The cannabis plant contains important compounds that are fractionated from the biomass by using extraction methods. In the plant, acidic cannabinoids like tetrahydrocannabinolic acid (THCa) dominate. Decarboxylation is a chemical process that causes THCa to convert to delta-9-THC via heat and time.
The heat and time used must be precise as it is critical to prevent THC from transforming into cannabinol (CBN). Tunable carbon dioxide (CO2) extraction systems use lower temperatures for a process called cold separation. The cold separation process can protect plant oils by keeping them at lower separator temperatures than the temperatures used for extraction.
Because heating cannabis extracts via vaping or dabbing effectively decarboxylates THCa to THC, and because continued heat can turn THC into CBN, preventing decarboxylation during extraction is desirable. Green Mill Supercritical Throughput Boost Method seeks to extract THCa instead of THC because the solubility of THC in supercritical CO2 is similar to other undesirable compounds. Says Jesse Turner of Green Mill: “traditionally operators must choose between better overall purity or faster extraction.” Rather than increasing pressure, which increases the CO2 density, the Throughput Boost Method increases the vapor pressure through the use of a higher temperature. Says Turner, “The method delivers a huge bump in efficiency in the extraction of THCa, while leaving behind the undesired compounds and producing a clean, pure extract requiring lower levels of post-extraction processing.”
THCa can also be concentrated to the point of crystallization within the CO2 extraction system’s separators, producing diamonds. Says John Van Antwerp, Director of Chromatography at Thar Process, “Many people believe the only way to get THCa crystals or to make shatter is using by using butane but this can also be accomplished using CO2 extraction as long as you adjust the density of the CO2 (pressure and temp) on the collectors so that the THCa can be selectively dropped out and the majority of the neutrals moved to the next collector.”
With the scope of the cannabis industry spanning across the globe, the need to find environmentally sound ways to create boutique products is paramount to scalability. Utilizing the flexibility of CO2 extraction offers promise for everything from terpene extraction to retain a given cultivar’s profile, or for crystallizing THCa for direct use or insertion into other products.