The CO2 Cannabis Extraction Process Explained
People generally make assumptions and associations when hearing about CO2 extraction. Like a lot of people, you probably think of closed-loop, high-pressure systems (e.g. supercritical and subcritical extraction) when hearing the term. But there’s so much more to CO2 extraction than just using high-pressure carbon dioxide to mimic a solvent. For instance, did you know that you can also use CO2 as a refrigerant or cooling agent at atmospheric pressure to brittle trichomes and mechanically extract them using a sifter? If you think you already have a basic understanding of how CO2 is used in an extraction environment, keep reading. There’s a lot more to it than meets the eye.

Solvent CO2 Extraction

CO2 is commonly associated with full-spectrum extract (an extract with a complete cannabinoid and terpene profile as opposed to artificially added terpenes or distilled cannabinoids). Extraction with subcritical and liquid CO2 allows for an efficient terpene extraction, so you don’t have to add additional terpenes from plants or other sources to make your extract work in a vape pen. And because CO2 naturally evaporates, there’s virtually no residual solvent left behind after the extraction is complete. The following are among the key reasons why high-pressure CO2 has become popular for extraction:
  • It behaves like a solvent at high pressures
  • It’s the cheapest chemical to use in extraction
  • It doesn’t require C1D1 rooms with fire suppression
  • It allows for compliance with strict regulations
  • It supports the production of Full Spectrum extracts and vape pen oil
Often facilities will choose CO2 extraction because it’s the only type of extraction allowed by their fire department, zoning regulations, or Authority Having Jurisdiction (AHJ). While high pressures can present dangers, CO2 is non-flammable.

The Downsides of High-Pressure CO2 Extraction

One downside of CO2 is that it’s inhibited by water content, so producing live extracts is not really an option without advanced methodologies. CO2 readily dissolves in water, just like soda bubbles. For this reason, it is necessary to dry out your material prior to extraction. Most facilities also decarboxylate their material as THC extracts more readily in high-pressure CO2 than THCA. On the same token, it’s rare to see CO2 extracts packaged as dabs in a jar, as it’s too liquidy. There is nothing wrong with dabbing them, but the form factor is not conducive to jar packaging, as it ends up on the lid unless special packaging is used. In addition, CO2 extract takes on an amber brown color, which sometimes gets ridiculed as being impure, even if that’s an unfair presumption. In fact, clear extracts are often the most adulterated and made from the worst material. Still, when deciding for or against CO2 extraction, it’s important to understand how the perception of color might affect your market value.

Types of CO2 Extraction Methods

There are many types of CO2 extraction methods, including methods where pressurized CO2 behaves like a solvent (such as in supercritical and subcritical extraction) and methods where low-pressure CO2 works as a refrigerant (more on that later).

The Supercritical Carbon Dioxide Extraction Method

Supercritical fluid extraction is one popular type of CO2 extraction, though not all machines can support it. When CO2 is heated to certain pressures and temperatures, it transforms into a supercritical fluid—meaning that it has the properties of both a gas and a liquid. Typically, a CO2 extraction tech will run pressurized liquid CO2 to extract terpenes and use higher pressures for cannabinoids. Then they blend these two fractions together to make full-spectrum oil for vape pens.

The Subcritical CO2 Extraction Method

Subcritical CO2 works similarly to supercritical extraction, but it has different temperature and pressure requirements. Liquid extraction times are typically much faster and are designed for terpene extraction. Because you’re working with lower temperatures and pressure settings, you’re better able to extract lower-density compounds such as terpenes.

Sub-Zero (No Pressure) CO2 Extraction

As we’ve said, CO2 doesn’t just function like a solvent; liquid CO2 can also work as an effective freezing agent, which presents a whole world of solventless extraction potential. And unlike high-pressure CO2 or hydrocarbon, this process requires no special licensing or facility development. You don’t need to freeze your product ahead of time in order to turn cannabis flower into sift or hash. The flash-freezing process, however, does allow you to achieve a higher-quality extract—and ultimately that’s the goal for all processors. If you’ve ever used dry ice to freeze cannabis buds, you already understand the basic science. Dry ice is just the solid form of liquid CO2, but liquid CO2 is much better for freezing fresh cannabis because it doesn’t bruise your trichome heads or force excess cannabis plant material into your kief. It simply flash-freezes your product so that you can extract the valuable resin glands and trichomes quickly and easily with no solvents required. It’s quick, it’s simple, and it’s clean. To understand how low-pressure liquid CO2 fits into cannabis processing, look no further than The Original Resinator. The Resinator is the only solventless cannabis extraction product designed with wet, dry, and flash-freeze capabilities. It uses liquid CO2 to freeze your cannabis flower to sub-zero temperatures and help you transform it into bubble hash or dry sift. The flash-freezing process also makes the sugar leaves brittle, so they can easily detach without the need for blades, leaving you with a high-quality, whole-bodied trim. After freshly harvested cannabis is loaded into the Resinator OG or Resinator XL, the liquid CO2 canisters release carbon dioxide into the chamber to power the cryo-capabilities. The CO2 expands into a gaseous state as it’s released. It doesn’t hold pressure the way that it would in a closed-loop extraction system; it simply freezes the plant material to preserve the maximum concentration of terpenes, giving you a “live” product that’s more flavorful, more aromatic, and more likely to fetch top-dollar. And because the Resinator is designed as an all-in-one trimmer, flash-freezing tool, and extraction machine, you can go from harvest to hash in one smooth workflow. For instance, if you want to make sift, our machines support CO2 kief extraction and separation. Our patented Cryo-Sieve® process filters out the undesired plant material and leaves you with just your desired trichomes. Just load the drum with the appropriate micron screen for your desired extract (e.g. a 75- to 100-micron screen for making high-quality dry sift or a series of micron screens for premium bubble hash), and let the Resinator go to work. It’s live kief sifting made easy. The Resinator can serve as an excellent pre-extraction tool if you’re looking to make live resin or other live extracts in a CO2, hydrocarbon, or solventless system. It supports sub-zero separation for biomass reduction ahead of your main extraction, so you save time and achieve a higher-quality product in the end. Biomass reduction is a process where we extract the trichomes by utilizing liquid CO2 much in the same way many other sifters will use dry ice. The Resinator removes almost all the cannabinoid content, with residuals between 1-2% total cannabinoids left behind. From there, you can extract the kief/sift with another extraction method such as hydrocarbon extraction or high-pressure CO2. All in all, you benefit from higher throughput (as great as 4-5x), a cleaner product, smaller equipment needs, and a reduction in solvent, energy, and labor costs.

Put Low-Pressure CO2 to Work for You

Carbon dioxide works well for extracting cannabis compounds because it’s extremely malleable. By adjusting the pressure and temperature, you can put it to work in numerous ways. But while there are pros, cons, and tradeoffs to using CO2 for high-pressure extraction, the benefits of using CO2 as a freezing agent are enormous—and the Resinator can help you unlock these benefits like no other machine. The cannabis market is getting more competitive than ever, and a growing number of consumers are demanding higher-quality live extracts. Emerging carbon dioxide technologies are making it easier than ever before to achieve these kinds of products without the need for solvents, so you might want to consider how CO2 as a refrigerant can benefit your own game plan.
TJ Arnovick

Cannabis extraction expert and founder.