Essential Oil Extraction Methods
Overview
There are several different ways that the essential oils are removed from the plant. When it comes to using therapeutic essential oils, be sure to only look for steam distilled or CO2 extracted oils. Some oils are solvent extracted, and you should not use these on your body or for therapeutic purposes. This is because the chemical solvents used for extracting the oil can never be fully removed from the essential oil and thus will still be in your bottle of essential oil.
Steam Distillation
Most essential oils are obtained through steam distillation. Aromatic plant material is harvested and put into a canister or still through which steam rises. The steam gently lifts the volatile oil from the plant material. The steam and vaporous oil pass into a condenser coil that cools the steam and vaporous oil down into a liquid. The liquid pours into a flask where the essential oil naturally separates and floats on top of the water.
- Still
- Cowl
- Swan neck
- Condenser coil
- Receiver flask
- Plant material
- Steam & vaporous essential oil
- Steam inlet
- Condenser
- Circulation of cold water (in)
- Circulation of cold water (out)
- Essential oil layer
- Floral water layer (aromatic water)
Each plant has its own unique characteristics and will yield its best oil to those distillers who have learned the subtle techniques through many seasons of experience. Distillation of high quality therapeutic grade essential oils requires the correct balance of time and temperature to release the most valuable molecules from the plant material without destroying them. This careful process can take much longer than some producers are willing to spend, but it allows the plant to release its full depth of aromatic complexity.
Typical distillations will produce only a 1 to 2% yield of essential oil from the plant material. Many oil producers choose to employ a heavy-handed distillation process to save time and boost essential oil yields, producing a lesser quality essential oil. Hexane and other harsh chemical solvents are also commonly used to further increase yield and production efficiency, which must be removed with added steam. However, residual solvents will always remain in the end product, resulting in an adulterated essential oil. Therefore, looking for steam distilled oils does not guarantee they will be free from chemical solvents. E.O.B.B.D. testing will show if a chemical solvent was used when extracting the oils. This would be one factor for disqualifying an essential oil (it would not meet EOBBD quality).
CO2 Extraction
Carbon dioxide or CO2 extraction is sometimes used in special circumstances. The process is called Supercritical Fluid Extraction (CFE) and uses CO2 under very high pressure with specialized equipment. The resulting form of CO2 has unique properties of both a liquid and a gas, making it a powerful extraction vehicle. Because CO2 is a safe and ubiquitous gas, it simply evaporates at the end of the extraction process, leaving no residues behind. Depending on the process conditions, CO2 extraction may employ lower temperatures than traditional steam distillation. While CO2 extraction can yield an essential oil with a more complete and complex array of constituents, the process is prohibitively expensive for most consumer uses.
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