Hundreds of chemicals exist in cannabis—these include the psychoactive tetrahydrocannabinol (THC), the purportedly medicinal cannabidiols (CBD), and many more. Plant processors and product manufacturers use a variety of extraction techniques to obtain the component chemicals. If nothing else, the growing number of signs advertising CBD-based products provides some indication of the increasing use of cannabis extraction.
The idea of extraction is pretty straightforward: remove the chemical components from a cannabis plant. In practice, it gets more complicated. First, some chemicals are more desirable than others in a particular product, and some methods of extraction do a better job of isolating specific components. Next, the resulting extract must be safe for its intended purpose. For example, nothing dangerous should be left in the final extract, such as a solvent used in extraction or a pesticide used in growing. Given that cannabis extraction is a business, the method should also provide the needed level of throughput at an affordable cost. Meeting all of those caveats turns cannabis extraction into a competitive industry.
Alexander Wilson, assistant professor of chemistry at Northern Michigan University, divides cannabis extraction into two major categories: methods that use a solvent and ones that don’t. He notes several solvent-based methods, including extraction with butane, ethanol, isopropyl alcohol, propane, and supercritical carbon dioxide (CO2 ). For solvent-free methods, Wilson points out sieve extraction, water extraction, and rosin press extraction.
As Wilson summarizes these options, he says, “I would characterize ethanol as the cheapest for market entry and most scalable.” It can also be pretty easy: soak the cannabis in ethanol, remove the plant pieces, filter the remaining liquid, remove the ethanol with evaporation, and that just leaves an extract. This, though, is a bit too simple for most industrial applications, which would at least include some other steps, such as distillation.
Every method offers some benefit, and probably a shortcoming or two. For lower cost, Wilson suggests a CO2-based method, which he adds has “the fewest clean-up steps required.” Some methods are also riskier than others. For example, Wilson notes that butane-based extractions have “the highest potential for risk,” such as the potential for an explosion.
Carbon dioxide is king
The benefits of CO2-based extraction trigger wide use of this method. “The vast majority of cannabis extract produced is extracted via supercritical fluid carbon dioxide extraction,” says Christian Sweeney, vice president of science and technology at Cannabistry. “This is because the scale and throughput of CO2 extractors is considerably larger and continues to grow.”
As a producer of cannabis-infused products, Sweeney knows what it takes to get the best components from cannabis. When asked about the latest advance in cannabis extraction, he says, “To my mind, the most interesting and impactful advance in cannabis extraction has been the ability to produce nature-identical extracts using CO2-extraction.” He adds, “This means that skilled extractors are able to deliver a true bioactive replica of the cannabis cultivar being extracted, including the efficacy, flavor, and aroma.” The consequence of that capability, Sweeney says, is “a shift in focus from distillates and isolates focused solely on maximizing the THC content in an extract toward full spectrum or—in the best cases—truly ‘nature identical’ extracts.”
Ultimately, scientists will develop easier and more efficient ways of extracting more-targeted components from cannabis. In many ways, this young industry continues to evolve from garage-based methods to processes using commercial equipment—some of it now dedicated to cannabis extraction. Not too many years ago, some major instrument makers requested—even insisted—that none of their devices should be linked to cannabis extraction. Now, many publish specific cannabis extraction workflows. What a difference a few years, and some changing laws, can make in an industry