Extraction Technologies: Which to Choose?
Currently, there is a wealth of cannabis extraction technologies available to invest in or use to extract cannabinoids for medicinal or adult use. Over the last few years, it has become more and more clear that whole plant extracts which extract the medically interesting biomolecules from the plant in a manner that is “honest” to the chemical composition of the plant are likely more useful and attractive to patients. Each extraction technology produces a result that varies widely in its composition, even if the same starting plant material is used. Here, I want to evaluate and rank the extract technologies based upon how “honest” each is to what is actually in the plant, solvent contamination risks, post-processing required, and potential for scaleability.
The main extraction technologies currently being used are: hydrocarbon, supercritical/subcritical CO2, ethanol/cold ethanol, and freon 134a. There are some that used mixed solvent extraction techniques, including pulsed ethanol extraction, that I will not comment on at this point as they are quite new.
Hydrocarbon extraction uses butane, hexane, or combinations of similar charmicals, and it is very effective at extracting the following chemicals from cannabis: hydrocarbons, carotenoids, diglycerides, monoglycerides, stearin, phospholipids, tocopherols, terpenoids, aldehydes, ketones, complex ethers, flavones, aglycones, alcohols, amino acids, organic acids, carbohydrates, and alkaloids. The undesirable chemicals from both a quality and medicinally interesting perspective are amino acids, organic acids, carbohydrates, and alkaloids. So, hydrocarbon extractions are fairly selective but does require a fair amount of post-processing to eliminate undesirable chemicals as well as a process to eliminate solvent contamination, which, if present, is quite toxic. This form of extraction is quite useful for producing more potent extracts. However, it is more selective and may hyper-concentrate some terpenes and leave some others of interest out. Some states also do not allow hydrocarbon extraction for food or medicine, such as California. Overall, it is a fairly decent technique and is more scalable than CO2 but it has some down sides in terms of post-processing and a small solvent contamination risk.
Subcritical CO2 is defined as CO2 gas with a pressure of at least 600 PSI to 1083 PSI but a temperature < 88 degrees F. If the pressure drops below 600 PSI, the CO2 liquid becomes a gas that cannot solubilize extract components. Varying temperature and pressure allows you to be more or less selective because the pressure and temperature changes the dipole moment of CO2 altering its polarity and thus what it can pull into solution. This is a complex process that requires a lot of careful experimentation and practice. It does not have the risk of solvent contamination and you recapture the CO2, which helps with expense, but the systems designed to do the extraction are incredibly expensive. Subcritical CO2 has the downside of not getting all of the biomolecules of interest while also extracting many undesirable components that requires a lot of post-processing. It also hyper-concentrates some terpenes while ignoring others, making it a less “honest” to the plant extraction even compared to hydrocarbon extraction. The main chemicals it extracts are diglycerides, monoglycerides, stearin, phospholipids, tocopherols, and terpenoids. It does not extract the medically useful biomolecules such as hydrocarbons, carotenoids, aldehydes, ethers, and alcohols. It is becoming more popular because it is more gentle and less damaging to terpenes as compared to supercritical CO2 and it doesn’t get as many undesirable elements that requires post-processing.
Supercritical CO2 extraction uses C02 gas at 1083 PSI and at least 88 degrees F. It has the downsides of gathering even more undesirable chemicals that requires a lot of post-processing. It extracts the useful medically useful phospholipids, tocopherols, terpenoids, aldehydes, ketones, complex ethers, flavone aglycones, and alcohols. It ignores the medically useful hydrocarbons, carotenoids, diglycerides, monoglycerides, and stearin. It extracts the undesirable amino acids, organic acids, carbohydrates, alkaloids, tannins, phenolic compounds, glycosides, minerals, polysaccharides, oligosaccharides, and pectins which need to be removed via post-processing.
It also is not particularly “honest” to the terpene profile and tends to destroy many of them with high temperatures. Supercritical CO2 is, again, very expensive and does not select the most interesting biologic compounds. More useful extraction technologies that are cheaper, cleaner, and more scalable are currently available.
Ethanol and Cold Ethanol
Ethanol, especially cold (-20 degree C) is especially good at extracting the interesting biomolecules, preserving terpenes, and is much more “honest” chemically speaking to the whole plant as compared to hydrocarbon or either CO2 technique. Cold ethanol is becoming more and more popular due to the increased interest in whole plant extracts that are “honest” to the composition of the plant raw material. It is favored in general by Israel for this reason as well. It captures most of the medically interesting molecules but leaves out hydrocarbons, carotenoids, and diglycerols but captures monoglycerides, stearin, phospholipids, tocopherols, terpenoids, aldehydes, ketones, complex ethers, flavone aglycones, and alcohols. It captures the undesirable amino acids, organic acids, and carbohydrates that requires some post-processing for removal. Overall, ethanol, especially cold ethanol is one of the best for extracting a more chemically “honest” to the plant extract gently, requiring some but not a lot of post-processing.
Freon extraction uses freon 134a, which is the same HFA propellant in asthma inhalers such as ProAir and Ventolin. Freon has been well-studied by the FDA and is considered safe for medication and for extraction of food or medicinal products. Although it sounds more chemical and is scary to many, it evaporates cleanly at -30 degrees C. It can use trim and low concentration plant product more effectively than any other extraction technique, leading to low levels of loss and is perhaps the most efficient and scalable for industrial production. It also captures the most medically interesting biomolecules while leaving out undesirable elements and captures hydrocarbons, carotenoids, diglycerides, monoglycerides, stearin, phospholipids, tocopherols, terpenoids, aldehydes, ketones, complex ethers, flavone aglycones, and alcohols while ignoring all of the undesirable chemicals. Although it is not popular yet due to fears about freon, I think it will eventually be the industry standard, especially for inexpensive whole plant extracts. It is superior for capturing whole plant extracts but followed by cold ethanol as a close second.
I’ve included a chart that compares all these methods for quick reference:
If you are using one of these techniques and have invested heavily in one technology, switching may not be advantageous from a business perspective. However, if you are considering becoming involved in the cannabis industry in the near-future, it might be better to choose one of the extractions that produce a better whole flower product with as little post-processing as possible. If you are considering choosing a manufacturer for your product or getting involved in extraction, I would lean toward cold ethanol or freon 134a. I would also encourage people not to be as scared of freon because it sounds scarier. It is actually a lot better a technique in the long run and it evaporates 100% cleanly with very little post-processing.
I hope this breakdown helps people sort out the differences between different extraction technologies and defines some of the differences so people can make an educated choice about the extraction technology that is best for them.