Extracting Essential Oils From Your Home-grown Plants for Fun and Profit!
If you’ve been growing plants for a long time like me, there comes a point where you ask yourself, “can I get more out of this plant?”. It turns out that you can! It’s possible to extract essential oils from your plants if you know where to look and know a little bit of chemistry.
The first most important thing to know is that when you are talking about fragrances or flavors, these are almost always a natural concoction of a few compounds that make the unique smell or taste. For example, there are many compounds that make up what we smell as pine oil, even though pinene is a major component. When extracting, a good distiller knows that you don’t want to just go for the pinene, but also consider the other compounds that may be present (like limonene).
Additionally, the biggest thing to keep in mind when extracting is that there are polar compounds and non-polar compounds. The layman’s way of saying it is, there are compounds that will dissolve in water, but not oil, and there are compounds that will dissolve in oil, but not water. An oil is a non-polar compound, just like waxes and fats are. Because most essences of plants are oils, fats, or waxes, this makes them easily dissolved in other fats, oils, or waxes. Like dissolves like. Non-polar compounds dissolve into other non-polar compounds, just like polar compounds dissolve other polar compounds – water dissolves salts, acids, bases, sugars, and other things; oils can dissolve into fats and waxes (that’s why you can easily make candles out of essential oils – essential oils easily dissolve into wax. In many extractions, the water-soluble (polar) compounds are discarded, as they are generally weaker, fragrance-wise (I think there may be value in keeping them, though they will have to be used separately).
There are a few methods for extracting essential oils, and the video below demonstrates how each of the six methods for oil extraction work.
- Hydro Distillation
- In hydro distillation, the plant matter is boiled in water as a tea, and the steam is collected, cooled, and condensed back into liquid where the oil is at the top. You can see a weak version of this when you boil loose leaf black tea – little oil droplets or an oil rainbow may appear at the top of your tea if it’s strong enough.
- Steam Distillation
- Like hydro distillation, except instead of tea being boiled, steam passes through the dry plant matter. Steam distillation is the most common oil extraction method, but some compounds decompose at steam temperatures. While this is effective in most cases, a good distiller knows which oils are the exceptions for steam distillation and uses another method of extraction to avoid decomposing the product. For example, a good distiller will know that the fragrant oils from a jasmine flower degrade and decompose at low temperatures (before water boils actually), so there would be no yield from steam distillation.
- Solvent Extraction
- This method employs food grade solvents like hexane and ethanol to isolate essential oils from plant material. It is best suited for plant materials that yield low amounts of essential oil, that are largely resinous, or that are delicate aromatics unable to withstand the heat and pressure of steam distillation. This method also produces a finer fragrance than any type of distillation method, as it is possible to concentrate your extraction. The only downside is that there will be trace amounts of solvent in your final product, but if the solvent is removed properly, the trace amounts should be too low to affect much.
- CO2 Extraction
- The holy grail of extraction methods. It’s expensive and requires a lab, but versatile and leaves zero residue. Additionally, because the temperature is usually kept at 95F/35C or lower, you get an extraction with more of the plants components intact (heat can’t damage them). Because carbon dioxide is inert, it is inherently non-polar. This makes it an excellent solvent to dissolve any oil or resin into. With pressurization, we can bring carbon dioxide into its liquid state, pass it through the plant matter, then release the pressure for the carbon dioxide to just evaporate off.
- This is typically used for things with a rind, like citrus.
- One of the oldest methods of extraction is also not as frequently used because of the space and time needed.
For more information on these methods, check out New Directions Aromatics blog and check out this video.
Learning about the properties of aromatic compounds is important. Each class of molecules behaves in a certain way. Terpenes behave differently from phenols, from tannins, etc. There’s not much information on this that’s compiled, but I have found this gem of a site that makes infographics of various compounds and their fragrances. They also have smell profiles of esters and terpenes. If you are looking to try the smell of a compound, you can easily look up its boiling point, find out which plant makes a bunch of it, and you can go have fun extracting. The TGSC Database is an excellent source of compound extraction info as well. I recommend selecting your favorite fragrances in the infographic, looking up the compound, and trying to see if you can extract some to practice your extraction skills.
So, where do I start distilling/extracting essential oils?
If you want high quality extraction and have a little extra to spend, I recommend either this kit or this kit. You will need this adapter to hook up to your sink to run cold water through the condenser. The rest is included in the kit. For the glass connections, a little Vaseline helps. You’ll just need to supply your own solvents. For other kinds of extraction like solvent extraction, you will need a separatory funnel. Watch how to distill below.