What is a CO2 Extract? How Are CO2′s and Essential Oils Different?
What does ‘CO2′ and ‘Super Critical CO2′ mean to the aromatherapist? CO2 extraction is an amazing tool for making some (but not all) oils. And while they share many of the same properties, they’re not called “essential oils”, as that term technically means “steam distilled, hydro-distilled or cold-pressed” aromatic oils. We most certainly love our CO2′s, and here’s a look at what they are and how they fit in the aroma-therapeutic world…
Pure Calendula extract, an extremely useful therapeutic oil for the skin, is available only through CO2 distillation.
In summary, CO2 extraction has the following benefits:
- It’s clean: the process can be certified organic, as most of our CO2 oils & extracts are.
- It’s cool: plant material never reaches the boiling point. This is great for some oils & plants, as many cannot be made via steam distillation.
- It’s efficient: CO2 carries more lipophillic compounds into the final product without the minor loss inherent in steam distillation. It’s more costly to extract via CO2, but you can get more oil out of your plants.
- It’s adjustable: The extractor can change the temperatures and pressures of the extraction process, optimizing changing the chemical profile of the resultant oil, . This can result in “Select” and “Total” extracts, to be explained…
- It’s environmentally friendly: Industrial CO2 for extractions comes from byproducts – primarily hydrogen and ammonia manufacturing and fermentation for ethanol. CO2 used for extractions does not contribute to the overall atmospheric CO2 levels. The CO2 is recycled after each extraction process and used again for the next one.
- Best of All, It Gives Us New Options and Sometimes Better Oils: For some oils, the extraction gives us something a little bit different. Lavender CO2 is not that widely different than the Steam Distilled oil, but is said to be closer to the original plant’s aroma. Cinnamon CO2 & steam distillates are also fairly similar. On the other hand, Frankincense and Myrrh CO2′s are by far our favorites over the steam distilled oils. They’re warmer, smoother, and far more complex.
The CO2 extract of Frankincense resin contains 15% - 30% more compounds in the oil than the steam distilled variety. You can definitely smell the difference!
Let’s look at the CO2 distillation process, and see which oils may be improved via CO2 extraction, which are just different, which are better via steam, and which wouldn’t be available to us at all if it weren’t for CO2!
CO2 Extraction: The Basics
When carbon dioxide is put under extreme pressure and cooled, it becomes a liquid. Under higher pressures, it becomes a ‘supercritical fluid’ which is physically somewhere between a gas and a liquid – think of it as a CO2 “fog”. This is the ‘solvent’ which carries the essential-oil-like compounds away from the raw plant material ~ as opposed to steam and hydro-distillation, the ‘solvent’ is water.
The lower pressure CO2 extraction, where the CO2 is just a simple liquid, involves chilling carbon dioxide to between 35 and 55 degrees F, and pumping it through the plant material at 1000 psi. Supercritical CO2 extraction, where the CO2 becomes like a “fog”, involves the carbon dioxide heated to 87 degrees F and pumped through the plant material at around 8,000 psi.
It’s not that one temperature and pressure setup is better than another, it’s that different parameters are required for each plant. And by further adjusting the temperatures & pressures, different ‘varieties’ of extract can be produced from the same plant material.
What’s the difference between ‘Select’ and ‘Total’ Extracts?
Lavender CO2 'Select' is a favorite for Lavender lovers.
For example, a ‘Select’ CO2 extract is most akin to an essential oil. Using Frankincense as an example, the distiller notes the composition of the Select extract on their Certificate of Analysis as “70 – 85 % essential oil with a high content of alpha-pinene and other monoterpenes like thujene, sabinene, beta-pinene,myrcene, limonene furthermore sesquiterpenes and diterpene alcohols (Incensol, Serratol).”
So for Frankincense, typically there are 15 – 30% MORE ‘oil’ compounds in the CO2 extract than the essential oil, and these are most often heavier, larger molecules not “picked up” by steam. These heavier molecules contribute to a significantly warmer aroma, with an overall deeper tone. Frankincense was the first CO2 extract to be recognized by “medical” aromatherapists world wide as potentially “more therapeutic” because of the presence of these larger sesquiterpenes and diterpene alcohols…this is also the case with Myrrh – the CO2 Select is so very wonderful, warm and rich, and a very worthwhile experience. (Continued below…)
About CO2 Total Extracts
A Frankincense ‘Total” extract is not produced at all by any CO2 distiller – one would end up with a gummy mass not much different than the resin itself. But a “Total” extract is just what’s called for in cases such as Sea Buckthorn, Rosehip and Calendula. No steam distilled version of them even exists! The higher pressure and temperature “total” process extracts all the “oils” from these plant materials.
Some Incredible Plant Extracts ONLY Available as CO2′s
The extracts of whole Rosehips, whole Sea Buckthorn Berries, and even Calendula flowers don’t have strong aromas, as they don’t contain much lighter, smaller aromatic molecules such as mono-terpenes. However, they do contain fatty acids – whole rosehips are not only rich in deep-red phytonutrients, but they also contain the oils from the seeds inside. ALL these lipophillic compounds are extracted in a CO2 “Total”. Together, these are absolute MAGIC skin care ingredients, as you can imagine!
Until CO2 extraction, Calendula was available only as an infusion – one had to soak Calendula flowers in olive oil for months to extract the skin-healing nutrients into the carrier oil. Now, you can just add a few drops of Calendula CO2 to any blend and Voila! A Calendula “infusion” in minutes…
The Spice Oils – Viva la Difference!
Many ‘spice’ oils seem to have a fuller aroma, with more pronounced middle and lower tones when CO2 distilled. Yet the changes in the therapeutic values depend on the oil itslef — while Cinnamon CO2 and steam distilled varities are very similar, Ginger, for example, is quite different depending on the distillation technique. Its benefit to the digestive system is best received from the steam distilled variety, whereas the CO2 oil is best for its anti-inflammatory properties.
The CO2 extract of Rosemary is the perfect antioxidant / preservative for your essential oil blends.
Rosemary CO2 is SPECIFICALLY extracted for its unique anti-oxidant action: it is the only known compound to quench EVERY one of the seven classes of oxidative radicals (we’ll skip the chemistry…we’ll just let you know that we actually put this in capsules to take it as as supplement for this purpose…note it is NOT an essential oil, but a CO2 extract meant only to derive the strong anti-oxidant properties from the plant).
This makes a great addition to any formula with a carrier oil. Just add one to two drops of Rosemary CO2 for every ounce of blend – it’s aroma is very, very light, and is typically undetectable at such low concentrations.
One other commonly used oil which stands out as “better” therapeutically is German Blue Chamomile. The heat of the steam process converts the stronger anti-inflammatory molecule of Matricin (the blue-green compound in the oil) to the weaker Chamazulene (the inky-blue compound in the oil). But truly, there are only a few oils where CO2 distillation produces a better product over steam distillation. These can be almost completely summed up in Frankincense & Myrrh, the Spice oils, German Chamomile, and the oils where they would otherwise not exist: whole Sea Buckthorn Berry, whole Rosehip, & Calendula.
But CO2′s Are Not Always Better…Oftentimes, They’re Just Different…
And then there’s many oils which are just different. Not even really therapeutically different, but aromatically different. Patchouli is a great example…the CO2 is somewhat “green” smelling, like a freshly distilled Patchouli. You may know that Patchouli really gets better with age, and while some folks may enjoy the CO2′s aroma, it hasn’t hit it big.
Lavender is probably the best example of an oil simply being ‘different’. As some linalyl-acetate is converted to linalool in the steam distillation process, the plant’s natural aroma profile is changed. We do use the Lavender CO2 in ingestable formulas, as it is the form found in lavender capsules, though the science doesn’t really point to one form being advantageous over another. You may or may not prefer the aroma, and it’s certainly worth the experience.
Carrier Oils & the Future of CO2′s
One very strong point for CO2′s is the extended shelf life of carrier oils extracted using this method. Borage Seed and Evening Primrose oils are excellent examples. These are extremely delicate, and the cold-pressed varieties do require attention to keep them away from light and heat. The CO2-extracted varieties are much less susceptible to oxidation – though there costs are almost prohibitively high, but are coming down.
At Ananda, we plan to continue to expand our CO2 offerings, and do our best at explaining why you might choose a CO2 over a steam distillate for a particular oil variety. They’re really all worth experiencing – Our owner is dearly in love with his newfound favorite ‘therapeutic cologne’ of Frankincense Carteri & Seratta CO2′s, Myrrh CO2 and Indian Sandalwood. Sandalwood CO2′s are only “interesting”, and haven’t topped the aroma of a good steam distilled variety, yet.
Thank you for reading! We hope you find the information helpful in your Aromatherapeutic journey!