CBD Extraction Methods
This form of CBD extraction is actually divided into supercritical, subcritical, and ‘mid-critical’ categories. But supercritical is by far the most commonly used. In fact, it is the most regularly used extraction method of all because it is safe and provides a pure end product.
The purpose of CBD extraction is quite simple; to end up with the cannabinoid (and others) in a highly concentrated form to make it suitable for human consumption.
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).
CBD and THC can be extracted with high efficiency from cured cannabis biomass using supercritical CO2 without a co-solvent. The design of experiments approach allowed efficient sampling of CO2 flow rates, CO2 pressures and extraction times to assess the impact these variables have on recovery of CBD, recovery of THC and total extract yield. The extraction of CBD is largely dependent on flow rate while, the extraction of THC is dependent on both flow rate and extraction time. In terms of cannabinoid recoveries and extract yield the optimal extraction parameters for the biomass used in this study was a flow rate of 150 g/min, an extraction time of 600 min and an extraction pressure of 320 bar.
3 Present Address: La Trobe Institute for Agriculture and Food, School of Life Sciences, Department of Animal, Plant and Soil Sciences, La Trobe University, 5 Ring Road, Bundoora, Victoria, 3083 Australia
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.
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 )