Editing Ethanol (section)

== Production ==
[[File:Ethanol Flasche.jpg|thumb|upright|94% denatured ethanol sold in a bottle for household use]]

Ethanol is produced both as a [[petrochemical]], through the hydration of [[ethylene]] and, via biological processes, by fermenting [[sugar]]s with [[yeast]].<ref name="Mills-Ecklund">{{cite journal | vauthors=Mills GA, Ecklund EE | title=Alcohols as Components of Transportation Fuels | journal=[[Annual Review of Energy]] | volume=12 | pages=47–80 | year=1987 | doi=10.1146/annurev.eg.12.110187.000403 | doi-access=free}}</ref> Which process is more economical depends on prevailing prices of [[petroleum]] and grain feed stocks.

=== Sources ===
World production of ethanol in 2006 was {{convert|51|GL|usgal}}, with 69% of the world supply coming from Brazil and the U.S.<ref name="Renewable Fuels Association-2008" /> Brazilian ethanol is produced from sugarcane, which has relatively high yields (830% more fuel than the fossil fuels used to produce it) compared to some other [[energy crop]]s.<ref name="WaPo-Brazil">{{cite news | date=19 August 2006 | title=Brazil's Road to Energy Independence | newspaper=[[The Washington Post]] | url=https://www.washingtonpost.com/wp-dyn/content/article/2006/08/19/AR2006081900842.html | vauthors=Reel M}}</ref> Sugarcane not only has a greater concentration of sucrose than corn (by about 30%), but is also much easier to extract. The [[bagasse]] generated by the process is not discarded, but burned by power plants to produce electricity. Bagasse burning accounts for around 9% of the electricity produced in Brazil.<ref>{{Cite journal | last1=Rossi | first1=Liane M. | last2=Gallo | first2=Jean Marcel R. | last3=Mattoso | first3=Luiz H. C. | last4=Buckeridge | first4=Marcos S. | last5=Licence | first5=Peter | last6=Allen | first6=David T. | date=2021-03-29 | title=Ethanol from Sugarcane and the Brazilian Biomass-Based Energy and Chemicals Sector | journal=ACS Sustainable Chemistry & Engineering | language=en | volume=9 | issue=12 | pages=4293–4295 | doi=10.1021/acssuschemeng.1c01678 | s2cid=233676614 | issn=2168-0485 | doi-access=free}}</ref>

In the 1970s most industrial ethanol in the U.S. was made as a petrochemical, but in the 1980s the U.S. introduced subsidies for [[corn-based ethanol]].<ref name="WittcoffReuben2004">{{cite book | last1=Wittcoff | first1=Harold A. | url={{google books | plainurl=y | id=4KHzc-nYPNsC | page=136}} | title=Industrial Organic Chemicals | last2=Reuben | first2=Bryan G. | last3=Plotkin | first3=Jeffery S. | publisher=John Wiley & Sons | year=2004 | isbn=978-0-471-44385-8 | pages=136– | name-list-style=vanc}}</ref> According to the Renewable Fuels Association, as of 30 October 2007, 131 grain ethanol bio-refineries in the U.S. have the capacity to produce {{convert|7|e9USgal|m3|abbr=on}} of ethanol per year. An additional 72 construction projects underway (in the U.S.) can add {{convert|6.4|e9USgal|m3}} of new capacity in the next 18 months.<ref name="rfa1" />

In India ethanol is made from sugarcane.<ref>{{Cite book | last=Swami | first=V. N. | publisher=Vidyabharti Publication | year=2020 | location=[[Latur]], Maharashtra, India | page=119 | language=mr | script-title=mr:विद्याभराती जिल्हा मध्यवर्ती सहकारी बँक भारती परीक्षा मार्गदर्शक | trans-title=Vidyabharti District Co-operative Bank recruitment examination guide (Bank clerk grade examination)}}</ref> [[Sweet sorghum]] is another potential source of ethanol, and is suitable for growing in dryland conditions. The [[International Crops Research Institute for the Semi-Arid Tropics]] is investigating the possibility of growing sorghum as a source of fuel, food, and animal feed in arid parts of [[Asia]] and [[Africa]].<ref>{{Cite web | title=Sweet sorghum for food, feed and fuel | date=January 2008 | website=New Agriculturalist | url=http://resourcespace.icrisat.ac.in/filestore/8/4/0_6c06c9b61b19c20/840_be710da94740b90.pdf | access-date=2023-03-11 | archive-url=https://web.archive.org/web/20150904014010/http://resourcespace.icrisat.ac.in/filestore/8/4/0_6c06c9b61b19c20/840_be710da94740b90.pdf | archive-date=4 September 2015}}</ref> Sweet sorghum has one-third the water requirement of sugarcane over the same time period. It also requires about 22% less water than corn. The world's first sweet sorghum ethanol distillery began commercial production in 2007 in [[Andhra Pradesh]], [[India]].<ref>[http://exploreit.icrisat.org/sites/default/files/uploads/1378281395_DevelopingASweetSorghum_2013.pdf "Developing a sweet sorghum ethanol value chain"] {{Webarchive|url=https://web.archive.org/web/20140223044045/http://exploreit.icrisat.org/sites/default/files/uploads/1378281395_DevelopingASweetSorghum_2013.pdf |date=23 February 2014 }}. [[ICRISAT]], 2013</ref>

Ethanol has been produced in the laboratory by converting [[carbon dioxide]] via biological and [[electrochemical]] reactions.<ref>{{cite journal | vauthors=Liew F, Henstra AM, Köpke M, Winzer K, Simpson SD, Minton NP | title=Metabolic engineering of Clostridium autoethanogenum for selective alcohol production | journal=Metabolic Engineering | volume=40 | pages=104–114 | date=March 2017 | pmid=28111249 | doi=10.1016/j.ymben.2017.01.007 | pmc=5367853}}</ref><ref>{{Cite news | url=https://newscenter.lbl.gov/2017/09/18/solar-fuel-system-recycles-co2-for-ethanol-ethylene/ | title=Solar-to-Fuel System Recycles CO2 for Ethanol and Ethylene | date=18 September 2017 | work=News Center | access-date=19 September 2017 | language=en-US}}</ref>

{{block indent|CO<sub>2</sub> + {{chem|H|2|O}} → {{chem|CH|3|C|H|2|O}}H + side products}}

=== Hydration ===
Ethanol can be produced from petrochemical feed stocks, primarily by the [[acid]]-[[catalysis|catalyzed]] [[Hydration reaction|hydration]] of ethylene. It is often referred to as synthetic ethanol.

:{{chem2| C2H4 + H2O -> C2H5OH }}

The catalyst is most commonly [[phosphoric acid]],<ref name="r_and_c">{{cite book | last1=Roberts | first1=John D. | last2=Caserio | first2=Marjorie C. | name-list-style=vanc | author-link1=John D. Roberts | author-link2=Marjorie Constance Caserio | year=1977 | publisher=W. A. Benjamin | title=Basic Principles of Organic Chemistry | isbn=978-0-8053-8329-4 | url=https://archive.org/details/basicprincipleso1977obe}}{{page needed|date=February 2014}}</ref><ref name="ullmann" /> [[adsorption|adsorbed]] onto a porous support such as [[silica gel]] or [[diatomaceous earth]]. This catalyst was first used for large-scale ethanol production by the [[Shell Oil Company]] in 1947.<ref name="ECT4 820">{{cite encyclopedia | chapter=Ethanol | title=Encyclopedia of chemical technology | year=1991 | page=82 | volume=9}}</ref> The reaction is carried out in the presence of high pressure steam at {{convert|300|C|F}} where a 5:3 ethylene to steam ratio is maintained.<ref>[http://www.essentialchemicalindustry.org/chemicals/ethanol.html "Ethanol"] {{Webarchive|url=https://web.archive.org/web/20150113175914/http://www.essentialchemicalindustry.org/chemicals/ethanol.html |date=13 January 2015 }}. ''Essential Chemical Industry''.</ref><ref>{{cite web | last=Harrison | first=Tim | date=May 2014 | url=http://www.chemlabs.bris.ac.uk/outreach/resources/Catalysis%20Web%20Pages%20for%20PreUniversity%20students%20V1_0.pdf | title=Catalysis Web Pages for Pre-University Students V1_0 | archive-url=https://web.archive.org/web/20210305074612/http://www.chemlabs.bris.ac.uk/outreach/resources/Catalysis%20Web%20Pages%20for%20PreUniversity%20students%20V1_0.pdf | archive-date=5 March 2021 | website=Bristol ChemLabs, School of Chemistry | publisher=University of Bristol}}</ref> This process was used on an industrial scale by [[Union Carbide]] Corporation and others. It is no longer practiced in the US as fermentation ethanol produced from corn is more economical.<ref>{{Cite web | last=Tullo | first=Alexander | date=2021-08-26 | title=Last synthetic ethanol plant in US to close | url=https://cen.acs.org/energy/biofuels/Last-synthetic-ethanol-plant-US/99/i31 | access-date=2022-11-22 | website=cen.acs.org}}</ref>

In an older process, first practiced on the industrial scale in 1930 by Union Carbide<ref name="ECT4 817">{{cite book | last=Lodgsdon | first=John E. | chapter=Ethanol | editor1-last=Howe-Grant | editor1-first=Mary | editor2-last=Kirk | editor2-first=Raymond E. | editor3-last=Othmer | editor3-first=Donald F. | editor4-last=Kroschwitz | editor4-first=Jacqueline I. | title=Encyclopedia of chemical technology | publisher=Wiley | location=New York | year=1991 | isbn=978-0-471-52669-8 | edition=4th | volume=9 | page=817}} Republished as {{cite book | last=Lodgsdon | first=John E. | chapter=Ethanol | date=4 December 2000 | editor-last=Seidel | editor-first=Arza | title=Kirk-Othmer Encyclopedia of Chemical Technology | edition=5th | publisher=Wiley | isbn=978-0-471-48494-3 | doi=10.1002/0471238961.0520080112150719.a01}}</ref> but now almost entirely obsolete, ethylene was hydrated indirectly by reacting it with concentrated [[sulfuric acid]] to produce [[ethyl sulfate]], which was [[hydrolyzed]] to yield ethanol and regenerate the sulfuric acid:<ref name="s_and_h" />

:{{chem2| C2H4 + H2SO4 -> C2H5HSO4 }}
:{{chem2| C2H5HSO4 + H2O -> H2SO4 + C2H5OH }}

=== Fermentation ===
{{more citations needed section|date=November 2024}}
{{Main|Ethanol fermentation|Cellulosic ethanol}}
{{See also|Yeast in winemaking}}
Ethanol in [[alcoholic beverage]]s and fuel is produced by fermentation. Certain species of yeast (e.g., ''[[Saccharomyces cerevisiae]]'') metabolize sugar (namely [[polysaccharide]]s), producing ethanol and carbon dioxide. The chemical equations below summarize the conversion:

{{block indent|[[glucose|{{chem|C|6|H|12|O|6}}]] → 2 {{chem|CH|3|C|H|2|O}}H + 2 CO<sub>2</sub>}}
{{block indent|[[sucrose|{{chem|C|12|H|22|O|11}}]] + {{chem|H|2|O}} → 4 {{chem|CH|3|C|H|2|O}}H + 4 CO<sub>2</sub>}}

Fermentation is the process of culturing yeast under favorable thermal conditions to produce alcohol. This process is carried out at around {{convert|35|-|40|C|F}}. Toxicity of ethanol to yeast limits the ethanol concentration obtainable by brewing; higher concentrations, therefore, are obtained by [[Fortified wine|fortification]] or [[distillation]]. The most ethanol-tolerant yeast strains can survive up to approximately 18% ethanol by volume.

To produce ethanol from starchy materials such as [[cereal]]s, the [[starch]] must first be converted into sugars. In brewing [[beer]], this has traditionally been accomplished by allowing the grain to germinate, or [[malt]], which produces the [[enzyme]] [[amylase]]. When the malted grain is [[mashing|mashed]], the amylase converts the remaining starches into sugars.

Sugars for [[ethanol fermentation]] can be obtained from [[cellulose]]. Deployment of this technology could turn a number of cellulose-containing agricultural by-products, such as [[corncob]]s, [[straw]], and [[sawdust]], into renewable energy resources. Other agricultural residues such as sugarcane bagasse and energy crops such as [[switchgrass]] may also be fermentable sugar sources.<ref>{{cite web | last=Clines | first=Tom | name-list-style=vanc | title=Brew Better Ethanol | publisher=Popular Science Online | date=July 2006 | url=http://www.popsci.com/popsci/energy/6756226d360ab010vgnvcm1000004eecbccdrcrd.html | archive-url=https://web.archive.org/web/20071103083747/http://www.popsci.com/popsci/energy/6756226d360ab010vgnvcm1000004eecbccdrcrd.html | archive-date=3 November 2007}}</ref>

=== Testing ===
[[File:EthanolMIRInfraredSpectra.PNG|class=skin-invert-image|thumb|upright=1.35|Infrared reflection spectra of liquid ethanol, showing the −OH band centered near 3300&nbsp;cm<sup>−1</sup> and C−H bands near 2950&nbsp;cm<sup>−1</sup>]]
[[File:Ethanol near IR spectrum.png|class=skin-invert-image|thumb|upright=1.35|[[Near-infrared spectrum]] of liquid ethanol]]

Breweries and [[biofuel]] plants employ two methods for measuring ethanol concentration. Infrared ethanol sensors measure the vibrational frequency of dissolved ethanol using the C−H band at 2900&nbsp;cm{{sup|−1}}. This method uses a relatively inexpensive solid-state sensor that compares the C−H band with a reference band to calculate the ethanol content. The calculation makes use of the [[Beer–Lambert law]]. Alternatively, by measuring the density of the starting material and the density of the product, using a [[hydrometer]], the change in specific gravity during fermentation indicates the alcohol content. This inexpensive and indirect method has a long history in the beer brewing industry.