22 Over the coming decades, a large additional mass of plastic waste will become available for 23 recycling , as the world’s largest fast moving consumer goods companies step up efforts to 24 reduce plastic pollution and facilitate a circular economy. Finding ways to recover value from 25 this mater ial is a substantial challenge that has prompted exploration of novel processes , such as 26 ‘chemical recycling’, as well as more established ones, such as incineration with energy 27 recovery . Many of these efforts will take plac e in the Global South, where plastic pollution and 28 due to mismanagement of waste are most acute. New infrastructure will need to be developed, 29 and it is important that the processes and systems chosen do not result in adverse effects on 30 human health and th e environment. This concern is particularly acute in countries that lack 31 effective, well -resourced and independent systems for environmental regulation and the 32 protection of occupational and public health. Here, we present a rapid review and critical semi- 33 quantitative assessment of the potential risks posed by eight approaches to recovering value 34 (resource recovery , circular economy ) from post-consumer plastic packaging waste that has 35 been collected and separated with the purported intention of recycling. The focus is on the 36 Global South, where there are more chances that high risk processes could be run below 37 standards of safe operation (though much of the evidence reviewed is inevitably based on 38 research outcomes obtained in the Global North context) . Our assessment indicates that under 39 realistic, i.e. non -idealised operational conditions, mechanical reprocessing is the least impactful 40 on the environment and is the most appropriate and effective method for imp lementation in the 41 Global South. We find l ittle difference in potential risks between so called ‘bottle -to-fibre’ and 42 ‘bottle -to-bottle’ processes as they involve similar processing and both result in substantial 43 avoided burdens from virgin production. The lack of real -world process data for the g roups of 44 processes known as ‘chemical recycling’ make them hard to assess. A t present , there is no 45 strong evidence that any of them have reached commercial stability when applied to processing 46 post-consumer plastic packaging waste. Given this lack of matur ity and potential for risk to 47 human health and the environment (inferred through the handling of potentially hazardous 48 substances under pressure and heat) , it is hard to see how they will make a useful addition to the 49 circular economy in the Global South in the near future . Incineration of waste plastics that have 50 been collected for recycling is comparable with other forms of fossil fuel combustion used to 51 generate energy and , despite the lack of process data , the same is likely for co -processing in 52 cement kilns : notably, neither of these processes can be described as ‘recycling ’ and, in general, 53 are deemed as only the last resort in circular cascading systems . Though contemporary air 54 pollution control technology is capable of comprehensively mitigating harm ful emissions from 55 combustion, there is a high risk that costly maintenance and management will not be carried out 56 in the absence of strong regulation and enforcement. Inevitably, increasing circular economy 57 activity will require expansion towards targetin g flexible, multi -material and multi -layer 58 products, for which mechanical recycling h as well -established limitations; which has prompted 59 exploration of alternative approaches. Yet , our comparative risk overview indicates major 60 barriers to changing resource recovery mode from the already dominant mechanical recycling 61 mode towards other nascent or energetic recovery approaches. 62 1 Introduction 63 In recent years, s everal voluntary commitments have been made by fast moving consumer 64 goods (FMCG) companies in an effort to enable more post-consumer plastic packaging waste to 65 be collected and recycled . For instance s ignatories to the Plastic Pact (Ellen MacArthur 66 Foundation, 2017) have pledged to include post -consumer recycled plastic in plastic pack aging 67 they place on the market by 2025 . It is anticipated that these initiatives will reduce the amount 68 of plastic waste that is mismanaged by being dumped on land, into water or through burning i n 69 open uncontrolled fires , thereby preventing plastic pollution (Lau et al., 2020) . 70 If these circular economy commitments are successful, a large mass of additional material wi ll 71 need to be processed and converted into new raw materials or energy worldwide (Ellen 72 MacArthur Foundation et al., 2020) . Efforts such as Lau et al. (2020) have proposed high level 73 solutions that focus on reduction, material substitution, collecting, processing or disposing of 74 this large mass of material, but as yet there are no comprehensive efforts to assess their safety 75 when implemented at global scale. 76 In the absence of such consolidated evidence , FMCG companies have been investigating 77 existing ‘approaches ’ to recovering value (materials or energy ) from plastic packaging . Some of 78 these resource recovery approaches include those that recover the material whilst preserving its 79 physical and chemical structure and integrity such as: A1) Conventional mechanical 80 repro cessing for extrusion; A2) Bottle -to-fibre mechanical reprocessing for extrusion; A3) 81 Mineral -polymer composites: road surfacing & brick & tile production ; and A4) Solvent based 82 purification. Other approaches involve decomposition of chemical structures in plastics to create 83 new chemicals that have the potential to be synthesised into starting materials for new plastics 84 production such as: A5) Chemical de -polymerisation (Chemolysis); and A6) Pyrolysis or 85 gasification. 86 Other approaches explored by FMCG companies are typically referred to as ‘recovery’ and are 87 not considered ‘ recycling ’ according to globally applied terminology ( Table S8 ) such as: A7) 88 Co-processing in cement kilns; and A8) Incineration (combustion) with e nergy recovery (often 89 described as ‘energy -from -waste’ – EfW – but hereafter ‘incineration’) . These technologies 90 have been used to process material that has been collected from the mixed municipal waste 91 stream but due to the composition of the plastics and /or lack of available markets, are unsuitable 92 for mechanical reprocessing. 93 Many of these approaches are, or are planned to be implemented in Global South where the 94 majority of the world ’s plastic packaging is mismanaged (Cook et al., 2020a) . However , some 95 of these countries lack well-resourced, independent environmental and safety regulators, and 96 there are concerns that emi ssions from some processes may result in harm to human health and 97 the environment (Nguyen et al., 2021; Rollinson et al., 2019; UNEP et al., 2020) . 98 Several efforts have been made to compare the relative safety of potential approaches to 99 managing post -consumer plastic packaging that has been collected for recycling. For instance, a 100 working group of parties to the Basel Convention on the Contro l of Transboundary Movement 101 of Hazardous Wastes and Their Disposal (hereafter , the Basel Convention) has drafted guidance 102 that begins to describe the safe treatment of plastic waste (UNEP et al., 2020) . The purpose is to 103 support Decision BC -14/13 of the Conventio n that compels parties to ensure exported waste 104 plastic wastes undergo ‘environmentally sound management’ in the country of destination. 105 Other comparisons of approaches to recovering value f rom post-consumer plastic packaging 106 waste that has been collected for recycling focus on certain aspects of environmental harm or 107 human safety. Lazarevic et al. (2010) reviewed studies that compared the life cycle impacts of 108 managing plastic waste using mechanical reprocessing , feedstock recycling, incineration and 109 landfill. The study did not assess the impact on human health , but found that mechanical 110 reprocessing was t he least impactful on the environment. More general , reviews exist such as 111 Crippa et al. (2019) and Ragaert et al. (2017) , who provide descriptions and process informat ion 112 that explain the potential pathways for processing plastic wastes. In each case, the focus is on 113 the circular economy ; however , only summary evidence is provided that relates to the potential 114 environmental and public health risks from the various proce sses. 115 There are many other s ources that address the public, occupational and environmental safety of 116 approaches to recovering value from plastic waste, however as yet, there is no review that 117 compares the approaches or assesses their suitability for imple mentation o r continued existence 118 in the Global South. For clarification, t he term ‘Global South’ is used here for convenience but 119 really alludes to countries where the lack of effective, independent, well -resourced enforcement 120 and regulation might result in an elevated risk to human health and the environment. 121 Here, we rapid ly review such evidence for eight types of resource recovery approach, each of 122 which is presented in their own section (Table 1). Evidence is summarised i n sub -sections for 123 1) Overview – prevalence and commercial maturity; 2) Risks to the environment , particularly 124 global warming; and 3) Risks to occupational and public hea lth. In Section 11, we compare the 125 approaches and qualitatively assign scores to indicate the comparative risk to human health and 126 the environment when implemented in the Global South. 127 Table 1: Engineering a pproaches to recovering value (resource recovery) from post-consumer plastic 128 packaging that has been collected for recycling . 129 Approach number Approach name Description A1 Conventional mechanical reprocessing for extrusion (Section 3) Plastic wastes are sorted, purified, comminuted and re -melted (extruded) into pellets for conversion (Shen et al., 2014) A2 Bottle -to-fibre mechanical reprocessing for extrusion (Section 4) Polyethylene terephthalate ( PET) waste is sorted, purified, comminuted and re - melted (extruded) into pol yester fibre for use in textile production (Shen et al., 2011) A3 (a & b) Mineral -polymer composites: road surfacing (A3a) & brick & tile production (A3b) (Section 5) Plastics wastes are melted alongside minerals such as sand or aggregate, acting as a binding and strengthening agent when cooled (Kumi -Larbi et al., 2018; Zhu et al., 2014) A4 Solvent based purification (Section 6) Solvents are used to dissolve specific polymers in plastics , enabling them to be separated from additives and residues (Ügdül er et al., 2020) A5 Chemical de -polymerisation (Chemolysis) (Section 7) Plastics are reacted under heat and pressure alongside catalysts to depolymerise them and enable the resultant monomers and oligomers to be used in primary plastics production (Raheem et al., 2019) A6 Pyrolysis or gasification (Section 8) Plastics are heated, without (pyrolysis) or with limited (gasification) oxygen, resul ting in polymer chain scission and reformation of hydrocarbons as gases solid or liquid that can be used as fuels or as feedstock for repolymerisation (plastic production) (Lopez et al., 2017; Ragaert et al., 2017) A7 Co-processing in cement kilns (Section 9) Waste is used as a replacement fuel for coal in cement production plants (also often termed: waste -derived fuel, solid -recovered fuel – in which case it is often applied to material derived from mixed waste rather than that which has been collected for recycling ) (Velis et al., 2012) A8 Incineration with energy recovery (Section 10) Waste is combusted whilst heat is recovered to heat space and water whilst electricity is generated (Neuwahl et al., 2019) For clarification, this review is concerned with the eight engineer ing approa ches to resource 130 recovery as they are applied to treating post -consumer single use plastic packaging that has been 131 collected for recycling. This means that post -industrial (pre -consumer) material is excluded as 132 well as mixed wastes, for instance those that have been collected from households. The 133 approaches included are those that have been utilised by or considered for utilisation by FMCG 134 companies. This means that some approaches that are more nascent, and at bench scale of very 135 low technological readiness (U.S. Department of Energy, 2011) , such as enzymatic conversion 136 (Tournier et al., 2020) or hydrothermal carbonisation (Shen, 2020) . Other parts of the waste 137 system are also excluded from this review, such as waste collection systems (formal and 138 informal), reuse, minimisation and material substit ution. 139 2 Methods 140 2.1 Literature review 141 Literature was obtained by searching peer-reviewed content in the arch ival database Scopus, 142 Google Scholar (e.g. non-governmental organisation and industry led reports) and generic 143 internet content via Google. A rapid search was carried out of existing re views of each of the 144 approaches ( Table 1). However, d rawing on evidence only from the reviews w ould have 145 introduced bias to the study and an over -reliance on the robustness of a third party’s 146 investigation. To establish a r eliability pedigree, and inform inclusion/exclusion, samples of 147 articles cited in each review were checked to ensure that the findings of original works had been 148 correctly and fairly represented. If there was an indication that this was not the case, furth er 149 samples were taken and if necessary the review was rejected for inclusion. Other considerations 150 included the number of times a review had been cited by others in the context of the publication 151 date, whether a report was funded by a particular narrow gro up of stakeholders and the quality 152 and thoroughness of interpretation of data by the author of the review . 153 Citation / snowball search methods (Cooper et al., 2018) were used to identify more recent 154 studies carried out since reviews had been conducted. In some cases, no relevant reviews e xist, 155 for instance for plastic packaging co -processed in cement kilns, therefore relevant individual 156 papers were identified assessed . 157 2.2 Visual assessment of online media 158 As there is hardly any relevant process data (for example: process system inputs, outputs, 159 throughput, energy use, emissions, workforce behaviour, safe systems of work) for many of the 160 topics covered in this review, an assessment of online multimedia (video) sources was carried 161 out to identify risks to occupational health and safety from mechanical reprocessing and mineral 162 polymer composite slab and tile production . Observations of multimedia content have emerged 163 in the last decade following the rising popularity of video sharing platforms such as YouTube 164 (Kousha et al., 2012) . We developed a novel rapid method for assessing occupational health and 165 safety based on an observational study of safe systems of work employed by firefighters (Kahn 166 et al., 2014) and one of recreational jumping from height into water (Moran, 2014) . 167 Searches were carried out in the YouTube repository, which is the most widely used repository 168 with the widest scope using a variety of terms including ‘plastic recycling’ and ‘plastic and sand 169 tile production’. National terms were added to the search operators such as ‘India’, ‘China’ and 170 ‘Brazil’. The purpose of this part of the study was to obtain an indication of good or poor 171 practice ; working conditions; engineering controls to manage occupational and public risk; and 172 identify potential extremes of occupational safety behaviour. We did not attempt to determine 173 the p revalence of these practices , because the method feasible was not deemed as suitable. To 174 control for bias, we chose to exclude footage intended to indicate bad practice as there was a 175 risk that fill makers had cherry picked poor behaviour. Instead, footage that was intended to 176 demonstrate or ‘showcase’ a process or existing operation was assessed. 177 For each video, b asic information was recorded (Table 4) and the main hazards were identified 178 using Hughes et al. (2016) and consolidated in to the following list: 179 1. Unguarded fast or high torque machinery in close proximity to work ers; 180 2. Worker interaction with machinery resulting in risk of being drawn in ; 181 3. High temperature equipment in close proximity to workers risking burns ; 182 4. Risk of interaction with unknown potentially hazardous materials or substances (i.e. 183 through atmosphere, dermal contact or ingestion) ; 184 5. Risk of burns from caustic substance ; 185 6. Particle loss to the environment likely ; 186 7. Risk of aerosolised hazardous substance ; and, 187 8. Risk of ballistic injury to hands, feet, body from interaction with sharp or heavy objects . 188 2.3 Inclusi on/exclusion criteria 189 Technical l iterature and other sources of information identified were assessed for inclusion in 190 this study according to the criteria listed in Table 2. 191 Table 2: Inclusion and exclusion criteria. 192 Inclusion Exclusion  Conventional plastics  Waste collection – e.g. waste pickers  Technologies listed  Biodegradable plastics  Supply systems  International trade in plastic scrap  Post-consumer plastic waste  Post-industrial waste  Packaging  Non—packaging  Peer reviewed journal articles, conference papers, books, reports, websites, online multi -media  Reuse / alternative delivery systems  Film footage intended to expose poor practice 193 2.4 Assessment criteria for approaches 194 2.4.1 Commercial and technological maturity 195 The commercial and technological maturity of each approach alongside its commercial 196 prevalence provide valuable insights into the level of risk of safe operation. Whereas well 197 established processes benefit from many years or even decades of experience, the re may be an 198 increased risk of harm to human health and the environment from more nascent approaches due 199 to hazards that were not expected or sufficiently mitigated. The technological readiness level 200 (TRL) scale (U.S. Department of Energy, 2011) is commonly used to indicate how far a 201 technology has progressed towards commercialisation. However onc e an innovation has reached 202 Level 9, the scale does not indicate whether the technology is commercially sustainable in the 203 real world, only that it is stable and functional at a large enough scale to be commercialised. 204 Though our objective differs from a proposal by Bruno et al. (2020) that ext ends the TRL scale 205 to consider legal, organisational and societal readiness, we have used this as a basis to create our 206 own four level scale for low -high maturity ( Table S1). 207 2.4.2 Risk of harm to the environment and human health 208 The risk of harm to the environ ment and human health were described and summarised in Table 209 S6. As the majority of robust data exist only for the Global North context, these were assessed 210 first. Scores for the Global South were then adapted from the Global North using objective 211 reasonin g to infer likely conditions, and controls to protect human health and the environment. 212 The descriptions in Table S6 were then ranked using criteria adapted from Velis et al. (2021) 213 according to four levels: low risk; medium -low risk; medium -high risk; and high risk. Where 214 the evidence was insufficient to make an assessment, no score was given. 215 2.4.3 Risk of operating below standards (appropriateness) 216 Each approach was scored for its appropriateness for safe operation in the Global South using 217 the matrix in Table 3. The score is chosen at the intersect of the lowest of the two scores for 218 either environmental or human health risks on the x -axis and the maturity on the y -axis. 219 Table 3: Matrix for assessing risk of operating below standards in the Global South (appropriateness) . 220 Risk to either environment or human health in the Global South (whichever is greatest) L ML MH H ID Commercial and technological maturity H L ML MH H MH ML ML H H ML ML MH H H H L ML MH H H H ID ML MH H H H Risk of operating below environmental and health standards in the Global South (appropriateness): L = 221 appropriate/low risk of operating below standards; ML = appropriate but with some risk of operating below 222 standards; MH = inappropriate but could be implemented if operating standards sufficient; H = inappropriate/high 223 risk of operating below standards. ID = insufficient data to make an assessment. 224 2.4.4 Grouping of approaches 225 Each of the eight app roaches and sub -approaches were arranged into groups according to the 226 characteristics: maturity ; risks to human health and envir onment ; and of operating below 227 environmental and health protection standards in the Global South (appropriateness) . Three 228 groups emerged ( G1-G3), one of which was divided into G1a and G1b due to slightly differing 229 levels of evidence and maturity. Approach 6 was divided into two sub -groups during this 230 process, to demarcate between pyrolysis and gasification used for feedstock and fuel; the former 231 of which is immature and the latter of which is mature but with questionable environmental 232 benefit when applied to post -consumer waste plastic packaging. 233 3 Approach 1: Conventional mechanical reprocessing 234 for extrusion 235 3.1 Overview 236 In the Global South, mechanical reprocessing of plastics has been carried out since the 1980s 237 (Lardinois et al., 1995; Wahab et al., 2007) , long before many high-income countries developed 238 commercial reprocessing capacity. Despite these several decades of activity, very little 239 published data exist on how these processes are carried out in the Global South context, which 240 makes it challenging to assess the risk to human health and the environment. 241 In the Global North, plastics reprocessor operations are reasonably well documented, though 242 commercial confidentiality may sometimes obscure the latest developments. In this setting , 243 manual sorting is slowly being replaced as sensor -based separation technology increases in 244 accuracy and many modern plants have reported to reduce their material loss es substantially as 245 their processes and learning mature. 246 Mechanical reprocessing of post-consumer waste plastics involves several steps aimed at 247 purifying and standardising polymers and their additives to make them suitable for remelting 248 and forming into n ew products (Schyns et al., 2020) . Reprocessors of waste packaging oft en 249 start with a feedstock that is more -or-less a single polymer, though other materials and objects 250 such as closures , labels, glues, inks, and residues of materia ls and substances from the item s’ 251 use such as food or beverages may also be present . Materials and substances may also become 252 adhered or attached to packaging during handling and sorting during the use phase. For 253 instance , a plastic bottle that has been collected, mixed, compacted in a waste collection vehicle, 254 and deposited on a dumpsite may exhib it surface contamination with food and dust, or have 255 materials such as paper or metal trapped within its folded structure (Gall et al., 2020) . 256 ‘Contamina nts’ are removed during several sorting steps that prepare the material for 257 reprocessing including size reduction (comminution), separation by density (sink/float), 258 washing (either hot, cold and or with chemicals) and optical separation (near infra -red or laser) 259 (Vogt et al., 2021) . A manual sorting step is almost always included at some point between 260 collection for recycling and reprocessing , because mechanical means are rarely sophisticated 261 enough to obtain sufficient material quality to make new products. There are a multitude of 262 configurations of waste plastic reprocessing operations from the highly sophisticated facilities 263 common in Europe , some of which employ robotics and automated quality management 264 systems, to extremely rudiment ary operations seen in some areas of the Global South (Neo et 265 al., 2021) . 266 3.2 Environment 267 3.2.1 Global warming potential 268 The majority of Life cycle assessment (LCA ) studies of post -consumer plastic waste 269 management support the ranking system offered by the ‘Waste Hierarchy ’ (European 270 Commission, 2008) . Lazarevic et al. (2010) reviewed 77 scenarios reported in 10 LCA studies 271 that evidenced im pacts of mechanical reprocessing , feedstock recycling, incineration and 272 landfill to compare the relative burdens across six LCA impact categories. Compared to 273 incineration, mechanical reprocessing showed a lower a biotic depletion potential, energy use 274 and global warming potential findings that were supported more recently by Bernardo et al. 275 (2016) . 276 An exception highlighted by Lazarevic et al. (2010) was evidence from Frees (2002) , indicating 277 that high levels of surface contamination with ‘organic’ (hereafter ‘biological’) material resulted 278 in substantial burdens associated with hot water washing , wastewater treatment and plastic 279 waste pre-treatment. Accor ding to Lazarevic et al. ( 2010) , these burdens increased the emissions 280 from mechanical reprocessing to more than those emitted by incineration . However , a contrary 281 result was reported by Krogh et al. (2001) who r eported that despite the high biological material 282 contamination (7% - by weight - wt.), mechanical reprocessing had 100% better overall 283 performance compared to incineration. Theoretically, the addition of sodium hydroxide to the 284 washing process should nega te the need for hot water use, however there is evidence that both 285 heat and the caustic additive are used in combination as reported in some LCA studies (Aryan et 286 al., 2019) . Importantly though, very few LCAs investigate reprocessors operating in a Global 287 South context, meaning that process data are absent for these facilities (Laurent et al., 2014a) . A 288 few excepti ons (non -exhaustive search) exist for China (Gu et al., 2017; Zhang et al., 2020) , 289 India (Aryan et al., 2019; Choudhary et al., 2019) and Brazil (Martin et al., 2021) . 290 3.2.2 Water use 291 Clearly water consumption is a concern in countries where it is scarce, however according to 292 Laurent et al. (2014b) it is reported in less than 15% of LCA waste management studies. As a 293 guide to the magnitude of water consumption during mechanical reprocessing , Chen et al. 294 (2019) provided water depletion p otential factors for the mechanical reprocessing of several 295 polymers, indicating between 340 and 452 L t-1 material processed and waste -water discharge of 296 between about 65 and 95% depending on the polymer being processed ( Table S2). Aryan et al. 297 (2019) reported much higher water use; 1,200 L t-1 for polyethylene (PE) milk pouches and 298 1,600 L t-1 for polyethylene terephthalate (PET) reprocessed at a comparatively small -medium 299 scale facility in India. The water use reported at the plant not only contributed to freshwater 300 aquatic ecotoxicity, but also marine aquatic ecotoxicity and eutrophication. M oreover, the plant 301 used coal to heat the water and dry the pouches in the winter when the sun provided insufficient 302 heat. 303 The rapid review of YouTube studies carried out here (Table 4) observed the use of sodium 304 hydroxide in four sources, mainly those that were more technologically sophisticated, handling 305 large quantities of post -consumer material. However , eight of the processes observed did not 306 clean ma terial using water ; instead, mainly secondary plastic foils were fed either directly into 307 extruders or via a comminution step. It is unclear how common this ‘dry processing’ is, but it 308 has been reported to be carried out by Aryan et al. (2019) in India and has been observed at 309 Biffa Polymers in the UK (Houston, personal communication, 27 November 2019) . 310 Table 4: Summary of practices involving plastics reprocessing in the Global South observed on multimedia posts with identification of hazards and hazard mitigation practices. 311 Source Context Feedstock Process description Dry/ wet Soph. cat. Hazards Mitigation measures or comments 1 2 3 4 5 6 7 8 Daharwal (2018) Nagpur, India Plastic bags Manual separation, comminution, particle manually moved to extruder and made into mini -football sized lumps of polymer Dry Low x x x x x x  No obvious SSW  No PPE use  No guarding on equipment Mooge Tech. (2015) Assumed China PET packaging Co-located sorting and reprocessing system including de -baling, trommel, ‘de -labelling (rotating star), electromagnetic separation, high speed friction washing, centrifugal dewatering, comminution, float sink separation Wet Med- high x x x  Only one worker observed wearing gloves to sort manually, possibly drawing in risk on several con veyors though film not detailed enough to assess this. Triwood1973 (2009) China PET bottles Polyester spinning includes comminution, float sink separation, washing, drying and extrusion into fibres which are then carded and woven into polyester sheet Wet Med- high x x x x  PPE – face shield used  Gloves used by some workers  Possibly insufficient respiratory protective equipment used during carding sps (2018a) India LDPE bags Clean, dry bags fed by hand into extruder which produces strands that are cooled and cut into pellets Dry Low x x x x  No SSW in place  Stick to feed material in to extruder prevents drawing in  Open top sandals around molten plastic sps (2018b) India LDPE bags Clean, dry bags sorted by hand and cleaned with a knife then fed by hand into extruder which produces strands that are cooled and cut into pellets x x x x x IndustrieS (2019) India Hard plastics Material manually loaded in baskets into shredder Dry Low x x x x  No obvious SSW  No PPE used and all in open top sandals  No guarding on equipment  Women help each other with heavy loads Saha (2020) Bangladesh Misc. coloured PET packaging Hand sorting and grading of material on the floor with low sided baskets followed by comminution, washing and s ink float separation where material skimmed by hand. Appears to be a hot wash but not obviously so. Wet med x x x x x  No obvious SSW  No PPE used and all in open top sandals or bare feet  No guarding on equipment The Times of India (2019) India hard plastics Material crushed and extruded with durability additives then pelletised and re -melted and formed into tiles Dry low – med x x x x  No obvious use of PPE though few workers shown Kao (2014) Manual de -baling and summary sort before inclined conveyor feeds trommel. Process then includes more intensive manual sorting, a hot wash (possibly caustic) – film seemed to stop prematurely Wet med x  Stop rope above conveyor  Gloves worn by approx. 50% of staff  Some use of face coverings  Some use of hearing protection  Evidence of SSW Source Context Feedstock Process description Dry/ wet Soph. cat. Hazards Mitigation measures or comments 1 2 3 4 5 6 7 8 Carretino Proyectos (2016) Sriracha Thailand Plastic packaging Mechanical loading of bales into automated de -baler followed by caustic wash and drying tumbler, lights separated with cyclon e then missed labels removed manually (special tool) on conveyor. Comminution followed by sink float separation to remove closure materials followed by another caustic wash and drying tumbler – yet another sink float carried out before high purity achieved . Final manual polishing to increase purity - no extrusion here. Wet Med- high x x x x x  Huge sign on front of building states ‘safety first’  Signage throughout building warning of danger  Gloves worn by all workers  Face coverings worn by ~20% of workforce –presumably according to need  High level of safety evident Micro Machinery Manufacture (2018) India Woven PP raffia sacks Hand sorted before being hand fed directly into extruder dry – extruded into strands and pelletised (possibly this is a display machine) Dry med x x x  No obvious SSW  No PPE use & all operatives in bare feet  Very little guarding on equipment Kumar (2019) South Asia (assumed) Dry fed shredder created flake which was manually fed into an extruder and pelletised Dry low x x x  No obvious SSW  No PPE use  No guarding on equipment Potdar (2015) South Asia (assumed) electrical insulation cables Apparently are course shredded and then manually transferred to a hoper and extruded into strands Dry Low- med x x x x x x x  No obvious SSW  No PPE use  No guarding on equipment Singh (2018) India Mixed plastic packaging Comminuted and mixed in a dark environment where workers manually load between unit processes including washing, drying and extrusion. Wet x x x x x x x x  No obvious SSW  No PPE use  No guarding on equipment  Very dark & terrifying conditions GlobeTrotter (201 3) Ahmedabad, India Pipes, polythene moulding materials Material is handfed directly into extruder stranded and pelletised 1.8 - 1.9 tonne s per day Dry Low med x  No obvious SSW  No PPE use  No guarding on equipment Hazard codes as follows: 1) Unguarded fast or high torque machinery in close proximity to workers; 2) Worker interaction with machin ery resulting in risk of being drawn in; 3) High temperature 312 equipment in close proximity to workers risking burns; 4) Risk of inte raction with unknown potentially hazardous materials or substances; 5) Risk of burns from caustic substance; 6) Particle loss to the 313 environment likely; 7) Risk of aerosolised hazardous substance; 8) Risk of ballistic injury to hands, feet, body from inter action with sharp or heavy objects. Abbreviations: Waste electrical and electronic 314 equipment (WEEE); end of life vehicle (ELV); safe system of work (SSW); pers onal protective equipment (PPE); polyethylene terephthalate (PET); low density polyethylene (LDPE ); polypropylene 315 (PP); sophistication category (Soph. cat.). The term ‘wet’ refers to process in which plastics were subjected to washing and or sink -float separation; the term ‘dry’ refers to processes in which no water 316 was used other than for cooling str ands for palletisation. 317 3.2.3 Management of residues 318 A concern highlighted in recent years, is the management of residues (solid rejects) by plastics 319 reprocessors in countries where mismanagement of waste in general is also reported to be high 320 (European Environment Agency, 2019) . The infer ence is that non-targeted for recovery materials ( low 321 value plastic s or those that are problematic to sort and concentrate and contraries ), may be 322 mismanaged by dumping on land, discharge into waterways and coastal waters and open burning (Lau 323 et al., 2020) . 324 Though there are no academic studies that provide systematically gathered evidence on the prevalence 325 of residue mismanagement by reprocessors , several documentaries and news articles have highlighted 326 the pheno menon with film footage and still photographic evidence (60 Minutes Australia, 2019; BBC 327 News, 2020; CBC News, 2019; Fruhnert, 2014; Sky News, 2018 ) as well as reports such as Velis 328 (2014) . The existence of the problem is also inferred by increasing regulation to curb transboundary 329 movements of post-consumer plastic recyclate (often termed ‘scrap’) particularly from high -income 330 countries to industrialised nations in the Global South. For instance, there are indications tha t part of 331 the rationale for the Chinese Authority’s virtual ban (hereafter the ‘Chinese import ban’) on plastic 332 imports in 2018 (Ministry of Ecology and Environment, 2017) was to reduce the risk of residue 333 mismanagement (Liang et al., 2021) . 334 Following the Chinese import ban, considerable amounts of material has been diverted to other 335 countries , such as Turkey and several South and Southeast Asian countries including Malaysia, 336 Thailand, Vietnam, Indonesia, Taiwan and India (Resource Futures -Nextek, 2018) . This has resulte d 337 in planned or actual tightening of import restrictions, as their respective authorities fear 338 mismanagement of residues that they are unable to enforce (APL, 2018; Bedi, 2019; CMA CGM 339 (Japan), 2018; Cotecna, 2018; D as, 2018; Government of India: Ministry of Environment Forest and 340 Climate Change, 2016; ISRI, 2018; Liang et al., 2021; Resource Recycling, 2019; Staub, 2018a; b; 341 2019) . Moreover, the mismanagement of residues from imported post-consumer plastic was te was the 342 motivating rationale of the parties to the Basel Convention , who implement ed significant restrictions 343 on the export of plastics from high income countries to the Global South from January 2021 344 (Secretariat of the Basel Convention, 2019) . 345 In addition to the mismanagement of residues, Operation Clean Sweep (2020) , Boucher et al. (2017) 346 and Cole et al. (2016) have reported that plastics reprocessors are likely to be a proportionally small 347 but significant source of micropla stic pollution as a result of comminuted flakes and spilled pellets 348 that are discharged into foul and surface water drainag e systems during reprocessing. T here is still 349 very high uncertainty over the magnitude of plastic pellet loss from reprocessors. For instance, Cole et 350 al. (2016) estimated pellet loss from the plastics industry as a whole at between 5.3 and 53 billion 351 pellets (105 -1,054 tonnes) per annum from the UK alone , based on 4.8 Mt being processed 352 (reprocessor inputs) . Lassen et al. (2015) provided a very rough estimate for plastics processors in 353 Denmark, estimating that between 0.0005% and 0.01% of production may be lost as microplastics to 354 the environment. 355 The rapid review of multimedia evidence prese nted in Table 4 indicated that pellet loss was 356 uncontrolled in at least five out of the 15 facilities observed. This assertion is based on the assumption 357 that the facilities observed did not have closed circu it wastewater treatment, and that there was 358 observable evidence of material being spille d and discharged into drainage. 359 3.3 Health 360 3.3.1 Emissions to air 361 Emissions from e xtrusion of the main conventional plastics used in packaging, such as polypropylene 362 (PP), PE, PET, high density polyethylene and low density polyethylene (LDPE) are not thought to 363 result in harm to human health if carried out at controlled temperatures and using relatively pure 364 feedstock. A study by Unwin et al. (2013) of atmospheric emissions at ten UK plastics extrusion 365 facilities (PP, PE, acryl onitrile butadiene styrene , PET and polyvinyl chloride - PVC), found 366 extremely low and often undetectable concentrations of carcinogens in all cases. All the sites and 367 processes investigated by Unwin et al. (2013) incorporated a variety of engineering controls , 368 including forc ed air ventilation local exhaust ventilation and mechanical dilution. 369 In the Global South, ventilation may not always be provided in plastics extrusion facilities. For 370 example, a review by Cook et al. (2020b) found examples of facilit ies investigated in China where 371 only passive ventilation was provided as a control measure. Other examples were identified in the 372 multimedia evidence presented in Table 4, where workers were in close proximity to extruders 373 without any observable mechanical ventilation or personal protective equipment. In several cases 374 there was evidence that end -of-life vehicle parts and electrical goods including PVC insu lation were 375 being extruded without any form of ventilation or respiratory protective equipment. Speculatively, 376 insufficient ventilation may be a widespread reality where resources are limited and there is a lack of 377 sufficiently resourced, independe nt health and safety regulation. 378 Although the most common polyolefins and PET do not usually result in harmful emissions if 379 ventilation is sufficiently controlled, there some is evidence that if materials are not sourced or sorted 380 carefully then they may be i nadvertently mixed with plastics such as polystyrene and PVC , both of 381 which result in harmful emissions when extruded (Cook et al., 2020b; He et al., 2015) . Moreover, if 382 the polyolefins and PET have originated form a source that involves some potentially hazardous 383 substances being added, for example electrical casings, then these substances may volatilise when 384 heated, exposing work ers. For instance, analysis by Tsai et al. (2009) next to polypropylene and 385 polyethylene extrusion facilities in Taiwan detected phthalates in air samples indicting that PVC had 386 contaminated the feedstock. In two other studies, both Tang et al. (2014) and Tang et al. (2015) 387 detected brominated flame retardants in envir onmental media near to plastic packaging recycling 388 plants in China. Though the source was potentially confounded, the implication from these findings is 389 that plastics from end of life vehicles, and electrical equipment plastics were being reprocessed into 390 secondary feedstock regardless of the potential carcinogenic and environmentally persistent 391 substances within. Moreover, Tang et al. (2014) found high concentrations of brominated flame 392 retardants in hair samples of young people who may work in plastics extrusion plants within the local 393 area. 394 395 3.3.2 Accidents 396 Accident s in plastics reprocessing facilities are not specifically reported by the International Labour 397 Organization (2019) , instead being aggregate d across the waste industry, often including water and 398 utilities. There are also no specific reports in the academic literature. The multimedia evidence 399 presented in Table 4was used as a reference and highlighted some d eeply concerning practices at 400 small and medium scale reprocessors operating in the Global South, particularly in India and China. 401 For instance, evidence of the potential for workers to beco me entangled or drawn into fast moving or 402 high torque machinery was observed at almost all facilities. In nine of the facilities observed, workers 403 also carried out duties in very close, unprotected proximity to extremely hot machinery used for 404 extrusion. The lack of robust and systematically obtained data on this topic makes it challenging to 405 accurately assess, but c learly there are also some well managed plants in the Global South, where 406 workers’ safety is systematically managed and emissions are controlle d to protect public health ; and 407 this level of safety was apparent from the multimedia footage in two of 15 examples (Carretino 408 Proyectos, 2016; Kao, 2014) . 409 3.3.3 Food contact applications and legacy substances 410 Some plastics contain potentially hazardous substances that have been added intentionally or which 411 have been unintentionally incorporated through adsorption, absorption, during production or 412 conversion (Cook et al., 2020b) . These substances are not u sually bonded to the polymers themselves, 413 but exist between the polymer chains as part of a mixture (Hahladakis et al., 2018; Wiesinger et al., 414 2021) . These may migrate into the outside world from where they can disperse, or be absorbed into 415 the body through the skin ; via ingestion of food ; or through mucous membranes under certain 416 condit ions (Koch et al., 2009) . 417 In much of the Global North and South, the use of hazardous substances in food contact packaging is 418 tightly controlled by legi slatory frameworks designed to limit exposure to human health and the 419 environment depending on the application (Cook et al., 2020b) . Thus , the use of recycled (secondary) 420 plastics in food contact materials presents additional challenges because of t he potential uncertainty 421 around the origin of the material (primary production and manufacturing phase), its previous use (use - 422 phase) and the way that it may have been handled, stored and treated after it has been used (end -of- 423 life-phase). 424 For example , to reduce the risk of fire, plastics used in many electronic goods are treated with flame 425 retardants which are potentially harmful to human health if absorbed into the body. If these electronic 426 casings were used to make food packaging, there is a risk that they might migrate from within the 427 polymer and leach into the food being packaged, potentially exposing the consumer. These substances 428 are often described collectively as ‘legacy substances’ (Wagner et al., 2020) . A summary of potential 429 materials and substances that may exist in a secondary plastic is provided in Table 5. 430 Table 5: Summary of constituents in plastics; after Goulas et al. (2000) , Hahladakis et al. (2018) , Cook et al. 431 (2020b) and Wiesinger et al. (2021) . 432 Life cycle phase Residual substance or substance group Examples Production & manufacturing Polymers  Polyethylene, polyvinyl chloride, polyethylene terephthalate Production residues  Residual monomers (bisphenol A, styrene), dimers and oligomers  Residual catalysts Additives  Plasticisers (e.g. di -(2-ethylhexylexyl)), fillers, brominated flame retardants (e.g. polybrominated diphenyl ethers) Use Food  Cooking oil Household chemicals  Pesticides  Paint stripper End-of-life Commercially used substances  Engine oil  Battery acid 433 Legacy substances may occur in all secondary plastics, however the concentration is usually so small 434 as to be unlikely to pose any threat to human health (Wagner et al., 2020) . Nonetheless, the potential 435 risks are managed through stringent legislation in several countries. For instance, in India, the 436 Ministry of Health and Family Welfare (2018) has recently prohibited the use of recycled content in 437 food packaging under the Food Safety and Standar ds (Packaging) Regulations, 2018. Thailand, Japan 438 and China have also historically implemented similar bans, however there are indications that these 439 laws may be relaxed to encourage more circular materials use (PackagingLaw.com, 2020; Rosato, 440 2020) . 441 In Europe, the use of recycled content was banned in food contact packaging until fairly recently. 442 However , Regulation EC 282/2008 (European Union, 2008) now allows secondary material use as 443 long as c ertain conditions are met including requirements to: 444  Use recycled plastic behind a ‘functional barrier’ as defined by Directive 2002/72/EC 445  Sort plastic to 100% efficiency, though where provenance is more certain, e.g. from a 446 kerbside separate collection (e ither comingled ‘single stream or separated ‘multi -stream’ 447 collection), this requirement can be lowered on a case by case basis 448  Characterise input (feedstock) to determine if substances from misuse of the product are 449 present (e.g. an orange juice container used to contain domestic pesticide) 450  Obtain authorisation (from the relevant ministry) to use recycled content in conversion 451 feedstock 452 It is beyond the scope of this review to carry out a comprehensive review of regulatory frameworks 453 managing the use of re cycled content in food contact materials, but it appears that other countries 454 allow its use including Mexico (PetStar, 2018) , South Africa (Petco, nd) , and Brazil 455 (PackagingLaw.com, 2019) . 456 4 Approach 2: Bottle -to-fibre reprocessing 457 4.1 Overview 458 Approximately 52% (wt.) of all textile fibre s are polyester , representing 55 Mt of material produced in 459 2018 (Textile Exchange, 2019) . Of this 13% (7.2 Mt), was produced using a mixture of post - 460 consumer PET bottles and post -industria l spun polyester fibre. Although the proportional and absolute 461 mass of polyester produced from recycled content has increased steadily over the last decade, a 462 reduction of three percentage points took place following the Chinese import ban (Ministry of 463 Ecology and Environment, 2017) , highlighting the impact of international restrictions on the circular 464 economy. 465 The use of secondary PET in polyester production has increased , alongside the amount of PET 466 collected for recycling. But a greater proportion of the PET that is collected for recycling is now used 467 in packaging (66%) whilst the remainder is used in bottle -to-fibre reprocessing (44%) (Park et al., 468 2014; Sarioğlu et al., 2018) . 469 Polyester spinning does not differ greatly from other mechanical reprocessing systems for extrusion or 470 blow moulding. It produces textile fibres that are as strong or in some cases stronger than its virgin 471 counterparts as chain scission is substantially reduced in comparison to conventional mechanical 472 reprocessing (Muslim et al., 2016; Shen et al., 2010) . 473 4.2 Environment 474 4.2.1 Global warming 475 Virgin polyester results in approximately 2.2 -2.7 t C O2eq t-1 product (Bartl, 2020) compar ed to, for 476 example, cotton produced in China which has been reported to be between 5.2 and 57.9 t C O2eq t-1 477 across the whole lifecycle (Wang et al., 2015) . However , LCA studies that evaluate the benefits of 478 recycling PET into polyester fibre are limited , with just three relevant studies that have directly 479 compared impacts, all of which showed a reduced emissions burden in comparison to virgin 480 production (Komly et al., 2012; RDC -Environment, 2010; Shen et al., 2011) . 481 In compar ison with mechanical reprocessing for extrusion (Approach 1 – Section 3), bottle -to-fibre 482 recycling has been found to have similar (Shen et al., 2011) or lower impact on global warming 483 (Komly et al., 2012; RDC -Environment, 2010) , mainly because the material that it replaces (virgin 484 polyester and cotton) has very high burdens. These indicative results challenge the conception that 485 bottle -to-fibre recycling, so called ‘open -loop’, is less beneficial than bottle -to-bottle recycling , so 486 called ‘closed loop’, because the output of bottle -to-fibre recycling (textiles) is not suitable for 487 recycling in future (Geyer et al., 2016) . 488 4.2.2 Water use 489 There are few clear estimates for water use from polyester spinning processes. Bartl (2020) suggested 490 that primary polyester spinning uses 48.8 m3 t-1 water (excluding printing and dyeing) and Zhang et al. 491 (2018) estimated 24.2 m3 t-1. It seems reasonable to assume that similar quantities are used for 492 recycled PET and that cleaning and separation processes are similar to those carried out for 493 conventional recycling. Possibly a more importan t comparator is for cotton , which has been reported 494 to use between 2,000 and 27,000 m3 t-1 produced (Bartl, 2020) . Otherwise , there is no reason to 495 assume that bottle -to-fibre reprocessing has a different water consumption rate in comparison to 496 bottle -to-bottle. 497 No specific data were found to indicate microplastic release from bottle -to-fibre reprocessing ; 498 however , it is reasonable to assume that it is the same as for other conventional recycling processes. 499 4.3 Health 500 No evidence that has not already been discussed in Section 3.3 was found to indicate specific health 501 hazards from polyester spinning. But, objective reasoning suggests that the use of only one polymer 502 (PET) in bottle -to-fibre reprocessing, which is mainly used in packaging, may lower the risk of 503 contamination from materials that have been used in other applications - for instance end of life 504 vehicles or electrical and electronic equipment. 505 5 Approach 3: Mineral p olymer composites 506 5.1 Overview 507 5.1.1 Road -surfacing (Approach 3a) 508 The use of waste plastics in road surfacing has been investigated as a solution to the plastic pollution 509 crisis and could be used to recover unrealised value from the waste system (Chin et al., 2019; Wu et 510 al., 2021) . This potential has been embraced by some states in India (Karelia, 2018; Louise, 2019; 511 News18, 2019) , and the National Rural Roads Development Agency (nd) has developed guidelines 512 for the use of plastic waste in roads. 513 To clarify, the roads discussed here are not made purely from plastic. Instead , the bitumen component 514 is typically modified with around 5% wt. (2-10% wt.) plastic (Rødland, 2019) . This means that when 515 aggregate and sub -layers are included, the total mass of plastic used as a proportion of road 516 construction mass is very small. Polymer modification of bitumen is well established , having been 517 investigated since the 1950s and has been in common use since the 1980s (Zhu et al., 2014) , where it 518 is used to improve elasticity reduced rutting, fatigue resistance, reduced thermal cracking, and 519 increased elasticity (Ahmadinia et al., 2011; Costa et al., 2013; Dalhat et al., 2017; Fang et al., 201 4; 520 Movilla -Quesada et al., 2019; RAHA Bitumen Co., nd; White, 2019; White et al., 2018) . Until 521 recently , it has been exclusively carried out using virgin polymers , including PE, PP, ethylene –vinyl 522 acetate, ethylene –butyl acrylate, styrene –butadiene –styrene, styrene –isoprene –styrene and styrene – 523 ethylene/butylene –styrene. 524 5.1.2 Bricks and tiles (Approach 3b) 525 The use of waste plastics as a bonding agent for the manufacture of tiles and b ricks is becoming 526 increasingly widespread , having been implemented by several charities including WasteAid UK 527 (Lenkiewicz et al., 2017) . Several proprietary and open source processes are available (Earth Titan, 528 2019) that involve melting plastic together with sand to form a paste which is then pressed into 529 moulds and left to cool. At its most basic, the process is carried out over a fire, whereas some 530 processes observed were more automated (Kolev, 2019) , including mechanical pressurised moulding, 531 mechanical mixing, and comminution of plastics with low speed high torque cutting mills (Earth 532 Titan, 2019) . In one example, sand was kiln dried to improve the properties of the final product in 533 advance of the plastic waste being added (NTVUganda, 2013) . 534 Historically, there has been a paucity of published academic literature on brick and tile production 535 using waste plastics, though several recent papers have exp lored the approach , finding it results in 536 products with very high durability and strength (Ali et al., 2020; Salvi et al., 2021; Thorneycroft et al., 537 2018; Uvarajan et al., 2021) . According to Kumi -Larbi et al. (2018) who tested the physical properties 538 of LDPE -bonded sand, the compressive strength of the composite is greater than Portland cement 539 sandcrete and similar to C20/25 concrete. 540 5.1.3 Unbound aggregate 541 Gu et al. (2016) reviewed 83 studies that investigated the use of plastics in concrete as a lightweight 542 replacement for aggregate. Although it was not within the scope of the present review to assess this 543 end-use, it is referred to here to identify it as a potential avenue of further research. 544 5.2 Environment 545 5.2.1 Global warming 546 According to Wu et al. (2021) , very few studies have investigated global warming emissions from 547 polymer modified asphalt , referring to just f ive studies that indicate mixed resul ts from using waste 548 plastics in comparison to virgin plastics. Four of these (Santos et al. (2018) , Vila-Cortavitarte et al. 549 (2018) , Mukherjee (2016) and Nascimento et al. (2020) , investigated plastics that are not commonly 550 used in FMCG packaging (rubber, polystyrene etc.) . Only one, Poulikakos et al. (2017) investigated a 551 range of waste plastics used in packaging, reporting substantial cost savings alongsi de a reduction in 552 CO 2 emissions. The model was highly theoretical and intended to demonstrate the potential concept 553 rather than being based on physical implementation. It assumed that the plastics would not require 554 substantial processing (cleaning and puri fying) to be suitable for use in roads, reducing the 555 environmental burdens associated with mechanical reprocessing , which was one of the comparators. 556 Whether this uncertainty in material composition would be acceptable to road manufacturers is 557 unclear. 558 There is insufficient data available to make an assessment over whether the use of waste plastics as a 559 bitumen modifier provides overall environmental improvement across the lifecycle. Intuitively , 560 anything that reduces the need to resurface or replace roa ds using a product that would otherwise be 561 wasted ought to provide some benefit. Given that there is substantial evidence to indicate that polymer 562 modification of bitumen results in increased durability, it seems likely that its use would result in 563 reduced maintenance and associated avoided burdens. Further investigation using post -consumer 564 waste plastic packaging would provide more insight. 565 No LCA data was found for mineral -polymer composites used in the production of bricks, tiles or 566 paving slabs. As th is technology begins to increase in prevalence, it will be important to understand 567 the full life -cycle impacts. Clearly, rudimentary processing advocated by WasteAid uses very few 568 resources (Lenkiewicz et al., 2017) . The removal of plastic film would benefit the local environment 569 though the process requires relatively c lean sand , which would need to be sourced sensitively and 570 sustainably (Torres et al., 2021) . The LCA case is likely to be strongly driven by the avoided concrete 571 production , which is intensive sector with high energy demand (discussed further in Section 9.1) but 572 it is noteworthy that the heat sued to melt the mineral -polymer mixture may be provided by open, 573 uncontrolled fires. Therefore , the climate change impact of black carbon production may also have a 574 significant effect on the overall environmental emissions (Reyna -Bensusan et al., 2018) . 575 5.2.2 Particle emissions (microplastics) 576 One concern highlighted by Rødland (2019) is the potential for microplastic release from the polymer 577 modified road surface during the use phase. The study reported microplastic emissions from each 578 source in Norway at approximately 28 t y-1 polymer modified asphalt, 90 -320 t y-1 road marking 579 polymer and 4,250 -5,000 t y-1 from tyres. The source of most of the data reported by Rødland (2019) 580 is Vogelsang et al. (2020) who acknowledged that there is huge uncertainty associated with the 581 emission factors for polymer modified bitumen ; but, the main particle emission source is likely to be 582 studded tyres , used to drive through ice and snow in northern Europe, that abrade the road surface. 583 A potential risk is that the surface may become less durable if asphalt -polymer mixtures are 584 incorrectly formulated, for instance too rich in polymer. It is recomm ended that this theory is 585 investigated as lack of durability could influence both life -cycle emissions and the risk of plastic 586 particle emissions. 587 Intuitively, there may also be risks associated with microplastic release, fire risk, and possibly 588 migration of substances into the air inside buildings. No evidence was found for any of these, but it is 589 suggested that this is considered in future investigations 590 5.3 Health 591 Asphalt is laid at 100 -195°C (Nicholls et al., 2013) . The top of this range of temperatures overlaps 592 with the lower end of the ra nge of temperatures used in mechanical reprocessing (Hahladakis et al., 593 2018) . Given the evidence for potentially hazardous emissions from extrusion and summarised in 594 Section 3.3.1 , it is conceivable that substances emitted during asphalt laying or brick and tile 595 production could pose a threat to the health and safety of those who inhale air nearby, for instance if 596 PVC, polystyrene or plastics from electrical goods or vehicles are used. There are no obvious 597 concerns from the main conventionally used polyole fins and PET used in packaging and studies have 598 found very low emissions from LDPE (Yamashita et al., 2009) and PE (He et al., 2015; Tsai et al., 599 2009) . 600 Both White (2019) , and White et al. (2018) , manufacturers of a proprietary modifier using discarded 601 plastics (wastage) from recyclers in the UK, investigated air and leachate emissions from polymer 602 modified bitumen. Their air sampling found no hazardous emissions other than those that would be 603 expected from the bitumen and no hazardous leachate was detected. 604 Discussions with Kumi -Larbi Jnr (personal communication 10 December 2020) who has observed tile 605 manufacture in West Africa, revealed that the process often resulted in the plastics combusting 606 briefly, which could potentially result in the production of sub stances of partial combustion. When 607 completely decomposed under combustion, LDPE emits only water and CO 2. However , the LDPE is 608 likely to include small amounts of antioxidant and ultraviolet resistant additives and is unlikely to 609 achieve complete combustion under very low heat used in the production process. Several relevant 610 sources , including Valavanidis et al. (2008) and Barabad et al. (2018) , reported low levels of 611 particulate matter being emitted during LDPE combustion at low temperatures. The only other source 612 of relevant information is from Wang et al. (2004) who report ed a range of emission data from PE 613 combustion. 614 5.3.1 Accidents 615 The multimedia evidence in Table S3, highlighted several hazards associated with brick and tile 616 production , including becoming entrained in high -speed or high torque machinery and having contact 617 with hot materials as they are formed and moulded to the shape of the tile or road surface. 618 6 Approach 4: Solvent based purification 619 6.1 Overview 620 So-called ‘chemical recycling’ technologies have received increasing attention from researchers who 621 want to overcome the challenges associated with sorting and reprocessing the complex mixtures of 622 polymers and additives found in post -consumer waste plastics (David son et al., 2021) . One is 623 ‘solvent -based purification’, an approach that uses solvents to dissolve polymeric materials, allowing 624 them to be separated from the additives and contaminants found in the plastics. There are seven 625 groups of process according to Ügdüler et al. (2020) : 1) Shake -flask extraction; 2) Soxhlet extraction / 626 batch multi -stage extraction; 3) Ultrasonic extraction; 4) Microwave assisted extraction; 5) 627 Supercritical fluid extraction; 6) Accelerated solvent extraction; and 7) Dissolution -precipitation. 628 Mechanical reprocessing involves heating polymers, adding a the rmal even t to their history and 629 causing some of the chains to break (chain scission/ decomposition) and thus weaken the overall 630 structure. Solvent -based purification keeps the polymer chains intact, thus creating a higher quality 631 end product . However , the removal of solvents post -separation remains an issue in some processes, 632 potentially hindering commercial viability (Zhao et al., 2018) . Some authors argue that solvent based 633 purification should not be classified as ‘chemical recycling’ , because the polymers are not completely 634 deconstructed, and it should instead be classed as mechanical reprocessing (Crippa et al., 2019) . As 635 the solvents target specific polymers, the process should be applicable to the recovery of polymers 636 from layered multi -material packa ging (Kaiser et al., 2018; Walker et al., 2020) or even the pl astic 637 fractions in mixed material textiles such as polyester cotton mixtures (Sherwood, 2020; Thiounn et al., 638 2020) . 639 There is evidence of at least one pilot plant operating the CreaSolv® and Newcycling® process in 640 Indonesia (Unilever, nd) . The facility is capable of processing 3 t d-1 of water sachet waste per day 641 (1,000 t y-1) (Unilever, nd) and has aspirations to increase this to 30,000 t y-1. According to Crippa et 642 al. (2019) no other commercially viable solvent based purification facilities are currently operational. 643 Ügdüler et al. (2020) agree with this assertion, indica ting that most processes are between TRL 3 and 644 8. 645 6.2 Environment 646 As explained by Crippa et al. (2019) , there is very little real world process data available for solvent 647 based purification as the technology group is not yet commercialised. Ügdüler et al. (2020) carried out 648 a basic LCA of two processes to remove additives, however , the work was highly theoretical and it 649 would be misleading to extrapolate further. 650 6.3 Health 651 Though this technology does not exist commercially, the use of solvents, their treatment and disposal 652 after-use is likely to be one of the most significant potential health concerns when this technology 653 becomes commercialised. As discussed by Ügdüler et al. (2020) , there are a multitude of solvents all 654 of which are targeted at differ ent additives. Many of these are potentially hazardous to human health 655 such as chloroform, xylene, n -hexane and cyclohexane. 656 7 Approach 5: Chemical depolymerisation (Chemolysis) 657 7.1 Overview 658 Approximately seven processes are grouped under the ‘depolymerisation ’ category: 1) Methanolysis; 659 2) Glycolysis; 3) Hydrolysis; 4) Ammonolysis; 5) Aminolysis; 6) Hydrogenation; and 7) Alcoholysis 660 (Kumar et al., 2011; Ragaert et al., 2017; Raheem et al., 2019) . Plastics are reacted under heat and 661 pressure with a range of substances including catalysts, acids, alkalis, alcohols causing the 662 depolymerisation of the polymers (Raheem et al., 2019) . 663 The most studied polymer for depol ymerisation is PET (Crippa et al., 2019) , which can be completely 664 decomposed into its starting materials such as ethylene glycol, terephthalic acid bis(2 -hydroxyethyl 665 terephthalate) (BHET), or partially into dimers, and oligomers of the aforementioned. Glycolysis of 666 PET is a commercially proven practice having been carried out for several decades by large chemical 667 producers (Ragaert et al., 2017) . Glycolysis of PET is suited to high quality, post -industrial feedstock 668 as shortcomings in the processes’ abi lity to remove dyes, copolymers and colourants make it unusable 669 in other contexts. 670 Presently, glycolysis is only used to process off -specification post -industrial textiles and carpet fibres 671 (Aquafil, 201 4). The hope is that one day glycolysis can be used for processing post -consumer bottles, 672 but as yet there is no evidence of this taking place at commercial scale (Crippa et al., 2019) . 673 Several niche plastics can also be viably depolymerised with chemolysis such as poly (γ- 674 butyrolactone) and aromatic polycarbonates, however as Sardon et al. (2018) explain, ‘plastics that 675 can be so easil y depolymerized lack suitable mechanical and thermal properties to be widely useful’ . 676 7.2 Environment 677 Given that there are only a handful of implemented facilities worldwide, it is unsurprising that there 678 are few LCA studies that compare the environmental impacts of PET glycolysis with other 679 technologies; only two are reported here. The first study by Shen et al. (2010) used data f rom Far 680 Eastern New Century Co. (FENC), a textile manufacturer who implements glycolysis of polyester 681 fibres to BHET oligomers that are then re -polymerised to produce new PET. The process was 682 compared with ‘semi -mechanical reprocessing ’ (process data from the Long John Group) that 683 involves sorting, flaking and palletising before re -extrusion, and full mechanical reprocessing where 684 flakes are directly extruded into filament. The glycolysis resulted in higher costs and global warming 685 emissions in comparison t o the other two options , but still resulted in approximately half the global 686 warming potential compared with virgin production. The study is based on highly specific industry 687 data, which were incorporated at face-value. 688 In a more recent LCA modelling effo rt by Meys et al. (2020) , glycolysis of PET (described as 689 ‘chemical upcycling’) is reported to perform slightly better than mechanical reprocessing , resulting in 690 a comparative improvement of 1.13 t CO 2eq t-1 processed. 691 Given the paucity of robust data and that the only two relevant studies are contradictory, there is no 692 clear indication of the relative benefits of this process ; it does not appear to have been used to process 693 packaging anyway. 694 7.3 Health 695 Assessing potential health implications of PET glycolysis is difficult in the absence of relevant data. 696 As with any chemical processing, consideration should be given to controlling process emissions to 697 protect the health of workers and the wider population. 698 699 8 Approach 6: Py rolysis or gasification 700 8.1 Overview 701 8.1.1 Pyrolysis 702 Pyrolysis is a process that has been manipulated by humans for centuries to make charcoal from 703 wood. Material is heated in the absence of oxygen , thereby preventing complete combustion . When 704 applied to waste plas tics, this results in a random scission and reforming of the polymer chains into a 705 mixture of hydrocarbons resembling many of those found in crude oil in liquid (80% wt.) and solid 706 (20% wt.) phase (Lopez et al., 2017; Ragaert et al., 2017) . At scale, this is carried out at between 707 200°C and 1100°C (often around 500°C) and under moderate pressure (1 -2 atm) (Mayer et al., 2019) . 708 The liquid fraction is often distilled into three basic fractions; kerosene; diesel; and l ight oils 709 (naphtha) and the solid material , known as char , includes non -combustible minerals and metals, as 710 well as a high proportion of black carbon (Butler et al., 2011) . More volatile substances are often 711 flared as a firm of disposal or combusted to recover energy that is used to contribute to the heat 712 necessary for the process. 713 The liquids from pyrolysis plant s are all combustible, and according to Crippa et al. (2019) , the most 714 viable end -use for these is as fuel for ships and power plants. If sufficiently refined, pyrolysis oils can 715 be used in higher grade applications , such as road vehicles or aviation (Lopez et al., 2017) . However , 716 the ambition of m any pyrolysis developers is to refine these oils into monomers and other compounds 717 that can be used in primary plastic production (Papari et al., 2021) . 718 The synthesis of plastic production feedstock using pyrolysis has the potential to both reduce the need 719 to extract further fossil fuels, and also reduce the disposal and recovery burden on other parts of the 720 waste management system (Hann et al., 2020) . Moreover, if the process was able to compete 721 commercially with mechanical reprocessing , the value of waste plastics would increase; creating a 722 disincentive to mismanage plastics. Though pyrolysis innovat ion has accelerated in recent years, there 723 is little evidence that pyrolysis oils have been used in the best -case scenario , which is to produce 724 monomer feedstock (Solis et al., 2020) . It is therefore assumed that the outputs of pyrolysis plants are 725 being used as fuel . 726 Solis et al. (2020) reported that s everal plastic waste pyrolysis plants exist, and that this indicates that 727 ‘conventional pyrolysis’ is currently at level 9 of technological readiness based on the opinion of an 728 academic expert . However, they also point out that there are few full -scale projects from which to 729 determine economic feasibility . This leaves some doubt about how close these projects are to 730 commercialisation. Khoo (2019) indicated that several plants exist including one in Japan (processing 731 15,000 t y-1); and two in the U S of which one processes 25,000 t y-1 and the other is expected to 732 process 100,000 t y-1 once operational. At time of writing, none of the plants reported by Khoo (2019) 733 are verified as providing commercially proven processes. 734 Whilst it is possible that these plants can maintain a pyrolytic process, some serious doubts have been 735 raised by Rollinson et al. (2019) and Rollinson et al. (2021) over whether any of these processes are 736 self-sustai ning or whether they require a constant external source of heat. Commercial sensitivities 737 and lack of transparent process data may prevent these questions being answered, at least in the short - 738 term. 739 8.1.2 Gasification 740 Similarly to pyrolysis, gasification reactio ns involve the restriction of oxygen to allow decomposition 741 of the polymers without complete combustion. Unlike pyrolysis, gasification takes place at higher 742 temperatures ( 700-1200°C) and some oxygen is introduced into the process (Solis et al., 2020) , 743 resulting in partial oxidation of some hydrocarbons and atoms. Carbon monoxide (CO), hydrogen 744 (H2), carbon dioxide (CO 2), methane (CH 4) and nitrogen (N 2) are prod uced alongside some of the 745 lower molecular weight hydrocarbons , such as ethane ( C2H6) and ethylene ( C2H4) (Ciuffi et al., 2020; 746 Punkkinen et al., 2017) . Collectively these are known as ‘syngas’. 747 Much heavier hydrocarbons are also produced resulting in a substance kno wn as char alongside tarry 748 substances. The tars are made up of a mixture of heterocyclic hydrocarbons such as pyridine, and 749 phenol; light aromatics such as benzene and toluene; polycyclic aromatic hydrocarbons such as 750 naphthalene and heavier hydrocarbons t hat are not often characterised (Wolfesberger et al., 2009) . 751 This complex blend of substances is highly undesirable in the process as it quickly condenses, 752 clogging and corroding pipework (Zeng et al., 2020) . The char itself becomes contaminated by the 753 tars, meaning it is unviable to clean, ref ine and utilise further (Benedetti et al., 2017; Lopez et al., 754 2018) . The presence of these solids and their disposal continues to hinder the business case for 755 gasification. Gasification of plastics produces less char compared to gasification of biomass or fibre 756 (Sharuddin et al., 2016) . However , the syn gas itself tends to contain higher concentrations of char 757 particulates; a key disadvantage to overcome when plastics are used as a feedstock (Lopez et al., 758 2018; Solis et al., 2020) . 759 Historically, commercial gasification has us ed coal as a feedstock (Higman, 2013) . Gasification plants 760 that use waste as a feed stock have also begun to emerge over the last 10 years, but there is no 761 comprehensive state of the industry review. Seo et al. (2018) reported four plants using waste as a 762 feedstock in operation; one in Japan, on e in Canada, and two in Europe. Jayarama Reddy (2016) also 763 reported multiple plants that were operational at some stage in the last 20 years, although it is clear 764 that some have clearly ceased operating. In a more recent study, Solis et al. (2020) reported three 765 gasification plants using plastics waste as a feedstock. 766 Hydrogen can be extracted from the syngas mixture , which can also be used to synthesise a range of 767 substances including methanol and ammonia (Antonetti et al., 2017) . Quicker (2019) , indicated that 768 gasification of homogenou s mixed plastics had been shown to be viable at a German run plant. 769 However , he cautioned that the plant has suffered from technical difficulties over many years and 770 questioned the overall viability of the process. E ven as a fuel production process , waste gasification 771 becomes less viable due to the need to remove moisture from the syngas before it is combusted. 772 Although synthesis of chemical s is the objective of gasification plants using coal as a feedstock 773 (Ciuffi et al., 2020) , Rollinson et al. (2020) suggest that this is unlikely to have happened at plants 774 using waste as a feedstock. I t is suggested that syngas from gasification is at best, converted into 775 fuels ; however , it is more likely that they are combusted directly in the plant, thus operating as an 776 incinerator. 777 8.2 Environment 778 The majority of studies that compare environmental performance of gasification and pyrolysis with 779 other approaches to waste management do so on the basis of a mixed waste feedstock. Relatively few 780 focus on plastics specific ally. One exception is Khoo (2019) , who compared emissions from 781 mechanical reprocessing , pyrolysis, gasificatio n and incineration in Singapore. Including avoided 782 burdens, the lifecycle emissions from pyrolysis were approximately 0.6 -0.8 t CO 2eq t-1 plastic 783 processed in three studies and for gasification they were 0.4 -0.9 t CO 2eq t-1 plastic processed. Though 784 both pyrolysis and gasification perfor med much better than incineration with energy recovery, they 785 resulted in higher emissions than mechanical reprocessing , which showed between 0.2 and 0.4 t 786 CO 2eq t-1 in three studies. 787 A mo st recent LCA presented by Schwarz et al. (2021) , provided detailed lifecycle carbon emiss ions 788 data for 25 polymers processed using the methods: gasification and pyrolysis with and without 789 monomer recovery; open and closed loop mechanical reprocessing ; depolymerisation (for two 790 polymers); dissolution (for 24 polymers); and incineration with and without energy recovery. 791 Superficially, the study agrees with the differences between emissions from each technology reported 792 by Khoo (2019) , though the emissions were generally higher for pyroly sis, gasification and 793 mechanical reprocessing and lower for incineration. Where pyrolysis and gasification were used for 794 monomer production, emissions were generally slightly lower than those from mechanical 795 reprocessing in the Schwarz et al. (2021) model. However , as stated t his is entirely theoretical and 796 there are no commercial plants available with which to validate such a model. 797 The study by Schwarz et al. (2021) was not carried out according to ISO14040, and the authors 798 exclude d sorting and collection emissions and model led pure polymers (no additives) for simplicity. 799 The exception was for two ‘case studies’ of 1) mixed PP and LDPE foils; and 2) Acrylonitrile 800 butadiene styrene containing brominated flame retardants. These were used to ‘test’ and compare the 801 counterfactual pure polymer results. Focussing on the mixed LDPE/PP foils, the case -study method 802 assumed that material sent to pyrolysis would require as much sorting as that sent for mechanical 803 reprocessing , and that material sent for gasification would require slightly less sorting . Residu es were 804 incinerated with energy recovery and assumed as 50% (wt.) for gasification and 59% (wt.) for 805 mechanical reprocessing and pyrolysis. The outcome of this case study was that that all the 806 technologies more or less equalised in their lifecycle emission s to a range between 3.2 t CO 2eq t-1 807 plastic processed (gasification for monomer production) and 5.2 t CO 2eq t-1 plastic processed by 808 incineration with energy recovery. 809 The case studies reported by Schwarz et al. (2021) are interesting because pyrolysis and gasification 810 innovators report that the unique selling point (USP) of their technologies are their versatility in 811 processing wastes that are too complex or contaminated to undergo mechanical sorting and 812 reprocessing, either because they are multi -layered or because they are technically and or 813 economically challenging to sort (Ragaert et al., 2017; Solis et al., 2020) . However, Schwarz et al. 814 (2021) indicate that significant sorting is required upstream of both gasification and pyrolysis of 815 plastics where the process outputs (gas, liquid) are intended to be used as feedstock for plastics 816 production , and that this could increase the overall lifecycle carbon emissions enough to nullify the 817 potential benefits. 818 The study and comparisons made by Khoo (2019) and the study by Schwarz et al. (2021) provide a 819 helpful indication of the potential lifecycle carbon emissions from gasification and pyrolysis of waste 820 plastics. However, the high uncertainty associated w ith LCA results, especially with technology that 821 is barely tested at scale, means that it is challenging to draw a robust conclusion. As demonstrated by 822 Schwarz et al. (2021) , there are some highly sensitive parameters for both approaches that can weaken 823 the environmental ‘bus iness case’ in comparison to mechanical reprocessing . Clearly neither is a 824 panacea. Both gasification and pyrolysis have experienced significant operational limitations, 825 including tar removal and char disposal for the former (Benedetti et al., 2017; Lopez et al., 2018; 826 Wolfesberger et al., 2009; Zeng et al., 2020) , and high energy inputs for the latter (Crippa et al., 2019; 827 Mayer et al., 2019; Ragaert et al., 2017; Sherwood, 2020) . 828 Regardless of any theoretical carbon reductions from pyrolysis and gasification in comparison to 829 mechanical reprocessing , if fugitive emissions are uncontrolled, the savings may be nullified. In 830 gasification, the emitted CO and CH 4 both have high climate forcing potential and in pyrolysis, 831 uncontrolled coal combustion emissions produce black carbon and CO 2 that would contribute 832 considerably to the overall process emissions. A basic Google search for pyrolysis and ‘India’ or 833 ‘China’ for instance, brings up numerous small -scale commercial pyrolysis units aimed at processing 834 waste tyres and household waste. Not only are these low -tech systems unlikely to incorporate air 835 pollution control systems, but the y have the potential to be operated without any regulatory oversight 836 or enforcement to ensure that process emissions are controlled to protect the environment and the 837 surrounding population. FMCG companies considering processing post -consumer plastic wast e using 838 gasification or pyrolysis should refer to the European Best Available Techniques for Incineration 839 (Neuwahl et al., 2019) that include details on process emission control and plant operation for the 840 technologies. 841 8.3 Health 842 8.3.1 Process emissions 843 Process emissions from gasification and pyrolysis have the potential to cause serious harm to health if 844 unmanaged. The oils from pyrolysis resemble the products of crude oil and contain a range of 845 hydrocarbons, many of which are potentially hazardous. For e xample, pyrolysis of plastic packaging 846 can produce ethylbenzene, styrene, toluene and a range of polycyclic aromatic hydrocarbons 847 (Budsaereechai et al., 2019; Miandad et al., 2019) . Pyrolysis also results in the formation of gasses 848 including hydrogen, methane, ethane, ethene, propane, propene, butane, and butene (Williams et al., 849 1999) . 850 Aside from the desirable gasses themsel ves (hydrogen, carbon monoxide), syngas from gasification 851 also contains several hazardous substan ces. Though the feedstock was not stated, a n example syngas 852 ‘contaminant ’ profile was provided by Block et al. (2019) and is shown in Table S 4. The syngas from 853 packaging plastics is unlikely to contain substantial quantities of halide, dioxins and related 854 compounds, metals or sulphur , aside from some small quantities fou nd in glues and labels 855 (Gerassimidou et al., 2020) . Yet, plastics are generally co-gasified alongside biomass or as part of 856 refuse derived fuel (RDF) / SRF from mixed waste , which may contain a vast array of materials and 857 substances that may result in wide ranging chemical species formation. 858 The tar from gasification of waste can include a wide range of highly hazardous substances : however , 859 when compared to other materials, r elatively little is produced when only plastics are used as a 860 feedstock (Block et a l., 2019) . Some tar is produced, and according to Robinson et al. (2016) , much of 861 this is found in the syngas itself creating a barrier to upgrade. 862 Tar from gasification is also found in the char at concentrations that make it unusable for upgrade. 863 Char from pyrolysis is generally much better quality. Multiple bench -scale efforts have been made to 864 valorise the char from both pyrolysis an d gasification of waste, and in theory it can be used to make 865 activated carbon a highly prized and versatile substance (Bernardo et al., 2010; Miandad et al., 2019) . 866 Bernardo et al. (2012) characterised char from pyrolysis of mixed plastics, biomass and tyres, finding 867 a range of potentially toxic elements, aliphatic hydrocarbons and aromatic hydrocarbons. Whilst the 868 hydrocarbons w ere able to be removed using sequential solvent extraction, the metals were more 869 problematic, presenting a barrier for upgrading the char for use. Bernardo et al. (2010) also analysed 870 char produced from a simulated mixed waste sample and determined that all samples would be 871 classified as hazardous under Council Decision 2003/33/CE and CEWME evaluation methods for 872 Ecotoxicity. Whilst there is clearly potential for further use of pyrolytic chars from plastics waste, it 873 seems likely that the barriers to upgrading will result in the material, either being combusted , either to 874 provide heat for the process or simply to dispose of it on -site, or disposed of as hazardous waste in 875 either a hazardous waste incinerator or hazardous waste landfill (Defra, 2013) . 876 The range of potentially hazardous substances produced by gasification and pyrolysis is not an 877 inherent barrier to safe operation and there are clearly engineering solutions to controlling process 878 emissions , as de tailed by Neuwahl et al. (2019) . However , these controls are costly and require a high 879 level of technical expertise to ensure that they are implemented and maintained to remain effective. 880 Safe operation is not guaranteed anywhere in the world and in countries that lack sufficiently well - 881 resourced and effective enforcement and regulation, there is a risk that process emissions from 882 gasification and pyrolysis may not be managed according to safe standards. 883 8.3.2 Hazardous waste 884 Unless combusted on-site for disposal or energy recovery , the hazardous chars , tars and liquids 885 produced by gasification and pyrolysis must also be treated or disposed of safely. This is important, 886 because sufficiently managed and regulated hazardous waste landfills or incineration facilities do not 887 exist in many parts of the Globa l South . For instance , it is estimated that in India, 70% wt. of 888 hazardous waste is mismanaged (Karthikeyan et al., 2018) . If this is the case, then neither gasification 889 nor pyrolysis should be considered. 890 8.3.3 Accidents 891 Lastly, as much of the growth in pyrolysis has taken place in the Global South, plants may be 892 constructed with limited safety considerations. Several life -threatening incidents of malfunction have 893 been reported including: an explosion at a plant in Panchkula (India) that resulted in several workers 894 being injured; Khanty -Mansiysk in Russia in 2012 that resulted in eight deaths; Budennovsk in 895 Russia; Chennai, India in 2014 that killed one and left one injured; and Joensuu (Finland) in 2014, 896 and Furth in Germany in 1998 that both resulted large emissions of toxic gas ses escaping and nearby 897 residents being evacuated (International Power Ecology Company, 2014) . 898 9 Approach 7: Co-processing in cement kilns 899 9.1 Overview 900 The high heat and hence energy use associated with cement production has prompted producers to 901 explore ways to reduce fossil carbon output from the sector that currently account s for 7% of the total 902 global anthropogenic emissions (between 2.3 and 2.6 Gt of CO 2eq) (Hertwich, 2020; Lehne et al., 903 2018) . One of the most widely adopted solutions is to co -combust waste, known as solid recovered 904 fuel (SRF), alongside or instead of coal (Gerassimidou et al., 2020) . This practice has been adopted 905 across Europe and where cement production f acilities substituted their energy requirements with SRF , 906 for example at a rate of: 42% in the UK in 2015 (MPA Concrete Centre, 2017) ; 83% in the 907 Netherlands; and 60% in Norway (Aranda Usón et al., 2013) . 908 SRF, is produced from non-hazardous mixed waste and therefore contains a combination of both 909 fossil (plastics , not bio -based ) and biogenic waste, the latter of which is carbon neutral when 910 combusted (Iacovidou et al., 2018) . There is some evidence from industry that plastics which have 911 been collected for recycling are also used to co -fire cement kilns (Brock et al., 2021; Jiao, 2020; 912 Republic Cement, 2020) and there is also evidence th at the residues from material recovery facilities 913 are used which contain a high proportion of plastic (Fyffe et al., 2016; Saveyn et al., 2016) . However , 914 there is no indication of how prevalent the practice of co -processing plastics that have been collected 915 for recycling is. 916 9.2 Environment 917 As the fuel used in cement kilns is commonly fossil oil or coal (lignite), almost any other fuel source 918 is likely to result in at least a small reduction in carbon emissions due to fugitive emissions of 919 methane and high energy used in coal extraction. Several LCA studies have investigated potential 920 reduction in emissions by using alternative fuels including SRF : for instance Georgiopoulou et al. 921 (2018) , Khan et al. (2020) , Vermeulen et al. (2009) , Bourtsalas et al. (2018) and Malijonyte et al. 922 (2016) . However , SRF is typically comprised of a complex mixture of materials, of which , for 923 example, 68% (wt. ar) are of biogenic origin such as paper, cardboard, wood, and natural textiles 924 (Séverin et al., 2010) . Therefore these studies do not provide a good indication of the potential 925 emissions from plastic packaging waste alone .GIZ-LafargeHolcim (2020) provided some indicative 926 emission factors for different materia ls co-processed in cement kilns. Factors for p lastics were not 927 reported , but the fossil element of the RDF and tyres, indicates a ballpark of between (~50 and 62 928 kgCO 2 GJ-1) respectively. This suggests co-processing of plastic packaging waste might result in the 929 same or slightly greater emissions compared to natural gas (58 kgCO 2 GJ-1) and slightly less than 930 petrol coke (95 kgCO 2 GJ-1) or coal 98 kgCO 2 GJ-1). 931 Only one review by Lazarevic et al. (2010) compared the use of plastic in cement kilns with other 932 treatment sources, identifying just two relevant papers. The first, Shonfield (2008) , presented a model 933 that compared a range of end -of-life treatment proc esses for plastics waste including combustion of 934 the plastic fraction of SRF in cement kilns. The model was theoretical , as no process data or prior 935 publications were available for the combustion of plastics without other materials and found the 936 purely pla stic SRF combustion to provide a net carbon emissions reduction in comparison to the use 937 of coal , despite the fact that most plastic is of fossil origin . The reason provided is that coal extraction 938 releases fugitive emissions of methane, a small yet non-negligible source of emissions from the life - 939 cycle of coal used in combustion; reported as 1.91 -4.23 g CH 4 kg-1 of coal (ar) for over and 940 underground mined coal respectively (Spath et al., 1999) . 941 The second study reviewed by Lazarevic et al. (2010) was by Jenseit et al. (2003) , which compared 942 the lifecycle impacts of plastic used to co -fire cement kilns with landfill and conventional mechanical 943 reprocessing for extrusion. As with Shonfield (2008) , the SRF co -firing performed slightly better than 944 incineration , but considerably worse than mechanical reprocessing , which showed the least 945 environmental impacts overall in both studies. 946 Two further papers w ere identified here that assess the lifecycle of plastics co -fired in cement kilns. 947 The first, Schmidt et al. (2009) , did not involve plastics typically used in packaging . They compared 948 an ‘end -of-life’ scenario in which used tyres were partly used to produce artificial turf and partly used 949 as a modifier in asphalt with a scenario where the tyres were co-combust ed in a cement kiln. 950 Overwhelmingly , the cement kiln scenario produced much higher emissions, adding confidence to the 951 premise that mechanical reprocessing provides greater overall lifecycle benefits. The second, Meys et 952 al. (2020) compared chemical recycling, mechanical reprocessing and plastics co -fired in cement 953 kilns. The re search found replacing lignite in cement kilns provided greater benefits compared to 954 incineration with energy recovery, chemical recycling for fuel production and feedstock, but was 955 performing worse than chemical recycling to monomers and mechanical reproc essing . Whilst the 956 comparisons with incineration and mechanical reprocessing are broadly commensurate with the other 957 studies, the various chemical recycling pathways are less certain. As acknowledged by Meys et al. 958 (2020) , these technologies are still relatively nascent and it is likely that future learning will improve 959 efficiencies. 960 9.3 Health 961 Most studies into the human health risks related to atmospheric emissions from co -firing alternative 962 materials relate to SRF produced from mixed (often residual) municipal solid waste rather than plastic 963 waste. For instance , studies by Rovira et al. (2010) and Rovira et al. (2016) investigated 964 environmental media near two plants in Spain, finding no notable difference in c oncentratio ns of 965 potentially toxic elements , particulate matter and dioxins and related compounds in soil, plants and air 966 surrounding the facilit ies. 967 In a bench scale trial, Conesa et al. (2011) characterised emissions from simula ted SRF, lignite co - 968 combustion complimented with field tests of an operational kiln that co -combusted with SRF. Sulphur 969 dioxide emissions decreased as a consequence of the reduced li gnite and emissions of several 970 PCCD/F congeners increased very slightly co mpared to the reference sample (coal) , but were still 971 much lower (range: 4.42-8.48 pg I -TEQ Nm-3) than the permitted levels of 100 pg I -TEQ Nm-3. The 972 paper reported that these findings were commensurate with four other sources (not reviewed here). 973 Conesa et al. (2011) remarked that emissions of dioxins and related compounds were more likely to 974 come from organic material in the plant feedstock (fuel) . In addition, the study found concentration 975 changes to be negligible for the six pri ority pollutant polycyclic aromatic hydrocarbons , and hydrogen 976 fluoride was not detected at all. Hydrogen chloride was slightly elevated , but within legal limits and 977 though some small changes were detected in the levels of potentially toxic elements , they were all 978 well within legal limits. 979 As a comparator, theoretical modelling carried out by Shonfield (2008) reported human toxicity 980 potential of mixed plastic co -fired in cement kilns at approximately 1100 kg eq. dichloromethane t-1 981 plastic combusted, less than landfill and incineration , but approximately double that of all other 982 technologies including mechanic al reprocessing and pyrolysis. 983 The limited evidence for emissions co-firing post-consumer plastic packaging in cement kilns does 984 not indicate that the emission of potentially hazardous substances is any greater than for coal alone 985 and that they may even be less. In Europe facilities that co -fire waste in cement kilns are regulated at 986 member state level by Directive 2000/76/EC (European Union, 2000a) as detailed in Section 10.3. 987 The Directive requires plants to be constructed and operated according to a series of ‘best available 988 techniques’ (BATs) detailed by Neuwahl et al. (2019) . Cement kilns tend to be operated by large 989 multinational corporations with sufficient resources to implement air pollutio n control practices. 990 Notwithstanding this, it is possible that environmental emissions may not be managed 991 comprehensively in less stringently regulated contexts . However , no evidence was found to support 992 that speculation. 993 10 Approach 8: Incineration with energy recovery 994 10.1 Overview 995 Waste incineration with energy recovery is one of the most rapidly expanding approaches to treating 996 mixed municipal solid waste (typically the residual part, not targeted for recycling) , favoured for its 997 effectiveness in reducing its mass (75% wt.), volume (90% v/v) and bioactivity (Christensen et al., 998 2011a; b; Dalager et al., 2011; Hjelmar et al., 2011a; Hjelmar et al., 2011b; Niessen, 2010) . More than 999 500 municipal solid waste incinerators exist in Europe (Blasenbauer et al., 2020) ; approximately 75 in 1000 the US (United States Environmental Protection Agency, 2019) ; 1200 in Japan (Amemiya, 2018) ; 172 1001 in Korea (Bourtsalas et al., 2019) ; and 390 in C hina (Ministry of Housing and Urban -Rural 1002 Development (MoHURD), 2019) , where the approach is fast becoming the dominant form of waste 1003 treatment (Li et al., 2015) . 1004 The high cost of construction and operation in comparison to land disposal (SYSTEMIQ et al., 2020) 1005 has meant that incineration has not been implemented extensively in the Global South. Incinerators 1006 require considerable expertise to operate and there have been several notable plant failures, for 1007 instance in India as reported by Nixon et al. (2017) . In another example, a facility completed in 2018 1008 by a European Chinese consortium in Addis Ababa, Ethiopia, was shut -down during the early stages 1009 of commissioning. Mutethya (2020) indicate d that the plant is now up and running again, though there 1010 is little further information to indicate the ongoing success of the project. 1011 Other examples include a planned facility in Kenya (Najimesi, 2019) , at least three in Delhi (Central 1012 Pollution Control Board, 2021) ; ‘inevitable’ planned plant construction in Malaysia (Kadir et al., 1013 2013) ; at leas t one in Indonesia (Bahrah et al., 2020) , and at least one in Myanmar (JFE Engineering 1014 Corporation, 2017) . 1015 10.2 Environment 1016 Studies that asses the lifecycle emissions of incineration predominantly focus on the combustion of 1017 mixed municipal solid waste . These studies show lower climate forcing emissions from incineration 1018 compared to landfill across the lifecycle (Laurent et al., 2014a) . This is because modern incinerators 1019 almost always recover as energy (EfW plants) , a large portion of which comes from biogenic sources 1020 (Zheng et al., 2019) and because landfill generates methane, which is never captured in its entirety 1021 (Bel Hadj Ali et al., 2020) . 1022 Plastics that have been collected for recycling are rarely incinerated in isolation , resulting in a 1023 corresponding paucity of process information to determine the lifecycle emissions from the practice. 1024 With the exception of Frees (2002) and perhaps one scenario reported by Shonfield (2008) , 1025 incinerated plastics result in higher climat e forcing emissions compared to mechanical reprocessing 1026 (Lazarevic et al., 2010) . Although approximately 1.9 Mt of bio-based plastics were produced in 2021 1027 (European Bioplastics, 2020) , 368 Mt are still made from fossil carbon (PlasticsEurope, 2021 ), and 1028 therefore result in an emission profile similar to fossil fuels. The small comparative benefit from 1029 incineration of waste plastic in compar ison with gas and coal i s that the latter two fuels result in 1030 fugitive emissions of methane during their extraction alongside the fossil fuels combusted during the 1031 process (Spath et al., 1999; Turconi et al., 2013) . By comparison, the extraction of oil to produce the 1032 plastics that have become waste sits outside the system boundary used to assess the lifecycle benefits 1033 of plast ics combustion in incineration plants (Alhazmi et al., 2021) . 1034 10.3 Health 1035 Incinerators operated in the Global North have been subject to increasingly stringent e missions 1036 thresholds since the late 1990s and early 2000s (Table S5 ). For example, i n Europe, emissions are 1037 strictly controlled and regulated under the Industrial Emissions Directive (European Union, 2010) . 1038 Some persistent organic pollutants, polycyclic aromatic hydrocarbons, potentially toxic elements and 1039 particulate matter are still emitted, but a t very low levels . For example, in the UK, particulate matter 1040 emissions from waste incineration represent just 0.02% of emissions from all sources , both nationally 1041 and in the immediate vicinity of incinerators (Maynard et al., 2010) . 1042 The effect of the Waste Incineration Directive (European Union, 2000b) limits on dioxin emissions in 1043 the UK provides an indication of the capability of emissions abatement practices , which have 1044 advanced considerably (Joint Research Centre, 2018) . As illustrated in Figure 1, the previously high 1045 emissions of polychlorinated dibenzo(p)dioxin and furans (PCDD/F) from UK incinerators was 1046 reduced to negligible quantities by 1997. Since then, dioxins from waste combustion have been 1047 almost entirely generated by small waste fires, accidental fires, and on N ovember the 5th (‘bonfire 1048 night’, a traditional celebration during which large fires are burned all over the UK). 1049 1050 Figure 1: Dioxin emissions from open burning and waste incineration in the UK; data after National 1051 Atmospheric Emissions Inventor y (2020) . Abbreviations: Polychlorinated dibenzo(p)dioxin and furans 1052 (PCDD/F); international toxic equivalency (I -TEQ). 1053 1054 Several studies indicate that the risk to human health from incineration is likely to be minimal 1055 (Douglas et al., 2017; Freni -Sterrantino et al., 2019; Ghosh et al., 2019) Although some non - 1056 negligible negative health outcomes are highlighted in systematic reviews by Tait et al. (2019) and 1057 Ashworth et al. (2014) , the evidence reviewed in both studies was temporal ly various, and some 1058 studies were ba sed on decades old incinerators that do not comply with current best available 1059 techniques. 1060 In China, municipal solid waste incineration emissions standards have followed a step -wise pattern of 1061 improvement in much the sa me way as was done in European the US (Cheng et al., 2010; Ji et al., 1062 2016) . With the exception of Pb and Cd, China’s limits , outlined in GB 18485 -2014 , are roughly on a 1063 par with Europe’s and are more stringent for sulphur dioxide (Wu, 2018) . Aside from China, there are 1064 two concerns with the implementation of waste incineration infrastructure in other parts of the Global 1065 South: 1) That some countries do not have effective, independent, well -resourced enforcement and 1066 regulation to ensure that process emissions are controlled to within safe limits (SYSTEMIQ et al., 1067 0100200300400500600700 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018PCDD/F emissions (g I -TEQ) MSW incineration Accidental fires Small-scale waste burning Bonfire night 2020) ; and 2) That the technology restricts the access of the informal recycling sector to valuable 1068 materials which contribute to their income (IJgosse, 2019) . 1069 1070 11 Assessment of risk to human health and the 1071 environment when implemented in the Global South 1072 The g rouped approaches are shown in Table 5 alongside their scores for environmental and public 1073 health risk and appropriateness for implementation in the Glo bal South. 1074 11.1 Group 1a (Conventional reprocessing) 1075 Conventional mechanical reprocessing (Approach 1) and bottle to fibre mechanical reprocessing 1076 (Approach 2) are likely to result in the fewest environmental emissions and cause the last harm to 1077 public health when implemented in the Global South in comparison to other approaches. The types of 1078 plastics used in plastic packaging are unlikely to result in emissions that are harmful to workers, 1079 provided that adequate ventilation is provided. While there is evidence that operators in the Global 1080 South do not always provide such control measures, they are low -cost, low -tech and easier to 1081 implement in comparison to the engineering controls required to mitigate emissions for the 1082 approaches in Group 2 and 3. Such interven tions to enable smaller, low -tech mechanical reprocessors 1083 to implement safe systems of work could be driven by FMCG companies, supporting their efforts to 1084 improve the circular economy whilst building capacity and improving working conditions in the 1085 Global South. 1086 Little evidence was found to distinguish between the risk of harm to human health associated with 1087 Approach 1 and 2, and the evidence for avoided lifecycle -burdens is comparable. Both approaches are 1088 mature, having been implemented at commercial scale since at least the 1980s and 1990s respectively. 1089 Table 6: Qualitative indication of the r isk to human health, and the environment and human health from eight approaches to recovering value from post -consumer plastic 1090 packaging waste that has been collected for recycling in the Global North and South; alongside the risk of operating below environmental and health protection standards in 1091 the Global South. 1092 Recovery type Material recycling Energy recovery Group Group 1a: Conventional reprocessing Group 1b: Mineral polymer composites Group 2: Chemical recycling Group 3: Combustion with energy recovery Approach number Approach 1 Approach 2 Approach 3 Approach 4 Approach 5 Approach 6 Approach 7 Approach 8 Approach name Conventional mechanical reprocessing Bottle -to-fibre mechanical reprocessing Mineral -polymer composites: road surfacing Mineral -polymer composites: bricks & tiles Solvent based purification Chemical de - polymeri sation (Chemolysis) Pyrolysis & gasification for feedstock Pyrolysis & gasification for fuel Co-processing in cement kiln s Incineration for energy recovery & 2-stage gasification * Global North Environment L L L ID ID ID ID MH MH MH Human health L L ID ID ID ID ID L L L Global South Environment ML ML ML ML ID ID ID MH MH H Human health ML ML ID ID ID ID ID H H H Commercial & technological maturity H H MH MH L L L MH H H Risk of operating below standards in Global South (appropriateness) ML ML ML ML H H H H H H Meaning of colours & patterns Low risk / high maturity Medium -low risk / medium -high maturity Medium high risk / medium low maturity High risk / low maturity * 2-stage gasification refers to the process whereby syngas is created through gasification and then n subsequently combusted in a downstream chamber within the same process. Qualitative 1093 scoring of risk to environment and human health and risk of operatio n below standards in the Global South : L = low risk ; ML = medium -low risk ; MH = medium -high risk; H = high risk . 1094 Qualitative scoring of level of commercial and technological maturity: L= low maturity ; ML = medium -low maturity ; MH = medium -high maturity ; H = high maturity . Approaches are 1095 organised into groups 1a, 1b, 2 and 3 according to the similarity of scores detailed in Section 2.4.3 . 1096 11.2 Group 1b : Miner al polymer composites 1097 Lack of published data for the mineral -polymer composite approaches ( A3a and A3b) makes them 1098 challenging to assess . As with extrusion, emissions from the types of materials and substances used in 1099 plastic packaging are unlikely to result in a serious risk to human health, though in the case of the 1100 brick and tile production, consideration is advised t hat the emission s from open fires could be more 1101 harmful than the emissions form the heated plastics themselves , if inhaled . 1102 Black carb on produced by the open uncontrolled fires used to heat plastics has a high global warming 1103 potential that could offset some of the benefits brought about by the inferred avoided burdens of the 1104 energy intensive conventional brick and tile production (concre te or ceramics) . Similarly, the use of 1105 plastic packaging waste to modify bitumen in road surfacing is unlikely to result in more harmful 1106 emissions than those already emitted by hot bitumen during surfacing operations. Though no specific 1107 evidence was found in support , the fact that modified bitumen increases the durability of roads, infers 1108 that its use could avoid burdens associated with road resurfacing and repairs over time. 1109 One possible concern is that plastics with potentially hazardous properties will be used as feedstock 1110 alongside the comparatively benign packaging plastics. Moreover, the risk that plastic packaging itself 1111 contains substances that are harmful when emitted during heating should not be overlooked , 1112 especially as the composition of plastic s used in some parts of the Global South are not necessarily 1113 tightly controlled. It is recommended that the approaches are explored with caution until a better 1114 understanding of the potential risk from emissions are explored further. 1115 11.3 Group 2 : Chemical recycling 1116 Three groups of approaches exhibited very similar assessment scores in this study, and were therefore 1117 grouped together for ease of discussion despite the array of technological difference between them. 1118 There is no strong evidence that any of the so called ‘chemical recycling’ techniques are 1119 commercially viable methods of producing feedstock for plastics production. As such there is also 1120 limited evidence of the associated emissions and environment al benefits beyond theoretical 1121 modelling. 1122 The processes all involve either heat, pressure, gasses or chemical solvents. Controlling these 1123 phenomena requires expertise, financial resources and ongoing maintenance to ensure that the health 1124 of workers, the public and the environment are not compromis ed. Moreover, the potentially hazardous 1125 solid wastes generated from some processes such as used solvents; tars and chars from gasification 1126 and pyrolysis; and air pollution control residues require careful handling, treatment and disposal to 1127 ensure that the y do not present an ongoing environmental hazard in the future. Many countries in the 1128 Global South do not have access to landfills let alone specialist hazardous waste disposal facilities. 1129 This factor alone, is a barrier to safe and sustainable implementat ion of any process that produces 1130 hazardous solid waste. 1131 11.4 Group 3 : Combustion with energy recovery 1132 Incineration of post -consumer plastic packaging waste that has been collected with the intention to be 1133 recycl ed does not recover value at the material level and has a similar global warming potential to 1134 other fossil fuels ; notably, such as resource recovery route cannot be accounted for as ‘recycling ’ by 1135 any commonly stated definition – technical or legal (Table S8). Incineration (with or without 1136 combined heat and power or tri -generation; and without carbon capture storage or carbon capture and 1137 utilisation ) is also likely to result in higher emissions of fossil CO 2 in comparison to all the other 1138 approaches; a gap that would possibly widen as electricity grids decarbonise over the coming decades , 1139 reducing the burdens for other technolog ical options such as mechanical processing. 1140 Very little information exists to evidence CO 2eq emissions from co -processing waste plastics in 1141 cement kilns because most studies focu s on SRF, a mixture of biogenic and fossil material from 1142 mixed non-hazardous waste. It is possible that across the lifecycle, the use of waste plastics as a fuel 1143 in place of coal is likely to result in a marginal benefit due to the fugitive emissions durin g coal 1144 extraction . 1145 Pyrolysis to fuel is a more mature approach compared to other ‘chemical recycling’ technologies and 1146 has the theoretical potential to be operated safely. In the case where pyrolysis oils are burned to 1147 generate electricity or power vehicle s, the overall process may result in slightly fewer climate forcing 1148 emissions compared to other fossil fuels such as coal or oil. However as the energy grid and vehicle 1149 fuel systems decarbonise, this benefit will dwindle. 1150 Some studies have indicated that h ot-water washing used to remove surface contamination from 1151 soiled plastic packaging may result in much higher emissions from mechanical reprocessing , in effect 1152 tipping the balance in favour of incineration. However , these comparators seem easily avoidable by 1) 1153 using sodium hydroxide in place of hot water, and 2) Changing the energy source for mechanical 1154 reprocessing . However, arguably these considerations do not extend on a complete environmental 1155 assessment. 1156 12 Conclusion s and prospects 1157 Our review compared eight approaches to managing post -consumer plastic packaging waste to 1158 determine whether they are ‘appropriate’ for implementation in countries that lack an independent, 1159 well-resourced and effective environmental and safety regulator. We assessed the potent ial for harm 1160 to human health and the environment from each technological solution by considering its maturity 1161 alongside the costs and specialist resources that might be required to mitigate such harm. 1162 All processes have the potential to be managed safely, but s afe operation is not guaranteed anywhere . 1163 We do not suggest that waste valorisation in the Global South is inherently hazardous . However, the 1164 resources and expertise that are required to implement engineering and management safety controls 1165 varies bet ween approaches . Where resources are scarce, approaches that require fewer resources to 1166 mitigate risk may be more appropriate. For example, at its most basic, b rick and tile production from 1167 mineral polymer composite s (Group 1b) requires little more than a mould, a trowel and a metal 1168 container on an open fire. Respiratory inhalation of emissions from the fire and melting plastic has 1169 been highlighted as a risk , but the hazards are easily and cheaply surmountable with basic engineering 1170 controls such as personal respiratory protection equipment and careful source management of 1171 feedstock. For technologies such as incineration (Group 3) and chemical recycling (Group 2) , safety 1172 management is more challeng ing, partly because of the high heat and pressure involved, but also 1173 because many of the chemical and material outputs can be highly hazardous to human health and the 1174 envir onment . Most countries in the Global South still lack comprehensive waste management for non - 1175 hazardous waste, let alone specialist facilities for managing such hazardous by -products. 1176 Conventional m echanical reprocessing operations (Group 1 a) are mature and capable of handling 1177 large amounts of material. Whilst there are hazards involved wi th both small and large operations, the 1178 expertise and cost to control those hazards is minimal in comparison to incineration or co -processing 1179 in cement kilns. 1180 Our review focussed on the final stages of the waste material flow that involve reprocessing and 1181 recovery, touching briefly on the risk involved with secondary use of mechanically reprocessed 1182 plastics. We did not consider in detail the wider waste system, in particular the systems that involve 1183 collection, sorting and supply, much of which is carried out by large numbers of informal actors, 1184 waste pickers who operate outside of mainstream waste management planning, often without and safe 1185 systems of work. Informality or not, we did not address the dilemma between small -scale, 1186 decentralised approaches ve rsus large scale, high -throughput processing (economies of scale) . Even if 1187 affordable, implementing safety and environmental protection measures is a substantial challenge 1188 across the predominantly informal waste sector in the Global South. However, to exclude informal 1189 actors in favour of large -scale, on the basis of west ern standards of safe operation, could risk cutting 1190 off material supplies whilst restricting income generation potential of some of the world’s poorest 1191 people. 1192 Chemical recycling processes h ave received attention in recent years for their potential to handle 1193 material that is either highly soiled, bonded into an assembly or bonded into a multi -layer composite. 1194 Yet the evidence indicates that none of these unique selling points ha ve been realis ed and no evidence 1195 was found to indicate that chemical feedstock is being produced from post -consumer plastic 1196 packaging in a commercially sustainable process. 1197 Innovation of new processes must be supported, but the urgency with which action must be taken to 1198 improve our use of resources and reduce plastic pollution is a much greater concern. Mechanical 1199 reprocessing is both commercially mature and has the lowest environmental impact compared to all 1200 the other approaches reviewed here. It is already implemente d worldwide, as a highly mechanised 1201 process in the Global North, and as a more labour intensive operation in the Global South. Th e 1202 principle limitation of mechanical reprocessing is that it is unsuitable for processing multilayer (multi - 1203 polymer) materials. In response, the hope that chemical recycling with actualise is proffered. Given 1204 how unlikely this is in the near future it is suggested that product redesign is considered. 1205 Though some of the approaches were reasonably well evidenced, process data for o perations in the 1206 Global South is very limited or non -existent and therefore not easily discoverable for most processes. 1207 Our review was comprehensive but not exhaustive. Only a carefully conducted systematic review will 1208 reveal the true state of evidence on this topic and it is strongly recommend such a process is carried 1209 out, building on our work and bringing a more robust insight into the topic. 1210 1211 1212 CRediT author statement 1213 Ed Cook: Conceptualisation, methodology, investigation, writing – original and final draft; Costas A 1214 Velis: Review & editing, writing – final draft; Josh Cottom: Review & editing, writing – final draft. 1215 1216 Acknowledgements 1217 We are grateful to the project advisory board and technical reviewers who provided comments and 1218 insightful feedback su ggestions on earlier versions of this review, in particular: Professor David C 1219 Wilson (Independent consultant); Professor Linda Godfrey (Council for Scientific and Industrial 1220 Research – CSIR); David Lerpiniere (Resource Futures); Joanne Green (Tearfund); M ari Williams 1221 (Tearfund); Richard Gower (Tearfund). We would also like to thank the following people who kindly 1222 provided their time, advice, experience and expertise: Alexander Kumi -Larbi Jnr. (Imperial College 1223 London); Zoë Lenkiewicz (WasteAid); Sarah Edmo ndson; Carla Valle -Klann (UN Environment) . 1224 1225 Funding 1226 This research is the result of an independent review commissioned by Tearfund and funded jointly by 1227 Tearfund and the Norwegian Agency for Development Cooperation (NORAD) under Project 1228 Agreement QZA -20/0114 (‘From Trash to Cash: Turning plastic pollution into economic 1229 opportunity’). 1230