Recycled Materials for Construction Applications: Plastic Products and Composites 3031148711, 9783031148712

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Luís Eduardo Pimentel Real

Recycled Materials for Construction Applications Plastic Products and Composites

Recycled Materials for Construction Applications

Luís Eduardo Pimentel Real

Recycled Materials for Construction Applications Plastic Products and Composites Keywords: Plastics; Composites; PVC; PE; PP; PU; Environmental impact; Sustainability; Recycling; Reuse; Circular economy; Construction application

Luís Eduardo Pimentel Real National Laboratory for Civil Engineering Lisbon, Portugal

ISBN 978-3-031-14871-2    ISBN 978-3-031-14872-9 (eBook) https://doi.org/10.1007/978-3-031-14872-9 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

In this work, a general approach to the recyclability of plastics and composites used in construction, with the purpose of their reuse, is provided. The various recycling technologies applicable to plastic materials, most used in civil construction, are described, indicating the difficulties inherent to these processes for the main polymers. In this context, several illustrative cases of success and examples of recent technological innovation are presented. It also addresses the issue of quality control, certification, and standardization adopted in Europe for recycled plastics. Several market data are presented, namely the production capacity for plastics and bio-based polymers, the quantities of recycled plastic and, for each type of polymer, some statistical data on recycling. The obstacles for recycled materials in the plastics market are mentioned, also referring to the variables that most influence recycling costs and the price of recycled materials. The conclusions drawn from this work are of several types. In a succinct way, they demonstrate that recycling is a fundamental resource to minimize waste and reduce environmental pollution, constituting a strategic approach to the management of waste from plastic construction products at the end of its useful life. The main challenges and future perspectives arising from the most recent developments in this area are presented. Finally, the most relevant strategic recommendations are presented in order to continue and concretize the resolution of the problem of recycling plastics and seek to achieve the objectives of the circular economy, which involves the development of a specialized market for recycling and recycled plastics, and, consequently, promote the purchase and sale operations of economic agents and interested parties (i.e., sellers, buyers, consumers, associations, recyclers, and manufacturers of production machinery) in order to also increase the recycling and recyclability of plastic waste. Lisbon, Portugal

Luís Eduardo Pimentel Real

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Introduction

The purpose of this work is to present the state of the art on the topic “recycling of plastic building materials,” comprising a synthetic market analysis, presenting the latest developments in plastics recycling technologies, and making some recommendations to optimize the success of recycling and encourage the circular economy. In Chap. 1, the problem is briefly described and the topic of plastics sustainability is addressed, covering the topic of life cycle analysis and some case studies related to plastic materials. Then, in Chap. 2, the various types of plastics and additives usually incorporated in polymers are described. Chapters 3 describes the use, in construction, of various types of plastic materials, including composites, biocomposites, and recycled plastics. Next, in Chap. 4, the entire value chain for plastic waste is described, from the collection to the introduction of recycled materials on the market, with an emphasis on separation and recycling technologies, including recycling machinery. This chapter also addresses several aspects related to the quality of recycled plastics, including influencing factors and constraints, ending with a description of the various recycling processes. Chapter 5 summarizes data statistics on the plastics, starting with the evolution of production capacity of plastic materials, followed by recycled plastics, referring economical topics like costs of recycling and prices of recyclates. In Chap. 6, the main constraints and difficulties associated with the market of recycled plastic materials are mentioned. Next, in Chap. 7, the recycling of the main plastics used in construction is described and success stories are presented regarding the recycling of each type of polymer. Finally, Chap. 8 presents the conclusions, the challenges that are expected for the future in the short and medium term, and the recommendations to guarantee the success of recycling and encourage the circular economy.

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Environmental Aspects����������������������������������������������������������������������������    1 1.1 Plastics as a Source of Pollution ������������������������������������������������������    1 1.2 Sustainability of Plastic Materials and Products������������������������������    2 1.3 Sustainability of Plastics Used in Construction��������������������������������    3 1.4 Circular Economy Recycling������������������������������������������������������������    4 1.5 Life Cycle Assessment����������������������������������������������������������������������    5 1.5.1 Generalities ��������������������������������������������������������������������������    5 1.5.2 Life Cycle-Based Sustainability Standards��������������������������    7 1.5.3 LCA Case Studies ����������������������������������������������������������������    7 1.6 Contribution of Regulations and Policies ����������������������������������������   16

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Plastic Materials and Additives��������������������������������������������������������������   19 2.1 Generalities ��������������������������������������������������������������������������������������   19 2.2 Thermoplastics����������������������������������������������������������������������������������   20 2.3 Thermosets����������������������������������������������������������������������������������������   20 2.4 Elastomers����������������������������������������������������������������������������������������   21 2.5 Polymeric Additives��������������������������������������������������������������������������   21 2.6 Ecological Plastics����������������������������������������������������������������������������   22 2.6.1 Generalities ��������������������������������������������������������������������������   22 2.6.2 Bioplastics����������������������������������������������������������������������������   23 2.6.3 Biocomposites����������������������������������������������������������������������   29 2.6.4 Recycled Plastics������������������������������������������������������������������   31

3

 Use of Polymer Materials in Construction��������������������������������������������   35 3.1 Plastics����������������������������������������������������������������������������������������������   35 3.2 Fiber-Reinforced Plastics������������������������������������������������������������������   36 3.2.1 Classification of Composites������������������������������������������������   36 3.2.2 Characteristics of Polymeric Composites ����������������������������   37 3.2.3 Application of Polymeric Composites in Construction��������   38

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3.3 Biocomposites����������������������������������������������������������������������������������   41 3.3.1 Generalities ��������������������������������������������������������������������������   41 3.3.2 Use of Biocomposites in the Construction���������������������������   42 3.4 Recycled Plastics������������������������������������������������������������������������������   44 4

Recycling��������������������������������������������������������������������������������������������������   47 4.1 Generalities ��������������������������������������������������������������������������������������   47 4.2 Classification of Recycling Processes����������������������������������������������   47 4.3 Cascading Principles for Recycling��������������������������������������������������   48 4.4 Value Chain for Plastic Waste ����������������������������������������������������������   49 4.5 Machinery for Recycling������������������������������������������������������������������   49 4.6 Collection������������������������������������������������������������������������������������������   56 4.7 Separation ����������������������������������������������������������������������������������������   60 4.7.1 Generalities ��������������������������������������������������������������������������   60 4.7.2 Wet Separating Techniques for Separating Plastics��������������   63 4.7.3 Dry Separating Techniques for Separating Plastics��������������   70 4.8 Innovations Along the Separation Process of Plastics����������������������   87 4.9 Quality of Recycled Materials����������������������������������������������������������   87 4.9.1 Objectives������������������������������������������������������������������������������   87 4.9.2 Constraints and Influencing Factors��������������������������������������   88 4.9.3 Quality Assessment. Normalization��������������������������������������   89 4.9.4 Destination of Rejected Materials����������������������������������������   91 4.10 Reprocessing ������������������������������������������������������������������������������������   92 4.11 Manufacture of Final Products����������������������������������������������������������   93 4.12 Impact of Different Recycling Processes������������������������������������������   93 4.13 Technologies for Industrial Recycling of Plastics����������������������������   94 4.13.1 Chemical Recycling��������������������������������������������������������������   94 4.13.2 Mechanical Recycling����������������������������������������������������������   96 4.13.3 Optimization of Recycling and Separation Technologies ������������������������������������������������������������������������  101

5

 Plastics Statistics: Production, Recycling, and Market Data��������������  103 5.1 Generalities ��������������������������������������������������������������������������������������  103 5.2 Production Capacity and Application Market for Plastics����������������  103 5.3 Production Capacity and Market for Biobased Polymers����������������  104 5.4 Quantities of Recycled Plastic����������������������������������������������������������  106 5.5 Costs of Recycling����������������������������������������������������������������������������  109 5.6 Prices of Recycled Plastics ��������������������������������������������������������������  110 5.7 Competitiveness of the Waste Management Sector��������������������������  113

6

 Constraints to the Application of Recycled Plastics������������������������������  115 6.1 Generalities ��������������������������������������������������������������������������������������  115 6.2 Environmental Problems Associated with Recycling ����������������������  116 6.3 Main Difficulties in the Recycling of Plastics����������������������������������  117

Contents

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 Recycling of the Main Plastics Used in Construction ��������������������������  119 7.1 PVC Recycling����������������������������������������������������������������������������������  119 7.1.1 Generalities ��������������������������������������������������������������������������  119 7.1.2 Difficulties����������������������������������������������������������������������������  121 7.1.3 Mitigation Measures ������������������������������������������������������������  123 7.1.4 Recycling Methods ��������������������������������������������������������������  123 7.1.5 PVC Recycling Statistics������������������������������������������������������  124 7.1.6 Sustainability Label��������������������������������������������������������������  125 7.2 Recycling of Polyurethane����������������������������������������������������������������  126 7.2.1 Generalities ��������������������������������������������������������������������������  126 7.2.2 Constraints Associated with PU Recycling��������������������������  126 7.2.3 Mitigation Measures ������������������������������������������������������������  126 7.2.4 Recycling Methods ��������������������������������������������������������������  126 7.2.5 PU Recycling Statistics��������������������������������������������������������  128 7.3 Recycling of Polypropylene and PPolyethylene������������������������������  129 7.3.1 Generalities ��������������������������������������������������������������������������  129 7.3.2 Recycling Methods ��������������������������������������������������������������  129 7.4 Recycling of Plastic Mixtures����������������������������������������������������������  129 7.4.1 Difficulties����������������������������������������������������������������������������  129 7.4.2 Mitigation Measures ������������������������������������������������������������  130 7.4.3 Recycling Methods ��������������������������������������������������������������  130 7.5 Recycling of Composites������������������������������������������������������������������  130 7.5.1 Generalities ��������������������������������������������������������������������������  130 7.5.2 Constraints Associated with the Recycling of Composites ����������������������������������������������������������������������  131 7.5.3 Mitigation Measures ������������������������������������������������������������  132 7.5.4 Recycling Methods ��������������������������������������������������������������  132 7.5.5 Applications of Recycled Composites����������������������������������  134 7.6 Illustrative Cases of Success ������������������������������������������������������������  135 7.6.1 Recycled PVC����������������������������������������������������������������������  135 7.6.2 Recycled PU��������������������������������������������������������������������������  138 7.6.3 Recycled Polyolefins (PP and PE)����������������������������������������  139 7.6.4 Recycled PS��������������������������������������������������������������������������  139 7.6.5 Recycling of Mixtures of Plastics ����������������������������������������  139 7.6.6 Recycling of Composites������������������������������������������������������  140 7.7 Relevant Projects, Programs, and Studies����������������������������������������  142

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Final Remarks������������������������������������������������������������������������������������������  145 8.1 Conclusions��������������������������������������������������������������������������������������  145 8.2 Challenges����������������������������������������������������������������������������������������  147 8.3 Recommendations����������������������������������������������������������������������������  148

References ��������������������������������������������������������������������������������������������������������  153 Index������������������������������������������������������������������������������������������������������������������  161

List of Figures

Fig. 3.1 Examples of typical applications for fiber-reinforced composite materials: (a) pavements and outdoor urban furniture; (b) Sheraton Hotel - Malpensa Airport, Milan, IT; (c) Camp Mackall, North Carolina, USA; (d) York, Maine, USA; (e) Severn Crossing approaches, UK; (f) Kolding, Denmark.............40 Fig. 3.2 Waste resulting from the manufacture of pipes and fittings (Whittle and Pesudovs 2007). (Copyright ©Institute of Materials, Minerals and Mining, reprinted by permission of Taylor & Francis Ltd., http://www.tandfonline.com on behalf of Institute of Materials, Minerals and Mining.).................................45 Fig. 4.1 HDPE/PP recycling line, for barrels, boxes, containers, pipes, desks, and chairs. (Image courtesy of Jiangsu G.E.T.  Recycling Technology Co., Ltd.)........................................................50 Fig. 4.2 Recycling line for waste from electrical and electronic equipment. (Image courtesy of Jiangsu G.E.T. Recycling Technology Co., Ltd.).........................................................................51 Fig. 4.3 Picking station. (Image courtesy of M6K Group)..............................51 Fig. 4.4 Magnet separator: (a) rotary magnetic drum that can be integrated into an existing conveyor belt as a machine component. (Image courtesy of STEINERT GmbH); (b) magnetic drum already mounted on a feeder belt inline. (Image courtesy of M6K Group)........................................................52 Fig. 4.5 Eddy current separator. (Image courtesy of STEINERT GmbH).......52 Fig. 4.6 Air stream separators: (a) high efficient air aspirator. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH); (b) cyclone separator. (Image courtesy of B + B Anlagenbau GmbH).............................................................53 Fig. 4.7 Dimensional separators: (a) dry densimetric separator. (Image courtesy Guidetti Recycling Systems); (b) ballistic separator. (Image courtesy of Komptech GmbH)...............................53 xiii

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List of Figures

Fig. 4.8 Guillotine shear, providing separation by cutting mill pressure, essential to separate large waste parts that have fused or meshed together. (Image courtesy of NEUE HERBOLD Maschinen u. Anlagenbau GmbH)........................................................................54 Fig. 4.9 Pipe shredders: (a) image courtesy of Wiscon Envirotech; (b) image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH.............................................................................54 Fig. 4.10 Double-shaft shredders adapted for large volume and large strength materials like WEEE, waste household, plastic containers, barrels, etc.: (a) Image courtesy of Jiangsu G.E.T. Recycling Technology Co., Ltd.; (b) Image courtesy of Wiscon Envirotech..........................................................................55 Fig. 4.11 Granulators: (a) and (b) Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH; (c) Image courtesy of Wiscon Envirotech..........................................................................55 Fig. 4.12 Pulverizer. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)....................................................56 Fig. 4.13 Zig Zag air separator. (Image courtesy of Jiangsu G.E.T.  Recycling Technology Co., Ltd.)........................................................57 Fig. 4.14 Holding silo. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)....................................................58 Fig. 4.15 Washers: (a) Pre-Wash. (Images courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH); (b) Centrifugal washer. (Image courtesy of Jiangsu G.E.T.  Recycling Technology Co., Ltd).........................................................58 Fig. 4.16 Friction Washers, for intensive cleaning of plastic flakes and separation of impurities: (a) Images courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH; (b) Image courtesy of Wiscon Envirotech...........................................................59 Fig. 4.17 Intensive cleaner. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)....................................................59 Fig. 4.18 Dewatering screw. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)....................................................60 Fig. 4.19 Screening machine. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)....................................................61 Fig. 4.20 Two perspective views of a sink float separation tank: (a) Image courtesy of Wiscon Envirotech; (b) Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH..................61 Fig. 4.21 Mechanical dryers, where the wet granulates/foil flakes will be centrifuged with high rotational speeds against sieves that are mounted at the outside, which will be cleaned continuously to prevent clogging: (a) Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH; (b) Image courtesy of Wiscon Envirotech..........................................................................62

List of Figures

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Fig. 4.22 Thermal dryer: the material flow, fed through a cyclone, will be charged with hot air to achieve vaporizing of the water and therefore a drying of the grinding stock. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)................63 Fig. 4.23 Back and front views of a color line camera. (Image courtesy of JAI A/S)..........................................................................................63 Fig. 4.24 Hyperspectral imaging camera setup as optical sensor for recycling applications. (Image courtesy of LLA Instruments, Germany. All rights reserved LLA Instruments GmbH & Co. KG Germany)......................................................................................64 Fig. 4.25 Color sorting system equipped with an RGB line scan camera and 3D detection. (Image courtesy of STEINERT GmbH)................65 Fig. 4.26 Extruder machine. (Image courtesy of EREMA Group GmbH)........65 Fig. 4.27 Pallets of PE and PVC pipes classified (Whittle and Pesudovs 2007). (Copyright ©Institute of Materials, Minerals and Mining, reprinted by permission of Taylor & Francis Ltd., http://www.tandfonline.com on behalf of Institute of Materials, Minerals and Mining.)........................................................................66 Fig. 4.28 Photo of a separation system equipped with two vertical cyclones, the left feeding an automated double big-bag packing unit and on the right side one feeding an automated buffer bunker. (Image courtesy of B + B Anlagenbau GmbH)..................................74 Fig. 4.29 NIR spectrometer DAGS (1997). (Image courtesy of Fraunhofer Institute for Chemical Technology)....................................................77 Fig. 4.30 Automated NIRS sorter, allowing to detect the chemical composition in plastics, as well as black and dark objects. (Image courtesy of STEINERT GmbH).............................................78 Fig. 4.31 Spectral records obtained by NIRS technology, showing characteristic harmonic or combination vibrations of various plastics (Wu 2020)..............................................................................78 Fig. 4.32 Average NIRS spectra of each kind of plastic (Zhu 2019).................79 Fig. 4.33 Spectral records obtained by NIRS technology, showing spectra of different plastics. (Image courtesy of LLA Instruments, Germany. All rights reserved LLA Instruments GmbH & Co. KG Germany)......................................................................................79 Fig. 4.34 Set of X-ray fluorescence devices used for separate aluminum. (Image courtesy of STEINERT GmbH).............................................82 Fig. 4.35 Line Sorting System LIBS. (Image courtesy of STEINERT GmbH)................................................................................................83 Fig. 4.36 Line containing an eddy current separator and an X-ray separator in series, regarding the separation of aluminum. (Image courtesy of STEINERT GmbH)........................................................................84 Fig. 4.37 Image, under two perspectives, of the equipment used in the S3P process (Wakabayashi 2013). (Courtesy of Professor Katsuyuki Wakabayashi, Bucknell University, Lewisburg PA, USA).................98

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Fig. 5.1 Accumulated world production of plastics until 2019........................105 Fig. 5.2 Quantity of packaging generated in Europe, in 2018, by Country. (Source: Eurostat)...........................................................108 Fig. 5.3 Quantity of packaging recycled in Europe, in 2918, by Country. (Source: Eurostat)...........................................................109 Fig. 5.4 Evolution of the type of treatment carried out on post-consumer plastic, in Europe, between 2006 and 2018. (Data based on PlasticsEurope 2019).....................................................................110 Fig. 5..5 Evolution of waste treatment in Europe (EU28 + NO/CH), in millions of tons, from 2006 to 2018...............................................111 Fig. 5.6 Recycling, energy recovery, and landfill rates of post-consumer plastic in Europe (EU28 + NO/CH) in 2018, by country. (PlasticsEurope. Plastics – the Facts 2020. All rights reserved)..............................................................................................111 Fig. 7.1 Typical PVC construction products: (a) vinyl floor covering; (b) piping; (c) window profiles; (d) doors; (e) suspended ceilings.........................................................................120 Fig. 7.2 Auto-cad design of a set of semi-detached houses with the virtual roof constituted by Tectum’s prefabricated rainwater collection system, constructed from recycled PVC pipes (Kristen Tapping 2021)...................................................................................................137

List of Tables

Table 1.1 List of ISO standards and technical specifications regarding environmental management applicable to plastic materials and plastic industries.................................................................8 Table 1.2 List of ISO standards, technical specifications, and recommendations regarding environmental labels and circular economy, applicable to plastic materials and plastic industries.................................................................9 Table 1.3 List of ISO standards and technical recommendations regarding environmental footprint of biobased plastics............10 Table 1.4 List of ISO standards and technical recommendations regarding greenhouse gases applicable to plastic materials and plastic industries.................................................................10 Table 1.5 List of EN standards and technical recommendations regarding biobased products and sustainability of construction works................................................................11 Table 1.6 List of country standards, specifications, and guides regarding environmental aspects...............................................11 Table 4.1 Regulatory documents most used in Europe for recycled materials....................................................................................90 Table 4.2 Quality requirements set out in EN ISO 15347 91 Table 5.1 Distribution of plastic production in 2019 (PlasticsEurope 2020)................................................................106 Table 5.2 Total demand for plastics in Europe (EU28 + NO / CH) for industrial conversion, by sector of activity, in 2019 (PlasticsEurope 2020)................................................................106 Table 5.3 Plastics market in Europe (EU28 + NO/CH), by type of resin and application (PlasticsEurope 2020).........................107 Table 5.4 Distribution of recycled materials by sector of activity, in Europe (EU28 + NO/CH), in 2019 (PlasticsEurope 2020)................................................................112 xvii

About the Author

Luís  Eduardo  Pimentel  Real  Graduated in chemical engineering at the Instituto Superior Técnico (IST), Lisbon, Portugal. Holds a PhD in chemical engineering (IST, Portugal) and a PhD in chemistry (UBP, France). He worked in the Materials Department of National Laboratory of Civil Engineering (LNEC) from 1990 until 2015. Since January 2016, has been working in the Buildings Department of LNEC. Its activity has been very dispersed and covers several fields, namely applied chemistry, degradation and stabilization of polymers, durability, environmental issues (radon and recycling), biocomposites, assessment of construction products, and technical advice. He is author and co-author of more than 200 publications, including scientific papers in journals listed on the ISI WEB of Science, communications at international scientific meetings, and technical guides and reports, and has participated in several European research projects, and in specialized courses and technical training. He was responsible, for several years, for an accredited laboratory of plastics and composites. He was awarded the degree of specialist in metrology by the Portuguese Order of Engineers, for having carried out numerous activities in the scope of quality control of plastic materials and products, doing agreement activity and support for certification, technical auditing in plastic pipe factories located in Portugal and Europe, and participation in technical committees and working groups.

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List of Abbreviations and Acronyms

ABP abiotic depletion parameter (for LCA) ABS poly (acrylonitrile butadiene styrene) AP acidification parameter (for LCA) Bio-PBS biobased poly(butylene succinate) CEN European Committee for Standardization CENELEC European Committee for Electrotechnical Standardization CH4 methane C2H2 acetylene C2H4 ethylene CFC chlorofluorocarbon CIS Commonwealth of Independent States CO carbon monoxide CO2 carbon dioxide CO2 eq carbon dioxide equivalent CPR regulation of construction products DEHP Bis (2-ethylhexyl) phthalate DIS Draft International Standards DNA deoxyribonucleic acid EC European Commission ECHA European Chemical Agency ELV low voltage equipment EP eutrophication parameter (in ACL) EPPA European PVC Window Profile and Related Building Products Association EPS expanded polystyrene EU European Union FDIS Final Draft International Standard FprEN draft European Standard for Formal Vote FRC or FRP fiber-reinforced composites / plastics FTIRS Fourier-transform infrared spectroscopy GHG greenhouse gases xxi

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List of Abbreviations and Acronyms

GRP polymer/glass fiber reinforced plastic Gt gigatonnes GWP global warming parameter (in LCA) H2 molecular hydrogen HBP hydro-biodegradable plastics HCN hydrocyanic acid HDPE high-density polyethylene HIPS improved impact resistance polystyrene HSI hyperspectral imaging system HTP human toxicity parameter (in LCA) ISCC International Sustainability & Carbon Certification system ISO International Organization for Standardization LCA life cycle analysis LDH double layered hydroxide LDPE low-density polyethylene LLDPE linear low-density polyethylene LIBS laser-induced breakdown spectroscopy MIR mid-infrared MIR-HSI mid-infrared hyperspectral imaging system Mt megatonnes N nitrogen NAFTA North American Free Trade Agreement (North American Free Trade Agreement, involving Canada, Mexico, and the United States, replaced by the USMCA on July 1, 2020) NFC cellulose nanofiber NH3 ammonia NIRS near infrared spectroscopy NO nitrogen monoxide NOx nitrogen oxides O2 molecular oxygen OBP oxy-biodegradable plastic OLDP ozone depletion parameter (in LCA) P phosphorus PA polyamide (or nylon) PAc polyacrylate PB polybutadiene or polybutylene PBAT poly(butylene adipate terephthalate) PBT polybutylene terephthalate PC polycarbonate PCL polycaprolactone PCR post-consumer recycled PE polyethylene PET polyethylene terephthalate PHA polyhydroxyalkanoate PHB polyhydroxybutyrate

List of Abbreviations and Acronyms

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PI polyisoprene PIM powder impression molding PLA polylactic acid POCP parameter of photochemical ozone creation (in LCA) POM methylene polyoxide (or polyacetal) PP polypropylene PPE polyphenylene PS polystyrene PU polyurethane PUR rigid polyurethane (in the form of foam) PVC poly (vinyl chloride) RCF recycled carbon fiber REACH registration, evaluation, authorization, and restriction of chemicals ROH* hydroxide radicals ROO* peroxide radicals RS Raman spectroscopy S3P solid state shear spray technology SBS poly (styrene-butadiene-styrene) SPI Plastics Industry Society TDI toluene diisocyanate THz terahertz spectroscopy TR technical recommendation TS technical specification USMCA United States-Mexico-Canada Agreement UP unsaturated polyester UV ultraviolet radiation VFRC composites reinforced with vegetable fibers VIS visible spectroscopy VIS-NIRS visible- near infrared spectroscopy VOC’s volatile organic compounds WEEE waste electrical and electronic equipment WRAP action program for packaging recycling XPS extruded polystyrene XRF X-ray fluorescence XRFS X-ray fluorescence spectroscopy

Chapter 1

Environmental Aspects

1.1 Plastics as a Source of Pollution The use of plastic materials leads to a high carbon footprint related to their production, high volumes of waste, persistent pollution, and negative impact on the oceans, wildlife health, and ecosystems when leaks into the environment occur, resulting in considerable socio-economic costs due to negative impacts of plastic waste. Thus, plastics, although essential in everyday life and their essential use in several areas, are a source of pollution. Poor management of plastic waste is the main source of macroplastic leakage, which is responsible for 88% of plastic leakage, mainly resulting from improper collection and disposal. The pieces with a diameter smaller than 5 mm (microplastics), existing in the terrestrial environment and in the oceans, correspond to the remaining 12% (OECD 2019). There is already a significant accumulation of plastics (about 140 Mtons) in aquatic environments (rivers and oceans) and even considering some innovative measures,1 cleaning these plastics becomes increasingly difficult and expensive as plastics break down into smaller and smaller particles (OECD 2019). It is estimated that 20% of all plastic waste in the oceans comes from marine sources. In some regions, marine sources dominate. For example, in the Great Pacific Garbage Spot (GPGP), more than half of plastics are made up of nets, ropes, and fishing lines (RITCHIE 2018). The rest comes from plastic waste. The richest countries generate more plastic waste per capita, but have very effective waste management systems. The least wealthy and poorest countries have a

 Like the “Ocean Cleanup Interceptor” which was developed with the objective of capturing plastics leaking from rivers before they enter the ocean trough barriers that guide floating plastic waste to a waste collection vessel, powered by solar energy, capable of storing up to 50 cubic meters of waste (OECD 2019). 1

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 L. E. P. Real, Recycled Materials for Construction Applications, https://doi.org/10.1007/978-3-031-14872-9_1

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poor waste management system and are the main sources of plastic pollution in the global ocean. The life cycle carbon footprint of plastics is also very significant, contributing 3.4% of global greenhouse gas emissions over their life cycle, with 90% coming from the conversion of fossil fuels and the production of plastic materials (OECD 2019). It is obvious that all these leakages, gas emissions, and consequent environmental impact are not really a responsibility that can be attributed to the plastic itself. To solve the main problem, it is necessary to implement a recycling and reuse strategy, as well as discourage the waste and abandonment of plastics through public awareness campaigns on the value of plastic products, in order to reduce the disposal of unwanted and unusable products. The implementation of an appropriate recycling (and reuse) strategy and the improvement of waste management systems worldwide would make it possible to reduce plastic pollution and reduce the plastic footprint. The implementation of an environmental continuous information scheme for people, as well as legislative measures to discourage the illegal abandonment of waste and its discharge into the oceans, would lead to a radical reduction in the disposal of unwanted and unusable products.

1.2 Sustainability of Plastic Materials and Products Sustainability focuses on meeting the needs of the present without compromising the ability of future generations to meet their needs. The concept of sustainability consists of three pillars: economic, environmental, and social. The sustainability of plastics is a controversial issue. On the one hand, some people report that the almost permanent contamination of the natural environment with plastic waste is a growing concern. On the other hand, there are experts who argue that plastic materials are often the target of unfair criticism and false myths, namely those related to fossil origin and the consumption of energy for their production. It is a confirmed fact that the use of plastic saves more oil than is used in its manufacture (only 4%), as these products also help to save energy in applications such as heating, transport, etc., applications that are responsible for 96% of oil use. In addition, at the end of their useful life, the inherent value of plastics can be almost fully recovered. Added to this is the fact that plastics may also already be from a biological source. Many studies show that plastics help to save energy. In fact, according to the Denkstatt report (Denkstatt 2010), the energy consumption of plastics was 4270 GJ/ year compared to 6690 GJ/year consumed by other alternative materials. According to this report, replacing plastics across Europe (EU27 + 2) with alternative materials is equivalent to an additional 53 million tons of crude oil and an additional 61% of greenhouse gas (GHG) emissions.

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Finally, it is important to note that plastics are, for the most part, recyclable, so it is obvious that the use of recycled polymers contributes to sustainability in two ways: first, by diverting thousands of tons of plastic from landfills per year and, second, preserving natural resources, with an impact on the economy associated with energy consumption, and providing a significant reduction in greenhouse gas emissions. Plastics improve the quality of life of millions of people around the world, making it easier, safer, and more enjoyable, while being essential for accelerating the European transition to a low-carbon circular economy, where resources and energy are used in the most effective way. Society will only be able to take advantage of the potential of these extraordinary materials if it faces the global challenges related to their negative impact on the environment, at the end of their useful life. Global issues require global approaches and global solutions. It is necessary to create strong partnerships in the plastics value chain with all stakeholders, whether local, national or global, and to develop innovative and sustainable solutions, in order to create a structure to boost the circular economy for plastics and develop a project collective that allows to accelerate the transformation towards a more sustainable future, in order to guarantee that the plastics continue to offer social benefits and, simultaneously, have a positive impact on the environment (PlasticsEurope 2020). The creation of the International Sustainability & Carbon Certification system (ISCC), which is a sustainability certification program for biobased and circular (recycled) raw materials, has made an important contribution to the development of more sustainable plastic products and to reduce the risk for companies to create environmentally harmful processes, helping also the customers identify which companies provide a sustainable supply of agricultural raw materials.

1.3 Sustainability of Plastics Used in Construction Although the plastics used in civil construction are intended for long-term applications (pipes, cables, window and door profiles, coatings, insulation, etc.) and, therefore, these materials do not present as many problems as for other types of applications, intensive use and low durability (bags, packaging, etc.), the poor image of polluting plastics is also reflected negatively in all other plastic products. However, as the construction sector increasingly requires materials, logistics and transport, packaging and waste management, among other aspects, this sector and its supply chain contribute, on a large scale, to consumption and production patterns that have an impact on fundamental environmental aspects such as carbon footprint, incorporated energy, water, and waste (UNEP-SBCI 2012). The building construction sector is currently also the largest user of energy in Europe (40%) and, consequently, the largest emitter of greenhouse gases (39%), which means that this sector can have an impact huge in energy savings.

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Plastics help to conserve resources in buildings because they are light and good thermal and sound insulators, so they also contribute decisively to sustainability in construction, because in addition to being effective in a wide range of sustainability factors, they allow to improve the energy efficiency of buildings and reduce CO2 emissions. In addition, these materials also contribute to increase the durability of buildings, due to being less susceptible to corrosion. Its low density also influences energy savings in transport and alternative energy equipment (e.g., the propellers of wind towers). Consequently, it can be seen that plastic materials should not be banned, but their use should be intensified. If one considers the potential use of recycled and biobased plastics and composites in civil construction, the scenario will be even better in terms of sustainability. Increasing the incorporation of recycled plastic into new construction products, adding the development of plastic products, additives, and more environmentally friendly technologies, while ensuring durability goals and the good final performance of plastic products, constitutes an enormous contribution to promote the low carbon economy (decarbonization), circular production and sustainability, reducing impacts on the environment, generating employment, innovation, and technological development.

1.4 Circular Economy Recycling The recycling of fossil and biological plastics and composites, in addition to reducing pollution, also promotes decarbonization, circular economy, and sustainability, reducing impacts on the environment and helping to conserve resources. In fact, it is possible to recycle several plastics countless times, increasing the useful life of the material by hundreds of years, so the incorporation of recycled materials in construction materials and in the manufacture of new products is being increasingly explored. The application of concepts of circular production implies less consumption of natural resources and greater efficiency of processes, with consequent reduction in costs and environmental impacts. The circular economy and the closed cycles of plastics are dominating the current agenda, and recycling is at the center of numerous developments, also extending to the construction area, as it allows to drastically reduce GHG emissions, expand production and energy consumption clean and achieve gains in energy and production efficiency. Increasing the quantity and quality of plastic and recycled composites maximizes the retention and recovery of the value inherent in these materials, contributing to a “circular economy,” because it allows reprocessing plastics from flows containing low-value waste and transforming them quality construction products, commercial and with added value.

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Thus, a closed loop circular plastics, for construction, must act in three strategic domains to optimize and increase the amount of recycled plastic available to meet the growing demand for high-quality, recycled content in plastic products: 1. Collection and sorting, by increasing the collection of plastics using advanced material collection systems, including transportation, logistics, and infrastructure. 2. Recycling technology and classification, by upgrading recycling systems to more efficiently classify plastics, aiming to increase the total amount of high-­ quality for remanufacturing. 3. Manufacturing, by investing in facilities and equipment that manufacture finished products using recycled content.

1.5 Life Cycle Assessment 1.5.1 Generalities Life cycle assessment or life cycle analysis (LCA) provides the internationally recognized method to quantify the environmental impacts associated with all stages of the entire life cycle of a product, process, or service. –– The LCA process is a systematic and phased approach comprising four components: definition of objectives and scope; inventory analysis; impact analysis; and interpretation of results: –– Definition of objectives and scope: defines and describes the product, process, or activity. It establishes the context in which the assessment is to be carried out and identifies the limits and environmental effects to be reviewed for the assessment. –– Inventory analysis: Identifies and quantifies the energy, water, and materials used and environmental discharges (e.g., air emissions, solid waste deposition, effluent discharges liquids). –– Impact analysis: analyzes the human and ecological effects of energy, water, and material use and environmental discharges identified in the inventory analysis. –– Interpretation of results: evaluates the results of inventory analysis and impact analysis to select the preferred product, process, or service with a clear understanding of the uncertainties and assumptions used to generate the results. The LCA results are used to help decision-makers select products or processes that have the least impact on the environment. In the case of a manufactured product, the environmental impacts are evaluated from the extraction and processing of the raw material (cradle), through the manufacture, distribution, and use of the product, construction, repair, and maintenance, to the end-life treatment—-recycling or final disposal of the materials—that comprise it (grave), sometimes referred to as “cradle-to-grave analysis.”

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Cradle-to-cradle or closed-loop production is a specific type of cradle-to-grave assessment, where the disposal step at the end of the product’s life is a recycling process. This method is used to minimize the environmental impact of products through sustainable production, operation, and disposal practices, aiming to incorporate social responsibility into product development. A LCA study involves a complete inventory of the energy and materials needed throughout the value chain of the product and calculates emissions to the environment. For this purpose, all inputs and outputs at all stages of the life cycle are considered. There are currently several software specially designed for LCA, such as OPEN LCA, GaBi, SimaPro, and Umberto. General categories of environmental impacts that need to be considered are resource use, human health, and ecological consequences, which can be detailed in the following specific categories: 1. Resources depletion: it comprises the biotic (living things) or abiotic (non-living components—minerals, metals, and fossil fuels) resources depletion within an ecosystem based on reserves and extraction rates. 2. Pollution: it comprises global warming potential, ozone layer depletion potential, formation of photochemical oxidants, acidification potential, eutrophication (or nitrification) potential, human toxicity, and ecotoxicity. (a) Global warming potential: increase in the Earth’s average temperature, mostly through the release of greenhouse gases. Common outcomes are an increase in natural disasters and sea level rise. (b) Ozone depletion potential: the decline in ozone in the Earth’s stratosphere. The depletion of the ozone layer increases the amount of short wave ultraviolet B radiation (UVB) that reaches the Earth’s surface. UVB is generally accepted to be a contributing factor to skin cancer, cataracts, and decreased crop yields. (c) Photochemical ozone creation potential: the formation of photochemical ozone is a type of impact that can receive contributions from carbon monoxide (CO) and all volatile organic compounds (VOCs) capable of reacting with the hydroxide radical (ROH*) to form peroxide radicals (ROO*), which in the presence of nitrogen oxides (NOx) and ultraviolet light (UV) can induce the formation of ozone and other reactive compounds in the troposphere. (d) Acidification potential: a process whereby pollutants are converted into acidic substances which degrade the natural environment; common outcomes of this are acidified lakes and rivers, toxic metal leaching, forest damage, and destruction of buildings. The substances that most contribute to acidification are SO2, NOX, and NHX. (e) Eutrophication potential: an increase in the levels of nutrients, nitrogen (N), and phosphorus (P), released to the water (aquatic freshwater and aquatic marine) and soil, which can cause an undesirable change in species composition in ecosystems and a reduction in ecological diversity; a common outcome of this is high biological productivity that can lead to oxygen depletion,

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as well as significant impacts on water quality, affecting all forms of aquatic and plant life. (f) Human toxicity: comprises the impact on human health (cancer and non-­ cancer) of toxic substances present in the environment, including particulate matter and ionizing radiation. (g) Ecotoxicity: comprises the impacts of toxic substances on ecosystems (aquatic, terrestrial, and sediment). (h) Water use: comprises drinking water and brown water. 3. Land use: it has related impacts on the degradation of ecosystems (loss of biodiversity and in the loss of life support functions) and landscape.

1.5.2 Life Cycle-Based Sustainability Standards The International Standards Organization has developed and published several standards dedicated to sustainability, environment, and related topics. Some of these standards are adopted by CEN. The main product standards for LCA are ISO 14040 and ISO 14044. Both these standards cover life cycle assessment (LCA) studies and life cycle inventory (LCI) studies, including the definition of the goal and scope of the LCA, and the three life cycle analysis phases (inventory, LCI; impact assessment, LCIA; and interpretation), reporting and critical review of the LCA, limitations of the LCA, relationship between the LCA phases, and conditions for use of value choices and optional elements. ISO 14040 describes the principles and framework for life cycle assessment (LCA), but not describes the LCA technique in detail, nor specify methodologies for the individual phases of the LCA. ISO 14044 specifies requirements and provides guidelines for life cycle assessment. These and other important ISO standards related to LCA topic are listed in Tables 1.1, 1.2, 1.3, and 1.4. In the scope of biobased products, CEN published two standards, as well for sustainability of construction works (Table 1.5). Other country-specific standards (UK and USA) are indicated in Table 1.6.

1.5.3 LCA Case Studies 1.5.3.1 Plastics The estimated GHG emissions of fossil-based plastics in 2019 were 1.8 Gtons of carbon dioxide equivalent (CO2 eq), or 3.4% of global emissions that year (OECD 2019).

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Table 1.1  List of ISO standards and technical specifications regarding environmental management applicable to plastic materials and plastic industries Standard reference ISO 14001:2015 ISO 14002-1:2019 ISO 14004:2016 ISO 14005:2019 ISO 14006:2020 ISO 14007:2019 ISO 14008:2019 ISO 14009:2020 ISO 14010:1996 ISO 14011:1996 ISO 14012:1996 ISO 14016:2020 ISO 14040:2006a ISO 14044:2006a ISO/DTS 14074 ISO/TS 14071:2014a ISO/TS 14072:2014

Title Environmental management systems—Requirements with guidance for use Environmental management systems—Guidelines for using ISO 14001 to address environmental aspects and conditions within an environmental topic area—Part 1: General Environmental management systems—General guidelines on implementation of ISO Environmental management systems—Guidelines for a flexible approach to phased implementation Environmental management systems—Guidelines for incorporating eco-design Environmental management—Guidelines for determining environmental costs and benefits Monetary valuation of environmental impacts and related environmental aspects Environmental management systems—Guidelines for incorporating material circulation in design and development Guidelines for environmental auditing—General principles Guidelines for environmental auditing—Audit procedures—Auditing of environmental management systems Guidelines for environmental auditing—Qualification criteria for environmental auditors Environmental management—Guidelines on the assurance of environmental reports Environmental management—Life cycle assessment—Principles and framework Environmental management—Life cycle assessment—Requirements and guidelines Environmental management—Life cycle assessment—Principles, requirements, and guidelines for normalization, weighting, and interpretation (under development) Environmental management—Life cycle assessment—Critical review processes and reviewer competencies: Additional requirements and guidelines to ISO 14044:2006 Environmental management—Life cycle assessment—Requirements and guidelines for organizational life cycle assessment

Adopted by CEN as EN ISO

a

Production and conversion into products account for around 90% of the lifecycle emissions of fossil-based plastics. GHG emissions from the production and conversion of polymers vary depending on the polymer considered (with a range from 2.7 to 6.3 tons CO2 eq. per ton of plastics).

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Table 1.2  List of ISO standards, technical specifications, and recommendations regarding environmental labels and circular economy, applicable to plastic materials and plastic industries Standard reference ISO 14020:2000 ISO 14021:2016 ISO 14024:2018 ISO 14025:2006 ISO 14026:2017 ISO/TS 14027:2017 ISO/WD 59004 ISO/WD 59010.2 ISO/WD 59020.2 ISO/CD TR 59031 ISO/DTR 59032.2 ISO 14080:2018 ISO/DIS 14083 ISO 14097:2021 ISO 19694-1:2021

Title Environmental labels and declarations—General principles Environmental labels and declarations—Self-declared environmental claims (type II environmental labeling) Environmental labels and declarations—Type I environmental labeling— Principles and procedures Environmental labels and declarations—Type III environmental declarations— Principles and procedures Environmental labels and declarations—Principles, requirements, and guidelines for communication of footprint information Environmental labels and declarations—Development of product category rules Circular economy—Framework and principles for implementation (under development) Circular economy—Guidelines on business models and value chains (under development) Circular economy—Measuring circularity framework (under development) Circular economy—Performance-based approach—Analysis of cases studies Circular economy—Review of business model implementation [under development] Greenhouse gas management and related activities—Framework and principles for methodologies on climate actions Greenhouse gases—Quantification and reporting of greenhouse gas emissions arising from transport chain operations [under development] Greenhouse gas management and related activities—Framework including principles and requirements for assessing and reporting investments and financing activities related to climate change Stationary source emissions—Determination of greenhouse gas emissions in energy-intensive industries—Part 1: General aspects

End-of-life emissions vary significantly depending on the disposal option, with incineration the most GHG intensive (2.3 tons CO2 eq. per ton of plastics), not considering compensations due to energy recovered. Recycling directly emits 0.9 ton CO2 eq. per ton of plastic, but the use of secondary plastics can avoid emissions from producing primary plastics. The sanitary landfill is the least intensive disposal alternative in terms of direct emissions, with less than 0.1 ton CO2 eq. per ton of plastic, but it does not generate energy that can be used.

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Table 1.3 List of ISO standards and technical recommendations regarding environmental footprint of biobased plastics Standard reference ISO 22526-­ 1:2020 ISO 22526-­ 2:2020 ISO 22526-­ 3:2020 ISO/DIS 22526–4

Title Plastics—Carbon and environmental footprint of biobased plastics—Part 1: General principles Plastics—Carbon and environmental footprint of biobased plastics—Part 2: Material carbon footprint, amount (mass) of CO2 removed from the air and incorporated into polymer molecule Plastics—Carbon and environmental footprint of biobased plastics—Part 3: Process carbon footprint, requirements and guidelines for quantification Plastics—Carbon and environmental footprint of biobased plastics—Part 4: Environmental (total) footprint (life cycle assessment). Under development

Table 1.4  List of ISO standards and technical recommendations regarding greenhouse gases applicable to plastic materials and plastic industries Standard reference ISO 14064-1:2018 ISO 14064-2:2019 ISO 14064-3:2019 ISO 14067:2018a ISO/WD 14068 ISO/DTR 14069

Title Greenhouse gases—Part 1: Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals Greenhouse gases—Part 2: Specification with guidance at the project level for quantification, monitoring, and reporting of greenhouse gas emission reductions or removal enhancements Greenhouse gases—Part 3: Specification with guidance for the verification and validation of greenhouse gas statements Greenhouse gases—Carbon footprint of products—Requirements and guidelines for quantification Greenhouse gas management and related activities—Carbon neutrality [under development] Greenhouse gases—Quantification and reporting of greenhouse gas emissions for organizations—Guidance for the application of iso 14,064–1 [under development]

Adopted by CEN as EN ISO

a

1.5.3.2 PVC PVC has been the most studied polymer in terms of environmental impact. PVC products require comparatively less energy and resource use during production, as well as in conversion to finished products. They are lighter than those made of concrete, iron, or steel requiring less energy (and thus fewer emissions) to transport and install. Well-established schemes ensure that a large proportion of PVC used in construction applications, such as pipes, window profiles and flooring, cladding and roofing, are now recycled at the end of their useful lives (WRAP 2006).

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Table 1.5  List of EN standards and technical recommendations regarding biobased products and sustainability of construction works Standard reference CEN/TR 16957:2016

Title Biobased products—Guidelines for life cycle inventory (LCI) for the end-of-life phase EN 16760:2015 Biobased products—Life cycle assessment EN Sustainability of construction works. Environmental product 15804:2012 + A2:2019 declarations. Core rules for the product category of construction products EN 15978:2011 Sustainability of construction works—Assessment of environmental performance of buildings—Calculation method CEN/TR 16970:2016 Sustainability of construction works—Guidance for the implementation of EN 15804 CEN/TR 17005:2016 Sustainability of construction works—Additional environmental impact categories and indicators—Background information and possibilities—Evaluation of the possibility of adding environmental impact categories and related indicators and calculation methods for the assessment of the environmental performance of buildings FprEN ISO 22057 Sustainability in buildings and civil engineering works—Data templates for the use of environmental product declarations (EPDs) for construction products in building information modeling (BIM) (ISO/ FDIS 22057:2021) Table 1.6  List of country standards, specifications, and guides regarding environmental aspects Standard reference PAS 2050:2011 BS 8001: 2017 ASTM E3012–20 ASTM E3256–20

Title Specification for the assessment of the life cycle greenhouse gas emissions of goods and services Framework for implementing the principles of the circular economy in organizations—Guide Standard guide for characterizing environmental aspects of manufacturing processes Standard practice for reference scenarios when evaluating the relative sustainability of bioproducts

The CSIRO report (CSIRO 1998) concluded that the adverse environmental effects of using PVC in building products do not appear to be greater than for other materials. There are a series of socio-economic studies that focus more on to comparison of PVC products with other alternative materials, that are not referred in this book. Some of them are referred in a EC report (EC 2004), whose consultation is recommended.

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1.5.3.3 Biobased Plastics Despite the positive outlook of biobased plastics, in terms of GHG emissions, their environmental impact is controversial due to their potential to drive land-use changes, such as deforestation or competition with food production from agricultural activities, which can lead to increased GHG emissions. Currently, only 0.7 million hectares (≈ 0.02%) of agricultural land is used to grow the raw material for biobased plastics (OECD 2019). Therefore, the additional pressure on agricultural land is currently negligible and will remain so for years, even if high growth rates of biobased polymers are achieved. Thus, it can be concluded that bioplastics make it possible to reduce GHG emissions in the production of plastics, as long as the negative effects of changes in land use are avoided. Many other interesting studies focusing on biobased polymers are available in the reference literature: Some examples are listed below: –– –– –– –– ––

LCA of biobased plastic (Tsiropoulos 2015). LCA of biobased and fossil-based plastic (Walker and Rothman 2020). LCA of biobased PVC (Alvarenga 2013). LCA of biobased and fossil-based PE (Liptow and Tillman 2012). GGE emissions of biobased and fossil-based PET (Semba 2018).

1.5.3.4 Pipes 1.5.3.4.1  Plastic Piping Systems for Different Applications VITO, under the authority of The European Plastic Pipes and Fittings Association – TEPPFA, has carried out a life cycle assessment (LCA) from cradle to grave of four specific applications of plastic pipe systems (PEX pipe system for hot & cold water in the building; PP pipe system for soil and waste removal in the building; PE pipe system for water distribution; and PVC solid wall sewer pipe system) using the methodology prescribed in ISO standards 14,040 and 14,044. The conclusions of these studies carried out till 2012 show that when considering all the categories of the LCA, the CO2 footprint and the average environmental impact of plastic pipe systems are lower than of comparable other materials. Concluded also that the largest potential for optimization to raise the environmental performances of all pipe systems considered, that can be further developed, is the reduction of the mass or to reduce the amount of virgin resins and applying recyclates (TEPFFA 2010). In buried applications, the environmental profile can be still optimized by reducing the amount of soil that needs to be digged up and backfilled again at the trench during installation (TEPFFA 2010). For global warming (carbon footprint) the contribution of the pipe systems evaluated (expressed per functional unit, being the 100 meters of pipe system over its

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entire life cycle, calculated per year), was compared to the impact to global warming related to the driving of a passenger car over a defined distance (TEPFFA 2010), which seems to give an easily understandable idea in relation to current situations in real life. 1.5.3.4.2  Sewer Plastic Pipes A life cycle assessment of PVC water (storm and potable) and sanitary sewer piping, aiming to evaluate and compare different piping materials, for underground pipe infrastructure, was carried out in 2017 by the Sustainable Solutions Corporation (SSC) commissioned by Uni-Bell PVC Pipe Association (SSC 2017). The context of the study was to provide sustainable water and sewage services over a 100-year period, with minimal risk of degrading water quality (1), while reducing operation, maintenance, and repair costs (2) considering the variables which can influence pipe performance and service-level expectations (3). The U-PVC pipe depicted in this study was manufactured in the USA and Canada. The pipe formulation does not contain phthalates, lead or cadmium, but a tin-based thermal stabilizer. Based on the results from the LCA, PVC pipe provides both environmental and economic advantages to solving the water and sewer infrastructure needs for utilities and municipal projects. The LCA and research conducted for this study show that PVC has lower environmental impacts from a lifecycle and carbon footprint perspective—lower embodied energy, lower use-phase energy, and longer lifespan attributes compared to other pipe materials (SSC 2017). The study report also provides relevant data which can assist utility officials with their asset management plans and life cycle cost assessments for different pipe materials. 1.5.3.4.3  Wastewater Pipes of Different Class of Materials An independent study was published that utilizes LCA to analyze the environmental performance of four different piping materials in wastewater transportation infrastructure. This study was published in 2015 by Procedia Engineering and conducted by Purdue University as the Comparative Life Cycle Analysis of Materials in Wastewater Piping Systems (Vahidi 2015). This comparative study was carried out on the production stages of different pipe materials, because this phase had the maximum impact for all the four materials (ductile Iron, concrete, “FRP” composite fiber reinforced polymer, and PVC). The ductile iron production stage was the most deleterious, impacting almost all categories to a greater extent, except for ecotoxicity, which was most affected by the concrete production stage. Although the ductile iron production step has a considerable negative impact on the destruction of the ozone layer, as hydrochlorofluorocarbons (HCFCs) are

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generated during the production process of FRP pipes, the FRP production step is considered the most impacting step. in the ozone layer depletion category. The production of FRP and PVC pipes also affected the environment but not as much as ductile iron. Among the four pipe types analyzed by Purdue University, ductile iron has the maximum environmental and health impacts, while PVC has the lowest. Notably, ductile iron scored highest of all materials in the production of carcinogens. 1.5.3.5 Paint Buckets The majority of paint buckets are made of good quality virgin polypropylene (PP). Paint buckets containing water-based paint scraps are not considered hazardous waste. Paint buckets (empty or with leftovers) are usually incinerated with “other fuels,” and are not included in a recyclable fraction, due to the uncertainty as to whether they are empty, which means that the large quantities of plastic that could, in theory, to be recycled are incinerated (Plastic Zero 2014). As part of the Plastic Zero project, in 2014, a LCA was carried out to determine the environmental impacts in the city of Copenhagen, caused by the introduction of a separate collection for the recycling of paint buckets (scenario 1), as opposed to incineration (scenario 2). According to the LCA carried out, recycling of paint buckets in the city of Copenhagen would lead to a reduced emission of global warming gases of approximately 150 kg CO2-eq., Per ton of paint buckets, which would be equivalent to a total saving 45 tons of CO2 per year, if all buckets of paint in the city of Copenhagen were recycled (Plastic Zero 2014). The acidification potential was assessed as being similar for both scenarios, as the emissions of acid gases (measured in kg SO2-eq.) are not substantially different. For eutrophication, there may be an increase in emissions from recycling, as the replacement of energy is less. Based on this life cycle assessment, it was not possible to conclude that either of the two scenarios had a lesser impact on the toxicity categories, since the results of these were quite similar for the two scenarios. If the ink could be reused for purposes other than incineration, the environmental burden would decrease, as the incineration of the ink leads to liquid emissions (more direct emissions than the benefit of energy substitution) due to the low calorific power. If the paint could replace other products, it would further improve the environmental profile of the scenario. However, the ink would be of mixed colors and qualities and therefore with limited applications. If the city of Copenhagen had a greater use of renewable energy, this would further improve the recycling solution compared to incineration, as a result of the economic reduction resulting from the production of energy from incineration, which would make incineration even more unfavorable. If only empty paint buckets were included in the recycling system, handling would be easier, as there would no longer be a need for manual cleaning. However,

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the amount of recycled plastic would be much less (compared to a system that includes buckets with paint waste), and the corresponding environmental benefits would also be smaller. 1.5.3.6 Windows Excellent thermal insulation of PVC windows helps to significantly increase the energy efficiency of buildings. In a study that evaluated the impact of energy consumption and carbon dioxide emissions from windows made of different materials, such as PVC, aluminum, and wood (Recio, Narváez & Guerrero, 2005), accounting for all stages of a window’s life cycle (extraction and production, transport for assembly, assembly, transport to building, use, transport to landfill and, disposal in landfill, or transport to recycling and recycling), the lowest energy consumption and CO2 emission is attributed to the PVC window with 30% of recycled material (Stichnothe and Azapagic 2013). This study concludes the following: –– The step of using a window corresponds to the highest energy consumption and, therefore, the highest CO2 emissions. –– Energy consumption in the stages of material extraction and production, use and final disposal, is higher for aluminum windows (52%), and lower for wooden windows (4%), being the PVC with 14%. –– Regarding the recycling of window materials, there is greater availability of recycled PVC and aluminum for the manufacture of a new window, or for use in the manufacture of other products, than in the case of wooden windows, as the material does not can be recycled, a factor that partially penalizes this material. The results of a LCA study, regarding the recycling of PVC window frames, suggest that significant savings of environmental impacts can be achieved by using recycled instead of virgin PVC for window frames (Stichnothe and Azapagic 2013), corroborates the obvious conclusions of the previously referred study (Recio et al. 2005) in what it refers to the advantage of using recycled PVC in. 1.5.3.7 Recycling Processes The results presented in a research study (Lazarevic 2010) indicate that for the majority of scenarios previously investigated by LCA, mechanical recycling is generally the environmentally preferred treatment option. This is relevant for environmental impact categories related to energy use, including global warming potential, acidification potential, eutrophication potential, abiotic resource depletion potential, and residual solid waste production. However, it has been shown that the virgin material substitution ratio and amount of organic contamination could lead to recycling showing lower environmental benefits than other treatment options such as incineration with energy recovery, confirming the outcomes of WRAP (WRAP

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2006). A degree of uncertainty exists as to what ratio recycled plastic is substituting virgin plastic and the level of organic contamination for mixed plastic waste, suggesting that a focus should be placed on recycling of high-quality plastic waste to realize maximum environmental benefits from recycling. This underlines the need for a greater understanding of material flows related to different plastic resins in different waste streams, as well as plastic material characteristics and its ability to be recycled. An environmental and economic analysis comparing four different recycling technologies for recovery of PVC cable waste (Vinyloop mechanical recycling process, Watech and Stigsnæs feedstock recycling processes, MVR municipal solid waste incineration process) using landfilling as reference option (EMPA 2003), allowed to draw conclusions at different levels, namely at environmental and the economic aspects, recovery of either energy or materials, results for several impact categories and management of the polymer as a resource. Many other interesting LCA studies focusing on recycling process are available in the reference literature: Some examples are listed below: –– Environmental impact of solvolysis of expanded polystyrene (CE Delft 2019). –– Mechanical recycling of PLA versus chemical recycling via hydrolysis and re-­ polymerization (De Andrade 2016). –– Mechanical recycling versus solvolysis of expanded PS (KIDV 2018). –– Mechanical recycling of PET trays versus magnetic depolymerization (CE Delft 2019). –– Pyrolysis and gasification versus landfilling (Demetrious and Crossin 2019). –– Pyrolysis and gasification versus incineration with energy recovery (Demetrious and Crossin 2019; Khoo 2019). –– Mechanical recycling versus thermolysis (Khoo 2019).

1.6 Contribution of Regulations and Policies In recent years, there has been a growing awareness of plastic pollution in public opinion and this has paved the way for stronger political intervention. As a result, many countries have been implementing policies that specifically aim to reduce the negative environmental impacts associated with the different stages of the plastics life cycle. The European Commission has set itself the objective of making the construction sector more sustainable, addressing the sustainability performance of construction products in the revision of the Construction Products Regulation (CPR), as announced in the Circular Economy Action Plan, safeguarding the maintenance of the construction products price (EP 2021). In that plan, the Commission is committed to align and make construction product legislation more consistent with horizontal environmental policies and stresses the general need for a transition to a sustainable economy and a more circular

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supply, manufacture, reuse, and recycling of construction products and their use in construction works; stresses the need to improve the sustainability of construction products and the availability of secondary and renewable products and materials on the market; The current basic requirements for construction works defined in the revised CPR may already form the basis for the preparation of standardization mandates and harmonized technical specifications with regard to the environmental performance and sustainability of construction products. Finally, the European Commission (EC) intends to establish a common European data space for smart circular applications, with data and information on construction products, including products that are reused, or reconditioned, or manufactured from recycled materials.

Chapter 2

Plastic Materials and Additives

2.1 Generalities The term “plastics” is used to describe a wide variety of resins or polymers with different characteristics and uses. The term “polymer” is often used interchangeably with plastic, but although all plastics are polymers, not all polymers are plastics. Polymers are rarely useful in themselves, and are most often modified or formulated with additives (see Sect. 2.5), the compound product being generally called a plastic. Over the last century, plastics have offered innovative solutions to the constantly evolving needs and challenges of society. Versatile, durable, and incredibly adaptable plastics are a family of remarkable materials with science and innovation in their DNA. For this reason, plastic was considered the material of the twenty-first century (PlasticsEurope 2020). Plastic is a unique material, very useful and efficient material compared to other barrier materials, with many benefits, as it is cheap, versatile, light, and resistant, which makes it an excellent material for many applications. It can also bring environmental benefits, as they play a critical role in maintaining quality, safety, and reducing food waste, in transportation and alternative energy equipment, as well as in thermal insulation and in numerous construction applications (Sect. 2.6.4.1), serving a myriad of functional and aesthetic applications. Polymers, which are described below, can be classified into three categories: thermoplastics, thermosets, and elastomers. The polymer’s properties can be found in several publications, for what the author recommends the reference (Mark 1999).

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 L. E. P. Real, Recycled Materials for Construction Applications, https://doi.org/10.1007/978-3-031-14872-9_2

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2.2 Thermoplastics Thermoplastic polymers are composed of long chains of molecules, linear or branched, flexible, which means that molecules can flow under pressure when heated above their melting point; and that quality also makes them mechanically recyclable. They behave like viscous liquids at high temperatures (below the temperature of degradation or depolymerization). Thermoplastic polymers have a plastic behavior, which can be melted when heated, and become hard when they cool. Therefore, they can be heated and transformed repeatedly. These polymers are obtained by addition reactions and the macromolecules are linked through weak bonds (Van der Walls and hydrogen bonds) and by entanglement (Real 2017). These materials are rigid at a temperature below the glass transition temperature, and are very flexible between this temperature and the melting temperature. Thermoplastics with a higher degree of crystallinity (polyethylene and polypropylene) must be used at a temperature higher than the glass transition temperature. Amorphous or low crystallinity thermoplastics (polystyrene and polyvinyl chloride) do not have a melting temperature range and should be used at a temperature below the glass transition temperature. Thus, thermoplastics are much easier to adapt to recycling, as their characteristics are reversible. Thermoplastics can be reheated, remodeled, and cooled repeatedly. There are dozens of types of thermoplastics, each varying in crystalline organization and density. The types of thermoplastic polymers that are most frequently produced and used are polypropylene (PP), polyethylene (PE), which can be of low density (LDPE) or high density (HDPE), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), polyamide (PA), polytetrafluoroethylene (PTFE), methyl polymethacrylate (PMMA), and polycarbonate (PC). Some plastic products formulated with the mentioned polymers, commonly used to pack household products, show a numerical coding system created by the Society of the Plastics Industry in the late 1980s. The identification “OTHERS” refers to plastics generally stratified or mixed, with no potential for recycling and which must be landfilled.

2.3 Thermosets Thermosets are obtained by condensation and consist of long chains that are strongly crosslinked to each other, forming three-dimensional structures, to which the notion of molecular mass cannot be applied. These polymers are amorphous and infusible and once heated and formed, they cannot be reheated and formed again. They are, in general, more rigid and resistant than thermoplastics, but they are also more fragile. As they do not have a melting range, they cannot be easily reprocessed after crosslinking, as they do not become viscous liquids by heating, but retain their

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rigidity until they are degraded, by combustion or oxidation (Real 2017). Examples of thermosets are epoxy and phenolic resins, polyesters, polyurethane (PU), amines, and silicone.

2.4 Elastomers The elastomers are provided with an intermediate structure, in which there is also some crosslinking. These polymers have the capacity to undergo enormous elongation due to elastic deformation (up to 1000%), without permanent alteration of their original shape. These materials must be used above their glass transition temperature (Real 2017). Examples of elastomers are copolymer of acrylonitrile, butadiene, and styrene (ABS), copolymer of styrene, butadiene, and styrene (SBS), polybutadiene, and polyisoprene.

2.5 Polymeric Additives Polymeric additives, when added to polymers, make it possible to form useful compounds (called plastics), useful materials, with characteristics suitable for the manufacturing process and the use for which the final product is intended. Additives for plastics are subdivided into adjuvants and fillers. Adjuvants are all non-polymeric substances introduced into a polymer, in small quantities, with the aim of facilitating its processing, modifying, or improving its rheological behavior and/or its physical properties, and to give it stability over time, fundamentally to the action of ultraviolet radiation, oxidation, and impact. These substances are normally organic or organometallic products and generally have low molecular weight when compared to the polymers themselves (Real 2017). The remaining substances, usually minerals, used in high concentrations, are called fillers. However, certain mineral products can also be classified as adjuvants, as long as their function justifies it. An example of this are the mixed aluminum and magnesium carbonates, used in the thermal stabilization of PVC, or carbon black, also used as an antioxidant in polyolefins (Real 2017). Adjuvants are classified into categories, according to their function: thermal stabilizers, photochemical stabilizers, dyes, anti-oxidants, lubricants, plasticizers, impact modifiers, metal deactivators, nucleating agents, antidepositants, flame retardants, release agents, antistatic agents, sparkling, non-stick, etc. Additivation is done before or after polymerization, often during the granulation phase. The use of additives is not only dependent on the performance of formulations and applications, but also on legislation, consumer pressure, environmental and toxicological factors, and technological development (Real 2017). The effectiveness of adjuvants is fundamentally determined by the chemical functions present in their molecules, but the more or less complex molecular

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structure where the functional groups are inserted contributes to their physical behavior within the polymer, highlighting aspects associated with their compatibility and dispersibility, which govern the phenomena of migration, exudation, and extraction. The compatibility between polymers and adjuvants depends on the morphology of the polymer (the crystalline parts are generally impervious to the adjuvants, so they accumulate in the amorphous zones), the physical characteristics of the adjuvant (volatility, for example), and structural factors (interaction adjuvant polymer). The effectiveness of the adjuvant is all the better the more uniformly it is distributed in the polymeric matrix, so its solubility limit at normal temperatures of use is an important factor in defining the optimal concentration of adjuvant in the formulation. Its use in quantities above that limit leads to a phase separation over time, resulting in the migration of the adjuvant to the material surface. In order to ensure a convenient dispersion, a compatibilizing additive can be added that ensures the connection, on the surface, of the dispersed particles, between the adjuvant and the polymer. A part of the binding agent molecule has an affinity for the additive to be dispersed and another part has an affinity for the polymer. To facilitate the use of adjuvants, granulated mixtures can be prepared, containing high concentrations of additives, which will later be added to the resin granules without adjuvants (Real 2017). In addition to those factors (compatibility and degree of dispersion), in the preparation of formulations, it is also necessary to take into account the possibility of antagonisms of actions on properties or between additives. In fact, an adjuvant can improve a given characteristic in a polymer and, at the same time, undesirably modify another property of that same polymer. On the other hand, there is also the possibility that antagonistic (or synergistic) effects may occur between additives (Real 2017). Issues related to sustainability have led to the development of sustainable additives and natural products. The sustainability of this new generation of additives, such as plasticizers, can be ensured through certification systems, such as the ISCC, which assesses the ability of products to reduce the carbon footprint and support sustainable sourcing of renewable raw material.

2.6 Ecological Plastics 2.6.1 Generalities Conventional plastics are fossil-based, meaning they use non-renewable resources from the earth that must be conserved. Plastic takes so long to decompose that it remains effectively available forever if not recycled. Also, when it breaks down, it just disintegrates into smaller and smaller pieces that are eventually absorbed into

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the environment (microplastics, more dangerous than in original form) and water can be contaminated with plastic fiber. Thus, for environmental reasons, there is currently a great interest and growing incentive to use sustainable alternatives and more environmentally friendly materials. This has led to the development of bioplastics and biocomposites, which are a class of materials that can be used in the same applications as conventional polymers, but that have reduced energy costs and less pollution during their production. Another sustainable way to use plastics is to assure their reciclability and manufacture plastic products incorporating recycled plastics, contributing to the circular economy. Finally, the capacity of plastics for degradability, at the end of life, makes the plastic safer to environment and contributes to its sustainability. However, some degradable plastics, like oxo-degradable plastics, are not biodegradable and, thus, they cannot be returned to nature without harming the environment. The terms used for referring green polymers, like “biobased,” “bioplastics,” “degradable,” “biodegradable,” and “compostable” are often ambiguous. That there is also misleading information, partly motivated by the preference of customers for “green” products, as many industries incorporate, in their products, small amounts of plastic made with alcohol distilled from plants or cereals, and therefore attribute to these products, green lids, logos with leaves or green plants. In the next sections, an attempt will be made to explain the meaning of each of these terms and clear up the confusion.

2.6.2 Bioplastics Bioplastics are made from plants and agricultural sources, such as corn starch, sugar cane, beet, soy protein, lactic acid, or cellulose (the main component of tissues vegetable), instead of fossil fuels, such as oil and coal and, thus, the carbon content in any biobased polymer comes from organic sources, because the atmospheric CO2, which is chemically bound during photosynthesis is conserved during the production of bioplastics. Bioplastics include two types of materials, biobased and biodegradable plastics. Although they are not necessarily identical, because there are biodegradable plastics that can be composted and biobased plastics that are made of renewable resources but are not biodegradable. “Biobased” addresses a product’s origins, while “biodegradable” addresses end-of-life options. Polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), PLA and polycaprolactone (PCL), poly(butylene adipate terephthalate) (PBAT) and biobased poly(butylene succinate) (Bio-PBS) are examples of biopolymers, used to manufacture bioplastic products. Some bioplastics, such as polylactic acid (PLA), are both biobased and biodegradable. Bioplastics still represent a small slice of the market of plastics (around 80%, consisting of bioplastics that are made from biobased raw materials but are not

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biodegradable or compostable), but the trend is rising sharply in the coming years, because they are an important driver of the evolution of plastics, significantly contributing to a more sustainable society. Flexural and tensile properties of biopolymers are available in the literature (SpecialChem 2022). 2.6.2.1 Biobased Plastics Biobased only refers to what was used to make the material (produced from sources of renewable biomass and plants, such as corn, cassava, sugarcane, wheat, or residues of other processes, but doesn’t imply anything about what happens to it at the end of its life. Thus, it is not necessarily biodegradable. Biobased plastics can be partially or fully biobased and they are similar to polymers produced from fossil fuels. They can be produced as drop-in resins (as a substitute together with plastics of fossil origin) or as alternative resins with other characteristics (OECD 2019). Biobased plastics production generates fewer greenhouse gas emissions than fossil-based plastics, for what they have great potential as long as the impacts of land use are well managed. 2.6.2.2 Biodegradable Plastics Biodegradable plastics are related to the process where the plastic degrades in its end of life, but not all biodegradable plastics are biobased, some are fossil-based that are combined with an additive that makes them break down. A large number of bacteria and enzymes produced by microorganisms have already been identified with the ability to degrade biodegradable polymers that are not oxodegradable, which convert the material back into natural substances like carbon dioxide, biomass, and water. However, since 2013, the environmental impact of compostable plastics has become controversial due to the issues related to biodegradation in natural environments (OECD 2019). Microbial degradation of biodegradable polymers is not easily achieved in a natural environment and biodegradation also requires optimal conditions, rarely present in natural environments. In many cases, microbial degradation must be preceded by UV or hydrolytic degradation, or a specific composting environment must be created (Luyt 2007). The effectiveness and/or rate of biodegradation depends on the properties of the polymer, namely the surface conditions, chemical structure, molecular mass, physical properties, and morphology. When the microorganisms cannot consume the substance completely and leave residues, the level of biodegradability varies according to the degree of carbon conversion and, therefore, the level of environmentally friendliness also varies.

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Thus, the bioplastics that have the functionality of being also biodegradable can only be used if the waste management system is designed to treat biological waste in a special way, which is often not the case. Currently, there are not enough composting infrastructures to treat biodegradable plastic. Therefore, it is evident that the development of alternatives to conventional plastic, using biodegradable plastic, has not yet reached a stage where it could be reasonably adapted and scaled to the industrial level. Moreover, If collection and recycling conditions are not suitable, biodegradable plastics may compromise the quality of the recycled resources. Still, there is always the risk that consumers might get confused and put non-compostable plastics in their kitchen waste to be collected for composting. Furthermore, labeling plastics as biodegradable may suggest that their disposal in organic waste is acceptable (OECD 2019). Nonetheless, if more manufacturers start using biodegradable plastics and municipal recycling programs respond well, it will be possible to have functional infrastructure to compost the plastic, as the most important thing in this regard is to compost safely and, in such case, compostable plastics can be advantageous for specific applications. 2.6.2.3 Other Degradable Plastics In addition to biodegradable plastic resins that can be degraded by microorganisms in CO2, water, and biomass through a biodeterioration process, biofragmentation, and assimilation, there is also another type of degradable plastics, called photodegradable plastics, which do not contain organic additives, but which break when exposed to sunlight. The presence of oxygen and moisture also accelerates the breakdown process. An example of photodegradable plastics is the so-called oxo-degradable plastic, which breaks when exposed to ultraviolet light and heat, through a process that is catalyzed by additives like metallic salts. This chemical process accelerates the actual degradation, but the material cannot be considered biodegradable or compostable. The degradation of this type of plastics can lead to the release of microplastics and metals into the environment, whose effects on soil, water, flora, and fauna are still not well understood (OECD 2019). Moreover, oxodegradability can potentially corrupt the functionality of recyclable plastics and plastics with these functionalities must therefore be avoided in mechanical recycling processes (Plastic Zero 2013a). Several countries have already adopted regulatory measures on oxodegradable plastics. For example, since 2015, France has banned packaging made from oxodegradable plastic and the European Union has banned products made from oxodegradable plastic since 2019 (OECD 2019).

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2.6.2.4 Applications Currently, the main areas of application for bioplastics are in packaging, catering, agriculture and horticulture, the automotive industry, electronic applications, fibers and textiles, toys, leisure, and sports articles. The most important requirements for using this type of polymers in construction are that they can be processed in the melting state, be impermeable to water and maintain their integrity during normal use. Bioplastics are seldom used in construction materials. Although there are already experiences of incorporating polylactic acid (PLA) in wood-plastic composites, the biggest disadvantage being their low-­ temperature resistance during the production process. Packaging, like shopping bags and compostable waste collection bags, is the largest segment of the market for biodegradable plastic. Biodegradable plastic is also becoming popular for use in products disposable and single-use items: trays for fruits, meat, and vegetable, materials for pills and capsules, to make disposable catering service wares, bottles, tea bags, jars, air pillows, pens, pencils sharpeners, and mulch film. However, some biodegradable plastics can be sufficiently stable to be used in furniture and floors, among other applications typical of construction materials, because their decomposition depends exclusively on the presence of microorganisms that live in anaerobic environments and under controlled landfill conditions (no sunlight, no oxygen, more than 40% water). 2.6.2.5 Advantages and Disadvantages In principle, the manufacture of bioplastic products requires the same energy as the manufacture of plastics based on fossil fuels. The same can be said in relation to transport. Thus, it is not easy to assess for what purposes the bioplastics will have an advantage over conventional plastic, considering both the functionalities of the material and the mass flow of resources (Plastic Zero 2013a). Therefore, the various disadvantages of these materials can only be really compensated by reducing pollution (waste), energy consumption, and CO2 emissions, in a global life cycle analysis. 2.6.2.5.1 Advantages The main advantages of bioplastics and biodegradable plastics are the following: –– Sustainability. As bioplastics can be produced from renewable resources and there are several end-of-life options, their life cycle falls within the scope of the circular economy concept.

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The greatest advantage of these plastics is the lesser energy incorporated from the raw materials and the greater ease of degradation after their end of life. In fact, bioplastics are compostable and decompose easily in a few weeks, unlike conventional plastics, which can take more than 500 years to degrade. PLA, for example, when it decomposes in landfills, produces almost 70% less greenhouse gases than traditional plastics. It has also been found that companies of the ecological plastic sector are more likely to adopt alternative or low energy consumption processes, since they target the “green” market. In fact, bioplastics companies have instituted new manufacturing processes that reduce their greenhouse gas emissions and their energy needs, allowing them to emit less CO2 than the production of a typical petroleum-based plastic. –– Flexibility. Other great benefit of biobased plastic products is that once the desired material is converted into a polymer, it can be easily combined with the materials that are used to make conventional plastic. –– Recyclability. Recycling technologies available for common petroleum-based plastics, like reuse, incineration, pyrolysis, or chemical recycling, may also be applicable to biobased plastics. While products made entirely from bioplastics can cause problems in mechanical recycling facilities because they actually contaminate the recycling stream, making it unusable and ruining lots of reusable plastic waste, a product only partially constituted by bioplastics (for example, 30%) can also be subjected to mechanical recycling processes to obtain new products as long as the product’s material quality permits, and at the end of its life, return it to nature through composting. So while it’s not ideal, it’s likely the best option on the current market, because hybrids made of traditional plastics and ethanol-sourced plant material work with the existing recycling system and infrastructure. –– Benefits of biodegradability (when applicable). Biodegradable plastics take less time to decompose and they are also non-toxic since they have no chemicals or toxins. The recycled bio-waste can be used as compost or as renewable energy for biogas. Composting biodegradable plastic products can increase soil fertility. As they decompose, they improve the retention of water and nutrients in the soil and help grow healthier plants, without the need for pesticides and chemical fertilizers. The use of biodegradable plastic products instead of traditional plastics lessens the amount of greenhouse gas emissions, avoiding part of its effects such as desertification and extreme flooding. With the growing trend toward reducing decarbonization, biodegradable plastic products will be increasingly in demand in the future. In addition, many companies have addressed this social awareness, implementing marketing strategies to increase

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their sales, for example, by incorporating biodegradable plastics in the constitution of their products, also contributing to improve the environment. 2.6.2.5.2 Disadvantages The main issues and disadvantages of bioplastics and biodegradable plastics are of various types: –– Potential worsening of the food crisis. In general, the global need for arable land to produce biobased polymers is only 0.006% of global agricultural land (Ritchie 2018). The main raw material of biomass used for the production of biobased polymers is glycerol, as a biogenic by-­ product (37%). However, the use of soil, water, fertilizers, and plantations (often transgenic), for growing large quantities of corn, sugarcane, wheat, beet, or other genetically modified crops, constitutes an insurmountable environmental disadvantage of bioplastics, as these agricultural lands and these means could be used for growing food (Plastic Zero 2013a). –– Contamination risks. Bioplastics are made from soy and corn. Therefore, there is a risk of contamination as crops are typically sprayed with harmful chemicals, like pesticides, which can be easily transferred or included in the final product. Furthermore, there is also a risk of contamination between biodegradable and non-biodegradable plastics, as they must not be mixed when discarded. With many people unable to distinguish between the two types of plastic, both bioplastics can end up becoming contaminated and no longer recyclable. Many operational industrial composting facilities today won’t even accept PLA and other biodegradable plastics, because they are seen as contamination risks. The result of this is just to increase the volume of waste. –– Potential instability. Some bioplastics, when compared to conventional petroleum-based plastics, show poorer properties. As they degrade more quickly, they are not all are good for building materials, which must have high durability and good resistance to atmospheric agents. Moreover, to improve durability, they will need additives, to increase resistance to biological attack, greater resistance to moisture, as well as better thermal resistance during processing, leading to greater energy consumption and CO2 emission. –– Biodegradability conditions (when applicable). Biodegradability is as complex as the types of polymer chemistry and types of microbes that degrade the polymer structure. Thus the conditions of the environment usually have to be quite specific to degrade the plastic effectively.

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The need to create commercial composting sites in all countries of the world, where the different biodegradable polymers can be separated and composted in environments that contain microorganisms effective for the biodegradation of each specific polymer (s). The majority of the countries are ill equipped to properly compost any significant volumes of biodegradable plastic. –– Economic issues. The biodegradable plastics need expensive industrial processors and composters, especially those that require high temperatures on an industrial scale to be decomposed. In addition to the cost, there is a need for availability of equipment, which can be a problem, as most machinery manufacturers are only made by order. Biodegradable products are sold at a higher cost than traditional plastic. However, with improved technologies and more access to materials, however, this cost could be reduced in the future. –– Environmental issues. Some biodegradable plastics produce methane when they decompose in landfills. The amount of methane produced each year is high. Methane is several times more harmful than carbon dioxide and absorbs heat more quickly; therefore, if not held back, it could accelerate climate change. Thus, the disposing of bioplastics directly into landfills should be avoided and it is essential to guarantee its recycling. Biodegradable plastics cannot also decompose in ocean because the waters are too cold. Therefore, these plastics will either float on water or create microplastics that pose risks to marine life and not solve the ocean’s pollution problem. –– Recycling of biodegradable plastics. Biodegradable bioplastics cannot be mechanically recycled, as they contaminate other plastics.

2.6.3 Biocomposites Biocomposites include several types of composite materials, namely non-­ biodegradable polymers derived from petroleum, reinforced with biofibers; biopolymers reinforced with biofibers (the most environmentally friendly, referred to as “green composites”, which can be also biodegradable); biopolymers reinforced with synthetic fibers, such as glass or carbon; and inorganic materials containing natural fibers. Although biocomposite products already perform satisfactorily in many construction applications, they still need to be improved in some specific characteristics, like mechanical strength, stiffness, toughness, reaction to fire, resistance to UV degradation, to moisture absorption, and to biological degradation (Real 2017). Among different possibilities, fiber surface modification and chemical treatment of fibers are the most effective for decreasing hygroscopicity (increased resistance

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to moisture absorption and less susceptibility to retraction or volumetric expansion of fibers as a result of adsorption/desadsorption of water), improving the mechanical properties and microbial resistance. To improve the properties of green composites, the interfacial bonding between the fiber and the resin needs to be optimized, providing a more homogeneous composite and of greater dimensional stability, with better performance and greater durability. The surface modification of the fibers is done by means of grafting and cross-­ linking techniques, by coating or adding compatibilizers. Modification of the surface structure of the fibers or increase in surface energy has the effect of improving interfacial bonding by blocking the available hydrophilic spots and increasing the roughness, preventing the process of moisture absorption and thus reducing the damages resulting from the volumetric expansion of the fibers (Yatim 2013; Billington 2014). The impregnation of the natural fibers with polymer or with monomers, followed by polymerization in situ, allows to increase the resistance of the fibers from 60 to 250%. For this purpose, acrylates, methacrylates, epoxides, or melamine monomers are used. Compatibilizers already proved successful (Ishak and Thirmizir 2021) are glycidyl methacrylate (GMA) grafted biopolymer (e.g., PBS-g-GMA and PLA-g-­ GMA), maleic anhydride (MA) grafted biopolymer (e.g., PLA-g-MA, PHB-g-MA, and PBS-g-MA), and acrylic acid grafted biopolymer (PBSA-g-AA). Chemical treatments (with silanes or peroxides, or by acetylation or benzoylation) reduce the problems associated with the hydrophilic nature of the fibers, by altering the surface tension and polarity of the fibers surface (Yatim 2013). Other treatment methods aimed at increasing the durability of the biocomposites are the irradiation of the polymer and the fibers and the inclusion in the formulation of the composite of additives with special characteristics. The irradiation allows to improve the mechanical properties of the composite and the use of additives, such as low toxicity (biocides) antimicrobials, photochemical and flame retardants, enable actively to combat biodegradation, improve UV resistance and fire performance, respectively. However, it should be kept in mind that additive solutions can have a negative environmental impact. For each case, the effect of the selected treatments can be evaluated based on the measurement of the hydrophobicity and the volumetric expansion of the fibers under wet conditions. It is also important to evaluate the adsorption of moisture in the fibers as a function of the relative humidity of the air and its absorption by immersion in water, as well as to evaluate the mechanical properties (such as stiffness, resistance, and deformation) after adsorption of moisture and water absorption. This evaluation can be complemented with observation by scanning electron microscopy (SEM) after fracture, in order to extract a conclusion about the best options for the treatment of the fibers of the biocomposites under analysis. It is expected that, in the near future, these problems will be resolved and that biocomposites will have greater durability, greater resistance to fire and moisture, as

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well as better thermal (and acoustic) insulation performance, especially when combined synergistically with nanomaterials (such as silica aerogel). The construction industry is very demanding with regard to the characteristics of the materials, which must be suitable for the application for which they are intended and present, either a good performance or an appropriate durability. On the other hand, new products find it in applications. However, the use of more sustainable materials and products has been encouraging and increasing, due to the growing pressure exerted by consumers and/or by legislative imposition (Real 2017).

2.6.4 Recycled Plastics Plastic products that are recovered (from various sources, including the ocean) and recycled to make new products are called recycled plastics. However, recycling old materials to create new products has its disadvantages, as this production consumes, with rare exceptions, the same amount of time and energy as any other plastic product. The great advantage of recycling is the implementation of the circular economy, that is, reducing pollution and the consumption of natural resources (raw materials), promoting decarbonization, circular production and sustainability, reducing greenhouse gas (GHG) emissions, recover the value inherent to recycled materials, by reprocessing plastics from flows containing low-value waste and transforming them into quality, commercial and added value construction products. The recycled plastics may need to be mixed with virgin polymers or be added with specific additives to compensate for property loss and to improve their performance for certain applications (Sect. 2.6.4.1). 2.6.4.1 Additives for Recycled Plastics Recycled plastics can contain impurities and polymer contaminants that accelerate polymer degradation and change the material properties. Additive solutions can help increase the percentage of recycled content in end-use applications (such as building and construction), addressing specific quality issues associated with recycled resins, such as limited processing stability, poor long-term thermal stability, and insufficient protection from outdoor weathering, mainly based in the combination of antioxidants and light stabilizer systems (CW 2021). Repetitive extrusion and recycling of poylolefins causes a chain reaction that forms free radicals, breaks up the long polymer chains, and degrades the appearance and performance of the plastic. The addition of specific antioxidant masterbatches during these processes helps prevent yellowing, surface cracking, and helps to preserve critical mechanical properties such as impact resistance, elongation, and tensile strength (CW 2021).

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Recycled plastics, which contain a mixture of polymers and fillers, generally lack compatibility between them and can cause poor mixing, and lead to rough surfaces and poor final properties. In these cases, binding agents and compatibilizers act on the molecular interfaces of different surfaces to improve properties and processing. Examples of compatibilizers are minerals used to compatibilize PE and PP. Other compatibilizers are used for various normally incompatible mixtures such as PP/PA, PO/PET, PA/PET, or for polar/non-polar polymer alloys, WPCs, and natural fiber composites (CW 2021). Viscosity modifying additives, lubricants, and processing aids can also be effective in improving product manufacturing conditions from recycling streams. There are also combined products on the market, specific for various polymers, for example, those designed for recycled PP and polyolefin blends containing impurities, for recycled PP with a high content of PE, for polyester compounds “contaminated” with other resins, for recycled HDPE, polyolefins and mixed polymers used in rigid applications, for recycled LDPE and LLDPE for incorporation into films and related flexible packaging applications and for reclaimed HDPE and PP blends for re-use in outdoor goods. Part of the plastic used to manufacture wood-plastic composites (WPC) may result from post-consumer recycled materials (RPC), so it may have a bad odor as a result of amines and/or volatile sulfur components formed by post chemical reactions-­processing. There are specific additives to neutralize the odor associated with natural fillers, such as lignin and cellulose, and the processing and reprocessing of polymers. Some additive manufacturers have developed a series of additives in the area of odor reduction; there are examples of additives that result from the combination of a lubricant and an odor neutralization mask designed for specific products, such as wood-plastic composites (PRW 2019a). Another example of additives for recycled plastics are polar zinc cations that tend to group together in ionic clusters within the polymer matrix, promoting the formation of a network (such as carbon-carbon covalent bonds in aliphatic polymers) that leads to better resistance to Fusion (CW 2021). Other solutions include upcycle processing aids made from post-consumer and post-industrial recycled plastics for compounds suitable for pipes, fittings, and sheets (CW 2021). Additives can play also an important role in washing and drying technologies for recycling plastics, optimizing the washing step and shortening drying time, as well as reducing the water content in the recycled material, which results in lower energy consumption during the drying and recomposition process. Other developments include a biodegradable desiccant additive that reduces water absorption during the washing step, which can eliminate the need for centrifugation and more efficient wetting and biodegradable agents (PRW 2021b) or a biodegradable de-watering additive that reduces water uptake during the washing step, which can eliminate the need for centrifuge and more efficient biodegradable de-­ foaming and wetting agents (PRW 2021b).

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Some companies have been developing pigments, showing a good compromise between color tone, opacity, polymer compatibility, non-toxicity, and NIR detection due to a specific adjustment of their reflectivity. These pigments allow black material to be readily classified even at high polymer flux velocities, whereas color articles formulated with carbon black could not be classified (PRW 2021c). Some pigments and colors were developed and optimized to allow the classification and recycling of black plastic products, even with high dye resistance and opacity, NIR reflectivity in any concentration and high heat resistance, making it suitable for use with all plastics, even after several steps processing (PRW 2021c). In addition to the additives that aim to improve the performance of recycled plastics or optimize the recycling processes, there is also a special type of additives to give biodegradability to plastics, called oxodegradable products. The use of these additives gives rise to a specific type of biodegradable plastic, called oxy-biodegradable plastic (OBP). While hydro-biodegradable plastics (HBP) are made from biobased products such as corn, wheat, sugar cane, petroleum-based products, or a mixture of the two, OBPs are made by adding a small portion of fatty acid compounds of specific transition metals to traditional plastics. The carbon in OBP is converted to CO2 over a longer period of time, while HBP degrades and biodegrades more quickly than OBP (Rosato 2016). OBP undergoes chemical degradation, by hydrolysis and oxidation, respectively; OBP is degraded by oxidative fission of the chain catalyzed by metal salts, leading to the production of shorter chain molecules; in oxygen-containing environments, plastics containing oxodegradation additives degrade and fragment, with smaller fragments with less molecular mass being conducive to biodegradation (Rosato 2016). Several organizations, universities, environmentalists, industry experts, suppliers, and technology companies have been involved in a controversy over OBP versus HBP.  The European Bioplastics Association issued a positioning document distancing itself from the oxy-biodegradable sector, and the SPI (Society of the Plastics Industry) Bioplastics Council, based in the USA, issued a positioning document on oxy-biodegradable additives and other degradable additives in support of the European Bioplastics Association. These entities consider that the use of degrading additives is not a sustainable way of tackling this issue of waste management, as there is no doubt that the materials that contain these biodegradable additives actually biodegrade in landfills, or that they can be recycled. In other words, degrading additives do not add value to plastic waste (Rosato 2016).

Chapter 3

Use of Polymer Materials in Construction

3.1 Plastics The wide range of appearance and performance properties of plastics are derived from the inherent characteristics of the individual polymeric material, its composition (polymer plus additives), and how it is processed and used. Although plastics are not always visible in buildings, the construction industry increasingly uses these materials for a wide range of applications, including insulation, piping, exhaust and ventilation ducts, window frames, and interior design. This growth in applications is mainly due to the unique characteristics of plastics, namely their chemical resistance, mechanical properties (strength, dimensional stability), insulation properties (electrical, thermal, and acoustic), their durability, the possibility of recycling, and many others. The construction industry has an important role to play in reducing energy use and carbon dioxide emissions, which are the biggest contributor to global warming, so the use of plastic materials contributes to sustainability in construction (see Sect. 1.3). The polymers most often used in buildings and construction are as follows: PE, PP, PVC, PC, expanded polystyrene (EPS), extruded polystyrene (XPS), polyurethane foam (PU), acrylics (usually PMMA), and composites. However, new plastics are always emerging, as they are materials in continuous development, with a large component of innovation. For example, recently, the plastics industry pioneered the creation of a new polymer that increases thermal resistance, using up to 50% less raw material (EuPC 2014). The polymers most often used in buildings and construction are as follows: PE, PP, PVC, PC, EPS, XPS, polyurethane foam (PU), acrylics (usually PMMA), and composites. However, new plastics are also always emerging, as they are materials in continuous development and which stand out for innovation. For example, the plastics industry has recently pioneered the creation of a new polymer that increases thermal resistance, using up to 50% less raw material (EuPC 2014).

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 L. E. P. Real, Recycled Materials for Construction Applications, https://doi.org/10.1007/978-3-031-14872-9_3

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In 2019, the Civil Construction sector consumed 10.3 million tons of plastics, that is, 20.4% of the total plastics consumption in Europe (EU28  +  NO / CH), becoming the second largest plastic application after the packaging (Table 5.2). The main applications of non-reinforced plastic materials in construction are as follows: –– –– –– –– –– –– –– –– ––

Piping systems for different uses. Buried tanks, manholes, and systems for wastewater treatment facilities. Screens and geomembranes for cladding and insulation. Doors and windows. Rail supports on railway tracks. Support structures on the coastline (e.g., docks). Roofs and false ceilings. Cladding and facades for buildings. Seismic reinforcement systems and pads for the dissipation of seismic energy, placed between the buildings and the respective foundations.

In most of these applications, it is possible to use polymeric materials, partially, or totally recycled, therefore with evident social and environmental benefits. To enable the production of high-quality recycled materials, the plastic waste from the end-of-life products used in the aforementioned applications must be separated according to the nature of the constituent polymer. However, there are a large number of different varieties of plastic resins and mixtures of resins used in construction products, without codes, which are difficult to separate, collect and recycle, so they must be sent to incineration or mixed waste streams.

3.2 Fiber-Reinforced Plastics 3.2.1 Classification of Composites Composites can be classified according to the nature of the matrix (ceramic, polymeric, or metallic) and by the type of polymeric resin (thermoplastic, thermoset) and respective origin (synthetic, biological, or mixed). Fiber-reinforced plastics (FRP) are called polymer matrix composites and result from the combination of fibers (natural or synthetic), which can be continuous or discrete, in concentrations typically in the range of 12–60% by volume, wrapped in a matrix of thermoplastic resins or thermosetting. These composites can have inorganic fillers in the formulation, usually up to 20% by volume, but some types of polymeric composites can contain up to 50% of their weight in fillers, usually calcium carbonate, talc, or mica powders (Yazdanbakhsh and Bank 2014).

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Polymeric composites can also be classified based on the type of reinforcement (fibers, particles, or structures—laminated or sandwiched) and the nature of the fibers (organic, inorganic, biological, or synthetic). Fiber-reinforced composites can also be classified by the length of the fibers (long aligned and continuous, or short and discontinuous, aligned, or randomly oriented). Finally, composites used in buildings can also be classified into two main groups: structural and non-structural composite materials, depending on whether or not they support loads during use. Examples of structural composites are those applied to support walls, stairs, roof systems, sidewalks and pedestrian roads, docks, sidewalks and paving slabs. Examples of non-structural and semi-structural composites are those used in various situations of less structural demand, such as external wall coverings, decorative elements, insulation, tiles, furniture, windows, doors, and other products of the same type (Real 2017).

3.2.2 Characteristics of Polymeric Composites Composite materials of fiber-reinforced plastic matrix (based on PRF) are a class of materials that exhibit great potential for use in civil engineering infrastructures, having demonstrated their usefulness in several areas of construction during the last three decades. Due to their good resistance and specific rigidity, low weight, dimensional stability, architectural flexibility, and aesthetic appearance, they have been replacing some of the traditional materials used in construction, being able to refer to a wide range of applications. PRF-based polymeric composites have important advantages over many other traditional building materials (such as steel and concrete, and wood, in certain circumstances). These advantages typically include lower densities (i.e., low weight), higher mechanical properties in specific directions (fiber orientation, for example), ease of installation, and greater durability in aggressive chemical and aqueous environments. The disadvantages compared to conventional construction materials generally include higher costs, lower temperature resistance, and therefore worse fire performance, and some difficulty in recycling. The improved mechanical properties of composites in relation to other materials is a key feature and they can be found in specific literature: –– Flexural and tensile properties of ramie-fiber-reinforced composites (Irawan 2011). –– Flexural properties of glass-fiber-reinforced composites (Singh et al. 2013). –– Tensile properties of composites (Singh et al. 2013; Al-Hasani 2007; De Paiva et al. 2006). –– Tensile properties of fibers (SpecialChem 2022), (Wambua et al. 2003; Ahmad et  al. 2006; Saheb and Jog 1999; Holbery and Houston 2006; Hajnalka et  al. 2008; Sapuan 2005).

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–– Shear strength of composites (Unal and Dayal 2003; Short 1995; Feraboli and Kedward 2003; Feraboli and Kedward 2004). –– Mechanical properties of jute-fiber-reinforced composites (Khan and Khan 2014). These are just a few references, as the topic has been widely studied and when accessing these documents online, several other papers related to the subject are usually presented.

3.2.3 Application of Polymeric Composites in Construction 3.2.3.1 Generalites Most of the polymeric composites used in civil construction are based on polyester or epoxide resins reinforced with continuous glass or carbon fibers (FRC or FRP). There are some examples of efficient structures of high durability, consisting of these materials, which have facilitated and promoted the acceptance of the FRP in construction. The flexibility of FRP has allowed its wide use in construction, both in non-­ structural and semi-structural components and also in innovative structural developments, without compromising structural integrity and, generally, without increasing costs, so superstructures are made up exclusively of FRCs. The main advantage of these materials comes from the synergy that can be obtained in integrated uses, with other more conventional materials. Taking bridges as an example, there is a large number of hybrid structures, in which only a part of the superstructure is made of FRC. The composite surface can also be textured to facilitate bonding to other conventional materials, such as mortar and concrete. Its ease of transformation during the manufacturing process of finished products and its compatibility with other construction materials, provides more dimensional and architectural flexibility, as it allows the achievement of complex shapes, which cannot be obtained with traditional materials, which are more creative and innovative, with a pleasant appearance and easy social acceptance. Its excellent resistance to corrosion reduces maintenance needs and ensures greater durability. The benefits associated with transportation, installation, and safety prevail with the use of structural elements of PRF. Endowed with lower density, PRFs reduce transport costs and become safer to handle at the construction site. It is also possible to prefabricate modular elements, facilitating assembly at the construction site and reducing installation time. Its excellent corrosion resistance reduces maintenance needs and ensures greater durability.

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3.2.3.2 FRP Waste FRP production and the subsequent manufacture of FRP products release a notable amount of waste. In highly efficient processes such as pultrusion, waste (scrap) is in the range of 3−5%, while in less efficient manual lay-up processes, it is usually close to 15% (Yazdanbakhsh and Bank 2014). Applications of FRP waste in concrete include precast paving slabs, tiles, wall panels, paving blocks, and exterior cladding materials of an architectural nature. The waste generated from the production of glass fiber-reinforced polymer (GRP), usually in the form of short rebars or defective rebars with poorly adhered glass fibers, can be used directly for incorporation into concrete parts or elements with lower structural strength, for example, that used to cover pavement (Yazdanbakhsh and Bank 2014). A potentially viable use for fiber-reinforced plastic waste is the partial replacement of fillers or aggregates in cementitious materials (particularly Portland cement mortar and concrete) (Yazdanbakhsh and Bank 2014) and in various construction materials (Job 2010), with little effect on durability. However, it is necessary to identify new applications and continue developing methods to reuse FRP manufacturing waste. 3.2.3.3 PRF Products There are a large number of applications for plastic materials reinforced with fibers and composites, namely the following: –– –– –– –– –– –– –– –– –– –– –– –– –– –– –– –– –– –– ––

Repair and rehabilitation of structural elements. Repair and reinforcement systems for wooden structures. Structural profiles and small structures for buildings. Formwork. Side protection systems on bridges. Closed lower walkways for circulation in bridges. Strengthening of beams in bridges. Light structural walls. Exterior wall coverings. Insulation. Covers for special acoustic applications. Floors. Energy efficient roofing and in passive construction. Decorative sound-absorbing wall and ceiling coverings. Decorative elements. Exterior fences and interior partitions. Reinforcement of beam joints with pillars. Reinforcement of slabs, walls, silos, chimneys, and tunnels. Anchoring systems.

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3  Use of Polymer Materials in Construction

Cargo transmission bars for road infrastructures. Construction of pedestrian bridges supported or suspended. Pedestrian paths. Docks. Solar panels and wind energy structures and turbines. Explosion protection kits.

Among the applications mentioned above, the frequent use of FRP to repair concrete structures and rebuild buried pipes is noteworthy. Composite beams have also been used extensively on several bridges, either because of their low weight or their high mechanical strength. Thus, FRP beams and paving slabs are already an efficient, economical, and more easily installed alternative for replacing old slabs with reduced span that no longer meet the current requirements for bridges (Alampalli et al. 2002). PRF panels are also used to serve as formwork systems for concrete elements by pouring the concrete directly onto the interconnected fiberglass panels. As the panels are corrosion-resistant and lightweight, they do not need to be removed, thus functioning as a lost formwork. This saves on labor costs and makes installation faster. Some typical applications of polymeric composites and recycled plastics (https:// inhabitat.com/axion-­international-­makes-­rail-­road-­tracks-­bridges-­and-­i-­beams-­ from-­100-­recycled-­material/) are illustrated in Fig.  3.1, namely in exterior urban applications (a); small structures (b); pedestrian and vehicle traffic bridges (c); train traffic bridges (d); lower bridge walkways (e), and suspended pedestrian bridges (f).

Fig. 3.1  Examples of typical applications for fiber-reinforced composite materials: (a) pavements and outdoor urban furniture; (b) Sheraton Hotel - Malpensa Airport, Milan, IT; (c) Camp Mackall, North Carolina, USA; (d) York, Maine, USA; (e) Severn Crossing approaches, UK; (f) Kolding, Denmark

3.3 Biocomposites

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3.3 Biocomposites 3.3.1 Generalities The resurgence of composites reinforced with vegetable fibers (VFRC) and other types of biocomposites is the result of a great interest in sustainable technology, due to their lower incorporated energy. Vegetable fibers are a type of renewable natural resource, with abundant availability and accessibility, which provide less environmental impact than traditional fiber-reinforced composites. The advantages of natural fibers and biocomposites occur at the most diverse levels (Rao, Prasad & Sharma, 2007; Faruk and Sain 2014; Real 2017): –– Environmental: they represent renewable resources and require little energy during production. –– Biological: they are natural organic products and are not dangerous to health, as they do not cause adverse dermal effects in their handling and do not present biological danger when they are discarded. –– Technological: they have good mechanical properties (damping and stiffness, for example), are lighter, provide good thermal and electrical insulation (due to the tubular structure of the fibers, with many empty spaces), have excellent performance at low temperatures, low coefficient thermal expansion, versatility for complex 2D shapes, they are non-abrasive and have great processing flexibility. –– Economic: biofibers are cheaper than synthetic fibers. –– Social: they have benefits for agriculture because they constitute a secondary income for farmers, and are also available on a more global scale. –– Risk: biofibers are safer, as they are less likely to cause accidents during fragmentation and shattering when subjected to mechanical action. The disadvantages of biocomposites are related to their lower durability in applications in humid environments, and their lower resistance to fire (Real 2017). These materials are also sensitive to microbial attack resulting in a volumetric expansion of the fibers that causes partial or total loss of their reinforcement properties. This dilation can also lead to the weakening of the interfacial bond with the resin and the formation of micro-cracks, which further increase the transport and absorption of water, both in liquid and vapor states. In addition, some natural fibers (such as linen, for example) have a high curl tendency and low permeability (Real 2017). The main disadvantages and limitations of biocomposites in long-term applications are, in summary, the following (Faruk and Sain 2014; Real 2017): –– Low thermal stability, resulting in difficulties in finding an adequate manufacturing technique. –– Poor resistance to moisture adsorption due to the hydrophilic nature of the fibers, which compromises the adhesion properties at the interface between the fibers and the matrix.

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–– :ow resistance to radiation and consequent photochemical degradation when exposed to UV radiation. –– Low melting temperature. –– Low fire resistance and low fire reaction rating. –– Decomposition in alkaline environments. –– Susceptibility to biological attack. –– Dimensional instability of the fibers due to the residual stresses induced during processing. –– High variability of physical and mechanical properties, as they depend on materials, environment, and processing technology. All of these aspects compromise the mechanical properties of biocomposites, as well as their dimensional stability and chemical composition, limiting the potential for application of biocomposites in the construction area. To increase the durability and performance of biocomposite materials, it is necessary to act in several aspects, such as in the treatment and modification of the fiber surface, addition of natural resins, and coating of the final biocomposites.

3.3.2 Use of Biocomposites in the Construction Although it is more common to find natural fibers in the reinforcement of composites in recent years, instead of the usual glass and carbon fibers, its use is not new. Various natural fibers, such as cane bagasse, bamboo, wood, wheat, cereal straw, holly and rice, sunflower stems, coconut, hemp, cotton, kenaf, banana, pineapple, and tobacco leaves, were widely used in 1970s and 1990s for the manufacture of panels (Yatim, Khalid and Mahjoub 2011). In India, a variety of construction materials, using industrial and agricultural waste and integrating cement and cementitious materials as binders, were used to make earthen slabs, tiles, and weather-resistant coatings (Yatim, Khalid and Mahjoub 2011). The fiber-reinforced cement composite was one of the most promising materials for the exterior and interior use of buildings, in the form of fences, ceilings, exterior and interior cladding, floors, walls, bricks, frames, decorative elements, for simulating other materials (tiles and slate), and slabs for various construction applications. Fiber cement composites, containing cement and wood, have been widely used to replace old cement products with asbestos fibers (meanwhile banned), as well as many other non-structural building materials, such as floorboards, sidewalks, wood products from cedar, tiles, bases for the application of tiles, architectural elements, and replacement materials for wood-based products (Madhuri et  al. 2005; Yatim 2003). These composites are more resistant to fire, moisture, fungi, to attack by insects and, consequently, have a greater durability than conventional wood. However, some of these materials continue to have problems and exhibit degradation due to exposure to moisture and drying cycles and, therefore, require maintenance and protection through the application of varnish coatings or paint coatings.

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As an additional example of construction involving mixtures of natural fibers with inorganic materials, monolithic construction using lime with hemp fibers, the material of which can be recycled as fertilizer, or mixtures of hemp and lime for aggregates, can be referred to. The potential benefits of these solutions include better permeability to air and steam, important hygroscopic properties, and low thermal conductivity. Lime also protects hemp components from fire and worms (avoiding the need for toxic chemical treatments). Natural fibers can also be used as reinforcement for prefabricated concrete panels applied for slope stabilization and soil retention. Biocomposites reinforced with natural fibers, such as plastic wood composites (WPC), are widely used in outdoor applications, as substitutes for solid wood and wood-based products, such as garden and pool furniture, floors, walls, doors, and windows. WPCs are also widely used as insulation materials on docks, guards, decks and roofs, suspended ceilings, interior panels, wall coverings, roof eaves, and as decorative elements on walls and ceilings, as well as for special acoustic applications, such as sound-absorbing walls (Yatim, Khalid and Mahjoub 2011). The formwork systems based on biocomposites are a development of the PP formwork systems, which have replaced, with advantages, the traditional wooden formwork systems. These systems are used in several applications, namely in the following (Yatim, Khalid and Mahjoub 2011; Cassaforma Muro 2016): –– Separate the spans from the bridge beams, replacing the steel, as they are lighter and more porous, and because they have the capacity to be easily broken in case the bridge deck needs to be inspected from the bottom. –– For reinforcing concrete with raised walls, inverted beams, and foundation shoes, reducing the construction times of the foundations. –– For the construction of dispersion tanks and/or water collection (works that are increasingly necessary in the most diverse construction contexts). –– For the construction of ribbed rafts (structures not normally used due to excessive formwork and demoulding work). –– For the simultaneous construction of foundation and slab beams. –– For the creation, in one step, of the upper slab (cavities) and internal and perimeter beams for the foundation of the structure. –– For any work that requires, for various reasons, an elaborate and geometrically complex formwork. The properties of these systems, such as porosity (allowing water to evaporate through the elements and preventing corrosion of metal elements in bridges), mechanical strength (capable of supporting heavy loads, without beams), low weight, and modularity, have numerous advantages over traditional systems. The lost formwork systems based on biocomposites, in addition to allowing the designer to change the geometric parameters to adapt to all situations with great architectural freedom, also have several economic advantages. In fact, they are easy and quick to assemble without the need for specialized labor, allow the simultaneous concreting of the foundation of the beams and the slab (which saves time),

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dispense cleaning (as they are perfectly smooth and clean), and allow save on storage and transport costs (since the material is compact and weather resistant). Recent developments in composite flooring systems, consisting of reinforced plastic lost formwork systems and concrete slabs (Koteš and Vičan 2014; Remy 2011), with greater load capacity, are promising for the future development of similar solutions, replacing glass fibers with natural fibers. Biocomposites reinforced with ramie fibers are used in ballistic panels, allowing to achieve a level II resistance to ballistic penetration in polyester matrix composites or level III in hybrid polyester and Kevlar composites, which corresponds to an energy absorption of 1362 J at 624 m/s or from 3185 J to 837 m/s, in panels with a thickness of 15 and 25 mm respectively (Faruk and Sain 2014). In addition to the aforementioned uses, biocomposites are currently found in many other common applications in the field of construction, namely in handrails, coverings, floors, fences, false ceilings, garden, and indoor furniture (benches, chairs, tables), in a wide variety of door panels and window profiles, counters, dishwashers, sanitary products and accessories, corrugated boards, tiles, guards, small buildings (bungalows, etc.), insulating materials with ecological characteristics, stairs, docks, supports for cable routing, pedestrian bridges, drain grates, energy efficient roofs, and various products for use in passive houses. Some biodegradable composites, made of natural fibers and biodegradable plastic resins, are sufficiently stable for use in a wide variety of construction materials, as they only undergo degradation under anaerobic conditions. When subject to biodegradation, biodegradable composites release methane gas that can be captured and burned for energy recovery or reused to produce more biocomposites.

3.4 Recycled Plastics In the construction industry, plastic is mainly used in pipes, thermal and acoustic insulation, wall and floor coverings, interior fittings, window frames, scaffolding boards, and fences. The plastics that can be more easily recycled and converted into products with reuse of the same polymer are of the thermoplastic type, namely the following: PET, HDPE, LDPE, PP, PVC, PS, and ABS. The recovered plastic can be used in construction in many applications, including moisture membranes, drain pipes, ducts, floors, decks, packaging, in applications related to landscape aspects (walkways, jetties, pontoons, bridges, fences, and signs), urban furniture (benches, dustbins, signs and flower boxes), containers and garbage bags, traffic management systems, industrial straps for packaging, and even as loads to incorporate in the filling of other materials (mainly in the case of thermosetting plastics, more difficult to recycle). The plastic products manufacturing process also generates large amounts of waste and scrap, mainly in the start-up of the manufacturing line and in the rejected material after internal quality control. This can be converted into granules and sent

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Fig. 3.2  Waste resulting from the manufacture of pipes and fittings (Whittle and Pesudovs 2007). (Copyright ©Institute of Materials, Minerals and Mining, reprinted by permission of Taylor & Francis Ltd., http://www.tandfonline.com on behalf of Institute of Materials, Minerals and Mining.)

in reprocessing bags, giving the manufacturer a disposal option, free of charge and environmentally friendly for reused plastic, and for bags (also usually made from recycled material). A good example of this is the one that is often adopted in the plastic piping industry (Fig. 3.2). Even in the final stage of life, plastics remain a valuable resource for simply being disposed of. If Europe were able to achieve best practices and have efficient recycling and energy recovery technologies, about 5 million more tons of plastic could be recycled, avoiding the emission of 7 million tons per year of CO2 (equivalent to removing 2.4 million vehicles from road traffic) and an additional generation of 300 TWh of electricity. Thus, CEN has been introducing changes in terms of the possibility of incorporating recycled plastics, in certain products and applications, like plastic pipe systems, in order to contribute to the circular economy. In accordance with current regulations and standards, the incorporation of recycled materials in plastic piping for the distribution of drinking water is still not allowed, due to the possibility of contamination. Also in the case of pipes for pressure applications, incorporation is not recommended due to the possibility of forming weak points that facilitate rupture. A possible way of applying recycled material in a pressure pipe is restricted to its use in intermediate layers of structured and multilayer pipes, since the coextruded pipes, containing an intermediate layer of compact or foamed recycled material, maintain a mechanical resistance and a durability equivalent to conventional pipes. This type of solution also applies to plastics piping systems for non-pressure underground drainage and sewerage, namely structured-wall piping systems of PVC-U, PP, and PE, covered by the standard EN 13476–2. It is also important to highlight the role of plastic additives in plastics that have been recycled, reground, or are off-specification, since in this case the base plastic starts with lower grade properties and its properties need to be improved (see Sect. 2.6.4.1). Finally, application of recycled composites can be consulted in Sect. 7.5.5.

Chapter 4

Recycling

4.1 Generalities Society is increasingly focused on environmental issues and plastics recyclability, which is reflected in regulatory and legislative initiatives. Companies with strategies to reduce the environmental impact of their products also need to review all the processes that intervene in the development of a product and find solutions to maximize its recyclability at the end of its useful life, in order to contribute to sustainability and to the circular economy.

4.2 Classification of Recycling Processes The primary recycling process consists of reusing materials and products in others that have similar characteristics to the original product, being only feasible with plastics from semi-clean industrial waste, so this process is not widely used. The secondary process, also called mechanical recycling, consists of the physical treatment of post-consumer resins for the purpose of reprocessing the material. This recycling method has been used successfully for a long time in industrial and technological waste of unique classification (end-life windows, pipes, packaging, etc.). Today, this type of material recycling remains an expanding recycling method, offering a variety of benefits. Unlike incineration, the environmental implications are minimal and the investment costs are much lower compared to chemical recycling. Mechanical recycling is the recycling method most often adopted, since in the chemical recycling method waste has to undergo complex chemical treatments. The tertiary process, also called chemical recycling, involves the production of basic chemicals and fuels from plastic. This type of recycling process is increasingly applied due to the need to adapt to the high levels of contamination in the waste. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 L. E. P. Real, Recycled Materials for Construction Applications, https://doi.org/10.1007/978-3-031-14872-9_4

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The last form of recycling is the quaternary process, also referred to as thermochemical recycling or incineration, which uses energy from plastic through burning (energy recovery). This process is common and widely used in recycling, due to the high heat energy content of most plastics. Most incinerators can reach temperatures in the range of 900–1000  °C.  Currently, the main concern of this process is the decrease in the amount of air pollutants that are released. The most beneficial contribution of this process consists in the reduction in mass (in 80%) and in volume (in 90%) of the residues through the process of heating to high temperature. However, some plastics are less suitable for energy recovery, such as halogenated plastics, because they can form, as a result of incineration, highly toxic dioxins. These negative side effects for the environment and health, associated with the emission of toxic gases, can be, at least, partially eliminated by the application of catalysts that allow oxidizing harmful gases in situ. The materials left over from this process are then placed in landfills. Landfill is not a recycling process and should be the last solution to be adopted. Waste containing plastic should not be admitted to a landfill for inert waste, except in trace amounts. Organic or biological recycling (composting) is a controlled microbiological treatment of biodegradable plastics waste under aerobic or anaerobic conditions and does not directly fall within the scope of plastic recycling processes.

4.3 Cascading Principles for Recycling Plastic recycling can be seen as a cascade with different levels of quality (Plastic Zero 2013a). It is possible to use recycled plastics several times depending on the type of polymer. However, contamination and the breaking and crosslinking of polymeric structures will become limiting factors for the prolongation of the cycles. The recycling system covers the entire range of plastic waste, from pure polymers, with high added value, to mixed qualities, of low value, since it is not possible to separate all plastic waste in a “pure” quality grade. There are many qualities of recycled materials on the market. The main reason is that some sources are able to provide purer and homogeneous plastic waste than others, and single polymer industrial waste versus mixed packaging waste. Thus, it is necessary that recycling be treated as a cascade process, where high-­ quality plastics can eventually be classified into inferior qualities. The costs of sorting waste will reach a point of equilibrium, at which it is no longer economically viable to improve quality through subsequent sorting, but this point is difficult to identify because it will vary according to the regulations of each country and the implementation of plastic waste treatment, as well as fluctuating raw material prices. This could be overcome by means of regulations that impose taxation for the use of landfills or for the incineration of waste, and if a scheme for producer responsibility and eventually financing for these situations, among other possible measures, was implemented. In addition, the politically determined

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recycling targets set quantitative rather than qualitative targets for waste management. Without clear targets for the quality of recycling, there seems to be a lack of incentives to increase the quality of plastic recycling and avoid downcycling (Plastic Zero 2013a). When plastics are agglomerated and used as building materials or the like, they will usually be incinerated after use (Plastic Zero 2013a).

4.4 Value Chain for Plastic Waste From a systematic point of view, the plastic recycling value chain can be divided into the following general operations: –– –– –– –– ––

Supply in large quantities of used plastic. Collection of used plastics. Sorting and separation of collected plastics. Reprocessing (production of secondary raw material). Manufacture of new products.

The different stages of the value chain are affected according to the others. The characteristics (composition, type, and quality) of the collected plastic will affect the selection of the classification technology, which again will affect the quality of the flow at the outlet and, consequently, the type of applications in which the secondary plastic can be used (Plastic Zero 2012). The collected waste can be pre-consumer waste (industrial waste, from the manufacture of products) or post-consumption waste (waste resulting from the use of plastic products in the consumer market). The next steps in waste processing will depend, to a large extent, on the origin and composition of the waste. Often, pre-­ consumer waste will have undergone a mono-material collection (unmixed) and will have low levels of impurities, while post-consumption waste will generally need more intensive treatment. Due to the high quality of pre-consumer plastic waste, it is often economically viable to recycle these waste streams internally, at the production facility, or through external channels.

4.5 Machinery for Recycling Waste recycling is complex and demanding. Usually, a complete modular system for recycling of plastics should include a set of units, like cutting, washings, separation, drying units, classification, and production of final products, including machinery that should be selected according to the type of plastic waste, final products, and applications.

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Figures 4.1 and 4.2 present complete recycling lines for two different waste plastic materials. Sub-processes and associated equipment, in particular separation technologies and dimension reduction, can be ignored, replaced, or repeated, depending on the quality of the input material and the requested quality of the output material: –– Initial screening, using belts and a pickup station (when needed, Fig. 4.3), for separating and manually sorting the material to remove foreign substances from the targeted polymer material. The manual separation may be replaced by automatic separation, using any of the technologies mentioned to later. The belts are used also further ahead to transport the material to the shredder or granulator, and to subsequently discharge size-reduced material from them. –– Removal of ferrous metals by a magnetic drum (Fig.  4.4) or aluminum by an eddy current separator (Fig. 4.5), when necessary. These operations also protect the granulator and washing components located further on. –– Separation of coarse foreign material from the material flow and to protect the downstream components, using an air aspirator or a cyclone (Fig.  4.6). These devices are generally used as a preventive treatment for the partial reduction of the polluting elements and for the separation of dust generated by manufacturing in recycling and general waste treatment sectors. –– Dimensional separation using air separators or ballistic separators (Fig.  4.7). These separators are used to separate plastics from metals, sand, stones, fibers, etc., or to remove small and light parts as well as heavy parts and pieces having the same particle size but different specific weights. Ballistic separators allow to configure a separation into three or four fractions, several size ranges, and many options. In certain waste flows, other types of separation may be used. –– Discharge and transport of the material from or to various units, like cleaners, dryers, and granulators, using suction units and/or belts.

Fig. 4.1  HDPE/PP recycling line, for barrels, boxes, containers, pipes, desks, and chairs. (Image courtesy of Jiangsu G.E.T. Recycling Technology Co., Ltd.)

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Fig. 4.2  Recycling line for waste from electrical and electronic equipment. (Image courtesy of Jiangsu G.E.T. Recycling Technology Co., Ltd.)

Fig. 4.3  Picking station. (Image courtesy of M6K Group)

–– Reduction of dimensions of the material to the necessary size cutting (Fig. 4.8), shredding (Figs.  4.9 and 4.10), granulation (Fig.  4.11), and pulverizing (Fig. 4.12). –– Removal of the material from the cutting mill, shredder, granulator, pulverizer, or vibrational screening using transport systems already mentioned. –– Separation of fines to achieve a better quality final product, using an air separator or a cascade sifter (Fig. 4.13). The inlet material moves in the airflow and the heavier material, which has a lower float factor, separates from the lighter fraction that continues to flow in the airflow direction. The degree of separation depends on the number of stages that are used in the complete unit.

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Fig. 4.4  Magnet separator: (a) rotary magnetic drum that can be integrated into an existing conveyor belt as a machine component. (Image courtesy of STEINERT GmbH); (b) magnetic drum already mounted on a feeder belt inline. (Image courtesy of M6K Group)

Fig. 4.5  Eddy current separator. (Image courtesy of STEINERT GmbH)

–– Storage of different size materials, to allow consistent feeding of the wash, cleaning, and subsequent separation, using holding silos (Fig. 4.14) or containers; this equipment is also used forward, after completion of the drying process for further treatment. –– Cleaning of the plastic by washing, using a pre-wash drum (Fig. 4.15a), centrifugal washer (Fig.  4.15b), friction washer (Fig.  4.16), or intensive cleaner (Fig. 4.17); a hot washing system is recommended in any materials where heavy contamination and persistent odors must be treated, enabling a considerable reduction in organic contamination to be achieved; a cleaner system can be also used as dry cleaner or pre-cleaner without requiring water consumption. –– Separating the dissolved contamination of the material which has been washed and size reduced, using a dewatering screw (Fig. 4.18). –– Screening of loose and swimming particles from the waste water for final discharge to drainage system, using an appropriate screening machine (Fig. 4.19); the screening machines may also be used in previous steps, primarily for screening powder formed material that requires a very fine end product and can be

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Fig. 4.6 Air stream separators: (a) high efficient air aspirator. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH); (b) cyclone separator. (Image courtesy of B + B Anlagenbau GmbH)

Fig. 4.7 Dimensional separators: (a) dry densimetric separator. (Image courtesy Guidetti Recycling Systems); (b) ballistic separator. (Image courtesy of Komptech GmbH)

integrated into the pulverizer systems to screen the oversized material (for example, PE pulverizing). –– Density separation of plastic parts with a specific density or by type of polymer, using a floating sink tank or a fluid-density separator tank (Fig. 4.20) for separation of the plastic parts with a specific density; the mixed plastic stream is dosed into the tank where high-density materials will sink, and low-density materials

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Fig. 4.8  Guillotine shear, providing separation by cutting mill pressure, essential to separate large waste parts that have fused or meshed together. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)

Fig. 4.9  Pipe shredders: (a) image courtesy of Wiscon Envirotech; (b) image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH

will float. The separated particles will be recovered and conveyed for further processing.1 –– Drying using a mechanical (Fig. 4.21) or thermal dryer (Fig. 4.22).

 After the plastics are sorted and washed, they can be regranulated. Wet-milling is often used to prevent clogging of screens and thermomechanical degradation of plastics. If powdered material is required, plastics can be pulverized in a mill equipped with a cryogenic medium. 1

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Fig. 4.10  Double-shaft shredders adapted for large volume and large strength materials like WEEE, waste household, plastic containers, barrels, etc.: (a) Image courtesy of Jiangsu G.E.T. Recycling Technology Co., Ltd.; (b) Image courtesy of Wiscon Envirotech

Fig. 4.11 Granulators: (a) and (b) Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH; (c) Image courtesy of Wiscon Envirotech

–– Efficient wastewater treatment units to be integrated into washing lines (advisable). –– Optical classification of polymers by type of polymer and color (Fig.  4.23, 4.24, 4.25). –– Extrusion for the production of pellets (Fig. 4.26). –– Packing of recycled materials, in bulk or baled. –– Final quality control through laboratory tests.

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Fig. 4.12 Pulverizer. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)

4.6 Collection Collection of used articles is the first step in the value chain of the post-consumer recycling process, as it can immediately contribute to defining the limits for meeting the quality requirements of buyers, since the variable quality of the input material constitutes a barrier to the search for recycled plastics. Establishing closed material circuits generally requires a separate collection system to avoid mixing the target products with other products. In the case of glass bottles, it is possible to separate the bottles from a mixture of waste streams, because they are relatively easy to recognize and are found in large quantities. There is also another common way of collecting bottles, using deposit and return systems. However, it is not always easy to guarantee a good level of separation in other types of products, including plastic packaging. The risk of mixing colors and types of polymers and/or contaminating plastic with non-targeted materials in the collection phase, increases with the diversity of mixed waste, leading to the need for a more rigorous classification later.

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Fig. 4.13  Zig Zag air separator. (Image courtesy of Jiangsu G.E.T.  Recycling Technology Co., Ltd.)

It is in the interest of recyclers to encourage and promote sorting at the source, as it increases the value of the residual plastic and reduces the cost of reprocessing. To make separation at source efficient, it is important to continuously provide citizens with information on how to separate plastic material for recycling. This is an important barrier for more improved recycling (Plastic Zero 2012).

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Fig. 4.14  Holding silo. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)

Fig. 4.15 Washers: (a) Pre-Wash. (Images courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH); (b) Centrifugal washer. (Image courtesy of Jiangsu G.E.T.  Recycling Technology Co., Ltd)

Taking into account the wide range of applications for plastics and the level of demand for plastics and composites for use in construction, this area can be considered potentially large and promising for the use of recycled materials. Although the separation in construction works of plastic products, by product type and type of plastic or composite material is not difficult (Fig. 4.27), the collection schemes necessary for bulky waste plastics and construction and demolition waste cannot always be established, which is an obstacle to multiple recycling cycles.

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Fig. 4.16  Friction Washers, for intensive cleaning of plastic flakes and separation of impurities: (a) Images courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH; (b) Image courtesy of Wiscon Envirotech

Fig. 4.17 Intensive cleaner. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)

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Fig. 4.18 Dewatering screw. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)

4.7 Separation 4.7.1 Generalities The second step in the recycling process is the separation, which includes sorting, shredding (and grinding), separation, and cleaning. The cleaned recyclate is dewatered, reground, and used for fabricating new products. Although in the case of construction materials the separation methods applied to other wastes are not generally applied, it is relevant to mention these methods, as some of these wastes may later be used for the production of construction materials. A typical separation and classification process comprises several classification steps, by which different types of materials are removed from the primary mixed waste stream. The classification process often includes the following sub-processes (Plastic Zero 2012; Plastic Zero 2013b; PRW 2021b):

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Fig. 4.19 Screening machine. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)

Fig. 4.20  Two perspective views of a sink float separation tank: (a) Image courtesy of Wiscon Envirotech; (b) Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH

–– Initial screening: refers to activities that take place at the treatment plant and includes many different types of technologies for material separation, as well as polymer decontamination and production of raw materials. –– Sorting: to remove films, cardboard, and bulky items and for polymer screening. –– Magnetic and eddy current separation: removal of ferrous metals and aluminum. –– Dimensional separation: to isolate small/light/two-dimensional parts (low thickness items) from three-dimensional articles (such as containers and packaging), as well as to remove heavy parts (such as glass and stones). –– Size reduction of plastic waste: pre-grinding the plastics to an optimal particle size to obtain fragments with dimensions, for example, between 10 and 60 mm, before the washing, cleaning, and post-separation processes.

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Fig. 4.21  Mechanical dryers, where the wet granulates/foil flakes will be centrifuged with high rotational speeds against sieves that are mounted at the outside, which will be cleaned continuously to prevent clogging: (a) Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH; (b) Image courtesy of Wiscon Envirotech

–– Cleaning of the plastic: by washing and drying, to remove dirt from the surface and labels.2 The glue can be removed with hot water and caustic soda; the cleaned recyclate is dewatered and dried; in dry cleaning, contaminants are removed by friction, rotating the particles at high speed. –– Final separation: by type of polymer, etc. –– Post-screening. –– Water treatment and purification of plastic, when needed. Most European separation and classification facilities use a combination of the technologies mentioned above to guarantee an economic and efficient classification of the input material, with satisfactory quality at the exit. The exact composition of the technologies used must be adjusted according to the input material and also to the quality required for the output material, because most of the extant separation processes have certain limitations that compromise their effectiveness in dealing with multiple substance mixture.

 As washing and drying technologies are important for raising the quality of recycled plastics, new additives are being recently introduced that can improve the washing process and reduce drying time (see Sect. 2.6.4.1). 2

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Fig. 4.22  Thermal dryer: the material flow, fed through a cyclone, will be charged with hot air to achieve vaporizing of the water and therefore a drying of the grinding stock. (Image courtesy of NEUE HERBOLD Maschinen- u. Anlagenbau GmbH)

Fig. 4.23  Back and front views of a color line camera. (Image courtesy of JAI A/S)

4.7.2 Wet Separating Techniques for Separating Plastics 4.7.2.1 Generalities Since, in general, polymers have different densities (or ranges of different densities), the plastic can be separated by immersion in a fluid medium. Contaminants, made up of other materials present in the plastic stream, can also be removed (Plastic Zero 2012).

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Fig. 4.24 Hyperspectral imaging camera setup as optical sensor for recycling applications. (Image courtesy of LLA Instruments, Germany. All rights reserved LLA Instruments GmbH & Co. KG Germany)

The most appropriate use for this technology consists of the separation of plastic from heavier materials, or to separate materials from the intermediate fraction from dimensional separation equipment (Plastic Zero 2013b), and/or to improve the performance of subsequent equipment for near-infrared classification. In the past, before the appearance of the NIR method (Sect. 4.7.3.4), the wet technologies were mostly used to separate PVC and filled PP from the plastic waste stream, but they were progressively replaced by optical separation technologies, and are no longer very common in Europe.

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Fig. 4.25  Color sorting system equipped with an RGB line scan camera and 3D detection. (Image courtesy of STEINERT GmbH)

Fig. 4.26  Extruder machine. (Image courtesy of EREMA Group GmbH)

Although wet separation techniques provide adequate recoveries, they have clear disadvantages over some dry ones, due to some problems associated with wet separating methods, such as: 1 - Treatment of water from the process for reuse or discharge. 2- The requirement of expensive wetting reagents, and most importantly. 3- Dewatering or drying the mixture after separation cannot be avoided.

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Fig. 4.27  Pallets of PE and PVC pipes classified (Whittle and Pesudovs 2007). (Copyright ©Institute of Materials, Minerals and Mining, reprinted by permission of Taylor & Francis Ltd., http://www.tandfonline.com on behalf of Institute of Materials, Minerals and Mining.)

4.7.2.2 Froth Flotation Froth flotation is a technique based on hydrophobicity differences between particles and is a potential method for plastics separation, in particular for plastics with particle size greater than 2.0 mm (Pita and Castilho 2017). In pure water, all plastics show contact angles greater than 80°, indicating that they are naturally hydrophobic (or non-wetting). Thus it is difficult to achieve separation by flotation, except using a wetting agent, which means that they require the addition of chemicals that promote the selective wettability of one of its components, for a flotation separation (Yoon 1997). Flotation of mixed plastics utilizes selective wetting characteristics in order to change the surface of specific plastics from hydrophobic to hydrophilic. The froth flotation can be used for separating shredded and pulverized plastics. The separation process occurs in several steps using common wetting reagents. For example, a successful separation in 3 steps of four different types of plastics, namely PVC, PC, polyacetal (POM), and polyphenylene (PPE), is done using common wetting reagents like sodium lignin sulfonate, tannic acid, aerosol OT (sodium bis(2-­ ethylhexyl) sulfosuccinate), and saponin (Dodbiba and Fujita 2004). As the concentration of the wetting agent increases, however, the contact angles arc reduced substantially and the difference between different plastics becomes magnified. These findings provide a basis of separating plastics by flotation.

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The quality of separation varied with the mixture type, depending not only on the plastics hydrophobicity, but also on the size, density, and shape of the particles, i.e., the particle weight. Flotation separation of plastics can be enhanced by differences in hydrophobicity. In addition, flotation separation improves if the most hydrophobic plastic, that floats, has a lamellar shape and lower density and if the most hydrophilic plastic, that sinks, has a regular shape and higher density (Pita and Castilho 2017). The separation of different kinds of plastics molded together is not possible by flotation. 4.7.2.3 Sink–Float Separation Sink–float separation techniques are well-known wet methods for separation of mixed plastics, but are more suitable for separating plastics with large density differences. The sink-float method consists of the classification by density using a fluid medium, which allows the separation, up to a degree of 98%, of different plastic materials in a flow of mixed plastics (Plastic Zero 2013b). The separation of polyolefins (PE and PP) from other polymers can be very efficient (90–94%), making it more difficult to produce high purity outlets of specific types of polymers with similar densities, such as PS and PET (WRAP 2008). The plastic fractions separated with 90–95% of the target polymer are further refined to a purity level of 99–100% before being reprocessed. Figure 4.20 shows two images of a separation tank. The material is fed to the tank, especially designed separation plates and paddle rollers transport the material through the water quench, allowing a good separation result due to the long retention time of the plastic materials in the tank. In tanks for recovery of float fractions, the material discharge is handled by pneumatic valves, which open up intermittently to discharge the sink fractions. This discharge system is mainly used for small amounts of sink fractions. In cases of larger amounts of sink fractions, the discharge is handled by screws or scraper conveyors. In tanks for recovery of sink fractions, the material discharge is handled by oversized discharge screws. This method may show some disadvantages, because the surface activities of certain plastics particles are large enough that denser plastics rise up because of the effect of bubbles adhering to their surface and the effectiveness of the static density separation would be reduced as the plastic particles tend to stick together (Yuan 2015). Moreover, the separation would be impossible if two kinds of plastics are molded together.

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4.7.2.4 Hydrocyclonic Separation Hydrocyclones are applied in solid–liquid or liquid–liquid separation and use a centrifugal field as the basic separation principle and are used extensively given their simple design, low acquisition cost, easy operation, and low maintenance (Salvador et al. 2019). Hydrocyclones can be used instead of conventional separation tanks, allowing to achieve higher separation levels and exerting more friction on the material. The hydrocyclonic separation can be used for separation of waste plastics because of its characteristics of high G force and good dispersing action generated from the shearing effect of the internal flow (Yuan 2015). The shearing effect within hydrocyclones is of great advantage to disperse the plastic particles sticking together to improve the separation process. The waste will be fed to the hydrocyclone in the form of an aqueous suspension. The lightest fractions will be carried upwards, while the denser particles will end at the bottom of the cyclone. The light medium separation of two kinds of solids with density lower than water could also be made with hydrocyclones, using as light medium hollow glass beads in water. Unconventional hydrocyclones that meet the individual needs of each industrial process can be developed by altering the hydrocyclone geometry or by adding another operation to the hydrocycloning process (Salvador et  al. 2019). Hydrocyclones with hyperbolic or parabolic conical sections have a higher efficiency than those with conventional conical sections. However, the effectiveness of a hydrocyclone system is problematic for low-­ density plastic due to carry-over of liquid leaving with the underflow stream (Yuan 2015). Moreover, hydrocyclone separation can only handle binary plastics, and is also affected by particle sizes (Zhang 2019). 4.7.2.5 Multidune Separation Plastics recycling may be difficult as many types of plastic, each with different physical and chemical properties, may have very similar masses and many established methods of industrial separation may show problems and difficulties regarding separating plastics that have a similar mass. The multidune separator functions by transporting a mixture of plastic particles and fluid through a network of parallel semi-cylindrical transparent pipes (in perspex), using fluid dynamics to separate the plastics into outlets that correspond to their particular density, allowing to sort plastics according to their exact individual mass (De Sena 2008), allowing to differentiate even the smallest mass differences between plastic particles. Its high sensitivity allows the instrument to recognize plastic particles of an extremely small specific mass (1 g/cm3).

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4.7.2.6 Solvent Extraction It is possible to separate plastics by selective dissolution, using solvent-based separation processes. During this process, plastic waste is subjected to a series of purification steps using specifically selected solvents or a solvent preparation to separate the target polymer(s) with or without additives, keeping the polymers intact. The solid polymer which remains virtually unchanged by the process can be later reformulated into plastics using dissolution and/or remelting and/or compounding. The separation and recovery of plastics using solvents started by using xylene, because the solubility of plastics in this solvent varies with temperature, which serves as the basis of separation, applying steps of temperature (Yoon 1997). However, xylene is toxic and harmful to health, so that more environmentally friendly solutions were later developed. The “Fraunhofer Institute for Process Engineering and Packaging” has developed and patented the “CreaSolv®” process (Fraunhofer 2015), which allows a mixture of selected polymers to be selectively dissolved and thus separated from a stream of plastic waste, and for contaminants and hazardous materials to be effectively removed from the solution using special purification methods. The CreaSolv® process is suitable for the recovery of various thermoplastics, such as ABS, PS, EPS, PAc, PC, PLA, PVC, PET, PE, PP, and mixtures of these polymers, in complex post-consumption waste, like waste of electrical and electronic equipment (WEEE), low voltage equipment waste (ELV), construction waste, and mixtures of plastics (packaging waste). A special feature of this process is the option of separating certain additives from the recycled polymer, namely brominated flame retardants and plasticizers. Another similar process developed by Fraunhofer is “FiltraSolv,” suitable for recovering lacquered plastic or with electrodeposited coating (for example, galvanized plastics). In contrast to the CreaSolv® process, the residual plastic is treated with a small amount of solvent and, due to the low viscosity of the liquid mixture, it is then effectively filtered, extracting the polymer, and using most of the solvent containing the metallic coatings (Fraunhofer 2015). Due to the reduced use of solvents, the FiltraSolv process can be implemented using conventional plastic processing machines, such as an extruder with liquid filtration and vacuum degassing. Such a system would allow the swelling of the polymer, the filtration of electroplating metals, and the recovery of the solvent in a single line. Compared to solvent-­ based plastic recycling processes, the operating and investment costs for this process are considerably low. In selective polymers’ dissolution, multi-layered films or composites do not represent any problem, since this method can extract each polymer and fiber fraction subsequently using different solvents (Araujo-Andrade 2021).

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Some recent bibliographic references and standards classify this separation method as part of physical recycling,3 considering that most physical recycling methods are solvent-based methods.

4.7.3 Dry Separating Techniques for Separating Plastics 4.7.3.1 Generalities Generally speaking, dry gravity separation has the attraction of low capital input and operating cost which together with the lack of water, chemicals, and drying requirements means it is environmentally friendly. Thus, dry separation processes offer economical alternatives to wet separation processes. 4.7.3.2 Manual Sorting with Quality Control Despite the use of infrared separation equipment and other types of sensor-based separation equipment has replaced, over time, much of the manual separation work (Fig.  4.3), manual separation of mechanically or optically separated recyclable materials is, however, still widely used in different applications, to ensure sufficient purity (between 96% and 99%, depending on the type of material). Typical applications are called positive or negative (Plastic Zero 2013b): –– As a positive sorting, for separating large objects, such as 2D plastic films, from other recyclable mixed plastics. This application appears as one of the first operations in a central sorting installation or for separation in the larger fraction after passing through the drum screen. –– As a negative sorting, to remove undirected materials from single source waste streams. Undirected materials can be impurities or types of non-certified packaging waste (in producer responsibility systems). This action can also be called quality control of the output materials in order to obtain sufficient purity for a given purpose. The ability to manually classify depends a lot on the actual objective (positive or negative classification) and the accuracy of the classification, as well as the type of material to be separated. For example, a person has a lower income (in kg/h) separating smaller plastic items than larger and heavier ones.

 Process in which a plastic undergoes a series of purification steps to separate the target polymer(s) from other polymers, additives, and other added materials such as fibers, fillers, dyes, and contaminants, resulting in recovered polymers, which remain largely unaltered by the process and can be reformulated into plastics. This process may also allow for the recovery of other valuable components from the plastic (according EN 17615–2021) 3

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In this type of separation, occupational health and safety issues are important. Mitigating measures for acceptable occupational health and safety broadly include the following interventions: –– –– –– –– ––

Effective ventilation of workplaces. Use of protective gloves, masks, etc. Frequent intervals of manual sorting activities. Change of workplace. Frequent medical check-up.

The productivity of manual sorting is low and is only suitable for plastic mixtures which have obvious external differences and the separation of different kinds of plastics is impossible if they are molded together. 4.7.3.3 Dimensional Separation The dimensional separation equipment divides the recyclable waste that is fed into the stream, according to the individual dimension of the waste (Plastic Zero 2013b). The equipment typically used for these screens (drum screens, vibrating screens, or other screens) and air classifiers. The materials fed into the entrance of the dimensional separation screen equipment are generally made up of mixed waste, such as mixed recyclable packaging waste. Dimensional separation equipment is usually the first primary classification, and may or may not occur after crushing. Typically, the separator divides the waste into three fractions: –– Small size: < 50 mm. –– Average size: 50–300 mm. –– Large size: > 300 mm. Plastics usually appear in medium- and large-size fractions. Medium-sized 2D and 3D waste will normally be classified later in a ballistic separator and, eventually, also in an air classifier (for instance see paragraph a) below). The large-sized fraction normally passes to a manual sorting booth, for selecting large-sized 2D plastic films (Plastic Zero 2013b). 4.7.3.3.1  Air Classifiers By this method, the separation is carried out according to the variation of the “speed of falling materials” in an air flow. The use of air classifiers in the separation of mixed plastics can be limited due to a small density differential between plastics to be processed. Thus, the main objective is to separate the light and heavy parts of the waste stream, as well as to separate the particles in different range sizes. The air classifier

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is especially suitable for separating 2D plastics from heavier materials (3D plastics and other materials/impurities). There are different types of air classifiers that can be used in waste sorting installations. Air classifier designs are wide and the choice of the classifier type and designs is dictated by the technological requirements and the properties of materials to be classified. The air classifier types and designs are the following (Shapiro and Galperin 2005): –– –– –– ––

Gravitational air classifiers. Cascade air classifiers (known as Zigzag classifiers). Fluidized bed classifiers (single-stage, two-stage, or continuous operation). Inertial air classifiers (Franken/Buell gravitational-inertial classifier, vortex classifier, gravitational–centrifugal classifier). –– Centrifugal air classifiers (vortex air classifiers, rotor classifiers, gravitational– centrifugal air classifiers, circulating air classifiers). The air classifiers may have vertical or horizontal air streams and multiple classifiers can be used in series to produce products in multiple particle size ranges. Vertical air classifiers need to be connected with a device (commonly a cyclone) in order to subsequently separate the low-density fraction entrapped in the air stream from air. These air classifiers require a large working space (because of their considerable height) and are not an answer where the space is key feature (Dodbiba and Fujita 2004) and, in certain circumstances more compact devices, with a simpler geometry, are preferable. 4.7.3.3.2  Star Screens and Ballistic Separators The disk screen consists of a series of driven shaft assemblies mounted on a frame. Each rotor shaft assembly has profiled disks mounted at regular spacing. The disks on one shaft intersect with those on the adjacent shafts, creating open areas between the disks and the shafts. Incoming material is fed into one end of the screen. The sets of axes rotate, the disks shake the material and move it across the screen. Pieces of material smaller than the spacing between the discs and shaft assemblies fall across the screen. Pieces larger than the openings are transported along the top of the discs and pass through the end of the screen. A ballistic separator (or ballistor, Fig.  4.7b) is similar to a conventional disc screen, but showing advantages over a conventional disc screen, due to reduced wear parts replacement and much lower labor costs related to cleaning. It consists of a perforated vibrating platform equipped with replaceable screening plates that are used to filter material of a certain size as determined by the application. It is used to separate out usable fractions from waste and potential recyclables and it allows to configure a separation into three or four fractions, several size ranges, and different geometry options.

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A slight inclination in the tray causes heavy materials to fall to the lowest level of the tray, while lighter materials, such as plastic sheets, are transported upwards. Thin materials fall through the perforated bottom. The classification is done automatically according to size, density, and rigidness, resulting in three fractions: –– Light fraction (non-heavy and flat parts, with 2D format). –– Heavy fraction (non-light parts and with 3D format). –– Fine fraction (for example, less than 20 mm in size). By changing the inclination of the separation tray, the performance of the separator can be adjusted. Considering the separation of plastic, this separation equipment is applied to separate the 2D and 3D plastic materials, as well as to separate the main non-plastic materials. In the 2D ballistic separator, the plastic will appear in the light fraction (along with other 2D light materials, such as paper, cardboard, and textiles). This light fraction will need one or two more classification steps to separate the plastic from the paper and cardboard, which can be done using an airflow classifier. 3D plastic materials will appear in the heaviest 3D fraction, along with other heavy 3D materials (wood, leather, glass, metals). This heavy fraction will need one or two more sorting steps to separate the plastic. Metal can be separated using metal sorting equipment. By combining ballistic separation with screening, separation is performed in one operation in accordance with the criteria three/two-dimensional, rolling-cubic-rigid/ flat-soft-narrow, or undersized/oversized particles. 4.7.3.3.3  Cyclone Separators A cyclone separator uses a centrifugal field as the basic separation principle and is considered a high-efficient waste plastic sorting equipment, mainly for easy separation of fine and finest particles. The particle-laden air stream enters the separator tangentially at the top, creating a rotating airflow (vortex). By centrifugal force, the particles are moved along the outer wall, where they are separated and, in a spiral motion, deposited to the final collection point. At the bottom of the box, the airflow is forced to reverse and flows upward through the vortex. Density separation of waste plastics with cyclones is a low-cost, highly efficient process to recycle plastics either for direct use in manufacturing or to prepare fractions for subsequent treatment with other processing methods. Key parameters affecting the efficiency are the length of the separator, the length of the overflow pipe, and the diameter of the discharge opening. The cyclone separator also facilitates the pneumatic transportation of product between certain equipment and also performs a dedusting of the air flow. Figure 4.28 shows a recycling unit equipped with vertical air stream cyclones.

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Fig. 4.28  Photo of a separation system equipped with two vertical cyclones, the left feeding an automated double big-bag packing unit and on the right side one feeding an automated buffer bunker. (Image courtesy of B + B Anlagenbau GmbH)

4.7.3.4 Optical Separation As macroscopic physical methods, namely those that use density measurements, are not sufficient to efficiently separate the various types of plastics, and because the hand-sorting is labor-intensive and costly, identification of plastics has been done with methods of monitoring structural or molecular properties of the constituent polymers. Thus, many different types of automatic plastics sorting systems for the identification, characterization, and analysis of plastics, based on optical spectroscopies, have been developed. Current technologies use equipment equipped with a sensor or a series of optical sensors to identify different objects. The signal from a multidetector system is

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processed by a computer, equipped with software that sends signals that trigger air jets to remove the identified object from the feed stream and eject it by resin type and color into separate containers. This blow-out of particles from the feed stream, performed by air nozzles, requires that objects have previously been subjected to size reduction processes and the particle size of such processes is decisive for the sorting outcome (Araujo-Andrade 2021). These technics allow the separation of materials such as paper, cardboard, wood, glass, electrical and electronic components, minerals, and plastic materials (such as PET, HDP, LDPE, PP, PVC, EPS, HIPS, and ABS), as well as different colors (except black colored items, that cannot normally be separated due to their lack of reflective ability). Optical separation can also be used to separate two-dimensional articles (of low thickness) from three-dimensional articles. Although these techniques utilize different physical phenomena, they can be grouped into two general categories: molecular spectroscopies and atomic/elemental spectroscopies (Araujo-Andrade 2021). Molecular spectroscopies are generally non-destructive and most of them use low-energy excitation sources (Araujo-Andrade 2021). They provide information related to the spectral signature of the materials (molecular identity, conformation, and/or structure), and include Raman spectroscopy (RS), Fourier-transform infrared spectroscopy (FTIR), near-infrared spectroscopy (NIRS), visible spectroscopy (VIS), and terahertz spectroscopy (THz). Atomic spectroscopic techniques commonly use high-energy radiation sources to provide information about the atomic or elemental composition of a sample (Araujo-Andrade 2021). The specificity of these techniques is low when compared to molecular spectroscopies and materials with similar elemental composition will give similar or identical spectra, limiting the applications in sample discrimination/ classification. They can be used as a complement to the previously discussed techniques, for example, to identify all components in organic–inorganic composites such as polymers with flame retardants or inorganic fillers. The most common techniques in this class are X-ray fluorescence spectroscopy (XRFS) and laser-induced breakdown spectroscopy (LIBS). The generality of commercial solutions for monitoring and/or sorting plastics using photonic techniques are based on Vis-NIR spectroscopy and HIS and are available in different versions, depending on its mainstream capacity and sorting capabilities. In specific applications, the systems may combine Vis-NIR and XRFS or enable the combination of up to three sensors for detecting contaminants or yet use MIR to sort black and dark plastics (Araujo-Andrade 2021). 4.7.3.4.1  Raman Spectroscopy Measurement by RAMAN spectroscopy is based on the interaction of laser light with a flow of plastic material in a preconditioning unit (PCU) of the recycling extruder.

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Unlike FTIR, RS is more sensitive to the molecular structure (electronic bonds) than functional groups and in this sense, both have been treated as complementary techniques. RS is suitable for all thermoplastics and types of fillers, but is not suitable for the analysis and characterization of black plastics, since Vis-NIR light is highly absorbed by the black carbon commonly present in black plastics. 4.7.3.4.2  Fourier-Transform Infrared Spectroscopy (FTIRS) FTIR is a vibrational spectroscopy that works in the mid-infrared (MIR) region, allowing rapid determination of high-resolution spectra in a wide spectral range (4000–400 cm−1). Different bonds in a molecule vibrate at different energies, and therefore absorb different wavelengths of the IR radiation. The frequency and intensity of these individual absorption bands, related to the atom-to-atom vibrational bond energies in molecules, contribute to the overall spectrum, creating a characteristic fingerprint of the sample under study. Since the MIR region is beyond the visible range, colored and black plastics do not pose a problem for analysis, unlike NIR and Raman spectroscopies. This technology is used for sorting applications in the form of a mid-infrared hyperspectral imaging system (MIR-HSI). Hyperspectral cameras working in the MIR region (approximately 3500–2400 cm−1) available in the market for recycling applications, includes (a) a sensor for the MIR range, (b) a wideband light source, (c) a spectrometer, which separates backscattered/transmitted light into its different wavelengths and, when necessary, (d) a conveyor belt, synchronized with the recording frame’s rate of the sensor for scanning the sample (Araujo-Andrade 2021). Four basic modes for HSI measurements can be performed depending on the application, with in-line scanning being the best choice for in-line applications, where sample can be transported by belt, or where the scan head can be automated (Araujo-Andrade 2021). 4.7.3.4.3  Near-Infrared Spectroscopy (NIRS) Unlike the fundamental modes of molecules in the MIR region, the absorption spectra in the NIR region (750–2500 nm) are composed of overtones and the combination and overlapping of broad bands. Also, the strength of the NIR signal is much weaker than the signal in the MIR region. However, the N-H, O-H, and C-H atomic bonds strongly absorb radiation in the NIR wavelength range, making this technique an excellent tool for the study of organic compounds. In the near-infrared spectroscopy (NIRS), plastic is classified by types of polymers and colors by means of optical classification technologies based on near-­ infrared (NIR) cameras. The chambers are adjusted to detect certain properties, such as types of materials, types of polymers, or colors. The infrared sensors identify the materials by their specific wavelength, which are subsequently separated

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into different compartments by the action of air jets, so that any piece of unidentified material is thus ejected from the conveyor belt (Plastic Zero 2012). Figure 4.29 shows a NIR spectrometer DAGS which was constructed from department ES of Fraunhofer ICT in 1997, which was installed in sorting lines for detection of bottle polymers (mainly PET and PVC). The spectrometer was a diode array system and could measure up to 20,000 spectra per second (that was world record in 1997). Latest NIR spectrometer systems can measure up to 50,000 spectra per second. Current NIR-HSI technology is widely used for sorting of solid plastic waste monitoring applications and most of the modern plastic sorters in-line are equipped with hyperspectral cameras (Fig. 4.30), which current setup includes (a) a broadband excitation source (which is usually a halogen light with a tungsten filament, (b) a spectrometer, and (c) a semiconductor photodetector, generally made of an alloy of InGaAs, complemented with significant computing capacity and software for data analysis using advanced multivariable methods (Araujo-Andrade 2021). The NIR system can be optimized with the use of a focal plane matrix (FPA) detector, for remote and online measurements on a macroscopic scale. This technology is normally applied to the separation of: –– –– –– ––

Polymers, by type, in mixed plastic streams, including PLA-based bioplastic. Wood and textiles. Paper, cardboard, and packaging. PVC in undefined waste streams.

The “Wrap Recycling Action Program” (WRAP) conducted tests of NIR technology to separate mixed plastic packaging (WRAP 2008). The test results show a purity of 87% for polystyrene and 93–96% for other types of plastic (PVC, PE, PP, PET) and 97% for bioplastic PLA.

Fig. 4.29  NIR spectrometer DAGS (1997). (Image courtesy of Fraunhofer Institute for Chemical Technology)

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Fig. 4.30  Automated NIRS sorter, allowing to detect the chemical composition in plastics, as well as black and dark objects. (Image courtesy of STEINERT GmbH)

Fig. 4.31  Spectral records obtained by NIRS technology, showing characteristic harmonic or combination vibrations of various plastics (Wu 2020)

It is also possible to classify a polymer of a single color, with approximately 90% purity (but this will require several optical units for each polymer or recirculation flow). Figures 4.31, 4.32, and 4.33 show separated and overlapping NIRS spectra from two different sources of plastic sorting. Figure  4.33 includes also a reference to three different spectral ranges according to the model of the spectrometer used. However, the NIR classification technology has some limitations. The main weaknesses are:

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Fig. 4.32  Average NIRS spectra of each kind of plastic (Zhu 2019)

Fig. 4.33  Spectral records obtained by NIRS technology, showing spectra of different plastics. (Image courtesy of LLA Instruments, Germany. All rights reserved LLA Instruments GmbH & Co. KG Germany)

–– When articles contain more than one type of material or plastic (for example, label, laminated products) they may not be recognized correctly by the NIR sensor. –– Fillers, plasticizers, dyes/pigments, and other additives influence the shape of the spectra of plastic materials. Thus, for example, carbon black absorbs all light and

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even small amounts (> 0.1%) reduce the reflection or transmission of NIR light to levels that are not sufficient for identification. Therefore, the colored parts containing carbon black are not identified, so they will subsequently remain in the residual flow.4 –– When the article is inside another, it is not identified. –– Dirty objects are not recognized if the light cannot be reflected. 4.7.3.4.4  Visible Spectroscopy (VIS) This technology is based on automatic optical classification using cameras to identify the color of materials (in the visible spectrum) by means of photographic recognition (Figs. 4.23 and 4.24). The materials are subsequently distributed to different compartments through the action of air jets. Although less used than NIRS technology, the costs of both technologies are similar, so its use is expected to increase in the future to improve the efficiency of separation, as well as the quality of the separated materials (Plastic Zero 2013b). The online colorimetry equipment includes: –– –– –– ––

A vibrating feeder. A camera. A light source. A pressurized air rejection unit.

The inline colorimetric chamber is normally applied to separate different colors of plastic products (for example bottles, films), waste electrical and electronic equipment, glass, and minerals. The inline colorimetric camera (Fig. 4.23) is also capable of separating waste paper (magazines, newspapers, cardboard packaging, etc.), determining the lead content in the glass, separating bottle caps (3D camera), and separating black plastic. 4.7.3.4.5  Terahertz Spectroscopy (THz The terahertz spectroscopy (THz) imaging provides a unique combination of high contrast imaging, high spatial resolution, and safety, making it an alternative to some tomography and imaging technologies (Araujo-Andrade 2021). Since some black plastics cannot be sorted using conventional optical sorting systems, THz technology can help in identifying different polymeric resins as well as black plastics. In spite of THz being commercially available, no industrial use has yet been identified in mainstream polymer sorting (Araujo-Andrade 2021).  Some black pigments have been developed for NIRS detection (see Sect. 2.6.4.1). The solution is not to absorb at the near infrared wavelength and to allow classification systems, which are based on reflective or transmission sensors, to properly identify the different polymers. 4

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4.7.3.4.6  X-Ray Fluorescence Spectroscopy (XRFS) The XRFS is a high-energy spectroscopy that allows to recognize the elemental composition and distinguish different materials, by analyzing the X-ray radiation emitted (fluorescence) by electron movements, through a X-ray spectra in the wavelength range from 10−3 nm to 10 nm, resulting from the interaction between the incident X-ray radiation and the target material. XRFS is a high-energy spectroscopy that allows recognizing the elementary composition and distinguishing different materials, through the analysis of the emitted X-ray radiation (fluorescence), by means of electron movements, resulting from the interaction between incident X-ray radiation and the target material. The X-ray fluorescence (XRF) is characteristic for each element and specific for each electronic transition, illustrated by an X-ray spectrum in the range of wavelength from 10−3 nm to 10 nm. The XRF technique is useful for qualitative and quantitative analysis of inorganic materials, metals (copper, brass, stainless steel, aluminum, and zinc), regulated heavy metals (lead, cadmium, mercury, and chromium), flame retardants or other additives containing halogens (bromine and chloride) or antimony or phosphorus. XRF can also be used to identify aluminum layers in multi-layered packaging and silicon in glass fiber-reinforced plastics. Therefore, XRF can be used both as a: (a) process control tool to evaluate the presence of these agents in the finished product; and (b) sorting tool for the process of plastics’ recycling. Figure 4.34 shows a set of X-ray transmission devices mainly used for separation of pure aluminum. Currently, X-ray fluorescence separation is not widely used in the separation of mixed plastic waste, because this technology is not able to distinguish between polymers. However, an automatic sorter using an X-ray fluorescence (XRF) analyzer can detect PVC and eject them from a plastic stream (for example, from PET). Thus, this technology may be promising for portable operating spectrometers applied to larger plastic parts in the course of manual dismantling at the beginning of a recycling line. 4.7.3.4.7  Laser-Induced Breakdown Spectroscopy (LIBS) The laser-induced breakdown spectroscopy is mainly used to sort aluminum scrap by alloy type. This technology allows the alloy elements to be determined and quantified with precision thus permitting a distinction to be made between a large number of different alloy types. Alongside the LIBS unit, the sorting machine can also be equipped with 3D detection to capture a high spatial resolution of the object form (Fig. 4.35). LIBS can also be used for the sorting of waste of electrical and electronic equipment (WEEE), which is technically complicated due to the mixture of metals and variety of polymers (such as ABS, PC, PC-ABS, PA, PMMA), as well as eventual regulated additives contained in WEEE products.

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Fig. 4.34  Set of X-ray fluorescence devices used for separate aluminum. (Image courtesy of STEINERT GmbH)

This technology is able to identify aliphatic and aromatic polymers, based on spectral lines of oxygen, carbon, and hydrogen (Araujo-Andrade 2021). Using elemental lines of bromine, chlorine, silicon, or carbon, LIBS can also be used for the analysis of flame retarded plastics, halogenated plastics, and for fiber-­ reinforced plastics (Araujo-Andrade 2021). 4.7.3.5 Separation Based on Electrostatic and Magnetic Properties 4.7.3.5.1  Electrodynamic Separation Electrodynamic separation consists of three stages (Lyskawinski 2021): –– In the first stage, the polymer waste is shredded into fractions with dimensions not exceeding a few millimeters. –– The second stage consists of electrifying particles of plastics by the corona discharge or in cylindrical mixers, shaking conveyors, or fluidized beds using the contact-friction method, resulting in the creation of electric charges on the surface of the mixture components. –– In the third stage, the mixture is separated in a strong electrostatic field depending on the size and polarity of the electrostatic charge accumulated on the surface of the separated polymer material.

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Fig. 4.35  Line Sorting System LIBS. (Image courtesy of STEINERT GmbH)

The formation of electric charges by this process is a consequence of the contact between surfaces of two solids and occurs due to their mutual friction by sliding, rolling, impact, vibration, or deformation. As a result of the electrification of particles of mixed plastics in the contact-friction process, positive and negative electric charges accumulate on the surface of the plastics (Lyskawinski 2021). However, the effectiveness of the electrostatic separation of PVC from PET fractions may be reduced because the plastic particles tend to stick together (Yuan 2015). Corona electrostatic separation can separate metallic particles (0.2–1 mm) from non-metallic particles; however, the separated particles are difficult to collect, because it is almost impossible to calculate their moving trajectories (Zhang 2019). 4.7.3.5.2  Magnetic and Eddy Current Separation Magnetic and eddy current separation is a technology that uses electromagnetic and permanent magnetic properties of the materials to separate magnetic iron and non-­ ferrous metals (for example, aluminum). The magnet is capable of separating ferromagnetic parts from other non-­ ferromagnetic materials, but does not allow separation of stainless steel and other no ferrous metals. The equipment is installed parallel or perpendicular to the feeding belt (Fig. 4.4a).

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The eddy current5 separator (Fig. 4.4b) is applied to separate non-ferromagnetic metals, such as aluminum, copper, magnesium, and silver, and is not effective in separating zinc, brass, and tin, as well as alloyed steels. It allows to separate non-­ metallic parts and non-ferrous metals from ferrous metals (Plastic Zero 2013b). This equipment can be installed on a line containing other equipment, such as an X-ray sorting system (Fig. 4.36). Eddy current is often used in waste electrical and electronic equipment (WEEE) separation, to recover non-ferrous metallic particles (2–10 mm). Both techniques are only applied to separate good conductors (such as metallic particles, etc.) from dielectrics and thus they can be also employed to separate plastic particles from a metal/plastic mixture. However, they are unable to separate a mixture of dielectric particles such as mixed plastics (Dodbiba and Fujita 2004).

Fig. 4.36  Line containing an eddy current separator and an X-ray separator in series, regarding the separation of aluminum. (Image courtesy of STEINERT GmbH)

 Localized electrical current, induced in a conductor by a variable magnetic field.

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4.7.3.5.3  Triboelectrostatic Separation Triboelectrostatic separation is a kind of electrostatic separation that utilizes frictional charging. This technology utilizes the difference between surface properties of different materials to get them oppositely charged, deflected in the electric field, and separately collected (Wu et al. 2013) and it is the technique most frequently used to selectively separate two solid species of dielectric materials (Dodbiba and Fujita 2004). This technology requires a pre-treatment, consisting of dimensional reduction and charging. When two dissimilar non-conducting particles come into contact, charge is transferred; one of the particles becomes negatively charged and the other positively charged. The charge polarity is determined by a triboelectric series (PTFE, PVC, PE, PP, PS, PET, Acrylic). Any polymer higher in the series in contact with one lower in the series will charge negatively. For example, PE will charge negatively in contact with PET, but will charge positively in contact with PVC (Brown 2000). This technology has advantages such as high efficiency, low cost, no concern of water disposal or secondary pollution (no toxic or polluting chemicals) and a relatively wide processing range of particle size especially suitable for the granular plastic waste. First, plastic waste is usually crushed to the optimum size range by cutting mills or shredders. Sieves are usually needed for classification. The suitable particle size for triboelectrostatic separation varies from device to device. It has been reported that the triboelectrostatic separation method is effective for the particles of size in the range of 1–13 mm (Wu et al. 2013). Rub can be used to increase the charge transfer between the granular plastics to several orders of magnitude greater than in a simple touching contact. Because the plastics are insulators, the electric charge will be accumulated with repeated rubbing, but tribocharging only happens on the surfaces of the particles, as deep as 30 nm as for polymers (Wu et al. 2013). After the crushing and screening step, plastic waste is supposed to be in a suitable range of particle size for the charging purpose, which can be done by several ways (fluidized-bed, vibration, rotation, high-speed air stream). When using a rotating drum triboelectric separator, chopped dry particles (5–10  mm size) of mixed plastics are fed continuously into the upper end of a slightly tilted, slowly rotating drum, comprised of a cylinder with rotary blades, whose form was adapted to enhance mutual friction between plastic pieces. As the particles tumble over each other they become charged, due to the many and repeated contacts. The quantity and polarity of the charge on each particle depends on the contacts with other particles. Because of the tilt of the drum, the particles migrate to the exit end of the drum where they fall through a strong horizontal electric field. The negatively charged particles are drawn toward the positive electrode while the positively charged particles are drawn toward the negative electrode (Dodbiba and Fujita 2004; Brown 2000). For mixtures of more than two plastics, more than one pass through the process is required. In the first pass for any mixture, one plastic will be the dominant

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positive charging species while another will be the dominant negative charging species. These will be drawn toward the electrodes and fall in the side bins. The others will be relatively uncharged and tend to fall in the center bin. If the material in the center bin is re-run through the process, the charging of the particles will be quite different since the mixture contains a very different set of plastics. Thus, in the new mixture a different pair may be the dominant positive and negative charging species. As a consequence, very complex mixtures can be separated into pure components by a sequence of passes (Brown 2000). An alternative device that can be used for charging, is the triboelectric cyclone separator, that produces a higher frictional speed (Dodbiba and Fujita 2004). It is also reported that the cyclone separator can be effective for plastic particles of size in the range of around 150 μm (Wu et al. 2013). The required complex pretreatments for triboelectrostatic separation, such as rubbing surfaces and collision, to charge the objects that are to be separated, might not be economically viable for some waste management scenarios (Zhang 2019). 4.7.3.5.4  Magnetic Levitation Magnetic levitation or “MagLev” is based on a configuration with two identical square magnets like-poles facing each other (Zhang 2019). The plastic particles mixed and immersed into paramagnetic medium are placed into a magnetic levitation configuration that can levitate particles of different densities at their corresponding balanced positions; this process is free from the limit of sizes, as mixtures of different size fractions reached their respective equilibrium positions, therefore being widely applied in density measurement. The method has economically viable, environmentally friendly, and the paramagnetic medium that can be reused indefinitely (Zhao 2018). 4.7.3.5.5  Magnetic Projection The method, still in its infant stage and requiring potential future research, is inspired by MagLev and aims at separating multiple mixed particles, without energy supply, reagent input, and particle size restrictions (Zhang 2019). It is based on a simple configuration: a container full of paramagnetic medium is placed beside a permanent magnet. Particles of different densities that submerge in the medium are driven by the magnetic force, moving in accordance with different trajectories, and are finally landed in different collection regions. The magnetic force is no longer employed for levitation, but is exploited to project the diamagnetic objects, i.e., the particles to be separated, in the solution to desirable landing zones (Zhang 2019).

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4.7.3.6 Thermal Treatment As heating plastics change their properties, a method of separating plastics from others can be made after a thermal treatment, using a separator consisting of an electrically heated cylinder enclosed within a hollow rotating tube fitted with vanes to ensure a tumbling action about the heated cylinder. The plastics melting on the healed cylinder is removed by blade, and then discharged. The heater discharge can also be fed to a cyclone and then to an air classifier to separate a material overflow from the plastics underflow (Yoon 1997). However, the melting separation process is not recommended, because it would produce toxic ingredients as plastics are heated and broken down (Yuan 2015).

4.8 Innovations Along the Separation Process of Plastics To achieve a high level of purity, some advanced plastic waste sorting techniques currently involve “machine learning,” a process through which a machine is trained to recognize different types of plastics and other materials. For example, machine learning is currently applied to sort plastic waste WEEE, such as ABS, HIPS, PP, and PS. It is especially useful for sorting dark plastics that are difficult to identify using near-infrared techniques due to radiation absorption (OECD 2019). Blockchain digital technologies, which allow detailed tracking and verification of information, namely access to validated data on the source of waste, type, color, quantity, origin, and classification process, in order to reduce uncertainty about the quality of plastics sorted and recycled (OECD 2019). To reduce the release of microplastics and microfibers during the washing of plastic and textiles and ensure their retention for later disposal, filter washing bags have been created.

4.9 Quality of Recycled Materials 4.9.1 Objectives The options for using recycled plastic depend on the quality and homogeneity of the polymer, because the properties of the materials are the main concerns of the market. Factors influencing the value of the recycled material are the type of polymer, the color, the degree of transparency, and the purity. A clean, contaminant-free source of a single polymer from recycled plastic waste has more end-use options and greater value than a mixed or contaminated source of plastic waste (Plastic Zero 2012).

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An important objective of the recycling industry is generally to maintain, for a recycled plastic material, the same application as the one it had, as this way it is easier to take advantage of the properties of the polymer and its additives and, consequently, respect the legal requirements of these products. Thus, in the collection and sorting stage, it is important to obtain a pure flow of one or two polymers for recycling. The inefficient sorting means that the mixed plastic material is not recycled or is recycled in a downward cycle. In addition, plastic waste must be clean, non-plastic materials must be removed and contamination must be eliminated.

4.9.2 Constraints and Influencing Factors Homogeneous streams of plastic waste are not easy to obtain. Although mixed plastic systems are cheaper, the separation of different polymers depends on the applicable technologies, which are still not perfect, although they are constantly evolving (Plastic Zero 2012). Rigid black plastic materials continue to be a challenge to identify and positively classify, as carbon black dyes prevent the plastic from being detected by optical selection equipment. As a result, black plastic often ends up in the residual flow of rejected materials (WRAP 2012). Some polymers also find it easy to undesirably mix, as, for example, it happens between PVC and PET (cross-contamination). Most of the current sorting technologies are based on automated systems. These apply to waste streams that have undergone a pre-treatment to define a specific particle-size range, otherwise the subsequent separation process will not be efficient enough. But, other than that, failures in automated optical sorting may occur by incorrect identification but also if the air nozzle emits more than the targeted items or if a blown-out particle hits another one, which is then falsely separated. The definition of the restriction range of the classification parameters can also influence the results obtained in the sorting process, which must depend on the position of automated sorting systems in the value chain. When applied to the initial screening of mixed shredded plastics, it does not make sense to apply too strict sorting parameters, in order not to lose target material in the rejected fraction (Araujo-­ Andrade 2021). If, however, automated sorting is applied at the end of a recycling process cascade, purity rather than yield is decisive. In this case, it is better to reject all particles that do not show the typical photonic pattern of the target material and that non-identified fractions may be circulated several times to increase the ability to identify them.

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4.9.3 Quality Assessment. Normalization There are two main groups of technical specifications and standards that can be applied to plastic waste for recycling. The first category deals with the phase between the collection and reprocessing of plastic waste. The second category of standards is directed mainly at recycled plastics and final products, and characterizes the plastic material in the secondary raw material stage, for example, for re-granulate and “pellets, after reprocessing (Plastic Zero 2012). Table 4.1 lists the most commonly used normative documents in Europe for assessing the quality of recycled plastics.6 The standard EN 15347, belonging to the first category of standards referred to above, aims at the characterization of plastic waste, establishing the specifications on plastic waste, that is, input material for reprocessing and for some types of conversion, and the specifications for waste plastic-based intermediates (for example, re-granulated), which are materials for reprocessing output, and which are used as input for the manufacture of final products (Table 4.2). The EN standards for specific recyclates, indicated in Table 4.1, define the quality requirements for a specific recycle (which may be mandatory or optional), as well as the relevant test procedures. In practice, more specific requirements can be agreed, as usually the buyer’s specifications involve more stringent quality requirements, and the testing responsibility is, generally, with the reprocessor. The reliability of the manufacturer’s laboratory is often supported by a quality certificate provided by an external organization that certifies and conducts external audits. Still on this topic, it is important to highlight that CEN (“European Committee for Standardization”) and Technical Committee 350 of CENELEC (“European Committee for Electrotechnical Standardization”), responsible for standardization related to the sustainability of construction works. Recently created a new subcommittee called “Circular economy under construction,” whose work program includes a consistent digitization strategy, with a scientific and reliable basis, and which should introduce changes to the standards already developed by the CT 350. The new subcommittee will also have the task of combining the guidance developed by the ISO 323 technical committee (“International Organization for Standardization”) with that provided by the CEN Technical Committees (TC 351, which deals with hazardous substances, and the various CEN committees responsible for the standardization of construction products), also taking as a reference the European Commission’s circular economy strategy.

 It is worth noting the fact that a future standard is already being developed, establishing the quality requirements for the application of recycled plastics in products of different polymers, subdivided in parts (1 – General; 2 – PE; 3 – PP; 4 – PVC; 5 – PET; 6 – PS; 7 – PA; 8 – ABS; 9 – PC). 6

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Table 4.1  Regulatory documents most used in Europe for recycled materials Regulatory documents and standards EN 13430:2004 CEN/TR 13688:2008

CEN/TS 14541:2013a EN 15342:2007 EN 15343:2007 EN 15344:2007 EN 15345:2007 EN 15346:2007 EN 15347:2007b EN 15348:2014c CEN/ TR 15353:2007 EN 13430:2004 EN 13437:2003 EN ISO 16103:2005 ISO 15270:2008 ISO/TR 23891:2020 ISO 17088:2021 EN 17615:2021d

Title Packaging—Requirements for packaging recoverable by material recycling Packaging—Material recycling—Report on requirements for substances and materials to prevent a sustained impediment to recycling Plastics pipes and fittings—Characteristics for use of non-virgin PVC-U, PP, and PE materials Plastics. Recycled plastics. Characterization of polystyrene (PS) recyclates Plastics. Recycled plastics. Plastics recycling traceability and assessment of conformity and recycled content Plastics. Recycled plastics. Characterization of polyethylene (PE) recyclates Plastics. Recycled plastics. Characterization of polypropylene (PP) recyclates Plastics. Recycled plastics. Characterization of poly (vinyl chloride) (PVC) recyclates Plastics. Recycled plastics. Characterization of plastics waste Plastics. Recycled plastics. Characterization of poly (ethylene terephthalate) (PET) recyclates Guidelines for the development of standards relating to recycled plastics Packaging. Requirements for packaging recoverable by material recycling Packaging and material recycling. Criteria for recycling methods. Description of recycling processes and flow chart Packaging. Transport packages for dangerous goods. Recycled plastics material Plastics—Guidelines for recovery and recycling of waste plastic Plastics. Recycling and recovery—Necessity of standards Plastics. Organic recycling—Specifications for compostable plastics Plastics—Environmental aspects—Vocabulary

CEN/TS 14541 is under revision and a new version should be published in 2022. It should be subdivided in 2 parts: Plastics pipes and fittings—Utilisation of thermoplastics recyclates—Part 1: Vocabulary; Part 2: Recommendations for relevant characteristics. The part 2 of this standard refers to characteristics of PVC-U, PVC-C, PE, PP an ABS polymers and also already includes the new test for PVC-U, PP and PE recyclates with CRB-method b EN 15347 is under revision and a new version should be published in 2022 c EN 15348 is under revision and a new version should be published in 2022 d EN 17615 is under revision and a new version should be published in 2022 a

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Table 4.2  Quality requirements set out in EN ISO 15347 Property Lot size Color Recycled shape History of recycled Main polymer present Other polymers present Recycled packaging type Impact resistance Charpy or Izod

Test method Required (weight or volume) Mandatory (visual assessment) Required (for example, flakes, film, or bottle) Mandatory (EN 15343) Mandatory (percentage by weight, if known) Mandatory (percentage by weight, if known) Required Optional (EN ISO 179-1 and EN 179–2 or EN ISO 180) Melt flowy index Optional (EN ISO 1133) Vicat softening temperature Optional (EN ISO 306 method A) Additives, contaminants, water content Optional Ash content Optional (EN ISO 3451-1) Humidity Optional (EN 12099) Tensile strength and elongation at Optional (EN ISO 527, parts 1 to 3) break Volatile content Optional (weight loss at a given processing temperature)

4.9.4 Destination of Rejected Materials The quantity and quality of materials discarded in recycled separation and sorting facilities, equipped with highly advanced automated classification equipment, depend, among others, on the following factors (Plastic Zero 2013b): –– –– –– ––

Quality of entry. Criteria and specification for the output materials. Technical design of the sorting installation. Market for products (recyclable materials and other fractions).

There is little information available on the quantity and quality of the rejected materials, and what exists should be seen in a local context, as each country has its own methodologies. There are countries that only separate certified waste, the rest being incinerated or landfilled, and others where actual recycling depends more on the market situation and options.

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4.10 Reprocessing Reprocessing consists of the production of recycled materials in the form of granules, ground powders, pieces, agglomerates,7 and compounds,8 from an inlet of plastic waste. However, the process can also be extended and involve the extrusion of profiles or, more simply, the pelletizing of the plastic at the outlet. The granules (“pellets”) are sold as a final product, for use as a raw material, in a new production. The reprocessing of the plastic material (fine sorting and production of secondary raw material) usually occurs after the initial sorting and the separation of mixed waste from plastic streams or directly into industrial plastic waste.9 For high-quality plastic products, the input for the production of secondary raw material is often made of plastic of a single material (for example, PET or PP), with no or little amount of contaminants and unwanted plastic materials. For plastic products of inferior quality, the tolerance with regard to impurities is greater. It is important to note that, although divided, using the systematic approach adopted in this document, the classification and separation processes can also occur during reprocessing. The following types of processes can be applied in a typical reprocessing installation (Plastic Zero 2013b): –– –– –– –– –– –– –– –– ––

Opening bales. Additional fine separation and sorting (using equipment referred to in Sect. 4.7). Washing. Water extraction microfiltration (to remove glue, for example). Plastic size reduction, by cutting, using a shredder (for obtaining smaller pieces, for example about 12 mm long). Vacuum reactor to purify organic contaminants. Extrusion (for the production of plastic threads). Screening after or during the extrusion process (in order to remove any solid impurities). Pelletizing (cutting the extruded wires while still hot, to form pellets, followed by cooling in water).

 Product resulting from the processing of plastics or mixed films. The agglomeration aims to increase the apparent density of plastic waste, joining pieces by heating, at a temperature slightly below that of the melting point. The quality is defined according to the chlorine, water and ash content, as well as the apparent density and grain size. 8  High quality material made to measure, from granules, the properties of the base material being chemically modified with different additives and modifiers. 9  Industrial plastic waste is mostly made up of the leftovers from the production of plastic products in the factory, either during the start-up operation, or of the material rejected for non-compliance with quality requirements, or of batches stored abroad for longer than reasonably acceptable time. 7

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4.11 Manufacture of Final Products Plastic products can be manufactured using virgin polymer, made from crude oil, or secondary raw materials recovered from plastic waste as input material. The input is usually in the form of pellets, granules (of variable size, including powders), or profiles, depending on the type of product produced (Plastic Zero 2013b). The use of secondary raw materials often replaces production using virgin plastic materials. However, in some cases (often low-quality plastic products), other materials (for example, wood) are replaced by plastics. This issue is important when assessing the environmental benefits of recycling plastic. The manufacture of the final product generally involves a process of shaping intermediate plastic products by means of extrusion, molding, or blowing. Household plastic waste usually generates secondary raw materials of different qualities, from PP, HDPE, PET, and PS pellets to high-quality plastic products, obtained after positive classification by NIR technology, to mixed plastic waste, which can be used for energy purposes or for the production of low-quality products. Each type of final product requires different qualities of plastic (polymer and impurities), in terms of purity and stability of composition. For example, PET can be used for the production of textiles, as well as for the production of bottles, films, etc. The bottles are often produced from high-quality recycled plastic, and must meet the requirements for food packaging. The production of woolen jackets and the like can tolerate more impurities and, therefore, can be produced from PET from mixed streams of plastic waste. The current typical trend is that high-quality recycled materials replace virgin plastic, while low-quality recycled materials replace low-durability plastic products, as well as other materials in applications where this is possible, such as replacing wood in profiles of palisades, urban furniture, pallets, pedestrian platforms on beaches, etc., and for the formulation of composites (Sect. 3.2.3).

4.12 Impact of Different Recycling Processes Specialists in Circular Economy and Resource Efficiency (WRAP) carried out a life cycle analysis of several key processes for the elimination of mixed plastic waste, evaluating the potential of several impact categories, namely global warming (GWP), the photochemical ozone creation (POCP), eutrophication (EP), acidification (AP), human toxicity (HTP), ozone layer depletion (OLDP), and abiotic depletion (ADP) (Shonfield 2008). This study showed that, in terms of the net potential for global warming, the landfill is the option with the least favorable environmental performance, followed by incineration. All recycling processes have shown an environmental benefit, which is mainly due to the substitution of processes that, in this way, are avoided (for example, the need to produce primary plastic). Results in most impact

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categories are dominated by avoided emissions from replaced processes, showing the contribution to the overall global warming potential of each step in the process. This means that even some very large differences in the impacts of the process are often obscured by the even greater benefits that result from avoiding the use of primary resources (Shonfield 2008). In terms of solid waste generation, the study shows that the landfill has the greatest impacts and that the incineration scenarios have the least impacts, since plastic does not leave a lot of waste when burned. All other recycling scenarios result in widely similar amounts of solid waste, despite the diversity of technologies involved. The results show that there are possible scenarios in which incineration is preferable to recycling; when incineration replaces the need to use coal for energy production and when recycling does not produce high-quality recycled plastic. However, if it can be guaranteed that the recycled plastic is of high quality, the recycling scenarios always have an environmental performance superior to incineration for the global warming potential (Shonfield 2008).

4.13 Technologies for Industrial Recycling of Plastics 4.13.1 Chemical Recycling 4.13.1.1 Generalities Mechanical recycling of plastics can be expensive and difficult due to restrictions resulting from contamination of waste, or due to improper separation before recycling. For these cases, chemical recycling (also called feedstock recycling) is preferable and should be seen as a complement to mechanical recycling. As with mechanical recycling, sorting and pre-treatment are essential to optimize chemical recycling. The chemical recycling of plastic waste and polymers consists of decomposition of materials of a single classification, by changing its chemical structure, conversion into low molecular weight compounds and monomers through chain breaking or depolymerization, excluding energy recovery, use as fuel, and incineration. Monomers can be processed into feedstock recycling plastics using chemical synthesis, while chemical raw materials can be processed into feedstock recyclates for applications other than plastics, like functional polymers or chemicals. Consequently, depending on a process and an input material, chemical recycling includes two types of intermediates, namely monomers or chemical raw materials. Monomers are intermediates in a depolymerization process and chemical raw materials are intermediates in a feedstock generation process. Biological recycling does not directly fall within the scope of plastic recycling processes, but some of the products from this organic process can be used in chemical recycling, for example, for the production of synthesis gas, indirectly contributing to the recycling of plastics.

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Some authors (Rahimi and García 2017) refer the transformation of plastic waste mainly into fuels by thermolysis processes, like thermal cracking, pyrolysis, gasification, hydrothermal liquefaction, and pressureless catalytic depolymerization, as a method of chemical recycling. However, the relatively high internal energy requirements (high temperatures) and focus on producing fuels rather than materials make the term recycling controversial for most thermolysis processes. Furthermore, as the end products can also be used for applications other than plastics, the limits of plastic recycling processes, in terms of chemical recycling, cannot currently be clearly defined. Other chemical depolymerization technologies that allow the conversion of basic plastic waste into monomers, as feedstock for new polymers are generically called solvolysis, which includes hydrolysis, alcoholysis, methanolysis, glycolysis, and aminolysis. The polymer monomers produced by condensation reactions, such as polyurethanes, polyesters, and polycarbonates, are obtained by these methods. The chemical industry can thus play a leading role in increasing the amount of recycled plastic, expanding chemical recycling technology. Complementing mechanical recycling with chemical recycling will be essential to solve the EU’s waste plastic problem and reach the goal of the “Circular Plastics Alliance,” which aims to have by 2025, 10 million tons of recycled plastic incorporated into new products. 4.13.1.2 Recent Examples of Chemical Recycling Applications Canadian company “GreenMantra Technologies” has technologies for chemically recycling post-consumer and post-industrial LDPE, HDPE, and PP to convert them into waxes and additives for use in plastics and other building materials, such as asphalt and roofs (CW 2019). Recently, GreenMantra started to supply a series of additives for the production of wood-plastic composites (WPC) with PE or PP, with increased strength and rigidity (CW 2019). Prof. Thomas Maschmeyer, from the School of Chemistry and the Sydney Nano Institute, has commercialized, with his start-up, Licella, a new industrial process, Catalytic Hydrothermal Upgrading (Cat-HTR™), that uses supercritical water to economically convert plastic waste, otherwise destined for landfills, into oil and gas, with 98% efficiency, to produce fuels, chemicals, and new plastics, helping to unlock a circular economy for all plastics (SpecialChem 2021b). The company “Mura Technology Limited” holds the licensing of Licella’s technology and maintains the ability to develop its own operational recycling capacity, with the first Cat-HTR™ unit currently under development in Teesside, North East England. After the completion of this first unit, it will have the capacity to process 80,000 tons of plastic waste per year, but it is expected to have a recycling capacity of 1 million tons of plastic waste by 2025. For the global implementation of this innovative technology, “Mura Technology Limited” has partnered with “Kellogg, Brown & Root Engineering” (KBR), whose position at the forefront of innovative

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and revolutionary technologies offers Mura world-class development opportunities for the Cat-HTR™ platform in the global petrochemical sector (SpecialChem 2021b).

4.13.2 Mechanical Recycling 4.13.2.1 Generalities Mechanical recycling consists of processing plastic waste into secondary raw materials or recycled plastic without changing the chemical structure of the material, that is preserving the polymer chain and the polymer composition. The secondary (intermediate) raw material can be directly reused or subjected to further treatment by remelting or compounding. The end product of the mechanical recycling process is plastic recyclate, which represents a material that contains a high polymer as main component and can be shaped into finished products during its processing. The definition of mechanical recycling technologies covers pre-treatment and classification to establish the quality of recyclable plastic and the techniques for manufacturing plastic products. The entire process consists of three main steps (Plastic Zero 2013a): 1. Pre-treatment, involving separation, classification, cleaning, and reducing the size of plastic waste. 2. Creation of intermediate products, involving grinding, extrusion, and pelletizing. 3. Manufacture of new products, for example, by extrusion, molding, or blowing. The set of equipment for a typical mechanical recycling plant depends on the type of recycled products targeted and the detailed characteristics of the application (amount of contamination and the final usage of the finished product). There are basically two types of mechanical recycling. In one case, the recycled material can be used for the same purpose for which it was originally designed (process designated as direct recycling or closed circuit recycling). In another case, the recycled material can only be used in other types of products, less demanding (what is often called “downcycling,” that is to say recycling of lower or descending cycle). Bioplastics, such as PLA and PHA, cannot be recycled mechanically, but only through chemical recycling technologies. 4.13.2.2 Direct Recycling (Closed Circuit) Closed-loop recycling is achieved when polymers can be used again for the same type of products and applications for which they were designed before recycling. Examples of closed circuits are bottle racks, PET soda bottles, HDPE milk bottles, and PVC pipes (Plastic Zero 2013a).

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One of the main reasons why plastic is not kept in a closed circuit is the strict requirements in terms of material quality for certain applications, such as, for example, what happens with packaging in contact with food. The food packaging can be used again as a food packaging, but the recycling process requires separation of the target food packaging from the mixed residual plastic stream, followed by a decontamination process. This is an expensive recycling process and, therefore, mixed, recyclable plastic packaging is often used in other types of products. Other applications with strict requirements are electrical and electronic products, children’s toys, medical equipment (Plastic Zero 2013a), and PVC window profiles. The establishment of closed material circuits generally requires a separate collection system to avoid mixing the target products with others. 4.13.2.3 Downcycling One of the most frequent reasons why waste plastics are often recycled in a descending cycle results from situations in which the color of the recycled output material becomes darker due to impurities in the input material. The final product may also be stained on the surface due to these impurities. It is difficult to obtain a color of pure white, or other colors, if the input material consists of a mixture of materials of different colors. Therefore, the outlet material is used in gray or black-colored products (Plastic Zero 2013a). Examples of this are: –– Films and opaque bags. –– Transport, construction, and outdoor furniture materials (pallets, pipes, railings, fences, planks, benches, flower boxes), as color has little or no importance for many of these applications. –– Utility articles and interior furniture, as the imperfection in color is acceptable or even part of the desired appearance for many of these applications. Most applications of recycled materials in a downward cycle are intended for direct substitutes for virgin plastic products, while others replace other materials, such as when a plastic bench replaces a wooden bench, or when synthetic fibers replace natural fibers. Like wool or down. Even if these applications are considered “downcycling,” the products can still have a high durability. In addition, the material acquires an additional useful life period and allows to postpone its final disposal. In many cases, the material can even be recycled multiple times. There are some innovative mechanical recycling technologies that deserve to be mentioned, as they include pioneering and innovative techniques for solving very specific problems, namely the separation of various types of polymers or the development of products from mixtures of these polymers, as described below.

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4.13.2.4 Processes for Recycling of Mixtures of Plastics 4.13.2.4.1  Solid State Shear Pulverization In 1990, Northwestern University’s Department of Chemical Engineering developed a new secondary plastic recycling process called “solid state shear pulverization technology (S3P),” which eliminates the need for classification by type or color. This technology is a continuous, single-step process that uses a modified co-­ rotating twin screw extruder, which includes, in its initial segment, a solid state shear sprayer, to keep the polymer in the solid state during the processing. It allows the recycling of unselected plastic waste, converting crushed plastic or rubber waste into particles of controlled size, ranging from coarse (10 and 20 mesh) to fine (80 mesh) or ultrafine (200 mesh), and still allows to manufacture polymer blends and polymeric nanocomposites (Fig. 4.37). As a result, the spray product is usable in applications ranging from direct injection molding, without prior pelletizing, to rotational molding, for use in protective and decorative coatings, as well as for mixing with virgin resins and composition with additives. Injection molded parts made of the powdered product from the S3P process have comparable or better mechanical and physical properties than the properties resulting from the direct conventional processing of simple or mixed recycled plastics. In addition, parts made from the powder product of the S3P process can be of uniform or multicolored colors. The high degree of mixing achieved through the S3P process is often associated with the carbon chain cleavage in the polymers that make up the mixture, resulting in the generation of free radicals during S3P processing and consequent modification of the fluidity index of the polymers by the S3P process. Research and development of S3P technology has evolved significantly since 1990 to a much broader polymer processing method, which allows efficient mixing of polymers with very different viscosities and the dispersion of additives in the

Fig. 4.37  Image, under two perspectives, of the equipment used in the S3P process (Wakabayashi 2013). (Courtesy of Professor Katsuyuki Wakabayashi, Bucknell University, Lewisburg PA, USA)

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solid state, including pigments and continuous powder production with exclusive shapes and larger surface area. S3P can convert multicolored, unclassified residues and virgin resins into a uniform, light-colored powder with controlled particle size, suitable for direct melt conversion by all existing plastic processing techniques. In addition, this process allows for in-situ compatibility of different polymers through the application of mechanical energy to cause chemical reactions. Unlike previous processes, through which the polymers are melted before spraying, the S3P process does not involve melting. On the other hand, S3P keeps polymers in a solid state and avoids the application of heat that occurs during other processes, which can be detrimental to the physical properties of the pulverized materials (Khait 2001). S3P mixes polymer mixtures efficiently with different component viscosities, resulting in the elimination of phase inversion. The S3P process directly produces mixtures with matrix and dispersed phase morphology similar to those obtained after the phase inversion that takes place during the long mixing process, by melting. In addition, S3P technology is also advantageous for the production of powder-­ coated, thermoplastic, or thermosetting composites, in a single-step process, as opposed to conventional multi-step operating processes, involving melt extrusion, followed by batch grinding produced. The main characteristics of this new process are summarized below (Khait 2001): –– –– –– –– –– ––

Continuous production of dust from plastic or rubber raw materials. Mixture of immiscible polymers. Efficient mixing of polymers with viscosities not comparable. Ecological recycling of multicolored mixed plastic waste. Dispersion of heat-sensitive additives in the solid state. Previously defined plastic/rubber mixtures.

4.13.2.4.2  Powder Impression Molding Process The waste generated at works and construction sites is often difficult and expensive to recycle due to the variety of materials used. However, some materials, in addition to being light, can have excellent mechanical properties, which makes them ideal for reuse in construction products. The impression powder molding process (PIM) is a mechanical recycling process capable of processing most of the available residual materials and, from these, making usable products that allow this sector to minimize its environmental impact. The PIM process can use mixed plastic waste that is not classified with a high level of contaminants, without using cleaning and polymer segregation processes (ERT 2015). The bulk waste is crushed and transformed into powder and granules and later to be converted into sandwich structures, light and reusable. The material produced is melted, expanded, and used as a filler between two films. The process involves forming two layers of coating by sintering plastic powder on the mold surface, creating the core, and foaming the core to produce a

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sandwich structure integrated with solid surface coatings. Using open molds, it is possible to form composites with different films on each surface, with different materials, and also with different properties and colors (ERT 2015). Depending on the formulation, materials derived from the PIM process perform similarly to conventional foam, fiber boards used in floors and for thermal and acoustic insulation. The design of the PIM process, which uses micronized mixed plastic waste, involves the application of a virgin polymer film inside a hot molding tool. The core material, consisting of mixed recycled powder and blowing agent, is then sprayed onto the bottom half of the mold. A lid, also coated with virgin polymer, is then lowered over the bottom half of the mold and the mold halves are fixed together. The mold is then placed in a hot curing oven, where the core material melts under pressure, partially generated by the blowing agent, after which the mold is cooled and the product is removed. This process does not require the complete fusion of all the constituent particles, since the upper and lower virgin polymer sheets maintain the composite core and form the main load structure of the manufactured component. Depending on the final application, the composite core may contain a wide range of mixed polymer residues, including a percentage of fillers and inorganic fibers. The mixed polymeric composite, constituted by a mixture of residues, can be used as construction material, in temporary structures, flood protection barriers, floors, and marine structures. The PIM process should allow the manufacture of products for the construction industry, containing up to 80% recycled plastic mixed as the main material, without loss of functionality and without prejudice to aesthetic appearance. By selecting the material and adjusting the process conditions, it is possible to manipulate the density and properties of the composite material. Both the surface film and the core of the product can be made from recycled, virgin, or mixed plastic. Each plastic recycling line of the PIM process can be designed and built to specification to meet specific product requirements. Products made with the PIM process are recyclable and can be reused as raw material for the manufacture of new products. In summary, the PIM process offers a sustainable opportunity to use large volumes of mixed plastic waste streams that cannot be separated physically or economically. PIM economically produces value-added end products from low-value plastic waste that would otherwise be incinerated or sent to landfill. The process has the capacity to produce molded products, on a large scale, which are usually lighter, easier to handle, very robust, and require little or no maintenance.

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4.13.3 Optimization of Recycling and Separation Technologies As mentioned above, recycling methods allow the conversion of plastic waste streams (from different applications, including packaging) into raw materials and products with different applications, including construction materials and products, so it is pertinent to mention the most recent developments. Recycling technologies for identifying and separating plastics in mixed streams. The company Erema has developed a package (QualityOn PoliScan) that allows supervision and continuous quality control during a recycling process. Various parameters, such as volume flow rate (MVR), intrinsic viscosity, color coordinates, and polymer composition (by Raman spectroscopy) of the input material, can be measured directly on the processing machine. In combination with the Manufacturing Execution System Re360, which records production and machine data for the entire range of manufacturing machines, it is possible to support the optimization of the recycling process (PRW 2019d). The company Sikora has developed an optical laboratory test system, called “Purity Concept V,” for plastics, using color detection. The system consists of an automated light table in which the plastic granules, placed in a movable sampling tray, are transported along the inspection area. In seconds, the material is inspected by a colorimetry camera, and a projector optically marks all contaminated granules in the sampling tray. When evaluating images and contamination, such as black spots on the surface of transparent, translucent, and colored material, with a dimension above 50 μm, the granules are automatically detected, visualized, and statistically evaluated, allowing also the screening by the use of a designated equipment “Purity Scanner Advanced.” Clear contamination assignment and subsequent inspection are possible at any time. Another characteristic of the optical laboratory test system is the automatic detection of color deviations in the granules (PRW 2019d). Sikora also developed the “Purity Concept X” laboratory test system with X-ray technology for the detection of metallic contamination. The device is dedicated to the inspection of metallic inclusions on the surface and inside of black and colored granules, which would be invisible with optical systems. Repsol, Axens, and IFP Energies Nouvelles have joined forces to develop a new process (Rewind™ Mix) for the chemical recycling of plastic waste that removes impurities such as silicon, chlorine, diolefins, and metals from plastic waste mixed to produce pyrolysis oils, allowing the direct and undiluted processing in existing petrochemical plants for the production of circular plastics, which they hope to experiment on an industrial scale at a Repsol unit (PRW 2021a, b, c).

Chapter 5

Plastics Statistics: Production, Recycling, and Market Data

5.1 Generalities Although there are several European organizations that obtain and provide information and statistics on market data regarding the plastics value chain, namely PlasticsEurope, EuPC (the European Plastics Converters), EuPR (the European Plastics Recyclers), and EPRO (the European Association of Plastics Recycling and Recovery Organizations), access to up-to-date and reliable market statistics is not always easy. The data presented here correspond to those in the bibliography, in particular in PlasticsEurope’s annual reports. For a more detailed analysis worldwide, it is also suggested to consult other specialized publications (OECD 2019; Geyer et al. 2017).

5.2 Production Capacity and Application Market for Plastics The plastics industry is vital to Europe’s economy and its recovery plan. Together, producers of plastic raw materials, plastic transformers, plastic recyclers, and machinery manufacturers represent a value chain that employs more than 1.5 million people in Europe, through more than 55,000 related companies, most of them SMEs, operating in all European countries. In 2019, these companies earned more than 350 billion euros and contributed more than 30 billion euros to European public finances (PlasticsEurope 2020).

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In 2019, the global production of plastics almost reached 370 million tons (359 in 2018).1 Figure 5.1 represents plastic production in the world and in Europe until 2019 (cumulative graph). These plots are based on data extracted from several publications of PlasticsEurope (PlasticsEurope 2006–2020). Table 5.1, on the other hand, shows the percentage distribution of plastics production in the various regions of the world (PlasticsEurope 2020), which shows that China is the largest world producer of plastics. In 2019, the total demand for plastics in Europe (EU28 + NO/CH) for industrial conversion was 50.7 million tons, distributed among the segments indicated in Table 5.2 (PlasticsEurope 2020). As can be concluded from Table 5.2, the packaging and construction markets are those that lead the market, followed by the automotive industry. Table 5.3 shows the plastics market in Europe (EU28 + NO/CH), in 2019, by type of resin and application (PlasticsEurope 2020). Practically, all types of thermoplastics referred to in Table 43 are used in packaging, and almost all (except PET) are also used in construction, in the automotive industry, and in electrical and electronic equipment.

5.3 Production Capacity and Market for Biobased Polymers 2020 was a promising year for biobased polymers. In 2020, the total volume of production of biobased polymers was 4.2 million tons, which represents 1% of the total volume of production of fossil-based polymers. For the first time in many years, the compound annual growth rate (CAGR) is at 8%, significantly higher than the overall growth of polymers (3–4%), a trend that is expected to continue until 2025 (Nova 2021). After Asia, as the leading region, which installed the largest global biobased production capacities with 47% in 2020, Europe follows with 26%, North America with 17%, and South America with 9%, respectively, with Australia having a production capacity of around 1% (Nova 2021). With an expected CAGR of 16% between 2020 and 2025, Asia exhibits the greatest growth in biobased polymer capacities compared to other regions in the world. This increase is mainly due to the greater production capacities of PA, PBAT, PHA, and PLA (Nova 2021). Biodegradable plastics, such as polylactic acids (PLAs) and polymers based on cornstarch, reached a market share of 56% of the total market for bioplastics in 2018. Biobased plastics such as polyethylene, PET, or PA made of sugar cane, which are not biodegradable, are expected to experience weaker growth, at 5.1% per year (Goldsberry 2020).

 According OECD report (OECD 2019). The annual production of plastics in the world, in 2019, was 460 million tons. 1

Fig. 5.1  Accumulated world production of plastics until 2019

5.3  Production Capacity and Market for Biobased Polymers 105

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Table 5.1  Distribution of plastic production in 2019 (PlasticsEurope 2020) Region Asia (China) USA and Mexico (NAFTA) Europe Middle East and Africa Latin America Commonwealth of independent states (CIS: Russia, etc.)

% 51 (31) 19 16 7 4 3

Table 5.2  Total demand for plastics in Europe (EU28 + NO / CH) for industrial conversion, by sector of activity, in 2019 (PlasticsEurope 2020) Activity sector Packaging Building & construction Automotive Electrical & electronic Household, leisure & sports Agriculture Others (include appliances, mechanical engineering, furniture, medical, etc.)

% 39.6 20.4 9.6 6.2 4.1 3.4 16.7

Currently, biobased polymers can be used in almost all market segments; but the various applications per polymer can be very different. The sectors that lead the use of bioplastics are the fiber industry (mainly cellulose acetate and polytrimethylene terephthalate) and packaging (both with a 24% share in total), followed by the automotive industry and transport (using mainly epoxy resins, PUR, and aliphatic polycarbonates) with 16%. The percentage of use in buildings and construction is 14% (mainly epoxy and polyamide resins). The agro-horticultural, electric and electronic, functional, and other market segments have a market share of less than 5% (Nova 2021). More detailed information about the bioplastics market can be found in the reference (European Bioplastics 2021).

5.4 Quantities of Recycled Plastic According to OECD data (OECD 2019), only 9% of plastic waste in the world will have been recycled in 2019, with 19% being incinerated and almost 50% sent to landfills. The remaining 22% were disposed of in uncontrolled dumps, burned in open pits or leaked into the environment.

5.4  Quantities of Recycled Plastic

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Table 5.3  Plastics market in Europe (EU28  +  NO/CH), by type of resin and application (PlasticsEurope 2020) Resin PP

Applications Food packaging, candy wrappers and appetizers, hinged lids, microwave containers, pipes with fittings, auto parts, bank notes, etc. LDPE (homo and copolymers) Reusable bags, trays, containers, films for agriculture, and PELBD (linear copolymers) films for food packaging, etc. HDPE and PEMD Toys, milk and shampoo bottles, tubing, household items, etc. Other thermoplastics Miscellaneous

% 19.4

17.4 12.4 11.6

In Europe, around 43% of all plastics produced are collected for recycling every year, but only 11% are really sent for recycling. The remaining waste, including the contamination discarded during recycling processes, cannot be recycled due to very poor design or quality. Instead, it is sent to incineration plants, or in the worst case, for landfills (de Gregorio 2021). The highest percentage of recycled materials in Europe is generated by the packaging market. Figure 5.2 represents the quantity of packaging generated in Europe in 2018, by Country and per capita. Figure 5.3 shows the quantity of packaging recycled in Europe in 2018, by Country and per capita. *(Iceland): value from 2017. The graphs in Fig. 5.4 illustrate the evolution of the type of treatment carried out on post-consumer waste between 2006 and 2018, in Europe, in terms of percentage and mass, respectively, demonstrating that 25% of this waste was still sent to landfill in 2018. According to EUROSTAT, the rate of packaging recycling in Europe has evolved over the years, as shown in Fig. 5..5. According to OECD, sanitary landfill was responsible by 49% of end-of-life-fate of all plastic waste produced in the world during 2019, followed by incineration (19%), against only about 9% of recycling (OECD 2019). Figure 5.6 Countries that have legislation that restricts the sending of post-­ consumer plastic to landfill are shown in the zone limited to the left of Fig. 5.6, which illustrates waste treatment in Europe (EU28  +  NO/CHE) in 2018. (PlasticsEurope 2020): Switzerland, Austria, Netherlands, Luxembourg, Sweden, Finland, Belgium, Denmark, and Norway Currently, only 11 European countries recycle or recover over 90% of plastic waste, with 12 countries sending more than 40% of plastics to landfill. In 2018, about 3.3 million tons of plastic waste were landfilled in Europe (PlasticsEurope 2020), thereby wasting a large amount of resources and increasing the risk associated with waste. However, there has been a great reduction in the amount of plastics sent to landfill (Fig. 5.6). When plastic is dumped in landfills, the decomposition process can take 10−30 years to complete. The European plastics industry is working with a number of stakeholders in order to achieve “Zero Plastics to Landfill” in Europe. Recycling

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Ireland Denmark Estonia Portugal Italy Spain

Country

Hungary Malta Netherlands Poland Finland Sweden Latvia Romania Greece Croaa 0

5

10

15

20

25

30

35

40

45

50

55

60

Kg per capita

Fig. 5.2  Quantity of packaging generated in Europe, in 2018, by Country. (Source: Eurostat)

has therefore become a reasonable solution to the problem resulting from sending plastic to landfills. According to OECD, Building & construction is the application responsible by 4,6% of plastic waste produced in the world (OECD 2019). Table  5.4 shows the distribution of products containing recycled materials by sectors of activity, thus confirming that it is construction products that use more recycled materials. Countries in Europe that have good statistical control over waste treatment are Germany, the United Kingdom, Italy, France, Spain, Poland, the Netherlands, and Belgium. In 2018, of the 5 million tons recycled in Europe, around 80% was reused for the production of new products, the rest being exported outside Europe. Finally, it should be noted that the plastic recycling market “collapsed” during the Covid-19 crisis, as the general use of recycled materials fell by more than 40% due to the combination of adverse factors (low prices for virgin resin and drop in demand). The current crisis represents a risk, not only in terms of slowing down the planned expansion of the recycled markets, but also in the fact that the objectives already achieved so far can be called into question.

Country

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Lithuania Germany Spain Ireland Italy Estonia Netherlands United Kingdom Norway Czech Republic Luxembourg Portugal Iceland * Denmark Belgium Slovakia Sweden Slovenia Bulgaria Austria Cyprus Hungary France Poland Romania Latvia Finland Greece Croatia Liechtenstein Malta 0

2

4

6

8

10

12

14

16

18

20

Kg per capita

Fig. 5.3  Quantity of packaging recycled in Europe, in 2918, by Country. (Source: Eurostat)

5.5 Costs of Recycling It is difficult to define and generalize the costs associated with recycling, as they depend on several factors (Plastic Zero 2013a). The costs associated with the collection, sorting, and transport of plastic waste can be considerably high, but are highly dependent on local conditions, such as transport distances, labor costs, capacity of treatment units, and availability of cargo centers. If the cost of a necessary separation and classification process becomes too high, the residual plastic will probably be exported to countries with lower treatment costs or, alternatively, the waste will result in a low quality recycled (Plastic Zero 2012). Transport costs are decisive for the cost of recycled plastics and they fluctuate considerably, often on the same day, due to the availability of transport to a predefined destination, still with available cargo capacity (Plastic Zero 2013a).

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Recycling Incineration

%

Landf ill

60.0 50.0 40.0 30.0 20.0 10.0 0.0 2004

2006

2008

2010

2012

2014

2016

2018

2020

year

Fig. 5.4  Evolution of the type of treatment carried out on post-consumer plastic, in Europe, between 2006 and 2018. (Data based on PlasticsEurope 2019)

5.6 Prices of Recycled Plastics Basically, it is the demand from the world market for recycled plastics that sets the price and quality of plastic waste. Demand is influenced by the price of virgin material, as well as the quality of the recycled polymer. The previous collection and separation will define the limits for the fulfillment of the buyers’ quality requirements. The Eurostat price indicator for plastic waste shows the same trend as for virgin plastic and crude oil. About 75% of the demand for recycled plastic in Europe is covered by five polymers: PP, PE (HDPE, LDPE), PET, PS, and PVC. However, some types of polymer are more valuable than others. PET prices are generally higher than HDPE prices, followed by LDPE and mixed polymers. PET and HDPE from packaging in contact with food (and approved for that purpose) are the most valuable polymers. Those in 2012 had prices around 900–1100 GBP (1100–1350 euros) per ton, for pelleted polymers (WRAP 2012). The prices of polymers such as PP and PS are considerably lower, for example, 0–200 GBP (0–250 euros in 2012) per ton of baled material (WRAP 2012).

5.6  Prices of Recycled Plastics

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% 50.0 45.0 40.0 35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0 2004

2006

2008

2010

2012

2014

2016

2018

2020

Year Fig. 5..5  Evolution of waste treatment in Europe (EU28  +  NO/CH), in millions of tons, from 2006 to 2018

Fig. 5.6  Recycling, energy recovery, and landfill rates of post-consumer plastic in Europe (EU28  +  NO/CH) in 2018, by country. (PlasticsEurope. Plastics  – the Facts 2020. All rights reserved)

Consequently, the composition of a mixed plastic waste stream is of great importance for the overall value of the recycled materials obtained after separation. Technical polymers, such as ABS, polybutylene terephthalate (PBT), and POM, which are widely used in construction materials, are also recyclable, but, although

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Table 5.4  Distribution of recycled materials by sector of activity, in Europe (EU28 + NO/CH), in 2019 (PlasticsEurope 2020) Activity sector Construction Packaging Agriculture Car Electric and electronic Home, leisure, and sport Others (mechanical engineering, furniture, medicine, etc.)

% 46 24 13 3 2 1 11

they are quite valuable, they require special requirements to give separated, so they are priced much higher than the most common polymers (Plastic Zero 2012). Therefore, transparent polymers (such as LDPE) are more expensive than colored or translucent polymers. The degree of reprocessing also affects the price of the recycle. For example, granulates are priced higher than those recycled in bales. Finally, the purity of the recycle, which refers to the content of other polymers and non-plastic materials and impurities that can be accepted, also determines the price. Therefore, the economy of any recycling process depends on the yield of the useful material that can be obtained from the incoming material flow; for example, the proportion of the highest value polymer types (such as PET, HDPE, LDPE) that a batch contains. Contamination with undirected polymer (for example, film in a flow of rigid plastic) or paper can decrease the value of a mixed plastic deposit from 5% to 35%. Higher final prices for packaging recycled are only achieved for mixed bales, if PET and HDPE have not been extracted from the mixed plastic stream for separate sale (WRAP 2012). Processing costs are determined by the quality of the material, the type of polymer, the ease of reprocessing, and the technologies used. In addition, quality control analyzes increase reprocessing costs, possibly decreasing the competitiveness of recycled polymers. The prices of recycled or secondary plastics depend, to a large extent, on the demand for recycled plastics on the international market (China/ Asia), which also depends on the level of economic activity of the importing country, the global prices of virgin plastics, and the regulation of EU and each country (Plastic Zero 2012).

5.7  Competitiveness of the Waste Management Sector

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5.7 Competitiveness of the Waste Management Sector Investment in recycling facilities (facilities, land, and technology) is high, and the operating cost consists mainly of labor and energy costs. Thus, productivity plays an important role in deciding where to establish a recycling and/or reprocessing facility, and whether to invest in more or less intensive technology, or in labor (Plastic Zero 2013a).

Chapter 6

Constraints to the Application of Recycled Plastics

6.1 Generalities The use of recycled plastics in construction products (insulation, internal layers of coverings, doors, windows, pipes, and as fillers for various building materials) can improve the energy efficiency of buildings and reduce CO2 emissions, having been shown to be effective in a wide range of sustainability indicators. However, there are still several obstacles that hinder a wider use of recycled plastics in the construction sector. One of the biggest obstacles to the use of recycled plastic in high-quality products is the lack of stability, resulting from the heterogeneity of characteristics. For a plastic producer, it is very important to always have a raw material with the same characteristics, since the production, namely the configuration of the processing variables, is very sensitive to small deviations, such as, for example, the temperature of fusion of the raw material. Deviations in the melting point of the raw material can affect the functionality, strength, or durability of the product, which is not acceptable for some applications, for example, for safety reasons, medical equipment, or auto parts. The use of secondary plastic in these products is therefore very limited. For less sensitive products, a very common way to limit this problem is to “dilute” the secondary plastic in virgin plastic, where the composition is stable and fully documented (Plastic Zero 2013b). The presence of hazardous substances in mixed plastic streams also limits applications of recycled plastic in products such as medical equipment, toys, food packaging and baby equipment. Impurities, such as organic waste, bacteria, etc., are mainly a hygiene problem during the collection, storage, and classification and separation of plastic waste, but rarely affect the quality of the final product (secondary plastic). The consumption of plastic for the production of food packaging is huge, and the use of recycled plastic for this purpose is attractive. However, a number of requirements of European food safety legislation must be met, which can prevent the use © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 L. E. P. Real, Recycled Materials for Construction Applications, https://doi.org/10.1007/978-3-031-14872-9_6

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of packaging for non-food purposes in production (Plastic Zero 2013b). This is a barrier to the use of recycled plastic from mixed plastic streams, as there is no technology available today that can separate food packaging from packaging for non-­ food purposes. Only the positive classification of, for example, easily recognizable products, such as packaging and bottles (HDPE, PET, or similar), can be separated from a mixed plastic stream by optical separation (NIR). The use of recycled plastic or food packaging is therefore currently limited to individual products (for example, bottles recognized by the NIR) or materials collected separately. A future development of sensor-based recognition techniques can reduce this problem and thus increase the proportion of secondary plastics involved in the production of food packaging. The technologies “Dual Energy X-Ray Transmission” (DEXRT) and “Laser-Induced Breakdown Spectroscopy” (LIBS) aim at the separation of, for example, contaminants from heavy metals. However, these technologies are not yet sufficiently developed to be applied in low-cost operations (Plastic Zero 2013b). The color of the secondary raw material can also lead to the exclusion of recycled applications in some applications. Recycled plastic usually has colors (gray, green, etc.), which makes it suitable for the production of highly colored materials, but not for transparent products. The production of fully transparent products requires only a very clean flow of transparent plastic. For plastic products of inferior quality, a higher degree of impurities and varied composition can be accepted, without compromising the function of the product.

6.2 Environmental Problems Associated with Recycling Recycling of plastics is generally considered an environmental advantage over alternatives, which will normally be incineration or landfill. However, since plastic is a good (fossil) fuel, the recycling system must be sufficiently effective to guarantee the environmental advantage of recycling in relation to its use for energy production. There are some aspects that must be taken into account to assess the overall environmental performance of the plastic recycling system (Plastic Zero 2013b): –– The fraction of the plastic collected discarded in the classification process, for example, black plastic, non-certified packaging, unwanted polymers, etc. –– The ability to replace virgin material (virgin plastic, wood, or other materials). –– The energy consumption of the sorting installation. –– Transport distances (especially if plastic is exported to Asia). –– The alternative treatment of waste (incineration or landfill, and the performance of these treatment technologies).

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In order to carry out an objective environmental assessment, it is necessary to specify a real system and to define specific scenarios for comparison. For this purpose, all relevant data should be considered to estimate the savings obtained by recycling plastic. CO2 is normally chosen as an example of an environmental impact parameter, but there is a range of other parameters (acidification, polluting smoke, toxic impacts, etc.) that can also be relevant and therefore must be taken into account (Plastic Zero 2013b). Therefore, the balance between the economy due to the saved production of, for example, energy or new materials, and the emissions of CO2 and polluting smoke must be considered (which, in addition to being able to vary considerably with the specific recycling technology and the chosen application), also depend on the different transport options, which can also vary considerably depending on the specific choice of vehicle or ship). The real savings of a specific case must be assessed in waste system scenarios (collection, treatment and disposal, including upstream and downstream effects), comparing recycling with the alternative waste treatment option. The ratio economy/total emission of a plastic incineration process depends on the specific situation of the incineration unit with regard to energy use. Since plastic is based on fossil material, the incineration of the plastic will result in a certain emission of fossil CO2, which is counted as a net emission. Only if the energy produced is used effectively for electricity and/or heating, substituting fossil energy sources can an environmental saving be achieved in a magnitude that makes the general CO2 account, for plastic incineration, a net reduction of CO2 (Plastic Zero 2013b). The accounting for CO2 for plastic incineration therefore depends on (1) the efficiency of the incineration plant and (2) the replaced energy sources (electricity and district heating).

6.3 Main Difficulties in the Recycling of Plastics There are some constraints to recycling plastics, particularly related financial costs, such as transport costs (plastics are bulky and expensive to transport and store) and separation costs (different varieties of plastic, and mixed plastics contain different dyes and additives that, for quality reasons, may require separation). Pandemic situations, such as the one that occurred in 2020 with the Covid-19 virus, aggravate recycling costs and make it even more difficult to maintain competition with virgin materials, which normally suffer a significant price reduction, resulting from the decrease in production activity and, consequently, demand. Thus, in certain circumstances, it may be cheaper and easier to use virgin plastic instead of recycled plastic, even more so because some types of plastics can only be recycled once, unlike glass, paper, and metal packaging that become similar products after recycling and can be used and recycled continuously.

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Another serious problem that may occur with plastic waste is related to the additives contained therein (see, for example, Section 7.1.2), namely dyes, stabilizers, and plasticizers that may include toxic components such as heavy metals from old formulations (with lead and cadmium). In addition, it should be noted that thermosetting plastics (see Sect. 2.3), as well as composites that use matrices of this type of resins, are not easily recycled. Finally, it is also quite complex to identify and separate hybrid materials into plastic compounds and mixtures.

Chapter 7

Recycling of the Main Plastics Used in Construction

7.1 PVC Recycling 7.1.1 Generalities Due to its versatility, PVC continues to be one of the most used polymers in the world, as it provides suitability for applications in the most diverse industrial, technical, and domestic environments. Due to its low weight, durability, and stability, PVC can offer energy, economic, and technological efficiency advantages in several construction applications (PRW 2019d). PVC is predominantly used for furniture and long-lasting products, mainly construction materials, such as window frames, pipes, floor coverings, false ceilings, and in electrical cables (Fig. 7.1). Although the average life of long-lived PVC products is variable, a value of around 25 years is currently accepted. However, some plastic products used in construction have a longer service life. It is accepted that PVC pipes and ducts used in water and sewage infrastructures generally have a useful life of more than 100 years, so that many of these pipes are not yet available for recycling. Currently, the replacement of pipes from these infrastructures is more likely to be due to unacceptable breakages and failures (which may result from operational, installation, or manufacturing problems), or a need to change the capacity of the piping circuits due to unforeseen developments (Whittle and Pesudovs 2007). A potential source of pipes for recycling is that resulting from leftovers from the construction industry. However, the ability of these pipes to be cut and reused, or reprocessed internally for manufacturing, greatly reduces the amount of product available for recycling. Some (other) long-lived PVC products that were produced and sold since 1960 have started to enter the waste stream, some years ago. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 L. E. P. Real, Recycled Materials for Construction Applications, https://doi.org/10.1007/978-3-031-14872-9_7

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Fig. 7.1  Typical PVC construction products: (a) vinyl floor covering; (b) piping; (c) window profiles; (d) doors; (e) suspended ceilings

In view of the increase in PVC production and the large volume of long-lasting PVC products, which will become residual in the future, it becomes evident that PVC recycling is a fundamental feature to guarantee the protection of the environment, and that it is a great contribution to a circular economy. In fact, PVC can be recycled up to seven times without any loss of performance, and can be reused in many new and long-lasting products, from construction products such as windows, floors, and electrical components. The good quality of recycled PVC and innovative solutions to solve the main problems of PVC (see Sect. 7.1.2) is an important factor that drives the success of recycling and increases the demand from manufacturers. Discarded PVC products are collected selectively in many countries. PVC is normally separated directly at the construction site and sent to recyclers for granulation, micronization, and mixing. These recycled materials can be used in the middle layer of drain pipes, designed in multilayer, or in electrical cables. A study demonstrated the environmental benefits (for example, less CO2 emissions) of using recycled PVC in window frames (Stichnothe and Azapagic 2013). Window profiles can be retrieved and re-extruded to make new windows, doors, and various construction products. In fact, the potential for reusing existing products for a second life in service is being increasingly explored (PRW 2019d). PVC is also used to form the matrix of wood-plastic composites, mainly in the USA. However, in Portugal, there is a manufacturer of WPC with PVC matrix. A work developed by Fumire and Tan showed that it is possible to recycle rigid PVC in pipes with structured wall, with foamed intermediate layer countless times,

7.1  PVC Recycling

121

increasing the useful life of the PVC material by more than 300 years, and that the use of recycled PVC at a level of only 25% in structured wall pipes would consume more recycled rigid PVC than what was available on the market at that date (Fumire and Tan 2015).

7.1.2 Difficulties A problem that persists in PVC recycling is the high chlorine content of raw PVC (56% by weight of the polymer) and the high concentrations of additives, this being the polymer that has the highest proportion of additives of all plastics, which can represent up to 60% of the weight of a PVC product. In addition, the old PVC formulations contained dangerous stabilizers, based on heavy metals, which were added to the polymer to allow processing of the polymer at a temperature above 170 °C and also to give specific properties to the material. Although PVC formulations have started to change in this century and heavy metals and dangerous stabilizers have been completely banned (e.g., cadmium and lead), like most PVC products have a long shelf life, old formulations will naturally be present in the waste stream for decades. This problem led to a conflict between the objectives of the EU’s circular economy and the management of restricted substances under the EC directive 1907/2006 (REACH 2006) and administered by the European Chemical Agency (ECHA). ECHA proposed a 0.1% lead content limit for articles that do not contain recycled PVC and, for some construction applications, there would be a 15-year derogation with an upper lead content limit for articles that use recycled PVC. Those responsible for the “VinylPlus” program, created by the EU, sent comments and information to ECHA, including the results of independent studies on the levels of lead stabilizers in rigid PVC, considered safe (PRW 2018). A research project, commissioned in 2015 by the “VinyLPLus” program from “Forschungs-GmbH für Analytik und Bewertung von Stoffübergänge” (FABES), demonstrated that the migration of existing additives in recycled rigid PVC, from window profiles and pipes, was very low and the water used to wash recycled PVC complies with the very strict requirements of environmental standards. This study considered all possible options for managing rigid PVC waste, and also demonstrated that the reuse of this waste stream is preferable to alternative disposal routes (PRW 2018). In addition, it is likely that the concentration of legally restricted additives will continue to decrease in the material flow as new PVC formulations enter the recycling flow. In addition, PVC transformed from recycled materials is more resistant than virgin plastic due to the chemical transformation undergone by the various stabilizers it contains, and it has been shown that PVC can be recycled up to 10 times without degradation and loss of quality, which gives it a useful life in the construction industry of 350 years (PRW 2020).

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However, the problem of additives with regulatory restrictions, existing in old formulations, continued to constitute a barrier to the circular economy and, therefore, in 2018, the European Commission (EC) decided to take steps to develop a specific decision-making methodology for support decisions on the recyclability of waste containing hazardous substances. This methodology, which was due to be completed by mid-2019, would take into account the overall cost-benefit of recycling a material compared to its disposal (including incineration with energy recovery). However, this work was not completed in the scheduled period and, in February 2020, most members of the European Parliament voted against a derogation—proposed by the European Commission—that would have allowed PVC products to be placed on the market containing controlled levels of “additives subject to regulatory restriction,” mainly lead-based stabilizers (PPE 2020). This vote went against the recommendation of the board of the European Chemicals Agency (ECHA), which showed that allowing this restricted use for 5 years was the best waste management option for long-lasting PVC products, such as pipes from infrastructure and window profiles replaced in buildings. Those responsible for the “VinyPlus” program also deplored the result of the vote and added that, in the absence of alternative options, this means that the majority of PVC recycled in the EU—almost 740,000 tons in 2018, no longer considering 2019 and 2020—will be diverted to landfill or incineration. The difficulty imposed by this regulation is compounded by other legally restricted additives—phthalate-based plasticizers—also used with plasticized PVC. Many phthalates have been restricted by ECHA, including bis(2-ethylhexyl) phthalate (DEHP), which has been widely used as a plasticizer in vinyl floor coverings. In 2016, the European Commission supported a recommendation by ECHA to grant a four-year authorization for the use of DEHP, in recycled PVC by three PVC recycling companies. The lawsuit was challenged by the environmental NGO ClientEarth, which took the Commission to the Court of Justice of the European Union, a process that is still pending. In addition to the restrictions associated with phthalates, the European Commission has decided to proceed with plans to classify titanium dioxide (TiO2) as a category 2 carcinogen, due to the potential risks of inhalation, which also affects most white PVC products (CW 2019). The REACH and CLP (“Classification Labeling Packaging”) regulations indicate that TiO2 is not toxic, but only dangerous due to its particulate nature (typical of nanomaterials), and should therefore be treated taking into account occupational exposure limits. Applying the category 2 carcinogen classification means that products containing TiO2, such as plastics and paints, will be labeled as hazardous, even when there is no risk of inhaling TiO2. In the circumstances, recycling and waste management are critical areas of concern, as any product that contains more than 1% TiO2 will become hazardous waste and cannot be recycled.

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7.1.3 Mitigation Measures The incorporation of additives of biological origin in recycled PVC contributes to obtaining more ecologic (“green”) products. Amorphous polyhydroxyalkanoate (α-PHA) can be used as a processing aid and as a performance improvement additive in formulations containing recycled PVC. Α-PHA, of high molecular weight, has a good potential in the production of extruded rigid products used in construction. It is highly miscible with virgin and recycled PVC, acting as an effective compatibilizer to successfully incorporate recycled PVC in a virgin PVC matrix or, for total replacement of virgin PVC with recycled PVC (PPE 2016). In addition, PHA products can remain in the formulation indefinitely because they anchor the formulation components, including plasticizers and other additives, to the PVC matrix. Α-PHA-based additives already exist on the market, and it is anticipated that in the short term there may be at least one PHA bioplastics factory capable of producing 10,000 tons/year (CW 2019).

7.1.4 Recycling Methods Mechanical recycling of PVC, separated at source, is a practical, relatively simple and common technique. Suitable post-use products are those that are easy to identify and separate from the waste stream, or that can be kept relatively clean, ending up as a high-quality recycled product for use in the existing range for PVC applications. Examples of this are piping (usually also recycled for pipes), window profiles (recycled for new profiles or pipes), floors, coatings, and roofing membranes. The materials used in flexible (non-rigid) applications are sometimes recycled through the “Vinyloop” process or reprocessed in products such as mats, carpets, and traffic and signage cones. Composite products containing PVC are also recycled. However, it is not possible to obtain these pure PVCs, so the recycled PVC composite is only suitable for applications where a mixed composition can be tolerated. When homogeneous plastic flows are not available, suitable recycling schemes for mixed plastics, including PVC, can be used. Mixed plastic waste, containing up to 15% PVC, does not present technical problems, although the quality of the recycled material is adequate for a more limited number of applications. In fact, there are a number of compositions or products made up of multiple materials that, when sent for recycling, cannot be economically classified into single polymer streams. These materials are closely linked to each other for performance reasons and their separation is not yet economically viable. For these cases, the chemical recycling method can be used for recycling PVC, whose current technologies are less sensitive to unclassified or contaminated waste

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products, and which allow the extraction of raw materials and increase the future recycling capacity for larger ones. Quantities of mixed waste.

7.1.5 PVC Recycling Statistics The starting point for PVC recycling was with the first Voluntary Commitment of the PVC industry, called Vinyl 2010, which made it possible to reach the level of 260,000 tons of recycled PVC in 2010. Afterward, this program was replaced by VinylPlus, which constituted the second program created by the European PVC industry, aiming to increase the recycling of window profiles, pipes and fittings, cables, rigid and flexible films, and a whole series of vinyl coverings. The focus of the VinylPlus program is not only to achieve goals of the circular economy, but also to address other forms of sustainability, namely the topics of energy and climate change, supply and production of sustainable material, and the responsible use of additives. These key issues were integrated into the sustainability certification scheme for PVC products in civil construction (“VinylPlus” seal), considered the sector with the highest sustainability performance and contribution to the circular economy. To date, ten companies have received the “VinylPlus” label, for more than 100 PVC products manufactured in 18  units located in Europe (PRW 2020). Thus, in the VinylPlus program, recycling targets are reinforced by traceability and certification schemes, in order to guarantee the safety and quality of recycled materials and processes. The initial goal of this voluntary scheme was to recycle 800,000 tons of PVC by 2015. In 2018, the “VinylPlus” program made a new commitment to recycle 900,000 tons by 2025 and then one million tons per year until 2030 (PRW 2018). During 2015, the industry increased PVC collection rates by around 7%, reaching around 515 thousand tons. The window profiles sector alone saw collection rates increase by around 15%, to almost 233,000 tons in 2015. The windows and profiles sector continued to account for most of the volume (around 45%). The remaining main applications were electrical cables, rigid films, pipes and fittings, and flexible PVC coatings (for waterproofing roofs and other waterproofing membranes, with different applications). However, not all projects have been successful. For example, a project promoted by “The European Plastic Pipes and Fittings Association” (TEPPFA) to recycle pipes and fittings suffered a 10% drop in collections, falling below 50,000 tons in 2015, due to uncertainties related to the regulatory framework of the EU on the use of recycled PVC.  This caused the pipe industry to postpone investments in new products, namely multilayer pipes incorporating recycled (PPE 2016). Electric wire and cable applications today represent the largest flexible PVC application sector in Europe, absorbing around 7% of the PVC resins manufactured and accounting for 46% of the cable market in Europe. PVC cables today represent

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one of the main sources of recycled PVC, with more than 127 ktons of recycled cables in 2016, out of a total of 568,696 tons of recycled PVC (PVC4cables 2017). Residual PVC-U profiles accounted for 62% of the total recycled PVC in the UK in 2016, with the remainder corresponding to piping, rigid and flexible PVC films, and cabling (SpecialChem 2017b). According to the VinyLPLus program, around 300 ktons of PVC window profiles were recycled in Europe in 2017 (PRW 2018). The “VinylPlus” program reached a level of almost 740,000 tons of recycled PVC in 2018. In 2019, more than 771 ktons of PVC were recycled (PRW 2020), surpassing the final target foreseen, a year earlier, as projected by the “VinylPlus” program, which in 2018 established a new goal to recycle 800 ktons/year of PVC by the end of 2020 (PPE 2020). In 2019 the program reached 96% of that target (771,000 tons of PVC). However, the Covid-19 pandemic provoked severe market disruption during the first half of 2020 and recycling operations decreased in Europe, as many companies were forced into lockdown. A complete recovery from the first wave of Covid-19 was not possible and, thus, PVC waste recycling within the VinylPlus framework still reached near 731,400 tons—above 91% of the program’s 2020 target (PPE 2021a). Therefore, the PVC industry is well on its way to meeting VinylPlus’ recycling targets for 2025 (900,000 tons), and 1 million tons/year by 2030, which are in line with EU policy initiatives to encourage the recovery, recycling, and reuse of plastics. The “VinylPlus” program created a subprogram, in 2014, called “RecoMed,” to recycle hospital material in PVC, which allowed 9000  kg of masks and flexible pipes to be recycled in hospitals in the UK during 2019, making a total of one. Total of 24 tons since 2014 (PRW 2020). This subprogram has been extended to other countries, namely Australia, Canada, South Africa, Guatemala, and Colombia.

7.1.6 Sustainability Label The “VinylPlus” program, in collaboration with the Building Research Establishment (BRE) and the company “The Natural Step” (TNS), has developed a new sustainability label in order to create a long-term sustainability structure for the entire chain of PVC value across Europe and the world. Based on sustainability criteria, including source sources and additives, the “VinylPlus” product seal is open to all PVC buildings and construction products. The “VinylPlus” product label is designed to make easier, for customers and markets, to choose the most sustainable and highest performing PVC products. The program covers the construction sector (buildings and construction products) and concession audits are carried out by specialized companies, based on strict criteria, including the supply of PVC resin and additives, the circular management of controlled recycling, recycling policies sustainable energy, organizational and supply chain management requirements (PRW 2019d).

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7.2 Recycling of Polyurethane 7.2.1 Generalities Due to its varied applications and commercial success, an increasing amount of PU waste is produced annually. These wastes comprise end-of-life and post-consumer products, as well as wastes from the manufacture of polyurethanes. The latter is the result of imperfections in the production and processing methods and can constitute up to 10% of the PU produced. However, waste from end-of-life and post-consumer PU products is a much bigger problem, because they are generally contaminated or deformed and, therefore, are less likely to be reused (Kemona and Piotrowska 2020). Unfortunately, landfill is still the most common way to process PU waste. The fraction of PU discarded in this way reaches almost 50% of the waste (post-­ consumption or post-production combined). However, the landfill should be considered a temporary storage place for waste awaiting recovery and further processing, instead of the final solution (Kemona and Piotrowska 2020).

7.2.2 Constraints Associated with PU Recycling The toxic products of the combustion and pyrolysis of PU products are, in addition to hydrocyanic acid (HCN) and carbon monoxide (CO), nitrogen oxides, benzonitrile and other nitriles, and toluene diisocyanate (TDI) of aromatic foams. In addition, flame retardants present in PU products can produce highly toxic acid gases, dioxins/furans and bicyclic phosphate esters, or toxic zinc ferrocyanide (used as a smoke suppressant in PU and other polymers) (Zevenhoven 2004).

7.2.3 Mitigation Measures The emission of PU smoke can be reduced by increasing the crosslinking of the material, using cyanurate structures, or by introducing smoke suppressors into the polymer structure, for example, alcohols such as furfuryl alcohol (Zevenhoven 2004).

7.2.4 Recycling Methods Rigid polyurethane (PUR) foams are produced and consumed in large quantities in the construction industry, for the constitution of thermal insulation plates. This foam, when applied in construction, can have a typical useful life of 30–80 years.

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PU waste can be mechanically recycled by one of the following four methods (Nikje 2011): 1. Grinding and spraying: process for reusing ground PU waste as a filler in PU foams or elastomers. It involves two steps: (i) crushing the PU material into a fine powder; and (ii) mixing the powder with the polyol component to make a new PU material. 2. Reprocessing with adhesives: PU is molded from pieces of fragmented flexible PU foam, joined by a binder. Its high relative density and excellent resilience make it suitable for applications in pavements and others with a view to dampening vibration. The sequential flow of the process consists of collecting, sorting, crushing, coating the surface with binder, compression molding, activating the adhesive binder, curing the adhesive binder, and producing recovered parts. 3. Compression molding and injection molding, without adhesives: this method of reprocessing without adhesives involves the molding, by compression or injection of PU particles, at 180 °C of temperature and at a pressure of 350 bar to make particles flow together without any binder. In addition to mechanical recycling, energy recovery from PUR foam waste from construction and demolition waste is also an interesting option and is the only suitable disposal method for PU waste with no market or applications (Zevenhoven 2004; Nikje 2011). In the thermochemical recycling (incineration) of PU products, an attempt is made to use the waste stream as a source of energy, fuel, or to obtain some monomers with economic value. This process results in a volume reduction of about 99%, which has a great impact on the reduction of the landfill area of this material, while destroying chlorofluorocarbon (CFC) compounds and other environmentally damaging foam expansion agents. Thermochemical recycling comprises the following methods (Nikje 2011): –– Pyrolysis: uses a heated, oxygen-free environment for the pyrolysis of plastics in gases, with the release of CO, methane (CH4), HCN, ammonia (NH3), and nitrogen monoxide (NO), in addition to small amounts of ethylene (C2H4) and acetylene (C2H2), as well as mixtures of monomers (in the form of a viscous red single-phase oil with a viscosity that increases over time). –– Gasification: consists of an exothermic process that produces heat, ash, and gas. In this process, the residual stream is heated and then combined with air rich in molecular oxygen (O2), forming a synthesis gas (CO + H), which can be used in refinery processes for the production of different chemicals, for example, ammonia and alcohols. The molecular hydrogen (H2) and CO produced can also be used in the production of polyethers and isocyanates, respectively. –– Hydrogenation: a process that consists of a compromise between pyrolysis and gasification methods. Hydrogenation contains an additional step in relation to pyrolysis to produce even purer gases and oils through a synergistic combination of temperature, pressure, and hydrogen.

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Chemical recycling comprises the following methods (Nikje 2011): –– Hydrolysis: the steam superheated to 200  °C converts the PU foam, in about 15 min, into a liquid with two phases, using a medium without oxygen and under pressure. Hydrolysis is the reaction of PU with water, producing polyols and amine-based products. The recycled polyols can be used as monomers in the formation of PU and the amine intermediates can be reused to produce other PU components, for example, isocyanates. PU residues can be conveniently and economically converted to polyethers and polyamines containing active hydrogen, by contacting PU with water, in the presence of a strong base and an activating agent. –– Aminolysis: is the reaction of PU residues with amines such as dibutylamine, ethanolamine, lactam, or lactam1 adducts under pressure at elevated temperatures, using potassium and sodium hydroxide as the main catalysts. –– Glycolysis: is the most widely used chemical recycling method for PU waste. The main objective of this process is the recovery of the valued monomers, namely, polyols from PU waste, for the production of new material. Basically, glycolysis involves heating the PU residues (crushed) to 180–220 °C, in high-­ boiling glycols, in the presence of a catalyst. Glycols act as agents that promote the breakdown of bonds and the release of polyols and amines, binding to the functional groups of urethane. Finally, biological degradation methods, through fungi, bacteria, and enzymes, must also be considered (Kemona and Piotrowska 2020).

7.2.5 PU Recycling Statistics Through a search of the specialty literature, it was not possible to find statistics data on PU recycling, either from construction products (thermal insulation products and adhesives/sealants) or from products containing PU from the furniture industries (couches), textiles (clothing and shoes), and automobiles (seat cushions and instrument panels).

 The designation “lactam” results from the combination of the words “lactone” + “amide” and is a cyclic amide. 1

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7.3 Recycling of Polypropylene and PPolyethylene 7.3.1 Generalities Polypropylene (PP) and polyethylene (PE) are polymers of the polyolefin family and are widely used in the construction sector. PE is mainly used in pipes, cables, and conduits, as well as the main constituent of the matrix of wood-plastic composites (WPC). PP, on the other hand, is more used in pipes, of smaller diameter, for the distribution of hot water inside buildings and for sprinkler networks, in low-risk applications. As mentioned for PVC, it is also expected that the HDPE pipes and conduits used in water, gas, and sanitation infrastructures, with large diameters, will have a useful life of more than 100  years and, therefore, the availability of recycled PE pipes is still very limited.

7.3.2 Recycling Methods PE and PP are polymers of the polyolefin family and are widely used in the construction sector. PE is mainly used in pipes, cables, and conduits, as well as the main constituent of the wood-plastic composite (WPC) matrix. PP is more used in pipes, of smaller diameter, for hot water distribution inside buildings and for sprinkler networks, in low-risk applications. In a study carried out at LNEC (Portugal), it was possible to confirm the applicability of recycled PE in pipes for sanitation, with satisfactory performance.

7.4 Recycling of Plastic Mixtures 7.4.1 Difficulties In contrast to the case of single-component products, the separation, purification, and recycling of thermosetting plastics and mixtures of various plastics, coated and laminated plastics, and polymeric textile products remains difficult and constitutes a major challenge. Post-consumer recycled materials (PCR) are made up of a mixture of various types of resin and colors with varied rheologies (high variability flow). In addition, the levels of additives that exist in polymers are unknown, and it is generally quite complex to identify hybrid materials in post-consumer waste. Another problem with PRCs is the possibility of bad odors and organic contaminants.

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Unpleasant odors are usually caused by amines and/or volatile sulfur components formed by post-processing chemical reactions. Contaminants in PCR include incorrectly classified polymers, as well as adhesives and other low molecular weight polymer species. Contaminants and degraded material also cause a bad odor in the PCR. Mixtures of polymers are difficult to homogenize, as some polymers do not have any specific chemical interaction or reaction between them, such as, for example, PET, PE, and PVC. Thus, the mixtures may have low miscibility between the polymers and, due to the high interfacial tension, the morphology of the recycled mixture may not be stable.

7.4.2 Mitigation Measures A possible approach to mitigate the difficulties of recycling plastic mixtures is to develop the methods of separation and cleaning, as well as to design the products to facilitate the recycling process, in particular in the case of hybrid products and with regard to the incorporation of additives.

7.4.3 Recycling Methods The best methods for recycling plastic mixtures are those previously described in Sects. 4.13.2.4 (solid state shear pulverization) and (molding process by powder impression). However, although society is trying, through regulatory changes, to limit incineration, export, and landfill, unfortunately, these are still widely used methods for the disposal of these materials (Ignatyev, Thielemans and Vander Beke 2014).

7.5 Recycling of Composites 7.5.1 Generalities As composite materials and fiber reinforced plastics (FRP) have high durability, disposal at the end of their useful life has not been a major problem to date. The greatest amount of waste from composite materials has resulted from the production process of these materials, since the production processes of composites are continuous and the remaining portions of the raw material and final product, FRP parts and sections, become unusable (Yazdanbakhsh and Bank 2014).

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However, it must be considered that many composite products are currently approaching the end of their useful or functional life, resulting in an increasing rate of waste accumulation. Considering that recycling of end-of-life composite materials is a complex process, it will be necessary assessing the interdependencies of serial recycling processes, in order to obtain solutions throughout the value chain, from collection to the creation of a new application.

7.5.2 Constraints Associated with the Recycling of Composites Hybrid post-industrial and construction waste, as well as that of composites, are easier to identify than mixed flows of post-consumer plastics, so the problem with these materials does not lie in this aspect. The main problems for recycling plastics and fiber-reinforced composites are as follows: –– Most composites use matrices of thermosetting resin, which are not easily recycled because they are cross-linked and cannot be reprocessed, unlike thermoplastics that can be repeatedly melted. The complexity of recycling is increased because these materials also contain a considerable fraction of fiberglass and fillers, such as calcium carbonate and sand. –– Composites are commonly combined with other materials (metal fixings, honeycomb structures, hybrid composites, etc.). –– The value of the material constituents of the composites (and therefore of any recovered waste or demolition material) is low. –– Composite materials have high strength and stiffness, which is a disadvantage during reprocessing, as it requires the use of heavy machinery for crushing and grinding. –– Polymer composite products are also generally bulky and light, with sections or profiles subject to complex geometry by engineering design, which makes the transport of non-crushed waste economically unviable. –– Carbon fiber products can be difficult to decompose or recycle. It is only possible to crush or break them at high temperatures or using specific chemicals to recover the carbon fiber incorporated in them. In addition, the process can also damage the carbon fiber and destroy the matrix resin materials in the composites. Thus, recycling and reusing FRC and FRP waste is more difficult and expensive than for other materials widely used in construction (particularly metals, wood, and concrete). The reduced recyclability of composite materials is seen as a fundamental barrier to the development or even the continued use of these materials in some markets.

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7.5.3 Mitigation Measures It is necessary to identify applications and develop methods to reuse composite materials, including manufacturing waste. It is also necessary to establish a viable recycled composites supply chain that allows for the dismantling, classification, and recycling. As decisions made at the beginning of a product’s design have implications for its life impact, it is important to develop a methodology that guides designers to consider the sustainability of their product at all stages of the design process and manufacturing, facilitating the identification and separation of various components made up of different materials in hybrid products, during the recycling process. The Hybrid Project, launched in 2016 by the “European PVC Window Profile and Related Building Products Association” (EPPA), is a good example, aiming to classify the recyclability of hybrid PVC profiles.

7.5.4 Recycling Methods Due to the difficulties in recycling composites, incineration with energy recovery, or in combination with the production of cement, has been the main option to eliminate waste from composite materials. However, environmental issues and legislative limitations associated with landfill and the incineration of PRF waste, made it essential to develop efficient and economical FRP recycling routes, with associated supply chains, as constituting an increasingly viable alternative for the management of this waste (Yazdanbakhsh and Bank 2014). Although several research projects have been carried out to develop recycling processes and find ways to effectively use the recycled material in new or existing applications, most have aimed at recycling carbon fiber composites, due to the cost differential (carbon fibers and virgin fibers have a value of about 10 times the value of glass fibers). Thus, several recycling processes have been developed for FRC and PRF, which can be categorized into two main groups: the recovery of fibers from the polymeric matrix and mechanical recycling. The recovery of the fibers from the polymeric matrix uses an aggressive thermal or chemical process to break the polymeric chains of the thermosetting matrix, so that the fibers can be released and separated. These recovery processes are expensive and are only economically justified for extracting expensive fibers, such as carbon fibers, because carbon fibers have high chemical stability and generally their superior mechanical properties are not significantly affected during recovery. The main recovery processes are as follows: –– Pyrolysis: many of the recycling projects for plastics and composites reinforced with carbon fibers (PRFC or CRFC) have concentrated on a partial pyrolysis

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process, where the resin matrix is burned with limited oxygen concentration, up to a temperature of 450–700 °C, allowing the recovery of fibers and the production of fuel. In this temperature range, the polymeric matrix is volatilized into molecules of lower molecular weight, while the fibers are minimally affected and recovered (Yazdanbakhsh and Bank 2014). Carbon fibers, processed in this way, retain 90% or more of their original mechanical properties. Several variants of pyrolysis processes, using fiberglass and carbon composites, have been tested in several countries. The microwave pyrolysis processes were developed in the UK (Nottingham University), USA, and Germany, with the aim of reducing the energy consumption of the recycling process (Job 2010). –– Fluidized bed (oxidation): process very tolerant to mixed and contaminated materials, developed at Nottingham University, which involves feeding waste consisting of composite pieces of PRFC and PRFV, reduced to about 25 mm, in a bed of sand. The sand is fluidized with a stream of hot air at a temperature of 450–550 °C. The polymer decomposes and vaporizes, releasing the fibers and charges that are carried in the gas stream. The fibers and fillers are then separated, and the resin products are completely oxidized in a combustion chamber, where thermal energy can be recovered (Job 2010). Glass fibers lose about 50% of their tensile strength, but retain their rigidity if processed at 450 °C, which is sufficient to remove the polyester resin. At higher temperatures, the fibers lose even more strength. Carbon fibers have a loss of strength of about 20% when processed at 550 °C (suitable for epoxy resin), maintaining the original stiffness. –– Chemical recycling (solvolysis): recycling process that allows the recovery of chemical products from the resin. FRP residues are subjected to the action of a reactive (acidic) material at low temperature (usually less than 350 °C), resulting in the decomposition and separation of the material from the polymeric matrix (Yazdanbakhsh and Bank 2014). Nottingham Trent University investigated this process, using supercritical propanol to dissolve the resin in epoxide composites and promote carbon fiber separation. Supercritical water and methanol were also used to recycle fiberglass composites (Job 2010). However, chemical methods can cause negative environmental impacts if they use hazardous materials.Todos os métodos de reciclagem mecânica de compósitos envolvem a quebra do material e a redução sucessiva do tamanho das partículas dos materiais reciclados por meio da trituração, moagem ou outro processo mecânico semelhante; os pedaços resultantes podem ser segregados, usando peneiras e ciclones, em produtos em pó (ricos em resina) e produtos fibrosos (ricos em fibras) (Yazdanbakhsh and Bank 2014). All methods of mechanical recycling of composites involve breaking the material and successively reducing the particle size of the recycled materials through crushing, grinding, or other similar mechanical processes; the resulting pieces can be segregated, using sieves and cyclones, into powder products (rich in resin) and fibrous products (rich in fibers) (Yazdanbakhsh and Bank 2014). Mechanical grinding is the most widely used approach for recycling fibrous composite materials with thermosetting polymers. After the reduction of adequate

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size, the material is ground and classified into different fractions. This approach is economically challenging, as it is difficult to produce finely ground recycled at a cost comparable to the filler charges currently used, such as calcium carbonate (Job 2010). Carbon fiber products, on the other hand, are more difficult to mechanically recycle, as carbon fiber can be damaged in the process.

7.5.5 Applications of Recycled Composites Recycled composites have been widely used in cementitious materials (concrete and mortars), to replace aggregates (fillers). The mechanical properties of cementitious materials containing FRP and recycled FRC, mainly the compressive strength of cementitious materials, depend on several factors (Yazdanbakhsh and Bank 2014), namely the type of cementitious material (concrete or mortar), the proportion of water/cement and mixture and proportions of cementitious material and constituents, the type of FRC residue (reinforced with glass or carbon fibers), the different fiber contents and types of resin and, finally, the particle size of the recycled FRP and the aggregate that has been replaced (thin vs. thick). It has been reported that the partial replacement of concrete and mortar aggregates with mechanically recycled FRP does not significantly affect the durability of cementitious materials, but that it significantly reduces their mechanical properties (Yazdanbakhsh and Bank 2014). On the other hand, it was reported (Job 2010) that the addition of 5% residual powder of glass fiber reinforced plastic (GRP) to the concrete, with superplasticizer (2% cement content), increased the compressive strength by about 14% compared to normal test pieces. It is also reported in another study that the partial replacement of aggregates of sand by GRP residues has an incremental effect on the flexion and compression strengths of the tested samples, regardless of the type and content of GRP residues (Ribeiro 2011; Castro 2013). FRP residues have also been used in the production of wood-plastic composites (WPC), shower trays, chipboards, asphalt, and rubber (Job 2010). Wood-containing composites can be recycled again. But they can contain unpleasant odors, associated with natural fillers, such as lignin and cellulose. The recycled plastics reinforced with ground fiberglass can be used in rubber composites, in contents up to 50%, to increase the hardness and the elasticity modulus of the rubber and to improve the damping capacity and the acoustic properties (Job 2010).

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7.6 Illustrative Cases of Success 7.6.1 Recycled PVC The Rewind project collected 100,000 tons of PVC windows in Germany in 2015. This project was created to promote the recycling of used PVC doors and windows, and gave rise to the appearance of some large-scale projects in Germany. One of these major projects was implemented at Askren Manor, west of Schweinfurt, where an old abandoned US Army settlement was demolished for the site to be rebuilt, and is now renamed “Bellevue.” On this 28-hectare plot, there were 34 three-story residential blocks (approximately 700 residential units), 13 semi-detached houses, and several common facilities, allowing about 2500 PVC windows to be recycled. These windows were and the recycled PVC is being used again in the manufacture of windows (PRW 2018). Deceuninck recycled 12,000 tons of rigid, post-industrial, and post-consumer PVC waste in 2017, part of which was reused for new value-added products, such as window profiles and elements for thermal cutting reinforcement (PRW 2018). In 2019, Deceuninck opened a new recycling line in Diksmuide, Belgium, which provides for recycling up to 45,000 tons/year of PVC (PRW 2020). The input materials come from post-industrial waste (waste from customers, as well as waste from their own manufacturing process) and first-generation PVC windows that are gradually being replaced after 30–40 years of service life. The company expects the new facility to divert more than 2  million windows a year from landfills or incineration. Recycling technology is used to recycle PVC profiles of all colors and compositions; including those that contain fiberglass reinforcement. The old profiles are decontaminated, classified by color and granules, to be used in the extrusion of new PVC profiles. German company Veka, another major manufacturer of PVC profiles, made a major investment in PVC recycling in the UK in 2018, spending more than £8 million to convert a former metal recycling plant, located in Wellingborough, into a unit recycling PVC windows using post-industrial and post-consumer waste. With the addition of this new plant in the UK, to the two that already operate in Germany and France, Veka will have a combined recycling capacity of more than 100,000 tons per year of PVC window waste (PRW 2018; 2019d). Veka aims to produce high-­ quality polymers for use in a variety of sustainable construction products, such as new window profiles and door frames. The company Veka Recycling has recycled more than 10 million U-PVC facilities since 2007. The company has a closed-loop recycling process and says that its recycled products can maintain an adequate performance for another 30–40 years. Window profiles made of PVC-U can be reused for more than 300 years before they become unsuitable for recycling (PRW 2020). Veka’s PVC-U waste recycling process for the production of PVC-U pellets, i.e., recycled materials used to manufacture new door and window profiles, is carried out in four stages:

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–– –– –– ––

Window and door profiles are collected and sent to the recycling center. PVC-U waste is then mechanically crushed. All metallic and magnetic materials are then removed. The various parts of the products are then separated into different colors and reduced in size. –– TThe final step in the recycling process is compression, followed by filtration and the pelletizing process. British window manufacturer Eurocell also made commitments related to PVC recycling and created the Eurocell Recycle brand. Over the past 6 years, Eurocell has invested £5 million to expand its plant in Ilkeston, Derbyshire, with a view to recycling PVC. The plant has potentially contributed to the 61,500 tons of PVC, at the end of its life, that Eurocell has diverted from the landfill over the past 10 years (PRW 2018). In 2018, Eurocell contributed significantly to 3.6 million structures not going to landfill (PRW 2019c). Eurocell Recycle offers a complete closed-­loop process for the collection and processing of PVC-U profiles used in the UK, intended to be re-extruded and transformed into new windows, doors, and construction products. Eurocell also continued to increase recycling, using 13,400 tons of recycled PVC compound in the manufacture of coextruded rigid profiles during 2019, which represented 23% of the total consumption of recycled material in 2018 (PPE 2020). The Salamander company received the 2020 Sustainability Award from the “Deutschland Test” and “Focus Money,” in particular, for the development of the Greta ecological window system, produced within the highest sustainability standards (PRW 2020). All PVC used comes from old windows and production waste. As modern production methods do not allow to obtain totally smooth surfaces using recycled PVC, the company used special surface textures, with open pores, to create a profile with a similar appearance to concrete, allowing to maintain the typical acoustic and thermal insulation standards of the PVC windows, but creating different architectural styles and different types of windows. Greta profiles are part of the flexible modular system GreenEvolution and can be individually adjusted for each project. The design of fine lines allows the construction of large glass surfaces to obtain maximum light and improve the quality of the space, which is vital in old renovated buildings and new modern buildings. Two Italian companies (Noise SRL and VBN) have developed an acoustic barrier made of recycled PVC, with the aim of improving or replacing the existing noise barriers in aluminum, porous concrete, wood, and stainless steel, as well as another variety of natural barriers. These acoustic barriers are certified according to the highest requirements of mechanical resistance and acoustic performance required for this application, and are characterized by an attractive design that adapts well to the environment. They comply with the sound absorption and sound insulation classes A5 and B3, according to the standardization in force. Inside, the barrier has a layer of polyester fiber for sound absorption. Each panel, which is up to 4 m long, is made of 85% recycled PVC. The external structure (15%) consists of virgin PVC resin. The panels are manufactured by tubular extrusion, in a continuous process, which creates a homogeneous product, both in terms of the constituent material and

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its mechanical resistance. They can be fully recyclable, with almost any color, and combined with existing barriers. They do not need painting or varnishing and are designed to last up to 25 years (PPE 2016). The German company Vinylit Fassaden developed a material, in recycled PVC of window profiles, called “VinyPlus”, for the facade of buildings. With this material, the facade does not require maintenance. British company MK Electric uses recycled pieces of extruded PVC in its production process, obtaining products made from 100% recycled plastic, intended for cables, skirting boards, and rails. PVC-U waste, including production leftovers and remnants of cut, is collected by PVC recyclers in factories in the UK and Ireland. This material is then processed to remove all contaminants and ground to form a high-quality powder mix for reuse. Linpac recycles 98% of PVC waste at the Pontivy plant (SpecialChem 2017a). The vapors and fumes released, as by-products of the manufacturing process, are captured and condensed, for later manufacture of plasticizers, which are used as additives to improve the plasticity properties of materials in products, such as garden hoses. The remaining 2% of PVC waste is sold by Linpac to external customers for use in the manufacture of rigid and flexible products, namely pipes, cables, shoe soles, and car mats. Linpac recycled 227 tons of PVC waste in 2016, including 42 tons of plasticizers that were reused externally. In the past 10  years, Linpac has

Fig. 7.2  Auto-cad design of a set of semi-detached houses with the virtual roof constituted by Tectum’s prefabricated rainwater collection system, constructed from recycled PVC pipes (Kristen Tapping 2021)

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recycled more than 3000 metric tons of PVC waste at its Pontivy plant, an amount that has been sold for reuse. The company Tectum created insulating covers using recycled PVC pipes (Fig. 7.2). The pipes are cut in half and placed in opposite directions to divert the water to a chute and from there to a water storage container, both made from recycled PVC pipes. The pipes are pre-assembled in panels to make installation faster and more economical (Kristen Tapping 2021). A pilot project was launched, financed by the European Regional Development Fund, called PVC Upcycling, with the objective of recovering the PVC component of electrical cables and recycling it into products with a low level of environmental impact, in the form of powder and granules of PVC in new products for construction (PRW 2020). Inovyn introduced a biobased PVC line, called Biovyn, using a supply chain fully certified by Roundtable on Sustainable Biomaterials (RSB). The material is fully recyclable. Manufactured in Rheinberg, Germany, Biovyn is made with bioethylene, a renewable raw material derived from biomass that does not compete with the food chain. Biovyn is certified by the RSB as replacing 100% fossil raw material in its production system, allowing a greenhouse gas savings of more than 90%, compared to conventionally produced PVC (PRW 2019d). The results achieved with this product showed that it is possible to replace the use of virgin fossil raw materials without compromising the quality of the final product, in terms of durability, flexibility, and recyclability; which makes PVC one of the most widely used sustainable plastics in the world. The company Vynova, a European PVC manufacturer, launched what is considered the world’s first line of PVC resins with circular characteristics, to which it attributed the brand “VynoEcoSolutions.” These resins are certified under the seal of “International Sustainability & Carbon Certification” (ISCC) structure, according to a mass balance approach. The resins are made at the company’s facilities in Beek, the Netherlands, and Mazingarbe, in France, using ethylene raw material “Trucircle” supplied by the raw material manufacturer SABIC, from its unit in Geleen, the Netherlands (CW 2020). Ethylene is produced from oil resulting from the chemical pyrolysis of recycled plastic waste, reducing CO2 emissions by 50%. According to Vynova, circular resins make it possible to obtain products with the same quality and performance characteristics as conventional PVC materials. Manufacturers of faithful products can easily process these resins in conventional equipment, used to manufacture products for rigid and flexible applications.

7.6.2 Recycled PU Since 1996, Germany has had a great capacity for recycling PU waste to manufacture heating pipes under building floors (Weigand 1996). In 2011, a permeable elastic floor was invented, which uses recycled PU residues, obtained from the soles of shoes, toys, appliances, and vehicles (Kang 2006).

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The addition of micronized PU powders, obtained from flexible PU residues, to urea-formaldehyde resins and phenol-formaldehyde resins, significantly improves the performance of panels prepared with these resins, namely plywood and agglomerate (Mansouri and Pizzi 2007).

7.6.3 Recycled Polyolefins (PP and PE) The manufacturer Borealis of raw materials, acquired the recyclers “MTM Plastics,” in Germany, and Ecoplast, in Austria. Borealis has an annual production capacity for recycled polyolefins of between 80,000 and 100,000 tons. BOREALIS is developing a technology called “Borcycle” for the production of compounds from recycled polyolefins, which is designed to be scalable and modular, capable of producing high—quality recycled materials. Borcycle is used by BOREALIS internally to respond to the growing demand for high-quality PP and PE materials, incorporating recycled materials (PRW 2019b). Canadian company Greenmantra Technologies has technology to chemically recycle post-consumer and post-industrial LDPE, HDPE, and PP, and conversion to lubricants and additives for use in the manufacture of plastics and other construction materials, such as asphalt and roofing (CW 2019). Recently, Greenmantra started supplying a series of additives for the production of wood-plastic composites based on PE and PP wood-plastic composite, which provide an increase in strength and stiffness to the WPC. Finally, it should be noted that a few years ago, Lu and Korman carried out a study that shows the potential applicability of recycled HDPE reinforced with hemp fiber to the product applicable to construction (Lu and Korman 2013).

7.6.4 Recycled PS The Canadian company “Greenmantra Technologies” started, in 2019, a joint project with the manufacturer Ineos of styrenic products to chemically convert post-­ consumer recycled PS into monomers, to feed the polymerization process of “Ineos Styrolution” (CW 2019).

7.6.5 Recycling of Mixtures of Plastics Fraunhofer is developing a matrix for wood-plastic composites (WPC) from mixtures based on recycled PP and/or PE, PA, PMMA, ABS, and PC, with wood sawdust or other lignocellulose fibers to improve properties mechanical.

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The company “Plastinum Polymer Technologies” holds the patent rights to a mechanical process for mixing immiscible plastics, called Blendymer, which allows plastic waste to be fully recycled instead of being landfilled or incinerated. It is capable of bonding polymers that were previously considered to be incompatible. Plastinum’s “Blendymer” ™ technology solves the two main problems of recycled plastics (insufficient quantity and unsatisfactory quality). It supplies high-quality, consistent material in an unlimited quantity (thanks to the unlimited availability of mixed plastic waste), and manages to do so at a stable and highly competitive price. In 2009, Plastinum opened a production line with a capacity of 10,000 tons/year using its Blendymer recycling process for the production of thermoplastics “Infinymer” and “Ultrymer,” from post-consumer mixed plastic waste. Plastic recycling technology company Recycling Technologies, in collaboration with the Center for Sustainable Chemical Technologies (CSCT) at the University of Bath, is developing a method for chemical recycling of plastic mixtures, to create molecules that can be used to manufacture new plastics or other value-added products. In order to increase the efficiency of the process, they tested the feasibility of incorporating analytical technologies (“Oscillating Baffle Reactor”) in the Recycling Technologies pyrolysis machine to improve the quality of the raw material, allowing it to be used in the manufacture of new plastic without need pre-treatment. In order to increase the efficiency of the chemical recycling process, they developed a partnership with the company “Optimal Industrial Automation,” in order to improve automation of the recycling process (SpecialChem 2021a). This is an example of synergy, in which the fundamental knowledge of CSCT in polymer science, catalysis and reaction life cycle and engineering assessment, combined with industrial knowledge in recycling technologies from NiTech and Optimal demonstrate the feasibility of sustainable chemical recycling of mixed plastic waste on an industrial scale.

7.6.6 Recycling of Composites Two UK companies (Hambleside Danelaw and Filon), manufacturers of roofing products, developed mechanical grinding processes for fiberglass composites, used in limited quantities in their own roofing products (Job 2010). Filon invested in improving the energy efficiency of the milling process, thereby reducing costs, and Hambleside Danelaw invested in retaining the length of the fibers, with a view to maximizing the value of the recycled material. The company “Recycled Carbon Fiber”, formerly known as “Milled Carbon” has a pyrolysis plant in the West Midlands with the capacity to process 2000 tons/ year of carbon fiber waste, and markets recycled carbon fiber in milled and granulated forms (Job 2010).

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The University of Leeds has developed a pyrolysis process for recycling FRP with a method where the fluid pyrolysis products can be used as fuel (Job 2010). A Danish company, ReFiber ApS, uses pyrolysis in GRP waste. The resulting glass fibers are bonded with PP on insulation boards (Job 2010). Firebird Advanced Materials Inc. (Raleigh, N.C., USA) has developed a continuous microwave recycling method used to recycle PRFC and PRFV (Job 2010). Researchers at Washington State University have developed a new method for recycling carbon fiber-containing plastics (Wsu 2019). Prof. Jinwen Zhang, from the School of Mechanical and Materials Engineering, and his team, have developed a new chemical recycling method that uses weak acids, as catalysts, in liquid ethanol, at a relatively low temperature to break the chains of thermosetting polymers. To break the cured materials, the researchers raised the temperature of the material so that the liquid containing the catalyst penetrates the composite and breaks its complex structure. Zhang used ethanol to force resins to expand and zinc chloride to break critical carbon-nitrogen bonds. Thus, this method is able to preserve both the carbon fibers and the resinous material in a way that can be easily reused. Researchers at the University of Maryland College Park, Rice University, and the University of California Merced have found a viable alternative to plastic, in the form of a composite made of a mixture of graphite and cellulose extracted from wood pulp (Zhou 2019). The new composite uses hydrogen bonds between graphite flakes and nanofibrilated cellulose (NFC) to create an extremely strong material. In ballistic, tensile, fracture, and impact resistance tests and superficial hardness, the material showed remarkable results that rival steel, aluminum alloys, polyethylene compounds, and even carbon fibers (Zhou 2019). The researchers obtained values of tensile strength up to 1 GPa, tenacity up to 30 MJ/m3 and a specific strength of 794 MPa/g.cm-3 thanks to the low density of graphite and cellulose. This material is not only stronger than many steels, but also six times lighter than steel, having a specific strength greater than any existing metal or alloy (including titanium alloys). The solvent-free approach at room temperature is easily scalable and has a much smaller environmental footprint than the processes for manufacturing other structural plastic or metal materials. In addition, the compost is completely degradable in water at higher temperatures. The compost can be coated to withstand the effects of water and moisture during use. The research team is confident that the mechanical properties of the graphite-cellulose compound can be further increased, while also reducing costs, to make it an ideal substitute for existing non-biodegradable materials (Zhou 2019). A research study also made it possible to obtain a successful recycling of an aluminum matrix composite, via an electrolysis process in 1-butyl3-­ methylimidazolium chloride (Kamavaram 2005).

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7.7 Relevant Projects, Programs, and Studies The European Commission, European Community Countries and European Manufacturers’ Associations have been implementing a circular economy and encouraging the recycling of plastics and composites, financing research projects in these areas. A project started in 2010 by European PVC producers, called Recovynil, aims to anticipate the collection and recycling of used PVC. In 2015, the “VinylPLus” program also started to support the recycling consortium “Resysta,” which produces a wood-like material, based on rice husks and PVC, in a homogeneous polymer matrix. The program allowed 183 tons of PVC to be recycled in the first year, and is now included in future VinylPlus statistics (PPE 2016). In the context of a German project (LIFE 00 ENV/D/000348), a pilot installation was built for the production of wood-plastic composite (WPC), using up to 100% recycled PP. Another Life project, coordinated by Denmark (LIFE 04 ENV/DK/000070), aims at the complete conversion of powder granules, from used tires, into high-­ quality rubber products, through the application of dense phase techniques. The recycled material is applicable to the flooring of sport fields, rubber materials, and asphalt. The consortium created a patent to protect this technology (Ignatyev 2014). The Spanish plastics association “AIMPLAS” started in 2019 the “Enzplast” project with the objective of developing more sustainable processes for the manufacture, recycling, and composting of plastics, which will develop the implementation of synthetic routes to obtain plastics in a safer and more ecological way, using enzymes instead of metal catalysts. AIMPLAS is also studying the use of enzymes in recycling, incorporating them in the washing phase to remove odors, as well as in the separation of multilayer materials. Finally, the evaluation of the effectiveness of different enzymes in the biodegradation process of different bioplastics is also part of the project. The Basajaun project, coordinated by Tecnalia Research and Innovation Foundation, is a EU Horizon 2020-funded 4-years project that addresses novel concepts in building materials, products, systems, and technology to improve the wood construction value chain. Profiles of WPC are pultruded from resins derived from forestry products and reinforced with natural fibers. The project aims to construct full-scale demo buildings in Finland and France that pull together the various parts of the project. The project also includes the development of thermal insulation products using foams made from renewable sources as well as wood-plastic composites (WPCs) and fire-resistant composites (PPE 2021b). The “Remadyl” project also aims to remove dangerous substances from old PVC, that is, from PVC added with dangerous substances, subject to regulatory restrictions, namely plasticizers based on low molecular weight phthalate (mainly DEHP) and stabilizers based on heavy metals (mainly lead). This “old PVC” constitutes most of the current post-consumer waste of rigid PVC (for example,

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window and pipe frames) and flexible PVC (for example, floor coverings or cables) of PVC. The presence of hazardous additives constitutes a barrier to recycling PVC, as there are currently no economically viable solutions for their removal. The “Remadyl” project aims to develop a continuous innovative one-step process, based on extractive extrusion technology in combination with new solvents and fusion filtration, which has the potential to rejuvenate “old PVC” and transform it into PVC of high purity, in accordance with REACH (Reach 2006), intended for the market of rigid and flexible PVC products, at competitive costs (Remadyl 2019). The EU-funded “Circular Flooring” project, started in June 2019, aims to recover PVC used in flexible, end-of-life PVC floor coverings that contain “banned plasticizers,” which can no longer be used due to issues consumer protection, and transform it into products with quality equivalent to virgin PVC. The latest generation recycling of this type of floor coverings is not yet possible, so these products are often incinerated, irreversibly destroying valuable resources. This project will meet the challenge of establishing the circularity of flexible PVC floor coverings with an innovative plastic recycling process. The process consists of recycling these coatings, by dissolving them in a selected solvent, in order to remove the critical substances, restricted plasticizers (phthalates), to obtain a high-quality virgin PVC material. The phthalates removed will be chemically transformed into non-­hazardous plasticizers. Both recycled PVC and processed plasticizer are once again incorporated into the production cycle of new coatings, respecting the principles of circular economy (Circular flooring 2019). The RENUVA™ Mattress Recycling Program, started by Dow Polyurethanes and partners, aims recycling polyurethane foam from end-of-life mattresses and turning it into RENUVA™ polyols for use in new mattresses and other applications. Dow Polyurethanes and Orrion Chemicals Orgaform together with Eco-mobilier, H&S Anlagentechnik and The Vita Group have inaugurated in 2021 a pioneering mattress recycling plant as part of the RENUVA™ program, with a full capacity to process up to 200,000 mattresses per year. Researchers at the Institute of Molecular Science (ICMOL) at the University of Valencia are developing radical scavenging additives to remove lead-based, PVC thermal stabilizers with old formulations. Researchers have already developed a laboratory-scale synthesis process to obtain a precursor material to support the lead scavenger, based on so-called double-layer hydroxides (LDHs). This precursor material comprises layers of divalent and trivalent metal cations (for example, Mg2 + , Zn2 +, or Al3 +), with an interlayer space that can be occupied by anions of different sizes (PPE 2020). Recently, these researchers optimized a synthesis, on a semi-pilot scale, needed to obtain the LDH precursor material on a larger scale, and are now able to produce lots of ZnAl LDH using equipment on an industrial scale. Using LDH scavenging complexes, in combination with specific filtration methods, the Spanish plastics association “AIMPLAS” is testing several formulations of rigid PVC, including a type of lead-free virgin PVC and micronized end-of-life PVC samples, both supplied by the German company “Deceuninck” (PPE 2020). The objective is to test various mesh and filter configurations, as well as different extrusion parameters, to determine the most suitable removal methodology. The

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selection of the filter takes into account the size of the inorganic particles in PVC formulations, such as calcium carbonate and titanium dioxide, often used in white products of rigid PVC, constituents of white-colored window profiles (which is more durable and consequently more used). In the first filtration test, using a screw extruder, it was possible to filter large mineral loads from PVC, including pre-mixed HDL (without the sequestering complex). However, a rapid saturation of the filter occurred. Subsequently, the results of the optimization tests showed that the filling materials, consisting of granules, of large dimension can be filtered, without breaking the filter, allowing to increase the extraction process yield. Other tests were also carried out with a counter-rotating twin-screw extruder, using a special device to prevent the saturation of the filter, further increasing the scale and the efficiency of the process (PPE 2020). The University of Birmingham and the engineering consultancy firm Stopford, in the UK, received funding to develop a laboratory-scale prototype to test a plastic recycling process using supercritical water2 (as a green solvent), which is supposed to indiscriminately dissolve and decompose mixtures of non-recyclable plastic waste, transforming mixed plastic streams into a chemical raw material that can be reused in the manufacture of plastics (Reinforced Plastics 2022).

 Supercritical water is water that is above the critical point of 374.5 °C and 220 bars.

2

Chapter 8

Final Remarks

8.1 Conclusions Recycling is a key resource to minimize waste and reduce environmental pollution, and is a strategic approach to the management of waste from plastic construction products at the end of its useful life. Recycling helps to conserve natural resources and is progressively more important, both from an economic and an environmental perspective. The most recent results demonstrate a substantial increase in the rate of recovery and recycling of plastic construction materials. Through the recycling of plastic waste it is possible to produce new materials, concluding that this process can reduce environmental pollution and contribute to the generation of jobs and by making more human resources available. In addition to recycling, the development of bioproducts from biomaterials and natural fibers has become relevant for a significant number of industries and for a series of applications, increasingly in construction. Although the applications of biocomposites, with the objective of reducing the energy incorporated in construction materials, are already numerous, either in applications with lower performance requirements or in combination with other materials of greater resistance, these materials are not yet widely used due to their susceptibility to degradation induced by the action of humidity, and because they still do not present a fire behavior as good as conventional construction materials, therefore requiring future developments. What was mentioned throughout this work and the information in the specialty bibliography allow us to draw the following conclusions: –– The plastics recycling market in Europe and the World is relatively robust and the interest in plastics recycling is growing, and it will be greater the lower the price of recycled plastic and the more additional benefits there are. –– The quantities of recycled PVC (which is the most used plastic in construction) continue to grow year after year, which shows that both PVC recyclers and man© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 L. E. P. Real, Recycled Materials for Construction Applications, https://doi.org/10.1007/978-3-031-14872-9_8

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ufacturers of finished products that use recycled PVC, especially in the recycling sector, pipes, and profiles are making progress and showing good results, as they have already recycled 4.2 million tons of PVC since 2000, and this recycling capacity has increased continuously over the years. In fact, every year, the European PVC industry approaches the future target set for recycling PVC, namely 800,000 tonnes in 2020, 900,000 tonnes in 2025, and 1 million tonnes per year between 2025 and 2030 (PRW 2018). The interest in recycled plastics is also a consequence of regulations and waste management policies. Part of the recycled plastic market has been stimulated by legislative acts that set objectives (Directives), such as producer responsibilities, recycling targets, and taxes associated with incineration. National practices and regulations therefore determine the quantity and quality obtained in a given country. However, until now, recycling targets have been specified only for the quantity to be recycled, and not for the quality of the recycled material. The price of crude oil, but also the demand for plastic in the global market (mainly from China), are decisive for formulating the price of recycled plastic. The purity of the recycle also determines the price and the application of the recycle. The market demand is higher in relation to pure recycled products, such as industrial reprocessed, which are part of current plastic manufacturing practices and/or work as a diluting material in the production of virgin plastics; The recycling of plastic waste faces challenges related to the costs of collection and sorting, and the quality of the waste collected. Exporting to Asia has long been the most viable solution for the least valuable plastic waste fractions. The lack of capacity to treat mixed plastic waste and the high costs associated with reprocessing are some of the causes of low demand in national markets (Plastic Zero 2013a). Although the market may benefit from the existence of standardization and common certifications, the prevailing practice has been based on less formal bilateral agreements, as they allow for more exact specifications based on less exhaustive documentation (Plastic Zero 2013a). The quality of the waste plastic received at the sorting facilities is a key factor, especially for mixed plastic waste streams. The efficient separation of plastic waste at the source is crucial, but it is not always easily accomplished, as it requires experience and knowledge about local conditions to motivate people to separate the desired source. The guarantee of a stable supply of recycled plastics, with characteristics that have the least variation possible, is fundamental for manufacturers of finished products, aiming at applications in certain sectors. The classification and recycling technologies are already well developed for some types of plastic waste, but there is still a great potential for the development of recycling technologies and recycled plastic applications in a wide variety of plastic products.

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8.2 Challenges The trend toward a continued increase in recycling should be maintained. However, there are still some significant challenges, both in terms of technological factors and in relation to issues of economic or social behavior, related to the collection of construction materials in recyclable plastic and the replacement of virgin plastic construction products by recycled ones. The recovery of materials and products should not only be considered at the end of life, but also at the design level. The choice of materials for the production process (in terms of ease of classification at the end of its useful life) and the design of the product in terms of final disassembly (for example, avoiding embedded metal fastenings that are difficult to separate before grinding) should be two key characteristics to consider in the future, not least because the design of recyclable products can stimulate investment in collection, separation, and recycling infrastructures, even in countries where this infrastructure is still non-existent. The inevitable problem of downcycling of materials will continue to demand new technological solutions and continuous developments. The development of mixing techniques for mechanical recycling of plastics, in the presence of suitable compatibilizers, is a fundamental feature to increase recycling in the future and the growth of the market for materials that can make compatible mixed resin flows. Innovative solutions are needed for plastic waste from sorting processes, as well as for new types of plastics and composite materials, which are currently not recyclable. The recycling of these materials constitutes a new market opportunity for plastics manufacturers and the recycling industry in Europe. Research and development in the recycled composites business can be motivated by the establishment of recycling targets, both quantitative and qualitative, in the waste management sector. Integrating recycling know-how in the plastics value chain can benefit the industry, the environment, and society ecologically and economically. Other important aspects, which are expected to develop, are the measurement of the composition of the polymer directly on the recycling machine and the continuous monitoring of quality during the recycling process. It is increasingly important to determine the composition of recycled materials, the nature of the plastics, the purity of the material (especially with regard to the presence of heavy metals), and its molecular weight. It is also important to identify previously recycled plastics and in what percentage. To respond to these challenges, there have been new developments in the field of identification and analysis of commonly recycled plastics, even using existing techniques, namely nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), initial production verification (ICP).) and X-ray fluorescence (XRF). Future developments in the detection of contamination in recycling streams, using optical systems and X-ray technology, also constitute a promising field. Digitization opens new opportunities for the planning, control, and organization of industrial recycling processes, through a high degree of automation and access to

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assistance systems and information tools, on platforms developed online. The digital network is an important step on the way to integrate recycling know-how in the plastics value chain. The potential application of biobased and biodegradable plastics and composites in the area of civil ​​ construction requires the development of high-performance construction products, which require action in several directions. Among these, the treatment and modification of the fiber surface and the structural design technologies stand out, as they are the ones that allow to act more efficiently on the fibermatrix interfacial bond, an aspect of the greatest importance to increase the durability and performance of these materials. The manufacture of piping based on bioplastics is a major challenge in the future, not only to reduce the energy of incorporated, but also, and mainly, to reduce the CO2 emission. Other innovations that would help to improve the environment and create greener plastics, would be to give biodegradability to traditional plastics, in products of low durability, for example, adding substances that attract microbes, causing the final product to degrade more quickly in landfills, or remove harmful gases from the air (carbon dioxide and carbon monoxide), using them to manufacture biodegradable plastic products.

8.3 Recommendations The European Parliament's report on the EU debate on plastics held in 2018 allowed to develop a European strategy for plastics in the circular economy (Resolution 2035 2018), (EC 2019), recognizing that, although plastic plays a useful role in our economy and in our daily lives, it has, at the same time, significant adverse effects. Thus, it considers that the main challenge is the sustainable management of plastics throughout the value chain and the consequent change in the way we produce and use plastics, in order to preserve the value of our economy, without harming the environment, the climate, and public health; In this strategy, it is proposed to promote the development of joint and coordinated actions, involving all stakeholders, throughout the value chain, including consumers and government agencies, to guarantee the success of recycling and encourage the circular economy, aiming to achieve an advantageous result for the economy, the environment, the climate, and health. In addition to the EU, several associations of manufacturers and environmental organizations have also recommended the implementation of strategic actions aimed at solving the environmental problems resulting from the use of plastics. New initiatives will be needed to develop the market and increase the recycling and recyclability of plastic waste, since it seems unlikely that plastic recycling will continuously increase solely driven by market demand, as this depends fundamentally on the cost of recycled materials and their quality (which is not always good enough for certain applications).

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The most relevant strategic measures, indicated in scattered sources, can be classified at various levels, as summarized below: 1. Economic incentives: –– –– –– –– –– –– –– –– ––

Stimulate continuous investment in innovation for recycling technologies Increase investment in recycling infrastructure Encourage and support the plastics recycling industry and foster job creation Promote the use of recycled plastics as a substitute for virgin plastic Promote and reward pioneering innovation in the use, production, and reuse of plastics Increase sustainable markets for plastic waste Create favorable financing conditions for the construction of green buildings Reduce VAT for products containing recycled materials Create deposit-refund and pay-as-you-throw schemes

2. Management: –– Improve the interaction between recycling companies (collection, separation, and transformation) –– Improve logistical management, such as collection schemes –– Develop and implement strategies for the systematic application of ecological interventions throughout the construction supply chain –– Implement programs that allow to track the quantity and types of plastic materials used in construction, sent for recycling, as well as the quantity of recycled plastics used in new products applied in construction works. 3. Regulation and legislation: –– Implement consistent and complementary regulations on recycling –– Discourage incineration and landfill (for example, through the application of taxes) –– Encourage manufacturers to increase recycling volumes for their new products –– Encourage the development of responsible bioplastic technology and the consequent adjustment of the infrastructure necessary for its degradation and composting –– Complement the quantitative recycling targets with qualitative targets, in order to achieve a quality of the recycled material that can replace virgin plastic and, thus, avoid recycling in plastic descending cycle –– Establish differentiated goals for various types/plastic products, in order to consider their diversity. Such targets could assist local authorities in defining the residual plastic fractions to be collected and in the respective treatment methods –– Expand obligations in producer responsibility programs, with instruments that motivate producers to use recycled plastic in their products and/or increase the recyclability of products

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–– Differentiate rates in collective producer responsibility programs, according to the recyclability of products, for example, by imposing higher rates on virgin materials or products containing various materials, in order to motivate manufacturers to rethink the product design, using, for example, recycled/ recyclable materials and facilitating the disassembly of the product –– Set goals for low carbon manufacturing and the generation of green jobs –– Improve transport procedures and implement cross-border shipping regulations; involve the plastic industry sector in initiatives to promote sustainable growth and initiatives around the circular economy –– Increase the implementation of life cycle analyses for strategic planning and estimation of technological processes –– Continue to implement regulations to reduce the dumping of plastics at sea –– Limit the manufacture and consumption of plastic products with a short shelf life –– Increase ecological construction policies –– Support the development of life cycle-based indicators that may be needed to facilitate the measurement of resource efficiency and performance in the construction sector 4. Standardization and certification: –– Develop appropriate standards for the classification of waste, since the reliability of supply is critical to product development –– Develop testing and certification techniques for new products 5. Research and technological development: –– Boost innovation for a more circular plastics life cycle by reducing the amount of primary plastics needed, prolonging the useful life of products, and facilitating recycling –– Encourage research and technological development in the area of recycling of plastic mixtures, in order to find clear scientific and economic solutions to effectively use the recycled composite material in new or existing applications –– Encourage research aiming the reduction of contamination in recycled products –– Intensify the research on more versatile waste composition monitoring and/or sorting solutions, combining different automated photonic techniques and advanced data treatment –– Improve novel recycling methods such as selective polymer dissolution for multi-layered films or composites without preliminary separation of pure fractions –– Develop composite recycling processes and find ways to effectively use the recycled composite material in new or existing applications –– Create more solutions for the efficient collection and reuse of polymeric waste from the oceans –– Develop stabilizing additives, like antioxidants and photochemical stabilizers, aiming to preserve the length of the reused polymers chain and, consequently, the original level of performance

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–– Develop more high-performance biobased and biodegradable construction products –– Evaluate the performance of composite materials in case of fire and specify the best solutions to protect structural composite materials from fire, without harming the environment –– Develop life cycle analyses to assess and optimize recycling conditions for different types of composites –– Compile life cycle data and environmental product declaration data for selected building plastics and composite materials 6. Industrial production: –– Implement design improvements in plastic products to facilitate recycling (design for disassembly) –– Create products made from recycled WEEE plastics –– Contribute to facilitate the identification and separation of hybrid products during the recycling process –– Design fully biodegradable polymers that can replace some non-­biodegradable polymers currently in use –– Design new catalysts, active and selective, for oxidation reactions in thermochemical recycling, in order to avoid the formation of harmful toxic gases –– Optimize production technologies through the development of practical systems for large-scale processing of biocomposites, such as pultrusion and continuous or semi-continuous processes, for molding and compression lamination of panels, plates, flat and laminated profiles (sandwich structures) with more complex geometric shapes, used for cladding facades –– Supervise the use of energy and emissions during the processing of plastics and composites, in order to also minimize the environmental impact and the energy incorporated in the products –– Optimize industrialization, through more automated techniques and through the introduction of nanotechnologies, to have access to the market for structural composite applications 7. Training and dissemination: –– Discourage waste and abandonment of plastics through public awareness campaigns on the value of plastic products –– Enhance sorting at source –– Regularly adjust how citizens and businesses should manage plastic waste, by providing information on an ongoing basis –– Maintain and increase public support for recycling, to achieve the recycling targets established –– Promote training and training actions, providing workers with knowledge of handling on site

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Index

A Additives, 4, 19–33, 35, 45, 62, 69, 70, 79, 81, 88, 91, 92, 95, 98, 99, 117, 118, 121–125, 129, 130, 137, 139, 143, 150 Applications, 2, 19, 35, 48, 104, 115, 119, 145 B Biobased plastics, 4, 10, 12, 23, 24, 27, 104 Biobased polymers production, 28, 104 Biocomposites, 23, 29–31, 41–44, 145, 151 Biodegradable plastics, 23–29, 33, 44, 48, 104, 148 Bioplastics, 12, 23–29, 33, 77, 96, 104, 106, 123, 142, 148, 149 C Carbon footprint, 1–3, 10, 12, 13, 22 Challenges, 3, 19, 88, 129, 143, 146–148 Chemical recycling, 16, 27, 47, 48, 94–96, 101, 123, 127, 128, 133, 140, 141, 151 Circular economy, 3–5, 9, 11, 16, 23, 26, 31, 45, 47, 89, 93, 95, 120–122, 124, 142, 143, 148, 150 Closed circuit, 96–97 Composites, 4, 26, 35, 58, 118, 120, 147 Construction, 3, 19, 35, 58, 104, 115, 119, 145

D Decarbonization, 4, 27, 31 Downcycling, 49, 96, 97, 147 E Elastomers, 19, 21, 127 Environmental impact, 2, 4–6, 8, 10–16, 24, 30, 41, 47, 99, 117, 133, 138, 151 Environmental issues, 29, 47, 132 F Fiber-reinforced plastics (FRP), 13, 14, 36–40, 81, 82, 130–134, 141 Future developments, 44, 116, 145, 147 G Greenhouse gas (GHG) emissions, 2–4, 7–12, 24, 27, 31 H Hybrid materials, 118, 129 I Impurities, 31, 32, 49, 59, 70, 72, 92, 93, 97, 101, 112, 115, 116

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 L. E. P. Real, Recycled Materials for Construction Applications, https://doi.org/10.1007/978-3-031-14872-9

161

162 L Legislation, 16, 21, 107, 115, 149 Life cycle analysis (LCA), 5–7, 12–16, 26, 93, 150, 151 M Machinery, 29, 49–56, 103, 131 Market data, 103–113 Mechanical recycling, 15, 16, 25, 27, 47, 94–100, 123, 127, 132, 133, 147 Mitigation measures, 123, 126, 130, 132 Mixed plastic streams, 53, 77, 112, 115, 116, 144 O Optical separation, 65, 74–82, 116 P Plastic mixtures, 71, 84, 130 Plastic mixtures recycling processes, 129–130, 140, 150 Plastic recycling technologies, 140 Plastics, 1, 19, 35, 47, 103, 115, 119, 145 production, 2, 12, 24, 92, 104–106 waste, 1, 2, 16, 27, 33, 36, 39, 48, 49, 61, 64, 69, 77, 81, 85, 87–89, 92–96, 98–101, 106–111, 115, 118, 123, 138, 140, 144–149, 151 Pollution, 1–2, 4, 6, 16, 23, 26, 29, 31, 85, 145 Polyethylene (PE), 12, 20, 32, 35, 45, 53, 66, 69, 77, 85, 90, 95, 104, 110, 129, 130, 139, 141 Polypropylene (PP), 12, 14, 20, 32, 35, 43–45, 50, 64, 69, 75, 77, 85, 87, 90, 92, 93, 95, 107, 110, 129, 139, 141, 142 Polyurethane (PU), 21, 35, 95, 126–128, 138–139, 143 Polyvinyl chloride (PVC), 10, 20, 35, 64, 110, 119, 145 Programs, 3, 25, 89, 121, 122, 124, 125, 142–144, 149, 150 Projects, 3, 10, 13, 14, 86, 121, 124, 132, 135, 136, 138, 139, 142–144

Index Q Quality, 3, 4, 7, 13, 14, 19, 20, 25, 27, 31, 44, 48–51, 55, 56, 62, 67, 70–71, 80, 87–94, 96, 97, 101, 107, 109, 110, 112, 115–117, 120, 121, 123, 124, 136, 138, 140, 143, 146–149 Quality assessment, 89–91 R Recommendations, 9–11, 90, 122, 148–151 Recyclates, 12, 60, 62, 89, 90, 94, 96 Recycled plastics, 4, 5, 15, 16, 23, 31–33, 40, 44–45, 48, 56, 62, 87–90, 93–96, 98, 100, 106–109, 115–118, 134, 137, 138, 140, 146, 147, 149 constraints, 115–118 price, 110–112, 145, 146 Recycling, 2, 20, 35, 47, 103, 116, 119, 145 constraints, 117, 126, 131 cost, 69, 73, 109–110, 117, 146, 148 influencing factors, 88 market, 103–113, 140, 145 statistics, 103–113, 124–125, 128 success stories, 120, 135–141, 148 Regulations, 16–17, 45, 48, 112, 122, 146, 149, 150 Research studies, 15, 141 S Separation methods, 60, 70, 85 Statistics, 103–113, 124–125, 128, 142 Sustainability, 2–4, 7, 11, 16, 17, 22, 23, 26, 31, 35, 47, 89, 115, 124, 125, 132, 136, 138 T Thermoplastics, 19, 20, 36, 44, 69, 76, 90, 99, 104, 107, 131, 140 Thermosets, 19–21, 36, 44 W Waste management, 1–3, 25, 33, 49, 86, 113, 122, 146, 147