What are CO2 Extracts (CO2s)?
CO2 Extracts are produced by using the supercritical carbon dioxide extraction method.
Aromatics extracted by the CO2 (carbon dioxide) method are commonly referred to as CO2 Extracts, CO2 Supercritical Extracts or CO2s for short.
In its normal state, carbon dioxide is a gas that we breathe continually. Using specialized CO2 supercritical extraction equipment, carbon dioxide can be pressurized until it becomes a liquid. The liquid carbon dioxide then acts as a solvent that can dissolve the natural components present in botanical material that is exposed to the liquefied CO2.
Afterwards, the CO2 is brought back to natural pressurization, and the CO2 returns to its normal gaseous state. What remains is the resulting CO2 Extract.
Absolutes are typically solvent extracted using hexane as the solvent. Trace amounts of the hexane may remain in the final absolute. However, with the CO2 method of extraction, CO2 is used as the solvent, and all of the CO2 returns to its normal gaseous state after the extraction is completed.
CO2 Extracts possess an advantage over essential oils because none of the constituents risk damage due to heat incurred during the steam distillation of essential oils.
CO2 Extraction isn't limited to just the production of aromatics. CO2 Extraction can also be used to produce superior lipids (carrier oils) that contain more of the beneficial unsaponifiable materials of the plant that cold pressing isn't able to extract. Even though cold pressed carrier oils are supposed to be pressed at very low temperatures, the friction that occurs can still generate heat during the process. Additionally, not all producers genuinely take the temperature during carrier oil production and still claim the carrier is "cold pressed."
CO2 Extracts are becoming increasingly available through retailers and wholesalers that supply essential oils. Like with essential oils, CO2 Extracts are typically sold in glass bottles. However, some CO2 Extracts are very thick and are sometimes instead sold in small jars. For information on working with thick essential oils and CO2 Extracts, see Using and Blending Thick Aromatic Oils.
Two types of CO2 Supercritical Extracts are generally available:
CO2 Select Extracts
To create a CO2 Select, low pressure is used to liquefy the CO2. CO2 Selects generally contain the volatile (aromatic) components of the botanical that are soluble in liquefied CO2. Aromatic molecules each have their own molecular weight. Some aromatic molecules are too heavy to be present in a steam distilled essential oil. However, some of the heavier aromatic molecules are present in CO2 Selects. Therefore, CO2 Selects often smell closer to the aroma of the natural herb than do some steam distilled essential oils.
CO2 Total Extracts
To create a CO2 Total, much greater pressure is used. CO2 Totals contain all (or most all) of the molecules that are soluble in the liquefied CO2. CO2 Totals tend to be much thicker than CO2 Selects as they not only contain the volatile aromatic CO2 soluble constituents, but they also contain the natural lipids, waxes, and other CO2 soluble molecules present in the botanical. For information on working with thick essential oils and CO2 Extracts, see Using and Blending Thick Aromatic Oils.
CO2 Extract Book Recommendation
For much more information and to view profiles for over 50 CO2 Extracts, I recommend the book CO2 Extracts in Aromatherapy written by Madeleine Kerkhof. Madeleine has been working professionally with CO2 Extracts for over a decade and has a very strong clinical aromatherapy background.