The solute will then be transferred from the solid phase, the biomass, to the supercritical phase, in this case, the supercritical carbon dioxide. This transfer will continue until the solvent and biomass reach equilibrium for the quantity of solute in each. The specifics of the capacity of the CO2 for the target extracts will be determined by the solvent density, which will play a large role in determining how the contact equilibrium process plays out regardless of biomass variability.
Why is biomass potency?
Biomass potency varies widely across farms and cultivars, so testing before extraction to determine levels of target extract (such as the Essential oil, CBD, and THC content) is essential.
Most extraction facilities do not have in-house testing labs; many smaller operators collect biomass samples and send them to outside labs for analysis. However, results can vary between labs due to inconsistent testing protocols. To achieve more predictable results, consider investing in small-scale testing systems that utilize UV light to determine target extract (such as the CBD and THC content of cannabis) levels within the biomass. Their accuracy approximates full lab testing but by conducting the analysis in-house, you can better control the testing procedures and achieve consistently reliable results.
The factor in cannabis CO2 extraction that greatly influences potency is how much cannabis flower is included in biomass.
In the cannabis and hemp industry, biomass typically refers to the plant material left over for processing after the highly prized flower (colas or buds) of the plant has been removed. The flower contains the highest THC levels, so the majority of flower harvested in the United States goes into smokable products. As much as 40 percent of flower in some states, however, is added to biomass for extraction of cannabinoids, which will be used to manufacture edibles, infused and vaping products, as well as extractions for dabbing, distillates, and live resin.
When purchasing biomass, assessing its cost on a dollar-per-gram of cannabinoid basis is perhaps the most accurate method of assessing the cost of your inputs. You need accurate potency test results to get there.
Extraction time and biomass potency
The higher the target extract(such as essential oil) content in the biomass, the longer the extraction time required, which has been done many times in experiments in our laboratory, such as oil extraction from hazelnuts and oil separation from lecithin, which took a lot of time.
The type and target extract load of the biomass to be extracted is extremely important in determining the total solvent needed and overall run time for the extraction. There is no one-size-fits-all run time for any botanical variable such as cannabis and hemp. If you are introducing too little solvent you will be leaving cannabinoids behind in the raffinate. On the other hand, if you are extracting well into the DC stage you will be wasting time in your extraction system that could be better used loading the column with fresh material and proceeding to the next extraction.
What is the extraction time?
CO2 extraction has a lower throughput than ethanol but utilizes an inert gas for processing instead of a liquid solvent or explosive gas. CO2 extracts essential oils from plant seeds and rhizomes. The pressure usually used is between 150 and 350 bar, then we recommend a batch time of 2 hours (the time for a batch of cannabis extraction is almost 2 hours), of course, including the loading and unloading process.
Because too long extraction time will increase the cost of extraction because the extraction efficiency of CO2 is very high under the conditions of correct extraction pressure and temperature and CO2 flow rate.
In addition to the biomass potency and extraction equipment, other important factors that influence extraction time include:
- The mill size determines how much biomass fits into the extraction vessel and can be extracted per cycle.
- Downtime for maintenance and cleaning.
- Advanced extraction techniques involve chilling the solvent and pre-freezing the biomass.
What is the right temperature for biomass extraction?
The temperature of the solvent, along with the mill size of the biomass, will determine the amount of time required for the efficient extraction of the primary derivatives.
In CO2 extraction, 30.77 °C (87.4 °F) is the critical line. Below it, extraction requires subcritical processes. Extraction above it requires supercritical processes which run faster and yield more potent products. Usually, the temperature of CO2 extraction is between 50-60 °C.
In ethanol extraction, we recommend chilling your process ethanol to -40 °C (-40 °F) prior to extraction and freezing your biomass if possible, to efficiently capture cannabinoids while minimizing the extraction of fats, lipids, waxes, sugars, and chlorophyll. Ethanol is a polar solvent and dissolves gums, sugars, fats, and other undesirable molecules but not the target oils. Additional filtration and processing are then needed to remove the undesirables. Lowering the ethanol temperature to between -35 °C (-31 °F ) and – 55 °C (-67 °F) will convert it to a non-polar solvent that only dissolves the cannabinoids.
How many solvents do you lose during each extraction?
During extraction, the cannabis or hemp biomass is soaked in a solvent and agitated in a mechanical centrifuge. Most of the solvent is recovered. But depending on the process and equipment involved, a small amount of the solvent remains in the biomass or is lost when the extraction vessel or other valves and connections are opened.
Despite being a closed-loop CO2 extraction system, it inevitably loses some gas. In a closed-loop CO2 extraction system equipped with a gas recovery system, approximately one-third of the biomass weight gas is missing from one batch of extraction. That is when you extract 300 pounds of biomass, you should be prepared to lose 100 pounds of gas.
- “5 Questions Every Cannabis Extractor Should Be Able to Answer”, Analytical Cannabis, Visited 10 Aug, https://www.analyticalcannabis.com/articles/5-questions-every-cannabis-extractor-should-be-able-to-answer-313467
- “WHAT’S IN YOUR BIOMASS?”, Project Extract, Visited 10 Aug, https://www.projectextract.com/projects/the-truth-about-throughput-part-ii-whats-in-your-biomass