Editing Pyrolysis (section)

=== Waste management===
{{See also|Thermal depolymerization}}
Pyrolysis can also be used to treat municipal solid waste and [[plastic waste]].<ref name="Zhou-2017" /><ref name="Zhou-2015" /><ref name="Zhou-2015-3">{{Cite journal|last1=Zhou|first1=Hui|last2=Long|first2=YanQiu|last3=Meng|first3=AiHong|last4=Li|first4=QingHai|last5=Zhang|first5=YanGuo|date=January 2015|title=Interactions of three municipal solid waste components during co-pyrolysis|journal=Journal of Analytical and Applied Pyrolysis|language=en|volume=111|pages=265–271|doi=10.1016/j.jaap.2014.08.017|bibcode=2015JAAP..111..265Z }}</ref>  The main advantage is the reduction in volume of the waste. In principle, pyrolysis will regenerate the monomers (precursors) to the polymers that are treated, but in practice the process is neither a clean nor an economically competitive source of monomers.<ref>{{cite encyclopedia |first1=Walter |last1=Kaminsky |chapter=Plastics, Recycling |encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |publisher=Wiley-VCH |location=Weinheim |year=2000 |doi=10.1002/14356007.a21_057|isbn=978-3-527-30673-2 }}</ref><ref>N.J. Themelis et al. [http://www.seas.columbia.edu/earth/wtert/sofos/ACC_Final_Report_August23_2011.pdf "Energy and Economic Value of Nonrecyclable Plastics and Municipal Solid Wastes that are Currently Landfilled in the Fifty States" Columbia University Earth Engineering Center] {{webarchive|url=https://web.archive.org/web/20140508231827/http://www.seas.columbia.edu/earth/wtert/sofos/ACC_Final_Report_August23_2011.pdf |date=2014-05-08 }}</ref><ref>{{cite web |url=http://www.alternativesjournal.ca/science-and-solutions/plastic-oil |title=The Plastic to Oil Machine, A\J – Canada's Environmental Voice |work=Alternativesjournal.ca |date=2016-12-07 |access-date=2016-12-16 |archive-date=2015-09-09 |archive-url=https://web.archive.org/web/20150909064711/http://www.alternativesjournal.ca/science-and-solutions/plastic-oil  }}</ref>

In tire waste management, [[Tire recycling#Tire pyrolysis|tire pyrolysis]] is a well-developed technology.<ref name="jid">ผศ.ดร.ศิริรัตน์ จิตการค้า, "ไพโรไลซิสยางรถยนต์หมดสภาพ : กลไกการผลิตน้ำมันเชื้อเพลิงคุณภาพสูง"วิทยาลัยปิโตรเลียมและปิโตรเคมี จุฬาลงกรณ์มหาวิทยาลัย (in Thai) Jidgarnka, S. [http://www.vcharkarn.com/varticle/408 "Pyrolysis of Expired Car Tires: Mechanics of Producing High Quality Fuels"] {{webarchive|url=https://web.archive.org/web/20150220073033/http://www.vcharkarn.com/varticle/408 |date=2015-02-20 }}. Chulalongkorn University Department of Petrochemistry</ref>
Other products from car tire pyrolysis include steel wires, [[carbon black]] and bitumen.<ref>{{cite journal|author1=Roy, C. |author2=Chaala, A. |author3=Darmstadt, H. |title=The vacuum pyrolysis of used tires|journal=Journal of Analytical and Applied Pyrolysis|volume=51|issue=1–2 |pages=201–221|doi=10.1016/S0165-2370(99)00017-0|year=1999}}</ref> The area faces legislative, economic, and marketing obstacles.<ref name="j.rser.2013.02.038">{{cite journal |last1=Martínez |first1=Juan Daniel |last2=Puy |first2=Neus |last3=Murillo |first3=Ramón |last4=García |first4=Tomás |last5=Navarro |first5=María Victoria |last6=Mastral |first6=Ana Maria |title=Waste tyre pyrolysis – A review |journal=Renewable and Sustainable Energy Reviews |date=July 2013 |volume=23 |pages=179–213 |doi=10.1016/j.rser.2013.02.038 |bibcode=2013RSERv..23..179M }}</ref> Oil derived from tire rubber pyrolysis has a high sulfur content, which gives it high potential as a pollutant; consequently it should be desulfurized.<ref>{{cite journal |last1=Choi |first1=Gyung-Goo |last2=Jung |first2=Su-Hwa |last3=Oh |first3=Seung-Jin |last4=Kim |first4=Joo-Sik |title=Total utilization of waste tire rubber through pyrolysis to obtain oils and CO2 activation of pyrolysis char |journal=Fuel Processing Technology |date=July 2014 |volume=123 |pages=57–64 |doi=10.1016/j.fuproc.2014.02.007 }}</ref><ref>{{cite report |doi=10.2172/894989 |osti=894989 |title=Large-Scale Pyrolysis Oil Production: A Technology Assessment and Economic Analysis |date=2006 |last1=Ringer |first1=M. |last2=Putsche |first2=V. |last3=Scahill |first3=J. |url=https://digital.library.unt.edu/ark:/67531/metadc888262/ }}</ref>

Alkaline pyrolysis of sewage sludge at low temperature of 500&nbsp;°C can enhance {{chem|H|2}} production with in-situ carbon capture. The use of NaOH (sodium hydroxide) has the potential to produce {{chem|H|2}}-rich gas that can be used for fuels cells directly.<ref name="Zhao-2019" /><ref name="Zhao-2020" />

In early November 2021, the U.S. State of [[Georgia (U.S. state)|Georgia]] announced a joint effort with Igneo Technologies to build an $85 million large electronics recycling plant in the [[Port of Savannah]]. The project will focus on lower-value, plastics-heavy devices in the waste stream using multiple shredders and furnaces using pyrolysis technology.<ref>{{cite news |last=Leif |first=Dan |url=https://resource-recycling.com/recycling/2021/11/02/igneo-targets-low-grade-scrap-electronics-with-85m-plant/ |title=Igneo targets low-grade scrap electronics with $85M plant |work=resource-recycling.com |date=2021-11-03 |access-date=2021-11-28 }}</ref>

Waste from pyrolysis itself can also be used for useful products. For example, contaminant-rich retentate from liquid-fed pyrolysis of postconsumer multilayer packaging waste can be used as novel building composite materials, which have higher compression strengths (10-12 MPa) than construction bricks and brickworks (7 MPa), as well as 57% lower density, 0.77 g/cm<sup>3</sup> .<ref>{{cite journal |last1=Romani |first1=Alessia |last2=Kulas |first2=Daniel |last3=Curro |first3=Joseph |last4=Shonnard |first4=David R. |last5=Pearce |first5=Joshua M. |date=May 2025 |title=Recycled filtered contaminants from liquid-fed pyrolysis as novel building composite material |journal=Journal of Building Engineering |volume=102 |pages=112025 |doi=10.1016/j.jobe.2025.112025|doi-access=free }}</ref>

==== One-stepwise pyrolysis and Two-stepwise pyrolysis for Tobacco Waste ====
Pyrolysis has also been used for trying to mitigate tobacco waste. One method was done where tobacco waste was separated into two categories TLW (Tobacco Leaf Waste) and TSW (Tobacco Stick Waste). TLW was determined to be any waste from cigarettes and TSW was determined to be any waste from electronic cigarettes.  Both TLW and TSW were dried at 80&nbsp;°C for 24 hours and stored in a desiccator.<ref name="Lee-2021">{{cite journal |last1=Lee |first1=Taewoo |last2=Jung |first2=Sungyup |last3=Lin |first3=Kun-Yi Andrew |last4=Tsang |first4=Yiu Fai |last5=Kwon |first5=Eilhann E. |title=Mitigation of harmful chemical formation from pyrolysis of tobacco waste using CO2 |journal=Journal of Hazardous Materials |date=January 2021 |volume=401 |pages=123416 |doi=10.1016/j.jhazmat.2020.123416 |pmid=32763706 }}</ref> Samples were grounded so that the contents were uniform. Tobacco Waste (TW) also contains inorganic (metal) contents, which was determined using an inductively coupled plasma-optical spectrometer.<ref name="Lee-2021" /> [[Thermogravimetric analysis|Thermo-gravimetric analysis]] was used to thermally degrade four samples (TLW, TSW, [[glycerol]], and [[guar gum]]) and monitored under specific dynamic temperature conditions.<ref name="Lee-2021" /> About one gram of both TLW and TSW were used in the pyrolysis tests. During these analysis tests, {{chem|C|O|2}} and {{chem|N|2}} were used as atmospheres inside of a tubular reactor that was built using quartz tubing. For both [[Carbon dioxide|{{chem|C|O|2}}]] and {{chem|N|2}} atmospheres the flow rate was 100 mL min<sup>−1</sup>.<ref name="Lee-2021" /> External heating was created via a tubular furnace. The pyrogenic products were classified into three phases. The first phase was [[biochar]], a solid residue produced by the reactor at 650&nbsp;°C. The second phase liquid [[hydrocarbon]]s were collected by a cold solvent trap and sorted by using chromatography. The third and final phase was analyzed using an online micro GC unit and those pyrolysates were gases.

Two different types of experiments were conducted: one-stepwise pyrolysis and two-stepwise pyrolysis. One-stepwise pyrolysis consisted of a constant heating rate (10&nbsp;°C min<sup>−1</sup>) from 30 to 720&nbsp;°C.<ref name="Lee-2021" /> In the second step of the two-stepwise pyrolysis test the pyrolysates from the one-stepwise pyrolysis were pyrolyzed in the second heating zone which was controlled isothermally at 650&nbsp;°C.<ref name="Lee-2021" /> The two-stepwise pyrolysis was used to focus primarily on how well {{chem|C|O|2}} affects carbon redistribution when adding heat through the second heating zone.<ref name="Lee-2021" />

First noted was the thermolytic behaviors of TLW and TSW in both the {{chem|C|O|2}} and {{chem|N|2}} environments. For both TLW and TSW the thermolytic behaviors were identical at less than or equal to 660&nbsp;°C in the {{chem|C|O|2}} and {{chem|N|2}} environments. The differences between the environments start to occur when temperatures increase above 660&nbsp;°C and the residual mass percentages significantly decrease in the {{chem|C|O|2}} environment compared to that in the {{chem|N|2}} environment.<ref name="Lee-2021" /> This observation is likely due to the [[Boudouard reaction|Boudouard]] reaction, where we see spontaneous gasification happening when temperatures exceed 710&nbsp;°C.<ref>{{cite journal |last1=Lahijani |first1=Pooya |last2=Zainal |first2=Zainal Alimuddin |last3=Mohammadi |first3=Maedeh |last4=Mohamed |first4=Abdul Rahman |title=Conversion of the greenhouse gas {{chem|C|O|2}} to the fuel gas {{chem|C|O}} via the Boudouard reaction: A review |journal=Renewable and Sustainable Energy Reviews |date=January 2015 |volume=41 |pages=615–632 |doi=10.1016/j.rser.2014.08.034 }}</ref><ref>{{cite journal |last1=Hunt |first1=Jacob |last2=Ferrari |first2=Anthony |last3=Lita |first3=Adrian |last4=Crosswhite |first4=Mark |last5=Ashley |first5=Bridgett |last6=Stiegman |first6=A. E. |title=Microwave-Specific Enhancement of the Carbon–Carbon Dioxide (Boudouard) Reaction |journal=The Journal of Physical Chemistry C |date=27 December 2013 |volume=117 |issue=51 |pages=26871–26880 |doi=10.1021/jp4076965 }}</ref> Although these observations were seen at temperatures lower than 710&nbsp;°C it is most likely due to the catalytic capabilities of inorganics in TLW.<ref name="Lee-2021" /> It was further investigated by doing [[Inductively coupled plasma atomic emission spectroscopy|ICP-OES]] measurements and found that a fifth of the residual mass percentage was Ca species. {{chem|Ca|C|O|3}} is used in cigarette papers and filter material, leading to the explanation that degradation of [[Calcium carbonate|{{chem|Ca|C|O|3}}]] causes pure {{chem|C|O|2}} reacting with [[Calcium oxide|CaO]] in a dynamic equilibrium state.<ref name="Lee-2021" /> This being the reason for seeing mass decay between 660&nbsp;°C and 710&nbsp;°C. Differences in differential thermogram (DTG) peaks for TLW were compared to TSW. TLW had four distinctive peaks at 87, 195, 265, and 306&nbsp;°C whereas TSW had two major drop offs at 200 and 306&nbsp;°C with one spike in between.<ref name="Lee-2021" /> The four peaks indicated that TLW contains more diverse types of additives than TSW.<ref name="Lee-2021" /> The residual mass percentage between TLW and TSW was further compared, where the residual mass in TSW was less than that of TLW for both {{chem|C|O|2}} and {{chem|N|2}} environments concluding that TSW has higher quantities of additives than TLW.&nbsp;
[[File:Pyrolysis.svg|thumb|Production of Hydrogen, Methane, and Tars when creating Biochar]]

The one-stepwise pyrolysis experiment showed different results for the {{chem|C|O|2}} and {{chem|N|2}} environments. During this process the evolution of 5 different notable gases were observed. Hydrogen, Methane, Ethane, Carbon Dioxide, and Ethylene all are produced when the thermolytic rate of TLW began to be retarded at greater than or equal to 500&nbsp;°C. Thermolytic rate begins at the same temperatures for both the {{chem|C|O|2}} and {{chem|N|2}} environment but there is higher concentration of the production of Hydrogen, Ethane, Ethylene, and Methane in the {{chem|N|2}} environment than that in the {{chem|C|O|2}} environment. The concentration of CO in the {{chem|C|O|2}} environment is significantly greater as temperatures increase past 600&nbsp;°C and this is due to {{chem|C|O|2}} being liberated from {{chem|Ca|C|O|3}} in TLW.<ref name="Lee-2021" /> This significant increase in CO concentration is why there is lower concentrations of other gases produced in the {{chem|C|O|2}} environment due to a dilution effect.<ref name="Lee-2021" /> Since pyrolysis is the re-distribution of carbons in carbon substrates into three pyrogenic products.<ref name="Lee-2021" /> The {{chem|C|O|2}} environment is going to be more effective because the {{chem|C|O|2}} reduction into CO allows for the oxidation of pyrolysates to form CO. In conclusion the {{chem|C|O|2}} environment allows a higher yield of gases than oil and biochar. When the same process is done for TSW the trends are almost identical therefore the same explanations can be applied to the pyrolysis of TSW.<ref name="Lee-2021" />

Harmful chemicals were reduced in the {{chem|C|O|2}} environment due to CO formation causing tar to be reduced. One-stepwise pyrolysis was not that effective on activating {{chem|C|O|2}} on carbon rearrangement due to the high quantities of liquid pyrolysates (tar). Two-stepwise pyrolysis for the {{chem|C|O|2}} environment allowed for greater concentrations of gases due to the second heating zone. The second heating zone was at a consistent temperature of 650&nbsp;°C isothermally.<ref name="Lee-2021" /> More reactions between {{chem|C|O|2}} and gaseous pyrolysates with longer residence time meant that {{chem|C|O|2}} could further convert pyrolysates into CO.<ref name="Lee-2021" /> The results showed that the two-stepwise pyrolysis was an effective way to decrease tar content and increase gas concentration by about 10 wt.% for both TLW (64.20 wt.%) and TSW (73.71%).<ref name="Lee-2021" />