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What Is Supercritical CO2 Extraction?
Supercritical fluid extraction (SFE) is the process of separating components from each other by use of a particular type of solvent. These types of solvents are labelled “supercritical” by virtue of the fact that when they are exposed to extreme temperatures and pressures, they display structures that fluctuate between intermediate states of solid, liquid, and gaseousness.
When in this state, supercritical fluids are capable of breaking down structures where they can then be separated, or fractioned. Among the variety of supercritical solvents used for this process, the most common by far is CO2.
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Supercritical (sc-CO2) extraction has been around for decades, appearing first in the 1980s and 90s as a cleaner and more viable alternative to other methods of separation and extraction. From the decaffeination of coffee and tea to the extraction of essential oils for perfumes, this process has become commonplace in many industries.
What Are the Benefits of Using CO2?
Carbon dioxide within our natural atmospheric temperature and pressure rests in a gaseous state. CO2 must be frozen and compressed into a liquid and then further until it reaches its supercritical point. Under controlled circumstances, supercritical CO2 can be used to dissolve substances into “fractions” that can be removed.
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There are several reasons why CO2 is particularly useful within botanical extractions, namely with cannabis:
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CO2 is a naturally occurring compound. It exists all around us and our bodies produce it.
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As far as non-polar solvents are concerned, CO2 is among the safest. In fact, the FDA has labelled CO2 safe for industrial extractions, making it a much less controversial solvent than petroleum based hydrocarbons such as butane or propane.
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The conditions that allow CO2 to change from a fluid state to a supercritical state can occur without having to exceed temperatures above 90°F, meaning there is less risk of compromising the natural volatile compounds found in cannabis.
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CO2 is also unique in that its solubility will change with pressure, allowing for fractioning of the many different types of biomolecules available in cannabis strains. CO2 extraction can be used to pull various cannabinoids from the plant such as THCA, CBD, CBG, THCV as well as terpenes and other compounds.
CO2 Products in the Cannabis Industry
Once a compound has been fractioned using sc-CO2, it can then be further modified and refined depending on the desired outcome. In order to create shelf stable and desirable products for the market, often refinement procedures such as winterization and distillation are incorporated as a secondary process.
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Terpene reintegration may also occur where fractioned compounds are reintroduced to a refined THC solution to create a more robust and flavorful experience for those who prefer to vaporize. This process is unnecessary if the final product is intended for culinary uses as terpenes may compromise the integrity of an otherwise odorless and flavorless product that is perfect for a food additive.
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What makes sc-CO2 so beneficial for the cannabis concentrate market is the customizability factor. By modifying pressure temperature and solvent ratios, various products can be created ranging from vaporizer-friendly oils to dabbing concentrates such as waxes, crumbles, and even shatters and saps. The range of CO2-based products can be much wider than other extraction methods when used to its fullest potential.
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While not always cost-effective, SFE using CO2 has proved to be one of the most versatile and safest methods of producing cannabis concentrates. Today, CO2-based products have saturated almost every major market from consumables to pre-filled vaporizers to dabbing products and isolates. The world of cannabis extraction has benefited greatly from the adoption of this technology, and no doubt, the future of CO2 extraction technology will be positively impacted by its contributions to the cannabis community.
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Content Credit: Patrick Bennett (https://www.leafly.com/news/cannabis-101/what-are-co2-marijuana-concentrates)
What is the difference between supercritical and subcritical CO2 extraction?
CO2 is a unique solvent because its solvency power can change by simply adjusting the temperature and pressure 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.
Supercritical CO2 (SCCO2) extraction is a strong solvent and can extract all of the lighter (volatile oils, light waxes) and heavier molecular weights (heavy waxes, lipids, fats, paraffin) to produce very large yields. At very high temperatures (above 120F) and pressures (5000psi) it will extract chlorophyll as well. Subcritical CO2is a weaker solvent and generally pulls out just the lower molecular weights, and has correspondingly lower yields and higher extraction times.