Hypercritical carbon dioxide extraction is a relatively new process used to extract the essence of the plant. Oils extracted by the CO2 (carbon dioxide) method are commonly called CO2 Extracts or CO2s for short. In a nutshell, CO2 Extracts are extracted by pressurizing carbon dioxide until it becomes a liquid. The liquid carbon dioxide then acts as a solvent on the natural plant matter and the essential oil content then dissolves into the liquid CO2. Afterwards, the CO2 is brought back to natural pressurization, the CO2 evaporates back into its gaseous state and what is left is the resulting oil.

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 extracts are often labeled as essential oils as opposed to absolutes since no trace of a harmful solvent will remain in the final product. CO2s have an advantage over essential oils because none of the constituents of the oil are damaged by heat.

CO2 extracts are usually thicker than their essential oil counterparts and often smell closer to the aroma of the natural herb. CO2 extracts have been said to contain additional constituents than what is extracted from the same plant using steam distillation. This would seem to make sense since CO2 extracts generally are thicker oils and often seem to have a more rounded aroma.

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 Calendulas extract, for example, in a dosage of 2 grams extract to 1000 grams ointment is effective for it's 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 amber 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 achieve.

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