When Outfitting Your Lab, Choose CO2. Here’s Why:

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THE DIFFERENCES IN CANNABIS EXTRACTION TECHNOLOGIES

The cannabis industry today is comprised of three main extraction technologies; carbon dioxide (CO2), ethanol and hydrocarbons. Although these extraction methods are different, they all try to achieve the same objective of extracting valuable compounds from cannabis plant material. The main compounds targeted by these extraction systems are cannabinoids and terpenes, but each extraction method has its own respective advantages and disadvantages when extracting these compounds. Not only are the differences solely in how the compounds are extracted, but also extend to extraction safety, environmental impacts and costs. Having an understanding of these extraction methods is important when determining what cannabis extraction method to use. The characteristics that would be important for someone looking to purchase cannabis extraction equipment are discussed below for the three extraction methods mentioned.

CO2

CO2 in its liquid form can be used as an extraction solvent if its temperature and pressure are within the liquid phase range, or as a supercritical fluid if its temperature and pressure are above both 87.98 F and 1071 psi. It is an outstanding solvent for volatile compounds such as terpenes and, as a supercritical fluid, is good for cannabinoid extraction. The final separation of the solvent from the extract is achieved by a density drop that allows CO2 to evaporate from liquid or supercritical fluid to gas. The liquid cannabis oil that is left behind is free of any residual solvents.

Table 1: CO2 extraction system characteristics

Criteria CO2
Scalability Low to high
Infrastructure Required No significant infrastructure required
System Cost Medium to high
Product Options High; tuneability and terpene preservation allows for diverse product offering
Extraction Run Times Medium - long
Energy Usage Low to medium
Solvent Cost Very low
Tuneability Yes
Terpene Preservation Yes
Post Processing Winterization may or may not be required, depending on feedstock input and desired product formulation
Residual solvent in crude extract No residual solvent in extract
Pre-cool solvent No
Feedstock waste No residual solvent, general waste
Solvent Generally Recognized as Safe (GRAS) Yes
Safety High pressure
Solvent disposal Vent to atmosphere

The tuneability of CO2 and its ability to switch between a liquid and a supercritical fluid is a tremendous advantage for this process, and allows for a more diverse range of product offerings. Depending on the chosen parameters, extraction of undesirable compounds such as chlorophyll and lipids can be reduced, or a terpene pull can be completed using a subcritical run. As CO2 can extract at lower temperatures and pressures, subcritical parameters are good for targeting low molecular weight terpenes while leaving other components behind. Typically, with CO2 extraction, a post-processing step of winterization is required to remove undesirable compounds.

Another major advantage of using a CO2 extraction system is the relatively small infrastructure requirements. Unlike ethanol or hydrocarbon extractions that require a Class 1 Division 1 or 2 space, no specialized infrastructure is needed. This represents significant cost savings up front and helps mitigate the expense of the equipment.

CO2 extraction is the leader in safety in terms of residual solvent toxicity as well as environmental impacts relating to solvent disposal. Most extractors will reuse the CO2 or simply vent it to the atmosphere, saving on costly hazardous waste solvent disposal. CO2 is relatively inexpensive to restock, so even when levels need to be topped up, the costs are minimal. This is yet another area in which CO2 proves its affordability in the long run. With the savings on infrastructure, and the long-term costs of maintaining solvent stock, CO2 ends up being a more cost-effective process than the alternatives.

Ethanol

Ethanol extraction is best performed at temperatures below -40 °C, where the co-extraction of undesirables is minimized. However, cooling ethanol to these temperatures can require significant amounts of energy and time. Ethanol is a polar molecular, and this can create issues as it will readily mix with water and dissolve water soluble molecules such as chlorophyll. However, at temperatures below 40 °C this phenomenon is limited. During the extraction process, ethanol is passed over the cannabis material to dissolve the active compounds in the plant.

Table 2: Ethanol extraction systems characteristics

Criteria Ethanol
Scalability Low to medium
Infrastructure Required C1D2 or C1D1 space
System Cost Low to medium
Product Options Low to medium; poor terpene solubility means smaller product offering
Extraction Run Times Short to long, depending on solvent cooling duration
Energy Usage Low to high, depending on solvent cooling
Solvent Cost Medium to high
Tuneability No
Terpene Preservation No
Post Processing Winterization may or may not be required, depending on solvent cooling
Residual solvent in crude extract Solvent recovery required
Pre-cool solvent Below -40°C to minimize co-extraction of undesirables
Feedstock waste Residual solvent, hazardous waste
Solvent Generally Recognized as Safe (GRAS) Yes
Safety Flammable
Solvent disposal Hazardous waste

A major advantage of ethanol extraction systems is that they have a low cost of entry. However, due to ethanol’s flammability, infrastructure to support such an extraction system is more costly due to the requirements for hazardous locations (C1D1 or C1D2 – which means there is an ignitable concentration of flammable gas or vapour that has to be contained).

Terpenes have low solubility in ethanol which results in an oil that can lack flavour and aroma, and a reduced product offering for the extract. What ethanol excels at is cannabinoid extraction and it tends to have shorter extraction run times which is highly beneficial for throughput. The tuneability of the ethanol extraction method is very low and is primarily used to target cannabinoids. Ethanol, like CO2, is also generally recognized as safe (GRAS) for consumption by the FDA. But an important consideration is solvent recovery as residual solvent in the product could harm end users. Furthermore, ethanol waste is classified as hazardous, which in turn requires special handling and disposal.

Butane

Hydrocarbon extraction equipment typically uses butane, propane, or hexane as the extraction solvent (although most commonly butane). Cold butane is washed over the cannabis material, which slowly dissolves the cannabinoids and terpenes. As it is non-polar, it binds to the more fat-soluble components of the plant (cannabinoids, terpenes and lipids) and less so to chlorophyll and other plant metabolites. As it has a low boiling point (-0.5°C/31.3°F), very few temperature sensitive terpenes are lost when boiling off the residual solvent from the concentrate solution.

Table 3: Hydrocarbon extraction systems characteristics

Criteria Hydrocarbon
Scalability Low to medium
Infrastructure Required C1D1 space
System Cost Low to medium
Product Options Medium to high; terpene preservation and cold processing allows for diverse product offering
Extraction Run Times Medium
Energy Usage Low
Solvent Cost Low to medium
Tuneability No
Terpene Preservation Yes
Post Processing Winterization may or may not be required and desired product
Residual solvent in crude extract Solvent recovery required
Pre-cool solvent No
Feedstock waste Residual solvent, hazardous waste
Solvent Generally Recognized as Safe (GRAS) Yes (for butane)
Safety Pressurized and explosive
Solvent disposal Hazardous waste

Butane extraction is excellent for the extraction of cannabinoids and terpenes under the same conditions, and when done properly can produce a terpene-rich end product that closely resembles the starting plant material. This process tends to produce great tasting concentrates like shadder, budder, sauce and more.

However, butane and other hydrocarbons are highly flammable and volatile, which means there are strict regulations that surround butane extraction systems. Again, like ethanol extraction, a hazardous location space is required, and a solvent recovery step is needed following extraction. The spent butane is also classed as hazardous waste and appropriate environmental disposal is required.

While ethanol and butane extraction systems have their place in cannabis extraction, CO2 has proven itself to be one of the most adaptive and safe cannabis extraction methods. The CO2 extraction process is well known for its low up-front infrastructure cost, safe solvent use, scalability, and tunability. These factors, along with its long-term environmental sustainability, make CO2 an excellent choice for cannabis extraction.

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