co2 extraction cbdDecember 15, 2021
Response 3: Extraction weight (g)
The effect of factors on THC recovery is not as clear cut as for CBD. While three of the four lowest recoveries were obtained in low flow rate runs, the 2nd best result was also recorded on a flow rate run at 95 g/min. The other factors (time and pressure), and in particular, interactions between these factors also appear to have an impact (Table 3 )
The CO 2 was food grade (99.5% with less than 17.5 ppm water) and obtained from CoreGas (Thomastown, Victoria, Australia). All HPLC grade reagents, water with 0.1% formic acid (mobile phase A), acetonitrile with 0.1% formic acid (mobile phase B) and methanol were obtained from Fisher Scientific (Fair Lawn, New Jersey, USA). Primary standards for CBDA and THCA in acetonitrile, and CBD, CBN, CBC, THC in methanol, at 1000 μg/mL, were purchased from Novachem Pty Ltd (Heidelberg West, Victoria, Australia) as distributor for Cerilliant Corporation (Round Rock, Texas, USA). Glass marbles (12 mm, clear, MoreWine, CA) were used to top up the baskets to fill the void space after packing the cannabis material.
Of course, cannabinoids are not the only metabolites extracted from cannabis biomass. Attard et al . demonstrated that in the SFE of hemp waste fatty acids, fatty aldehydes, wax esters, alkanes, sterols and n-policosanols were extracted along with CBD and that different parameters could alter the amount of these other metabolites 17 . In our study between 32% and 61% of the extract is made up of other components. While our study did not investigate these other metabolites, it is clear that our extraction variables also affect the amounts of these metabolites in our final extract. Different cannabis plants will have different levels of the cannabinoids as well as these other metabolites. It is therefore anticipated that for GMP extraction of any new biomaterial PD would need to be repeated and extraction optimised for that specific cannabis material.
Despite this reduction in extraction weight, there may be value in this approach if there is a need for medicinal purposes. For example, high CBD and low (or no) THC is currently desirable for the treatment of epilepsy in children 26 . For a plant biomass exhibiting high CBD and low THC, this method may be optimised further so that low levels of THC could be removed. Based on the current study the optimised method for maximising the levels of either CBD or THC in the extract would be different. Analysis using Design Expert software suggests that extraction pressure would have the greatest effect in this case (Table 6 ).
Supercritical fluid extraction (SFE) can eliminate the need for these organic solvents during the manufacture of medicinal cannabis extracts. Carbon dioxide (CO 2 ) is the main solvent in SFE. It has GRAS (generally recognised as safe) status and evaporates from the extract when exposed to normal atmospheric conditions. The majority of the published studies on SFE of cannabis are either at small/analytical scale 12 or on hemp material that contains low levels of cannabinoids and very little THC 13 – 18 . There have been studies investigating the solubility of THC and CBN (cannabinol, a degradation product of THC) in supercritical CO 2 suggesting that temperature and pressure are critical parameters 19 , 20 . A more recent study evaluated the use of the Waters Bio-botanical extraction system with the use of ethanol as a co-solvent with CO 2 extraction using four cannabis samples (500 g each) with THCA:CBDA content of 15:1 or more. The authors noted extraction efficiency was highly linked to pressure as well as cannabinoid content of the plant material 21 .
Comparison of CBD, THC and total resin yield for each PD run. CBD: solid black bars, THC: light grey bars outlined in black, Total Extract Weight: solid grey bars.
Experimental design and results of extraction (rows coloured by experiment: white indicates the initial factorial designed runs, light grey indicates mid-point runs, dark grey indicates repeat runs).
Generally speaking, of the initial two-level factorial runs (1 to 8), the high flow rates (150 g/min) produced excellent CBD recovery, with all exceeding 90% of theoretical yield. The yields of each run are compared in Fig. 1 .
A total of 15 extractions were analysed for PD using a two-level, full factorial design of experiments for three variable factors over eight runs (1 to 8, Table 1 ), three mid-point runs (9 to 11, Table 1 ) and four additional extractions were conducted as replicated runs at high flow rates to determine reproducibility (runs 12 to 15, Table 1 ).
This study was undertaken as part of our efforts to obtain a GMP license to produce pharmaceutical grade medicinal cannabis. In order to simplify the regulatory process, and produce a cleaner product, we chose to avoid the use of co-solvents such as ethanol. Process development (PD) is part of GMP. The aim of PD to ensure that the factors underlying any manufacturing protocols are well understood so that any potential source of product variation can be better managed to ensure a safe and consistent pharmaceutical product. As part of GMP PD we used design of experiments (DOE) methodology to develop an extraction method for medicinal cannabis. The aim of DOE was to explore the factors influencing the extraction of cannabinoids and optimise the process for extraction of cannabis material at a pharmaceutical scale.
Result of statistical analysis of Response 1– %CBD Recovery.
DOE is commonly used to optimise engineering processes and to determine which process inputs have a significant effect on process outputs. In a factorial design each variable, or factor, is investigated at predefined levels. With a two-level factorial design each factor can be one of two values. For continuous variables, this is a high and a low level of the variable under investigation 22 . Importantly, the methodology can also determine if there are interactions between the factors in the process. This allows for more rapid optimisation of processes than if single variables were considered independently. This methodology has been used to investigate factors important in extraction of biomaterials. For example, Prasad et al . explored the effect of five factors (pH, ethanol concentration, temperature, time and liquid to solid ratio) on four responses (extract yield, antioxidant capacity, phenolics and flavonoids) for the extraction of the Malaysian fruit, Mangifera pajang 23 . Lee et al . analysed similar factors to optimise the recovery of phenolics, flavonoids and anti-oxidants from palm-kernel by-products 24 . A review of the literature by Reverchon and De Marco demonstrated that CO 2 flow rate, extraction pressure and extraction time are the critical parameters in SFE for the extraction of natural materials 25 . Therefore, these were the factors considered in this study.
The authors declare no competing interests.
Factor B: Extraction pressure, 150–320 bar.
Therefore, the three factors chosen for variance were:
Optimisation of parameters to maximise CBD or THC.
Dried and ground plant material was obtained from the Victorian Government Medicinal Cannabis Cultivation Facility. Biomass was combined from cannabis plants of varying genotype and chemotype to provide 18 kg of material of composite material with CBD:THC ratio of approximately 1:1.5. Coarsely ground biomass samples were cured at 120 °C for 2 hours facilitating the conversion of CBDA to CBD and THCA to THC. Subsamples of the cured material were ground to a fine powder and analysed to provide baseline cannabinoid content data using UHPLC analytical methods as described previously 28 .
The parameters used to assess extraction efficiency were:
When analysed statistically, the CO 2 flow rate is shown to have largest effect on CBD recovery. Extraction pressure had the least overall impact to CBD recovery even when combined with other factors (Table 2 ).
When the concentration of CBD and THC in each extract are compared, it is clear that the different run conditions do affect CBD and THC differently (Table 5 ). The ratio of CBD:THC varies from 0.5 to 1.6. The CBD:THC ratio in the cured material is approximately 0.7 and the data shows that this ratio can be increased if the flow rate is decreased, however, there is significant cost to yield (a maximum yield of 27.5 g compared to 71.0 g)
Result of statistical analysis of Response 3– % Extraction weight.
1 Agriculture Victoria, AgriBio, 5 Ring Road, Bundoora, Victoria, 3083 Australia.
Medicinal cannabis is consumed by patients using a variety of methods including smoking, vaping and consuming infused oils or other edible products. One of the issues associated with smoking or vaping is that the dose the patient receives is not reliable due to both the variability in plant product and the way patients inhale and hold vapour 11 . Vaping and smoking also have well known negative health effects and is particularly undesirable for juvenile patients. For this reason, the production of an extract that can be formulated in various ways is becoming more popular. The cannabinoids are non-polar compounds with low water solubility and can be extracted using a range of different organic solvents including hydrocarbons (e.g. hexane) and alcohols (e.g. ethanol). Extractions using these solvents can be efficient but depending on the final product, can impact regulation and require additional testing. For instance, residual solvent must be defined for medicines under good manufacturing practice (GMP). These solvents can also be costly and due to their toxicity, environmental risk and flammability are less desirable for large scale extractions.
Schematic of the SFE set up. CS = cyclonic separator (cyclone), BPR = manually adjusted back pressure regulator (adapted from Rovetto and Aieta 21 ).
The highest extraction weight of 71 g (7.1%) was obtained under high flow rate (150 g/min), with long extraction time (600 min) at high pressure (320 bar). This method also gave the best recoveries of THC and CBD (Table 3 ). The lowest extraction weight of 4.2 g (0.42%) was obtained with low flow rate (40 g/min) and short extraction time (240 min) even though the extraction pressure was high (320 bar). Runs 5–8 produced very similar quantities (50.8 g to 56.3 g) even though the extraction times were 240 min and 600 min, indicating that a longer extraction time did not necessarily increase the amount of extract. The three centre point runs (9–11) produced extraction weights as good or better than runs 2–8. The last four runs (12–15) were duplicates of runs 1, 5, 7 and 8. With the exception of run 13, the yields from the duplicate runs were similar (within 3 g).
Response 2: %THC recovery.
Response 1: %CBD recovery.
Cannabis is an herbaceous flowering plant of the Cannabis genus (Rosale) that has been used for its fibre and medicinal properties for thousands of years 1 , 2 . In recent decades medicinal cannabis has become legal in several jurisdictions and the possibility of legalisation is being explored in many more 3 – 8 . The chemistry of cannabis is rich and varied; it includes phytocannabinoids, terpenes and phenolics, and each of these classes contain compounds with biological activity 9 . The cannabinoids, in particular, Δ 9 -tetrahydrocannabinol (THC) and cannabidiol (CBD) have been the main focus of bioactive research. These cannabinoids are naturally present in planta as their acid analogues Δ 9 -tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA). THCA and CBDA are the major cannabinoids found in cannabis although more than 90 cannabinoids have been reported 9 . The acids degrade naturally to the corresponding neutral species at a slow rate via non-enzymatic processes 10 . Decarboxylation is facilitated by heating (e.g. when smoked) (Citti et al . 2018). Many medicinal cannabis preparations are consumed in an oil or are made from an extracted resin and not smoked. In this case, the dried cannabis material must be ‘cured’ prior to, or during, extraction ( i.e . heated for a specific time and temperature to ensure maximum decarboxylation). THCA is the main psychoactive cannabinoid followed by cannabigerolic acid (CBGA).
PD was designed and the data interpreted using Design Expert (Stat-Ease, version 10), which is a commercial, off-the-shelf Design of Experiments package. The system uses standard statistical methodology, such as analysis of variance (ANOVA), to determine the factors influencing responses that are critical to the final product (e.g. extraction weight). Additionally, it considers interactions between the different factors to determine if there are any synergistic effects between them.
What’s most important to remember is that, even when dealing with the exact same hemp strain, the extraction method utilized to create the oil can produce very distinct results. Even at a chemical level, you can tell which method has been used to create a specific CBD product – and that can make the difference between you getting the results you want and feeling like you’ve wasted your money.
CBD products are becoming increasingly popular, leaving many consumers wondering where to start. While it’s true there are almost more options than you can count in the world of CBD today, there’s one important factor everyone should consider before buying and consuming a hemp product: How it’s made.
Like anything, CO2 extraction isn’t perfect. While a popular and safe choice, there are some downsides to the process that should be considered, whether you’re a consumer or a CBD business owner. First, however, let’s focus on why CO2 really is one of the best extraction methods being used today, especially for CBD products.
The Pros and Cons of the CO2 Extraction Method.
There are, of course, a few reasons why CO2 extraction isn’t the right method for everyone. Below are a few of the cons to consider…
CO2 cannabis extraction works so well because of its ability to use pressurized carbon dioxide (that’s the CO2 part in case you missed chemistry class) to extract CBD from plants. Although other extraction methods can get the job done, CO2 works better because it becomes a solvent when frozen below -69 degrees Fahrenheit, turning it from gas form to its liquid state, and without presenting any of the risks that other solvents carry.
In terms of CBD products, how the hemp oil is extracted drastically impacts the final result. Although all methods are attempting to do the same thing – create a highly concentrated version of cannabinoid for human use, there are definitely right ways and wrong ways to extract the oil. And, of course, even when you’ve narrowed it down to the right ways to perform the extraction (keeping in mind the purity and potency, among other things), there are still several different “right” ways being put into practice. All of this makes it extremely difficult for consumers to know which method really is best – and where they should be spending their money.
Far from inexpensive, the equipment needed to extract CBD with CO2 is highly technical machinery that often is separated into three distinct chambers. As expected, each chamber has its own specialized task:
One of the most trusted ways to extract CBD from cannabis or hemp, the CO2 extraction method is categorized into three different types: supercritical, subcritical and mid-critical. Most professional and reputable companies use the CO2 extraction method simply because it’s the safest way to create the purest product.
Clean and efficient, CO2 extraction is only used by professionals, as the technical knowledge needed to operate the equipment (not to mention the expense of getting your hands on it) keeps amateurs and hobbyists away.
Understanding How the CO2 Cannabis Extraction Method Works.
When using the supercritical CO2 extraction method, the liquid CO2 is pushed to the point of becoming a property that is halfway between a gas and a liquid. Known as a “supercritical” state, the CO2 now functions as both a gas and a liquid, making it ideal for chemical extraction because it doesn’t denature or damage the substance. For CBD products, which are either consumed by ingestion or absorption, making sure that the hemp oil is as safe and pure as possible, without losing any of the critical components that make it effective, is key. When done properly, CO2 extraction pulls out all of the essential trichomes and terpene oils, ensuring that the products you buy really deliver the benefits you’re looking for.
Like anything you choose to consume, you have a choice in what you buy. While some consumers will decide that they’re fine using CBD products created using a different method, especially if it means they save money, a lot of people choose to exclusively use CO2 extracted CBD simply because it’s the safest most effective way to ensure they’re getting the benefits they want. At the end of the day, remember that how your CBD products are made will ultimately affect the end product, as well as your overall health.