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Details About CO2 Extraction

What is CO2 Extraction?

My respected colleague, Susan Renkel at Changes Within shared the following some time ago on one of the Aromatherapy Lists. She graciously gave me permission to quote her rather than reinvent the wheel.

Carbon Dioxide Extracts

Hypercritical carbon dioxide extraction is a relatively new process used to extract the essence of the plant. When a certain amount of pressure is applied to CO2 (carbon dioxide) this gas turns into liquid. This liquid CO2 can be used as a very inert, safe, “liquid solvent.” CO2 is the gas we all breathe out of our lungs. It is also the gas that plants themselves thrive on. Essential oils extracted in this way have the added benefit of avoiding the thermal degradation associated with distillation at atmospheric pressure. Two types of materials are obtained by this CO2 method:

Essential Oils or CO2 Selects: are obtained at relatively low CO2 pressure and contain only volatile, CO2 soluble components. These tend to resemble the classic steam distillate but with the advantage of no temperature degradation and the potential for additional volatile substances that may not be distilled out of the plant under normal steam distillation. The consistency of the essential oils extracted with the CO2 method will vary from batch to batch just as the plants themselves vary and just as steam distilled oils vary. Naturally, there is also the extraction process itself and the actual processor to consider.

Extracts Called “Totals:” are obtained at higher CO2 pressures and contain all CO2 soluble components, including waxes, resins, colorants, resembling a classical hexane extract, with the advantage of no solvent residue. These totals are very very much like the herb itself. CO2 totals are usually thick and pasty due to the beneficial fats, resins, and waxes they contain that come from the plant material itself. These totals are soluble in essential oils and vegetal oils. Some, such as rosemary verbenone must be warmed with the vegetal oil or by itself and then quickly added to warm oil in order to be soluble. It is the same thing for some of the others like sea buckthorn berry or vanilla CO2. Even small percentages of (.05% to 1%) of these CO2 extracts can be excellent additions to body oils, creams, ointments, lotions, balms, soaps, or essential oil blends. Because of the sometimes thick, pasty nature of these CO2 oils, they should not be used in a nebulizer type diffuser. They could clog your diffuser.


These potent extracts are wonderful for cosmetics and pharmaceuticals. The calendula extracts, for example, in a dosage of 2 grams extract to 1000 grams ointment is effective for its anti-inflammatory and anti-microbial activity. The chamomile CO2 extract or “total” contains 6% bisabolol and 2.8% matricin. The matricin is not degraded to chamazulene. Chamazulene has only one tenth of the anti-inflammatory activity as matricin.

CO2 extracts have a minimum shelf life of one year. They should be kept under the same conditions as steam distilled essential oils...that is in a cool, dark place, in full glass containers.

Hypercritical carbon dioxide extraction appears to be an aromatherapist’s (and herbalist’s) dream come true (in some respects). Unlike the products produced by regular solvents (absolutes and concretes) the solvent (CO2) can be easily and totally removed, just by releasing the pressure in the extraction chamber. This process, because it happens in a closed chamber, can then collect the most volatile and most fragile fractions of the fragrance and plant. The end result; an extract as close to the natural essence of the plant that anyone has achieved, except perhaps, the new “florasols” that Peter Wilde is producing.

This information is copyrighted by Susan Renkel RN / 1998 and can not be reproduced by any means without express written permission by the author.


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