Subcritical/Supercritical CO2 oil extraction has several advantages over other extraction mediums, such as alcohol and hydrocarbons:
- CO2 is nontoxic and is Generally Regarded As Safe (GRAS) by the FDA for use in food products. Our bodies produce it when we breathe, and it is commonly used in carbonated beverages. With CO2 as a solvent for oil extraction, no toxins, heavy metals or hydrocarbon materials come in contact with the extracted oils.
- CO2 is “solvent free”. Other extraction solvents, such as hydrocarbon based propellants like propane and butane, hexane and pentane, or ethanol/alcohol mixtures require additional distillation or purging beyond the extraction process to separate the solvent from the extracted oil. CO2 has a very low boiling temperature and wants to be a gas a room temperature, thus it naturally separates from the extracted oil the same way a soda goes “flat”. The spent plant material is also free of residual solvents so it can be re-used as well.
- CO2 is non-flammable. Flammable solvents must be processed in a NEMA Class 1, Division 1, 2 or 3 (explosion proof) environment. CO2 is not flammable and does not require costly explosion proof facilities.
- CO2 is “cold” – Botanical oil extractions can be done at temperatures that are native to the botanical material, minimizing thermal degradation of the plant material and the extracted oil.
- CO2 is “tunable” – the solvency power of CO2 can be adjusted simply by increasing or decreasing pressures and/or temperatures. The ability of the CO2 to selectively extract affords the ability to create unique extractions that have varying levels of desirable oils and waxes (see below). Less desirable plant constituents, like chlorophyl, can also be “de-selected”.
- CO2 is inexpensive. CO2 is readily available and widely used throughout several industries. In addition, Apeks’ production CO2 oil extraction systems recirculate and subsequently recover 95% of the CO2 used in each extraction.
- CO2 is 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.
Comparing CO2 extraction vs. butane or propane? Don’t forget to include the facility cost for processing with a compressed flammable gas: http://www.havelickindustrialhygiene.com/files/BHOfacility.pdf
FAQ: What is the difference between Supercritical and Subcritical CO2 extraction?
CO2 is a unique solvent because it has the ability to change its solvency power simply by adjusting the temperature and pressure of the CO2 during the extraction. When the pressure and temperature of the CO2 are above 1083psi and 88F, the CO2 is considered “supercritical”. If the temperature is dropped below 88F the CO2 changes to a liquid and referred to as “subcritical”. Both supercritical CO2 and subcritical CO2 act like a solvent and can extract oil from plant materials. When the pressure of the CO2 is decreased (typically to below 600psi) it converts to a gas and loses its ability to hold oils in solution and separates the extracted oil from the now gaseous CO2.
With respect to plant oil extractions, subcritical CO2 has lower solvency power and thus tends to pull mostly lighter oils and leave behind most waxes, paraffin and resins. Subcritical CO2 is also relatively cold and thus is very effective at extracting temperature sensitive volatile oils. Subcritical CO2 is great at extracting and preserving light oils from the plant material, but extraction times can be longer and yields are generally lower due to the fact that there will still be residual waxes and resins that are left behind in the plant material.
Supercritical CO2 can be a much stronger solvent than subcritical CO2 and in addition to extracting the lighter oils, supercritical CO2 can also extract the higher molecular weight materials (like waxes, parafins, lipids and resins) from the plant allowing for higher yields and a more complete extraction. The stronger solvency power also makes the extraction times faster. The photo below demonstrates CO2’s unique ability to produce significantly different results simply by manipulating temperature and pressure.
Apeks Supercritical’s 2000psi and 5000psi production systems all have the ability to run both subcritical and supercritical – allowing the user to perform a “Fractional Extraction” by first extracting at lower temperature and pressure to remove the lighter, temperature sensitive volatile oils, and then subsequently extracting the same material at a higher pressure and temperature to remove the remaining oils, waxes, etc.
Not all CO2 extraction systems are the same…
Heat is the enemy of any botanical oil. Supercritical CO2 extractions done at very high temperatures and pressures (greater than 5000psi and greater than 120F) can cause thermal degradation of the oils, and when extracting green plant materials can have the potentially negative consequence of extracting chlorophyll. Apeks Supercritical’s systems are designed specifically to take full advantage CO2’s “cold” extraction capabilities to minimize thermal degradation and chlorophyll extraction. The photo below shows the difference between a cold Supercritcal CO2 extraction (below 120F) and a hot Supercritcal CO2 extraction (150F)