CO2 Extractions vs. Classic Essential Oils: A Comparison
The first time I came across a CO2 extraction was nearly 8 years ago in an Apothecary in Denver; it was a lovely example of Ginger Root with a more floral note than the classic steam distillation I was accustomed to. More recently, when I worked at an internet-based apothecary that housed more than 100 oils, I came into relationship with several other examples of CO2 extractions being sold as synonymous to essential oils. These oils were claimed to be “more therapeutic” to classic steam-distilled essential oils based on the lack of heat used in the extraction process. These statements surprised me; what follows are some of my observations explaining why.
Essential Oils by definition, are volatile substances that are naturally produced by the metabolism of plants. It can take anywhere from 50-1600lbs of plant material to produce 16 oz of pure essential oil. While the majority of commercially available essential oils are produced using steam distillation, other processes are used including the cold-pressing process, which is a mechanical process, and hydro-distillation. In classic steam distillation there are two primary vessels stacked on top of one another. The lower vessel holds water which Is heated into steam, this steam passes through the second vessel which holds the plant matter being distilled, thereby breaking the cells within the plant matter which hold the essential oils and freeing them to be carried by way of the steam. At the ceiling of this vessel is a tube which acts as a passive passage collecting steam, which is then routed to descend into a collection flask. This tube is wrapped with a cold-water coiling tube which condenses the steam back into a liquid, resulting in two primary layers… hydrosol and essential oil. The resulting essential oils are light in mass and float on hydrosol, the term defining the resulting fragrant condensed steam, also known as classic flower water. (For further explanation of various extraction processes read here.) It is the tiny molecular size of essential oils which allows them to be carried by steam that also makes them so useful in topical applications. It is also this aspect of size that allows them to be vaporized by a nebulizing diffuser into a fine mist to be distributed through the air, and inhaled with ease.
When one has the opportunity to compare the two extraction processes, that of steam distillation and CO2 extraction, some clear differences can be observed. Let’s compare the two extractions of German Chamomile, for example. German Chamomile essential oil, when it is steam distilled, is a deep blue color due to its azulene content; it is mobile and liquid in its nature. When we examine a CO2 extraction of German Chamomile it is a greenish color, and is the consistency of a thick oil, similar to virgin coconut oil during winter time; it is semi-solid.
The aromatherapy company which sold the various CO2 extractions also sold several mechanisms for using essential oils, and specifically sold a nebulizing diffuser. Often, as a special, different blends and essential oils would be gifted with the purchase of these diffusers. One of the blends had a C02 extracted oil in its formula and for a period of time we received repeated calls from customers complaining that their diffuser seemed clogged with some sort of plug; the customer always declared they used nothing other than essential oils and pure blends they purchased or were gifted with the machine. I reasoned the problem was the due to the CO2 extracted oil. The CO2 extraction process is a solvent process, while it is a clean process… it results in a much thicker product than a classic essential oil. In the CO2 extraction process carbon dioxide is pressurized until it is semi-liquid. This solvent is then allowed to exchange with the plant matter and then simply vaporizes off, being that it is a gas in its natural state. This process allows for manufacturers to freeze plant material and store it prior to processing, and yields an end product that has a viscosity, sometimes including wax, pigments and other plant matter not present in steam distillates. When left to sit open to the air some of the volume of a CO2 extract may volatize, however some have been observed to leave a residue, and in some cases a wax, behind.
It is essential oils' molecular size which allows for them to function so effectively therapeutically. The CO2 extraction yields a larger molecule in its extraction, I would argue that this, combined with the waxy viscosity of their nature, makes them less therapeutic when compared to true essential oils that are classically distilled or cold-pressed, as examples.
Additionally, when considering an inexpensive way to test whether an essential oil is adulterated with another oil, a common method would be to smear the essential oil on a surface or allow a few drops to descend onto a sheet of paper. True essential oils will completely evaporate, with the exception of a deeply colored essential oil such as German Chamomile, which leaves an ink-dye like stain. A CO2 extract, again, leaves a residue…. therefore, the resulting products of CO2 extractions do not meet the definition of an essential oil, being that they are not volatile substances.
Despite CO2 extractions not being equivalent and synonymous to essential oils, this by no means is meant to discredit their nutritional value. It is important, however, to make these distinctions as each extraction process yields a different end resulting product, with a profile within its extraction that is very specific to the process itself.
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