and Norwegian tal Risk Management (ERM) & Fragile Yin, Assistant Director of the National Agency for Development Cooperation. and Conflict States (FCS), World Bank; Center for Asphalt Technology and As- Delphine Arri, Senior Environmen- sistant Research Professor at Auburn 16 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Abstract As global plastic waste continues to independent, scientific researchers to research gaps, including the generation grow, the global community is coalesc- determine the existing knowledge gaps of hazardous air pollutants during pro- ing to reduce plastic waste. Some stake- regarding the (1) technology feasibility, duction; microplastics and nanoplastics holders are also exploring new options including engineering performance; (2) generation during use; and leaching of to use plastic waste as partial substitute environmental issues; (3) occupational additives from plastic waste during use. for raw material. The use of plastic waste health; (4) economic viability; and (5) Industry standards for the use of plastic as a bitumen modifier in road construc- industry standards surrounding plas- waste in road construction are lacking. tion, referred to here as ‘plastic roads’, is tic roads. We found that many compa- In addition, there is prevailing uncer- one option being explored. We reviewed nies are starting to implement or pilot tainty in the economic viability of the the scientific literature, news articles, this technology worldwide though key technology. As a result of these key re- and patents; conducted a cost-effec- gaps in engineering performance, such search gaps, the Ways Forward section tiveness analysis; and interviewed repre- as cracking resistance, remain. The en- presents a roadmap for short- and long- sentatives from private companies and vironmental issues reviewed also have term research priorities. Executive summary Plastic pollution is one of the most early as 1974 and have spread, espe- Asia, in comparison to pressing environmental issues global- cially throughout India since Dr. Ra- conventional roads; ly. Plastics were commercialized in the jagopalan Vasudevan reported this 1950s (Andrady and Neal 2009) and technology in the scientific literature b Summarize the environmental have grown to be ubiquitous in our ev- in 2004. In plastic roads, post-con- impacts, engineering eryday lives, becoming the most wide- sumer and/or post-industrial plastic performance, regulatory ly used man-made substance (Worm waste is used as a partial substitute considerations and et al. 2017). In a business-as-usual for aggregate or bitumen, often be- economic viability; scenario, the amount of plastic waste tween 6 and 8 percent by weight of produced will grow from 220 million bitumen. In the wet process, pow- c Recap the key challenges metric tons in 2016 to an estimated dered plastic waste is added to bitu- and knowledge gaps; and 430 million metric tons in 2040 (The men, heated, and then added to the Pew Charitable Trusts and SYSTEMIQ aggregates. This report focuses on the d Develop recommendations 2020). In South Asia, open dumping dry process in which plastic waste is to inform further research (75 percent) dominates, while recycling shredded and mixed with preheated and road infrastructure (5 percent), and landfilling1 (4 percent) aggregates prior to adding bitumen. projects in South Asia. (Kaza et al. 2018) are less frequently This report targets policy mak- used. Given the large amounts of plas- ers, the private sector, and transport In the preparation of this report, the tic waste produced globally, entrepre- practitioners who may be considering project team reviewed the scientific lit- neurs, innovators, and researchers are using plastic waste in road construc- erature, news articles, and patents; con- discovering new ways of utilizing plas- tion. The report aims to ducted a cost-effectiveness analysis; tic waste. and interviewed representatives from The use of plastic waste in road a Provide an overview on private companies and independent, construction is an emerging, more the use of plastic waste in scientific researchers studying the use recent alternative use of plastic road construction using of plastic waste in road construction. waste. Plastic roads were patented as the dry process in South The key findings, identified by the proj- 1 The type of landfilling, whether controlled or sanitary landfilling, is unspecified (Kaza et al. 2018). Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 17 ect team, are clustered within this report Further research in these areas will help (3) Occupational health: At the asphalt into five themes: (1) technology feasibil- determine the environmental sustain- plant, the risk of fire and generation of ity, including engineering performance; ability of this technology. hazardous air pollutants (HAP) can be (2) environmental issues; (3) occupa- high for plastic roads constructed using tional health; (4) economic viability; and (2a) Microplastics: The scientific field the dry process (Willis, Yin, and Moraes (5) industry standards. Recommenda- lacks key environmental studies on the 2020). Plastics must be heated to com- tions to address key knowledge gaps scale and toxicity of microplastics and bine the aggregate and this should only were identified. nanoplastics generated from plastic occur at the central asphalt plant with roads and tire wear as compared to proper, protective environmental and Key findings conventional roads and tire wear. It is occupational health guidelines, rather expected, but to our knowledge, not than in an informal setting. The heating (1a) Technology feasibility: Plas- yet documented, that plastic roads of plastics can produce HAP such as vol- tic roads are an emerging technol- will generate microplastics and nano- atile organic compounds and polycy- ogy. The dry process primarily faces plastics from road and tire wear just as clic aromatic hydrocarbons (Willis, Yin, quality control issues, such as un- conventional roads do. and Moraes 2020). Occupational health even distribution of plastic waste standards should be created and have within the asphalt mix. This results (2b) Additive leaching: Plastics leach provisions to mitigate those risks. in operational issues for the industry organic and inorganic additives. Further and constraints in mainstreaming the research is also needed to determine if (4) Economic viability: There are con- technology. Similarly, additional and these additives leach from plastic roads flicting reports regarding whether or upgraded equipment would be need- and if so, what is the amount of addi- not plastic roads are more affordable ed to incorporate plastic waste into tives leached and chemical compounds. than conventional roads. Often, plas- asphalt at the plant. It is unknown if construction techniques tic roads are reported to be more af- can mitigate this leaching. The toxicity fordable than conventional roads since (1b) Engineering performance: Over- of leached plastic additives to aquat- plastic waste often partially substitutes all, there is currently high uncertainty in ic and terrestrial animals and environ- for bitumen (between 6 and 8 per- the field regarding the performance of ments should be evaluated. cent). We conducted a cost-effective- plastic roads. Generally, the use of plas- ness analysis that indicates that the use tic waste in road construction improves (2c) Recyclability at the end of life: of waste plastic in road construction rutting performance. However, improve- Most asphalt pavement in convention- is economically justifiable. However, ments in rutting often lead to problems al roads can be recycled. It remains un- KPMG (2021) conducted a cost-ben- with road cracking. A few studies show known if plastic roads can be recycled efit analysis for the World Bank and that the use of plastic waste in road con- at the end of their lifespan. Further re- found that the use of plastic waste in struction may reduce road cracking re- search should include end of life plan- road construction increases the cost sistance. Long-term performance of ning for plastic roads and determine if of roads by US$0.14 per square meter plastic roads under a range of environ- and how these roads can be recycled. of road, as compared to conventional mental conditions, including flooding, roads. The Government of India’s Min- remains unclear. Without this certainty, (2d) Life cycle analysis: Lastly, we istry of Railways (2019) came to the it will be difficult to ensure that plastic identified studies that analyzed plas- same conclusion. Multiple engineering roads will not require more maintenance tic roads in comparison to conventional studies in the scientific literature pre- than conventional roads. roads from a life cycle perspective. How- sented short analyses regarding the ever, these studies focused on roads in costs of plastic roads compared to con- (2) Environmental issues: Key gaps re- high-income countries. Further research ventional roads. These studies primarily lated to the environmental sustainabil- that conducts a life cycle assessment found that plastic roads were cheap- ity of this technology were identified (LCA) on plastic roads in lower-income er than conventional roads. The liter- and include the following topics: micro- countries is needed. This research incor- ature presents differing views on the plastics, additive leaching, recyclability porates the generation of greenhouse economic viability of the use of plastic at the end of life, and life cycle analysis. gas emissions as a part of the analysis. waste in road construction. 18 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia (5) Industry standards: At the time and public-private partnerships may Ways forward that this study was conducted, India help fill the aforementioned knowl- was the only country that has adopt- edge gaps on the use of plastic waste The recommendations provided are ed standards guidelines Indian Roads in road construction. Table 1 shows organized by short- and long-term Congress Special Provision 98-2013 through different color coding that recommendations for further re- (IRC SP 98-2013) for the use of plastic most of the aspects of plastic waste search. The achievement of the short- waste in road construction. The Unit- use in road construction still experi- term recommendations will provide ed Kingdom is likely to issue standards ence knowledge gaps and require fur- necessary prerequisites and input into in the near future. Widespread stan- ther research and in-depth analyses. the way the long-term recommenda- dards and guidelines on how plastic Subcategories in green indicate top- tions should be pursued. These rec- waste can be incorporated into roads ics with little uncertainty, which have ommendations are specific to the use are lacking. been extensively researched. Subcat- of plastic waste in road construction, egories in yellow indicate topics in but we also recommend that research- Key knowledge gaps and standards which research was conducted, but ers investigate alternative ways to use regarding the viability of plastic major gaps still exist. Subcategories plastic waste. roads are yet to be determined. Field in red indicate topics in which there is and laboratory research, pilot projects, a high uncertainty level. Table 1. Technology readiness of plastic roads and level of uncertainty in existing knowledge gaps. Technology readiness category Subcategory Projects implemented worldwide Technology feasibility and Industry players involved engineering performance Road cracking resistance Life cycle analysis Generation of HAP when heating plastics2 Environmental issues Additive leaching Recyclability of roads at end of life Generation of microplastics and nanoplastics Cost-effectiveness analysis Lifespan of roads Economic viability Cost-benefit analysis Supply of quality feedstock Note: The following color scheme is used: green - little uncertainty, extensively researched; yellow - research was conducted, but major gaps still exist; and red - high uncertainty level. 2 The production of HAP is a major concern when heating plastics, but we expect that guidelines can be developed to protect occupational health from these pollutants. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 19 Short-term research We recommend that an interdisciplinary team of experts in plastic waste applications, environmental and occupation health, and pavement technology spanning private entities, public-private partnerships, and governments, conduct short-term research to fill the research gaps listed below. Based on the results of the short-term studies, interested stake- holders should determine if and how long-term research should be pursued. Technology feasibility • A gap exists in regard to the quality assurance and control and engineering performance parameters, such as unevenness and skid number (KPMG 2021), of the use of plastic waste in road construction. • It is not known if the use of plastic waste in road construction results in increased road cracking, as compared to conven- tional roads. Environmental issues • Microplastics: Although conventional roads and tire wear are known contributors to global microplastic pollution, we were unable to identify a study on the generation of microplastics and nanoplastics from plastic roads and tire wear. • Additive leaching: Further research should be conducted on organic and metallic additive leaching from roads, includ- ing how different plastic waste melting temperatures and road construction methods may or may not impact the leach- ing of plastic additives. • Recyclability at the end of life: It remains unknown whether the plastic waste in roads can be recycled or if the entire plastic road, including the plastic waste and bitumen, can be recycled. Long-term research If supported by the short-term research, we recommend conducting long-term research and pilot projects to fill the research gaps listed below. We expect that a stocktaking of performance monitoring results from existing pilot projects and plastic roads will also be helpful. Field research and pilot projects should only be pursued if the short-term research results suggest that plastic roads are a viable option. Technology feasibility • Long-term studies on standard measures of road performance, such as road moisture susceptibility, filtrate management as well as engineering performance measures, such as cracking resistance, road moisture susceptibility, are greatly needed. These tests should be conducted under a range of environmental conditions, such as flooding, ultraviolet rays exposure, and extreme events, such as environmental accidents or natural disasters. • The scalability of plastic roads needs to be determined and is likely be based on plastic waste quality and collection rates in an area, ability to increase the percentage of plastic waste used in roads, and the long-term performance of the plastic roads. 20 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Environmental issues • Further research is needed to analyze plastic roads from a life cycle perspective, including greenhouse gas emissions, in lower-income settings. Occupational health • Occupational health guidelines need to be created, which protect human health from the generation of HAP and prevent accidental fires at the asphalt plant (Willis, Yin, and Moraes 2020). Economic viability • Detailed cost-benefit analyses that are ground-truthed with data from the field should be conducted to determine if plas- tic roads are more expensive or cheaper than conventional roads over the long term. Industry standards • We recommend that industry standards be determined to clarify the method used to incorporate plastic waste into bitu- men as well as the amount and types of asphalt and plastic waste. • Over 10,000 chemical compounds are associated with plastics, at least 2,400 of which have known toxicological issues (Wiesinger, Wang, and Hellweg 2021). Further work is needed to standardize the additives used in plastics. The upcoming international, legally incorporating both upstream and tic waste as an input material; further binding treaty to reduce plastic pol- downstream measures. The use of upstream measures to reduce plastic lution calls for a ‘full life cycle ap- plastic waste in road construction is a waste are needed. proach’ to reduce plastic pollution, downstream measure to utilize plas- Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 21 1 Introduction Since plastics commercialization in the 1950s (Geyer, Jambeck, and Law 2017), global plastic production has skyrocketed, so much so that annual plastic production was almost equal to the combined weight of the global hu- man population by 2015 (Worm et al. 2017). Plastic is ubiquitous in many as- pects of our lives, such as clothes, food packaging, medical supplies, and con- sembly (UNEA) will set up an Inter- governmental Negotiating Committee to negotiate an international, legally binding treaty to reduce plastic pollu- tion across plastics life cycle by 2024 (IISD 2022; UNEP 2022a).3 At present, measures implemented to reduce plas- tic pollution are not keeping pace with the rise in pollution. For example, even with immediate, coordinated, and dras- table Trusts and SYSTEMIQ 2020). Thus, entrepreneurs, innovators, and research- ers have begun to invent new technol- ogies that utilize plastic waste as an alternative input material. Example busi- nesses include those creating technolo- gies to prevent plastic leakage into the environment (Schmaltz et al. 2020; Dijk- stra, van Beukering, and Brouwer 2021), collect existing pollutants (Schmaltz et struction materials. Plastics ubiquity has tic global action to reduce plastic pollu- al. 2020; Dijkstra, van Beukering, and also grown in the environment as a glob- tion, 710 million metric tons of plastic are Brouwer 2021), transform recovered al pollutant and has been found in some expected to enter the environment be- plastic waste into new materials, prod- of the most remote corners of the Earth, tween 2016 and 2040 (Lau et al. 2020). ucts, or energy (Dijkstra, van Beukering, such as deep-sea trenches and the at- Innovations that utilize plas- and Brouwer 2021) and advance mon- mosphere (Brahney et al. 2021; Evange- tic waste as an input material have itoring and assessment (Dijkstra, van liou et al. 2020; Fischer et al. 2015). emerged, making use of the growing Beukering, and Brouwer 2021). Recently, governments at the Unit- amounts of plastic waste produced The use of plastic waste as a bi- ed Nations Environment Assembly 5.2 (Dijkstra, van Beukering, and Brouw- tumen modifier in roads, referred to agreed upon the resolution titled “End er 2021). The amount of plastic waste here as plastic roads, has emerged Plastic Pollution: Towards an interna- produced is expected to grow from as an innovation which uses plas- tionally legally binding instrument” 220 million metric tons in 2016 to 430 tic waste as an input material. In this (IISD 2022). Through this resolution, million metric tons in 2040 in a busi- technology, plastic waste is used to the United Nations Environment As- ness-as-usual scenario (The Pew Chari- modify bitumen (less than 10 percent 3 Potential life cycle stages of plastic pollution encompassed in this approach may include extraction of raw materials, design and production; packag- ing and distribution; use and maintenance; disposal; and incineration and landfilling (UNEP 2022b). After use and maintenance, plastic may also enter the reuse and/or recycling life cycle phases, and will once again undergo design and production (UNEP 2022b). 22 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia bitumen replacement) in flexible pave- construction is a viable option for the c Recap the key challenges and ment (Aziz et al. 2015; Nizamuddin et application of plastic waste that also knowledge gaps; and al. 2020). Virgin polymers have also protects environmental and human been used to modify bitumen, aiming health. We met these goals by review- d Develop recommendations to to reduce costs and improve road per- ing the scientific literature, news arti- inform further research and formance (Nizamuddin et al. 2020). cles, patents; conducting interviews road infrastructure in SAR. Since the use of plastic waste in with business representatives and in- road construction targets plastic dependent researchers in this field; and The methods used allowed us to waste after the use and maintenance conducting a cost-effectiveness anal- summarize this technology in an evi- stages, plastic roads are considered ysis (CEA). The key audience for this dence-based report. Detailed methods a downstream measure. Upstream report are policy makers, research- are available in Annex A. measures that promote waste avoid- ers, and transport practitioners who This report has some limitations. ance by targeting natural resource are considering using plastic waste in Reports on the use of plastic waste in extraction and plastic production are flexible pavements. To evaluate if plas- roads do not always specify if the roads greatly needed, as is suggested by the tic roads are a viable option for plastic are used in low-volume or high-vol- upcoming international treaty and the waste application, we collated available ume traffic conditions (Sasidharan, Tor- hierarchy of waste management that information to baghan, and Burrow 2019). Stocktaking prioritizes prevention over reuse, re- of the traffic loads of existing plastic cycling, energy recovery, and disposal a Provide an overview on the roads will further our understanding. (Lazarevic, Buclet, and Brandt, 2010). use of plastic waste in road Plastic roads need to be evaluated over In addition to the upstream measures, construction (dry process) in different traffic loads and environmental we expect that some unavoidable plas- South Asia, in comparison to conditions, including flooding. Technol- tic waste will be produced in the future, conventional roads; ogies that focused on the use of plastic such as medical waste, so downstream waste to replace concrete materials fall measures that utilize plastic waste, b Summarize the environmental outside the scope of this report. such as recycling and upcycling, will impacts, engineering be needed. performance, regulatory In this report, we aim to evalu- considerations, and ate if the use of plastic waste in road economic viability; Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 23 2 Methods To prepare this report, the team reviewed the literature, includ- ing peer-reviewed articles, news articles, and patents; conducted semi-structured interviews of busi- ness representatives and indepen- dent researchers; and conducted a CEA. We conducted a review of news Geographic location of road(s) by city (if available), country, Type of plastic item(s) (bags, bottles, other-specified, unspecified, tires) by count, articles to find out where plastic roads Status of the road at the Amount of plastic (kg or tons), have been implemented by reviewing time of article publication news articles identified in the business (Select one: in use, planned/ news databases ABI Inform and Dow pilot/under construction, or Jones Factiva by using a set of key- planned, but dropped), words. The following information was extracted from the news articles: 24 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Annex A provides a detailed summary of We conducted a CEA to compare the the methods used to prepare this report. costs of the business-as-usual sce- Plastic recycling category (PET Plastic roads businesses were nario (bitumen road without plastic - 1, HDPE - 2, PVC - 3, LDPE identified in news articles and the waste) to the cost of the interven- - 4, PP - 5, PS - 6, Other - 7, business database S&P Capital IQ. tion scenario (use of plastic waste in Unspecified - 8),4 Business representatives ranging from road construction). The scenarios and engineers to founders to public relations modelling assumptions were defined in contacts were interviewed to ground- detail. The CEA also includes the eco- truth our findings. Interview questions nomic pricing of carbon, according to Percent of bitumen, are presented in Annex A. Companies the World Bank’s Guidance Note on interviewed and their responses are pre- Shadow Pricing of Carbon in Econom- sented throughout the report. We also ic Analysis from 2017, and sensitivity interviewed two independent research- analysis. The CEA can be found in de- Name of company constructing ers who are studying the use of plastic tail in Annex K. the road, waste in road construction at scientif- To better understand patented ic and academic institutions. These re- plastic roads technology, we conduct- searchers also reviewed the report for ed a search of plastic roads patents scientific accuracy. in the World Intellectual Property Or- To provide an overview of plas- ganization’s Patentscope database. Name of government financing tic roads technology, we used a set Original patents were reviewed to col- the road, if applicable, of keywords to search the Web of lect the following information: year of Science databases to find peer-re- patent filing and publication, inventor, viewed articles that help us to un- patent applicant, type of plastic waste derstand plastic roads engineering (post-consumer or post-industrial), re- Name of development performance, environmental issues, cycling category of plastic waste, per- organization financing the and economic viability. Articles were cent of bitumen comprised of plastic, road, if applicable, and reviewed and data were extracted to and a hyperlink to the original patent help us answer the following questions: in the Patentscope database. (a) what is plastic road technology? Using the free, open-access data- and (b) what are the environmental base Plastic Policy Inventory (Diana et Total project cost (US$). and economic benefits and downsides al. 2022; Karasik et al. 2020), we iden- of implementing plastic roads? More tified policies adopted in India that than 500 articles were screened to find encouraged the use of plastic waste in 4 The acronyms are defined as poly- the relevant articles. Details on article road construction. Original policy doc- ethylene terephthalate (PET), screening methods and data extraction uments were reviewed to determine if high-density polyethylene (HDPE), parameters are in Annex A. the sections describing plastic pollution polyvinyl chloride (PVC), low-den- reduction efforts referred to the use of sity polyethylene (LDPE), polypro- plastic waste in road construction. pylene (PP), and polystyrene (PS). Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 25 3 Conventional road construction Road construction overview: the use of virgin polymer prise approximately 90–95 percent aggregate and about 5 percent bitu- men is used in flexible pavement con- struction because it is waterproof and men (by weight) (APAI n.d.). viscoelastic6 (Aziz et al. 2015; Rahman, Bitumen is a by-product of crude Mohajerani, and Giustozzi 2020). Visco- Conventional road construction is pri- petroleum that is used to coat and elastic materials are ideal for road con- marily categorized as either flexible bind hot stones to build pavements struction since they regain their original or rigid pavements (Aziz et al. 2015). (Vasudevan et al. 2012). As such, bi- shape after forces are applied from ve- Flexible pavements, which are bound tumen’s price changes based on the hicles traveling on roads. with bitumen,5 comprise 95 percent of price of petroleum and has generally To reduce costs and improve road highways found worldwide (Aziz et al. been shown to increase over time: from performance, alternative binders, 2015; Rahman, Mohajerani, and Gius- US$61.95 per barrel in 2008 to US$97.98 such as polymers, bio-oils, waste ma- tozzi 2020). Rigid pavements are less in 2013 (Aziz et al. 2015). Bitumen com- terials, emulsions, and crumb rubber, frequently used and are bound with prises about 80 percent carbons, mainly have been substituted for bitumen in Portland cement concrete (Aziz et al. aromatic hydrocarbons, and is black or roads in three ways, which differ based 2015; Rahman, Mohajerani, and Gius- brown in color (Aziz et al. 2015; Rahman, on the percent of bitumen replaced tozzi 2020). Flexible pavements com- Mohajerani, and Giustozzi 2020). Bitu- and function of the substitute: 5 Bitumen is referred to as asphalt in the United States and Canada. 6 The viscoelasticity refers to the mechanical properties that are intermediate of viscous liquid and elastic solid (Tanzi, Farè, and Candiani 2019), which allows the pavement to deform in response to a force and then return to its original configuration (Gould et al. 2019). 26 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia a Direct alternative (75– b Bitumen extender c Bitumen modifier 100 percent bitumen (10–75 percent bitumen (<10 percent bitumen replacement); replacement); and replacement) (Aziz et al. 2015; Nizamuddin et al. 2020). Bitumen modifiers are widely used Polyethylenes are thought to be some of ylene vinyl acetate copolymer (EVA), to improve pavement performance the most effective bitumen modifiers to glycidyl methacrylate (GMA), Sty- properties, such as durability, rutting enhance rutting performance (Aziz et al. rene–Isoprene–Styrene (SIS), PE, SBS, resistance, softening point, and visco- 2015; Nizamuddin et al. 2020), which de- Ammonia Polyphosphate (APP), and elasticity (Aziz et al. 2015; Nizamuddin creases cracking performance (Willis, Yin, Acrylonitrile–Butadiene–Styrene (ABS) et. al. 2020; Vasudevan et al. 2012). The and Moraes 2020). (Aziz et al. 2015). Polymer properties following virgin plastic additives are used All polymers reduce thermal sus- influence which polymer is used in a to modify bitumen to enhance road per- ceptibility of bitumen, such as rutting given setting (Aziz et al. 2015). formance: rubber latex, crumb rubber, in warm temperatures and fatigue Plastomers include the follow- styrene, butadiene styrene, styrene–eth- cracking in cold temperatures (Aziz ing plastic types: PE, polypropylene ylene–butylenes (SBS), recycled poly- et al. 2015; Nizamuddin et al. 2020). (PP), EVA, and ethylene-butyl acry- propylene (PP), low density polyethylene Specific polymer types may be used to late or a combination of materials (LDPE), polyethylene (PE), ethylene vinyl modify bitumen to obtain certain de- (Nizamuddin et al. 2020). PE is often acetate (EVA), and polyolefin (Vasude- sired properties. For example, reactive referred to as the most effective plasto- van et al. 2012). SBS is by far the most and plastomer polymers increase the mer and polymer bitumen modifier. It is common polymer additive in bitumen, at stiffness and resistance to deformation well established that PE-asphalt bind- about 2 percent replacement. due to traffic loads while elastomers er modification improves performance Synthetic and natural polymers have improve elastic properties (resistance by resisting fatigue and rutting as com- been used to modify bitumen since 1843 to fatigue) (Nizamuddin et al. 2020). pared to unmodified roads (Nizamuddin with construction projects beginning in Plastomers are often cheap and im- et al. 2020). High density polyethylene the 1930s in Europe and North Ameri- prove binder stiffness at high tempera- (HDPE) and low-density polyethylene ca (Aziz et al. 2015). Polymer modifica- tures, which can result in resistance to (LDPE) have been studied to deter- tion of bitumen is extensively practiced permanent deformation. mine which polyethylene better enhanc- worldwide in high-volume roadways to Three polymer categories are es road properties. HDPE (optimum at enhance road performance by improving used to modify bitumen: plastomers, 12 percent by weight of bitumen) has pavement elasticity, cohesion, moisture elastomers, and reactive polymers been shown to enhance the properties resistance, fatigue life, and performance (Nizamuddin et al. 2020). For exam- of the pavement more so than LDPE by at high temperatures by decreasing pave- ple, polyphosphoric acid (PPA) is a increasing road stability, reducing den- ments resistance to deformation and low polymer that has been used to modify sity, and increasing air and mineral ag- temperatures (Nizamuddin et al. 2020). bitumen. Others used with PPA are eth- gregate voids (Aziz et al. 2015). Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 27 4 Just as virgin polymer is used in road construction, recycled plastic waste has also been used been used in recent times, primarily to modify bitumen. Plastic waste can be used as a direct al- ternative to bitumen (75–100 percent bi- tumen replacement), bitumen extender (10–75 percent bitumen replacement), Use of plastic waste in road construction tive to bitumen or as a substitute for ag- gregate. PlasticRoads is an example of a business that uses plastic waste as a di- rect alternative to bitumen. In addition, the Solid Waste Institute for Sustainabil- ity at the University of Texas at Arlington is conducting studies on plastic waste as a substitute for aggregate (Box 1). Plastic waste can be categorized by the seven resin identification codes (RICs), which are based on the struc- ture of the polymer backbone of plastics. The seven RICs, recyclability, example products, and percentage of the plastic waste composition in South Asia can be found in Figure 1. One and bitumen modifier (less than 10 per- physical property that varies between cent bitumen replacement) (Aziz et al. Plastic waste RICs is the melting point (Annex Ta- 2015; Nizamuddin et al. 2020). Plas- ble 10) (Willis, Yin, and Moraes 2020). tic waste is most commonly used as a Plastic waste broadly falls into two This property is important for the in- bitumen modifier (Willis, Yin, and Mo- categories based on its source: corporation of plastic waste into road raes 2020). Since bitumen constitutes post-consumer plastic waste and construction because plastic is melted about 5 percent of a flexible pavement post-industrial/manufacturer’s plas- to coat the aggregate or mix with the road by weight (APAI n.d.), the use of tic waste. Generally, manufacturer’s binder (Willis, Yin, and Moraes 2020). plastic waste as a bitumen modifier, for plastic waste is cleaner than post-con- About 9 percent of plastic waste pro- example, would comprise about 0.5 sumer plastic waste and requires less duced between 1950 and 2015 was re- percent of the total road. Unless stat- sorting, making manufacturer’s plastic cycled (Geyer, Jambeck, and Law 2017). ed otherwise, the term ‘plastic roads’ in waste easier to recycle (Willis, Yin, and Although some plastic waste can be re- this report refers to the incorporation of Moraes 2020). Post-consumer plastic cycled multiple times successively (Erik- plastic waste into road construction as waste is collected from municipal solid sen et al. 2019; Geyer, Jambeck, and Law a bitumen modifier using the dry pro- waste drop-off locations, open dumps, or 2017), 90 percent of the recycled plastic cess. Multiple businesses and research- households (Willis, Yin, and Moraes 2020; waste has only been recycled once; so ers are developing technologies that Kaza et al., 2018). The plastic waste that in the current scenario, recycling delays increase the amount of plastic waste we are referring to in this report primari- rather than avoids plastic disposal (Gey- used in roads, either as a direct alterna- ly refers to post-consumer plastic waste. er, Jambeck, and Law 2017). 28 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Figure 1. Plastic RICs and amount consumed in kilotons in South Asia in 2018. The total plastic waste consumed domestically in South Asia is estimated to be 24,868 kilotons in 2018 (UN Comtrade 2021). Sources: CalRecycle (2021) and World Bank (2021). South Asia region plastic Plastic Resin Identification Code consumption (kilotons in 2018) Polyethylene terephthalate (PET) 1 Commonly recyclable Example products: soda bottles Recycled into many products (e.g., bottles, fibers) 2,561 High-density polyethylene (HDPE) 2 Often recyclable Example products: milk and juice bottles Recycled into many products (e.g., toys, trash cans) 3,126 Polyvinyl chloride (PVC) 3 Not commonly recycled Example products: house flooring, pipes, garden hoses, house siding 4,533 Low density polyethylene (LDPE) 4 Not commonly recycled Example products: cellophane, disposable diaper liners 3,670 Polypropylene (PP) 5 Not commonly recycled Example products: packaging, tubes, textiles 7,635 Polystyrene (PS) 830 Commonly referred to as “Styrofoam” 6 Example products: coffee cups, food containers/ packaging, egg cartons Can be recycled, but not common Other 7 Not commonly recycled Includes all plastic reins other than 1-6 and/or mixtures of resins 3,001 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 29 The Indian Roads Congress (IRC 2013) These include plasticizers, flame retar- in road construction and conventional recommends the use of LDPE, HDPE, dants, stabilizers, antioxidants, fillers, road construction, which often incor- PET, and PU (RIC 7, Other) plastic waste impact modifiers, colorants/pigments, porates virgin plastic, can be found in in road construction (dry process), thus lubricants, and other additives such as Figure 2. including both recyclable and some biocides. Recent estimates note that Only plastic waste that meets not commonly recycled plastics. In In- over 10,000 compounds are associat- quality control standards can be used dia, the adoption of an extended pro- ed with plastics, many of which have to modify bitumen, which must occur ducer responsibility law (PTI 2022) may unknown health effects—about 2,400 at the central asphalt plant. Robust shift the plastic waste used in roads to have known toxicity concerns (Wi- specifications on the recycling pro- be only those plastics that are unrecycla- esinger, Wang, and Hellweg 2021). cesses required and properties of the ble. LDPE is one of the plastics currently Plastic waste must pass quality recycled plastic for incorporation into recommended by the IRC to be used in standards and undergo sorting, de- asphalt pavements is lacking in most road construction, and this plastic is not contamination, shredding, and po- cases (Willis, Yin, and Moraes 2020). commonly recycled. The potential for in- tentially washing prior to mixing with The IRC (2013) standards “Guidelines corporation of otherwise non-recyclable aggregate at the asphalt plant. To en- for the Use of Waste Plastic in Hot Bi- plastics into road construction makes sure that the correct plastic type is used tuminous Mixes (dry process) in Wear- plastic roads a potentially helpful option in road construction, plastic must under- ing Courses” provides a starting point for the application of plastic waste. Fur- go collection and sorting by RIC. Plastic that can be rigorously evaluated to ther research is needed to ensure that may be collected from multiple loca- create standards. The IRC (2013) guid- the quality of plastic waste used in road tions, including landfills, dumps, and ance notes that plastic waste must be construction does not compromise envi- the environment. In addition, plastic collected, cleaned, and shredded in a ronmental and human health. must undergo chemical and biological shredding machine and mixed with Plastic waste is a complex cock- decontamination and potentially further aggregate and bitumen at the central tail of chemical contaminants (Roch- washing (Willis, Yin, and Moraes 2020). mixing plant. These standards provide man et al. 2019). Although the chemical During mechanical recycling, plastic also specifications on the size, chemical backbone of the plastics within a re- needs to be shredded, which allows the specifications like dust and impurities cycling category is the same, plastics plastic to pass through sieve mesh siz- and melt-flow value, and recycling cat- contain chemical additives that are es in millimeter (mm) ranges (Gopinath egory/type of plastic waste that can be not standardized within or between et al. 2020), noted to be 2.50–4.36 mm safely used in asphalt in order to pro- recycling categories (Rochman et al. by Vasudevan et al. (2012). Shredded, mote decent working conditions for 2019). Additives are used in plastics, decontaminated plastic may under- those involved in this sector.7 Further at about 7 percent of plastic by mass go further sorting based on separation discussion of these standards is provid- (Geyer, Jambeck, and Law 2017), to properties and quality control measures, ed in the Regulatory Landscape section provide useful and desirable proper- such as density, melting point, and color and a sample of the text is shared in ties, such as elasticity and color. Since (Willis, Yin, and Moraes 2020). Annex D. these additives are not strongly bond- Shredding plastic waste into ed to the polymer, plastics can readi- smaller sizes increases plastics sur- Further research will ly leach additives into the surrounding face area and enhances binding environment (Li et al. 2016; Wright and between the plastic and bitumen (Go- be needed to determine Kelly 2017). A sample of plastic addi- pinath et al. 2020). The aggregate is plastic quality standards tives that make up to the 2,000 million heated to 170°C and then the shredded and methods of plastic metric tons (MMT) of plastic additives plastic is placed over the heated ag- waste incorporation to expected to be produced by the end of gregate, which then softens and coats 2050 (Geyer, Jambeck, and Law 2017) it (Gopinath et al. 2020). A compari- best protect human and can be found in Annex B, Table 11. son between the use of plastic waste environmental health. 7 PVC and black colored plastic waste is not recommended Indian Roads Congress Special Provision 98-2013 (IRC SP 98-2013). 30 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Figure 2. Process of building a conventional road or plastic road (wet and dry process). Each of the plastic waste processing steps has costs associated that are discussed in the Economic Analysis section. a Wet process Dry process Conventional road construction b treatment of plastic waste for road construction c treatment of plastic waste for road construction Raw material Raw material Raw material Manufacture Manufacture Manufacture Monomer production Monomer production Monomer production Polymer production Polymer production Polymer production Plastic conversion Plastic conversion Use and end of life Use and end of life Use and end of life Mixture with bitumen Use Use Road construction Collection Collection Sorting Sorting Treatment Treatment Plastic mixed with bitumen Plastic mixed with aggregattes Road construction Aggregate mixed with bitumen Road construction Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 31 Plastic roads Plastic was first invented in the early Bunzl & Biach AG in the United King- 1900s and gained widespread com- dom. A little under fifty years later, In- A brief history of key events in the in- mercialization and use in the 1950s. To dia is reported to have 100,000 km of vention of plastic and later the use of our knowledge, the first patent filed for plastic roads. Patent applications for plastic and rubber tire waste in road the use of plastic waste (excluding rub- plastic waste increased between 1935 construction is shown in Figure  3. ber) in road construction was in 1974 by and June 2017(Annex B, Figure 6). Figure 3. Timeline of key events. Sources include patents and Denning and Carswell (1983); Mercer (1997); Willis, Yin, and Moraes (2020). 2013 1907 1983 Indian Roads Congress Leo Baekeland invents Denning and colleagues invent releases specifications on the first mass-produced, Novophall ® a polyethylene- the use of plastic waste in synthetic plastic: Bakelite modified bitumen road construction 1950s Commercialization Late 1980s-2000 2001-2020 of plastics and Al least 11 patent applications widespread use Nineteen patent filed using waste plastic or applications filed rubber in road construction using waste plastic Novophall ® used in roads in or rubber in road >12 countries construction 1974 2004 Bunzl & Biach AG apply for Indian scientist Dr. Rajagopalan the first patent using PS, Vasudevan reports plastic LDPE, HDPE, PP, PS, PVC in roads technology in the road construction scientific literature 1935 1995 2020 Albert Ernest Horatio Toronto-based company India reported Oussek applies for a patent licenses Polyphalt ®, waste to have over using rubber tires (5-15%) plastic and ground rubber 100,000 km of in road construction tires in asphalt plastic roads 32 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Composition and method Barriers exist that make it difficult to prevent phase separation; however, of plastic waste used in ensure the quality of plastic roads. agitated storage tanks are not widely road construction For example, when using the wet pro- available to contractors (Willis, Yin, and cess, phase separation between the Moraes 2020) and the financial risk of Recycled plastic waste is incorporat- plastic and binder is an engineering investing in these tanks for an emerg- ed into asphalt for road construction problem (Vasudevan et al. 2012; Wil- ing technology is high. As such, either a in one of two methods: (1) wet pro- lis, Yin, and Moraes 2020). However, technological change that avoids phase cess or (2) dry process. Plastic waste some companies, such as Neo, have separation or accessibility to the agi- can be mechanically or chemically re- reported that that their roads do not tated storage tanks may help to break cycled prior to incorporation into the undergo phase separation due to tech- down this barrier. Quality control and asphalt. A brief description of the wet nological advancements (Box 1). Phase assurance is greatly needed to ensure and dry processes, the role of the plas- separation changes the physical prop- that the plastic is uniformly distributed tic waste, plastic types used, and esti- erties of the pavement (Nahar 2016). in the tank during storage as well as in mates of the amount of plastic per 1 km The use of agitated storage tanks at the the road when laid for paving (Willis, of road can be found in Table 3. plant have been noted as a method to Yin, and Moraes 2020). Table 3. Wet and dry process of plastic road construction. Sources include Gill and Abid 2019; Willis, Yin, and Moraes 2020; and the IRC (2013) specifications. Method of Plastic (tons) incorporating Description of method Role of plastic Plastic types per 1 km of plastic road8 Recycled plastics in the Linear low density form of powder are added Polymer modifiers, polyethylene Wet process to bitumen, heated at 160– 0.48–1.9 asphalt replacement (LLDPE), LDPE, 170°C, mechanically mixed, HDPE9 and then aggregate added Aggregate replacement: PP, Plastic waste is shredded Binder modifier, mixture PET, PS, PC10 and mixed with preheated modifier, aggregate Dry process Mixture modifier: 0.95–4.52 aggregates prior to adding replacement or a any plastic type bitumen at 160°C combination other than PVC11 in most cases 8 The amount of asphalt that is needed to construct a 1- km road will vary based on the width and depth of the road. These factors can vary across ge- ographies and across types of roads (for example, low volume or high volume). Assuming a standard asphalt density of 2,322 kg/m3 , 1 km of road with a width and depth of 1.2192 m (4 feet) and 0.1524 m (6 inches) is roughly thought to weigh about 475.72 tons. We also assume an estimated weight of plastic as between 2-8 lbs/1 ton of asphalt for wet process and 4-19 lbs/1 ton of asphalt mixture for dry process. These calculations are rough esti- mates based on Georgiev, n.d., Gill and Abid 2019; Willis, Yin, and Moraes 2020; and the IRC (2013) specifications and further details in Annex C. 9 These plastic types are used due to low melting points. 10 These plastic types are used due to high melting points. 11 PVC cannot be used due to the concern of chloride and dioxin emissions. Box 1 features a research development by Behl, Sharma, and Kumar (2014) at the Central Roads Research Institute that has utilized PVC in road construction. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 33 Plastic waste should only be incorpo- gases up to 760°C, thus increasing the pilot and research projects are need- rated into asphalt at the central as- fire risk (Willis, Yin, and Moraes 2020). ed (Sasidharan, Torbaghan, and Bur- phalt plant rather than an informal In the wet process, recycled plastics row 2019). setting. Heating plastics can generate are added using the terminal blending Several businesses research, de- hazardous air pollutants such as vol- or plant blending approach, avoiding velop, pilot, and sell this technology. atile organic compounds and polycy- the aforementioned fire risks (Willis, Businesses interviewed to compile clic aromatic hydrocarbons (Willis, Yin, Yin, and Moraes 2020). Occupational this report have constructed plas- and Moraes 2020). As such, the heat- training should be given so that con- tic roads in the United States (Neo, ing of plastics for incorporation into struction workers can safely handle the Dow), Mexico (Dow, PlasticRoads), asphalt should only be conducted in a waste. This may involve drafting techni- Colombia (Dow), Vietnam (Dow), controlled occupational setting where cal manuals for the workers (Sasidha- and the Netherlands (PlasticRoads). guidelines and standards that protect ran, Torbaghan, and Burrow 2019). A subset of companies partaking in human health have been established. business involving the use of plastic The Solid Waste Institute for Sustain- Use of plastic roads waste in road construction and the lo- ability at the University of Texas at Ar- in other regions cation of company headquarters or the lington is currently researching if it is arm of the company focused on plas- possible to reduce the production of We found 132 total plastic roads proj- tic roads can be found in Annex E. A toxic fumes by heating plastic waste ects worldwide (Figure 4). We did not sample of companies and research at temperatures below 200°C. Further include multiple projects that were oc- institutes involved in the use of plas- research and verification is needed to curring at the same stage (for example, tic waste in road construction can be confirm this. constructed) in the same geograph- found in Box 1. Current asphalt plants are not set ic location as to not potentially over- Fifty-eight percent of plastic up to incorporate plastic waste. Fur- count. Just recently, Pakistan has also roads projects surveyed in news ar- ther research and standards are need- constructed its first plastic road in the ticles were in planning, pilot, or con- ed to reduce the risk of fires at the capital city of Islamabad (Daily Paki- struction phases at the time of source asphalt plant (especially for the dry stan Global 2021). Furthermore, recent article publication while 37 percent process) and generation of hazard- research from the University of Texas reported were already constructed ous air pollutants while heating plas- at Arlington funded through the Tex- and in use (Figure 5). The 5 percent tics (Willis, Yin, and Moraes 2020). In as Department of Transportation has of projects that were planned but were the dry method, recycled plastics are piloted the use of plastic waste in road dropped were for roads that would introduced to the asphalt at the cen- construction in raised highway beds have been in Arraiján, Panama; Bengal- tral plant often through the recycled (Halsey 2018). Since this technology is uru, India; Doon, Dehradun, India; Mum- asphalt pavement (RAP) conveyor or relatively new and most countries lack bai, India; San Carlos, Chiriqui, Panama; the cold feed through which recycled standardized guidelines, long-term and Thiruvananthapuram, India. plastics enter the drum, which holds outcomes remain unclear and further 34 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Figure 4. Map of plastic roads. Note: Sources for points on the map are in Annex E. Constructed Planned for future construction but dropped Planned / pilot / under construction Figure 5. Plastic roads use status.12 56% Under construction/planned for future 38% 5% Planed for the construction/pilots and trials Constructed future but dropped 12 We reported projects as ‘In use’ if they were noted to be complete at the time of news article publication. Completed projects could not be undergoing pilots or trials. We grouped pilot projects, projects under construction, and projects planned where it was unclear if construction necessarily started or not into one group: ‘Planned/pilot/in construction’. These three categories were grouped together since this level of detail was often not shared in the news articles reviewed. Projects that were planned, but dropped are also noted as ‘Planned, but dropped’. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 35 Box 1. Sample of companies and research institutes Central Roads Research Institute The Central Roads Research Institute, a prestigious laboratory in India, recently patented a PVC-modified bitumen, using particular types of medical and pipe waste (Behl, Sharma, and Kumar 2014). Initial tests indicate that this new technology can be used as pavement. Further partnerships with bitumen manufacturers will provide insight into the scalability of this technology and the locations where it may be piloted. The Dow Chemical Company The Dow Chemical Company, often referred to as Dow, has been developing asphalt modifiers from plastic waste. For example, Dow has been a leader in this technology since it began demonstration projects in 2018. Over 300 ki- lometers of plastic roads have been built by Dow across all continents. Dow uses an ELVALOYTM reactive elastomeric terpolymer (RET) mixed with post-consumer recycled plastic waste content to modify the asphalt and reduce road resurfacing needs. Neo The United States-based company Neo has developed a method of converting PET to polyurethane elastomer, which can chemically bind to the rock. As such, Neo does not appear to be facing the phase separation issues noted when incorporating plastic into asphalt using the wet process. PlasticRoads Based in the Netherlands, the company PlasticRoads uses locally sourced recycled polypropylene as a direct alter- native to asphalt pavement (almost 100 percent bitumen-replacement). PlasticRoads blocks are made almost en- tirely of plastic except for a thin coating of stone mineral to avoid abrasion and wear directly on the recycled plastic. This technology reduces carbon dioxide emissions and costs by about 52–70 percent and about 50 percent, respec- tively, in comparison to conventional roads. To address runoff, PlasticRoads has included a filtering mechanism to remove abrasion particles from infiltrating water that may enter the topsoil. PlasticRoads has six pilot projects in the Netherlands and one pilot in Mexico City. Solid Waste Institute for Sustainability at the University of Texas at Arlington Research at the Solid Waste Institute for Sustainability (SWIS) have found that plastic can be used as a base and subbase course material, substituting between 5 and 10 percent of aggregate in pavement (unpublished research). This development would increase the amount of plastic waste used in road construction by 10–20-fold. Wenger Manufacturing and Enviroplaz Although the focus of this report is on the use of plastic waste in flexible, bituminous pavement construction, Wenger Manufacturing and Enviroplaz created Plazrok USA to use mixed unrecyclable plastics in substitution for stone ag- gregate in concrete materials (deemed ‘PlazrokTM’) in precast concrete and blocks. PlazrokTM creates a market for unrecyclable plastics that also cuts construction transportation costs since the concrete is lightweight. PlazrokTM highlights other potential uses of plastic waste in construction more broadly, such as in pedestrian sidewalks. 36 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia About 5% of plastic roads projects tional law in India promoting the use around 15 local bodies, which that were planned were dropped. of plastic waste in road construction spent Rs 5.19-Rs 9.82 lakh for The reported reasons vary, includ- and government-issued standards. The purchase of shredders and bal- ing factors such as government sup- project planned in Doon, Dehradun, In- ing machines, didn’t sell shred- port, economic issues, and plastic dia was stopped for similar reasons. ded plastic between 2017 and waste quality. In Panama, plastic roads According to officials, the “unsegre- 2019. Yet, LSGD tried to keep were not constructed due to the lack gated and low quality of plastic waste the system alive. Suchitwa Mis- of the government’s approval of Bill available to the PWD” was the primary sion executive director reported 687, which would have authorized the deterrent (Jha 2019). In Thiruvanantha- in 2018 that the average daily use of recycled materials, including puram, India, the following economic expense to run plastic shred- plastics, in secondary streets in Pana- issues were noted: ding unit was Rs 2,057.5, while ma (Noticias Financieras 2019a). Rea- the income was just Rs 1,095. sons noted for stopping the project “ ...some local bodies, which Local bodies were asked to pay in Bengaluru, India were the costs of spent Rs 5-9 lakh for purchas- Rs 965 as viability gap fund for cleaning, sorting, and drying of plastic ing machines, had not sold a the first six months.” (The Times waste (Chakravorty 2019). Chakravorty single kilo of plastic for tarring of India 2019) (2019) also noted a lack of government in the past two years. Data ob- support, despite the passing of a na- tained through RTI showed that Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 37 5 Although both the wet and dry pro- cesses can be used to construct plas- tic roads, each process has relative advantages and disadvantages. For example, phase separation of binder and plastic is a disadvantage of using the wet process that is not encountered in the dry process (Willis, Yin, and Mo- Key findings and knowledge gaps ble 3). However, dry process has the re- ported disadvantage of increasing the fire risk at the asphalt plant and gener- ation of hazardous air pollutants if oc- cupational guidelines are not in place. Plastic roads in the pilot or con- struction stage are found on every continent other than Antarctica. How- undergoing pilot tests, under construc- tion, or planned for future construction at the time of news article publica- tion. Only 5 percent of projects were planned for the future, but dropped. These projects were in India and Pana- ma. Reasons attributed to dropping the project were lack of governmental ap- raes 2020). Dry process can encom- ever, all countries other than India proval (Panama), lack of governmen- pass greater amount of plastic (tons currently lack plastic roads guidelines tal support (India), plastic waste quality per 1 km of road) than wet process (Ta- and standards. Most plastic roads are (India), and economic viability (India). Environmental sustainability The sustainability of plastic roads en- Overall, the scientific literature sug- (EEE) Index, comparing the following compasses the (1) life cycle analysis, gests that the use of plastic waste in disposal methods in India: landfilling, (2) leaching of additives, (3) micro- road construction is beneficial from a recycling, pyrolysis, liquefaction, road plastics, and (4) end-of-life recyclabil- life cycle analysis perspective though construction and tar, and concrete. The ity. These categories were chosen based key gaps exist regarding the leaching best option according to the EEE Index on the availability of studies in the liter- of plastic additives and generation of was plastic roads and the use of plastic ature as well as environmental impacts microplastics. Gopinath et al. (2020) waste in concrete for buildings (Gopi- that were thought to have a great impact conducted an analysis that created an nath et al. 2020). These options per- on the sustainability of plastic roads. Energy, Environmental and Economic formed well due to the: 38 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia “lack of harmful greenhouse gas ing plastic waste over the past 15 years an and Shishehbor 2019). Maintenance emissions, the ease of localiza- (Biswas, Goel, and Potnis 2020; Wil- and end of life were noted to be depen- tion and the high sustainability lis, Yin, and Moraes 2020). The lack of dent on the performance of the asphalt and durability of the produced LCA studies focusing on the use of PET mixture (Pouranian and Shishehbor material and the constructed waste is worth noting given that PET 2019). Notably, crumb rubber and re- roads and buildings, the exis- was the second most frequently stud- cycled plastics decreased greenhouse tence of which significantly out- ied plastic type (behind PE) in our re- gas emissions and energy consumption weighs demerits such as the port (Annex B, Figure 7). within the maintenance and end-of-life inability to recover expended Overall, the LCA studies reviewed phases as compared to conventional energy” (Gopinath et al. 2020). (Lastra-Gonzalez et al. 2021; Santos asphalts and other asphalt mixtures et al. 2018, 2021; Vila-Cortavitarte et evaluated: recycled asphalt pavement, Others have also noted that the use of al. 2018) consistently showed an en- recycled asphalt shingles, construc- plastic waste in road construction re- vironmental impact reduction, includ- tion and demolition waste, copper and duces carbon dioxide emissions of up ing greenhouse gas emissions, from steel slag, and vacuum tower bottoms15 to 3 tons/km of road compared to con- the use of plastic waste14 in road con- (Pouranian and Shishehbor 2019). ventional roads (Sasidharan, Torbaghan, struction with few exceptions (San- However, crumb rubber can contain and Burrow 2019; Vasudevan et al. 2012). tos et al. 2021). A review by Pouranian hazardous compounds, such as polycy- and Shishehbor (2019) summarized clic aromatic hydrocarbons and phthal- LCA Studies whether the use of recycled plastics in ates (Armada et al. 2022). the production, construction, mainte- Life cycle assessment (LCA)13 is a nance, and end-of-life phases were re- Leaching valuable tool for understanding the ported to be associated with positive, environmental impacts of a product negative, or the same effects on emis- Major knowledge gaps regarding the over its lifespan. Overall, environmen- sions and energy, in comparison to con- leaching of (1) inorganic and (2) or- tal impact reductions were consistently ventional asphalt roads. Pouranian and ganic chemicals from plastic roads ex- found from the use of plastic waste in Shishehbor (2019) found that the use ists. Leaching of additives from plastic road construction and often depended of recycled plastics has both positive waste is a chemical hazard. Sasidha- on life span of the road. Further details and negative environmental impacts on ran, Torbaghan, and Burrow (2019) regarding the LCA studies are summa- emissions and energy used during the note that toxic additives may leach rized in Annex F. aggregate production phase. Howev- while plastic waste is being cleaned, The LCA studies reviewed were er, environmental benefits in emissions prior to incorporation into asphalt. primarily in high-income countries in and energy were noted during binder Initial reports from conference papers Europe (Spain and France) and one production for plastic roads (Pourani- indicate that leaching and fume emis- in Australia. Thus, a key gap appears an and Shishehbor 2019). At the plant sions were not reported as issues for the to exist in geography, notably lack- and during the construction phase, as- UK company MacRebur’s plastic waste ing countries in Latin America and the phalt containing recycled plastics per- (Sasidharan, Torbaghan, and Burrow Caribbean, Middle East and North Af- formed similarly for greenhouse gas 2019; White 2019) though further verifi- rica, South Asia, and Sub-Saharan Af- emissions and energy as convention- cation and research is needed. rica regions. The lack of LCA studies al asphalt (Pouranian and Shishehbor A few studies have evaluated the identified in South Asia is particularly 2019). During the maintenance and leaching of metallic additives from surprising given that India has been a end-of-life phases, plastic roads im- plastic waste used in road construc- leader in the construction of roads us- proved emissions and energy (Pourani- tion. We identified two scientific articles 13 The International Organization for Standardization (ISO) standard 14040, which regulates LCA defines it as the “compilation and evaluation of the in- puts, outputs and the potential environmental impacts of a product system throughout its life cycle.” 14 PS, waste nitrile rubber, EVA, LDPE, HDPE, packaging. 15 Residue from vacuum distillation process in oil refining (Pouranian and Shishehbor 2019). Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 39 that evaluated the leaching of plastic researchers from the Kerala Highway Re- use of plastic waste in road construc- additives: Fernandes, Silva, and Oliveira search Institute (KHRI) and Central Road tion does not result in environmental (2019a, b). The full list of the specific mix- Research Institute (CSIR) indicate that health issues, such as aquatic and/or tures and heavy metal additives evalu- studies on the leaching of organic ad- terrestrial toxicity. ated in both studies are given in Annex ditives from plastic roads are ongoing. The generation of hazardous chlo- G. The asphalt mixtures studied include Organic additives comprise a high per- rine gases during the process of road waste motor oil or recycled engine oil centage of plastic by weight and have construction was noted by Sasidha- bottoms and one of three waste plastics: environmental and human health im- ran, Torbaghan, and Burrow (2019). HDPE, SBS, or crumb rubber in varying pacts; for example, plasticizers can be This study found that bitumen alone percentages. Although these samples are between 10–70 percent weight of ad- generated harmful fumes, toluene, not ideal due to the use of waste motor ditive by weight of plastic (Hahlada- benzene, and aliphatic, cyclic, and aro- or engine oil bottoms, which is outside of kis et al. 2018). Phthalates function as matic hydrocarbons (White 2019). the scope of this study, these studies are plasticizers in plastic and are found in reported here due to limited other sci- many consumer products (Grindler et Microplastic Generation entific literature identified on this topic. al. 2018). Phthalates are known endo- Fernandes, Silva, and Olivei- crine disruptors and have been associ- A knowledge gap exists regarding ra (2019a) primarily found that ated with reproductive concerns, such the amount of microplastics generat- leaching of certain heavy metals as a decreased fecundity, pregnancy ed from plastic roads and their tox- and elements is not beyond legal loss, and other adverse childbirth-relat- icity, in comparison to conventional limits outlined in the Portuguese ed outcomes (Grindler et al. 2018). Given roads. The company Neo and the Na- Decree-Law no. 183/2009. For Cad- the high percentage of these additives in tional Center for Asphalt Technology miun (Cd), Chromium (Cr), Nickel (Ni), plastic and the potential environmental separately reported that their institu- and Lead (Pb), the samples contain- and human health effects, the leaching tions are undertaking research efforts ing HDPE and styrene–ethylene–bu- of these compounds from plastic roads to answer this question. We report be- tylenes (SBS) had less than or equal remains an important knowledge gap. low the generation of microplastics and to the same amount of each metal as Runoff from conventional roads future projections from conventional the reference material (Fernandes, contains contaminants with known road traffic emissions. Silva, and Oliveira 2019a). Similarly, toxicological effects, like metals and When vehicle tires mechanical- Fernandes, Silva, and Oliveira 2019b polycyclic aromatic hydrocarbons, ly abrade conventional road surfac- found that all mixtures tested be- as well as organic contaminants that es, both tire and brake wear particles low the Portuguese Decree-Law no. are not yet identified and contain are generated, creating microplas- 183/2009 for the leaching of Cd, Cr, currently unknown environmental tics16 and nanoplastics17 (Evangeliou Copper (Cu), Ni, Pb, and Zinc (Zn). impacts. Tire wear particle leachate et al. 2020; Leads and Weinstein 2019; The study design and leaching data and roadway runoff has been linked Sommer et al. 2018). There are three is summarized in Appendix I. Further to Coho salmon mortality (McIntyre broad categories of road traffic emis- research is needed to determine if et al. 2021) and developmental tox- sions generated by vehicles and roads: heavy metal and element leaching is icity for fathead minnows (Chibwe tire wear particles, brake wear particles, harmful to aquatic and terrestrial an- et al. 2021). Conventional road runoff and road sources (for example, poly- imals and ecosystems. and tire/road wear particles have tox- mer-modified bitumen, road marking Our study did not identify any sci- icity issues. The toxicity of road runoff paint) (Evangeliou et al. 2020).18 Road entific articles researching the leach- and tire/road wear particles has not yet traffic emissions exclude exhaust parti- ing of organic contaminants from been studied to our knowledge. Fur- cles (Sommer et al. 2018). Based on the plastic roads. However, interviews with ther research should ensure that the driving speed, traffic flow, and compo- 16 Plastics less than 5 mm in size (Arthur, Baker, and Bamford 2009). 17 Plastics less than 100 nm in size (Jahnke et al. 2017). 18 These three groups are sometimes all grouped together under the term ‘tire wear particles’. 40 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia sition of the traffic, particles vary in size, 4.8–167 and 26–67 kilotons of annual in road construction is not yet com- composition, and structure (Sommer et road microplastic emissions, respec- monly used except for roads in India. al. 2018). When these particles are gen- tively (Evangeliou et al. 2020). A break- erated, they accumulate on the road down of the microplastic emissions Recyclability and can be carried to the surrounding quantified by size and a summary of environment by wind, passing traffic, the methods used is in Annex H. It remains unknown whether plastic runoff, and can be dispersed into the Overall, the studies suggests that roads can be recycled at the end of atmosphere (Brahney et al. 2021; Evan- microplastic emissions from tires, life. Some companies have claimed geliou et al. 2020; Leads and Weinstein breaks, and road wear generate a that it is possible; however, this has 2019; Sommer et al. 2018). great amount of the microplastics not yet been established in the scien- A recent study found that road that end up in the environment. Mod- tific literature to our knowledge (Willis, and brakes generated 84 percent of eling by Lau et al. (2020) found that Yin, and Moraes 2020). Conventional microplastic emissions to the atmo- by 2040, tire particles are expected to asphalt pavement is highly recyclable; sphere in the Western United States contribute 93 percent of global micro- for example, pavements were recycled (Brahney et al. 2021). Evangeliou et al. plastic pollution (by mass), even with at a rate of over 99 percent in the Unit- (2020) conducted similar global esti- coordinated, drastic global efforts to ed States in 2012 (Williams et al. 2018). mates of the amount of microplastics reduce plastic pollution. These studies However, in India, asphalt pavements generated from tire and brake wear. are primarily representing conventional are not removed or recycled on more In Asia, tire and brake wear generated roads because the use of plastic waste than 70 percent of roads. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 41 Regulatory and policy landscape: examples from India Governments worldwide are adopt- ing policies to reduce plastic pollu- tion.19 We identified the following policies adopted in India as calling for the use of plastic waste in road con- struction as a part of a mandate to re- duce plastic pollution. Despite these regulations, plastic is not always incor- porated into roads. 1 Ministry of Environment, Forest, and Climate Change Notification. Adopted in 2016 at the national level in India, this policy notes that “local bodies shall encourage the use of plastic waste (preferably the plastic waste which cannot be further recycled) for road construction as per Indian Road Congress guidelines or energy recovery or waste to oil etc. The standards and pollution control norms specified by the prescribed authority for these technologies shall be complied with.” 19 A review of broader plastic pollution reduc- tion policies is outside of the scope of this report. For a detailed analysis of the global plastics policy landscape, please see Diana et al. (2022); Jambeck et al. (2018); Karasik et al. (2020); Schnurr et al. (2018); Xanthos and Walker (2017). 42 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 2 Plastic Waste Management Waste Management (Amendment) SP 98-2013) is the only standard that (Amendment) Rules, 2018. Rules, 2022’, which aim to extend- currently exists. India is also home to Adopted in 2018 at the ed producer responsibility regarding road research institutions that study subnational level in Punjab, India, plastic packaging, promote a circu- the use of plastic waste in road con- this amendment also notes that lar plastics economy, and develop al- struction, such as the CSIR (New Delhi, plastic waste should be used ternatives to plastics (PTI 2022). The India), and the KHRI. These institutes in road construction using the Government of India’s Ministry of Road as well as many others contribute to same policy instruments as the Transport and Highways mandates the India’s expertise in the use of plastic 2016 national-level ‘Ministry of periodic renewal of roads within 50 waste in road construction. Environment, Forest, and Climate kilometer of urban areas with over 5 The United Kingdom has start- Change Notification’. lakh (=500,000) people, including at ed to create guidance on the use of least 10 kilometer stretches of pilots plastic waste in road construction. In 3 Policy Circular no. 18.36/2019 using plastic waste in road construc- 2019, the United Kingdom government (Amendment to use of waste tion in every state in India. Addition- announced a £23 million investment plastic in hot bituminous mixes ally, the Ministry of Rural Development into pilot projects using plastic waste in IRC:SP: 98-2018). Adopted has called for rural connectivity in the in road construction in eight locales in 2020, the National Highway Pradhan Mantri Gram Sadak Yojana na- (Sasidharan, Torbaghan, and Burrow Authority of India (NHAI) notes tionwide plan. KPMG (2021) notes that 2019).20 This investment also aims to that “Bituminous Mix in the plastic the government has encouraged the create guidance documents and spec- waste will be the default mode of use of plastic waste in road construc- ifications on the use of plastic waste construction in wearing course of tion without incentives and that the re- in road construction (Sasidharan, Tor- all service roads to be constructed quired approvals take over 60 days to baghan, and Burrow 2019). by NHAI in all future projects.” begin a project. India appears to have the great- The Ministry of Housing and Urba n est concentration and experience Affairs of the Government of India using plastic waste in road con- has encouraged the construction struction (Sasidharan, Torbaghan, of roads using plastic waste in the and Burrow 2019) . To our knowl- Plastic Waste Management adviso- edge, the ‘Guidelines for the Use of ry report issued in March 2019. Ad- Waste Plastic in Hot Bituminous Mix- ditionally, the Government of India es (Dry Process) in Wearing Course’ has recently announced the ‘Plastic by the Indian Roads Congress (IRC: 20 Buckinghamshire, Bedfordshire, Cumbria, Staffordshire, Kent, Reading, Suffolk, Solihull, and Birmingham Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 43 Engineering performance It is important to study the engineering However, researchers have begun to ap- • Impact of use of plastic waste in var- performance of plastic roads to ensure ply these tests to plastic roads though ious types of asphalt layers under a that roads remain intact and safe for evidence on whether these tests are ful- range of environmental conditions, various traffic volumes over time and ly applicable to plastic roads is lacking • Methods to prevent leaching by de- throughout a range of climatic condi- (Willis, Yin, and Moraes 2020). sign of appropriate cross-sections, tions. Bitumen modified with virgin poly- Enhanced rutting resistance has • Development of standard tests to mers often increase fatigue cracking and been noted in laboratory studies eval- assess leaching, and rutting resistance (but not necessarily uating plastic waste modified bitumen • Long-term monitoring by research cracking resistance) (Fernandes, Silva, (Table 4). Enhancing rutting resistance teams. and Oliveira 2019). In general, bitumen often decreases cracking resistance. modified with plastic waste is thought to Background on laboratory binder charac- Further research in laboratory mix- behave similarly (Fernandes, Silva, and terization and laboratory mixture charac- ture characterization was noted by Oliveira 2019). Since the use of plastic terization is provided in Annexes I and J. (Willis, Yin, and Moraes 2020) in the waste in road construction is a relatively Regarding the laboratory binder following areas: new idea that emerged within the last few characterization (Willis, Yin, and Mo- decades, most of the engineering perfor- raes 2020) the following key gaps on • Fatigue and cracking resistance, es- mance data that is known is from the lab- binder containing recycled plastics pecially of long-term aged samples, oratory instead of the field (Sasidharan, must be noted: since existing studies expect plastic Torbaghan, and Burrow 2019). roads to have better rutting resis- Two broad categories of laboratory • Phase separation mitigation, tance which often has tradeoffs relat- tests are conducted to verify that roads • Fatigue and cracking resistance, ed to fatigue and cracking resistance; are engineered properly: (1) the labo- • Applicability of standard asphalt • Quantification of structural design ratory binder characterization and (2) binder tests, benefits to verify studies that show laboratory mixture characterization. • Compatibility with additives, and that the asphalt thickness could As the name implies, laboratory binder • Need for new solvent and testing decrease due to increased mixture characterization evaluates asphalt bind- technologies. stiffness; and er without the aggregate while the labo- • When using the dry process, re- ratory mixture characterization evaluates There are also further key gaps to be searchers have not yet quantified if both the asphalt binder and the aggre- addressed: the plastic waste is evenly dispersed gate. Laboratory binder and mixture throughout the asphalt mixture. characterization tests have been devel- • Impact of use of plastic waste on oped for conventional asphalt pavement highways with heavy pavements without the use of recycled plastic waste. and high traffic loads, 44 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Table 4. Results of sample engineering performance studies. Material studied Primary findings or reports Source 12% HDPE (by weight of bitumen) increases mixture stability, reduces mixture density, HDPE and LDPE modified bitumen Review by Aziz et al. (2015) and slightly increases air voids and voids in mineral aggregate Increased the bitumen melting point, flex- Plastic waste21 modified bitumen ibility, rainwater tolerance, UV resistance, Review by Gopinath et al. (2020) longevity, stiffness 4–6% and 8% by weight of bitumen in- creased in Marshall stability, Marshall quo- Review by Rahman, Mohajerani, HDPE modified bitumen tient, flow, resistance to permanent defor- and Giustozzi (2020) mation 3–6% by weight of bitumen increased the viscosity, softening point, and penetration in- Linear LDPE modified bitumen dex; decreased penetration value; improved Nizamuddin et al. (2020) elasticity (resistance against permanent de- formation at high temperatures) 5–10% by weight of bitumen improves pave- ment stability, strength, and fatigue life as Review by Sasidharan, Torbaghan, Plastic waste in road construction well as resistance to deformation and water and Burrow (2019) damage 21 Gopinath et al. (2020) also discuss PVC, HDPE, PET, and PE, but for the sake of brevity, just plastic waste broadly is presented in the table. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 45 Economic analysis Our analysis found at least five sci- plastic waste in road construction in- Two studies analyzed the cost of us- entific articles and one report pre- creased costs by US$0.14 per square ing recycled plastic waste, primarily pared for the World Bank reporting meter of road, compared to conven- polyethylene,22 in road construction. on the costs of plastic roads; only tional roads. This result was also found The size of the road was similar in both four of these provided cost figures. by the Government of India’s Minis- studies.23 The cost of plastic waste used We added to the literature on the try of Railways (2019). Gopinath et al. for road construction and materials/ costs of plastic roads by conducting (2020) summarized that plastic waste processes related to the rest of plas- a CEA of plastic roads and found that in road construction saved US$539.07 tic road construction can be found plastic roads are economically justi- per kilometer of road, though further in Table 5 and 6. For consistency, the fiable (Annex K). All of the scientific details are not provided. Krishnamoor- original values were calculated from articles in our sample of the peer-re- thy et al. (2016) did not analyze costs their original currency (Indian Rupees viewed literature that reported on but did report cost savings as a mo- for Khurshid et al. 2013 and Euros for costs estimated cost savings (Khur- tivation for studying the engineering Lastra-Gonzalez et al. 2021) to United shid et al. 2013; Lastra-Gonzalez et al. performance of tire rubber and poly- States dollars (US$).24 2021). The KPMG (2021) report pre- propylene bottles in concrete material pared for the World Bank found that for road construction. 22 The specific plastic types studied include HDPE from plastic bottles (8 percent of bitumen), PE obtained from copper cables (Pe-Cu) (25 percent weight of bitumen), and flexible PE packaging from the yellow container (film) (25 percent weight of bitumen) (Khurshid et al. 2013; Lastra-Gonzalez et al. 2021). 23 About 3.7 m in width and 1 km in length in Khurshid et al. (2013) and 3.5 m in width by 1 km in length in Lastra-Gonzalez et al. (2021). Lastra-Gonzalez et al. (2021) also specified the thickness of the road: a wearing layer (4 cm), binder layer (10 cm), and base layer (10 cm). 24 This currency equivalent calculation was made on June 8, 2021 using a currency equivalency calculator by Morningstar for Currency and Coinbase for Cryptocurrency. 46 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Table 5. Plastic waste costs for plastic road construction. Costs (US$/ Scientific paper Plastic waste Included in cost Source ton) associated Estimated by surveying Plastic waste processing, HDPE from plastic agencies involved in recy- 499 collection, cleaning, and Khurshid et al. 2013 bottles cling and municipal waste shredding costs management in India Agency costs during material PE from copper Lastra-Gonzalez et 49 construction, maintenance, Provided by source cables al. 2021 and end-of-life stages Flexible PE packag- Agency costs during material Lastra-Gonzalez et ing from the yellow 365 construction, maintenance, Estimated al. 2021 container and end-of-life stages Cost range depends on the Provided by a local compa- (Vila-Cortavitarte et Polystyrene waste 477–656 processes needed25 ny in Spain in the year 2015 al. 2018) Table 6. Cost of non-plastic materials and related processes for plastic road construction. Material/process Costs (US$/ton) Source Plastic shredding plant 13,333.33-20,00026 KPMG 2021 de Fomento 2016 in Lastra-Gonzalez et al. 536–547 2021; Vila-Cortavitarte et al. 2018 Bitumen 670 Sasidharan, Torbaghan, and Burrow 2019 Limestone aggregate 8–9 Lastra-Gonzalez et al. 2021; Vila-Cortavitarte et al. 2018 Ophitic aggregates 19–23 Filler 50 Construction 6 CYPE Ingenieros 2019 in Lastra-Gonzalez et Milling 36 al. 2021 Transportation US$0.12/(ton*km) 25 Plastic that is lacking impurities only needs to be mechanically ground and will be on the lower end of the cost range. Other plastics that need to have impurities removed as well as use of a pelletizing machine to create smaller particles will have a higher cost. In this scenario, plastic is heated and then passed through a hole to create strands that are cut into smaller sizes (Villa-Cortavitarte et al. 2018). 26 Excludes land costs. Approximately 1–1.5 acres would be needed. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 47 Plastic shredding centers can gen- erate an additional revenue of In- dian Rupee 6 per kg of otherwise non-recyclable plastics used in road construction, creating an additional income of Indian Rupees 1,500–2,000 per month per sanitary worker at the center (KPMG 2021). Employment ben- efits for waste pickers and entrepre- neurs may be seen (KPMG 2021). Khurshid et al. (2013) calculat- ed that about US$1,936.49 would be saved per kilometer of road lane us- ing HDPE in road construction at 8 percent by weight of bitumen,27 in comparison to conventional road con- struction. Lastra-Gonzalez et al. (2021) conducted a life cycle cost analysis and found that certain plastic waste types used in road construction had cost sav- ings when the durability of the plastic road mixture does not decrease below a certain amount (in the case 6.3 per- cent). Estimates by Lastra-Gonzalez et al. (2021) consider the service life of the road through traffic modeling and sim- ulation using the software packages Al- ize and 3-4 Move (Lastra-Gonzalez et al. 2021). This simulation assumed only cracking (fatigue failure) would oc- cur since Lastra-Gonzalez et al. (2021) found that rutting was unlikely giv- en their laboratory test results. In the modeling simulation, a single axle dual tire28 was used and an annual average daily traffic of 1400 vehicles with 2 per- cent traffic growth was simulated. A report generated by KPMG for the World Bank assesses the scores of business models viability. In this 27 Unspecified whether rural or urban. 28 The assumptions behind the tire are that the tire has pressure of 900 kPa, load of 32 KN, radius of 0.106 m and center-to-center tire spacing of 0.3192 m (Lastra-Gonzalez et al. 2021). 48 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia report, KPMG conducted a material plastic cutlery alternatives, followed by et al. 2015), partially substituting bitu- flow analysis and cost-benefit analy- SLRM. Plastic roads and co-processing men with plastic waste, which is plen- sis to determine the scalability of plas- in cement kilns had equal scores and tiful, will save costs upfront. However, tic waste business models at various followed SLRM. PET bottles to textiles given that the incorporation of plas- sites29 in India. The business models had the lowest score. Despite plas- tic waste can have a ripple effects in evaluated were plastic road construc- tic roads not receiving the top score, terms of cost, further cost-benefit or tion, solid liquid resource management KPMG (2021) recommends partner- other economic analyses considering (SLRM), Areca palm sheaths as plastic ing with local governments and the all the risk factors are greatly need- cutlery alternatives, co-processing in informal waste sector to promote this ed. Examples of additional costs in- cement kiln (plastic to fuel), and PET business model due to increased road clude the price of new manufacturing bottles to textiles (KPMG 2021). This performance, such as better resistance and storage equipment and processes analysis found that plastic road con- to water as well as widespread accep- and changes in long-term upkeep. Eco- struction (bitumen modification) in- tance and government support in India. nomic analyses, such as a cost-bene- creased the cost of roads by US$0.14 Few studies have analyzed the fit analysis, on the costs to construct a per square meter of road (KPMG 2021), cost to use plastic waste in road con- plastic road in comparison to a conven- as was also found by the Government struction. This knowledge gap may re- tional road, appears to be a knowledge of India’s Ministry of Railways (2019), flect the idea that since bitumen is a gap that would help to advance an evi- in contrast to the scientific articles. by-product of crude petroleum (Va- dence-based agenda for plastic roads. The top business models according to sudevan et al. 2012), which has gener- KPMG (2021) is Areca palm sheaths as ally increased in price over time (Aziz 29 These sites include Pulicat Lake, Gulf of Khambhat, and Vembanad Lake, spread across the states of Gujarat, Kerala, Tamil Nadu, and Andhra Pradesh (KPMG 2021). Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 49 6 We suggest that further research is needed to fill major gaps in our knowledge base of plastic roads. Op- portunities for close monitoring and further research may be found in coun- Way Forward tries that are already piloting or using short-term recommendations will pro- vide necessary prerequisites and input into if and how the long-term recom- mendations should be pursued. These recommendations are specific to the use of plastic waste in road construc- tion using the dry process, but we also recommend that researchers investi- gate alternative applications and treat- ment methods of plastic waste. plastic roads. The recommendations provided are organized by short- and long-term recommendations for fur- ther research. The achievement of the 50 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Short-term research 2 Environmental issues: We have including how different plastic highlighted three topics with waste melting temperatures and We recommend that short-term re- research gaps that will inform road construction methods may search be conducted before moving the environmental sustainability or may not affect the leaching of on to long-term research. Based on of this technology: microplastics, plastic additives. the short-term research results, inter- additive leaching, and • (2c) Recyclability at the end of ested stakeholders should determine if recyclability at the end of life. life: Research on the recyclability long-term research should be conduct- of plastic roads at the end of life ed or if resources should be allocated • (2a) Microplastics: Although con- is greatly needed. It is not known elsewhere. We recommend that an in- ventional roads and tire wear are whether the plastic waste in roads terdisciplinary team of experts in plas- known contributors to global mi- or the entire plastic road can be tic waste applications, environmental croplastic pollution, we could not recycled. Conventional asphalt and occupation health, and pavement identify a study regarding the pavements are highly recyclable technology spanning private entities, generation of microplastics and so care should be taken to make public-private partnerships, and gov- nanoplastics, specifically from the plastic roads as recyclable as ernments conduct further research to plastic roads and tire wear. Mi- the conventional roads. If plas- fill the following gaps: croplastics generated from tire tic roads cannot be recycled, fur- and plastic road wear should be a ther environmental considerations 1 Technology feasibility: A gap part of the ongoing plastic roads will be needed around the poten- exists regarding the quality research agenda. tial burying of plastic in layers of assurance and control of the • (2b) Additive leaching: Addi- road over time. The following fac- use of plastic waste in road tives leach out of plastics since tors should also be considered: construction. It is not known they are not molecularly bond- the adhesion of asphalt to plastic if plastic roads increase ed to the polymer. Researchers which can complicate recycling road cracking compared to should evaluate additive leaching and the disposal of materials gen- conventional roads. Further from plastic waste used in roads. erated during road construction studies should inform We did not identify studies quan- and repairs. engineering performance tifying the leaching of organic and include the following additives from plastic roads. Mul- parameters: “unevenness, skid tiple interviewees reported forth- number, texture (depth), field coming studies. We identified two density, rebound deflection, and studies on the leaching of metal- surface condition survey through lic additives from plastic roads. tracking of the number of Further research should be con- potholes, cracking, deformation ducted on organic and inorgan- and edge flaws” (KPMG 2021). ic additive leaching from roads, Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 51 Long-term research with bitumen suppliers, interest- hazardous air pollutants. ed stakeholders should deter- Interviews and partnerships If the aforementioned research gaps mine if plastic waste can be used with equipment manufacturers are filled, we recommend that inter- in base and subbase courses of will allow operational retrofits ested stakeholders conduct further pavements to increase the per- at the plant to be researched long-term applied research in a field centage of plastic waste used. and costs to be estimated. setting and/or through conducting Furthermore, interested stake- Interested stakeholders pilot projects. We expect that a stock- holders should evaluate the qual- should consider generating taking of performance monitoring re- ity of plastic supply, plastic waste occupational health guidelines. sults from existing plastic roads pilot capture, and regional plastic projects will be helpful. Field research waste collection rates to evalu- 4 Economic viability: Cost- and pilot projects should only be pur- ate if plastic roads can be scaled benefit analyses that compare sued if the results of the short-term re- up in a given geographic area. plastic roads to conventional search suggest that plastic roads are a Long-term performance studies roads should be conducted to viable option that is protective of envi- should also inform the scalability sharpen current findings. The ronmental and human health. of this technology. CEA conducted as a part of If supported by the short-term re- this study and reports in the search, we recommend conducting 2 Environmental: Further research scientific literature generally long-term research and pilot projects is needed on the benefits and report cost savings. However, to fill the following gaps: downsides of plastic roads, as cost-benefit analyses by compared to conventional roads, KPMG and results from the 1 Technology feasibility: Field from a life cycle perspective. Government of India’s Ministry simulated research studies Most of the life cycle analyses of Railways (2019) indicated that and pilot projects will aid in identified in this study were plastic roads are $0.14 USD per accelerating the scientific conducted on plastic roads square meter of the road more understanding of long-term in high-income countries. We expensive than conventional plastic road performance. These suggest that further research roads (KPMG, 2021). Detailed studies should be conducted evaluate plastic roads from a cost-benefit analyses that are under a range of environmental life cycle perspective, including ground-truthed with data from conditions, including under greenhouse gas emissions, in the field, including the life span flooding conditions, sunlight, lower-income settings. of plastic roads, will help sort out high-pressure, and extreme conflicting reports. events, such as fires, chemical 3 Occupational health: Further spills, and other environmental occupational health guidelines 5 Industry standards: We accidents or natural disasters. and trainings are needed. recommend that industry These long-term studies should Fires may occur if recycled standards be developed to determine road moisture plastics contact the burner ensure the asphalt mix’s susceptibility, road wear, filtrate flame or clog the filter bags at consistency. Industry standards management, and engineering the asphalt plant (Willis, Yin, should specify the amount and performance, including factors and Moraes 2020). Heating types of asphalt and plastic such as rutting, cracking of plastic waste can generate waste incorporated into plastic resistance, progression of hazardous air pollutants, roads. Standardized tests should deflection and roughness, and such as volatile organic be developed to ensure the oxidation. compounds (Willis, Yin, and proper inputs and methods are Moraes 2020). We expect that used to construct plastic roads. Further research is needed to guidelines can be developed determine the scalability of to protect occupational health Since plastic additives range this technology. In partnership from generating and inhaling and can include over 10,000 ad- 52 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia ditives, at least 2,400 of which have known toxicological issues (Wiesinger, Wang, and Hellweg 2021), further work should be conducted to standardize the additives used in plastics. Stan- dardizing plastic additives will aid in researchers’ understanding of the quantities and chemical com- pounds that are leaching. Ad- vancements in the standardization of additives in plastic will aid in us- ing plastic waste as an input into plastic roads and other materials. Ultimately, plastic production and sub- sequent waste generation need to be reduced via a ‘full life cycle approach’ as noted in the upcoming international legally-binding treaty to reduce plas- tic pollution. The use of plastic waste in road construction is an emerging ap- proach to utilize plastic waste as a par- tial substitute for bitumen. This new technology is a downstream measure, addressing plastic pollution after it has already become waste. 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Airey. cation and Extension of Bituminous Binder for Asphalt.” 2020. “Experimental Exploration of Influence of Recycled Eighteenth Annual International Conference on Pavement Polymer Components on Rutting Resistance and Fatigue Engineering, Asphalt Technology and Infrastructure, Liv- Behavior of Asphalt Mixtures.” 32: 04020129. https://doi. erpool, England, United Kingdom, February 27–28. org/10.1061/(ASCE)MT.1943-5533.0003140 White, G., 2020. “A Synthesis on the Effects of Two Commer- cial Recycled Plastics on the Properties of Bitumen and Asphalt.” 12: 8594. https://doi.org/10.3390/su12208594 White, T. D., National Cooperative Highway Research Pro- gram, American Association of State Highway and Trans- portation Officials, National Research Council (U.S.), eds. 2002. . Washington, D.C.: National Academy Press. 62 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Annex A. Methods We met with Duke University and c. Who are the major companies imple- by whom. We used the search strings World Bank librarians to craft search menting plastic roads and where have in Table 7 to extract relevant articles in strings that will help us to answer the plastic roads been implemented? each database. The databases have dif- following research questions: d. What is the regulatory landscape ferent search functions, so the search surrounding plastic roads? strings were adjusted for each data- a. What is plastic waste-to-road tech- base. In the ABI Inform search string,“- nology? We reviewed the business news da- su (road)” indicated that the subject b. What are the environmental and tabases, Abstracted Business Infor- of the article is the road. In Dow Jones economic benefits and downsides mation (ABI) Inform and Dow Jones Factiva, “w/3” only returned results of implementing plastic roads? Factiva, to find out where plastic that have the search terms within three roads have been implemented and words of one another. Table 7. Search strings used to identify those who are building plastic roads and geographic locations constructed or planned plastic roads Databases Search strings Number of returns ABI Inform su (road) AND recycled AND plastic AND project 318 (plastic or polyethylene or polymer) w/3 (road or pave- Dow Jones Factiva 181 ment or asphalt or bitum*) and (waste OR recycl*) ((environment* sustainabil* AND plastic) OR microplas- World Bank Group Library tic* OR (fumes NEAR5 leach) OR plastic) AND (road OR 102 pavement OR bitum* OR highway OR thoroughfare) Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 63 Article cutoffs were established before tic road. In some instances, only the Regarding economic and costs data, reviewing the articles. We stopped re- country was specified. For each road we recorded if a cost-benefit analy- viewing articles after 20 consecutive described, one researcher also noted sis was conducted and collected oth- articles were irrelevant or after 20 per- the status of the road at the time of ar- er costs that were reported. We also cent of returns were reviewed, which- ticle publication by selecting one of the shared any costs reported with regard ever was reached first. For the World following options: to building plastic roads in either US Bank Group Library, all results were re- dollars per ton of road, US dollars per viewed because the librarian sent over • Constructed, ton of plastic, or US dollars per km of only relevant searches. • Planned for future construction/pi- road, depending on what was report- News articles were reviewed to lot/under construction, or ed in the news article. If the cost of a determine if the use of plastic waste • Planned for future construction but conventional road (no plastic waste or rubber tires in road construction dropped. incorporated) was discussed, we re- was discussed or mentioned and if so, corded the road construction materi- predetermined data points of interest If the road was already constructed, the als described and cost in US dollars per were extracted. Articles were excluded year of the road construction was not- ton of road and/or US dollars per km if they did not mention recycling plastic ed. If provided, the length of the already of road. Any alternative mode of plas- into roads; specify that plastic waste or constructed road or the planned length tic waste management (for example, recycled plastic was used, as opposed of a plastic road to be constructed in the incineration) was noted and associat- to virgin polymer; and mention building future was indicated in kilometers. ed costs (US dollar per ton of plastic) roads from plastic waste, but just dis- We characterized the type and were noted. cussed plastic waste more broadly. We amount of plastic used to construct To identify businesses that con- collected data on the type of article title, plastic roads. One researcher select- struct plastic roads, one researcher author, publisher, and date of publica- ed one or more of the following types searched brief company descriptions tion. We identified relevant news articles of plastic item(s) (if applicable): bags, (about a paragraph long) returned based on the title of the article and full- bottles, and others—specified and un- by keywords (Table 8) searched in text review. Articles were considered rel- specified. If the article characterized the the S&P Capital IQ business data- evant if they discussed the construction plastic item or plastic waste used in road base. One researcher reviewed the or planned construction of a plastic road construction by recycling category, we returned company descriptions to in as little as one sentence. We extracted selected one or more of the following determine the company’s relevancy data on points of interest, listed below, recycling categories: PET (1), HDPE (2), to plastic roads (n=141 company de- in relevant articles. For certain points of PVC (3), LDPE (4), PP (5), PS (6), other scriptions). Companies that appeared data, we used a numbered system to or- (7), and/or unspecified (8). The amount to be a part of the plastic roads indus- ganize the data. Numbers were not used of plastic (kg) and percentage substitut- try were added to a separate database for statistical scoring. ed for bitumen or aggregate were noted. (n=9 companies). Duplicate com- The data points of interest fell into We characterized key stake- panies were not added. If it was un- the following categories: geograph- holders by recording any company, clear whether a company was a plastic ic location of the road, construction government, or developmental or- roads company (for example, compa- status of the road at the time of news ganization affiliated with construct- nies that construct roads using vir- article publication, plastic road spec- ing and/or financing the plastic road. gin plastics), company websites were ifications, company constructing the The name of the company construct- identified, if possible, and the compa- road, key stakeholders, and economic/ ing the road was recorded. The name ny’s product catalog, sustainability re- cost data. For each category of interest, of the government financing the road port, and broader descriptions were we had predetermined data extraction (if applicable), the amount financed reviewed to determine if plastic waste points, which are detailed for each cate- (US$), and the name of other relevant is used in road construction. gory in the following paragraphs. partners were noted. Lastly, the name For the geographic location(s) of of the developmental organization, the the road(s), one researcher extract- amount financed (US$), and the name ed the city and country of the plas- of other relevant partners were noted. 64 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Table 8. c. What percentage(s) of the road tal harms in projects implemented Keywords queried in brief business comprises plastic waste and in by your company or others? descriptions in Standard and Poor’s which geographic location(s)? c. What happens to plastic roads at (S&P) Capital IQ d. Where do you source your plastic the end of their life stages? waste from? Are you aware of what d. What is the cost (or range of costs) Keywords searched in would have happened to the plastic to construct plastic roads in com- S&P Capital IQ waste had it not been used in road parison to traditional roads (lacking construction? recycled polymer) or alternate plas- Plastic highway e. Are plastic roads socially accept- tic waste management schemes? Plastic pave ed or alternatively, do plastic roads • What factors may raise or lower cause stress? the cost of constructing of plas- Plastic road tic roads? Environmental and economic • Have you or others conducted a Plastic recycle roads sustainability cost-benefit analysis on the con- Plastic waste roads struction of plastic roads? If so, Please describe the environmental what were the results, or would Plastic roads businesses were com- benefits and harms from plastic waste- you be willing to share the study piled. Contact information for rep- to-road technology. with us? resentatives ranging from engineers e. What are the costs of upkeeping plas- to founders to public relations con- a. What are the greatest environmen- tic roads over time? How do these tacts were collected and one individ- tal benefits brought on by the con- costs compare to traditional road ual per company was contacted for struction of plastic roads? construction costs or alternatively, an interview lasting no longer than on • If so, are these environmental plastic waste management costs? hour. The goal of the interviews was to benefits realized by all types of ground-truth our findings from news plastic roads or only those com- Stakeholders articles and the scientific literature. In- prising certain plastic recycling terview questions are shared below. types/compositions? How do Please describe the role of your business/ these benefits compare to tradi- employer in the larger industry to us. Interview questions tional road construction or other waste management alternatives? a. How long has your company imple- By ‘plastic roads’ or ‘plastic waste-to- • If so, have you measured or mented plastic waste-to-road tech- road technology’, we are referring to the otherwise witnessed these en- nology? Do you have an estimation use of recycled plastic or plastic waste vironmental benefits in projects of how many miles of plastic roads in the construction of vehicular roads, implemented by your company your company has installed? bicycle paths, or pedestrian walkways. or others? b. Is your business responsible for the en- b. What are the greatest environmen- tire life cycle of plastic roads, such as Technology tal harms or externalities posed by procuring the plastic waste, process- plastic roads? ing it, and installing the road or one or Please describe plastic waste-to-road • If so, are these environmental more tasks in the process? Please de- technology. harms brought on by all types of scribe your business’s role in the pro- plastic roads or only those com- cess of constructing plastic roads. a. Which other primary material does prising certain plastic recycling c. Where (which country, no need to plastic substitute for in road con- types/compositions? How do specify exact locations) does your struction? these harms compare to tradi- business or your contractor con- b. Which plastic recycling categories tional road construction or other struct plastic roads? are primarily used to construct plas- waste management alternatives? • What is the existing legal frame- tic roads? • If so, have you measured or other- work for construction of plastic wise witnessed these environmen- roads in that location? Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 65 • Does this legal framework hin- the report. Depending on the interview- ed iteratively by reviewing the title, key- der or support the construction ee(s) preference, some interviews were words, abstract of scientific articles, and of plastic roads? recorded for note-taking purposes only. one piece of gray literature that appeared d. Regarding the financing of private We conducted a search in Web of highly relevant to our search questions: roads, have you worked with any Science to find peer-reviewed articles (Aziz et al. 2015; Biswas, Goel, and Pot- major development organizations? that help us answer (1) what is plas- nis 2020; Fernandes, Silva, and Oliveira • If so, which organizations? tic waste-to-road technology and (2) 2019b; Gopinath et al. 2020; Limantara et • If so, which geographic locations what are the environmental and eco- al. 2018; Rahman, Mohajerani, and Gius- (country level)? nomic benefits and downsides of im- tozzi 2020; Sabzoi et al. 2020; Santos et al. plementing plastic roads. We searched 2021; Sasidharan, Torbaghan, and Burrow Notes were taken during interviews for the Boolean strings in Table 9 in Web of 2019; Vasudevan et al. 2012; White 2020). recordkeeping and incorporation into Science. These search strings were creat- Table 9. Web of Science search string Number of Database Boolean search strings returns TITLE: (road* OR pavement* OR concrete OR asphalt OR bitum*) AND TOPIC: (poly- mer* OR plastic* OR polyethylene) AND TOPIC: (waste OR recycl* OR bottles OR Web of Science 520 “alternative materials” ) AND TOPIC: “toxic* OR gas* OR metal* OR chemical* OR de- teriorate* OR distress OR leach* OR ecotoxicity OR health OR ozone OR “life cycle:) Articles were sorted by relevance, and house gas emissions, microplastic • Primary data (yes/no), before reviewing, we developed cutoff leakage, and/or leaching of additives • LCA database used, criteria. We stopped reviewing when (1) from or during the construction of • Functional/declared unit, either after 20 consecutive irrelevant ar- plastic roads. For each of these cate- • Plastic type(s), ticles (as determined by screening the ab- gories, one researcher noted if the con- • Wet/dry process of plastic road stract and title) or (2) after 20 percent of cern was discussed (or mentioned as construction, the articles were screened, whichever was little as in one line) or not. If the con- • Percentage of bitumen replaced, reached first. Article titles and abstracts cern was noted, the amount and type • Impact assessment, and were reviewed for a reference to the use of each pollutant was noted. For exam- • Impact categories. of plastic waste in roads and if present, ple, for fumes, the amount and types the articles underwent full text screening. of fumes produced would be recorded. These data points help us compare and Scientific articles were excluded based on For microplastics, only the amount of contrast the LCA studies reviewed as a the same criteria used for news articles. microplastics produced would be not- part of this study. Each article was reviewed to deter- ed. An ‘other’ category was created to Engineering performance studies mine if it was peer-reviewed, a review note other environmental concerns and from Web of Science were reviewed article, or other. We reviewed included reported from plastic roads that did not to provide an overview of the types of articles to extract data on environmen- fall into the previous categories. plastic roads researched. Data were ex- tal and economic concerns and bene- We also summarized the following tracted on the following topics: the plas- fits noted below. predetermined data points from stud- tic waste type(s) being tested in asphalt The environmental concerns re- ies that conduct LCA of plastic roads: mixtures; percentage substituted for bi- viewed within this report include the tumen; and the use of Marshall Stabili- generation of noxious fumes, green- • Country of plastic road studied, ty, Superpave Performance Grading, or 66 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia both Marshall Stability and Superpave • Patent filing date, Using the free, open-access database Performance Grading. The specific • Patent publication date, of policies adopted to reduce plastic plastic types that we used as catego- • Inventor, pollution in Karasik et al. (2020) and ries were the following: PET, HDPE, PVC, • Applicant, Diana et al. (2022) (that is, the Plas- LDPE, PP, PS, Other, and/or Unspecified. • Post-consumer or postindustrial tic Policy Inventory), we searched the To review plastic roads patents, plastic waste (if specified), terms “road” and “pavement” to find one researcher searched the Boolean • Plastic type (if specified), policies adopted that encouraged the string “plastic waste AND (paving OR • PET - 1 use of plastic waste in road construc- coated OR pavements OR asphalt)” • HDPE - 2 tion. Original policy documents were re- in the World Intellectual Property Or- • PVC - 3 viewed by one researcher to determine ganization’s Patentscope database. • LDPE - 4 if the sections describing plastic pollu- Before beginning the patent database • PP - 5 tion reduction efforts referred to the use search, we set a rule that the research- • PS - 6 of plastic waste in road construction. er would review the first 20 percent of • PU The analysis by Karasik et al. (2020) patents or stop reviewing when the re- • Crumb rubber/rubber/tires and Diana et al. (2022) has an English searcher came across 20 consecutive • Other - 7 language bias and is not representative irrelevant results. Upon reviewing the • Unspecified - 8 of the global plastics policy landscape patent abstract and description, one • Percentage of bitumen comprising at the national and subnational levels so researcher extracted the following data plastic (if specified), and additional policies may exist. on any patents that incorporated waste • Hyperlink to the original patent in or recycled plastic into road construc- the Patentscope database. tion material: Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 67 Annex B. Plastic waste An overview of plastic recycling categories can be found in Table 10. Table 10. Plastic recycling categories Recycling cat- Plastics type Application/Uses Melting Point (°C) 1 egory Polyethylene Terephalate Bottles for water and soda, food packaging, food 1 >250 (PET) containers Plastic mailing envelopes, flexible pipes, plastic High Density Polyethylene 130 but can vary in 2 chairs/stools, toys and playground equipment, (HDPE) grade plastic bags shampoo bottles Pipes, electric cables, construction material, sign 3 Polyvinyl Chloride (PVC) 100–260 boards, vinyl flooring Low Density Polyethylene Trays and containers, plastic wraps, plastic bags, 4 110–120 (LDPE) juice, and milk containers Plastic hinges, piping system, plastic chairs, reus- 5 Polypropylene (PP) 160–165 able plastic containers, plastic moldings Food packaging, CD and DVD casing, disposable Glass transition at 6 Polystyrene (PS) utensils, license plate frames, foam beverage cups 100 Baby bottles, car parts, water cooler bottles, food Based on grade and 7 Other2 containers plastic type Source: Willis, Yin, and Moraes 2020. 1 When using recycled plastic as mixture modifiers for the dry process, plastics with a low melting point (for example, Linear Low Denstiy Polyeth- ylene (LLDPE), LDPE, and HDPE) were reported to be beneficial because they coat hot aggregates upon mixing. 2 Other may include Polycarbonate (PC), Polylactide (PLCA), Acrylonitrile Butadiene Styrene (ABS), nylon, fiberglass, and acrylic (Willis, Yin, and Mo- raes 2020). 68 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Table 11. Sample of plastic additives % of additive in global Plastic additive Example substances additive production Plasticizers 34 Dibutyl phthalate Brominated flame retardants with antimony as synergist and Flame retardants 13 phosphorous flame retardant Stabilizers (including heat and UV) and anti- 12 Cadmium and lead compounds oxidants Fillers 28 Metal powders, calcium carbonate, zinc oxide, and clay Impact modifiers 5 Rubbers Colorants/pigments 2 Azo-dyes, cadmium, chromium, and lead compounds Lubricants 2 Silicone oils Other (for example, 4 Arsenic compounds and organic tin compounds biocides) Source: Ebnesajjad and Morgan 2019; Geyer, Jambeck, and Law 2017; Hahladakis et al. 2018; Pritchard 2012. Plastic waste in road sumer and post-industrial plastic waste. patents used only post-industrial plastic construction Both post-consumer and post-industrial waste were incorporated into road con- waste, specifically LDPE, HDPE, Polyeth- ylene, PET, PVC, PP, ABS, polyamide, PC, struction according to patents identi- polyoxomethylene, polyester, acrylic, and We identified 76 patent applica- fied in the patent database. The specific fiberglass reinforced plastic. One patent tions and subsequent publications plastic types included LDPE, HDPE, PET, that used post-industrial waste report- for inventions incorporating plastic PVC, PU, rubber tires, PP, PS, polyolefm, ed using by-products of the plastic re- or crumb rubber waste into plastic polyamide, Polyvinyl Butyral, styrene cycling and polymer processing process, roads between 1935 and 2021. Over isoprene styrene, ethylene-vinyl acetate such as cellulose product recycle indus- time, more companies and inventors (EVA), ABS, polyesters, polyolefin wax- try waste, fibrous cellulose product pro- applied for patents that incorporated es, PS butadiene rubber, and styrene cessing industry waste, high molecular the use of plastic and crumb rubber butadiene rubber. A total of 19 patents weight polymer industry effluents, efflu- waste into road construction (Figure 6). that were filed used only post-consum- ent treatment plant sludge and natural These patents reported using er plastic waste for the following types of and synthetic polymer processing waste, post-consumer and post-industrial plastic: LDPE, HDPE, Polyethylene, PET, and related products. The remaining pat- waste in road construction. A total of 27 PP, PS, PVC, polyamide, acrylic, rubber ents did not specify the type of plastic patents were filed used both post-con- tires, and other unspecified plastics. Six waste used. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 69 Figure 6. Number of patent applications in our sample filed annually (non-cumulative) from 1935 to 2021 8 7 6 Number of patent applications 5 4 3 2 1 0 1937 1947 1957 1967 1977 1987 1997 2007 2017 Note: Patents were retrieved from the World Intellectual Property Organization’s Patentscope database using the methods described above. Multiple plastic recycling categories roads are widespread and widely ac- milling. The ‘Other’ category includes can be used in plastic road construc- cepted (Biswas, Goel, and Potnis 2020; cigarette butts comprising cellulose tion. Willis, Yin, and Moraes (2020) IRC 2013). A summary of scientific ar- acetate and the top and bottom lay- found that the wet process was most ticles (excluding review articles) using ers of unused single-use face masks frequently studied in the literature each plastic type can be found in Fig- procured during the 2019 novel coro- (n=57 documents), while the dry pro- ure 7. The ‘Rubber’ category primari- navirus (COVID-19) pandemic, which cess was studied less commonly (n=35 ly includes crumb rubber from waste has top and bottom layers made of documents). However, the dry process tires, though one scientific article stud- non-woven fabric. is used most in India where plastic ies waste nitrile rubber from sole shoe 70 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Figure 7. Number of scientific articles in our sample studying each plastic type PE PET Rubber PP Other PS 0 2 4 6 8 10 12 14 16 18 20 PE Type: HDPE LDPE PE These results are consistent with the waste (for example, ‘polymer’, ‘plastic’, The range of percentages that plas- review by Willis, Yin, and Moraes and ‘polyethylene’) as opposed to tire tic waste was studied in the scientific (2020) who found that various poly- waste, so we expect that we would find literature varies by plastic type, with ethylene plastics were studied most more articles on rubber or tires by al- a median range between 2 and 9 per- frequently followed by PET. Willis, Yin, tering the keywords used in the search- cent for plastic recycling categories and Moraes (2020) did not include rub- es. We did not find any studies using and rubber. In Table 12, the range, me- ber products in their study so PP was PVC or PU, though Willis, Yin, and Mo- dian, and mean percentage of plastic the next most common. Our search raes (2020) found 5 studies using PVC waste substituted for bitumen is shown terms focused on the use of plastic and 1 study using PU, respectively. by plastic type. Table 12. Percentages of bitumen substituted by plastic waste Average (%) Range (%) Median (%) PP 13 0 to 50 5 Rubber 11 0 to 50 9 HDPE 7 0 to 20 6 LDPE 6 2 to 15 5 Polyethylene 6 0.2 to 25 5 PET 4 0 to 30 2 PS 3 0 to 6 3 Other 1 0 to 3 0.4 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 71 Annex C. Reports from news articles The following tons of plastic per one ki- • 0.12 tons of plastic/1 km of road (1.7 • 0.48 tons of plastic/1 km of road lometer of road were reported in news tons/14 km) in Guanajuato, Mexico (2.4 tons/5 km) in Bareilly, Uttar articles for roads that have already (Alcántara 2019) Pradesh, India (Khan 2019) been constructed: • 0.5 tons of plastic /1km of road (1 • 1.3 tons of plastic/1 km of road (0.4 tons/2 km) in Guanajuato, Mexico tons/0.3 km) of road in Kavi Nagar, • 0.43 tons of plastic/1 km of road (1.7 (Anonymous 2019) India (Dev 2019) tons/4.0 km) in Guanajuato, Mexico • 0.91 tons of plastic/1 km of road (41 • 2 tons of plastic/1 km of road (0.5 (Anonymous 2019) tons/45 km) in Guwahati, India (Mi- tons/0.25 km) in Pune, India (Anon- tra 2019) ymous 2018). Annex D. Sample of Indian Roads Congress standards (IRC: SP 98-2013) “The waste plastic shall conform to the size passing 2.36 mm sieve and retained on 600 micron sieve. Dust and other impurities shall not be more than1 percent. The process is indicated in Appendix-2. An easy method to de- termine the quantity of impurity is to determine the ash content at 600°C. To ascertain the ability of plastic to mix with the binder, the melt-flow value shall be tested as per ASTM D 1238- 2010, for which the range shall be as For LDPE: 0.14-58 gm/10 min For HDPE: 0.02-9.0 gm/10 min.” 72 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Annex E. Relevant businesses The geographic locations of the plas- dropped, or (3) planned, under con- tic roads that are (1) constructed, (2) struction, or undergoing a pilot project planned for future construction, but in Figure 4 are found below in Table 13. Table 13. Geographic locations of plastic roads City Country Status of plastic road Source Planned, under construction, or (Real Estate Monitor Worldwide Hume Australia undergoing a pilot project 2018) Rayfield Avenue, Crai- Australia Constructed (Anonymous 2018a) gieburn Planned, under construction, or (News Bites - Private Companies Victoria Australia undergoing a pilot project 2020a) Shanghai China Constructed (Yeo and Tan 2021) Not specified Estonia Constructed (The Times 2019) Pons/Saint Aubin France Constructed (Gorman 2018) Planned, under construction, or Ashaiman Ghana (Sawer 2018) undergoing a pilot project Not specified Holland Constructed (Noticias Financieras, 2020) 11 states (unnamed) India Constructed (Khanna 2019) Planned, under construction, or Agra, Uttar Pradesh India (Lavania 2019a; Lavania 2019b) undergoing a pilot project Ahmedabad India Constructed (The Times of India 2019e) Bangalore India Constructed (The Times of India 2019e) Planned, under construction, or Bareilly, Uttar Pradesh India (Khan 2019) undergoing a pilot project Bareilly, Uttar Pradesh India Constructed (Khan 2019) Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 73 City Country Status of plastic road Source Planned for future construction but Bengaluru India (Chakravorty 2019) dropped Planned, under construction, or (TNN, 2019; The Times of India Bengaluru India undergoing a pilot project 2019d) City Centre II, Kolkata India Constructed (Chakraborti 2020) Planned, under construction, or Doon, Dehradun India (Jha 2019) undergoing a pilot project Planned for future construction but Doon, Dehradun India (Jha 2019) dropped Planned, under construction, or Gurgaon India (Chaman 2020) undergoing a pilot project Guwahati India Constructed (Mitra 2019) Planned, under construction, or Jamshedpur India (Chatterjee 2020) undergoing a pilot project Kavi Nagar India Constructed (Dev 2019) Planned, under construction, or Kavi Nagar India (Dev 2019) undergoing a pilot project Kazhakoottam-Muk- Planned, under construction, or kola stretch, Thiruva- India (Surya 2019) undergoing a pilot project nanthapuram Planned, under construction, or Kochi India (Nambudiri 2019) undergoing a pilot project Planned, under construction, or Kohlapur India (The Times of India 2019b) undergoing a pilot project Planned, under construction, or (Real Estate Monitor Worldwide Maharashtra India undergoing a pilot project 2017) Maharashtra India Constructed (Dutta 2019) Mukkola-Karode, Thi- Planned, under construction, or India (Surya 2019) ruvananthapuram undergoing a pilot project Planned for future construction but Mumbai India (Manju 2019) dropped Planned, under construction, or New Delhi India (Mathur 2009; Singh 2019) undergoing a pilot project Planned, under construction, or New Town, Kolkata India (Chakraborti 2020) undergoing a pilot project Planned, under construction, or (Singh 2019; The Times of India Noida India undergoing a pilot project 2019c; The Times of India 2020) 74 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia City Country Status of plastic road Source Planned, under construction, or Odisha India (Mazumdar 2018; Ramanath 2019) undergoing a pilot project Planned, under construction, or Palakkad India (Surya 2019) undergoing a pilot project Planned, under construction, or (Popular Plastics and Packaging Pune India undergoing a pilot project 2018) Pune India Constructed (Anonymous 2018c) Planned, under construction, or Sanjay Nagar India (Dev 2019) undergoing a pilot project Planned for future construction but (The Times of India 2019a; Surya Thiruvananthapuram India dropped 2019) (The Times of India 2019a; The Thiruvananthapuram India Constructed Times of India 2019f) Planned, under construction, or Thiruvananthapuram India (The Times of India 2019f) undergoing a pilot project Planned, under construction, or (New Building Materials & Construc- Uttar Pradesh India undergoing a pilot project tion World, 2020; Shah 2020; ) Planned, under construction, or Not specified Indonesia (Anonymous 2017) undergoing a pilot project Planned, under construction, or Not specified Iran (BBC Monitoring Americas 2016) undergoing a pilot project Planned, under construction, or Rome Italy (Willan 2019) undergoing a pilot project (Benzinga Newswires 2019; Alcán- Guanajuato Mexico Constructed tara 2019; Noticias Financieras 2019) Planned, under construction, or (CE Noticias Financieras 2019; Ro- Guanajuato Mexico undergoing a pilot project cha 2020) Not specified Mexico Constructed (Noticias Financieras 2020) Planned, under construction, or (Kotecki 2018; Anonymous 2018a; Zwolle Netherlands undergoing a pilot project Guardian 2015) Planned, under construction, or (Progressive Digital Media Packag- Rotterdam Netherlands undergoing a pilot project ing News 2015) Planned for future construction but San Carlos, Chiriqui Panama (Noticias Financieras 2019b) dropped Planned for future construction but Arraiján Panama (Noticias Financieras 2019b) dropped Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 75 City Country Status of plastic road Source Planned, under construction, or (Asia News Monitor 2019; Business Not specified Philippines undergoing a pilot project Mirror 2019a) Planned, under construction, or Mandaluyong Philippines (Asia News Monitor 2020) undergoing a pilot project Planned, under construction, or General Trias, Cavite Philippines (Business Mirror 2019b) undergoing a pilot project Springfield Properties, Planned, under construction, or (News Bites - Private Companies Scotland Elgin undergoing a pilot project 2020b) Planned, under construction, or (Real Estate Monitor Worldwide Kouga Municipality South Africa undergoing a pilot project 2019a) Planned, under construction, or Jeffrey’s Bay South Africa (Fullerton 2019) undergoing a pilot project Not specified South Africa Constructed (The Times 2019) Durham United Kingdom Constructed (Engelbrecht 2020) Planned, under construction, or Durham United Kingdom (Engelbrecht 2020) undergoing a pilot project Planned, under construction, or Not specified United Kingdom (Rocha 2020) undergoing a pilot project Ollerton, Nottingham- (News Bites - Private Companies United Kingdom Constructed shire 2020d) Queen Elizabeth (News Bites - Private Companies Olympic Park, Strat- United Kingdom Constructed 2019) ford, London (News Bites - Private Companies Wolverhampton United Kingdom Constructed 2020c) Planned, under construction, or (Real Estate Monitor Worldwide Carlisle, Cumbria United Kingdom undergoing a pilot project 2020) Bangor, Maine United States Constructed (Steuteville 1996) Planned, under construction, or (Dow Jones Institutional News Clare, New York United States undergoing a pilot project 2013b) Planned, under construction, or Coyote, New Mexico United States (Valenti 1995) undergoing a pilot project (TCA Regional News, 2020; Bendix Freeport, Texas United States Constructed 2019) (Dow Jones Institutional News Logan County, Ohio United States Constructed 2013a) 76 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia City Country Status of plastic road Source Los Angeles, Califor- Planned, under construction, or United States (Waste360 2019) nia undergoing a pilot project Planned, under construction, or Maine United States (Steuteville 1996) undergoing a pilot project North Yarmouth, United States Constructed (Steuteville 1996) Maine Not specified United States Constructed (Bendix 2019) Not specified United States Constructed (Noticias Financieras 2020) Planned, under construction, or Not specified United States (Shoenberger 2000) undergoing a pilot project Oroville, California United States Constructed (Kuhar 2020) Richmond, Maine United States Constructed (Steuteville 1996) Planned, under construction, or (Real Estate Monitor Worldwide Texas United States undergoing a pilot project 2019b) Planned, under construction, or York, Marine United States (Business Wire 2011) undergoing a pilot project Not specified Unknown, Africa Constructed (Noticias Financieras 2020) Planned, under construction, or Anzoategui Venezuela (BBC Monitoring Americas 2016) undergoing a pilot project Planned, under construction, or (Real Estate Monitor Worldwide Hai Phong Vietnam undergoing a pilot project 2019c) DEEP C Hai Phong II Industrial Park, Hai Vietnam Constructed (Asia News Monitor 2021) Phong By reviewing news articles and part of their larger business. These panies that have a large portfolio in businesses in the S&P Capital IQ companies can be found in Table 14. which the use of plastic waste in road database, we identified multiple We also identified the geographic lo- construction is one of a suite of prod- companies that either focus on the cation of the company headquarters ucts, we identified the geograph- use of plastic waste as their primary for those companies whose prima- ic location of at least one arm of the business (as reported by the compa- ry focus is the use of plastic waste company that focused on the use of ny) or for larger companies, as one in road construction. For those com- plastic waste in road construction. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 77 Table 14. Businesses using plastic waste in road construction identified in S&P Capital IQ database Company name Geographic location of business Advanced Asphalt Technology United States Alex Fraser Group Australia AXION International Holdings, Inc. United States DEEP C Industrial Zones Vietnam Dow Singapore Dow Mexico Mexico Dow Vietnam Company Vietnam Downer Australia GreenMantra Technologies Canada Intergen Energy Scotland Inversiones Plasticas Tpm Industrial SL Mexico JRD Infratech India KK Plastic Waste Management India KWS Netherlands MacRebur Scotland NELPLAST Ghana Limited Ghana Rourkela Steel Plant India San Miguel Corp. (SMC) Philippines TechniSoil Industrial United States TrueGrids United States Ventia Australia Vinci Construction France VolkerWessels Netherlands Wavin Netherlands 78 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Annex F. Life cycle analysis of the use of plastic waste in road construction We identified four studies in Web of • Lastra-Gonzalez et al. (2021): ener- difficult. We provide a summary of the Science that evaluated the use of re- gy consumed, atmospheric emis- overall results of these studies to share cycled plastic from an LCA perspec- sions, waste separation process, findings across different studies, not tive: Lastra-Gonzalez et al. 2021; distance travelled, diesel needed to with the goal of comparing/contrasting Santos et al. 2018, 2021; Vila-Corta- construct the road, life expectancy studies in mind, but rather to provide a vitarte et al. 2018. The following data of mixture, recyclability of mixtures, high-level overview of what is known. points were collected and can be found and material/process costs A summary of the country, primary for each study: country, primary data • Santos et al. (2018): durability of the data (yes/no), LCA database, function- (yes/no), LCA database, functional/ pavement and asphalt plant energy al/declared unit, plastic type, wet/dry declared unit, plastic type, wet/dry • Santos, et al. (2021): collection, sort- process, % bitumen replaced, impact process, % bitumen replaced, impact ing, and shredding assessment, and impact categories in assessment, and impact categories. • Vila-Cortavitarte et al. (2020): the LCA studies reviewed (Lastra-Gon- These studies are difficult to compare maintenance, lifetime expectancy, zalez et al. 2021; Santos et al. 2018, and contrast, given the differences in reclaimed asphalt pavement (RAP), 2021; Vila-Cortavitarte et al. 2018) can assumptions, scope, and inputs and recyclability, and feedstock energy. be found in Table 15. outputs between studies. Examples of the categories in which the authors This is just one example of how com- made assumptions are as follows: parison between LCA studies can be Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 79 Table 15. Summary of LCA studies reviewed Citation Lastra-Gonzalez et al. 2021 Country Spain Primary data (Yes/No) Yes LCA Database Eldan Recycling AS machinery catalogue, de Fomento, 2016, CYPE Ingenieros, 2019 Functional/declared Functional Unit: 1 km lane with a width of 3.5 m with wearing, binder, and base layers that units are 4, 10, and 10 cm thick. Plastic type Cable plastic and the film fraction from household packaging Wet/Dry Process Wet, dry Wet: 25% % bitumen replaced Dry: 25% Impact assessment ReCiPe 2016 Impact categories Economic, human health, ecosystem diversity, and resource availability Citation Santos et al. 2021 Country Australia Primary data (Yes/No) Yes LCA Database AusLCI database Declared Unit 1: provision of 1 ton of recycled plastic pallets Functional/declared Declared Unit 2: provision of the quantity of polymer-modified bitumen units Declared Unit 3: provision of the quantity of asphalt mix Plastic type LDPE, HDPE Wet/Dry Process Wet, dry Wet: 0%, 2%, 4%, 6% 8%; % bitumen replaced Dry3: 0%, 2.5%, 5%, 10% 20% Centrum voor Millikunde Leiden (CML) baseline using Best Practice Guide for Mid-Point Life Cycle Impact Assessment Impact assessment in Australia Climate change, acidification, eutrophication, ozone layer depletion, and photochemical oxi- Impact categories dation 3 Quarry aggregate replacement. 80 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Citation Santos et al. 2018 Country France Primary data (Yes/No) Yes LCA Database EcoInvent Database version 3.2 Functional/declared Functional Unit: A typical French highway section of 1 km length, composed of two inde- units pendent roadways, each with 2 lanes with an individual width of 3.5 m. Plastic type Waste nitrile rubber from shoe sole and EVA Wet/Dry Process Unspecified % bitumen replaced 2%, 5% International Reference Life Cycle Data System (ILCD) impact assessment method at mid- Impact assessment point level Climate change, freshwater and terrestrial acidification, freshwater ecotoxicity, freshwater eutrophication, ecosystem quality-ionizing radiation, marine eutrophication, terrestrial eutro- Impact categories phication, carcinogenic effects, human health-ionizing radiation, non-carcinogenic effects, ozone layer depletion, photochemical ozone creation, respiratory effects, land use, mineral, fossils, and renewables Citation Vila-Cortavitarte et al. (2020) Country Spain Primary data (Yes/No) No LCA Database GaBi Functional/declared Functional Unit: 1 km of road units Polystyrenes: Crystal Polystyrene, High Impact Polystyrene, and Polystyrene from hangers Plastic type Wet/Dry Process Dry % bitumen replaced 1%, 2% Impact assessment ReCipe 1.08 Agricultural land occupation, climate change ecosystems, climate changes humans, fossil de- pletion, freshwater ecotoxicity, freshwater eutrophication, human toxicity, ionizing radiation, Impact categories marine ecotoxicity, metal depletion, natural land transformation, ozone depletion, particulate matter (PM) formation, photochemical oxidation, terrestrial acidification, terrestrial ecotoxic- ity, and urban land occupation Note: Studies that used both primary and secondary data from an LCA database were considered to have used primary data. In this case, the LCA data- base used was also reported. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 81 Lastra-Gonzalez et al. (2021) found aggregates. For instance, replacing 5 percent waste nitrile rubber modified that, overall, the use of plastic waste 8 percent of virgin Polyethylene and bitumen, which had the highest envi- from copper cables and film from styrene-butadiene-styrene (SBS) with ronmental reductions in ozone layer household packaging to replace 25 recycled soft plastic waste using the depletion (21 percent) and lowest en- percent of bitumen in road construc- wet method led to about a 10 percent vironmental reductions in freshwater tion can achieve up to 11 percent re- and 16 percent decrease, respective- eutrophication (9 percent). ductions compared to conventional ly, in carbon dioxide (CO2) equivalent Vila-Cortavitarte et al.(2018) con- road construction. The plastic from emissions. The use of rigid recycled ducted an LCA of the use of PS waste copper cables was found to be more plastic as a substitute for quarry ag- in road construction and found that environmentally friendly than the film gregate using the dry method had less environmental benefits are expect- and was found to have environmental environmentally friendly results, show- ed to occur only when considering impact reductions between 17.2 and ing an increase of about 20 percent in enhanced road behavior. The life ex- 20.9 percent. The sustainability of the CO2-equivalent emissions. pectancy of the road is expected to in- roads was tied to the service life of Santos et al. (2018) studied the crease when PS from hangers is used the road and was also found to be less use of waste nitrile rubber from shoe in road construction (as determined by impactful if the whole pavement was sole and EVA in bitumen modification engineering performance tests con- evaluated compared to the binder only. and found that if the waste modifi- ducted in the laboratory as a part of Santos et al. (2021) found that the er improved the performance of the this study). Environmental reductions use of LDPE and HDPE waste can lead road, environmental benefits will be increased as the life extension of the to environmental reductions gener- seen no matter the type of polymer road increased. ally in all indicators in comparison or percentage used. The greatest envi- to virgin polymer and virgin quarry ronmental benefits were realized when 82 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Annex G. Asphalt mixtures tested in leaching studies The specific mixtures evaluated in both ed in this study (Fernandes, Silva, and testing, surface characterization, and studies (Fernandes, Silva, and Oliveira Oliveira 2019b). All the following sam- environmental characteristics to teach 2019a, b) include the following: ples include recycled SMA while each leaching according to EN 12457 (Fer- varies in bitumen modification: nandes, Silva, and Oliveira 2019a). This • Stone mastic asphalt (SMA) refer- standard uses spectroscopic methods ence material • Conventional bitumen B160/220 to evaluate heavy metal presence in • SMA with commercial modified bi- and 0.3 percent fibers eluate (Fernandes, Silva, and Oliveira tumen (no waste) • Bitumen modified with 15 percent 2019a). In this test, the sample is dried, • SMA with modified bitumen with 10 engine oil and 6 percent HDPE placed in a closed container with dis- percent waste motor oil and 6 per- • Bitumen modified with 15 percent tilled water, and agitated for 24 hours cent HDPE engine oil and 5 percent SBS (Fernandes, Silva, and Oliveira 2019a). • SMA with modified bitumen with 10 • Bitumen modified with 15 percent Then, the suspended solids are allowed percent waste motor oil and 5 per- engine oil and 20 percent crumb to settle and solids are filtered from liq- cent SBS rubber uids. The liquid portion (eluate) is then • SMA with modified bitumen with • Bitumen modified with 17.5 percent analyzed to quantitatively measure 7.5 percent waste motor oil and recycled engine oil bottoms and 6.0 leached heavy metals (Fernandes, Sil- 20.0 percent crumb rubber (Fer- percent HDPE va, and Oliveira 2019a). nandes, Silva, and Oliveira 2019a). • Bitumen modified with 17.5 percent The heavy metals measured in recycled engine oil bottoms and 5.0 both studies are Cadmium (Cd), Chro- Fernandes, Silva, and Oliveira (2019b) percent SBS mium (Cr), Copper (Cu), Nickel (Ni), study also evaluated the following ad- • Bitumen modified with 22.5 percent Lead (Pb), and Zinc (Zn) (Fernandes, ditional SMA mixtures: recycled engine oil bottoms and Silva, and Oliveira 2019a). The re- 20.0 crumb rubber (Fernandes, Sil- sults of Fernandes, Silva, and Oliveira • SMA with bitumen modified with 15 va, and Oliveira 2019b). (2019a) primarily indicate that leaching percent recycled engine oil bottoms of certain heavy metals is not beyond and 6 percent HDPE) Fernandes, Silva, and Oliveira (2019a) legal limits outlined in the Portuguese • SMA with bitumen modified with 15 evaluated waste HDPE (4 percent, 5 Decree-Law no. 183/2009. For Cd, Cr, percent recycled engine oil bottoms percent, and 6 percent by weight of Ni, and Pb, the samples containing and 5 percent SBS) bitumen), SBS (4 percent, 5 percent, HDPE and SBS had less than or equal • SMA with bitumen modified with 15 and 6 percent by weight of bitumen) to the same amount of each metal as percent recycled engine oil bottoms and crumb rubber (5 percent, 7.5 per- the reference material (Fernandes, Sil- and 20 percent crumb rubber. cent, 10 percent, 15 percent, and 20 va, and Oliveira 2019a). However, for percent by weight of bitumen) as bind- Cu, the bitumen modified with new Seven recycled SMA mixtures with 50 er modifiers in SMA mixtures. The mod- modified binder had higher levels of Cu percent of reclaimed asphalt pavement ified SMA mixture (binder content 5.8 than the reference material; this sam- (RAP) and plastic waste were also test- percent) then underwent mechanical ple still fell below the limits, so it is not Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 83 a concern (Fernandes, Silva, and Olivei- waste material had higher levels than ture with 10 percent engine oil and 5 ra 2019a). All values fell below the lim- control values: percent SBS had 0.49 mg per kg of Zn, its set by the Portuguese law for Zn; which was greater than one of the con- however, all mixture samples contain- 1. SMA with bitumen modified with 15 trols, control SMA with conventional bi- ing SBS, HDPE, or crumb rubber had percent recycled engine oil bottoms tumen B35/50 and 0.3 percent fibers, slightly higher levels of Zn than the new and 6 percent HDPE, and which had 0.43 mg per kg (Fernandes, modified binder (Fernandes, Silva, and 2. SMA with bitumen modified with 10 Silva, and Oliveira 2019b). Interesting- Oliveira 2019a). The sample containing percent waste engine oil and 5 per- ly, the samples that incorporated RAP SBS also had higher levels of Zn than cent SBS. had higher levels of Ni and Zn (though the reference material (Fernandes, Sil- still within the limits set by Portuguese va, and Oliveira 2019a). Zn may be a The SMA mixture with 6 percent HDPE law), potentially due to the accumula- potential concern, but since all values had higher levels of Cu (0.31 mg per tion of fuel and engine oil on the pave- fall well within the reference limit, this kg) than both control mixtures, which ment and tire and brake pad abrasion is unlikely to be a major issue for plas- lacked recycled engine oil bottoms and (Fernandes, Silva, and Oliveira 2019b). tic roads, in comparison to convention- HDPE (< 0.25 mg per kg) (Fernandes, RAP is widely used, so this may be a al roads. Silva, and Oliveira 2019b). The legal lim- future concern as RAP continues to be In Fernandes, Silva, and Olivei- it for Cu is 2 mg per kg, so the values recycled in the future. ra (2019b) two samples incorporating still fall well within legal limits. The mix- 84 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Annex H. Microplastic generation Modeling by Evangeliou et al. (2020) • 50–67 kilotons of PM10-size brake Atmospheric Deposition Network and estimated that the annual tire and wear particles. then modeled it outward. To our knowl- brake wear microplastic emissions in edge, none of the areas where prima- Asia is the following: These estimates were obtained using ry data were collected prominently use top-down estimates of total tire wear recycled plastic waste on roads (com- • 4.8–30 kilotons of PM2.5-size tire emissions based on data reported for pared to India, for example), so we can wear particles Norway, Sweden, and Germany (Evan- assume that these data likely represent • 85.0–167 kilotons of PM10-size tire geliou et al. 2020). On the other hand, the road traffic microplastic emissions wear particles Brahney et al. (2021) measured the primarily from conventional roads. • 26–62 kilotons of PM2.5-size brake deposition of microplastics in the west- wear particles ern United States through the National Annex I. Laboratory binder characterization Recycled plastic waste can be incor- signed a certain temperature at which viscosity of approximately 250 pois- porated into binder and graded ac- it should be conducted so researchers es at 60⁰C. The asphalt binder grading cording to penetration-, viscosity-, can determine the climate and traffic nomenclature shares the range of tem- and/or Superpave Performance Grad- conditions at which the binder can re- peratures at which a binder can per- ing-based measures to determine liably perform in the field. Frequently form properly. In addition to the tests binder suitability. Superpave Perfor- applied tests are provided in Table 16. shown in Table 16, laboratory bind- mance Grading is considered the most These laboratory binder characteriza- ing characterization can also evaluate modern specification system and vis- tion tests allow researchers to assign the use of recycled plastic in the bind- cosity tests are preferred over penetra- binders a ‘grade’, which corresponds to er evaluated by using softening point tion tests (Islam and Tarefder 2020). In the results of the test. For example, a and ductility tests (Willis, Yin, and Mo- the Superpave Performance Grading viscosity grade of AC-2.5 corresponds raes 2020). specification system, each test is as- to virgin asphalt cement (AC) with a Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 85 Table 16. Examples of standardized tests by the American Society for Testing and Materials (ASTM) and American Association of Highway and Transportation Officials (AASHTO) associated with laboratory binder characterization. Characterization category Example studies using these test(s) Test(s) Ahmedzade et al. 2017; Al Helo Qasim, and Abdulhussein 2020; Bary et al. 2019; Guru et al. 2014; Leng, Padhan, and Penetration Sreeram 2018; Leng et al. 2018; Padhan et al. 2020; Padhan ASTM D946 and Sreeram 2018; Sojobi, Nwobodo, and Aladegboye 2016; Ye et al. 2021 Ahmedzade et al. 2017; Cai et al. 2019; Khan et al. 2016; Pad- ASTM D 3381, AASHTO Viscosity han et al. 2020; Ye et al. 2021 M 226 Ahmedzade et al. 2017; Al Helo, Qasim, and Abdulhussein Superpave Performance 2020; Balaguera et al. 2018; Bary et al. 2019; Guru et al. 2014; Performance Grading Grading, AASHTO M Kabir et al. 2021; Khan et al. 2016; Leng, Padhan, and Sreeram 320, and AASHTO M 332 2018; Zhang et al. 2020 Source: Islam and Tarefder 2020. Synthesis of improve rutting resistance decrease be troublesome for road performance scientific literature cracking. Few studies were noted (Wil- lis, Yin, and Moraes 2020) as evaluating (Willis, Yin, and Moraes 2020). ASTM D7173 is used in part to evaluate the low-temperature cracking and fatigue. storage stability of binders (Willis, Yin, Studies evaluating plastic roads using When using the wet process, and Moraes 2020). Additionally, a test these tests consistently found that re- phase separation between the asphalt called the laboratory asphalt stability cycled plastic binders reduced pen- binder and recycled plastic was not- test was developed to test phase sep- etration and ductility and increased ed as an issue in the use of this pave- aration, which was not fully addressed the softening point, viscosity, and ment over the long term (Vasudevan in the previous Superpave Performance high-temperature performance grade et al. 2012; Willis, Yin, and Moraes Grading (Bahia et al. 2001). Research- (Willis, Yin, and Moraes 2020). It is 2020). Due to the solubility and ther- ers consistently found that phase sep- expected that recycled plastic bind- modynamics of the two materials used aration was an issue for recycled plastic ers will improve the rutting resistance to create a plastic road (that is, binder and binders; as such, multiple research- of roads, compared to conventional and recycled plastic), the materials can ers incorporated a stabilizer4 into the road construction (Willis, Yin, and Mo- separate from one another under static binder and recycled plastic blend (Wil- raes 2020). However, often factors that heated storage conditions, which can lis, Yin, and Moraes 2020). 4 Examples of potentially effective stabilizers include EVA, maleic anhydride (MA) grafted LLDPE, nanosilica, organic montmorillonite, polyphosphoric acid (PPA), reactive elastomeric terpolymer (RET), and SBS as well as low-level chlorination and maleation of Polyethylene (Willis, Yin, and Moraes 2020). 86 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Annex J. Laboratory mixture characterization Historically, rutting5 and cracking the rutting performance of roads in equate performance. Superpave spec- are the two major concerns that en- early stages, though now asphalt ifications that apply to asphalt binders gineers focused on to determine if a cracking performance is the prima- are newer than the Marshall Stabili- new asphalt mixture was fit to build ry concern (Islam and Tarefder 2020). ty Tests, applied to asphalt mixtures. a road. The use of plastic waste is However, rutting and cracking perfor- Overall, though, in more recent years, thought to improve rutting resistance mance is not a part of the standard concern when creating new asphalt but may decrease cracking resistance Superpave mixture design. Rather, Su- binder mixes has been focused on the in comparison to conventional roads. perpave only uses the tensile strength cracking of roads, instead of rutting (Is- From the late 1980s to early 1990s, the ratio test to determine if the asphalt lam and Tarefder 2020). Example tests U.S. Strategic Highway Research Pro- mixture has adequate moisture dam- for mixture properties can be found in gram created the Superpave mix de- age resistance. Therefore, relying only Table 17. sign technique, which aimed to create on the Superpave mixture design does asphalt mixes that greatly improved not ensure that plastic roads have ad- 5 Defined as the “the load-induced permanent deformation of a flexible pavement” (White et al. 2002). Table 17. Common laboratory tests and tests standards to assess asphalt mixture properties. Example studies Mixture property Laboratory test(s) Example of test standard using these test(s) Disk-Shaped Compact Tension Test ASTM D7313-13 Indirect Tensile (IDT) Test  AASHTO T 322-07  Semi-Circular Bend (SCB) Test  AASHTO TP 105-13  Thermal Stress Restrained Speci- (Fernandes, Silva, BS EN12697-4  men Test  and Oliveira 2019a; Cracking Mazouz and Mer- Disk-Shaped Compact Tension Test  ASTM D7313-13  bouh 2019; Vila-Cor- TxDOT Tex-248-F  tavitarte et al. 2018) Texas Overlay Test  NJDOT B-10  Illinois Flexibility Index Test  AASHTO TP 124-16  AASHTO TP 107-14, AASHTO TP Direct Tension Cyclic Fatigue Test  133-19 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 87 Example studies Mixture property Laboratory test(s) Example of test standard using these test(s) AASHTO T 321  Flexural Bending Beam Fatigue Test  ASTM D7460  IDT Fracture Energy Test  N/A  Illinois Flexibility Index Test  AASHTO TP 124-16  (Fernandes, Silva, LaDOTD TR 330-14  and Oliveira 2019a; SCB at Intermediate Temperature  Cracking Mazouz and Mer- bouh 2019; Vila-Cor- ASTM D8044-16  tavitarte et al. 2018) Texas Overlay Test  TxDOT Tex-248-F  Direct Tension Test  n.a  IDT Energy Ratio Test  n.a AASHTO TP 124-16, IDEAL CT ASTM Illinois Flexibility Index Test  D8225-19  Asphalt Pavement Analyzer  AASHTO T 340  Flow Number  AASHTO TP 79-15  (Khurshid et al. Rutting  Hamburg Wheel Tracking Test  AASHTO T 324  2013) Superpave Shear Tester  AASHTO T 320-07  Triaxial Stress Sweep Test  AASHTO TP 116-15  Hamburg Wheel Tracking Test  AASHTO T 324  (Al Helo, Qasim, and Moisture suscepti- Abdulhussein 2020; bility  Khurshid et al. 2013) Tensile Strength Ratio  AASHTO T 283  Source: West et al. 2018. 88 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Figure 8. Use of Marshall Stability Test and/or Superpave Performance Grading 24 % Neither Marshall nor Superpave 38 % Superpave reported 10 % Both Marshall and Superpave reported 28 % Marsall The civil engineering discipline re- Willis, Yin, and Moraes (2020) found tions were used more commonly than lated to road construction has devel- that many studies conducting labo- its predecessor, the Marshall Stability oped several laboratory tests, some of ratory mixture characterization of Test (Figure 8). In most cases, the ad- which have associated standards that plastic roads used the Marshall Sta- dition of recycled plastic to the asphalt are used to test if asphalt mixtures bility Test and/or Marshall specifica- mixture increased Marshall stability, perform suitably. These tests and stan- tions, as reported by the authors. We which, many indicated, would improve dards are widely accepted and choice did not attempt to review studies to road resistance to permanent defor- between which test to conduct varies determine if they met Marshall and/ mation (Willis, Yin, and Moraes 2020). across stakeholders and geographies. or Superpave specifications, but rath- Consensus is still building about which er relied on the reported designations tests is the ‘best’ test to conduct.6 by the authors. Of the 29 studies eval- uating the engineering performance Synthesis of of plastic roads, our study found that scientific literature most studies, 25 scientific articles in this case, used either the Marshall Sta- bility, Superpave Performance Grad- Despite the more recent use of Su- ing, or both tests/specifications. We perpave Performance Grading in- found that the Superpave Perfor- stead of the Marshall Stability Test, mance Grading and related specifica- 6 Within the United States, for example, states vary in their use of preferred rutting tests (West et al. 2018). In North Carolina, Oregon, and Arkansas, for instance, the Asphalt Pavement Analyzer (AASHTO T 340 is the current rutting test used whereas in Texas, Maine, Utah, and California, among other states, the Hamburg Wheel Tracking Test (AASHTO T 324) is currently used (West et al. 2018). Overall, most states use the Hamburg Wheel Tracking Test to test rutting followed by the AASHTO T 340. However, the less popular rutting tests, such as the Flow Number, which is currently used in Del- aware, is still accepted, just not as widely used. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 89 Annex K. Cost-Effectiveness Analysis (CEA) of Plastic Roads Plastic roads bring an interesting cir- proportion of bitumen constitute a sim- to the necessity for the construction cular economy and development-re- ple recipe for a potentially successful of more roads to connect more peo- lated option. The problems related to and scalable development solution. If ple with markets and the presence of the utilization of plastic waste persist verified financially and economically competing uses for scarce natural re- across the globe, but they are particu- and implemented through a techno- sources can increase financial expen- larly acute in East Asia and the Pacific logically standardized and transparent ditures.9 Therefore, the presence of a and South Asia Region. The notion of process, this solution could efficiently financially viable offsetting mechanism using plastic in road construction is not deliver a worthwhile investment option could potentially be of interest to the new, as this technology was patented in for developing countries, where the road construction industry in develop- 1974. Since then, the solution has been scarcity of paved and properly man- ing countries. available to the masses free of charge. aged roads is frequently intertwined Plastic roads are usually con- Its simplicity and direct applicability fa- with the mounting problem of plastic structed though two types of plastic cilitated plastic roads’ construction in waste management. utilization processes.10 The inclusion several countries worldwide: India, Sri The financial aspects of road con- of recycled plastic in road construc- Lanka, United Kingdom, Canada, or the struction are crucial from the indus- tion can generally be done through United States, to name a few.7 try point of view. For the industry, any a wet or dry process where plastic is The concept of plastic roads new solution needs to be cost-effective primarily used as a bitumen modifier seems promising, but is the econom- to be viable and scalable. But recently, (<10 percent bitumen replacement). ics convincing enough? It is expected the financial aspects of road construc- The dry and wet methods differ slight- that plastic utilization in road construc- tion are becoming more intertwined ly, with the dry process being gener- tion can help manage plastic waste and with the economic aspects as road ally considered a preferred option, prevent its negative impact on the en- paving is energy demanding and uses especially in the context of developing vironment. Combining the circular scarce natural resources.8 Traditional countries where optimal monitoring economy narrative with the alleged road building can negatively influence of processes can be hard. Further- longer life-span for plastic roads and the environment and bring econom- more, the Indian Road Congress has more extended durability for mainte- ic costs that generally should be ac- already set the dry process standards nance with similar or better road per- counted for from the point of view of that might constitute a practical ref- formance tests and allegedly cheaper the entire society. At the same time, a erence point for other countries in the inputs with recycled plastic replacing a rise in the use of natural resources due region. Consequently, the dry process 7 The original patent has been adjusted for the specific needs of different countries and various companies that specialize in this technology. Also, to various extents, both dry and wet processes have been employed. 8 The volume of fuel used to transport aggregates and other materials necessary for road construction and the energy used to power road machinery and equipment is significant. These factors add to the economic costs of road construction through emissions and natural resource depletion. 9 Because the growth in demand for natural resources due to a growing demand for roads and competing uses for scarce resources can increase the prices of these inputs adding to the financial costs of road construction. 10 These processes are described in more detail in the text of this report, specifically in Table 2 and the following text. 90 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia of plastic utilization in road construc- in traffic volume and type, change in Modeling tion is being considered in the follow- ing analysis. travel times and the onset of accidents, change in fuel usage or maintenance Assumptions The rigorous economic analyses of vehicles, and similar parameters. In of plastic roads are virtually non-ex- this report, as a second-best option, a A set of the essential modeling as- istent. The results of a few quanti- CEA, is employed instead. The CEA is sumptions used in the modeling pro- tative studies that are available in pursued using more general assump- cess is presented in Table 18. These peer-reviewed publications frequently tions by considering the construction assumptions were necessary to set up contain outdated data, show a scarci- of a plastic road and applying a dry an ‘existing scenario’ (business-as-usu- ty of financial and economic variables, plastic utilization process in India’s al scenario’) and ‘intervention scenar- present unclear and hard to trace data context.12 The standard CEA allows io’ that could be directly compared in sources or unconvincing methodolog- the estimation of economic benefits the CEA to deliver initial conclusions re- ical approaches. Furthermore, the re- in the number of units produced when garding the cost-effectiveness of both sults of these economic analyses can intervention is put in place instead of road types. even be contradictory.11 including direct valuation of these ben- efits. The goal of the CEA is to find out Methodology if investing in plastic roads could po- tentially produce higher benefits to the The CEA is pursued to verify the whole society and higher gain per unit economics of plastic roads. The eco- of expenditure than the construction nomic analysis pursued in this re- of standard bitumen roads. The effec- port has modest aspirations that are tiveness ratio of the road construction bound by a general lack of the neces- costs-to-benefits is measured using sary data, especially on the benefits the utility of 1 km of constructed road. side. The persistent lack of informa- The following cost-effectiveness ratio tion about potential changes in ben- is being used: efits between standard bitumen roads and plastic roads prohibits the use of a classic cost-benefit analysis PV of Costsi CE i (CBA), which would typically consti- = tute the preferred methodological ap- PV of Effectivenessi proach in this case. To set up a CBA properly, we would need to compare Where: ‘business-as-usual scenario’ and ‘in- CEi = Cost effectiveness ratio tervention scenario’ in the case of a PV of Costsi = Present Value of all costs mea- specific road in a particular location. sured at economic resource level. This would allow the quantification of PV of Effectivenessi = Effectiveness measured potential changes in benefits: change per 1 km of constructed road. 11 While most reports that include some economic analysis state that plastic roads are more economical (for example, Vasudevan et al. 2012), others claim that they are, in fact, more expensive than standard roads (for example, KPMG 2021 report). There might be several issues associated with these differences in economic results, and these elements can have individual or combined effects: (1) various reports might have different assump- tions, (2) the reports might also assess different road types in different locations, (3) the reports might analyze plastic waste use as bitumen re- placement versus bitumen modifier, (4) various types of bitumen might be considered (prices differ depending on class of bitumen and its origin) (the same might apply to costs of the aggregate), and (5) the reports might include and mix different categories of costs (for example, some finan- cial expenditures and revenues might be combined with economic costs and benefits) and so on. 12 India was chosen in this modeling exercise because it remains a pioneer in plastic roads. Also, the information regarding the construction of plastic roads in India was the most available. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 91 Table 18. Modeling assumptions Existing scenario: Intervention scenario: standard bitumen road construction plastic road construction (dry process) (a).The construction of a new/penetration road is assumed. (a).The construction of a new/penetration road is assumed. (b). No recycling of asphalt pavement is (b). No recycling of asphalt pavement is assumed. The road is constructed assumed. The road is constructed from new from new aggregate materials and bitumen+ a proportion of recycled plastic. 1. aggregate materials and bitumen. (c).The analysis assumes 1 km of road that is 3.75 m wide with thickness of 25 (c). The analysis assumes 1 km of road that is mm SDBC – 3,750 m2. 3.75 m wide with thickness of 25 mm semi- (d). Flexible pavement road is assumed. dense bituminous concrete (SDBC) -3,750 m2. (d).Flexible pavement road is assumed. (a) Standardized quality and size ready to use in the dry process plastic is pur- chased and delivered to the asphalt plant by the recycling company. The price of recycled plastic includes all costs associated with plastic recycling, cleaning, (a) The road is constructed from bitumen and and transport to the asphalt plant. aggregate. The same type of bitumen and (b) No additional costs are involved on the asphalt plant’s side (no new equip- aggregate is assumed, as is the case of the ment is needed and the same temperature is required for the bitumen-plastic 2. plastic road. mix as for the standard bitumen mix). Plastic is mixed with heated aggregate (at (b) The contractor in charge of laying the 140–175⁰C) and then combined with the already heated bitumen. The traditional road gets ready bitumen mix from the plant. bitumen road process differs from the dry process only when plastic is added to the heated aggregate. (c. The contractor in charge of laying the road gets ready bitumen-plastic mix from the plant.13 (a) It is assumed that aggregate and bitumen costs are the same in the case of both road types. 3. (b) Both road types require the same equipment type for laying the asphalt. The surface preparation before laying the asphalt is also assumed to be the same in the case of both road types. (a) It is assumed that 10% of bitumen in the standard road composite is mod- (a) 80/100 bitumen is assumed. For 1 km road ified with plastic. Therefore, 1.125 tons of plastic are used instead of bitumen. 4. as specified in Table 2 point (1) it is assumed The costing of bitumen is based on this distribution. Consequently, plastic road that 11.25 tons of bitumen are required. requires 10.125 tons of bitumen. (b) The plastic type assumed in dry process is LDPE.14 (a) The life of a traditional bitumen road is as- sumed at 20 years. End of life of a road is under- (a) The life of a bitumen-plastic road is assumed at 20 years. The end of life of a stood as the time when the road is abandoned road is understood as the time when the road is abandoned, and a decision will and there will be a decision made if it will be be made if the road should be reconstructed or left as is. reconstructed or left as it is. (b) Maintenance is assumed to be pursued every 7 years. Therefore, there are 2 5. (b) Maintenance is assumed to be pursued ev- maintenance activities assumed within 20 years. ery 5 years. Therefore, there are 3 maintenance Lower deterioration rate of plastic roads is assumed, based on the past re- activities assumed within 20 years. search on roads in Pune (Biswas, Goel, and Potnis 2020). (c) It is assumed that the overlay work is pur- (c) It is assumed that the overlay work is pursued in Year 10 after construction. sued in Year 10 after construction. (a) Assumed financial price per 1 ton of domestic bitumen (VG 10 (80/1000)15 = Indian rupee (INR) 36,830 per ton ex-Mumbai 6. (bulk bitumen).16 13 Source: https://e360.yale.edu/features/how-paving-with-plastic-could-make-a-dent-in-the-global-waste-problem. 14 Source: https://law.resource.org/pub/in/bis/irc/irc.gov.in.sp.098.2013.pdf. 15 This type of bitumen was used in analysis reported in Vasudevan et al. 2012. 16 Price obtained on August 16, 2021, from https://www.bitumenindia.com/. 92 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Existing scenario: Intervention scenario: standard bitumen road construction plastic road construction (dry process) (a) Assumed financial price of recycled plastic for dry process per 1 ton: INR 7. n.a. 20,000 per ton17 (per 1.125 tons = INR 22,500) (a) Assumed reduction in carbon dioxide (CO2) emissions: 3.5 tons of CO2 per 1 8. n.a. km of road (Source: Vasudevan et al. 2012). (a) Pricing of CO2 according to the World Bank’s ‘Guidance Note on Shadow Pric- 9. n.a. ing of Carbon in Economic Analysis’, dated November 12, 2017.18 (a) The potential economic costs of leaching of plastic and possible creation of various by-products (for example, gases and micro and nano plastics) are 10. n.a. ignored due to the lack of quantitative information on this topic. (b) The assumed dry process is expected to create no toxic gases due to max temperature of 180 Celsius.19 (a) Economic costs associated with road usage: traffic volume and type, the opportunity cost of travelling time, maintenance requirement for cars using the road, accidents’ rate and associated mortality rate, and so on are also ignored due to the lack of the specific location of the road and associated data (Note: unspecified road location in India is assumed in the case of both 11. road types). (b) In the evaluation of carbon release associated with both road types, only emissions associated with the road construction, maintenance, and overlay were quantified. All other emissions are ignored due to the lack of specifics as a generic type and location of Indian road is assumed.20 (a) VAT on goods is assumed to be at 18%. (b) The economic discount rate was assumed at 12%. (c) Tariffs on bitumen, aggregates, and plastic are assumed at 10%. 12. (d) Transportation and handling costs were assumed at 5%. (e) Foreign exchange premium was assumed at 1% (based on 2018 trade data). (f) No subsidies were included in calculation of conversion factors due to the lack of information on this topic. The CEA outcome is measured in kilometers of road built. In this case it is 1 km of constructed road that brings utility. One out- 13. come is assumed in this analysis due to the lack of data on other potential benefits.21 (a) It is assumed that 1 km of plastic road reduces 3.5 tons of CO2 as plastic is not burned but instead, it is used in the bitumen mix.22 Therefore, it is assumed (a) It is assumed that the emission of CO2 per that the construction of 1 km of plastic road produces 48.4-3.5 = 44.9 tons of 1 km is at 48.4 tons (construction phase) and CO2 per1 km of road. 2.71 tons of CO2 per 1 km for the maintenance (b) It is assumed that volume of carbon at maintenance is at 1.81 tons of CO2 phase (distributed equally into 3 maintenance (2.71 tons divided by 3 maintenance activities on a standard road = 0.903 tons 14. activities). of CO2. Multiplied by 2 maintenance activities in the case of plastic road = 1.81 (b) The volume of carbon emissions at the tons of CO2). These 1.81 tons of CO2 are distributed equally into 2 assumed overlay work in Year 10 after construction is maintenance activities. assumed at 50% of the original construction (c) The volume of carbon emissions at the overlay work in Year 10 after con- emissions, hence 24.2 tons of CO2. struction was assumed at 50% of the original construction emissions, hence 22.45 tons of CO2. 17 Source: Interview with Green Worms: http://greenworms.org/. Note: it was stated that this price can be further reduced in the case of steady high-volume orders. Sensitivity analysis was pursued on prices of recycled plastic (Table 20). 18 Source: https://pubdocs.worldbank.org/en/911381516303509498/2017-Shadow-Price-of-Carbon-Guidance-Note-FINAL-CLEARED.pdf. 19 Source: https://law.resource.org/pub/in/bis/irc/irc.gov.in.sp.098.2013.pdf. 20 The detailed approach to the carbon footprint estimations and data requirements can be seen in the link below. For this analysis, the emissions of 1 lane road in West Bengal were used as likely the most adequate to our road-type scenarios. https://www.adb.org/publications/methodology-esti- mating-carbon-footprint-road-projects-case-study-india. 21 Note: If additional environmental or other co-benefits could be estimated, the CEA would be replaced with cost utility analysis (CUA) as the latter allows building of an index to compare various outcomes of a proposed intervention that might have a joint impact. In this analysis, only one out- come is considered due to the lack of data, hence the CEA methodology. 22 Source: Vasudevan et al. 2012. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 93 Results percent. The results of the pursued case of the ‘existing scenario’ (busi- analysis show that the construction ness-as-usual scenario) (when 1 km The results of the CEA suggest that of plastic roads is likely cost-effective of traditional bitumen road is built). plastic roads are cost-effective. The as the present value (PV) of costs in Therefore, the use of recycled plastic CEA valuation was pursued over 20 the case of the ‘intervention scenario’ in roads construction seems to have its years to account for an assumed life (when 1 km of plastic road is construct- economic rationale. Table 19 presents of a road using a discount rate of 12 ed) is lower than the PV of costs in the more details obtained in the CEA. Table 19. CEA Results based on economic prices of 1 km of constructed road considering the lower and upper bound of CO2* pricing (in INR and US$, respectively) ** Costs of intervention Difference in PV of costs between Costs of existing sce- scenario (bitumen-plastic intervention scenario and existing nario (bitumen road) road) scenario PV in INR (consider- Costs savings in ing lower-bound CO2 INR –17,167,146 INR –16,722,975 INR –444,171 the case of plastic pricing) roads PV in US$ (consider- Costs savings in ing lower-bound CO2 US$ –156,065 US$ –152,027 US$ –4,038 the case of plastic pricing) roads PV in INR (consider- Costs savings in ing upper-bound CO2 INR –17,440,577 INR –16,975,638 INR –464,939 the case of plastic pricing) roads PV in US$ (consider- Costs savings in ing upper-bound CO2 US$ –158,551 US$ –154,324 US$ –4,227 the case of plastic pricing) roads Note: The differences in cost savings between lower and upper carbon valuation depend on CO2 annual valuation, as prescribed by the World Bank in November 2017 Shadow Pricing of carbon Guidance Note: https://pubdocs.worldbank.org/en/911381516303509498/2017-Shadow-Price-of-Carbon-Guid- ance-Note-FINAL-CLEARED.pdf. **. The results are based on economic prices (not financial prices) using construction, maintenance, and overlay costs. The costs associated with road us- age (traffic, fuel use, or maintenance of cars using each of these two roads) are excluded due to the lack of specifics about the location of the road and traffic data. Consequently, due to the lack of specifics associated with the location of the road, the costs used in this analysis do not include all the ex- penses related to the typical life cycle cost analysis of a road. The results obtained in the CEA also but they can also be financially viable fits associated with the use of recycled support the reality seen on the ground as the industry already engages in the plastic in roads construction. The CO2 in India, where actual roads that use construction of such roads. shadow prices and volumes of CO2 used recycled plastic are being constructed. The CEA includes the economic in the analysis are presented in Figure 9. Therefore, it is expected that plastic pricing of carbon. The CEA includes the roads are not only economically viable, valuation of potential carbon co-bene- 94 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Figure 9. Shadow prices of CO2 and volume of CO2 included in the CEA CO2 Volume Existing Scenario 131 128 CO2 Volume Intervention Scenario 125 122 120 Lower CO2 valuation 117 114 112 Upper CO2 valuation 109 Volume of CO2 in tons/1 km of constructed road 107 105 100 102 98 96 Shadow Price of CO2 in USD/ton 94 91 89 86 87 84 64 65 63 60 61 48,40 57 58 44,90 55 56 51 52 53 49 50 47 48 45 46 43 44 42 24,20 22,45 0,90 0,90 0,90 0,90 0,90 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2041 2042 2040 Sensitivity analysis shows robust re- pected that the location of the road construction technology (for example, sults. A simple sensitivity analysis was and particular arrangements related engineering and material/process re- pursued on the price of plastic neces- to the road construction supply chain quirements connected to the specifici- sary for the construction of the road. (for example, transport costs associat- ty of terrain and so on). The data used The cost of plastic was increased by up ed with the delivery of aggregate ma- in this analysis come from various pub- to 50 percent. The CEA results show terials, distance from the asphalt plant lished peer-reviewed resources, with the higher cost-effectiveness of plas- to road construction, terrain, availabil- many of them quoting experimental tic roads and hold when the price of ity of plastic recyclers that can pro- results, industry-specific websites, and recycled plastic increases from INR 20 vide a standardized quality product, interviews with plastic recyclers. It is per kg to INR 30 per kg. Table 20 shows the scale of road contractors, and so acknowledged that the available data more numerical details. on.) might influence the costs of road might have some measurement errors The pursued CEA acknowledges construction. Therefore, it is expected or might be relevant only in the case of some limitations. The presented CEA that the cost-effectiveness of plastic a specific road and circumstances stat- is general, is not associated with any roads might be location dependent. It ed in the publication. However, no bet- specific road in India, and holds un- might also be conditioned on road size ter information was available to pursue der the stated assumptions. It is ex- (scale of the project at hand) and road this analysis. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 95 Table 20. Recycled Plastic Price Sensitivity Analysis Currency: INR Difference in PV Difference in PV of Costs be- of Costs be- PV ‘intervention PV ‘intervention PV ‘existing PV ‘existing tween ‘existing tween ‘existing % Change in scenario’ low- scenario’ up- scenario’ low- scenario’ up- scenario’ and scenario’ and recycled plastic er-bound CO2 per-bound CO2 er-bound CO2 per-bound CO2 ‘intervention ‘intervention price pricing pricing pricing pricing scenario’, low- scenario’, up- er-bound CO2 per-bound CO2 pricing pricing [+]50% (INR –16,731,762 –16,984,425 –17,167,146 –17,440,577 –435,384 –456,152 30/kg) [+]40% (INR –16,730,005 –16,982,668 –17,167,146 –17,440,577 –437,141 –457,909 28/kg) [+]30% (INR –16,728,247 –16,980,910 –17,167,146 –17,440,577 –438,899 –459,667 26/kg) [+]20% (INR –16,726,490 –16,979,153 –17,167,146 –17,440,577 –440,656 –461,424 24/kg) [+]10% (INR –16,724,732 –16,977,395 –17,167,146 –17,440,577 –442,414 –463,182 22/kg) modeled (INR –16,722,975 –16,975,638 –17,167,146 –17,440,577 –444,171 –464,939 20/kg) Currency: US$ Difference in PV Difference in PV of Costs be- of Costs be- PV ‘intervention PV ‘intervention PV ‘existing PV ‘existing tween ‘existing tween ‘existing % Change in scenario’ low- scenario’ up- scenario’ low- scenario’ up- scenario’ and scenario’ and recycled plastic er-bound CO2 per-bound CO2 er-bound CO2 per-bound CO2 ‘intervention ‘intervention price pricing pricing pricing pricing scenario’, low- scenario’, up- er-bound CO2 per-bound CO2 pricing pricing [+]50% (INR –152,107 –154,404 –156,065 –158,551 –3,958 –4,147 30/kg) [+]40% (INR –152,091 –154,388 –156,065 –158,551 –3,974 –4,163 28/kg) [+]30% (INR –152,075 –154,372 –156,065 –158,551 –3,990 –4,179 26/kg) [+]20% (INR –152,059 –154,356 –156,065 –158,551 –4,006 –4,195 24/kg) [+]10% (INR –152,043 –154,340 –156,065 –158,551 –4,022 –4,211 22/kg) modeled (INR –152,027 –154,324 –156,065 –158,551 –4,038 –4,227 20/kg) Note: The difference in PV shows potential PV of costs savings for 1 km of constructed road when using recycled plastic instead of traditional road. These values show PV of economic costs that include CO2 valuation. 96 Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia Conclusions necessary volume of standardized and nies and where forces of demand and ready-to-use plastic that can be em- supply will set prices for recycled plas- The CEA results suggest that the use ployed in the road construction pro- tic.24 Also, bringing together the nec- of recycled plastic in road construc- cess. Second, recycled plastic must essary policies and well-monitored tion seems to be economically justifi- have competitive pricing to allow the plastic road construction quality stan- able. While the results of the CEA show financial viability of this technolog- dards seems like a condition sine qua that using recycled plastic in roads con- ical solution. Also, the location of re- non. Lastly, well-designed incentiviza- struction is likely to be a cost-efficient cycled plastic providers is essential as tion schemes might need to be creat- solution, obstacles to this technology transport costs can add to the finan- ed for the road construction industry might still exist. For example, the road cial expenditures.23 The asphalt plants and plastic recyclers to help ensure that construction industry does not ob- operate ‘in bulk’; therefore, it is likely both industries will be willing to help serve the economic prices, including that they will expect recycled plastic jointly make recycled plastic in road carbon valuation (CO2 co-benefits). In- to be delivered in bulk, at competitive construction a mainstream technology. stead, what the sector faces are finan- prices, with standardized quality, and cial prices. Therefore, it is likely that the with a high level of timing reliability. On industry must first see the financial ra- the recycling companies’ side, forward tionale for using plastic roads to fully contracting with the road construction employ this technology. Where such agency for delivery of recycled plastic financial viability is not present, but would be a possible incentive as recy- there exists a solid motivation to intro- cling companies could plan and adjust duce this solution to correct an existing their production possibilities. market failure (unused plastic waste), Recycled plastic is expected to a set of incentives could be introduced face competitive uses and multiple (for example, offsetting mechanisms markets. It is anticipated that recycling resulting in corporate tax cuts, envi- companies might face numerous mar- ronment-friendly inputs tracing, and kets for their plastic (for example, ap- geo-tagging brand building and mar- parel and clothing industry, furniture, keting mechanisms). and so on). The plastic prices are likely The ‘on-the-ground evidence’ to differ, and recyclers might prefer to seems to point to the financial viabil- cater to non-road constructing indus- ity of plastic roads as the industry is tries. The road construction industry already engaged in this activity. Since may not be the best option for recy- plastic roads are constructed in India, cling companies as it is likely to require cost savings for using recycled plastic low (bulk) prices. Recycling companies in road construction must already exist. might not have economies of scale suf- One may then question why the use of ficient to provide the road industry with recycled plastic in road construction is cheap input, especially when recycled not employed uniformly. There might plastic needs to be transported long be multiple reasons for such status distances, which will increase costs. It quo. First, to make sure that the con- is also expected that there might ex- struction of the plastic roads is feasi- ist a need to introduce an online trad- ble, there must exist a reliable plastic ing platform that will connect asphalt recycling value chain that delivers the plants with plastic recycling compa- 23 The estimated transport costs are INR 1.2–2 per 1 km assuming 8 tons of load to be transported (1 truckload). This is the minimum volume for trans- port under this pricing. 24 Based on interviews with Green Worms: http://greenworms.org/. Plastic Waste In Road Construction: A Path Worth Paving? Application of Dry Process in South Asia 97 As global plastic waste continues to grow, stakeholders are exploring new options to use plastic waste as partial substitute for raw material. The use of plastic waste as a bitumen modifier in road construction, referred to here as ‘plastic roads’, is one option being explored. We reviewed the scientific literature, news articles, and patents; conducted a cost-effectiveness analysis; and interviewed representatives from private companies and independent, scientific researchers to determine the existing knowledge gaps regarding the (1) technology feasibility, including engineering performance; (2) environmental issues; (3) occupational health; (4) economic viability; and (5) industry standards surrounding plastic roads. We found that many companies are starting to implement or pilot this technology worldwide though key gaps in engineering performance, such as cracking resistance, remain. The environmental issues reviewed also have research gaps, including the generation of hazardous air pollutants during production; microplastics and nanoplastics generation during use; and leaching of additives from plastic waste during use. Industry standards for the use of plastic waste in road construction are lacking. In addition, there is prevailing uncertainty in the economic viability of the technology. As a result of these key research gaps, the Way Forward section presents a roadmap for short-term and long-term research priorities.