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{{short description|Processes which convert waste plastic into new items}}
]]]'''Plastic recycling''' is the process of recovering ] or ] ] and reprocessing the material into useful products. Since the majority of plastic is non-], ] is a part of global efforts to reduce plastic in the waste stream, especially the approximately 8 million metric tonnes of ] that enters the Earth's ocean every year.<ref name=HardestyWilcox>{{cite journal|author1=Hardesty, Britta Denise |author2=Chris Wilcox|title=8 million tons of plastic are going into the ocean each year|journal=The Conversation|date=13 February 2015|url=http://theconversation.com/8-million-tonnes-of-plastic-are-going-into-the-ocean-each-year-37521|access-date=21 February 2015}}</ref><ref name=Jambeck1>{{cite journal|last1=Jambeck, Jenna|first1=Science 13 February 2015: Vol. 347 no. 6223|title=Plastic waste inputs from land into the ocean|journal=Science|volume=347|issue=6223|pages=768–771|doi=10.1126/science.1260352|pmid=25678662|display-authors=etal|year=2015|bibcode=2015Sci...347..768J}}</ref>
{{use British English|date=July 2021}}
{{use dmy dates|date=July 2021}}
{{multiple image|perrow = 2|total_width=400
| header = Plastic recycling
| image1 = Municipal_recycling_facilities,_Montgomery_County,_MD._2007,_Credit_USEPA_(14410405277).jpg
| image2 = Bales of PET bottles stacked.jpg
| image3 = Watering can made from 12 recycled bottles, Intratuin Winschoten (2020) 01.jpg
| image4 = Агломерат ПВД.JPG
| footer = '''Clockwise from top left:''' {{bulleted list |Sorting plastic waste at a ] centre| Baled colour-sorted used bottles| Recovered ] ready for recycling| A watering can made from recycled bottles}}}}


'''Plastic recycling''' is the processing of ] into other products.<ref name="Genrev">{{cite journal|last1=Al-Salem|first1=S.M.|last2=Lettieri|first2=P.|last3=Baeyens|first3=J.|date=October 2009|title=Recycling and recovery routes of plastic solid waste (PSW): A review|journal=Waste Management|volume=29|issue=10|pages=2625–2643|doi=10.1016/j.wasman.2009.06.004|pmid=19577459|bibcode=2009WaMan..29.2625A |doi-access=}}</ref><ref>{{cite journal|last1=Ignatyev|first1=I.A.|last2=Thielemans|first2=W.|last3=Beke|first3=B. Vander|year=2014|title=Recycling of Polymers: A Review|journal=]|volume=7|issue=6|pages=1579–1593|doi=10.1002/cssc.201300898|pmid=24811748|bibcode=2014ChSCh...7.1579I }}</ref><ref name=cycles /> Recycling can reduce dependence on ], conserve resources and protect the environment from ] and ] emissions.<ref name="auto">{{cite journal |last1=Hopewell |first1=Jefferson |last2=Dvorak |first2=Robert |last3=Kosior |first3=Edward |title=Plastics recycling: challenges and opportunities |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |date=27 July 2009 |volume=364 |issue=1526 |pages=2115–2126 |doi=10.1098/rstb.2008.0311|pmid=19528059 |pmc=2873020 }}</ref><ref>{{cite journal |last1=Lange |first1=Jean-Paul |title=Managing Plastic Waste─Sorting, Recycling, Disposal, and Product Redesign |journal=ACS Sustainable Chemistry & Engineering |date=12 November 2021 |volume=9 |issue=47 |pages=15722–15738 |doi=10.1021/acssuschemeng.1c05013|doi-access=free}}</ref><ref>{{cite book |last1=Rudolph |first1=Natalie S. |last2=Kiesel |first2=Raphael |last3=Aumanate |first3=Chuanchom |title=Understanding Plastics Recycling:Economic, Ecological, and Technical Aspects of Plastic Waste Handling |date=2021 |publisher=Hanser |location=Munich |isbn=978-1-56990-846-4 |edition=2nd |url=https://www.sciencedirect.com/book/9781569908464/understanding-plastics-recycling |doi=10.1016/C2020-0-01631-2}}</ref> Recycling rates lag behind those of other recoverable materials, such as ], ] and ]. From the start of plastic production through to 2015, the world produced around 6.3 billion tonnes of plastic waste, only 9% of which has been recycled and only ~1% has been recycled more than once.<ref name="Geyer2017" /> Of the remaining waste, 12% was incinerated and 79% was either sent to landfills or lost to the environment as pollution.<ref name="Geyer2017" />
Compared with lucrative ], and similar to the low value of ], plastic polymers recycling is often more challenging because of low density and low value. There are also numerous technical hurdles to overcome when recycling plastic. ] are responsible for sorting and processing plastics. As of 2019, due to limitations in their economic viability, these facilities have struggled to make a meaningful contribution to the plastic supply chain.<ref name=":0">{{Cite web|url=https://resource-recycling.com/plastics/2019/09/05/municipal-sector-grapples-with-plastic-realities/|title=Municipal sector grapples with plastic realities|date=2019-09-05|website=Plastics Recycling Update|language=en-US|access-date=2019-09-05}}</ref>


Almost all plastic is non-] and without recycling, spreads across the environment<ref>{{cite journal |last1=Andrady |first1=Anthony L. |title=Assessment of Environmental Biodegradation of Synthetic Polymers |journal=Journal of Macromolecular Science, Part C: Polymer Reviews |date=February 1994 |volume=34 |issue=1 |pages=25–76 |doi= 10.1080/15321799408009632}}</ref><ref>{{cite journal |last1=Ahmed |first1=Temoor |last2=Shahid |first2=Muhammad |last3=Azeem |first3=Farrukh |last4=Rasul |first4=Ijaz |last5=Shah |first5=Asad Ali |last6=Noman |first6=Muhammad |last7=Hameed |first7=Amir |last8=Manzoor |first8=Natasha |last9=Manzoor |first9=Irfan |last10=Muhammad |first10=Sher |title= Biodegradation of plastics: current scenario and future prospects for environmental safety |journal=Environmental Science and Pollution Research |date=March 2018 |volume=25 |issue=8 |pages=7287–7298 |doi=10.1007/s11356-018-1234-9|pmid=29332271 |bibcode=2018ESPR...25.7287A |s2cid=3962436 }}</ref> where it causes ]. For example, as of 2015, approximately 8 million tonnes of waste plastic enters the oceans annually, damaging oceanic ecosystems and forming ].<ref name="Jambeck1">{{cite journal |last=Jambeck |first=Jenna |author-link=Jenna Jambeck |date=13 February 2015 |display-authors=etal |year=2015 |title=Plastic waste inputs from land into the ocean |journal=Science |volume=347 |issue=6223 |pages=768–771 |bibcode=2015Sci...347..768J|doi=10.1126/science.1260352 |pmid=25678662 |s2cid=206562155}}</ref>
When different ]s are melted together, they tend to ], like oil and water, and set in these layers. The ] cause structural weakness in the resulting material, meaning that ]s are useful in only limited applications. The two most widely manufactured plastics, ] and ], behave this way, which limits their utility for recycling. Each time plastic is recycled, additional virgin materials must be added to help improve the integrity of the material. So, even recycled plastic has new plastic material added in. The same piece of plastic can only be recycled about 2–3 times before its quality decreases to the point where it can no longer be used.<ref> ''National Geographic''. Retrieved 2019-06-26.</ref>


Almost all recycling is mechanical and involves the melting and reforming of plastic into other items. This can cause ] at the molecular level, and requires that waste be sorted by colour and ] type before processing, which is often complicated and expensive. Errors can lead to material with inconsistent properties, rendering it unappealing to industry.<ref name=EU-demand /> Though filtration in mechanical recycling reduces microplastic release, even the most efficient filtration systems cannot prevent the release of ] into wastewater.<ref>{{Cite web |last=Paul |first=Andrew |date=2023-05-08 |title=Recycling plants spew a staggering amount of microplastics |url=https://www.popsci.com/environment/recycling-plant-microplastics/ |access-date=2023-05-08 |website=Popular Science |language=en-US}}</ref><ref>{{Cite journal |last1=Brown |first1=Erina |last2=MacDonald |first2=Anna |last3=Allen |first3=Steve |last4=Allen |first4=Deonie |date=2023-05-01 |title=The potential for a plastic recycling facility to release microplastic pollution and possible filtration remediation effectiveness |journal=Journal of Hazardous Materials Advances |language=en |volume=10 |pages=100309 |bibcode=2023JHzMA..1000309B |doi=10.1016/j.hazadv.2023.100309 |issn=2772-4166 |s2cid=258457895 |doi-access=free}}</ref>
Recently, the use of ] as "molecular stitches"<ref>{{cite journal|last1=Creton C|title=Molecular stitches for enhanced recycling of packaging|journal=Science|date=February 24, 2017|volume=355|issue=6327|pages=797–798|doi=10.1126/science.aam5803|pmid=28232538|bibcode=2017Sci...355..797C}}</ref> or "macromolecular welding flux" has been proposed<ref>{{cite journal|last1=Eagan JM|display-authors=etal|title=Combining polyethylene and polypropylene: Enhanced performance with PE/iPP multiblock polymers|journal=Science|date=February 24, 2017|volume=355|issue=6327|pages=814–816|doi=10.1126/science.aah5744|pmid=28232574|bibcode=2017Sci...355..814E|url=https://zenodo.org/record/891450}}</ref> to overcome the difficulties associated with phase separation during recycling.<ref>{{cite web|last1=Fleischman T|title=Polymer additive could revolutionize plastics recycling|url=http://www.news.cornell.edu/stories/2017/02/polymer-additive-could-revolutionize-plastics-recycling|website=cornell.edu|publisher=Cornell University|access-date=23 February 2017}}</ref> Certain ]s, such as PLA, recycled by breaking down plastic polymers into their chemical building blocks, can be recycled hundreds of times.<ref></ref>


In feedstock recycling, waste plastic is converted into its starting chemicals, which can then become fresh plastic. This involves higher energy and ]. Alternatively, plastic can be burned in place of ]s in ], or biochemically converted into other useful chemicals for industry.<ref>{{Cite journal |last1=Zhang |first1=Fan |last2=Zhao |first2=Yuting |last3=Wang |first3=Dandan |last4=Yan |first4=Mengqin |last5=Zhang |first5=Jing |last6=Zhang |first6=Pengyan |last7=Ding |first7=Tonggui |last8=Chen |first8=Lei |last9=Chen |first9=Chao |date=2021-02-01 |title=Current technologies for plastic waste treatment: A review |url=https://www.sciencedirect.com/science/article/pii/S0959652620345674 |journal=Journal of Cleaner Production |volume=282 |pages=124523 |doi=10.1016/j.jclepro.2020.124523 |issn=0959-6526}}</ref> In some countries, burning is the dominant form of plastic waste disposal, particularly where ] policies are in place.
The use of ]s or plastics which can be organically recycled or can be composted in industrial composting is increasing for certain short-lived packaging applications.<ref>{{cite journal|doi=10.1016/j.tibtech.2007.01.001|pmid=17234288|title=Industrial biotechnology for the production of bio-based chemicals – a cradle-to-grave perspective|journal=Trends in Biotechnology|volume=25|issue=3|pages=119–124|year=2007|last1=Hatti-Kaul|first1=Rajni|last2=Törnvall|first2=Ulrika|last3=Gustafsson|first3=Linda|last4=Börjesson|first4=Pål}}</ref>


Plastic recycling is low in the ], meaning that ] and ] are more favourable and long-term solutions for ].
The percentage of plastic that can be fully recycled, rather than downcycled or go to waste, can be increased when manufacturers of packaged goods minimize mixing of packaging materials and eliminate contaminants. The ] has issued a "Design Guide for Recyclability".<ref>{{cite web|url=http://www.plasticsrecycling.org/images/pdf/design-guide/PET_APR_Design_Guide.pdf|title=PET_APR_Design_Guide.pdf|date=|website=PlasticsRecycling.org|access-date=13 July 2017}}</ref>


It has been advocated since the early 1970s,<ref name="The Plastics Issue" /> but due to economic and technical challenges, did not impact the management of plastic waste to any significant extent until the late 1980s. The plastics industry has been criticised for lobbying for expansion of recycling programmes, even while research showed that most plastic could not be economically recycled.<ref name=":3">National Public Radio, 12 September 2020 </ref><ref>{{Cite web |last=CBC |date=October 8, 2020 |orig-date=Sep 23, 2020 |title=Recycling was a lie — a big lie — to sell more plastic, industry experts say |url=https://www.cbc.ca/documentaries/the-passionate-eye/recycling-was-a-lie-a-big-lie-to-sell-more-plastic-industry-experts-say-1.5735618 |website=CBC Documentaries}}</ref><ref name=":4">PBS, Frontline, 31 March 2020, </ref><ref>{{Cite web |author=Dharna Noor |url=https://www.theguardian.com/us-news/2024/feb/15/recycling-plastics-producers-report |title='They lied': plastics producers deceived public about recycling, report reveals |work=theguardian.com |date=2024-02-15 |access-date=2024-02-16}}</ref> This has resulted in occasions where plastic waste dropped into recycling bins has not been recycled, and been treated as general waste.<ref>{{Cite news |last1=McCormick |first1=Erin |last2=Simmonds |first2=Charlotte |last3=Glenza |first3=Jessica |last4=Gammon |first4=Katharine |date=2019-06-21 |title=Americans' plastic recycling is dumped in landfills, investigation shows |url=https://www.theguardian.com/us-news/2019/jun/21/us-plastic-recycling-landfills |access-date=2024-07-06 |work=The Guardian |language=en-GB |issn=0261-3077}}</ref>
==Methods==
Broadly, there are two major ways to recycle plastic:<ref>{{Cite web|url=https://resource-recycling.com/plastics/2019/09/05/indorama-will-invest-to-meet-increased-rpet-demand/|title=Indorama will invest to meet increased RPET demand|date=2019-09-05|website=Plastics Recycling Update|language=en-US|access-date=2019-09-05}}</ref> (1) mechanical recycling ("chop and wash"<ref name=":2">{{Cite web|url=https://www.bloomberg.com/news/articles/2019-04-09/-unmaking-plastics-spurs-120-billion-potential-market-in-trash|title=These Companies Are Trying to Reinvent Recycling|last=|first=|date=|website=www.bloomberg.com|url-status=live|archive-url=|archive-date=|access-date=2019-09-05}}</ref>), where the plastic is washed, ground into powders and melted, and (2) chemical recycling, where the plastic is broken down into basic components.


== History ==
Before recycling, most plastics are sorted according to their resin type. In the past, plastic reclaimers used the ] (RIC), a method of categorization of polymer types, which was developed by the ] in 1988.{{citation needed|date=December 2017}} ], commonly referred to as PET, for instance, has a resin code of 1. Most plastic reclaimers do not rely on the RIC now; they use various sorting systems to identify the resin, ranging from manual sorting and picking of plastic materials to mechanized automation processes that involve shredding, sieving, separation by rates of density i.e. air, liquid, or magnetic, and complex spectrophotometric distribution technologies e.g. UV/VIS, NIR, Laser, etc.<ref></ref><sup></sup> Some plastic products are also separated by color before they are recycled.
Although ] before the 20th&nbsp;century, large-scale production was not realised until ]. ] replaced ] in parachutes, while ] was a light-weight alternative to glass in aeroplanes. After the war these materials were commercialized. The plastic age began around 1950, part of the ].


Global ] in the 1960s and 1970s led to the formation of environmental agencies. (], 1970), EU (], 1973) Australia (], 1971) and Japan (] 1971). Environmental awareness put plastic waste under scrutiny.<ref name="The Plastics Issue">{{cite book |last1=Huffman |first1=George L. |last2=Keller |first2=Daniel J. |title=Polymers and Ecological Problems |chapter=The Plastics Issue |date=1973 |pages=155–167 |doi=10.1007/978-1-4684-0871-3_10|isbn=978-1-4684-0873-7 }}</ref> The earliest effort to abate plastic pollution was arguably the ], whose Annex&nbsp;V banned dumping plastics in the oceans.
After sorting, for mechanical recycling the plastic recyclables are then shredded. These shredded fragments then undergo processes to eliminate impurities like paper labels. This material is melted and often ]d into the form of pellets which are then used to manufacture other products. The highest quality purification may be referred to as "regeneration".<ref>{{Cite web|url=https://www.paprec.com/en/understanding-recycling/recycling-plastic/regeneration-micronisation-and-grinding-plastics|title=UNDERSTANDING RECYCLING > RECYCLING PLASTIC > Regeneration, micronisation and grinding plastics|last=|first=|date=|website=www.paprec.com|language=en|url-status=live|archive-url=|archive-date=|access-date=2019-09-05}}</ref>


===Thermal depolymerization=== === Industry lobbying ===
] cleanup in 1970. The Keep American Beautiful campaign was a ] by the plastics and other polluting industries founded in the 1970s to try to displace responsibility of plastic pollution and other disposable packing trash onto consumers as "].<ref>{{Cite news|title=The Litter Myth : Throughline|url=https://www.npr.org/2019/09/04/757539617/the-litter-myth|access-date=15 June 2021|website=]|language=en}}</ref>]]
{{main|Depolymerization|Thermal depolymerization}}Scientists have estimated that the potential commodity value of waste plastic may be in excess of $300 per ton when used in process pathways yielding high-value chemical products or to produce electricity in efficient IGCC (]) processes.<ref>{{Cite journal|title=Process targeting: An energy based comparison of waste plastic processing technologies|pages=273–283|journal=Energy|volume=170|doi=10.1016/j.energy.2018.12.160|date=March 2019|last1=Fox|first1=James A.|last2=Stacey|first2=Neil T.}}</ref>


As regulations expanded, the plastics industry responded with lobbying to preserve their business interests. In the U.S., the 1970 Resource Recovery Act directed the nation towards recycling and energy recovery.<ref name="The Plastics Issue" /> More than a thousand attempts to pass legislation to ban or tax packaging, including plastics, came by 1976.<ref>{{Cite journal |last=Jaeger |first=Andrew Boardman |date=April 8, 2017 |title=Forging Hegemony: How Recycling Became a Popular but Inadequate Response to Accumulating Waste |journal=] |volume=65 |issue=3 |pages=395–415 |doi=10.1093/socpro/spx001 |issn=0037-7791}}</ref> The plastics industry responded by lobbying for plastic to be recycled. A $50&nbsp;million per year campaign was run by organisations such as ] with the message that plastic could and would be recycled,<ref name=":3"/><ref name=":4"/> as well as lobbying for the establishment of ].<ref>{{cite journal |last1=Elmore |first1=Bartow J. |title=The American Beverage Industry and the Development of Curbside Recycling Programs, 1950–2000 |journal=] |date=2012 |volume=86 |issue=3 |pages=477–501 |doi=10.1017/S0007680512000785 |jstor=41720628 |url=https://www.jstor.org/stable/41720628}}</ref>
====Waste plastic pyrolysis to fuel oil====
Plastic pyrolysis can convert petroleum-based waste streams such as plastics into fuels and carbons.<ref>
{{cite web
|url=http://www.pyrolysisplant.net
|title=Plastic Pyrolysis Plant
|publisher=RESEM Group China
|access-date=23 October 2016
}}</ref><ref>
{{cite news
|url=http://articles.timesofindia.indiatimes.com/2013-08-26/chennai/41454053_1_fuel-patent-device
|title=Engineer's plastic-to-fuel device passes patent office tests
|newspaper=The Times of India
|access-date=23 October 2016}}</ref><ref>{{cite web
|url=http://www.plastic2oil.com/site/home
|title=Plastic 2 Oil
|access-date=23 October 2016
}}</ref><ref>{{cite web
|url=https://web.archive.org/web/20200224211624/http://wedocs.unep.org/bitstream/handle/20.500.11822/13364/GLOCIIPresentationMurray.pdf?sequence=1&isAllowed=y
|title=Successfully Converting End-of-Life Plastics to Liquid Fuel project (P2F) by United Nations Environment Programme
|author=Michael Murray
|access-date=23 October 2016
}}</ref><ref>{{cite web
|url=http://biomassmagazine.com/articles/2067/power-and-fuel-from-plastic-wastes
|title=Power and Fuel from Plastic Wastes
|access-date=23 October 2016}}</ref>


However, plastic could not be economically recycled using the technology of the time. For example, an April 1973 report written by industry scientists stated that, "There is no recovery from obsolete products" and that, "A degradation of resin properties and performance occurs during the initial fabrication, through aging, and in any reclamation process." The report concluded that sorting the plastic is "infeasible". Contemporary scientific reports highlighted numerous technical barriers.<ref>{{cite journal |last1=Paul |first1=D. R. |last2=Vinson |first2=C. E. |last3=Locke |first3=C. E. |title=The potential for reuse of plastics recovered from solid wastes |journal=Polymer Engineering and Science |date=May 1972 |volume=12 |issue=3 |pages=157–166 |doi=10.1002/pen.760120302}}</ref><ref>{{cite journal |last1=Sperber |first1=R. J. |last2=Rosen |first2=S. L. |title=Reuse of Polymer Waste |journal=Polymer-Plastics Technology and Engineering |date=January 1974 |volume=3 |issue=2 |pages=215–239 |doi=10.1080/03602557408545028}}</ref><ref>{{cite journal |last1=Scott |first1=Gerald |title=Some chemical problems in the recycling of plastics |journal=Resource Recovery and Conservation |date=June 1976 |volume=1 |issue=4 |pages=381–395 |doi=10.1016/0304-3967(76)90027-5}}</ref><ref>{{cite journal |last1=Buekens |first1=A.G. |title=Some observations on the recycling of plastics and rubber |journal=Conservation & Recycling |date=January 1977 |volume=1 |issue=3–4 |pages=247–271 |doi=10.1016/0361-3658(77)90014-5}}</ref><ref>{{cite journal |last1=Leidner |first1=J. |title=Recovery of the Value from Postconsumer Plastics Waste |journal=Polymer-Plastics Technology and Engineering |date=January 1978 |volume=10 |issue=2 |pages=199–215 |doi=10.1080/03602557809409228}}</ref>
Given below is the list of suitable plastic raw materials for pyrolysis:
* Mixed plastic (HDPE, LDPE, PE, PP, Nylon, Teflon, PS, ABS, FRP etc.)
* Mixed-waste plastic from waste paper mill
* Multi-layered plastic.


Globally, plastic waste was almost entirely disposed of via ] until the 1980s when rates of ] increased. Although better technology was known,<ref>{{cite journal |last1=Poller |first1=Robert C. |title=Reclamation of waste plastics and rubber: Recovery of materials and energy |journal=] |date=30 December 1979|volume=30 |issue=1 |pages=152–160 |doi=10.1002/jctb.503300120}}</ref> these early incinerators often lacked advanced combustors or emission-control systems, leading to the release of ].<ref>{{cite journal |last1=Victorin |first1=K |last2=Stahlberg |first2=M |last3=Ahlborg |first3=U |title=Emission of mutagenic substances from waste incineration plants |journal=] |date=June 1988 |volume=6 |issue=2 |pages=149–161 |doi=10.1016/0734-242X(88)90059-6}}</ref>
===Heat compression===
Heat compression takes all unsorted, cleaned plastic in all forms, from soft plastic bags to hard ], and mixes the load in tumblers (large rotating drums resembling giant ]s). The most obvious benefit to this method is that all plastic is recyclable, not just matching forms. However, criticism rises from the energy costs of rotating the drums, and heating the post-melt pipes.<ref>{{cite web|url=http://recyclenation.com/green-glossary/heat-compression |title=recyclenation.com |publisher=recyclenation.com |date=2010-09-07 |accessdate=2019-01-29}}</ref>


In the late 1980s plastic recycling began in earnest. In 1988 the U.S. ] created the Council for Solid Waste Solutions as a ] to promote the idea of plastic recycling to the public.<ref>{{cite journal |last1=Liesemer |first1=Ronald |title=A perspective of the plastics waste issue in the United States |journal=Makromolekulare Chemie. Macromolecular Symposia |date=May 1992 |volume=57 |issue=1 |pages=1–13 |doi=10.1002/masy.19920570103}}</ref> The association lobbied American municipalities to launch or expand plastic waste collection programmes and lobbied U.S. states to require the labelling of plastic containers and products with recycling symbols.<ref name=":3" /><ref name=":4" />
====Distributed recycling====
Distributed recycling of plastics using ] (or DRAM) can include mechanical grinding to make granules for 1) fused granular fabrication, 2) heated ] printing, 3) 3-D printed molds coupled to ] and 4) filament production in a ] to fused filament fabrication.<ref>{{Cite journal|last=Dertinger|first=Samantha C.|last2=Gallup|first2=Nicole|last3=Tanikella|first3=Nagendra G.|last4=Grasso|first4=Marzio|last5=Vahid|first5=Samireh|last6=Foot|first6=Peter J.S.|last7=Pearce|first7=Joshua M.|date=June 2020|title=Technical pathways for distributed recycling of polymer composites for distributed manufacturing: Windshield wiper blades|journal=Resources, Conservation and Recycling|language=en|volume=157|pages=104810|doi=10.1016/j.resconrec.2020.104810}}</ref> For some waste plastics, technical devices called ]s<ref name="RPJ">{{cite journal | last1 = Baechler | first1 = Christian | last2 = DeVuono | first2 = Matthew | last3 = Pearce | first3 = Joshua M. | year = 2013 | title = Distributed Recycling of Waste Polymer into RepRap Feedstock | doi = 10.1108/13552541311302978 | journal = Rapid Prototyping Journal | volume = 19 | issue =sur 2| pages = 118–125 | url = https://digitalcommons.mtu.edu/cgi/viewcontent.cgi?article=1027&context=materials_fp }}</ref> enable a form of distributed recycling by making 3-D printing filament. Preliminary ] (LCA) indicates that such distributed recycling of ] to make filament of ] in rural regions is energetically favorable to either using virgin resin or conventional recycling processes because of reductions in transportation energy.<ref name="LCA">M. Kreiger, G. C. Anzalone, M. L. Mulder, A. Glover and J. M Pearce (2013). Distributed Recycling of Post-Consumer Plastic Waste in Rural Areas. MRS Online Proceedings Library, 1492, {{DOI|10.1557/opl.2013.258}}</ref><ref>{{cite journal | last1 = Kreiger | first1 = M.A. | authorlink4 = J. M. Pearce | last2 = Mulder | first2 = M.L. | last3 = Glover | first3 = A.G. | last4 = Pearce | first4 = J. M. | year = 2014 | title = Life Cycle Analysis of Distributed Recycling of Post-consumer High Density Polyethylene for 3-D Printing Filament | url = https://digitalcommons.mtu.edu/cgi/viewcontent.cgi?article=1035&context=materials_fp| journal = Journal of Cleaner Production | volume = 70 | issue = | pages = 90–96 | doi = 10.1016/j.jclepro.2014.02.009 }}</ref>


The industry introduced ]s in 1988, which provided a standard system for the identification of various polymer types at ].
=== Chemical recycling ===
For some polymers, it is possible to convert them back into monomers, for example, PET can be treated with an alcohol and a catalyst to form a dialkyl terephthalate. The terephthalate diester can be used with ethylene glycol to form a new ] polymer, thus making it possible to use the pure polymer again.


=== Global recycling trade ===
An estimated 60 companies are pursuing chemical recycling as of 2019.<ref name=":2" />
] during the 1990s included the export of plastic waste from advanced economies to developing and middle-income ones, where it could be sorted and recycled less expensively. The annual trade in plastic waste increased rapidly from 1993 onwards as part of the ].<ref name=Brooks2018>{{cite journal |last1=Brooks |first1=Amy L. |last2=Wang |first2=Shunli |last3=Jambeck |first3=Jenna R. |author-link=Jenna Jambeck |title=The Chinese import ban and its impact on global plastic waste trade |journal=] |date=June 2018 |volume=4 |issue=6 |pages=eaat0131 |doi=10.1126/sciadv.aat0131|pmid=29938223 |pmc=6010324 |bibcode=2018SciA....4..131B }}</ref>


Many governments count items as recycled if they have been exported for that purpose, regardless of the actual outcome. The practice has been labeled ], as environmental laws and enforcement are generally weaker in less developed economies.<ref>{{cite web |title=Trashed: how the UK is still dumping plastic waste on the rest of the world |url=https://www.greenpeace.org.uk/resources/trashed-plastic-report/ |website=] |access-date=20 May 2021 |language=en}}</ref><ref>{{cite journal |last1=Bishop |first1=George |last2=Styles |first2=David |last3=Lens |first3=Piet N.L. |title=Recycling of European plastic is a pathway for plastic debris in the ocean |journal=Environment International |date=September 2020 |volume=142 |pages=105893 |doi=10.1016/j.envint.2020.105893 |pmid=32603969 |doi-access=free|bibcode=2020EnInt.14205893B |hdl=10344/9217 |hdl-access=free }}</ref> By 2016 about 14 ] of plastic waste was exported, with China taking 7.35&nbsp;Mt.<ref name=Brooks2018 /> Much of this was low quality mixed plastic that ended up in landfills. However, recycled plastic is used extensively in manufacturing in China, and imported plastic waste was predominantly processed using low-technology processing. High-income countries such as Germany, Japan, the United Kingdom and the United States were the top exporters.<ref name=":1">{{Cite web |last=Environment |first=U. N. |date=2021-10-21 |title=Drowning in Plastics – Marine Litter and Plastic Waste Vital Graphics |url=http://www.unep.org/resources/report/drowning-plastics-marine-litter-and-plastic-waste-vital-graphics |access-date=2022-03-23 |website=UNEP - UN Environment Programme |language=en}}</ref>
In 2019, ] announced initiatives for ] of polyesters and polymer gasification to ] designed to handle a greater variety of used material.<ref>{{Cite web|url=https://www.greenbiz.com/article/eastman-advances-two-chemical-recycling-options|title=Eastman advances two chemical recycling options|last=Siegel|first=R. P.|date=2019-08-07|website=GreenBiz|language=en|access-date=2019-08-29}}</ref>


In 2017, China began restricting waste plastics imports via ]. Exporters eventually exported to other countries mostly in Southeast Asia, such as Vietnam and Malaysia, but also Turkey and India.<ref>{{cite journal |last1=Wang |first1=Chao |last2=Zhao |first2=Longfeng |last3=Lim |first3=Ming K |last4=Chen |first4=Wei-Qiang |last5=Sutherland |first5=John W. |title=Structure of the global plastic waste trade network and the impact of China's import Ban |journal=Resources, Conservation and Recycling |date=February 2020 |volume=153 |pages=104591 |doi=10.1016/j.resconrec.2019.104591|s2cid=214271589 |url=https://pureportal.coventry.ac.uk/en/publications/structure-of-the-global-plastic-waste-trade-network-and-the-impact-of-chinas-import-ban(399872a7-4c4a-45ab-9c5f-cd01133bcd42).html }}</ref><ref name=":02">{{Cite web|title=Piling Up: How China's Ban on Importing Waste Has Stalled Global Recycling|url=https://e360.yale.edu/features/piling-up-how-chinas-ban-on-importing-waste-has-stalled-global-recycling|access-date=12 October 2020|website=]|language=en-US}}</ref> Indonesia, Malaysia, and Thailand reacted to illegal plastic waste imports by reinforcing border controls. Illegally imported containers were repatriated or refused entry. Consequently, plastic waste containers accumulated in ports.<ref name=":1" />
In 2019, Brightmark Energy in the United States began building a facility to convert 100,000 tons of mixed plastic per into diesel, ] blend stocks, and ];<ref>{{Cite web|url=https://resource-recycling.com/plastics/2019/04/17/commercial-plastics-to-fuel-plant-receives-financing/|title=Commercial plastics-to-fuel plant receives financing|date=2019-04-17|website=Plastics Recycling Update|language=en-US|access-date=2019-09-05}}</ref> the company plans to expand into building another plant which can process an additional 800,000 tons of plastic per year.<ref name=":0" /> The company has said that the economics have a significant margin of safety from price declines.<ref>{{Cite web|url=https://resource-recycling.com/recycling/2018/11/27/investor-explains-decision-to-back-plastics-to-fuel-firm/|title=Investor explains decision to back plastics-to-fuel firm|date=2018-11-27|website=Resource Recycling News|language=en-US|access-date=2019-09-05}}</ref>


Given limited export options, attention turned to local solutions. Proposed ] would tax plastic producers to subsidise recyclers.<ref>{{cite journal |last1=Leal Filho |first1=Walter |last2=Saari |first2=Ulla |last3=Fedoruk |first3=Mariia |last4=Iital |first4=Arvo |last5=Moora |first5=Harri |last6=Klöga |first6=Marija |last7=Voronova |first7=Viktoria |date=March 2019 |title=An overview of the problems posed by plastic products and the role of extended producer responsibility in Europe |journal=Journal of Cleaner Production |volume=214 |pages=550–558 |doi=10.1016/j.jclepro.2018.12.256|bibcode=2019JCPro.214..550L |s2cid=158295219 |url=https://e-space.mmu.ac.uk/622465/1/Plastics.Paper.Final.pdf }}</ref>
===Other processes===
]
A process has also been developed in which many kinds of plastic can be used as a ] source (in place of ]) in the recycling of scrap ].<ref>{{Cite web |url=http://www.cnn.com/2005/TECH/08/10/plastic.steel.reut/index.html |title=Scientists use plastic to make steel|website=CNN.com|access-date=10 August 2005 |archive-url=https://web.archive.org/web/20050812011212/http://www.cnn.com/2005/TECH/08/10/plastic.steel.reut/index.html |archive-date=20 August 2004 |url-status=dead |df=dmy-all }}</ref> There are also possibilities for better recycling of mixed plastics, avoiding the need for expensive/inefficient separation of the plastic waste stream. One such method is called compatibilization which uses special chemical bridging agents called compatibilizers to maintain the quality of mixed polymers.<ref>{{cite journal | last1 = Ignatyev | first1 = I.A. | last2 = Thielemans | first2 = W. | last3 = Beke | first3 = B. Vander | year = 2014 | title = Recycling of Polymers: A Review | url = | journal = ChemSusChem | volume = 7 | issue = 6| pages = 1579–1593 | doi = 10.1002/cssc.201300898 | pmid = 24811748 }}</ref>


In 2019, international trade in plastic waste became regulated under the ]. Under the convention, any Party can decide to prohibit imports of hazardous plastic waste and, since 1 January 2021, of some mixed plastic wastes. Parties to the convention are required to ensure environmentally sound management of their refuse either through alternative importers or by increasing capacity.<ref name=":1" />
==Applications==


The ] temporarily reduced trade in plastic waste, due in part to reduced activity at waste management facilities, shipping disruptions, and low oil prices that reduced the cost of virgin plastic and made recycling less profitable.<ref name=":1" />
===PET===
{{main|PET bottle recycling}}
Post-consumer ] (PET or PETE) containers are sorted into different color fractions and baled for onward sale. PET recyclers further sort the baled bottles and they are washed and flaked (or flaked and then washed). Non-PET fractions such as caps and labels are removed during this process. The clean flake is dried. Further treatment can take place e.g. melt filtering and pelletizing or various treatments to produce food-contact-approved recycled PET (RPET). This sorted post-consumer PET waste is crushed, chopped into flakes, pressed into bales, and offered for sale.<ref name="innovations-report1">{{cite web|author=Idea TV GmbH |url=http://www.innovations-report.com/html/reports/environment_sciences/report-7183.html |title=Recycled plastic – the fashion fabric of the future |publisher=Innovations-report.com |date= |access-date=21 August 2010}}</ref>


===European Union strategic developments===
One use for this recycled PET is to create fabrics to be used in the ].<ref name="thisisbrandx1">{{cite web |author=PT, November 13, 2009 |url=http://www.thisisbrandx.com/2009/11/trashy-chic-recycled-clothing-from-playback.html |title=Trashy Chic: Recycled clothing from Playback – Brand X |publisher=Thisisbrandx.com |date=13 November 2009 |access-date=21 August 2010 |url-status=dead |archiveurl=https://web.archive.org/web/20100108231125/http://www.thisisbrandx.com/2009/11/trashy-chic-recycled-clothing-from-playback.html |archivedate=8 January 2010 }}</ref> The fabrics are created by spinning the PET flakes into thread and yarn.<ref name="innovations-report1"/> This is done just as easily as creating polyester from brand new PET.<ref name="rewarestore1">{{cite web|url=http://www.rewarestore.com/tech_recycled_pet.html |title=Reware's REWOVEN Technology Info: The Eco Narrative – Recycled PET |publisher=RewareStore.com |date= |access-date=21 August 2010}}</ref> The recycled PET thread or yarn can be used either alone or together with other fibers to create a very wide variety of fabrics. Traditionally these fabrics are used to create strong, durable, rough products, such as jackets, coats, shoes, bags, hats, and accessories since they are usually too rough for direct skin contact and can cause irritation.<ref>{{cite web|url=http://www.sustainableisgood.com/products/2008/04/billabong.html |title=Billabong ECO Supreme Suede Boardshorts: Sustainable is Good Eco Products |publisher=SustainableIsGood.com |date=9 April 2008 |access-date=21 August 2010}}</ref> However, these types of fabrics have become more popular as a result of the public's growing awareness of environmental issues. Numerous fabric and clothing manufacturers have capitalized on this trend.{{Citation needed|date=July 2017}}
The ]'s "Action Plan" for a circular economy, adopted in December 2015, saw plastics as a strategic priority for developing circular economy actions. In 2017, the Commission further adopted a focus on plastic production and use, targeting the achievement of all plastic packaging being recyclable by 2030. The Commission then issued a strategic document in January 2018 which set out an "ambitious vision" and an opportunity for global action on plastic recycling.<ref name=EU-demand />


==Production and recycling rates==
Other major outlets for RPET are new containers (food-contact or non-food-contact) produced either by (injection stretch blow) moulding into bottles and jars or by thermoforming APET sheet to produce clamshells, blister packs and collation trays. These applications used 46% of all RPET produced in Europe in 2010.{{citation needed|date=March 2013}} Other applications, such as strapping tape, injection-moulded engineering components and building materials, account for 13% of the 2010 RPET production.{{citation needed|date=March 2013}}
]


The total amount of plastic ever produced worldwide, until 2015, is estimated to be 8.3 billion tonnes (Bt).<ref name=Geyer2017 /> Approximately 6.3&nbsp;Bt of this was discarded as waste, of which around 79% accumulated in landfills or the natural environment, 12% was incinerated, and 9% was recycled - only ~1% of all plastic has been recycled more than once.<ref name=Geyer2017 /> More recently, as of 2017, still only 9% of the 9&nbsp;Bt of plastic produced was recycled.<ref>{{Cite web |title=What Percentage of Plastic is Recycled Globally? |url=https://bren.ucsb.edu/news/international-statistic-year-91-plastic-has-never-been-recycled |access-date=2024-01-22 |website=UCSB Bren School of Environmental Science & Management |language=en-US}}</ref><ref>{{Cite journal |last1=Nikiema |first1=Josiane |last2=Asiedu |first2=Zipporah |date=April 2022 |title=A review of the cost and effectiveness of solutions to address plastic pollution |journal=Environmental Science and Pollution Research |language=en |volume=29 |issue=17 |pages=24547–24573 |doi=10.1007/s11356-021-18038-5 |issn=0944-1344 |pmc=8783770 |pmid=35066854|bibcode=2022ESPR...2924547N }}</ref>
In the United States, the recycling rate for PET packaging was 31% in 2013, according to a report from The National Association for PET Container Resources (NAPCOR) and The Association of Postconsumer Plastic Recyclers (APR). A total of 1.798 billion pounds was collected and 475 million pounds of recycled PET used out of a total of 5.764 billion pounds of PET bottles.<ref>{{cite web|url=http://www.plasticstoday.com/articles/recycling-for-PET-packaging-reaches-31-percent-in-2013-141008|title=Recycling for PET packaging reaches 31% in 2013|work=PlasticsToday|access-date=12 March 2016|date=2014-10-08}}</ref>


By 2015 global production had reached some 381 million tonnes (Mt) per year.<ref name=Geyer2017>{{cite journal |last1=Geyer |first1=Roland |last2=Jambeck |first2=Jenna R. |author-link2=Jenna Jambeck |last3=Law |first3=Kara Lavender |title=Production, use, and fate of all plastics ever made |journal=Science Advances |date=July 2017 |volume=3 |issue=7 |pages=e1700782 |doi=10.1126/sciadv.1700782 |pmid=28776036 |pmc=5517107 |bibcode=2017SciA....3E0782G |doi-access=free}}</ref> The recycling rate that year was 19.5%, while 25.5% was incinerated and the remaining 55% disposed of, largely to landfill. These rates lag behind those of other recyclables, such as paper, metal and glass. Although the percentage of recycled or incinerated material is increasing each year, the tonnage of waste left-over also continues to rise. Production could reach ~800&nbsp;Mt per year by 2040, although implementing all feasible interventions could reduce plastic pollution by 40% from 2016 rates.<ref>{{cite journal |last1=Lau |first1=Winnie W. Y. |last2=Shiran |first2=Yonathan |last3=Bailey |first3=Richard M. |last4=Cook |first4=Ed |last5=Stuchtey |first5=Martin R. |last6=Koskella |first6=Julia |last7=Velis |first7=Costas A. |last8=Godfrey |first8=Linda |last9=Boucher |first9=Julien |last10=Murphy |first10=Margaret B. |last11=Thompson |first11=Richard C. |last12=Jankowska |first12=Emilia |last13=Castillo Castillo |first13=Arturo |last14=Pilditch |first14=Toby D. |last15=Dixon |first15=Ben |last16=Koerselman |first16=Laura |last17=Kosior |first17=Edward |last18=Favoino |first18=Enzo |last19=Gutberlet |first19=Jutta |last20=Baulch |first20=Sarah |last21=Atreya |first21=Meera E. |last22=Fischer |first22=David |last23=He |first23=Kevin K. |last24=Petit |first24=Milan M. |last25=Sumaila |first25=U. Rashid |last26=Neil |first26=Emily |last27=Bernhofen |first27=Mark V. |last28=Lawrence |first28=Keith |last29=Palardy |first29=James E. |title=Evaluating scenarios toward zero plastic pollution |journal=] |date=2020-09-18 |volume=369 |issue=6510 |pages=1455–1461 |doi=10.1126/science.aba9475|pmid=32703909 |bibcode=2020Sci...369.1455L |hdl=10026.1/16767 |s2cid=221767531 |url=http://arodes.hes-so.ch/record/5725 |hdl-access=free }}</ref>
===HDPE===
Plastic #2, high-density polyethylene (]) is a commonly recycled plastic. HDPE's highly crystalline structure makes it a strong, high density, moderately stiff plastic. HDPE Thermoplastic materials become liquid at their melting point—around 130&nbsp;°C. A major benefit of thermoplastics is that they can be heated to melting point, cooled, and reheated again without significant degradation. Instead of burning, thermoplastics like PE (Polyethylene) liquefy, allowing them to be easily extruded or ] and turned into brand new ]. Often it is typically ] into ], tables, roadside curbs, benches, truck cargo liners, trash receptacles, stationery (e.g. rulers) and other durable plastic products and is usually in demand.<ref>{{cite web|url=http://polywaste.com.au/|title=Poly Waste HDPE Recycling Website|date=|website=|access-date=}}</ref>


Recycling rates vary among types of plastic. Several types are in common use, each with distinct chemical and physical properties. This affects sorting and reprocessing costs; which affects the value and market size for recovered materials.<ref>{{cite news |title=Why plastic recycling is so confusing |url=https://www.bbc.co.uk/news/science-environment-45496884 |access-date=6 August 2021 |work=BBC News |date=18 December 2018}}</ref> ] and ] have the highest recycling rates, whereas ] and ] are rarely recycled.<ref>{{cite web |title=Advancing Sustainable Materials Management: 2018 Tables and Figures |url=https://www.epa.gov/sites/default/files/2021-01/documents/2018_tables_and_figures_dec_2020_fnl_508.pdf |publisher=US_EPA |access-date=9 November 2021}}</ref>
===PS===
] character is U+2678, which will appear here if you have a suitable font installed: <span style="font-size:250%;">♸</span>.-->]]


One of the reasons for low levels of plastic recycling is weak demand, given the materials' poor/inconsistent properties.<ref name=EU-demand>{{CELEX|52018DC0028|format=HTML|text=Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions – A European Strategy for Plastics in a Circular Economy, COM(2018) 28 final, 6 January 2018}}</ref> The percentage of plastic that can be fully recycled, rather than ] or go to waste, can be increased when manufacturers minimise mixing of packaging materials and eliminate contaminants. The Association of Plastics Recyclers has issued a "Design Guide for Recyclability".<ref>{{Cite web |title=The Association of Plastics Recyclers {{!}} APR Design® Guide |url=https://plasticsrecycling.org/apr-design-guide |access-date=2023-02-24 |website=The Association of Plastic Recyclers |language=en-gb}}</ref>
Most polystyrene products are not recycled due to the lack of incentive to invest in the compactors and logistical systems required. As a result, manufacturers cannot obtain sufficient scrap. Expanded polystyrene (EPS) scrap can easily be added to products such as EPS insulation sheets and other EPS materials for construction applications. When it is not used to make more EPS, foam scrap can be turned into clothes hangers, park benches, flower pots, toys, rulers, stapler bodies, seedling containers, picture frames, and architectural molding from recycled PS.<ref>{{cite web|url=http://pspc.intoweb.co.za/index.php?page=recycle1|title="Polystyrene recycling". Polystyrene Packaging Council. Retrieved 6 March 2009.|date=|website=Intoweb.co.za|access-date=13 July 2017}}{{Dead link|date=April 2019 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>


The most commonly produced plastic consumer products include packaging made from ] (e.g. bags, containers, ] film), containers made from ] (e.g. milk bottles, shampoo bottles, ice cream tubs), and ] (e.g. bottles for water and other drinks). Together these products account for around 36% of plastic production. The use of plastics in building and construction, textiles, transportation and electrical equipment accounts for another substantial share of the plastics market.<ref name=":0">{{Cite web |last=Environment |first=U. N. |date=2021-10-21 |title=Drowning in Plastics – Marine Litter and Plastic Waste Vital Graphics |url=http://www.unep.org/resources/report/drowning-plastics-marine-litter-and-plastic-waste-vital-graphics |access-date=2022-03-21 |website=UNEP - UN Environment Programme |language=en}}</ref>
Recycled EPS is also used in many metal casting operations. ] is made from EPS that is combined with cement to be used as an insulating amendment in the making of concrete foundations and walls. Since 1993, American manufacturers have produced insulating concrete forms made with approximately 80% recycled EPS.{{Citation needed|date=July 2017}}


===Other plastics=== ===Regional data===
Plastic consumption differs among countries and communities, although it is found almost everywhere. As of 2022 North American countries (]) accounted for 21% of global plastic consumption, closely followed by China (20%) and Western Europe (18%). In North America and Europe per capita plastic consumption was 94&nbsp;kg and 85&nbsp;kg/capita/year, respectively. China reached 58&nbsp;kg/capita/year.<ref name=":0" />
The white plastic polystyrene ]s used as packing material are often accepted by shipping stores for reuse.<ref>{{cite web|url=http://www.allbusiness.com/consumer-products/office-supplies-equipment/6916130-1.html |title=Let Peanuts Live! Mail Boxes Etc. Recycles as Part of National Effort; Recycle Loose-fill, Foam 'Peanuts' At Participating Mail Boxes Etc. Locations |publisher=AllBusiness.com |date= |access-date=21 August 2010}}</ref>


In 2012, 25.2 Mt of post-consumer plastic waste was collected in the European Union. Of this, more than 60% (15.6 Mt) was recovered and 40% (9.6 Mt) was disposed of as municipal solid waste (MSW). Of the 15.6 Mt of recovered plastic waste, about 6.6 Mt was recycled, while the remainder was likely used as refuse-derived fuel (RDF) or incinerated in MSW incinerators with energy recovery (about 9 Mt). Europe leads in plastics recycling, reusing about 26%.<ref>{{Citation |last1=Shen |first1=Li |title=Plastic Recycling |date=2014 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780123964595000131 |work=Handbook of Recycling |pages=179–190 |publisher=Elsevier |language=en |doi=10.1016/b978-0-12-396459-5.00013-1 |isbn=978-0-12-396459-5 |access-date=2022-11-13 |last2=Worrell |first2=Ernst}}</ref>
Successful trials in ] have shown that plastic films recovered from mixed municipal waste streams can be recycled into useful household products such as ]s.<ref>{{cite web|url=http://www.oaktech-environmental.com/plastictrials.htm|title="Plastic trial procedure". Oaktech Environmental website.|date=|website=Oaktech-Environmental.com|access-date=13 July 2017}}</ref>


The recycling activities of the largest producers of plastic waste have the greatest effect on global averages. These are a mix of advanced economies and large developing nations. Some publish official statistics on their plastic recycling rates. Others may release partial data, usually limited to population centres. This makes it difficult to draw accurate comparisons, especially as the published recycling rates vary.
Similarly, ] such as mulch film, ] and ] bags are being diverted from the waste stream and successfully recycled<ref>{{cite web|url=http://www.rkoindustries.com/id26.html|title="Agricultural plastics recycling process". Agricultural plastics recycling website.|date=|website=RKOIndustries.com|access-date=13 July 2017}}</ref> into much larger products for industrial applications such as ].<ref>{{cite web|url=http://www.rti-railroad-tie.com/id5.html|title="Plastic Composite Railroad Tie Facts". Plastic Composite Railroad Ties website.|date=|website=RTI-Railroad-Tie.com|access-date=13 July 2017}}</ref> Historically, these agricultural plastics have primarily been either landfilled or burned on-site in the fields of individual farms.<ref>{{cite web|url=http://environmentalrisk.cornell.edu/AgPlastics/References/Garthe&Kowal-a.pdf|title="Recycling Used Agricultural Plastics". James W. Garthe, Paula D. Kowal, PennState University, Agricultural and Biological Engineering|date=|website=Cornell.edu|access-date=13 July 2017}}</ref>


{| class="wikitable sortable" style="text-align: center; width: 950px"
] reports that Dr. S. Madhu of the ] Highway Research Institute, ], has formulated a road surface that includes recycled plastic: aggregate, ] (asphalt) with plastic that has been shredded and melted at a temperature below 220&nbsp;°C (428&nbsp;°F) to avoid pollution. This road surface is claimed to be very durable and monsoon rain resistant. The plastic is sorted by hand, which is economical in India. The test road used 60&nbsp;kg of plastic for an approximately 500-meter-long, 8-meter-wide, two-lane road. The process chops thin-film road-waste into a light fluff of tiny flakes that hot-mix plants can uniformly introduce into viscous bitumen with a customized dosing machine. Tests at both Bangalore and the Indian Road Research Centre indicate that roads built using this 'KK process' will have longer useful lives and better resistance to cold, heat, cracking, and rutting, by a factor of 3.<ref name=ISEBIndia>{{citation|title=Plastics Recycling and The Need For Bio-Polymers |last=Patel |first=Almitra H. |agency= International Society of Environmental Botanists |publisher= EnviroNews Archives |volume=9 |number=4 |date=October 2003 |url= http://isebindia.com/01_04/03-10-2.html}}</ref>
|+ 12 largest producers of plastic waste (+EU) and their recycling rates in 2010
|-
! Country
! Plastic waste per year (Mt)<ref name=OWID>{{cite journal |last1=Ritchie |first1=Hannah |author1-link=Hannah Ritchie |last2=Roser |first2=Max |author2-link=Max Roser |title=Plastic Pollution |url=https://ourworldindata.org/plastic-pollution |journal=Our World in Data |access-date=22 September 2021 |date=1 September 2018}}</ref>
! Waste per person per day (Kg)<ref name=OWID/>
! Recycled
! Incinerated <small>(with energy recovery)</small>
! Landfill <small>(and incineration without energy recovery)</small>
! Comments
|-
| China || 59.08 || 0.12 || - || - || - || No official statistics
|-
| United States<ref>{{cite web |last1=US EPA |first1=OLEM |title=Plastics: Material-Specific Data |url=https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling/plastics-material-specific-data |website=www.epa.gov |access-date=22 September 2021 |language=en |date=12 September 2017}}</ref> || 37.83 || 0.34 || 8% || 14% || 78% || Source: EPA
|-
| ''EU total*''<ref name=PE2011>{{cite web |title=Plastics facts 2011 |url=https://www.plasticseurope.org/en/resources/publications/115-plastics-facts-2011 |website=www.plasticseurope.org|date=2 June 2023 }}</ref> || 24.7 || 0.15 || 24% || 34% || 42% ||
|-
| Germany<ref name=PE2011/> || 14.48 || 0.48 || 33% || 65% || 2% ||
|-
| Brazil || 11.85 || 0.17 || - || - || - || No official statistics
|-
| Japan<ref>{{cite web |title=An Introduction to Plastic Recycling |url=https://www.pwmi.or.jp/ei/plastic_recycling_2019.pdf |publisher=Plastic Waste Management Institute |access-date=22 September 2021}}</ref> || 7.99 || 0.17 || 27% || 49% || 24% ||
|-
| Pakistan || 6.41 || 0.10 || - || - || - || No official statistics
|-
| Nigeria || 5.96 || 0.10 || 12% || 0% || 88% || Estimated values
|-
| Russia || 5.84|| 0.11 || 6% || 0% || 94% || <small>World bank estimates (2013)</small><ref>{{cite web |title=Waste in Russia: Garbage of valuable resource? |url=https://www.ifc.org/wps/wcm/connect/region__ext_content/ifc_external_corporate_site/europe+and+central+asia/resources/publicationrussiawaste2014-4-eng |website=www.ifc.org |language=en}}</ref>
|-
| Turkey || 5.60|| 0.21 || 5% || 0% || 95% || Estimated values
|-
| Egypt || 5.46|| 0.18 || - || - || - || No official statistics
|-
| Indonesia || 5.05|| 0.06 || 19% || 0% || 81% || Estimated values
|-
| United Kingdom<ref name=PE2011/> || 4.93|| 0.21 || 23% || 8% || 69% ||
|-
| Spain<ref name=PE2011/> || 4.71 || 0.28 || 23% || 17% || 60% ||
|-
| France<ref name=PE2011/> || 4.56 || 0.19 || 18% || 40% || 42% ||
|-
| India || 4.49 || 0.01 || 42% || 18% || 40% || Estimated values
|-
| '''Rest of World''' || 60.76 || - || - || - || - || No official statistics
|-
| '''World Total'''<ref name="Geyer2017" /> || 245.00 || 0.10 || 16% || 22% || 62% ||
|}
<small>* Although not formally a country, legislation affecting recycling is often made at the EU level</small>


==Identification codes==
Some new innovations propose plastics much easier recycled, like 2019 ]s. (PDK)<ref> Ars Technica, 2019</ref>
]


{{main|Resin identification code}}
== Equipment vendors ==
Major plastic recycling equipment companies include ].<ref>{{Cite web|url=https://resource-recycling.com/recycling/2019/08/27/tomra-ceo-industry-has-an-opportunity-for-greater-value-recovery/|title=Tomra CEO: Industry has an opportunity for greater value recovery|date=2019-08-27|website=Resource Recycling News|language=en-US|access-date=2019-09-05}}</ref> Equipment such as shredders and granulators may be sold by a variety of companies.<ref>{{Cite web|url=https://www.plasticsmachinerymagazine.com/blow-molding/article/13000549/standalone-integrated-granulator-systems-open-up-options-for-processors|title=Stand-alone, integrated granulator systems open up options for processors|website=www.plasticsmachinerymagazine.com|language=en|access-date=2019-09-05}}</ref>

In 2016, startup ] created a marketplace called Bazar for selling machines and products targeted to DIY designers to recycle plastic.<ref>{{Cite web|url=https://www.fastcompany.com/40486883/these-diy-machines-let-anyone-recycle-plastic-into-new-products|title=These DIY Machines Let Anyone Recycle Plastic Into New Products|last=Peters|first=Adele|date=2017-10-30|website=Fast Company|language=en-US|access-date=2019-09-05}}</ref>

==Recycling rates==
The quantity of post-consumer plastics recycled has increased every year since at least 1990, but rates lag far behind those of other items, such as newspaper (about 80%) and ] (about 70%).<ref>The Self-Sufficiency Handbook: A Complete Guide to Greener Living by Alan Bridgewater pg. 62—Skyhorse Publishing Inc., 2007 {{ISBN|1-60239-163-7}}, {{ISBN|978-1-60239-163-5}}</ref> Overall, U.S. post-consumer ] for 2008 was estimated at 33.6 million tons; 2.2 million tons (6.5%) were recycled and 2.6 million tons (8%) were burned for energy; 28.9 million tons, or 86%, were discarded in landfills.<ref>
{{cite news|url=http://journalistsresource.org/studies/environment/energy/energy-non-recycled-plastics-landfill/|title="Energy and Economic Value of Non-recycled Plastics and Municipal Solid Wastes" at Journalist's Resource.org}}</ref>


Many plastic items bear symbols identifying the type of ] from which they are made. These resin identification codes (RIC), are used internationally.<ref name="ASTM">{{cite web|title=Standard Practice for Coding Plastic Manufactured Articles for Resin Identification|url=http://www.astm.org/Standards/D7611.htm|website=Standard Practice for Coding Plastic Manufactured Articles for Resin Identification|publisher=ASTM International|access-date=21 January 2016}}</ref> They were developed in 1988 by the Society of the Plastics Industry (now the ]) in the United States, but since 2008 have been administered by ] ].<ref name="ASTM" />
As of 2015, approximately 6.3 billion tons of plastic waste had been generated, around 9% of which had been recycled, 12% was incinerated, and 79% was accumulated in landfills or the natural environment.<ref>{{cite journal|url=http://advances.sciencemag.org/content/3/7/e1700782|title=Science Advances|volume=3|issue=7|pages=e1700782|last=Geyer|first=Roland|date=19 July 2017|website=|access-date=|doi=10.1126/sciadv.1700782|pmid=28776036|pmc=5517107}}</ref> In 2016 only 14% of plastic waste was recycled globally.<ref>{{cite web|url=https://www.ellenmacarthurfoundation.org/news/the-new-plastics-economy-rethinking-the-future-of-plastics-infographics|title=The new plastic economy rethinking the future of plastics|last=Ellen MacArthur Foundation|date=19 January 2016|website=|access-date=}}</ref> According to the EPA, the recycling rate for plastics overall was 9.1% in 2015. Certain products have higher rates, such as PET bottles and jars at 29.9%, and HDPE natural bottles at 30.3%. These rates are lower than certain other materials, like steel cans, that had an estimated recycling rate of 71.3% in 2015.<ref> EPA. Retrieved 2019-06-26.</ref><ref> EPA. Retrieved 2016-06-26.</ref>


RICs are not mandatory in all countries, but many producers voluntarily mark their products. More than half of U.S. states have enacted laws that require plastic products be identifiable.<ref>{{cite book|title=Holt Chemistry|publisher=]|year=2006|isbn=978-0-03-039114-9|chapter=19|page=702|quote=More than half the states in the United States have enacted laws that require plastic products to be labelled with numerical codes that identify the type of plastic used in them.|title-link=Florida|edition=Florida}}</ref> The seven codes include six for the most common ] and one as a catch-all. The EU maintains a similar nine-code list that also includes ] and ].<ref name="97/129/EC">Official Journal of the EC; establishing the ID system for packaging materials pursuant to European Parliament & Council Directive 94/62/EC</ref> RICs are based on the ], but have drawn criticism, as they imply that marked items are always recyclable when this may not be true.<ref name=":5">{{Cite web|last=Petsko|first=Emily|title=Recycling Myth of the Month: Those numbered symbols on single-use plastics do not mean 'you can recycle me'|url=https://oceana.org/blog/recycling-myth-month-those-numbered-symbols-single-use-plastics-do-not-mean-you-can-recycle-me|access-date=12 October 2020|website=]|date=11 March 2020|language=en}}</ref>
Japan's plastic waste utilization rate stood at 39% in 1996, increasing to 73% in 2006, 77% in 2011,<ref>{{Cite news | url=https://www.theguardian.com/environment/2011/dec/29/japan-leads-field-plastic-recycling | title=Japan streets ahead in global plastic recycling race| newspaper=The Guardian| date=2011-12-29| last1=McCurry| first1=Justin}}</ref> 83% in 2014<ref>{{cite web|url=http://www.pwmi.or.jp/ei/index.htm |title=一般社団法人プラスチック循環利用協会 |publisher=Pwmi.or.jp |date= |accessdate=2019-01-29}}</ref> and 86% in 2017, according to the nation's Plastic Waste Management Institute.<ref>http://www.pwmi.or.jp/ei/siryo/ei/ei_pdf/ei48.pdf</ref>


RICs are not particularly important for ], as these operations are increasingly automated. However, in some countries citizens are required to separate their plastic waste according to polymer type before collection. For instance, in Japan PET bottles are collected separately for recycling.
==Economic and energy potential==
{{Update|type=section|date=December 2018|reason=Impacts of "National Sword Policy" on commodity prices}}
In 2008, the price of PET dropped from $370/ton in the US to $20 in November.<ref>Page, Candace, Waste district raises recycling fees, ''Burlington Free Press'', November 12, 2008</ref> PET prices had returned to their long-term averages by May 2009.<ref>''Financial Times'', May 15, 2009 (article by Max Hogg)</ref>

==Plastic identification code==
{{main|Resin identification code}}
Seven groups of plastic polymers,<ref name="singapore">{{cite web|url=https://recyclemonthly.com/blogs/topsecret/recycling-tips-3-how-to-recycle-the-7-types-of-plastic-used-for-packaging|title=How to Recycle the 7 types of plastic used for packaging.|date=|website=RecycleMonthly|access-date=}}</ref> each with specific properties, are used worldwide for packaging applications (see table below). Each group of plastic polymer can be identified by its plastic identification code (PIC), usually a number or a letter abbreviation. For instance, low-density polyethylene can be identified by the number "4" or the letters "LDPE". The PIC appears inside a three-chasing-arrow recycling symbol. The symbol is used to indicate whether the plastic can be recycled into new products.{{citation needed|date=September 2011}}

The PIC was introduced by the Society of the Plastics Industry, Inc., to provide a uniform system for the identification of various polymer types and to help recycling companies separate various plastics for reprocessing. Manufacturers of plastic products are required to use PIC labels in some countries/regions and can voluntarily mark their products with the PIC where there are no requirements.<ref>{{cite book|title=Holt Chemistry (Florida edition)|publisher=]|year=2006|isbn=978-0-03-039114-9|chapter=19|page=702|quote=More than half the states in the United States have enacted laws that require plastic products to be labeled with numerical codes that identify the type of plastic used in them.|title-link=Florida}}</ref> Consumers can identify the plastic types based on the codes usually found at the base or at the side of the plastic products, including food/chemical packaging and containers. The PIC is usually not present on packaging films, since it is not practical to collect and recycle most of this type of waste.{{clarify|date=September 2011}}{{citation needed|date=September 2011}}


{{clear}}
{| class="wikitable" {| class="wikitable"
|- |-
Line 132: Line 142:
! Type of plastic polymer ! Type of plastic polymer
! Properties ! Properties
! Common packaging applications ! Common applications
! ] and ] temperatures (°C) ! ] and ] temperatures (°C)
! Young's modulus (GPa) ! Young's modulus (GPa)
|- |-
| <center>]</center> | ]
| ] (PET, PETE) | Polyethylene terephthalate (PET)
| Clarity, strength, toughness, barrier to gas and moisture. | Clarity, strength, toughness, barrier to gas and moisture
| Soft drink, water and salad dressing bottles; peanut butter and jam jars; ice cream cone lids; small consumer electronics | Soft drink, water and salad dressing bottles; peanut butter and jam jars; ice cream cone lids; small non-industrial electronics
| Tm = 250;<ref name="polymerprocessing.com">{{cite web|url=http://www.polymerprocessing.com/polymers/PET.html|title=poly(ethylene terephthalate) information and properties|first=Chris|last=Scott|date=|website=www.PolymerProcessing.com|access-date=13 July 2017}}</ref> Tg = 76<ref name="polymerprocessing.com"/> | T<sub>m</sub> = 250;<ref name="polymerprocessing.com">{{cite web|url=http://www.polymerprocessing.com/polymers/PET.html|title=poly(ethylene terephthalate) information and properties|first=Chris|last=Scott|website=PolymerProcessing.com|access-date=13 July 2017}}</ref> <br>T<sub>g</sub> = 76<ref name="polymerprocessing.com"/>
| 2–2.7<ref name="engineeringtoolbox.com">{{cite web|url=http://www.engineeringtoolbox.com/young-modulus-d_417.html|title=Modulus of Elasticity or Young's Modulus – and Tensile Modulus for common Materials|date=|website=www.EngineeringToolbox.com|access-date=13 July 2017}}</ref> | 2–2.7<ref name="engineeringtoolbox.com">{{cite web|url=http://www.engineeringtoolbox.com/young-modulus-d_417.html|title=Modulus of Elasticity or Young's Modulus – and Tensile Modulus for common Materials|website=EngineeringToolbox.com|access-date=13 July 2017}}</ref>
|- |-
| <center>]</center> | ]
| ] (HDPE) | ] (HDPE)
| Stiffness, strength, toughness, resistance to moisture, permeability to gas | Stiffness, strength, toughness, barrier to gas and moisture
|, , Electrical & Communications conduit,<ref>{{cite web|url=http://polywaste.com.au/|title=Poly Waste Website|archive-url=https://web.archive.org/web/20180904122451/http://polywaste.com.au/|archive-date=2018-09-04|url-status=dead}}</ref> ] rings, ]s, milk, juice and water bottles; grocery bags, some shampoo/toiletry bottles |Water pipes, gas and fire pipelines, electrical and communications conduits, ]s, milk, juice and water bottles, grocery bags, some toiletry bottles
| Tm = 130;<ref>{{cite web|url=http://www.dynalabcorp.com/technical_info_hd_polyethylene.asp|title=Dyna Lab Corp|website=DynaLabCorp.com|access-date=13 July 2017|url-status=dead|archiveurl=https://web.archive.org/web/20101122081958/http://dynalabcorp.com/technical_info_hd_polyethylene.asp|archivedate=22 November 2010}}</ref> Tg = −125<ref name="sigmaaldrich.com">{{cite web|url=http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/General_Information/thermal_transitions_of_homopolymers.Par.0001.File.tmp/thermal_transitions_of_homopolymers.pdf|title=Sigma Aldrich|date=|website=SigmaAldrich.com|access-date=13 July 2017}}</ref> | T<sub>m</sub> = 130;<ref>{{cite web|url=http://www.dynalabcorp.com/technical_info_hd_polyethylene.asp|title=Dyna Lab Corp|website=DynaLabCorp.com|access-date=13 July 2017|url-status=dead|archive-url=https://web.archive.org/web/20101122081958/http://dynalabcorp.com/technical_info_hd_polyethylene.asp|archive-date=22 November 2010}}</ref> <br>T<sub>g</sub> = −125<ref name="sigmaaldrich.com">{{cite web |url=http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/General_Information/thermal_transitions_of_homopolymers.Par.0001.File.tmp/thermal_transitions_of_homopolymers.pdf |url-status=dead |archive-url=https://web.archive.org/web/20120315144951/https://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/General_Information/thermal_transitions_of_homopolymers.Par.0001.File.tmp/thermal_transitions_of_homopolymers.pdf |archive-date=15 March 2012 |title=Sigma Aldrich |website=] |access-date=2 September 2024}}{{cbignore}}</ref>
| 0.8<ref name="engineeringtoolbox.com"/> | 0.8<ref name="engineeringtoolbox.com"/>
|- |-
| <center>]</center> | ]
| ] (PVC) | ] (PVC)
| Versatility, ease of blending, strength, toughness. | Versatility, ease of blending, strength, toughness.
| Blister packaging for non-food items; cling films for non-food use. May be used for food packaging with the addition of the plasticisers needed to make natively rigid PVC flexible. Non-packaging uses are electrical cable insulation; rigid piping; vinyl records. | ] for non-food items, sometimes ]. Non-packaging uses include electrical cable insulation, rigid piping and vinyl records.
| Tm = 240;<ref name="ReferenceA">{{cite web|url=http://www.polymerprocessing.com/polymers/PVC.html|title=poly(vinyl chloride) information and properties|first=Chris|last=Scott|date=|website=www.PolymerProcessing.com|access-date=13 July 2017}}</ref> Tg = 85<ref name="ReferenceA"/> | T<sub>m</sub> = 240;<ref name="ReferenceA">{{cite web|url=http://www.polymerprocessing.com/polymers/PVC.html|title=poly(vinyl chloride) information and properties|first=Chris|last=Scott|website=PolymerProcessing.com|access-date=13 July 2017}}</ref> <br>T<sub>g</sub> = 85<ref name="ReferenceA"/>
| 2.4–4.1<ref name="ReferenceB">''Modern Plastics Encyclopedia'' 1999, p B158 to B216. (Tensile modulus)</ref> | 2.4–4.1<ref name="ReferenceB">''Modern Plastics Encyclopedia'' 1999, p B158 to B216. (Tensile modulus)</ref>
|- |-
| <center>]</center> | ]
| ] (LDPE) | ] (LDPE)
| Ease of processing, strength, toughness, flexibility, ease of sealing, barrier to moisture. | Ease of processing; strength; flexibility; ease of sealing; moisture barrier.
| Frozen food bags; squeezable bottles, e.g. honey, mustard; cling films; flexible container lids | Frozen food bags; squeezable bottles, e.g. honey, mustard; cling films; flexible container lids
| Tm = 120;<ref>{{cite web|url=http://www.dynalabcorp.com/technical_info_ld_polyethylene.asp|title=Dyna Lab Corp|website=DynaLabCorp.com|access-date=13 July 2017|url-status=dead|archiveurl=https://web.archive.org/web/20110921105219/http://www.dynalabcorp.com/technical_info_ld_polyethylene.asp|archivedate=21 September 2011}}</ref> Tg = −125<ref>{{cite web|url=http://www.lasalle.edu/academ/chem/ms/polymersRus/Resources/GlassTrans.htm|title=Wofford University|website=LaSalle.edu|access-date=13 July 2017|url-status=dead|archiveurl=https://web.archive.org/web/20100111055937/http://www.lasalle.edu/academ/chem/ms/polymersRus/Resources/GlassTrans.htm|archivedate=11 January 2010}}</ref> | T<sub>m</sub> = 120;<ref>{{cite web|url=http://www.dynalabcorp.com/technical_info_ld_polyethylene.asp|title=Dyna Lab Corp|website=DynaLabCorp.com|access-date=13 July 2017|url-status=dead|archive-url=https://web.archive.org/web/20110921105219/http://www.dynalabcorp.com/technical_info_ld_polyethylene.asp|archive-date=21 September 2011}}</ref> <br>T<sub>g</sub> = −125<ref>{{cite web|url=http://www.lasalle.edu/academ/chem/ms/polymersRus/Resources/GlassTrans.htm|title=Wofford University|website=LaSalle.edu|access-date=13 July 2017|url-status=dead|archive-url=https://web.archive.org/web/20100111055937/http://www.lasalle.edu/academ/chem/ms/polymersRus/Resources/GlassTrans.htm|archive-date=11 January 2010}}</ref>
| 0.17–0.28<ref name="ReferenceB"/> | 0.17–0.28<ref name="ReferenceB"/>
|- |-
| <center>]</center> | ]
| ] (PP) | ] (PP)
| Strength, toughness, resistance to heat, chemicals, grease and oil, versatile, barrier to moisture. | Strength; resistance to heat, chemicals, grease and oil; moisture barrier.
| Reusable microwaveable ware; kitchenware; yogurt containers; margarine tubs; microwaveable ] ] containers; disposable cups; soft drink ]s; plates. | Reusable microwaveable ware or take-away containers; kitchenware; yogurt or margarine containers; ]s; soft drink ]s.
| Tm = 173;<ref name="ReferenceC">{{cite web|url=http://www.polymerprocessing.com/polymers/PP.html|title=polypropylene information and properties|first=Chris|last=Scott|date=|website=www.PolymerProcessing.com|access-date=13 July 2017}}</ref> Tg = −10<ref name="ReferenceC"/> | T<sub>m</sub> = 173;<ref name="ReferenceC">{{cite web|url=http://www.polymerprocessing.com/polymers/PP.html|title=polypropylene information and properties|first=Chris|last=Scott|website=PolymerProcessing.com|access-date=13 July 2017}}</ref> <br>T<sub>g</sub> = −10<ref name="ReferenceC"/>
| 1.5–2<ref name="engineeringtoolbox.com"/> | 1.5–2<ref name="engineeringtoolbox.com"/>
|- |-
| <center>]</center> | ]
| ] (PS) | ] (PS)
| Versatility, clarity, easily formed | Versatility, clarity, easily formed, easily foamed
| Egg cartons; packing peanuts; disposable cups, plates, trays and cutlery; disposable take-away containers | Egg cartons; disposable cups, plates, trays and cutlery; ]s; ] and ];
| Tm = 240 (only isotactic);<ref name="sigmaaldrich.com"/> Tg = 100 (atactic and isotactic)<ref name="sigmaaldrich.com"/> | T<sub>m</sub> = 240 (only isotactic);<ref name="sigmaaldrich.com"/> <br>T<sub>g</sub> = 100 (atactic and isotactic)<ref name="sigmaaldrich.com"/>
| 3–3.5<ref name="engineeringtoolbox.com"/> | 3–3.5<ref name="engineeringtoolbox.com"/>
|- |-
| <center>]</center> | ]
| Other (often ] or ]) | Other (often ] or ])
| Dependent on polymers or combination of polymers | Dependent on polymers or combination of polymers
| Beverage bottles, baby milk bottles. Non-packaging uses for polycarbonate, compact discs, "unbreakable" glazing, electronic apparatus housing, lenses (including sunglasses), prescription glasses, automotive headlamps, riot shields, instrument panels.<ref>{{cite web | title=What is Polycarbonate (PC)? | url=http://www.recycledplastic.com/resource/plastic/polycarbonate-pc/ | access-date=}}</ref> | Beverage bottles, baby milk bottles. Non-packaging uses for polycarbonate: compact discs, "unbreakable" glazing, electronic apparatus housing, lenses (including sunglasses), instrument panels.<ref>{{cite web | title=What is Polycarbonate (PC)? | url=http://www.recycledplastic.com/resource/plastic/polycarbonate-pc/ }}</ref>
|Polycarbonate: Tg = 145;<ref>{{cite web|url=http://www.polymerprocessing.com/polymers/PC.html |title=polycarbonate information and properties |publisher=PolymerProcessing.com |date=15 April 2001 |access-date=27 October 2012}}</ref> Tm = 225<ref>{{cite web|url=http://www.polymerprocessing.com/polymers/PC.html|title=polycarbonate information and properties|first=Chris|last=Scott|date=|website=www.PolymerProcessing.com|access-date=13 July 2017}}</ref> |Polycarbonate:<br>T<sub>m</sub> = 225<ref>{{cite web|url=http://www.polymerprocessing.com/polymers/PC.html|title=polycarbonate information and properties|first=Chris|last=Scott|website=PolymerProcessing.com|access-date=13 July 2017}}</ref><br>T<sub>g</sub> = 145;<ref>{{cite web|url=http://www.polymerprocessing.com/polymers/PC.html |title=polycarbonate information and properties |publisher=PolymerProcessing.com |date=15 April 2001 |access-date=27 October 2012}}</ref>
|Polycarbonate: 2.6;<ref name="engineeringtoolbox.com"/> ABS plastics: 2.3<ref name="engineeringtoolbox.com"/> |Polycarbonate: 2.6;<ref name="engineeringtoolbox.com"/> ABS plastics: 2.3<ref name="engineeringtoolbox.com"/>
|} |}


===Asia and Africa=== ==Waste composition==
Plastic waste consists of various polymer types.<ref name="Geyer2017" /><ref name="Geyer2020">{{cite book |last1=Geyer |first1=Roland |title=Plastic waste and recycling : environmental impact, societal issues, prevention, and solutions |date=2020 |publisher=Academic Press |location=Amsterdam |isbn=978-0-12-817880-5 |page=22}}</ref> ]s make up nearly 50% of all plastic waste and more than 90% of waste is made of ] polymers, which can be remelted
The ] reported that China, Indonesia, Philippines, Thailand, and Vietnam dump more plastic in the sea than all other countries combined.<ref>{{cite news |last1=Hannah Leung |title=Five Asian Countries Dump More Plastic Into Oceans Than Anyone Else Combined: How You Can Help |url=https://www.forbes.com/sites/hannahleung/2018/04/21/five-asian-countries-dump-more-plastic-than-anyone-else-combined-how-you-can-help/#1d663de71234 |accessdate=23 June 2019 |work=] |date=21 April 2018 |language=en |quote=China, Indonesia, Philippines, Thailand, and Vietnam are dumping more plastic into oceans than the rest of the world combined, according to a 2017 report by Ocean Conservancy}}</ref> ] reported that China dumps 30% of all plastics in the ocean, followed by Indonesia, the Philippines, Vietnam, Sri Lanka, Thailand, Egypt, Malaysia, Nigeria and Bangladesh.<ref>{{cite news |last1=Will Dunham |title=World's Oceans Clogged by Millions of Tons of Plastic Trash |url=https://www.scientificamerican.com/article/world-s-oceans-clogged-by-millions-of-tons-of-plastic-trash/ |accessdate=31 July 2019 |work=Scientific American |date=12 February 2019 |language=en |quote=China was responsible for the most ocean plastic pollution per year with an estimated 2.4 million tons, about 30 percent of the global total, followed by Indonesia, the Philippines, Vietnam, Sri Lanka, Thailand, Egypt, Malaysia, Nigeria and Bangladesh.}}</ref>


{{div flex row|align-items=center}}
===United States===
{{Graph:Chart
In 2015, the United States produced 34.5 million tons of plastic, which was about 13% of total waste.<ref name=":1">{{Cite web|url=https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling/national-overview-facts-and-figures-materials|title=National Overview: Facts and Figures on Materials, Wastes and Recycling|last=US EPA|first=OLEM|date=2017-10-02|website=US EPA|language=en|access-date=2019-09-05}}</ref> About 9% of that was recycled. Most of the waste stream is biodegradable but plastic though only 13% of the waste stream is persistent and accumulates.<ref name=":1" />
| width=110
| height=110
| type=pie
| legend=Letter
| x=HDPE,LDPE,PP,PS,PVC,PET,PUR,PP&A fibers,All Others
| y1=0.198,0.139,0.191,0.059,0.053,0.108,0.056,0.157,0.037
| showValues=format:.1%,offset:5
}}
{| class="wikitable sortable" style="width:55em; margin: 1em auto"
|+Global plastic waste by polymer type (2018)<ref name="Geyer2017" /><ref name="Geyer2020" />
|-
! Polymer !! Waste production (Mt) !! Percentage of all plastic waste !! Polymer type !! Thermal character
|-
|High-density polyethylene (HDPE) || 64 || 19.8% ||] || Thermoplastic
|-
|Low-density polyethylene (]) || 45 || 13.9% || Polyolefin || Thermoplastic
|-
|polypropylene (]) || 62 || 19.1% || Polyolefin || Thermoplastic
|-
|Polystyrene (]) || 19|| 5.9% || Unsaturated polyolefin || Thermoplastic
|-
|Polyvinyl chloride (]) || 17 || 5.3% || Halogenated || Thermoplastic
|-
|Polyethylene terephthalate (]) || 35 || 10.8% || Condensation || Thermoplastic
|-
|Polyurethane (]) || 18 || 5.6% || Condensation || Thermoset<ref>The majority of polyurethanes are thermosets, however some thermoplastics are also produced, for instance ]</ref>
|-
| PP&A fibers<ref name=PP&A>PP&A stand for ], ] and ]; all of which are used to make ]. Care should be taken not to confuse it with ] (PPA)</ref> || 51 || 15.7% || Condensation || Thermoplastic
|-
| All Others || 12 || 3.7% || Various || Varies
|-
| '''Total (excludes additives)''' || '''324''' || '''100%''' || - || -
|}
{{div flex row end}}


==Collecting and sorting==
Low national plastic recycling rates have been due to the complexity of sorting and processing, unfavorable economics, and consumer confusion about which plastics can actually be recycled.<ref>{{cite news | title=Where can we put all those plastics? |work=Seattle Times | url=http://seattletimes.nwsource.com/html/homegarden/2003730398_ecoconsumer02.html| access-date=2 June 2007 | first=Tom | last=Watson | date=June 2, 2007}}</ref> Part of the confusion has been due to the use of the ],<ref>{{cite web|url=http://www.americanchemistry.com/s_plastics/bin.asp?CID=1102&DID=4645&DOC=FILE.PDF|title=Page Not Found|website=www.AmericanChemistry.com|access-date=13 July 2017|url-status=dead|archiveurl=https://web.archive.org/web/20110721103005/http://www.americanchemistry.com/s_plastics/bin.asp?CID=1102&DID=4645&DOC=FILE.PDF|archivedate=21 July 2011}}</ref> which is only found on a subset of plastic products,<ref>{{cite web|url=http://www.plasticsindustry.org/AboutPlastics/content.cfm?ItemNumber=823|title=SPI Resin Identification Code – Guide to Correct Use|website=PlasticsIndustry.org|access-date=13 July 2017|url-status=dead|archiveurl=https://web.archive.org/web/20130516032146/http://www.plasticsindustry.org/AboutPlastics/content.cfm?ItemNumber=823|archivedate=16 May 2013}}</ref> and which includes the ] as part of its design. The resin identification code is stamped or printed on the bottom of containers and surrounded by a triangle of arrows. (See the table in ].) The intent of these symbols was to make it easier to identify the type of plastics used to make a particular container and to indicate that the plastic is potentially recyclable. The question that remains is which types of plastics can be recycled by local recycling centers. In many communities, not all types of plastics are accepted for sidewalk recycling collection programs due to the high processing costs and complexity of the equipment required to recycle certain materials. There is also sometimes a seemingly low demand for the recycled product depending on a recycling center's proximity to entities seeking recycled materials. Another major barrier is that the cost to recycle certain materials and the corresponding market price for those materials sometimes does not present any opportunity for profit. The best example of this is polystyrene (commonly called styrofoam), although some communities, like ], are moving toward banning the distribution of polystyrene containers by local food and coffee businesses.<ref></ref><ref>{{cite web|url=http://www.boston.com/yourtown/news/brookline/2012/11/brookline_town_meeting_bans_st.html|title=Brookline Town Meeting bans Styrofoam coffee, takeout containers|first=Brock|last=Parker|date=13 November 2012|website=Boston.com|access-date=13 July 2017}}</ref>
] (blues, clear and greens) Olomouc, the Czech Republic.]]
]
]

Recycling begins with the collection and sorting of waste. Curbside collection operates in many countries. Waste is sent to a ] or ] where the plastic is separated, cleaned and sorted for sale. Unsuitable materials are sent to a landfill or incinerator. These operations account for a large proportion of the financial and energy costs associated with recycling.

Sorting plastic is more complicated than other recyclable materials because it comes in a greater range of forms. For example, glass is separated into three streams (clear, green and amber), metals are usually either steel or aluminum and can be separated using magnets or ], and paper is usually sorted into a single stream.

Six types of ] account for about 75% of plastics waste, with the rest comprising a myriad of polymer types, including polyurethanes and ] with a range of chemical structures. Items made from the same type of polymer may be incompatible with each other depending on the additives they contain. ] are compounds blended into plastics to enhance performance and include ], ] and, most significantly, ].<ref name="Additive-rev">{{cite journal |last1=Hahladakis |first1=John N. |last2=Velis |first2=Costas A. |last3=Weber |first3=Roland |last4=Iacovidou |first4=Eleni |last5=Purnell |first5=Phil |title=An overview of chemical additives present in plastics: Migration, release, fate and environmental impact during their use, disposal and recycling |journal=Journal of Hazardous Materials |date=February 2018 |volume=344 |pages=179–199 |doi=10.1016/j.jhazmat.2017.10.014|pmid=29035713 |doi-access=free|bibcode=2018JHzM..344..179H }}</ref> Clear plastics hold the highest value as they may be dyed after recycling, while black or strongly coloured plastic is much less valuable, because they affect the color of the downstream product. Thus, plastic is typically sorted by both polymer type and colour.

Various sorting approaches and technologies have been developed.<ref name="Genrev" /> They can be combined in various ways.<ref name="Cimpan2016">{{cite journal |last1=Cimpan |first1=Ciprian |last2=Maul |first2=Anja |last3=Wenzel |first3=Henrik |last4=Pretz |first4=Thomas |title=Techno-economic assessment of central sorting at material recovery facilities – the case of lightweight packaging waste |journal=] |date=January 2016 |volume=112 |pages=4387–4397 |doi=10.1016/j.jclepro.2015.09.011|bibcode=2016JCPro.112.4387C }}</ref> In practice no approach is 100% effective.<ref>{{cite journal |last1=Faraca |first1=Giorgia |last2=Astrup |first2=Thomas |title=Plastic waste from recycling centres: Characterisation and evaluation of plastic recyclability |journal=Waste Management |date=July 2019 |volume=95 |pages=388–398 |doi=10.1016/j.wasman.2019.06.038|pmid=31351625 |bibcode=2019WaMan..95..388F |s2cid=198331405 }}</ref><ref>{{cite journal |last1=Antonopoulos |first1=Ioannis |last2=Faraca |first2=Giorgia |last3=Tonini |first3=Davide |title=Recycling of post-consumer plastic packaging waste in the EU: Recovery rates, material flows, and barriers |journal=Waste Management |date=May 2021 |volume=126 |pages=694–705 |doi=10.1016/j.wasman.2021.04.002|pmid=33887695 |pmc=8162419 |bibcode=2021WaMan.126..694A |doi-access=free}}</ref><ref name="Cimpan2016" /> Sorting accuracy varies between recyclers, producing a market where products are poorly standardised. This inconsistency is another barrier to recycling.

===Manual separation===
Sorting by hand is the oldest and simplest method. In developing countries this may be done by ]s, while in a recycling center, workers pick items off a conveyor-belt. It requires low levels of technology and investment, but has high labor costs. Although many plastic items have identification codes workers rarely have time to look for them, so leaving problems of inefficiency and inconsistency. Even advanced facilities retain manual pickers to troubleshoot and correct sorting errors.<ref name=Cimpan2016 /> Working conditions can be unsanitary.<ref>{{cite journal |last1=Poulsen |first1=Otto M. |last2=Breum |first2=Niels O. |last3=Ebbehøj |first3=Niels |last4=Hansen |first4=Åse Marie |last5=Ivens |first5=Ulla I. |last6=van Lelieveld |first6=Duco |last7=Malmros |first7=Per |last8=Matthiasen |first8=Leo |last9=Nielsen |first9=Birgitte H. |last10=Nielsen |first10=Eva Møller |last11=Schibye |first11=Bente |last12=Skov |first12=Torsten |last13=Stenbaek |first13=Eva I. |last14=Wilkins |first14=Ken C. |title=Sorting and recycling of domestic waste. Review of occupational health problems and their possible causes |journal=Science of the Total Environment |date=May 1995 |volume=168 |issue=1 |pages=33–56 |doi=10.1016/0048-9697(95)04521-2|pmid=7610383 |bibcode=1995ScTEn.168...33P }}</ref>

===Density separation===

{| class="wikitable floatright"
|+ Plastic densities<ref>{{cite journal |doi=10.1016/j.jglr.2014.12.020 |title=Plastic debris in the Laurentian Great Lakes: A review |journal=Journal of Great Lakes Research |volume=41 |pages=9–19 |year=2015 |last1=Driedger |first1=Alexander G.J. |last2=Dürr |first2=Hans H. |last3=Mitchell |first3=Kristen |last4=Van Cappellen |first4=Philippe|issue=1 |bibcode=2015JGLR...41....9D |doi-access=free |hdl=10012/11956 |hdl-access=free }}</ref>
|'''Plastic Type'''
|'''Density (g/cm<sup>3</sup>)'''
|-
|Polyvinyl chloride
|1.38-1.41
|-
|Polyethylene terephthalate
|1.38-1.41
|-
|Polystyrene
|1.04-1.08
|-
|High-density polyethylene
|0.94-0.98
|-
|Low-density polyethylene
|0.89–0.93
|-
|Polypropylene
|0.85-0.92
|-
|Polystyrene foam
|0.01-0.04
|}

Plastics can be separated by exploiting differences in their densities. In this approach the plastic is first ground into flakes of a similar size, washed and subjected to ].<ref name="flakes">{{cite journal |last1=Ragaert |first1=Kim |last2=Delva |first2=Laurens |last3=Van Geem |first3=Kevin |title=Mechanical and chemical recycling of solid plastic waste |journal=Waste Management |date=November 2017 |volume=69 |pages=24–58 |doi=10.1016/j.wasman.2017.07.044|pmid=28823699 |bibcode=2017WaMan..69...24R }}</ref> This can be achieved using either an ] or ], or via wet float-sink method.<ref>{{cite journal |last1=Bauer |first1=Markus |last2=Lehner |first2=Markus |last3=Schwabl |first3=Daniel |last4=Flachberger |first4=Helmut |last5=Kranzinger |first5=Lukas |last6=Pomberger |first6=Roland |last7=Hofer |first7=Wolfgang |title=Sink–float density separation of post-consumer plastics for feedstock recycling |journal=Journal of Material Cycles and Waste Management |date=July 2018 |volume=20 |issue=3 |pages=1781–1791 |doi=10.1007/s10163-018-0748-z |doi-access=free|bibcode=2018JMCWM..20.1781B }}</ref> These approaches provide partial sorting, as some polymers have similar density.<ref name=flakes /> Polypropylene (PP) and ] (PE) are similar as are polyethylene terephthalate (PET), polystyrene (PS), and ]. In addition, if the plastic contains ], this may affect its density.<ref>{{cite journal |last1=Bonifazi |first1=Giuseppe |last2=Di Maio |first2=Francesco |last3=Potenza |first3=Fabio |last4=Serranti |first4=Silvia |title=FT-IR Analysis and Hyperspectral Imaging Applied to Postconsumer Plastics Packaging Characterization and Sorting |journal=] |date=May 2016 |volume=16 |issue=10 |pages=3428–3434 |doi=10.1109/JSEN.2015.2449867|bibcode=2016ISenJ..16.3428B |s2cid=6670818 }}</ref> The lighter PP and PE fraction is known as mixed polyolefin (MPO) and can be sold as a low-value product,<ref>{{cite journal |last1=Hubo |first1=Sara |last2=Delva |first2=Laurens |last3=Van Damme |first3=Nicolas |last4=Ragaert |first4=Kim |title=Blending of recycled mixed polyolefins with recycled polypropylene: Effect on physical and mechanical properties |series=AIP Conference Proceedings |date=2016 |volume=1779 |pages=140006 |doi=10.1063/1.4965586|doi-access=free }}</ref> the heavier mixed plastics fraction is usually unrecyclable.

===Electrostatic separation===
{{main|electrostatic separator}}
In electrostatic separators, the ] is used to charge plastic particles electrically; with different polymers charged to different extents. They are then blown through an electric field, which deflects them depending on their charge, directing them into appropriate collectors. As with density separation, the particles need to be dry, be uniform in size and shape.<ref>{{cite journal |last1=Wu |first1=Guiqing |last2=Li |first2=Jia |last3=Xu |first3=Zhenming |title=Triboelectrostatic separation for granular plastic waste recycling: A review |journal=Waste Management |date=March 2013 |volume=33 |issue=3 |pages=585–597 |doi=10.1016/j.wasman.2012.10.014|pmid=23199793 |bibcode=2013WaMan..33..585W |s2cid=12323746 }}</ref> Electrostatic separation can be complementary to density separation, allowing full separation of polymers,<ref>{{cite journal |last1=Dodbiba |first1=G. |last2=Sadaki |first2=J. |last3=Okaya |first3=K. |last4=Shibayama |first4=A. |last5=Fujita |first5=T. |title=The use of air tabling and triboelectric separation for separating a mixture of three plastics |journal=Minerals Engineering |date=December 2005 |volume=18 |issue=15 |pages=1350–1360 |doi=10.1016/j.mineng.2005.02.015|bibcode=2005MiEng..18.1350D }}</ref> albeit of mixed colours.

===Sensor-based separation===
]
{{main|Sensor-based sorting}}

This approach is largely automated and involves various sensors linked to a computer, which analyses items and directs them into appropriate chutes or belts.<ref>{{cite journal |last1=Gundupalli |first1=Sathish Paulraj |last2=Hait |first2=Subrata |last3=Thakur |first3=Atul |title=A review on automated sorting of source-separated municipal solid waste for recycling |journal=Waste Management |date=February 2017 |volume=60 |pages=56–74 |doi=10.1016/j.wasman.2016.09.015|pmid=27663707 |bibcode=2017WaMan..60...56G }}</ref> ] can be used to distinguish polymer types,<ref>{{cite book |last1=Hollstein |first1=Frank |last2=Wohllebe |first2=Markus |last3=Arnaiz |first3=Sixto |title=Near Infrared Spectroscopy: Proceedings of the International Conference |chapter=Identification and Sorting of Plastics Film Waste by NIR-Hyperspectral-Imaging |date=24 October 2015 |doi=10.17648/NIR-2015-34127}}</ref> although black/strongly-coloured plastics, as well as composite materials like ] and ], which can give misleading readings. ] such as ]s or ] can then split by colour. Sensor based separation is more expensive to install but has the best recovery rates and produces more high-quality products.<ref name=Cimpan2016 />

===Scrap===
Plastic waste is either industrial ] (sometimes referred to as post industrial resin) or ]. Scrap is generated during production and is usually handled differently.<ref name=Kleinhans2021>{{cite journal |last1=Kleinhans |first1=Kerstin |last2=Demets |first2=Ruben |last3=Dewulf |first3=Jo |last4=Ragaert |first4=Kim |last5=De Meester |first5=Steven |title=Non-household end-use plastics: the 'forgotten' plastics for the circular economy |journal=Current Opinion in Chemical Engineering |date=June 2021 |volume=32 |pages=100680 |doi=10.1016/j.coche.2021.100680|issn=2211-3398 |doi-access=free|hdl=1854/LU-8710264 |hdl-access=free }}</ref> It can include ], trimmings, ] and rejects. As it is collected at the point of manufacture it is clean, and of a known type and grade, and is valuable. As scrap is mostly privately traded, it is often not included in official statistics.<ref name=Kleinhans2021 />

==Mechanical recycling==
]

The majority of plastic waste is made of ] polymers, which can be re-melted and reformed into new items via mechanical recycling. Globally, this is by far the most common form of recycling and in many countries it is the only type practised. It is the simplest and most economical technique. It has a lower ] than other processes.<ref name="Shaver">{{cite journal |last1=Schyns |first1=Zoé O. G. |last2=Shaver |first2=Michael P. |title=Mechanical Recycling of Packaging Plastics: A Review |journal=] |date=February 2021 |volume=42 |issue=3 |pages=2000415 |doi=10.1002/marc.202000415|pmid=33000883 |doi-access=free }}</ref> However, several factors can reduce output quality, which limits its applicability.<ref name="Shaver" />

Plastics are melted at anywhere between {{Convert|150-320|C|F|round=5}}, depending on polymer type.<ref name="flakes"/> This is sufficient to cause unwanted chemical reactions that degrade the output.<ref>{{cite journal |last1=Yin |first1=Shi |last2=Tuladhar |first2=Rabin |last3=Shi |first3=Feng |last4=Shanks |first4=Robert A. |last5=Combe |first5=Mark |last6=Collister |first6=Tony |title=Mechanical reprocessing of polyolefin waste: A review |journal=Polymer Engineering & Science |date=December 2015 |volume=55 |issue=12 |pages=2899–2909 |doi=10.1002/pen.24182}}</ref> This can produce volatile, low-] compounds, which may impart undesirable taste or odour, as well as discolouration. Additives can accelerate this degradation. For instance, ] additives, intended to improve the ] of plastic, also increase the degree of thermal degradation.<ref>{{cite journal |last1=Babetto |first1=Alex S. |last2=Antunes |first2=Marcela C. |last3=Bettini |first3=Sílvia H. P. |last4=Bonse |first4=Baltus C. |title=A Recycling-Focused Assessment of the Oxidative Thermomechanical Degradation of HDPE Melt Containing Pro-oxidant |journal=Journal of Polymers and the Environment |date=February 2020 |volume=28 |issue=2 |pages=699–712 |doi=10.1007/s10924-019-01641-6|s2cid=209432804 |url=https://repositorio.fei.edu.br/handle/FEI/3410 }}</ref><ref>{{cite journal |last1=Aldas |first1=Miguel |last2=Paladines |first2=Andrea |last3=Valle |first3=Vladimir |last4=Pazmiño |first4=Miguel |last5=Quiroz |first5=Francisco |title=Effect of the Prodegradant-Additive Plastics Incorporated on the Polyethylene Recycling |journal=International Journal of Polymer Science |date=2018 |volume=2018 |pages=1–10 |doi=10.1155/2018/2474176|doi-access=free }}</ref> ] can similarly have unwanted effects.<ref>{{cite journal |last1=Delva |first1=Laurens |last2=Hubo |first2=Sara |last3=Cardon |first3=Ludwig |last4=Ragaert |first4=Kim |title=On the role of flame retardants in mechanical recycling of solid plastic waste |journal=Waste Management |date=December 2018 |volume=82 |pages=198–206 |doi=10.1016/j.wasman.2018.10.030|pmid=30509582 |bibcode=2018WaMan..82..198D |s2cid=54487823 }}</ref> Product quality also depends strongly on how well the plastic was sorted. Many polymers are immiscible with each other when molten and ] (like oil and water) during reprocessing. Products made from such blends contain boundaries between the different polymers with weak cohesion across these boundaries, compromising mechanical properties. In more extreme cases the polymers may degrade each other, particularly with PVC, as it can generate ] which strongly affects condensation polymers such as PET.<ref>{{cite journal |last1=Paci |first1=M |last2=La Mantia |first2=F.P |title=Influence of small amounts of polyvinylchloride on the recycling of polyethyleneterephthalate |journal=Polymer Degradation and Stability |date=January 1999 |volume=63 |issue=1 |pages=11–14 |doi=10.1016/S0141-3910(98)00053-6}}</ref>

Many of these problems have technological solutions, though they bear a financial cost. Advanced ] and can be used to protect plastics from the stress of thermal reprocessing.<ref>{{cite journal |last1=Pfaendner |first1=R. |last2=Herbst |first2=H. |last3=Hoffmann |first3=K. |last4=Sitek |first4=F. |title=Recycling and restabilization of polymers for high quality applications. An Overview |journal=Angewandte Makromolekulare Chemie |date=October 1995 |volume=232 |issue=1 |pages=193–227 |doi=10.1002/apmc.1995.052320113}}</ref><ref>{{cite journal |last1=Pfaendner |first1=Rudolf |title=Restabilization – 30 years of research for quality improvement of recycled plastics Review |journal=Polymer Degradation and Stability |date=July 2022 |volume=203 |pages=110082 |doi=10.1016/j.polymdegradstab.2022.110082|doi-access=free}}</ref> Volatile degradation products can be removed by a range of ] techniques. Flame retardants can be removed by chemical treatment,<ref>{{cite journal |last1=Zhang |first1=Cong-Cong |last2=Zhang |first2=Fu-Shen |title=Removal of brominated flame retardant from electrical and electronic waste plastic by solvothermal technique |journal=Journal of Hazardous Materials |date=June 2012 |volume=221-222 |pages=193–198 |doi=10.1016/j.jhazmat.2012.04.033|pmid=22575175 |bibcode=2012JHzM..221..193Z |url=http://ir.rcees.ac.cn/handle/311016/7942 }}</ref> while damaging metallic additives can be rendered inert with ]. Finally, the properties of mixed plastics can be improved by using compatibilisers.<ref>{{cite journal |last1=Koning |first1=C |title=Strategies for compatibilization of polymer blends |journal=] |date=1998 |volume=23 |issue=4 |pages=707–757 |doi=10.1016/S0079-6700(97)00054-3|hdl=2268/4370 |hdl-access=free }}</ref><ref>{{cite journal |last1=Vilaplana |first1=Francisco |last2=Karlsson |first2=Sigbritt |title=Quality Concepts for the Improved Use of Recycled Polymeric Materials: A Review |journal=] |date=14 April 2008 |volume=293 |issue=4 |pages=274–297 |doi=10.1002/mame.200700393|doi-access=free }}</ref> These are compounds that improve ] between polymer types to give a more ] product, with better internal cohesion and improved mechanical properties. They are small-molecules possessing two chemical regions, each of which is compatible with a certain polymer. This allows them to act like molecular-nails or screws, anchoring the polymers to one another. As a result, compatibilisers are normally limited to systems dominated by two particular types of plastic and are not cost-effective for heterogeneous mixtures. No compatibiliser solves all plastic combinations. Even with these technologies, it is particularly challenging to recycle plastic so that it can meet ] standards.

===Closed-loop recycling===
In ], or primary recycling, used plastic is endlessly recycled back into new items of the same quality and type. For instance, turning drinks bottles back into drinks bottles. It can be considered an example of a ]. The continual mechanical recycling of plastic without reduction in quality is challenging due to cumulative polymer degradation<ref name=closing-loop>{{cite journal |last1=Eriksen |first1=M.K. |last2=Christiansen |first2=J.D. |last3=Daugaard |first3=A.E. |last4=Astrup |first4=T.F. |title=Closing the loop for PET, PE and PP waste from households: Influence of material properties and product design for plastic recycling |journal=Waste Management |date=August 2019 |volume=96 |pages=75–85 |doi=10.1016/j.wasman.2019.07.005|pmid=31376972 |bibcode=2019WaMan..96...75E |s2cid=199067235 |url=https://backend.orbit.dtu.dk/ws/files/186061805/Eriksen_et_al._2019_ORBIT.pdf }}</ref> and risk of contaminant build-up. In 2013 only 2% of plastic packaging was recycled in a closed loop.<ref name=ellen>{{cite web |title=The New Plastics Economy: Rethinking the future of plastics & catalysing action |url=https://www.ellenmacarthurfoundation.org/publications/the-new-plastics-economy-rethinking-the-future-of-plastics-catalysing-action |website=www.ellenmacarthurfoundation.org |access-date=28 May 2021}}</ref> Although closed-loop recycling has been investigated for many polymers,<ref name=closing-loop /> to-date the only industrial success is with ].<ref>{{cite journal |last1=Welle |first1=Frank |title=Twenty years of PET bottle to bottle recycling—An overview |journal=Resources, Conservation and Recycling |date=September 2011 |volume=55 |issue=11 |pages=865–875 |doi=10.1016/j.resconrec.2011.04.009}}</ref> This is because polymer degradation in PET is often repairable. PET's polymer chains tend to cleave at their ] groups and the alcohol and carboxyl groups left by this can be joined back together by the use of chemical agents called chain extenders.<ref>{{cite journal |last1=Schyns |first1=Zoé O. G. |last2=Shaver |first2=Michael P. |title=Mechanical Recycling of Packaging Plastics: A Review |journal=Macromolecular Rapid Communications |date=February 2021 |volume=42 |issue=3 |pages=2000415 |doi=10.1002/marc.202000415|pmid=33000883 |doi-access=free }}</ref> ] is one such compound.

===Open-loop recycling===
]

In open-loop recycling, also known as secondary recycling, or ], the quality of the plastic is reduced each time it is recycled, so that the material eventually becomes unrecyclable. It is the most common type.<ref name=ellen /> Recycling PET bottles into ] or other fibres is a common example, and accounts for the majority of PET recycling.<ref name=fibre>{{cite journal |last1=Shen |first1=Li |last2=Worrell |first2=Ernst |last3=Patel |first3=Martin K. |title=Open-loop recycling: A LCA case study of PET bottle-to-fibre recycling |journal=Resources, Conservation and Recycling |date=November 2010 |volume=55 |issue=1 |pages=34–52 |doi=10.1016/j.resconrec.2010.06.014}}</ref> ] shows it to be of ecological benefit.<ref>{{cite journal |last1=Huysman |first1=Sofie |last2=Debaveye |first2=Sam |last3=Schaubroeck |first3=Thomas |last4=Meester |first4=Steven De |last5=Ardente |first5=Fulvio |last6=Mathieux |first6=Fabrice |last7=Dewulf |first7=Jo |title=The recyclability benefit rate of closed-loop and open-loop systems: A case study on plastic recycling in Flanders |journal=Resources, Conservation and Recycling |date=August 2015 |volume=101 |pages=53–60 |doi=10.1016/j.resconrec.2015.05.014|hdl=1854/LU-6851927 |hdl-access=free }}</ref><ref name=cycles>{{cite journal |last1=Lazarevic |first1=David |last2=Aoustin |first2=Emmanuelle |last3=Buclet |first3=Nicolas |last4=Brandt |first4=Nils |title=Plastic waste management in the context of a European recycling society: Comparing results and uncertainties in a life cycle perspective |journal=Resources, Conservation and Recycling |date=December 2010 |volume=55 |issue=2 |pages=246–259 |doi=10.1016/j.resconrec.2010.09.014}}</ref><ref name=fibre /> Recycling can displace demand for fresh plastic.<ref name=Misconceptions>{{cite journal |last1=Geyer |first1=Roland |last2=Kuczenski |first2=Brandon |last3=Zink |first3=Trevor |last4=Henderson |first4=Ashley |title=Common Misconceptions about Recycling |journal=] |date=October 2016 |volume=20 |issue=5 |pages=1010–1017 |doi=10.1111/jiec.12355|bibcode=2016JInEc..20.1010G |s2cid=153936564 }}</ref> However, if it is used to produce items that would not otherwise have been made, then it is not displacing production and is of little or no benefit to the environment.

The reduction in polymer quality can be offset by mixing recycled and new materials. Compatibilised plastics can be used as a replacement for virgin material, as it is possible to produce them with the right ] needed for good results.<ref>{{cite journal |last1=Gupta |first1=Arvind |last2=Misra |first2=Manjusri |last3=Mohanty |first3=Amar K. |title=Novel sustainable materials from waste plastics: compatibilized blend from discarded bale wrap and plastic bottles |journal=] |date=2021 |volume=11 |issue=15 |pages=8594–8605 |doi=10.1039/D1RA00254F |pmid=35423365 |pmc=8695198 |bibcode=2021RSCAd..11.8594G |doi-access=free}}</ref> Low quality mixed plastics can be recycled in an open-loop, although demand for such products is limited. When these are mixed during reprocessing the result is usually an unappealing dark-brown. These blends find use as outdoor furniture or ]. As the material is weak, but of low cost it is produced in thick planks to provide material strength.

===Thermosets===
Although ] polymers do not melt, technologies have been developed for their mechanical recycling. This usually involves breaking the material down to small particles (crumbs), which can then be mixed with a binding agent to form a composite material. For instance, ] can be recycled as reconstituted crumb foam.<ref>{{cite journal |last1=Yang |first1=Wenqing |last2=Dong |first2=Qingyin |last3=Liu |first3=Shili |last4=Xie |first4=Henghua |last5=Liu |first5=Lili |last6=Li |first6=Jinhui |title=Recycling and Disposal Methods for Polyurethane Foam Wastes |journal=Procedia Environmental Sciences |date=2012 |volume=16 |pages=167–175 |doi=10.1016/j.proenv.2012.10.023|doi-access=free }}</ref><ref>{{cite journal |last1=Zia |first1=Khalid Mahmood |last2=Bhatti |first2=Haq Nawaz |last3=Ahmad Bhatti |first3=Ijaz |title=Methods for polyurethane and polyurethane composites, recycling and recovery: A review |journal=] |date=August 2007 |volume=67 |issue=8 |pages=675–692 |doi=10.1016/j.reactfunctpolym.2007.05.004}}</ref>

==Feedstock recycling==
In feedstock recycling, also called chemical recycling or tertiary recycling, polymers are reduced to their chemical building-blocks (]), which can then be ] back into fresh plastics.<ref>{{cite journal |last1=Lee |first1=Alicia |last2=Liew |first2=Mei Shan |title=Tertiary recycling of plastics waste: an analysis of feedstock, chemical and biological degradation methods |journal=Journal of Material Cycles and Waste Management |date=January 2021 |volume=23 |issue=1 |pages=32–43 |doi=10.1007/s10163-020-01106-2|bibcode=2021JMCWM..23...32L |s2cid=225247645 }}</ref><ref>{{cite journal |last1=Rahimi |first1=AliReza |last2=García |first2=Jeannette M. |title=Chemical recycling of waste plastics for new materials production |journal=Nature Reviews Chemistry |date=June 2017 |volume=1 |issue=6 |pages=0046 |doi=10.1038/s41570-017-0046}}</ref><ref>{{cite journal |last1=Coates |first1=Geoffrey W. |last2=Getzler |first2=Yutan D. Y. L. |title=Chemical recycling to monomer for an ideal, circular polymer economy |journal=Nature Reviews Materials |date=July 2020 |volume=5 |issue=7 |pages=501–516 |doi=10.1038/s41578-020-0190-4|bibcode=2020NatRM...5..501C |s2cid=215760966 }}</ref> In theory, this allows for near infinite recycling; as impurities, additives, dyes and chemical defects are completely removed with each cycle.<ref name=life>{{cite journal |last1=Vollmer |first1=Ina |last2=Jenks |first2=Michael J. F. |last3=Roelands |first3=Mark C. P. |last4=White |first4=Robin J. |last5=Harmelen |first5=Toon |last6=Wild |first6=Paul |last7=Laan |first7=Gerard P. |last8=Meirer |first8=Florian |last9=Keurentjes |first9=Jos T. F. |last10=Weckhuysen |first10=Bert M. |title=Beyond Mechanical Recycling: Giving New Life to Plastic Waste |journal=Angewandte Chemie International Edition |date=September 2020 |volume=59 |issue=36 |pages=15402–15423 |doi=10.1002/anie.201915651 |pmid=32160372 |pmc=7497176 |doi-access=free}}</ref><ref name="Thiounn2020">{{cite journal |last1=Thiounn |first1=Timmy |last2=Smith |first2=Rhett C. |title=Advances and approaches for chemical recycling of plastic waste |journal=Journal of Polymer Science |date=15 May 2020 |volume=58 |issue=10 |pages=1347–1364 |doi=10.1002/pol.20190261|doi-access=free}}</ref> In practice, chemical recycling is far less common than mechanical recycling. Implementation is limited because technologies do not yet exist to reliably depolymerise all polymers on an industrial scale and also because the equipment and operating costs are much higher. In 2018 Japan had one of the highest rates in the world at ~4%, compared to 23% mechanical recycling,<ref>{{cite journal |last1=Kumagai |first1=Shogo |last2=Nakatani |first2=Jun |last3=Saito |first3=Yuko |last4=Fukushima |first4=Yasuhiro |last5=Yoshioka |first5=Toshiaki |title=Latest Trends and Challenges in Feedstock Recycling of Polyolefinic Plastics |journal=Journal of the Japan Petroleum Institute |date=1 November 2020 |volume=63 |issue=6 |pages=345–364 |doi=10.1627/jpi.63.345|doi-access=free }}</ref> in the same period Germany, another major recycler, reported a feedstock recycling rate of 0.2%.<ref>{{cite web |title=Plastics - the Facts 2020 |url=https://www.plasticseurope.org/application/files/8016/1125/2189/AF_Plastics_the_facts-WEB-2020-ING_FINAL.pdf |website=PlasticsEurope |access-date=1 September 2021}}</ref> Depolymerising, purifying and re-polymerising the plastic can also be energy intensive, leading to the ] of feedstock recycling normally being higher than that of mechanical recycling.<ref name="Shaver" /> PET, PU and PS are depolymerised commercially to varying extents,<ref name=life /> but the feedstock recycling of polyolefins, which make-up nearly half of all plastics, is much more limited.<ref name="Thiounn2020"/>

===Thermal depolymerisation===
Certain polymers like ], polystyrene, ], and ] (PMMA) undergo ] when heated to sufficiently high temperatures.<ref>{{cite journal |last1=Kaminsky |first1=W |last2=Predel |first2=M |last3=Sadiki |first3=A |title=Feedstock recycling of polymers by pyrolysis in a fluidised bed |journal=Polymer Degradation and Stability |date=September 2004 |volume=85 |issue=3 |pages=1045–1050 |doi=10.1016/j.polymdegradstab.2003.05.002}}</ref> The reactions are sensitive to impurities and require clean and well sorted waste to produce a good product. Even then, not all depolymerisation reactions are completely efficient and some competitive ] is often observed; the monomers, therefore, require purification before reuse. The feedstock recycling of polystyrene has been commercialised,<ref name=Thiounn2020/> but global capacity remains fairly limited.

===Chemical depolymerisation===
]s bearing cleavable groups such as ] and ] can be completely depolymerised by ] or ]. This can be a purely chemical process but may also be promoted by enzymes such as ].<ref>{{Cite journal|last1=Tournier|first1=V.|last2=Topham|first2=C. M.|last3=Gilles|first3=A.|last4=David|first4=B.|last5=Folgoas|first5=C.|last6=Moya-Leclair|first6=E.|last7=Kamionka|first7=E.|last8=Desrousseaux|first8=M.-L.|last9=Texier|first9=H.|last10=Gavalda|first10=S.|last11=Cot|first11=M.|date=April 2020|title=An engineered PET depolymerase to break down and recycle plastic bottles|url=http://www.nature.com/articles/s41586-020-2149-4|journal=Nature|language=en|volume=580|issue=7802|pages=216–219|doi=10.1038/s41586-020-2149-4|pmid=32269349|bibcode=2020Natur.580..216T|s2cid=215411815|issn=0028-0836}}</ref><ref>{{cite journal |last1=Wei |first1=Ren |last2=Zimmermann |first2=Wolfgang |title=Microbial enzymes for the recycling of recalcitrant petroleum-based plastics: how far are we? |journal=Microbial Biotechnology |date=November 2017 |volume=10 |issue=6 |pages=1308–1322 |doi=10.1111/1751-7915.12710|pmid=28371373 |pmc=5658625 }}</ref> Such technologies have lower energy costs than thermal depolymerisation but are not available for all polymers. Polyethylene terephthalate has been the most heavily studied polymer,<ref>{{cite journal |last1=Geyer |first1=B. |last2=Lorenz |first2=G. |last3=Kandelbauer |first3=A. |title=Recycling of poly(ethylene terephthalate) – A review focusing on chemical methods |journal=Express Polymer Letters |date=2016 |volume=10 |issue=7 |pages=559–586 |doi=10.3144/expresspolymlett.2016.53|doi-access=free }}</ref> and has reached commercial scale.<ref name=life />

==Energy recovery==
], Thailand. Well regulated incinerators reduce harmful toxins released during the burning process, but not all plastic is burned in proper facilities.]]

Energy recovery, also called energy recycling or quaternary recycling, involves burning waste plastic in place of ] for energy production.<ref>{{cite journal |last1=Singh |first1=Narinder |last2=Hui |first2=David |last3=Singh |first3=Rupinder |last4=Ahuja |first4=I.P.S. |last5=Feo |first5=Luciano |last6=Fraternali |first6=Fernando |title=Recycling of plastic solid waste: A state of art review and future applications |journal=Composites Part B: Engineering |date=April 2017 |volume=115 |pages=409–422 |doi=10.1016/j.compositesb.2016.09.013}}</ref><ref name="auto"/> It is included in the recycling data reported by many countries,<ref name=JP>{{cite web |title=An Introduction to Plastic Recycling in Japan 2019 |url=https://www.pwmi.or.jp/ei/plastic_recycling_2019.pdf |publisher=Plastic Waste Management Institute |access-date=19 May 2021}}</ref><ref name=US>{{cite web |last1=US EPA |first1=OLEM |title=Plastics: Material-Specific Data |url=https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling/plastics-material-specific-data |website=US EPA |language=en |date=2017-09-12}}</ref> although it is not considered recycling by the EU.<ref>{{Cite web|date=2008 |location=Paragraph 15a|title=Directive 2008/98/EC of the European Parliament and of the Council. Article 3: Definitions|url=https://www.legislation.gov.uk/eudr/2008/98/article/3|access-date=August 4, 2021|website=Legislation.gov.uk}}</ref> It is distinct from ] without energy recovery, which is historically more common, but which does not reduce either plastic production or fossil fuel use.

Energy recovery is often the waste management method of last resort, a position previously held by landfill. In urban areas a lack of suitable sites for new landfills can drive this,<ref name=US-WtE>{{cite journal |title=A review on municipal solid waste-to-energy trends in the USA |journal=] |date=1 March 2020 |volume=119 |pages=109512 |doi=10.1016/j.rser.2019.109512|last1=Mukherjee |first1=C. |last2=Denney |first2=J. |last3=Mbonimpa |first3=E.G. |last4=Slagley |first4=J. |last5=Bhowmik |first5=R. |s2cid=209798113 |doi-access=free }}</ref> but it is also driven by regulation, such as the EU's ] or other ] policies. Compared to the other recycling options, its appeal is largely economic. If the correct technologies are used, then the plastics do not need to be separated, or from other ] (garbage), which reduces costs. Compared to the sometimes variable market for recyclables, demand for electricity is universal and better understood, reducing the perceived ]. As a means of waste management, it is highly effective, reducing the volume of waste by about 90%, with the residues sent to landfill or used to make ]. Although its CO<sub>2</sub> emissions are high, comparing its overall ecological desirability to other recycling technologies is difficult.<ref name=cycles /> For instance, while recycling greatly reduces greenhouse gas emissions compared to incineration, it is an expensive way of achieving these reductions when compared to investing in ].<ref>{{cite journal |last1=Gradus |first1=Raymond H.J.M. |last2=Nillesen |first2=Paul H.L. |last3=Dijkgraaf |first3=Elbert |last4=van Koppen |first4=Rick J. |title=A Cost-effectiveness Analysis for Incineration or Recycling of Dutch Household Plastic Waste |journal=] |date=May 2017 |volume=135 |pages=22–28 |doi=10.1016/j.ecolecon.2016.12.021|bibcode=2017EcoEc.135...22G |hdl=1871.1/390ebc9d-5968-479b-bd72-23ffe7c85c43 |s2cid=21744131 |url=https://research.vu.nl/en/publications/390ebc9d-5968-479b-bd72-23ffe7c85c43 |hdl-access=free }}</ref>

Plastic waste may be burnt as ] (RDF), or it may be chemically converted to a ] first. In either approach PVC must be excluded or compensated for by installing dechlorination technologies, as it generates large amounts of ] (HCl) when burnt. This can corrode equipment and cause undesirable chlorination of fuel products.<ref>{{cite journal |last1=Fukushima |first1=Masaaki |last2=Wu |first2=Beili |last3=Ibe |first3=Hidetoshi |last4=Wakai |first4=Keiji |last5=Sugiyama |first5=Eiichi |last6=Abe |first6=Hironobu |last7=Kitagawa |first7=Kiyohiko |last8=Tsuruga |first8=Shigenori |last9=Shimura |first9=Katsumi |last10=Ono |first10=Eiichi |title=Study on dechlorination technology for municipal waste plastics containing polyvinyl chloride and polyethylene terephthalate |journal=Journal of Material Cycles and Waste Management |date=June 2010 |volume=12 |issue=2 |pages=108–122 |doi=10.1007/s10163-010-0279-8|bibcode=2010JMCWM..12..108F |s2cid=94190060 }}</ref> Burning has long been associated with the release of harmful ], however these hazards can be abated by the use of advanced combustors and emission control systems. Incineration with energy recovery remains the most common method, with more advanced waste-to-fuel technologies such as ] hindered by technical and cost hurdles.<ref name=US-WtE /><ref>{{cite journal |last1=Fernández-González |first1=J.M. |last2=Grindlay |first2=A.L. |last3=Serrano-Bernardo |first3=F. |last4=Rodríguez-Rojas |first4=M.I. |last5=Zamorano |first5=M. |title=Economic and environmental review of Waste-to-Energy systems for municipal solid waste management in medium and small municipalities |journal=Waste Management |date=September 2017 |volume=67 |pages=360–374 |doi=10.1016/j.wasman.2017.05.003|pmid=28501263 |bibcode=2017WaMan..67..360F }}</ref>

===Waste-to-fuel===
{{See also|Waste-to-energy}}

Mixed plastic waste can be depolymerised to give a synthetic fuel. This has a higher ] than the starting plastic and can be burnt more efficiently, although it remains less efficient than fossil fuels.<ref>{{cite conference |last1=Nugroho |first1=Arif Setyo |last2=Chamim |first2=Moch. |last3=Hidayah |first3=Fatimah N. |title=Plastic waste as an alternative energy |conference=Human-Dedicated Sustainable Product and Process Design: Materials |series=AIP Conference Proceedings |date=2018 |volume=1977 |issue=1 |pages=060010 |doi=10.1063/1.5043022|bibcode=2018AIPC.1977f0010N |doi-access=free }}</ref> Various conversion technologies have been investigated, of which pyrolysis is the most common.<ref name=2011CommercialRev>{{cite journal |last1=Butler |first1=E. |last2=Devlin |first2=G. |last3=McDonnell |first3=K. |title=Waste Polyolefins to Liquid Fuels via Pyrolysis: Review of Commercial State-of-the-Art and Recent Laboratory Research |journal=Waste and Biomass Valorization |date=1 August 2011 |volume=2 |issue=3 |pages=227–255 |doi=10.1007/s12649-011-9067-5|hdl=10197/6103 |s2cid=98550187 |hdl-access=free }}</ref><ref>{{cite journal |last1=Anuar Sharuddin |first1=Shafferina Dayana |last2=Abnisa |first2=Faisal |last3=Wan Daud |first3=Wan Mohd Ashri |last4=Aroua |first4=Mohamed Kheireddine |title=A review on pyrolysis of plastic wastes |journal=Energy Conversion and Management |date=May 2016 |volume=115 |pages=308–326 |doi=10.1016/j.enconman.2016.02.037|bibcode=2016ECM...115..308A }}</ref> Conversion can take place as part of incineration in an ], but often the aim is to collect the fuel to sell it. Pyrolysis of mixed plastics can give a fairly broad mix of chemical products (between 1 and 15 carbon atoms) including gases and ] liquids.<ref>{{cite journal |last1=Kaminsky |first1=W. |last2=Schlesselmann |first2=B. |last3=Simon |first3=C.M. |title=Thermal degradation of mixed plastic waste to aromatics and gas |journal=Polymer Degradation and Stability |date=August 1996 |volume=53 |issue=2 |pages=189–197 |doi=10.1016/0141-3910(96)00087-0}}</ref><ref>{{Cite journal|last1=Quesada|first1=L.|last2=Calero|first2=M.|last3=Martín-Lara|first3=M. A.|last4=Pérez|first4=A.|last5=Blázquez|first5=G.|date=2019-11-01|title=Characterization of fuel produced by pyrolysis of plastic film obtained of municipal solid waste|url=http://www.sciencedirect.com/science/article/pii/S0360544219315464|journal=Energy|language=en|volume=186|pages=115874|doi=10.1016/j.energy.2019.115874|bibcode=2019Ene...18615874Q |s2cid=201243993|issn=0360-5442}}</ref><ref>{{cite journal |last1=Kumagai |first1=Shogo |last2=Yoshioka |first2=Toshiaki |title=Feedstock Recycling via Waste Plastic Pyrolysis |journal=Journal of the Japan Petroleum Institute |date=1 November 2016 |volume=59 |issue=6 |pages=243–253 |doi=10.1627/jpi.59.243 |url=https://www.jstage.jst.go.jp/article/jpi/59/6/59_243/_article/-char/en|doi-access=free }}</ref> Catalysts can give a better-defined product with a higher value.<ref>{{cite journal |last1=Aguado |first1=J. |last2=Serrano |first2=D. P. |last3=Escola |first3=J. M. |title=Fuels from Waste Plastics by Thermal and Catalytic Processes: A Review |journal=] |date=5 November 2008 |volume=47 |issue=21 |pages=7982–7992 |doi=10.1021/ie800393w}}</ref><ref>{{cite journal |last1=Miandad |first1=R. |last2=Barakat |first2=M. A. |last3=Aburiazaiza |first3=Asad S. |last4=Rehan |first4=M. |last5=Nizami |first5=A. S. |title=Catalytic pyrolysis of plastic waste: A review |journal=Process Safety and Environmental Protection |date=1 July 2016 |volume=102 |pages=822–838 |doi=10.1016/j.psep.2016.06.022 }}</ref><ref>{{cite journal |last1=Rehan |first1=M. |last2=Miandad |first2=R. |last3=Barakat |first3=M. A. |last4=Ismail |first4=I. M. I. |last5=Almeelbi |first5=T. |last6=Gardy |first6=J. |last7=Hassanpour |first7=A. |last8=Khan |first8=M. Z. |last9=Demirbas |first9=A. |last10=Nizami |first10=A. S. |title=Effect of zeolite catalysts on pyrolysis liquid oil |journal=International Biodeterioration & Biodegradation |date=1 April 2017 |volume=119 |pages=162–175 |doi=10.1016/j.ibiod.2016.11.015 |bibcode=2017IBiBi.119..162R |url=http://eprints.whiterose.ac.uk/109930/7/Revised%20Manuscript%20%28R1%29.pdf }}</ref> Liquid products can be used as ] fuel,<ref>{{cite journal |last1=Bukkarapu |first1=Kiran Raj |last2=Gangadhar |first2=D. Siva |last3=Jyothi |first3=Y. |last4=Kanasani |first4=Prasad |title=Management, conversion, and use of waste plastic as a source of sustainable energy to run automotive: a review |journal=Energy Sources, Part A: Recovery, Utilization, and Environmental Effects |date=18 July 2018 |volume=40 |issue=14 |pages=1681–1692 |doi=10.1080/15567036.2018.1486898|s2cid=103779086 }}</ref> with commercial production in several countries.<ref>{{cite journal |last1=Oasmaa |first1=Anja |title=Pyrolysis of plastic waste: opportunities and challenges |url=https://dc.engconfintl.org/pyroliq_2019/39 |journal=Pyroliq 2019: Pyrolysis and Liquefaction of Biomass and Wastes |publisher=ECI Digital Archives |access-date=10 June 2021 |date=2019-06-17|volume=152 |doi=10.1016/j.jaap.2020.104804 |bibcode=2020JAAP..15204804Q }}</ref> ] shows that plastic-to-fuel can displace fossil fuels and lower net ] emissions (~15% reduction).<ref name="auto1">{{cite journal |last1=Benavides |first1=Pahola Thathiana |last2=Sun |first2=Pingping |last3=Han |first3=Jeongwoo |last4=Dunn |first4=Jennifer B. |last5=Wang |first5=Michael |title=Life-cycle analysis of fuels from post-use non-recycled plastics |journal=] |date=September 2017 |volume=203 |pages=11–22 |doi=10.1016/j.fuel.2017.04.070|osti=1353191 |doi-access=free |bibcode=2017Fuel..203...11B }}</ref>

Compared to the widespread practise of incineration, plastic-to-fuel technologies have struggled to become economically viable.<ref name=2011CommercialRev /><ref>{{cite journal |last1=Rollinson |first1=Andrew Neil |last2=Oladejo |first2=Jumoke Mojisola |title='Patented blunderings', efficiency awareness, and self-sustainability claims in the pyrolysis energy from waste sector |journal=Resources, Conservation and Recycling |date=February 2019 |volume=141 |pages=233–242 |doi=10.1016/j.resconrec.2018.10.038|s2cid=115296275 }}</ref>

==Other Uses==

=== Coke replacement ===
Many ] can be used as a ] source (in place of ]) in scrap ] recycling,<ref>{{Cite web |url=http://www.cnn.com/2005/TECH/08/10/plastic.steel.reut/index.html |title=Scientists use plastic to make steel|website=CNN.com|access-date=10 August 2005 |archive-url=https://web.archive.org/web/20050812011212/http://www.cnn.com/2005/TECH/08/10/plastic.steel.reut/index.html |archive-date=12 August 2005 |url-status=dead |df=dmy-all }}</ref> with roughly 200,000 tonnes of waste plastics processed each year in Japan.<ref>{{cite journal |last1=Nomura |first1=Seiji |title=Use of Waste Plastics in Coke Oven: A Review |journal=Journal of Sustainable Metallurgy |date=March 2015 |volume=1 |issue=1 |pages=85–93 |doi=10.1007/s40831-014-0001-5|s2cid=137233367 |doi-access=free |bibcode=2015JSusM...1...85N }}</ref>

=== Construction and concrete ===
The use of recovered plastics in engineering materials is gaining ground.<ref>{{Cite journal |last1=Khan |first1=Kaffayatullah |last2=Jalal |first2=Fazal E. |last3=Iqbal |first3=Mudassir |last4=Khan |first4=Muhammad Imran |last5=Amin |first5=Muhammad Nasir |last6=Al-Faiad |first6=Majdi Adel |date=2022-04-23 |title=Predictive Modeling of Compression Strength of Waste PET/SCM Blended Cementitious Grout Using Gene Expression Programming |journal=Materials |language=en |volume=15 |issue=9 |pages=3077 |doi=10.3390/ma15093077 |issn=1996-1944 |pmc=9102582 |pmid=35591409|bibcode=2022Mate...15.3077K |doi-access=free }}</ref> Ground plastic may be used as a ] or filler material in certain applications.<ref>{{Cite journal |last1=Reis |first1=J. M. L. |last2=Carneiro |first2=E. P. |date=2012-02-01 |title=Evaluation of PET waste aggregates in polymer mortars |url=https://www.sciencedirect.com/science/article/pii/S0950061811004521 |journal=Construction and Building Materials |language=en |volume=27 |issue=1 |pages=107–111 |doi=10.1016/j.conbuildmat.2011.08.020 |issn=0950-0618}}</ref><ref>{{Cite journal |last1=Gavela |first1=Stamatia |last2=Rakanta |first2=Eleni |last3=Ntziouni |first3=Afroditi |last4=Kasselouri-Rigopoulou |first4=Vasilia |date=2022-10-24 |title=Eleven-Year Follow-Up on the Effect of Thermoplastic Aggregates' Addition to Reinforced Concrete |journal=Buildings |volume=12 |issue=11 |pages=1779 |doi=10.3390/buildings12111779 |doi-access=free |issn=2075-5309}}</ref> While generally unsuitable in structural concrete, plastic's inclusion in ], (forming ]), ] and recycled insulation can be beneficial.<ref>{{cite journal |last1=Awoyera |first1=P.O. |last2=Adesina |first2=A. |title=Plastic wastes to construction products: Status, limitations and future perspective |journal=Case Studies in Construction Materials |date=June 2020 |volume=12 |pages=e00330 |doi=10.1016/j.cscm.2020.e00330|s2cid=212815459 |doi-access=free }}</ref> An example of this is the construction of ]s. These may be made entirely of plastic or can incorporate significant amounts of plastic. The practice is popular in India, which by 2021 had constructed some 700&nbsp;km (435 miles) of highways.<ref>{{cite news|url=https://pib.gov.in/PressReleseDetailm.aspx?PRID=1740262|title=Use of Plastic Waste in Road Construction}}</ref> It may allow the ] of ] into the environment.<ref>{{cite journal |last1=Conlon |first1=Katie |title=Plastic roads: not all they're paved up to be |journal=International Journal of Sustainable Development & World Ecology |date=18 April 2021 |volume=29 |pages=80–83 |doi=10.1080/13504509.2021.1915406|s2cid=234834344 |url=https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=1314&context=usp_fac }}</ref> Research is ongoing to use plastics in various forms in cementitious materials such as concrete. Densifying plastic materials such as PET and plastic bags and then using them to partially replace aggregate and depolymerizing PET to use as a polymeric binder to enhance concrete are under study.<ref>{{Cite journal |last1=Dębska |first1=Bernardeta |last2=Brigolini Silva |first2=Guilherme Jorge |date=January 2021 |title=Mechanical Properties and Microstructure of Epoxy Mortars Made with Polyethylene and Poly(Ethylene Terephthalate) Waste |journal=Materials |language=en |volume=14 |issue=9 |pages=2203 |doi=10.3390/ma14092203 |issn=1996-1944 |pmc=8123358 |pmid=33923013|bibcode=2021Mate...14.2203D |doi-access=free }}</ref><ref>{{Cite journal |last1=Thorneycroft |first1=J. |last2=Orr |first2=J. |last3=Savoikar |first3=P. |last4=Ball |first4=R. J. |date=2018-02-10 |title=Performance of structural concrete with recycled plastic waste as a partial replacement for sand |url=https://www.sciencedirect.com/science/article/pii/S0950061817323474 |journal=Construction and Building Materials |language=en |volume=161 |pages=63–69 |doi=10.1016/j.conbuildmat.2017.11.127 |issn=0950-0618}}</ref><ref>{{Cite journal |last1=Bahij |first1=Sifatullah |last2=Omary |first2=Safiullah |last3=Feugeas |first3=Francoise |last4=Faqiri |first4=Amanullah |date=2020-07-15 |title=Fresh and hardened properties of concrete containing different forms of plastic waste – A review |url=https://www.sciencedirect.com/science/article/pii/S0956053X20302981 |journal=Waste Management |language=en |volume=113 |pages=157–175 |doi=10.1016/j.wasman.2020.05.048 |pmid=32534235 |bibcode=2020WaMan.113..157B |s2cid=219637371 |issn=0956-053X}}</ref>


==See also== ==See also==
{{Commons category|Plastic recycling}}
{{Portal|Environment}} {{Portal|Environment}}
* ]
* ], esp. relevant to types 3 & 7 plastics
* ] * ]
* ] * ]
* ] * ]
* ]
* ] * ]
* ] * ]

* ]
== Sources ==
{{Free-content attribution
| title = Drowning in Plastics – Marine Litter and Plastic Waste Vital Graphics
| publisher = United Nations Environment Programme
| documentURL = https://www.unep.org/resources/report/drowning-plastics-marine-litter-and-plastic-waste-vital-graphics
| license statement URL = https://commons.wikimedia.org/File:United_Nations_Environment_Programme_Drowning_in_Plastics_%E2%80%93_Marine_Litter_and_Plastic_Waste_Vital_Graphics.pdf
| license = Cc BY-SA 3.0 IGO
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==References== ==References==
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==External links== ==External links==
{{Commons category|Plastic recycling}}
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* {{cite web
|url=http://environment.about.com/od/reducingwaste/a/corn_plastic.htm
|title=Recyclable Plastic: Why are So Few Food Containers Made of Recyclable Plastic?
|publisher=About.com
|access-date=4 May 2009
|last=West
|first=Larry
}}
* ] * ]


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Latest revision as of 21:43, 6 January 2025

Processes which convert waste plastic into new items

Plastic recyclingClockwise from top left:
  • Sorting plastic waste at a single-stream recycling centre
  • Baled colour-sorted used bottles
  • Recovered HDPE ready for recycling
  • A watering can made from recycled bottles

Plastic recycling is the processing of plastic waste into other products. Recycling can reduce dependence on landfill, conserve resources and protect the environment from plastic pollution and greenhouse gas emissions. Recycling rates lag behind those of other recoverable materials, such as aluminium, glass and paper. From the start of plastic production through to 2015, the world produced around 6.3 billion tonnes of plastic waste, only 9% of which has been recycled and only ~1% has been recycled more than once. Of the remaining waste, 12% was incinerated and 79% was either sent to landfills or lost to the environment as pollution.

Almost all plastic is non-biodegradable and without recycling, spreads across the environment where it causes plastic pollution. For example, as of 2015, approximately 8 million tonnes of waste plastic enters the oceans annually, damaging oceanic ecosystems and forming ocean garbage patches.

Almost all recycling is mechanical and involves the melting and reforming of plastic into other items. This can cause polymer degradation at the molecular level, and requires that waste be sorted by colour and polymer type before processing, which is often complicated and expensive. Errors can lead to material with inconsistent properties, rendering it unappealing to industry. Though filtration in mechanical recycling reduces microplastic release, even the most efficient filtration systems cannot prevent the release of microplastics into wastewater.

In feedstock recycling, waste plastic is converted into its starting chemicals, which can then become fresh plastic. This involves higher energy and capital costs. Alternatively, plastic can be burned in place of fossil fuels in energy recovery facilities, or biochemically converted into other useful chemicals for industry. In some countries, burning is the dominant form of plastic waste disposal, particularly where landfill diversion policies are in place.

Plastic recycling is low in the waste hierarchy, meaning that reduction and reuse are more favourable and long-term solutions for sustainability.

It has been advocated since the early 1970s, but due to economic and technical challenges, did not impact the management of plastic waste to any significant extent until the late 1980s. The plastics industry has been criticised for lobbying for expansion of recycling programmes, even while research showed that most plastic could not be economically recycled. This has resulted in occasions where plastic waste dropped into recycling bins has not been recycled, and been treated as general waste.

History

Although plastics were discovered before the 20th century, large-scale production was not realised until World War II. Nylon replaced silk in parachutes, while Perspex was a light-weight alternative to glass in aeroplanes. After the war these materials were commercialized. The plastic age began around 1950, part of the post-war economic boom.

Global environmental movements in the 1960s and 1970s led to the formation of environmental agencies. (EPA, 1970), EU (DG ENV, 1973) Australia (EPA, 1971) and Japan (JEA 1971). Environmental awareness put plastic waste under scrutiny. The earliest effort to abate plastic pollution was arguably the 1973 and 1978 MARPOL agreements, whose Annex V banned dumping plastics in the oceans.

Industry lobbying

Photograph of Girl Scouts picking up discarded trash in 1970.
Girl Scouts on a Keep America Beautiful cleanup in 1970. The Keep American Beautiful campaign was a greenwashing campaign by the plastics and other polluting industries founded in the 1970s to try to displace responsibility of plastic pollution and other disposable packing trash onto consumers as "littering".

As regulations expanded, the plastics industry responded with lobbying to preserve their business interests. In the U.S., the 1970 Resource Recovery Act directed the nation towards recycling and energy recovery. More than a thousand attempts to pass legislation to ban or tax packaging, including plastics, came by 1976. The plastics industry responded by lobbying for plastic to be recycled. A $50 million per year campaign was run by organisations such as Keep America Beautiful with the message that plastic could and would be recycled, as well as lobbying for the establishment of curbside recycling.

However, plastic could not be economically recycled using the technology of the time. For example, an April 1973 report written by industry scientists stated that, "There is no recovery from obsolete products" and that, "A degradation of resin properties and performance occurs during the initial fabrication, through aging, and in any reclamation process." The report concluded that sorting the plastic is "infeasible". Contemporary scientific reports highlighted numerous technical barriers.

Globally, plastic waste was almost entirely disposed of via landfill until the 1980s when rates of incineration increased. Although better technology was known, these early incinerators often lacked advanced combustors or emission-control systems, leading to the release of dioxins and dioxin-like compounds.

In the late 1980s plastic recycling began in earnest. In 1988 the U.S. Society of the Plastics Industry created the Council for Solid Waste Solutions as a trade association to promote the idea of plastic recycling to the public. The association lobbied American municipalities to launch or expand plastic waste collection programmes and lobbied U.S. states to require the labelling of plastic containers and products with recycling symbols.

The industry introduced resin identification codes in 1988, which provided a standard system for the identification of various polymer types at materials recovery facilities.

Global recycling trade

Globalisation during the 1990s included the export of plastic waste from advanced economies to developing and middle-income ones, where it could be sorted and recycled less expensively. The annual trade in plastic waste increased rapidly from 1993 onwards as part of the global waste trade.

Many governments count items as recycled if they have been exported for that purpose, regardless of the actual outcome. The practice has been labeled environmental dumping, as environmental laws and enforcement are generally weaker in less developed economies. By 2016 about 14 Mt of plastic waste was exported, with China taking 7.35 Mt. Much of this was low quality mixed plastic that ended up in landfills. However, recycled plastic is used extensively in manufacturing in China, and imported plastic waste was predominantly processed using low-technology processing. High-income countries such as Germany, Japan, the United Kingdom and the United States were the top exporters.

In 2017, China began restricting waste plastics imports via Operation National Sword. Exporters eventually exported to other countries mostly in Southeast Asia, such as Vietnam and Malaysia, but also Turkey and India. Indonesia, Malaysia, and Thailand reacted to illegal plastic waste imports by reinforcing border controls. Illegally imported containers were repatriated or refused entry. Consequently, plastic waste containers accumulated in ports.

Given limited export options, attention turned to local solutions. Proposed extended producer responsibility would tax plastic producers to subsidise recyclers.

In 2019, international trade in plastic waste became regulated under the Basel Convention. Under the convention, any Party can decide to prohibit imports of hazardous plastic waste and, since 1 January 2021, of some mixed plastic wastes. Parties to the convention are required to ensure environmentally sound management of their refuse either through alternative importers or by increasing capacity.

The COVID-19 pandemic temporarily reduced trade in plastic waste, due in part to reduced activity at waste management facilities, shipping disruptions, and low oil prices that reduced the cost of virgin plastic and made recycling less profitable.

European Union strategic developments

The European Commission's "Action Plan" for a circular economy, adopted in December 2015, saw plastics as a strategic priority for developing circular economy actions. In 2017, the Commission further adopted a focus on plastic production and use, targeting the achievement of all plastic packaging being recyclable by 2030. The Commission then issued a strategic document in January 2018 which set out an "ambitious vision" and an opportunity for global action on plastic recycling.

Production and recycling rates

see caption
Global quantities of plastic produced and disposed of annually (1950–2015), showing the estimated amounts disposed of via landfill, recycling and incineration.

The total amount of plastic ever produced worldwide, until 2015, is estimated to be 8.3 billion tonnes (Bt). Approximately 6.3 Bt of this was discarded as waste, of which around 79% accumulated in landfills or the natural environment, 12% was incinerated, and 9% was recycled - only ~1% of all plastic has been recycled more than once. More recently, as of 2017, still only 9% of the 9 Bt of plastic produced was recycled.

By 2015 global production had reached some 381 million tonnes (Mt) per year. The recycling rate that year was 19.5%, while 25.5% was incinerated and the remaining 55% disposed of, largely to landfill. These rates lag behind those of other recyclables, such as paper, metal and glass. Although the percentage of recycled or incinerated material is increasing each year, the tonnage of waste left-over also continues to rise. Production could reach ~800 Mt per year by 2040, although implementing all feasible interventions could reduce plastic pollution by 40% from 2016 rates.

Recycling rates vary among types of plastic. Several types are in common use, each with distinct chemical and physical properties. This affects sorting and reprocessing costs; which affects the value and market size for recovered materials. PET and HDPE have the highest recycling rates, whereas polystyrene and polyurethane are rarely recycled.

One of the reasons for low levels of plastic recycling is weak demand, given the materials' poor/inconsistent properties. The percentage of plastic that can be fully recycled, rather than downcycled or go to waste, can be increased when manufacturers minimise mixing of packaging materials and eliminate contaminants. The Association of Plastics Recyclers has issued a "Design Guide for Recyclability".

The most commonly produced plastic consumer products include packaging made from LDPE (e.g. bags, containers, food packaging film), containers made from HDPE (e.g. milk bottles, shampoo bottles, ice cream tubs), and PET (e.g. bottles for water and other drinks). Together these products account for around 36% of plastic production. The use of plastics in building and construction, textiles, transportation and electrical equipment accounts for another substantial share of the plastics market.

Regional data

Plastic consumption differs among countries and communities, although it is found almost everywhere. As of 2022 North American countries (NAFTA) accounted for 21% of global plastic consumption, closely followed by China (20%) and Western Europe (18%). In North America and Europe per capita plastic consumption was 94 kg and 85 kg/capita/year, respectively. China reached 58 kg/capita/year.

In 2012, 25.2 Mt of post-consumer plastic waste was collected in the European Union. Of this, more than 60% (15.6 Mt) was recovered and 40% (9.6 Mt) was disposed of as municipal solid waste (MSW). Of the 15.6 Mt of recovered plastic waste, about 6.6 Mt was recycled, while the remainder was likely used as refuse-derived fuel (RDF) or incinerated in MSW incinerators with energy recovery (about 9 Mt). Europe leads in plastics recycling, reusing about 26%.

The recycling activities of the largest producers of plastic waste have the greatest effect on global averages. These are a mix of advanced economies and large developing nations. Some publish official statistics on their plastic recycling rates. Others may release partial data, usually limited to population centres. This makes it difficult to draw accurate comparisons, especially as the published recycling rates vary.

12 largest producers of plastic waste (+EU) and their recycling rates in 2010
Country Plastic waste per year (Mt) Waste per person per day (Kg) Recycled Incinerated (with energy recovery) Landfill (and incineration without energy recovery) Comments
China 59.08 0.12 - - - No official statistics
United States 37.83 0.34 8% 14% 78% Source: EPA
EU total* 24.7 0.15 24% 34% 42%
Germany 14.48 0.48 33% 65% 2%
Brazil 11.85 0.17 - - - No official statistics
Japan 7.99 0.17 27% 49% 24%
Pakistan 6.41 0.10 - - - No official statistics
Nigeria 5.96 0.10 12% 0% 88% Estimated values
Russia 5.84 0.11 6% 0% 94% World bank estimates (2013)
Turkey 5.60 0.21 5% 0% 95% Estimated values
Egypt 5.46 0.18 - - - No official statistics
Indonesia 5.05 0.06 19% 0% 81% Estimated values
United Kingdom 4.93 0.21 23% 8% 69%
Spain 4.71 0.28 23% 17% 60%
France 4.56 0.19 18% 40% 42%
India 4.49 0.01 42% 18% 40% Estimated values
Rest of World 60.76 - - - - No official statistics
World Total 245.00 0.10 16% 22% 62%

* Although not formally a country, legislation affecting recycling is often made at the EU level

Identification codes

See caption
Global plastic waste generation by polymer type. Colours indicate recyclability:
  • Blue is widely recycled
  • Yellow is sometimes recycled
  • Red is usually not recycled
Main article: Resin identification code

Many plastic items bear symbols identifying the type of polymer from which they are made. These resin identification codes (RIC), are used internationally. They were developed in 1988 by the Society of the Plastics Industry (now the Plastics Industry Association) in the United States, but since 2008 have been administered by standards organisation ASTM International.

RICs are not mandatory in all countries, but many producers voluntarily mark their products. More than half of U.S. states have enacted laws that require plastic products be identifiable. The seven codes include six for the most common commodity plastics and one as a catch-all. The EU maintains a similar nine-code list that also includes ABS and polyamides. RICs are based on the recycling symbol, but have drawn criticism, as they imply that marked items are always recyclable when this may not be true.

RICs are not particularly important for single-stream recycling, as these operations are increasingly automated. However, in some countries citizens are required to separate their plastic waste according to polymer type before collection. For instance, in Japan PET bottles are collected separately for recycling.

Plastic identification code Type of plastic polymer Properties Common applications Melting- and glass transition temperatures (°C) Young's modulus (GPa)
Polyethylene terephthalate (PET) Clarity, strength, toughness, barrier to gas and moisture Soft drink, water and salad dressing bottles; peanut butter and jam jars; ice cream cone lids; small non-industrial electronics Tm = 250;
Tg = 76
2–2.7
High-density polyethylene (HDPE) Stiffness, strength, toughness, barrier to gas and moisture Water pipes, gas and fire pipelines, electrical and communications conduits, five gallon buckets, milk, juice and water bottles, grocery bags, some toiletry bottles Tm = 130;
Tg = −125
0.8
Polyvinyl chloride (PVC) Versatility, ease of blending, strength, toughness. Stretch wrap for non-food items, sometimes blister packaging. Non-packaging uses include electrical cable insulation, rigid piping and vinyl records. Tm = 240;
Tg = 85
2.4–4.1
Low-density polyethylene (LDPE) Ease of processing; strength; flexibility; ease of sealing; moisture barrier. Frozen food bags; squeezable bottles, e.g. honey, mustard; cling films; flexible container lids Tm = 120;
Tg = −125
0.17–0.28
Polypropylene (PP) Strength; resistance to heat, chemicals, grease and oil; moisture barrier. Reusable microwaveable ware or take-away containers; kitchenware; yogurt or margarine containers; disposable cups and plates; soft drink bottle caps. Tm = 173;
Tg = −10
1.5–2
Polystyrene (PS) Versatility, clarity, easily formed, easily foamed Egg cartons; disposable cups, plates, trays and cutlery; foam food containers; packing peanuts and package cushioning; Tm = 240 (only isotactic);
Tg = 100 (atactic and isotactic)
3–3.5
Other (often polycarbonate or ABS) Dependent on polymers or combination of polymers Beverage bottles, baby milk bottles. Non-packaging uses for polycarbonate: compact discs, "unbreakable" glazing, electronic apparatus housing, lenses (including sunglasses), instrument panels. Polycarbonate:
Tm = 225
Tg = 145;
Polycarbonate: 2.6; ABS plastics: 2.3

Waste composition

Plastic waste consists of various polymer types. Polyolefins make up nearly 50% of all plastic waste and more than 90% of waste is made of thermosoftening polymers, which can be remelted

Graphs are unavailable due to technical issues. Updates on reimplementing the Graph extension, which will be known as the Chart extension, can be found on Phabricator and on MediaWiki.org.
Global plastic waste by polymer type (2018)
Polymer Waste production (Mt) Percentage of all plastic waste Polymer type Thermal character
High-density polyethylene (HDPE) 64 19.8% Polyolefin Thermoplastic
Low-density polyethylene (LDPE) 45 13.9% Polyolefin Thermoplastic
polypropylene (PP) 62 19.1% Polyolefin Thermoplastic
Polystyrene (PS) 19 5.9% Unsaturated polyolefin Thermoplastic
Polyvinyl chloride (PVC) 17 5.3% Halogenated Thermoplastic
Polyethylene terephthalate (PET) 35 10.8% Condensation Thermoplastic
Polyurethane (PUR) 18 5.6% Condensation Thermoset
PP&A fibers 51 15.7% Condensation Thermoplastic
All Others 12 3.7% Various Varies
Total (excludes additives) 324 100% - -

Collecting and sorting

See caption
Bales of colour sorted PET bottles (blues, clear and greens) Olomouc, the Czech Republic.
Manual separation of co-mingled waste (2 min).
Mixed PET bottles crushed into a bale.

Recycling begins with the collection and sorting of waste. Curbside collection operates in many countries. Waste is sent to a materials recovery facility or MBT plant where the plastic is separated, cleaned and sorted for sale. Unsuitable materials are sent to a landfill or incinerator. These operations account for a large proportion of the financial and energy costs associated with recycling.

Sorting plastic is more complicated than other recyclable materials because it comes in a greater range of forms. For example, glass is separated into three streams (clear, green and amber), metals are usually either steel or aluminum and can be separated using magnets or eddy current separators, and paper is usually sorted into a single stream.

Six types of commodity polymer account for about 75% of plastics waste, with the rest comprising a myriad of polymer types, including polyurethanes and synthetic fibers with a range of chemical structures. Items made from the same type of polymer may be incompatible with each other depending on the additives they contain. Additives are compounds blended into plastics to enhance performance and include stabilisers, fillers and, most significantly, dyes. Clear plastics hold the highest value as they may be dyed after recycling, while black or strongly coloured plastic is much less valuable, because they affect the color of the downstream product. Thus, plastic is typically sorted by both polymer type and colour.

Various sorting approaches and technologies have been developed. They can be combined in various ways. In practice no approach is 100% effective. Sorting accuracy varies between recyclers, producing a market where products are poorly standardised. This inconsistency is another barrier to recycling.

Manual separation

Sorting by hand is the oldest and simplest method. In developing countries this may be done by waste pickers, while in a recycling center, workers pick items off a conveyor-belt. It requires low levels of technology and investment, but has high labor costs. Although many plastic items have identification codes workers rarely have time to look for them, so leaving problems of inefficiency and inconsistency. Even advanced facilities retain manual pickers to troubleshoot and correct sorting errors. Working conditions can be unsanitary.

Density separation

Plastic densities
Plastic Type Density (g/cm)
Polyvinyl chloride 1.38-1.41
Polyethylene terephthalate 1.38-1.41
Polystyrene 1.04-1.08
High-density polyethylene 0.94-0.98
Low-density polyethylene 0.89–0.93
Polypropylene 0.85-0.92
Polystyrene foam 0.01-0.04

Plastics can be separated by exploiting differences in their densities. In this approach the plastic is first ground into flakes of a similar size, washed and subjected to gravity separation. This can be achieved using either an air classifier or hydrocyclone, or via wet float-sink method. These approaches provide partial sorting, as some polymers have similar density. Polypropylene (PP) and polyethylene (PE) are similar as are polyethylene terephthalate (PET), polystyrene (PS), and PVC. In addition, if the plastic contains fillers, this may affect its density. The lighter PP and PE fraction is known as mixed polyolefin (MPO) and can be sold as a low-value product, the heavier mixed plastics fraction is usually unrecyclable.

Electrostatic separation

Main article: electrostatic separator

In electrostatic separators, the triboelectric effect is used to charge plastic particles electrically; with different polymers charged to different extents. They are then blown through an electric field, which deflects them depending on their charge, directing them into appropriate collectors. As with density separation, the particles need to be dry, be uniform in size and shape. Electrostatic separation can be complementary to density separation, allowing full separation of polymers, albeit of mixed colours.

Sensor-based separation

Photograph of the interior workings of a recycling plant
An advanced recycling plant using optical separation
Main article: Sensor-based sorting

This approach is largely automated and involves various sensors linked to a computer, which analyses items and directs them into appropriate chutes or belts. Near-infrared spectroscopy can be used to distinguish polymer types, although black/strongly-coloured plastics, as well as composite materials like plastic-coated paper and multilayered packaging, which can give misleading readings. Optical sorting such as colour sorters or hyperspectral imaging can then split by colour. Sensor based separation is more expensive to install but has the best recovery rates and produces more high-quality products.

Scrap

Plastic waste is either industrial scrap (sometimes referred to as post industrial resin) or consumer waste. Scrap is generated during production and is usually handled differently. It can include flashings, trimmings, sprues and rejects. As it is collected at the point of manufacture it is clean, and of a known type and grade, and is valuable. As scrap is mostly privately traded, it is often not included in official statistics.

Mechanical recycling

Diagram showing plastic or other polymer compatibilisation.
Polymer compatibilisation

The majority of plastic waste is made of thermosoftening polymers, which can be re-melted and reformed into new items via mechanical recycling. Globally, this is by far the most common form of recycling and in many countries it is the only type practised. It is the simplest and most economical technique. It has a lower carbon footprint than other processes. However, several factors can reduce output quality, which limits its applicability.

Plastics are melted at anywhere between 150–320 °C (300–610 °F), depending on polymer type. This is sufficient to cause unwanted chemical reactions that degrade the output. This can produce volatile, low-molecular weight compounds, which may impart undesirable taste or odour, as well as discolouration. Additives can accelerate this degradation. For instance, oxo-biodegradable additives, intended to improve the biodegradability of plastic, also increase the degree of thermal degradation. Flame retardants can similarly have unwanted effects. Product quality also depends strongly on how well the plastic was sorted. Many polymers are immiscible with each other when molten and phase separate (like oil and water) during reprocessing. Products made from such blends contain boundaries between the different polymers with weak cohesion across these boundaries, compromising mechanical properties. In more extreme cases the polymers may degrade each other, particularly with PVC, as it can generate hydrogen chloride which strongly affects condensation polymers such as PET.

Many of these problems have technological solutions, though they bear a financial cost. Advanced polymer stabilisers and can be used to protect plastics from the stress of thermal reprocessing. Volatile degradation products can be removed by a range of devolatilisation techniques. Flame retardants can be removed by chemical treatment, while damaging metallic additives can be rendered inert with deactivators. Finally, the properties of mixed plastics can be improved by using compatibilisers. These are compounds that improve miscibility between polymer types to give a more homogeneous product, with better internal cohesion and improved mechanical properties. They are small-molecules possessing two chemical regions, each of which is compatible with a certain polymer. This allows them to act like molecular-nails or screws, anchoring the polymers to one another. As a result, compatibilisers are normally limited to systems dominated by two particular types of plastic and are not cost-effective for heterogeneous mixtures. No compatibiliser solves all plastic combinations. Even with these technologies, it is particularly challenging to recycle plastic so that it can meet food contact standards.

Closed-loop recycling

In closed-loop, or primary recycling, used plastic is endlessly recycled back into new items of the same quality and type. For instance, turning drinks bottles back into drinks bottles. It can be considered an example of a circular economy. The continual mechanical recycling of plastic without reduction in quality is challenging due to cumulative polymer degradation and risk of contaminant build-up. In 2013 only 2% of plastic packaging was recycled in a closed loop. Although closed-loop recycling has been investigated for many polymers, to-date the only industrial success is with PET bottle recycling. This is because polymer degradation in PET is often repairable. PET's polymer chains tend to cleave at their ester groups and the alcohol and carboxyl groups left by this can be joined back together by the use of chemical agents called chain extenders. Pyromellitic dianhydride is one such compound.

Open-loop recycling

Photograph of a re-usable carrier bag made from recycled plastic bottles processed using open-loop recycling.
This re-usable carrier bag has been made from recycled plastic bottles. It is an example of open-loop recycling

In open-loop recycling, also known as secondary recycling, or downcycling, the quality of the plastic is reduced each time it is recycled, so that the material eventually becomes unrecyclable. It is the most common type. Recycling PET bottles into fleece or other fibres is a common example, and accounts for the majority of PET recycling. Life-cycle assessment shows it to be of ecological benefit. Recycling can displace demand for fresh plastic. However, if it is used to produce items that would not otherwise have been made, then it is not displacing production and is of little or no benefit to the environment.

The reduction in polymer quality can be offset by mixing recycled and new materials. Compatibilised plastics can be used as a replacement for virgin material, as it is possible to produce them with the right melt flow index needed for good results. Low quality mixed plastics can be recycled in an open-loop, although demand for such products is limited. When these are mixed during reprocessing the result is usually an unappealing dark-brown. These blends find use as outdoor furniture or plastic lumber. As the material is weak, but of low cost it is produced in thick planks to provide material strength.

Thermosets

Although thermoset polymers do not melt, technologies have been developed for their mechanical recycling. This usually involves breaking the material down to small particles (crumbs), which can then be mixed with a binding agent to form a composite material. For instance, polyurethanes can be recycled as reconstituted crumb foam.

Feedstock recycling

In feedstock recycling, also called chemical recycling or tertiary recycling, polymers are reduced to their chemical building-blocks (monomers), which can then be polymerised back into fresh plastics. In theory, this allows for near infinite recycling; as impurities, additives, dyes and chemical defects are completely removed with each cycle. In practice, chemical recycling is far less common than mechanical recycling. Implementation is limited because technologies do not yet exist to reliably depolymerise all polymers on an industrial scale and also because the equipment and operating costs are much higher. In 2018 Japan had one of the highest rates in the world at ~4%, compared to 23% mechanical recycling, in the same period Germany, another major recycler, reported a feedstock recycling rate of 0.2%. Depolymerising, purifying and re-polymerising the plastic can also be energy intensive, leading to the carbon footprint of feedstock recycling normally being higher than that of mechanical recycling. PET, PU and PS are depolymerised commercially to varying extents, but the feedstock recycling of polyolefins, which make-up nearly half of all plastics, is much more limited.

Thermal depolymerisation

Certain polymers like PTFE, polystyrene, nylon 6, and polymethylmethacrylate (PMMA) undergo thermal depolymerisation when heated to sufficiently high temperatures. The reactions are sensitive to impurities and require clean and well sorted waste to produce a good product. Even then, not all depolymerisation reactions are completely efficient and some competitive pyrolysis is often observed; the monomers, therefore, require purification before reuse. The feedstock recycling of polystyrene has been commercialised, but global capacity remains fairly limited.

Chemical depolymerisation

Condensation polymers bearing cleavable groups such as esters and amides can be completely depolymerised by hydrolysis or solvolysis. This can be a purely chemical process but may also be promoted by enzymes such as PETase. Such technologies have lower energy costs than thermal depolymerisation but are not available for all polymers. Polyethylene terephthalate has been the most heavily studied polymer, and has reached commercial scale.

Energy recovery

Photograph of piles of trash including large amounts of plastic at an incinerator
Piles of trash including large amounts of plastic at an incinerator in Ko Tao, Thailand. Well regulated incinerators reduce harmful toxins released during the burning process, but not all plastic is burned in proper facilities.

Energy recovery, also called energy recycling or quaternary recycling, involves burning waste plastic in place of fossil fuels for energy production. It is included in the recycling data reported by many countries, although it is not considered recycling by the EU. It is distinct from incineration without energy recovery, which is historically more common, but which does not reduce either plastic production or fossil fuel use.

Energy recovery is often the waste management method of last resort, a position previously held by landfill. In urban areas a lack of suitable sites for new landfills can drive this, but it is also driven by regulation, such as the EU's Landfill Directive or other landfill diversion policies. Compared to the other recycling options, its appeal is largely economic. If the correct technologies are used, then the plastics do not need to be separated, or from other municipal solid waste (garbage), which reduces costs. Compared to the sometimes variable market for recyclables, demand for electricity is universal and better understood, reducing the perceived financial risk. As a means of waste management, it is highly effective, reducing the volume of waste by about 90%, with the residues sent to landfill or used to make cinder block. Although its CO2 emissions are high, comparing its overall ecological desirability to other recycling technologies is difficult. For instance, while recycling greatly reduces greenhouse gas emissions compared to incineration, it is an expensive way of achieving these reductions when compared to investing in renewable energy.

Plastic waste may be burnt as refuse-derived fuel (RDF), or it may be chemically converted to a synthetic fuel first. In either approach PVC must be excluded or compensated for by installing dechlorination technologies, as it generates large amounts of hydrogen chloride (HCl) when burnt. This can corrode equipment and cause undesirable chlorination of fuel products. Burning has long been associated with the release of harmful dioxins and dioxin-like compounds, however these hazards can be abated by the use of advanced combustors and emission control systems. Incineration with energy recovery remains the most common method, with more advanced waste-to-fuel technologies such as pyrolysis hindered by technical and cost hurdles.

Waste-to-fuel

See also: Waste-to-energy

Mixed plastic waste can be depolymerised to give a synthetic fuel. This has a higher heating value than the starting plastic and can be burnt more efficiently, although it remains less efficient than fossil fuels. Various conversion technologies have been investigated, of which pyrolysis is the most common. Conversion can take place as part of incineration in an IGC cycle, but often the aim is to collect the fuel to sell it. Pyrolysis of mixed plastics can give a fairly broad mix of chemical products (between 1 and 15 carbon atoms) including gases and aromatic liquids. Catalysts can give a better-defined product with a higher value. Liquid products can be used as synthetic diesel fuel, with commercial production in several countries. Life-cycle analysis shows that plastic-to-fuel can displace fossil fuels and lower net greenhouse gas emissions (~15% reduction).

Compared to the widespread practise of incineration, plastic-to-fuel technologies have struggled to become economically viable.

Other Uses

Coke replacement

Many kinds of plastic can be used as a carbon source (in place of coke) in scrap steel recycling, with roughly 200,000 tonnes of waste plastics processed each year in Japan.

Construction and concrete

The use of recovered plastics in engineering materials is gaining ground. Ground plastic may be used as a construction aggregate or filler material in certain applications. While generally unsuitable in structural concrete, plastic's inclusion in asphalt concrete, (forming rubberised asphalt), subbase and recycled insulation can be beneficial. An example of this is the construction of plastic roads. These may be made entirely of plastic or can incorporate significant amounts of plastic. The practice is popular in India, which by 2021 had constructed some 700 km (435 miles) of highways. It may allow the leaching of plastic additives into the environment. Research is ongoing to use plastics in various forms in cementitious materials such as concrete. Densifying plastic materials such as PET and plastic bags and then using them to partially replace aggregate and depolymerizing PET to use as a polymeric binder to enhance concrete are under study.

See also

Sources

[REDACTED]  This article incorporates text from a free content work. Licensed under Cc BY-SA 3.0 IGO (license statement/permission). Text taken from Drowning in Plastics – Marine Litter and Plastic Waste Vital Graphics​, United Nations Environment Programme.

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