How It Works
In supercritical CO2 extraction, a vessel is filled with plant material and then vacuum sealed. Liquid CO2 is then pumped in until a certain temperature and pressure is reached to induce a supercritical state (a state where the CO2 is neither liquid nor gas but has the properties of both). This supercritical state allows the CO2 to penetrate through solids like a gas and dissolve materials like a liquid. The resulting solvent is then released into a separator. The oil exits the separator from the bottom and the CO2 exits from the top for recovery.
Because CO2 is a gas that our bodies naturally produce, using it as a solvent creates a more natural product free of harmful chemicals. (Hence being considered a ‘solventless’ extraction method) By comparison, hydrocarbon solvents like Butane or Dimethylethylene which are used to make BHO and DHO can lead to neurological problems over long term use if the final product hasn’t been properly purged. Another benefit of CO2 Extraction is that, depending on the equipment used, separate types of waxes and oils can be extracted in a single run. Generally, waxes, heavy oils or resins and lighter oils can be separated out through the modulation of temperature and pressure as the final product passes through a device called a phase separator. This extra step saves time in refining for a clean final product.
A significant drawback of the CO2 extraction method is its barrier of entry. Because this process requires high pressure and high vacuum, design and assembly of the equipment require quality components, materials and rigorous attention to safety and quality control. Hence the most basic CO2 extractor has a starting cost of 100k and moves upwards of a half million for turnkey solutions. Additionally, while the final product is very clean and does preserve select amounts of terpenes and polyphenols, CO2 extraction machines face the challenge of disintegrating seals. Liquid CO2 is easily absorbed into the materials used for gaskets and seals. The depressurization of the CO2 from liquid back into gas usually rips these gaskets and seals apart, which if left unchecked, can lead to valve malfunctions. Many manufacturers who have not found solutions for this problem often change out o-rings, seals and gaskets every other run. When these parts are embedded in pumps and safety valves, the time/cost benefit might render the entire process cumbersome and unprofitable. Today, there are companies that have attempted to address this problem of disintegrating gaskets and seals through new materials and technology. One such company, Eclipse, specializes in spring energized seals made of patented thermoplastic elastomer materials. For more information on materials used for o-rings, seals and gaskets, check out our blog on Seals, Gaskets & O-Rings. For now, the CO2 extraction method still yields the most reliably clean extract on the market. However since CO2 as a solvent doesn’t dissolve as many types of terpenes as Dimethylethylene or even ethanol, the dimensionality of its flavor is limited. If cost doesn’t pose a barrier to entry, this method holds great potential for creating consistently clean and pure extracts.
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Gaskets, seals and O-rings come in so many different types of materials that it can be confusing what kind you should use. Check out this article on 6 of the most common used sanitary gasket materials for food grade processing.