Cannabis and hemp extracts are quickly becoming the favorite product category among recreational and medical marijuana consumers for their potency and purity. Cannabinoid extracts of compounds like CBD, THC, or a mix of both can be made with a variety of solvent-based and non-solvent methods. Carbon dioxide (CO2) has become a popular extraction solvent for cannabis concentrates, but that's not the only place you can find CO2 extraction.
In fact, many dry cleaners use liquid carbon dioxide to remove dirt and grime without altering the quality of the clothing. Similarly, a process known as supercritical CO2 extraction has been used since the 1980s to decaffeinate coffee and tea, extract essential oils for fragrances, and produce pharmaceuticals.
Supercritical CO2 is a relatively new process used in concentrate processing that can make THC and CBD tinctures, vape oils, capsules, powders, transdermal patches, topicals, edibles, terpene isolates, and other cannabis and hemp-infused products. Plus, CO2 is generally safe, efficient, versatile, and eco-friendly to use. And just a reminder: please don’t try this yourself. Cannabis extraction is a science reserved for highly trained professionals.
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What is Supercritical CO2 Extraction?
Usually, carbon dioxide exists as a greenhouse gas at room temperature. Carbon dioxide is exhaled by humans and animals and used by plants to produce carbohydrates during photosynthesis. In a solid form, carbon dioxide is dry ice. CO2 is widely used in extraction facilities because it's affordable, non-toxic, non-flammable, and practical.
CO2 turns into a liquid when placed in critical temperatures and pressures. CO2 has won a reputation as a tunable solvent meaning that extractors can create a complex set of products by changing the temperature and pressure variables. Slight parameter changes in the extraction equipment can target and extract compounds including terpenes by weight.
Benefits of Supercritical CO2 Extraction
Many extractors swear by supercritical CO2 extraction due to its ability to produce clean oil with varying textures and consistencies for dab connoisseurs. Some manufacturers steer clear of toxic solvents like butane and propane that can require time-consuming post-processing to purge the solvent in the extract. CO2 has produced some of the highest yields for large-scale manufacturers compared to other solvents.
Perhaps the biggest draw for supercritical CO2 extraction is the ability to fine-tune temperatures and pressures to separate different compounds during the extraction process. For example, terpenes have a lower boiling point than heavier cannabinoids like THC and CBD. That means that you can get a full-spectrum oil with its original chemical profile or an isolated terpene with supercritical CO2 extraction.
Supercritical CO2's efficacy is mostly due to its physical attributes. First, supercritical CO2 extractions use low temperatures, which reduce cannabinoid and terpene degradation. Supercritical CO2 can carry a high amount of compounds because of its dense liquid state. On top of that, supercritical CO2 can easily diffuse like gas through the raw material and has minimal flow resistance. CO2's density can be manipulated with pressure and temperature changes.
Behind-the-Scenes of a Supercritical CO2 Lab
Supercritical CO2 extraction training, equipment, and the entailing facility requirements can be costly. High-capacity extraction equipment can cost hundreds of thousands of dollars and require expertly-trained staff. Nevertheless, CO2 is able to strip therapeutic compounds from the cannabis plant and evaporate like carbon dioxide in an open can of soda at room temperature.
In an approved extraction facility, extraction technicians load dried cannabis into an extraction tube. Supercritical CO2 is pushed through the tube, thereby, stripping away unnecessary organic plant matter. The liquid CO2 is transferred into another vessel where it turns back into a gas. The process may be done a few times to ensure proper extraction. What's left is pure cannabinoid and terpene oil. CO2 is recycled and reused in a closed-loop extractor.
Winterization
Cannabis that goes through the supercritical CO2 process can still contain waxes and fatty acids in the final product. These unwanted plant compounds require further purging through a process called winterization using ethanol as a solvent. Low temperatures are used to separate the waxes, lipids, and chlorophyll from the cannabinoids.
This post-process can be time-consuming and expensive depending on the capacity of the extraction equipment. The winterization process must be done multiple times to completely remove the waxes. After that, the ethanol must be retrieved using rotary evaporation systems.
Supercritical CO2 Products
After the supercritical CO2 extraction has taken place, the resulting oil can be post-processed through processes like winterization and terpene reintegration. Cannabis oils intended for edibles or culinary reasons may not necessitate terpene reintroduction to maintain their neutral odor and flavor. Supercritical CO2 is versatile enough to make nearly every cannabis product.
CO2 is an adaptable solvent that can create a variety of concentrate types by modifying temperature and pressure variables. Supercritical CO2 can produce products such as distillate oils for disposable vaporizers or a variety of dabs like crumble, wax, shatter, and sap. Supercritical CO2 is effective at creating THC and CBD products, ones with a ratio of both compounds, and other products with minor cannabinoids.
What's the Difference Between Supercritical and Subcritical CO2?
CO2 turns supercritical when the pressure is 1083psi or higher and the temperature is 88ºF. When the temperature drops under 88ºF, CO2 turns into a liquid and is known as its subcritical state. CO2 converts to a gas when the pressure decreases below 600psi. Subcritical CO2 extraction can remove lighter compounds, but supercritical CO2 extraction is more robust extraction method.
Supercritical CO2 extraction can extract volatile terpene compounds that are sensitive to thermal degradation and effectively remove plant material leaving behind a clean oil. Fractional extraction methods use low temperatures and pressures to target terpenes and then remove oils and waxes from the material. Cold separation techniques are often used to prevent decarboxylation of unactivated compounds like THCA and CBDA.
Supercritical CO2 vs. Other Extraction Methods
Solventless cannabis extraction can produce potent and powerful dry-sift kief and hash, but can also leave behind organic plant matter. Manual dry sieving using screen meshes eliminates the need for a solvent to remove the trichomes' essential oil. Solvents are used to increase the number of cannabinoids reaped during extraction. Supercritical CO2 extraction faces stiff competition from other just-as-efficient methods.
For example, ethanol extraction can produce comparable concentrates and extracts to supercritical CO2 extraction, which can run the risk of thermal degradation. Ethanol extraction, however, can be difficult to scale to produce high yields at a fast pace. Butane extraction has significantly lower start-up costs than supercritical CO2 extraction but requires even stricter safety precautions for the flammable solvent.
Cannabis extraction methods ultimately depend on a variety of factors including the quality of starting plant material, equipment, and staff. Supercritical CO2 extraction is here to stay and has become one of the most common methods of extraction. It's likely that you've already tried a cannabis product that has undergone supercritical CO2 extraction. Ultimately, the type of concentrate you consume is up to your personal preference.
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