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Cannabis Extraction Methods

Various extraction methods used to concentrate and target molecules from plants have been around for centuries. Cannabis extraction processes have adapted different techniques popularly used in today’s agriculture, biopharma and petrochemical industries.

There are a few most commonly used extraction methods used in the creation of cannabis crude oil: CO2, hydrocarbon and ethanol. Each of these methods has its own set of pros and cons, as outlined in detail below.

CO2 extraction

One of the most popular methods of cannabis extraction is through the use of CO2 as a solvent. This method takes advantage of the supercritical properties of CO2 gas required to strip materials from botanical substances. This method of extraction has been used by a variety of industries before it was applied to cannabis, including in the production of perfumes and essential oils.

It is important to note that cannabinoids have a different molecular structure than essential oils, meaning they cannot be extracted together. Cannabis oil is extracted via CO2 by running supercritical extraction. The cannabis terpenes require subcritical extraction. As a result of having to run two separate processes, the entire extraction process is quite long. CO2 is a low density gas and needs to be pressurized to about ~8800psi (600atm) to become a solvent for those thicker or more viscous oils. That is why, due to the process architecture, scaling the CO2 system and operation is an expensive process. Moreover, using CO2 requires post-extraction lipid and wax separation by use of lipophilic solvent, such as ethanol, which adds additional cost and time to the process.

Hydrocarbon extraction

Hydrocarbon extraction uses a hydrocarbon, such as butane or propane, as a solvent. The hydrocarbon is washed over the plant matter in order to break it down, before ultimately concentrating a targeted molecule and removing it from the biomass. Hydrocarbon extraction has become popular due to its efficiency in the areas where CO2 falls short. It has a higher yield rate, preserves different terpenes than other methods; the equipment is affordable, although the solvent boiling point is still high enough to require solvent vacuum purging and remediation. Overall, this method of extraction is preferable, but also comes with its own set of drawbacks. Chemicals like butane are volatile gases and obviously have a high potential for combustion and flammability, resulting in zoning and storage limitation laws put in place for safety purposes. Consequently, this creates limitations on scalability for operations looking to expand. If a manufacturer is looking to scale, hydrocarbon extraction is not advised. De-waxing during hydrocarbon extraction is an issue, and secondary solvent de-wax will need to be performed in order to remove any stray lipids that made their way into the oil during extraction.

Ethanol extraction

Ethanol is now a preferred method for most hemp extractors because it is simple and scalable. The real advantage to this method is its ability to effectively scale up within manufacturing operations, especially after the extraction has been done with cold ethanol, below -40°F (-40°C). Winterization uses ethanol and sub-zero temperatures to separate unwanted fats and waxes from the oil: that is why the oil extracted this way is with almost no fats and lipids and looks like post-winterized crude. The major disadvantage of ethanol is that it denatures the oil.

Another disadvantage of ethanol is the high boiling point of around 176°F (80°C). This means that in order to be separated from the extract the temperature may exceed 212°F (100°C), the boiling temperature of water; so, as a result the separated solvent will be diluted in the plant residual moisture. The boiling point of the terpenes is 248°F (120°C) to 356°F (180°C), which means that the ethanol-water solution will already be contaminated with terpenes and will need to be purified after each run to keep the consistency of the extracts the same every time. This process brings a loss of the solvent to around 15% to 20% of the extractor volume at every run — which increases the operational cost of the extraction significantly, especially when operating at scale.

R134a Pure Botanical Extraction

One other method of cannabis extraction is through the use of a tetrafluoroethane (TFE), R134a, as a solvent. R134a, by itself, is often used in aerosol products for drug delivery. Products which are extracted using this method are called post-winterized, full spectrum oils. The level of wax present in the extract right off the machine is usually less than 5% or even less than 2% in most cases. The process is very similar to CO2 extraction in that both methods utilize a gas for extraction and liquefy it when it is in contact with the material.

Pure Botanical Extraction (PBX STANDARD) is performed at low pressure and room temperatures to gently strip the natural oils from the raw cannabis products in a closed loop system. The gas is slightly pressurized, then driven through the plant material and recovered in a separation tank leaving the full spectrum oil behind. R134a extraction is safe for human health, nontoxic, FDA approved and qualified as GRAS (Generally Recognized As Safe) under FDA standards. It has also been approved for usage as a solvent in the EU, by EC Directive 2009/32.

R134a extraction is the PBX STANDARD that was originally pioneered by COMERG after years of diligent research and prototyping. The PBX STANDARD has effectively isolated R134a to be the most appropriate method of primary plant matter extraction. As a primary extraction method, it only draws out the terpenes and the heavier resins – in this case, the cannabinoids. Prior to deploying this extraction methodology in support of hemp and cannabis product manufacturing, COMERG has successfully applied this method to over 150 various herbs.