Editing Polyethylene (section)

==Environmental issues==
[[File:Polyethylene.jpg|thumb|140px|A recyclable bag manufactured from polyethylene, [[resin identification code]]]]
[[File:Say no to polythene. Sign. Nako, H.P. India.jpg|thumb|''Say no to polythene.'' Sign. [[Nako, Himachal Pradesh]], India.]]
{{See also|Plastic pollution}}
The widespread usage of polyethylene poses potential difficulties for [[waste management]] because it is not readily biodegradable.  Since 2008, Japan has increased plastic recycling, but still has a large amount of plastic wrapping which goes to waste. Plastic recycling in Japan is a potential US$90 [[billion]] market.<ref name="prideaux2007">{{cite news |title=Plastic incineration rise draws ire |first=Eric |last=Prideaux |url=http://www.japantimes.co.jp/text/nn20071103f2.html |newspaper=The Japan Times|date=3 November 2007 |access-date=8 May 2012 |url-status=dead |archive-url=https://web.archive.org/web/20121122082604/http://www.japantimes.co.jp/text/nn20071103f2.html |archive-date=22 November 2012 }}</ref>

It is possible to rapidly convert polyethylene to hydrogen and [[graphene]] by heating. The energy needed is much less than for producing hydrogen by electrolysis.<ref>{{cite journal |last1=Alex Wilkins |title=Waste plastic can be recycled into hydrogen fuel and graphene |journal=New Scientist |date=Sep 29, 2023 |url=https://www.newscientist.com/article/2394144-waste-plastic-can-be-recycled-into-hydrogen-fuel-and-graphene/#}}</ref><ref>{{cite journal|display-authors=etal |last1=Kevin Wyss |title=Synthesis of Clean Hydrogen Gas from Waste Plastic at Zero Net Cost |journal=Advanced Materials |date=Sep 11, 2023 |volume=35 |issue=48 |pages=e2306763 |doi=10.1002/adma.202306763|pmid=37694496 |bibcode=2023AdM....3506763W }}</ref>

===Biodegradability===
Several experiments have been conducted aimed at discovering [[enzyme]] or organisms that will degrade polyethylene. Several plastics - polyesters, polycarbonates, polyamides - degrade either by hydrolysis or air oxidation.  In some cases the degradation is increased by bacteria or various enzyme cocktails.  The situation is very different with polymers where the backbone consists solely of C-C bonds.  These polymers include polyethylene, but also polypropylene, polystyrene and acrylates.  At best, these polymers degrade very slowly, but these experiments are difficult because yields and rates are very slow.<ref name= Enzyme>{{cite journal |doi=10.1021/acs.chemrev.2c00644 |title=Enzymes' Power for Plastics Degradation |date=2023 |last1=Tournier |first1=Vincent |last2=Duquesne |first2=Sophie |last3=Guillamot |first3=Frédérique |last4=Cramail |first4=Henri |last5=Taton |first5=Daniel |last6=Marty |first6=Alain |last7=André |first7=Isabelle |journal=Chemical Reviews |volume=123 |issue=9 |pages=5612–5701 |pmid=36916764 |url=https://hal.science/hal-04150645/file/Andre_Chemical_Reviews_HAL.pdf }}</ref> Further confusing the situation, even preliminary successes are greeted with enthusiasm by the popular press.<ref>{{cite magazine |url=http://www.spiegel.de/wissenschaft/natur/forscherin-entdeckt-zufaellig-plastik-fressende-raupe-a-1144619.html | title=Forscherin entdeckt zufällig Plastik-fressende Raupe| magazine=[[Der Spiegel]]| language=de |date=24 April 2017 |access-date=24 April 2017}}</ref><ref>{{cite news|work=BBC News|author=Briggs, Helen |title=Plastic-eating caterpillar could munch waste, scientists say|url=https://www.bbc.co.uk/news/science-environment-39694553|access-date=24 April 2017}}</ref><ref>{{cite web |url=http://woohooreport.com/2009/09/wci-student-isolates-microbe-that-lunches-on-plastic-bags/ |publisher=The Record.com |title=CanadaWorld – WCI student isolates microbe that lunches on plastic bags |access-date=2014-02-20 |author-first1=Karen|author-last1=Kawawada|url-status=dead |archive-url=https://web.archive.org/web/20110718081923/http://woohooreport.com/2009/09/wci-student-isolates-microbe-that-lunches-on-plastic-bags/ |archive-date=18 July 2011}}</ref> Some technical challenges in this area include the failure to identify enzymes responsible for the proposed degradation.  Another issue is that organisms are incapable of importing hydrocarbons of molecular weight greater than 500.<ref name= Enzyme/>

===Bacteria and insect case studies===


The [[Indian mealmoth]] larvae are claimed to metabolize polyethylene based on observing that plastic bags at a researcher's home had small holes in them. Deducing that the hungry larvae must have digested the plastic somehow, he and his team analyzed their gut bacteria and found a few that could use plastic as their only carbon source. Not only could the bacteria from the guts of the ''Plodia interpunctella'' moth larvae metabolize polyethylene, they degraded it significantly, dropping its tensile strength by 50%, its mass by 10% and the molecular weights of its polymeric chains by 13%.<ref>{{cite web|url=http://www.fondriest.com/news/discovery-plastic-eating-bacteria-may-speed-waste-reduction.htm |date=27 January 2015 |title=Discovery of plastic-eating bacteria may speed waste reduction |first=Lori |last=Balster |publisher=fondriest.com}}</ref><ref>{{cite journal|doi=10.1021/es504038a |pmid=25384056 |title=Evidence of Polyethylene Biodegradation by Bacterial Strains from the Guts of Plastic-Eating Waxworms |journal=Environmental Science & Technology |volume=48 |issue=23 |pages=13776–84 |year=2014 |last1=Yang |first1=Jun |last2=Yang |first2=Yu |last3=Wu |first3=Wei-Min |last4=Zhao |first4=Jiao |last5=Jiang |first5=Lei |bibcode=2014EnST...4813776Y }}</ref>

The caterpillar of ''[[Galleria mellonella]]'' is claimed to consume polyethylene. The caterpillar is able to digest polyethylene due to a combination of its [[gut microbiota]]<ref>{{Cite journal |last1=Cassone |first1=Bryan J. |last2=Grove |first2=Harald C. |last3=Elebute |first3=Oluwadara |last4=Villanueva |first4=Sachi M. P. |last5=LeMoine |first5=Christophe M. R. |date=2020-03-11 |title=Role of the intestinal microbiome in low-density polyethylene degradation by caterpillar larvae of the greater wax moth, Galleria mellonella |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=287 |issue=1922 |pages=20200112 |doi=10.1098/rspb.2020.0112 |issn=0962-8452 |pmc=7126078 |pmid=32126962}}</ref> and its saliva containing [[Enzyme|enzymes]] that oxidise and depolymerise the plastic.<ref>{{Cite journal |last1=Sanluis-Verdes |first1=A. |last2=Colomer-Vidal |first2=P. |last3=Rodriguez-Ventura |first3=F. |last4=Bello-Villarino |first4=M. |last5=Spinola-Amilibia |first5=M. |last6=Ruiz-Lopez |first6=E. |last7=Illanes-Vicioso |first7=R. |last8=Castroviejo |first8=P. |last9=Aiese Cigliano |first9=R. |last10=Montoya |first10=M. |last11=Falabella |first11=P. |last12=Pesquera |first12=C. |last13=Gonzalez-Legarreta |first13=L. |last14=Arias-Palomo |first14=E. |last15=Solà |first15=M. |date=2022-10-04 |title=Wax worm saliva and the enzymes therein are the key to polyethylene degradation by Galleria mellonella |journal=Nature Communications |language=en |volume=13 |issue=1 |pages=5568 |doi=10.1038/s41467-022-33127-w |pmid=36195604 |pmc=9532405 |bibcode=2022NatCo..13.5568S |issn=2041-1723}}</ref>

=== Climate change ===
When exposed to ambient solar radiation the plastic produces trace amounts of two [[greenhouse gas]]es, [[methane]] and [[ethylene]]. The plastic type which releases gases at the highest rate is [[low-density polyethylene]] (LDPE). Due to its low density it breaks down more easily over time, leading to higher surface areas.  When incubated in air, LDPE emits gases at rates ~2 times and ~76 times higher in comparison to incubation in water for methane and ethylene, respectively. However, based on the rates measured in the study methane production by plastics is presently an insignificant component of the global methane budget.<ref>{{cite journal | doi = 10.1371/journal.pone.0200574 | pmid = 30067755 | pmc = 6070199 | title = Production of methane and ethylene from plastic in the environment | journal = PLOS ONE | volume = 13 | issue = 8 | pages = e0200574 | year = 2018 | last1 = Royer | first1 = Sarah-Jeanne | last2 = Ferrón | first2 = Sara | last3 = Wilson | first3 = Samuel T. | last4 = Karl | first4 = David M. | bibcode = 2018PLoSO..1300574R | doi-access = free }}</ref>