These carbon dioxide methods have a couple of advantages: Like steam distillation, there are no solvent residues left behind, and the resultant product is quite pure. Like solvent extraction, there is no heat applied to the plant material or essential oil to alter it in any way. The oil produced is very accurate with respect to the original state of the plant. The CO2 methods also are the most efficient, producing the most oil per amount of plant (one of the reasons for the high cost of essential oils is the low yield of oil from most plants one ton of Rose petals produces less than 1 pound of oil, for example). The efficiency of CO2 extraction is particularly important when rare or endangered plant species are involved, such as Indian Sandalwood oil less of the precious plant is needed to produce an equivalent amount of oil. Cold Pressing Finally, there is the 'cold pressing' of citrus oils from the peels of fruit, as is done with Bergamot oil, Orange oil , Lemon oil , and the like. This method involves the simple pressing of the rind at about 120 degrees F to extract the oil. Little, if any, alteration from the oil's original state occurs these citrus oils retain their bright, fresh, uplifting aromas like that of smelling a wonderfully ripe fruit. Which Method is Best? CO2's, with some obvious advantages, are not always the best choice for a particular need. They still are the most expensive, despite their higher yields. The resultant product differs slightly compared to one produced another way the oils produced by steam distillation of some plants may sometimes be found to have a more agreeable aroma. Patchouli oil, for example, seems to benefit from the steam distillation process by becoming a little warmer and richer. Many other essential oils are quite effectively produced via steam distillation, with little alteration from the original plant state. Oils from other plant species do seem more 'complete' with CO2 processing, with Frankincense oil and most of the 'spice' oils being good examples where a little something special is present in the aroma. This likely translates to greater therapeautic properties. Producing essential oils of aromatherapeutic grade is skill requiring years of experience. It takes the work of a dedicated artesian at every step, from growing and harvesting to fine-tuning the distillation process, to produce a truly fine oil. The making of a fine essential oil relies far more on knowledge and experience than it does on the particular extraction method. There are, however, legitimate reasons to select one distillation method over another some plants simply require a particular process to produce a fine oil, and the oil needed for a particular application may only be made by one process. In the end, as is often the case in aromatherapy, your own sense of smell can tell you which oil will work best for you.
