There are a few different methods that are most-widely used to extract the cannabinoids, terpenes, etc. from Hemp/Cannabis. The extraction method of choice may be dependent on desired processing scale, capital, space, and market identity.
Hydrocarbon solvents like butane and propane are often used to produce artisanal oil. Use of these solvents is reportedly the best method to get all the desired cannabinoids and terpenes from the plant with the greatest efficiency, but on smaller scales. Many believe that retaining all the inherent constituents in the oil is needed to produce all benefits - known or unknown, that the plant has to offer. This is referred to as "The Entourage Effect." Some would clarify that a true entourage effect must have all inherent THC included. Cannabinoids and terpenes are volatile, but the properties of butane and propane, minimize risk of losing these valuable constituents during processing.
Hydrocarbon solvents are most efficient for throughput of approximately 1000 lbs or less per day. Scaling up processing throughput with butane and propane requires large footprints, raise safety concerns because of the high quantities with low flashpoints, and would require facilities to be a certified Class 1, Division 1 Hazardous location.
Ethanol extraction enjoys many of the benefits of hydrocarbon solvent extraction, and larger quantities can be kept in a facility at a lower risk, because it is less flammable and does not require pressure. Butane and Propane require pressures of 50 -150 psi (CO2 requires pressures of 1000 psi or greater to achieve extraction). This allows for ethanol extraction to offer higher throughput than the hydrocarbon solvents, with maximized and efficient extraction of compounds.
Ethanol does have its challenges. Relatively significant post-processing is required when using ethanol extraction. This, in part, is due to ethanol's positive molecular charge - which not only attracts the desired compounds, but also attracts unwanted parts of the plant that will require further processing (fats, wax, chlorophylls). Decreasing the temperature of ethanol can mitigate this. Depending on the scale of extraction, this temperature regulation of high volumes will require the right equipment, careful engineering, and possibly increase the cost of power, which is a consideration in any processing operation.
Ethanol extraction also requires distillation or decarboxylation to remove residual ethanol from the final product.
For large scale extraction, most processors choose CO2. By manipulating pressure and temperature to change CO2's state, CO2 will act like a solvent. The ability to dial in the temperature and pressure, makes CO2 a "tunable" solvent and able to be selective in which compounds to target. However, arguably one of the most significant factors in CO2 as the choice for extraction of scale is how it compares with safety precautions and requirements. CO2 extraction facilities at scale do not have the same explosion concerns or need for precautions, as large scale hydrocarbon or ethanol solvent operations.
At standard temperature and pressure (STP), CO2 is in a gaseous state. By increasing temperature and pressure to a critical point, CO2 will become a supercritical fluid - it will fill its space like a gas, but have the density of a liquid. It is in this state that CO2 acts most efficiently as a solvent.
All extraction methods have their pros, cons, and a dynamic interplay among them. For CO2, the tunable relationship is a tricky one. To use CO2 at its highest efficiency, you would set the temperature higher. This increases productivity, but decreases selectivity and will pull unwanted components from the input material, like wax. To increase selectivity, the temperature is lowered, but the CO2 to feed ratio greatly increases, which reduces efficiency.
For a time, CO2 had a high cost of equipment for initial setup, which would be prohibitive for some operations. As the industry has developed, solutions to this have become available through equipment innovation.
Refining the extracted liquid further with distillation and other refinement technologies allows a processor to isolate target compounds like CBD and vaporize unwanted others. Distillation also enables a processor to create uniformity in the refined oil, which allows for consistent inputs for end products. This consistency is critical for producing standardized ingredients and for creating products that consumers can trust.
After meeting with different extraction companies, one of the biggest considerations Generation Hemp, Inc. has focused on while considering partnerships and acquisitions, is scale.
An extraction company will utilize certain technology based on several factors, but volume is a big one. Some companies have extraction capabilities in order to process their own plant material (and sometimes others' on a smaller scale), but also play in other areas of the supply chain to vertically integrate. Some companies are focused solely on extraction and will receive and process harvested hemp from growers and/or other companies en masse. For this type of operation, CO2 extraction may be the most efficient - yet, other technologies can still be utilized under one roof.
Both models are attractive for different reasons and both have their place within the space.