Editing Essential oil (section)

==Production==
{{main|Extraction (fragrance)}}

===Distillation===
{{see also|Distillation}}
{{references|section|date=November 2022}}

Most common essential oils such as [[Lavandula|lavender]], [[peppermint]], [[tea tree oil]], [[patchouli]], and [[eucalyptus oil|eucalyptus]] are distilled. Raw plant material, consisting of the [[flower]]s, [[leaf|leaves]], [[wood]], [[Bark (botany)|bark]], [[root]]s, [[seed]]s, or [[peel (fruit)|peel]], is put into an [[alembic]] (distillation apparatus) over water. As the water is heated, the steam passes through the plant material, vaporizing the volatile compounds. The vapors flow through a coil, where they condense back to liquid, which is then collected in the receiving vessel.

Most oils are distilled in a single process. One exception is ''ylang-ylang'' (''[[Cananga odorata]]'') which is purified through a [[fractional distillation]].

The recondensed water is referred to as a hydrosol, hydrolat, [[herbal distillate]], or plant water essence, which may be sold as another fragrant product. Hydrosols include [[rose water]], [[lavender]] water, [[lemon balm]], [[clary sage]], and [[orange blossom water]].

===Expression===
Most [[citrus]] peel oils are expressed mechanically or cold-pressed (similar to [[olive oil extraction]]).<ref>{{cite web|title=How Are Essential Oils Extracted?|url=https://naha.org/explore-aromatherapy/about-aromatherapy/how-are-essential-oils-extracted/|last1=Shutes|first1=Jade|website=NAHA – National Association for Holistic Aromatherapy|archive-url=https://web.archive.org/web/20130611075007/https://naha.org/explore-aromatherapy/about-aromatherapy/how-are-essential-oils-extracted/|archive-date=11 June 2013|access-date=16 June 2019}}</ref> Due to the relatively large quantities of oil in citrus peel and low cost to grow and harvest the raw materials, citrus-fruit oils are cheaper than most other essential oils. Lemon or sweet orange oils are obtained as [[byproduct]]s of the citrus industry.

Before the discovery of distillation, all essential oils were extracted by pressing.<ref>{{Cite book|title = The Aromatherapy Handbook: The Secret Healing Power Of Essential Oils|last = Ryman|first = Daniele|publisher = Century Publishing CO. Ltd.|year = 1984|isbn = 978-0-85207-215-8|pages = Chapter 3}}</ref>

===Solvent extraction===
Most flowers contain too little volatile oil to undergo expression, but their chemical components are too delicate and easily denatured by the high heat used in steam distillation. Instead, a [[solvent]] such as [[hexane]] or [[supercritical carbon dioxide]] is used to extract the oils.<ref>{{Cite journal|last1=Aizpurua-Olaizola|first1=Oier|last2=Ormazabal|first2=Markel|last3=Vallejo|first3=Asier|last4=Olivares|first4=Maitane|last5=Navarro|first5=Patricia|last6=Etxebarria|first6=Nestor|last7=Usobiaga|first7=Aresatz|date=2015-01-01|title=Optimization of supercritical fluid consecutive extractions of fatty acids and polyphenols from Vitis vinifera grape wastes|journal=Journal of Food Science|volume=80|issue=1|pages=E101–107|doi=10.1111/1750-3841.12715|issn=1750-3841|pmid=25471637}}</ref> Extracts from [[hexane]] and other hydrophobic solvents are called ''[[Concrete (perfumery)|concretes]]'', which are a mixture of essential oil, [[wax]]es, [[resin]]s, and other [[lipophilic]] (oil-soluble) plant material.

Although highly fragrant, concretes contain large quantities of non-fragrant waxes and resins. Often, another solvent, such as [[ethanol|ethyl alcohol]], is used to extract the fragrant oil from the concrete. The alcohol solution is chilled to {{convert|-18|C|F}} for more than 48 hours which causes the [[wax]]es and [[lipid]]s to precipitate out. The precipitates are then filtered out and the ethanol is removed from the remaining solution by evaporation, vacuum purge, or both, leaving behind the ''[[Absolute (fragrance)|absolute]]''.

Supercritical carbon dioxide is used as a solvent in [[supercritical fluid]] extraction. This method can avoid [[petrochemical]] residues in the product and the loss of some "top notes" when steam distillation is used. It does not yield an absolute directly. The supercritical carbon dioxide will extract both the waxes and the essential oils that make up the concrete.  Subsequent processing with liquid carbon dioxide, achieved in the same extractor by merely lowering the extraction temperature, will separate the waxes from the essential oils.  This lower temperature process prevents the decomposition and denaturing of compounds. When the extraction is complete, the pressure is reduced to ambient and the carbon dioxide reverts to a gas, leaving no residue.

===Production quantities===

Estimates of total production of essential oils are difficult to obtain. One estimate, compiled from data in 1989, 1990, and 1994 from various sources, gives the following total production, in tonnes, of essential oils for which more than 1,000 tonnes were produced.<ref>{{cite web |url= http://isotc.iso.org/livelink/livelink/971087/ISO_TC_054__Essential_oils_.pdf |title= ISO TC 54 Business Plan – Essential oils | access-date= 2006-09-14}} It is unclear from the source what period of time the quoted figures include.</ref>

:{| class="wikitable"
! Oil !! Tonnes
|-
| [[Orange (fruit)|Sweet orange]] || style="text-align:right;"| 12,000
|-
| ''[[Mentha arvensis]]'' || style="text-align:right;"| 4,800
|-
| [[Peppermint]] || style="text-align:right;"| 3,200
|-
| [[Cedrus|Cedar]]wood || style="text-align:right;"| 2,600
|-
| [[Lemon]] || style="text-align:right;"| 2,300
|-
| ''[[Eucalyptus globulus]]'' || style="text-align:right;"| 2,070
|-
| ''[[Litsea cubeba]]'' || style="text-align:right;"| 2,000
|-
| [[Clove]] (leaf) || style="text-align:right;"| 2,000
|-
| [[Spearmint]] || style="text-align:right;"| 1,300
|}