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For decades, there were only two ways to enjoy cannabis. Smoking was a standard classic, but eating it was a popular second choice. Now the industry is opening in ways that were never imagined before. Vaporizers, hand creams, candies, baked goods, pills, patches and more are some of the many new choices for cannabis connoisseurs. The reason for that is a chemical process known as extraction.
Essentially, by using a like ethanol, hexane, or carbon dioxide, cannabis can be deduced down to its most concentrated form. [1] This concentrated essence, called an extract, then can be added to all sorts of consumer products in ways that cannabis flowers never could. In order to successfully extract cannabis, the plant material must be combined with a solvent to allow for the chemical compounds to accumulate into the extract.
Some solvents have advantages of simplicity or higher yields, but there are a few key ideas that can help determine which solvent leads to the best result.
Safety Considerations
Safety should always be the primary focus when performing chemical procedures like cannabis extraction. With this in mind, different extraction methods will present different safety concerns. [2] Some extracts may be sensitive to heat or some solvents may be particularly prone to ignition or leaving undesired residues in the final product. [3]
Highly flammable solvents such as should be handled with care, especially with extractions methods that require heat like Soxhlet extraction.
The same is also true for petroleum based solvent like propane or butane, which also need to be handled with care and not be used around open flames. [4] One way to prevent the risks associated with these solvents is to use closed loop extraction systems. Closed loops use vacuums, and replace heat with pressure to extract the cannabis. It is also possible to use a solvent that is not flammable, like carbon dioxide. [5] Through supercritical fluid extraction it is possible to tune the solvent and improve the solvation parameters and make it easier to extract the from the plant material, but it does rely on more complicated equipment.
Though it exists all around us in the atmosphere, carbon dioxide is not completely risk-free either. If the laboratory is not properly ventilated, a carbon dioxide leak could lead potentially to asphyxiation. The same is true of other solvent like hexane, heptane, or ethyl acetate. [6][7][8]
Without the right ventilation, exposure to these gases could range from nausea and headaches to comas and death. The good news is that these safety concerns are easy to fix, and depending on the equipment used could lead to differences in the final result.
Final Purity and Yields
Once safety has been managed, it is time to look at how much cannabis extract can be produced from each solvent. The differences in yield can also be determined by solvent of choice and by the ideal extraction method.
With this in mind, ethanol emerged as an early leader for maximizing yields with simpler extraction methods. [2] With basic techniques like maceration, alcohol is often the most efficient solvent, with yields above 80%. There are a few reasons for this efficiency. High proof ethanol extracts the cannabis material, it evaporates at relatively low temperature, and it is easily recoverable following the extraction method.
This means that it is possible to reuse the ethanol in more than one extraction, increasing the efficiency. However, there is a second consideration when it comes to evaluating the purity, which is how much solvent remains in the extract. With this in mind, using a supercritical solvent like carbon dioxide may produce even better results. [7] The supercritical extraction has several advantages including lower toxicity, more versatility, the ability to selectively choose which compounds are extracted, and higher yields. Carbon dioxide can also be reused multiple times, and with more availability in the atmosphere, it lowers your costs even further. Considering carbon dioxide’s yields usually fall in the range of 70-80%, but avoid the risk associated with any residual solvents in the final product, supercritical extraction may be slightly more advantageous.
Intended Uses and Remaining Byproducts
The last thing to consider when selecting a solvent for cannabis extraction comes down to the final results. If the cannabis extract is going to be used in food products, is there a potential for harmful byproducts to remain in the extract? With this in mind, both ethanol and carbon dioxide provide safer alternatives compared to other solvents, regardless of intended use.
Beyond how consumers intend to use the products, there is also the question of what leftovers may remain after the extraction is complete. There will certainly be plant material that needs to be disposed of, but what about remaining solvents? Here again, ethanol and carbon dioxide provide some advantage, as both can either be reused or disposed of with very little ecological harm.
While it does come down to deciding which extraction method is the best, both ethanol and carbon dioxide have many advantages. They are reusable, produce high yields, and provide finished products that are safe to consumers with negligible byproducts. The biggest difference is that ethanol relies on a simpler extraction technique, and carbon dioxide is a cheaper and cleaner solvent but relies on more expensive extraction equipment.
References:
- Lazarjani, Masoumeh Pourseyed, et al. “Processing and extraction methods of medicinal cannabis: A narrative review.” Journal of cannabis research 3.1 (2021): 1-15.
- Al Ubeed, Hebah Muhsien Sabiah, et al. “A comprehensive review on the techniques for extraction of bioactive compounds from medicinal cannabis.” Molecules 27.3 (2022): 604.
- Munson, Curtis L., and C. Judson King. “Factors influencing solvent selection for extraction of ethanol from aqueous solutions.” Industrial & Engineering Chemistry Process Design and Development 23.1 (1984): 109-115.
- Al-Zouabi, Ihsan, et al. “ hash oil and dabbing: insights into use, amateur production techniques, and potential harm mitigation.” Substance abuse and rehabilitation (2018): 91-101.
- Rovetto, Laura J., and Niccolo V. Aieta. “ of cannabinoids from Cannabis sativa L.” The Journal of Supercritical Fluids 129 (2017): 16-27.
- Maqbool, Javeria, et al. “Comparative evaluation of ethyl acetate and n‐Hexane extracts of Cannabis sativa L. leaves for muscle function restoration after peripheral nerve lesion.” Food Science & Nutrition (2023).
- Attard, Thomas M., et al. “Utilisation of supercritical fluids for the effective extraction of waxes and Cannabidiol (CBD) from hemp wastes.” Industrial Crops and Products 112 (2018): 38-46.
- Khan, Iqra Haider, and Arshad Javaid. “Antifungal activity of leaf extract of Cannabis sativa against Aspergillus flavipes.” Pakistan Journal of Weed Science Research 26.4 (2020): 447.
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