CO2 Extraction for Cannabis

There are various different methods of extracting cannabis. Whether you prefer salves, vaporizer pens, elixirs or infused edibles it is very possible that you have come across some cannabis products extracted though carbon dioxide (CO2) extraction technology.

Though this particular technology has not been used on cannabis for long, it has been employed in the extraction of other botanical extracts for quite some time.

Why is CO2 Extraction Popular?

As the consumers gets to be more discerning, they prefer products that do not contain any solvents such as petroleum based solvents like butane and propane, which hitherto had been most widely used for extraction, and other substances that some even consider to be cancer inducing. CO2 extraction offers a safe alternative as carbon dioxide is a gas that is found all around us and is not known to cause us any harm. It is also a versatile and sustainable method of extraction.

More and more, retailers are now labelling their concentrates by the method of extraction, detailing whether or not they used solvents and if they did, to what extent.

So, how does CO2 extraction work?

Obviously, CO₂ (Carbon Dioxide) is in gaseous state at room temperature. CO2 is also the infamous gas blamed for climate change which every responsible industry is trying to reduce its emissions of.

However, when not in gaseous form CO2 can have many beneficial uses. When inert, it has no color or scent, in non-toxic and GRAS classified (which means Generally Recognized As Safe under FDA rules). It is also affordable and very readily available.

CO₂ can behave as a fluid when compressed and under certain conditions. When in fluid state, it can dissolve “non-polar material” that possesses low molecular weight using a process called Supercritical Fluid extraction (SCF).

What exactly is Supercritical CO2 Extraction?

In a more detailed description, supercritical fluid extraction (SFE) can be described as the process in which components can be separated from each other using a particular type of solvent. Supercritical solvents are labelled thus by virtue of them displaying structures which fluctuate between gaseous, liquid, and solid states when exposed to extreme pressures and temperatures.

Supercritical substances that are in the fluid state break down structures to give way to fractioning. While different solvents can be used for fractioning, C02 is used in most occasions because it is efficient and economical.

Why is CO2 Extraction particularly viable for cannabis?

The conditions which allow CO2 to move from a fluid to a supercritical state usually occur without necessarily exceeding temperatures that are above 90°F. This means that there is negligible risk of the volatile compounds found within cannabis being compromised.

The uniqueness of CO2 that allows its solubility to change with pressure, which in turn allows for the fractioning of the diverse types of biomolecules that exist in cannabis strains, makes it ideal for this kind of extraction. CO2 extraction is useful in the extraction of various cannabinoids such as THCA, THCV, CBD, CBG, as well as the very delicate terpenes and other compounds found in the cannabis plant.

How does SCF compare to conventional extraction methods?

SCF has several advantages over conventional extraction and even pressing because:

• It uses lower temperatures of operation. This means that heat-sensitive components such as cannabis terpenes remain intact
• It does not involve oxygen, which means oxidation-sensitive components stay intact
• It has higher selectivity and therefore higher mass transfer. This means that there is higher yield as well as longer shelf life.
• The process of SCF is cleaner, both in terms of yield as well as environmental impact.
• Longer shelf-life of the extracted product when compared to conventional extraction methods
• More intense flavor and scent when compared to products that have been extracted conventionally.

CO2 Extraction Equipment and Process

The processes and equipment necessary for SFE can greatly vary in cost as well as complexity depending on a number of factors, including scaling requirements. If one intends to fraction large quantities of product, they would need larger machines which cost upwards of a couple of hundred thousand dollars as well as the requirements for servicing by highly trained professionals preferable in a lab setting.

The process of extraction is as follows:

Step 1: The gaseous CO2 is run through a chamber under extremely low temperatures of (-70°F) with enough pressure to make the gas change into fluid. When in this state, CO2 shows special properties which become supercritical when reheated and pressurized.

While in this state, the supercritical fluid is passed through the chamber containing the “raw” cannabis material. Because it has unique properties, the supercritical fluid is able to easily pass through the cannabis and dissolve the trichomes membrane to capture the many active compounds contained therein.

Step 2: The compound enriched solvent is then passed through a second pressurized separation vessel. The difference this time is that the temperatures and pressures will fluctuate so as to fraction the compounds like cannabinoids and terpenes away from the supercritical fluid.

Step 3: The last step is to transport the CO2 that remains behind to a condenser vessel whose pressure and temperature will allow it to stabilize back into gaseous state. Most “industrial scale extractors” actually recycle CO2 for reuse in a process that is referred to commonly as “closed loop extraction.”

Product improvement: The products that have been fractioned using sc-CO2 can then be further refined or modified depending on the outcome that is desired.  In order to make desirable as well as shelf stable products, refinement procedures like distillation and winterization are often incorporated in a secondary process.

Conclusion

CO2 extraction is quickly gaining ground and might even soon be a requirement as it is considered to be a safe extraction method that retains the integrity of the cannabis products. In cases where the benefits of terpenes or the scent of the particular cannabis strain are vital, this is a great way to go!