The cannabis market’s rise brings with it both new challaneges, especially around green methods for production, such as cannabinoid leaching recovery processes.
Sustainable and effective extraction techniques are necessary to satisfy customer demands while reducing environmental impact as the demand for cannabinoid-based goods keeps increasing. The pH-controlled aqueous leaching method is a promising and ecologically friendly extraction technique that has advantages over traditional organic solvent extraction procedures.
Cannabinoid extraction methods
The traditional method for extracting cannabinoids from Cannabis sativa flowers is organic solvent extraction. However, due to its drawbacks, which include low selectivity and environmental issues, it is less suited for large-scale, sustainable production.
Greener solvents like methanol and ethanol have gained popularity recently. However they still have drawbacks, such as flammability, which limits their scaling up abilities. Although other-techniques like supercritical fluids, deep eutectic solvents, and ionic liquids have shown promise, their general adoption can be hard because of large capital costs and technical difficulties.
Leaching methods: liquid-liquid extraction
But now we’ll talk about liquid-liquid extraction (LLE), a different strategy that has attracted interest in the cannabis market. LLE uses an aqueous solution as the leaching solvent, because there is no need for solvent evaporation. This option has a number of advantages including simplicity, lower investment costs and energy consumption. Moreover, it is sustainable due to the use of low-volatility and recyclable organic solvents. LLE is a viable alternative for large-scale cannabis manufacturing because of its track record in other sectors, such as the opium industry.
Despite LLE’s potential, the trick is to make the process of leaching of cannabis tissues as efficient as possible. Due to the limited solubility of cannabinoids in water, researchers have added tiny organic molecules to the aqueous phase to increase solubility. These modifiers, however, frequently call for large concentrations, raising security issues.
Recent research has looked at the potential to increase solubility by using solutions with high pH to extract cannabinoids from hemp. Systematic research is nonetheless insufficient, particularly for fresh plant tissues and high-THC cultivars.
Recent studies in this area aim to create an organic solvent-free, pH-controlled green leaching method for recovering cannabinoids from cannabis tissues. The study examined a variety of cannabis chemotypes and sources. It included fresh, dry, and decarboxylated cannabis, as well as high-THC and high-CBD cultivars. The researchers assessed the effectiveness of cannabis leaching and the stability of cannabinoids in leached solutions. They also looked at the impacts of leaching pH and solid/liquid ratios.
Can LLC be useful?
The results were promising. The study showed that at pH levels of 12 and above, all main cannabinoids, especially the acidic versions, may be successfully leached into aqueous solutions. This alkaline leaching technique exceeded methanol leaching in terms of performance. This indicates that methanol might take the place of flammable solvents and provide a more environmentally acceptable alternative.
Furthermore, the time-consuming drying stage might be avoided by directly leaching fresh cannabis with alkaline solutions.
However, the alkaline leaching method at pH 13,5 demonstrated slightly poorer efficiency for high-THC decarboxylated cannabis. It was yielding only 11–50% of the amount produced through methanol leaching at the same solid/liquid ratios. This gap may be explained by the neutral cannabinoids’ weaker acidity. It makes them more difficult to dissociate in alkaline solutions than their acidic equivalents.
Thus, leaching efficiency for high-THC cannabis can be improved by adjusting variables like solid/liquid ratios and avoiding high-temperature treatment before the leaching step.
Studies on the leached solutions’ stability were also done. In alcohol- and pH-12,5-leached solutions, THCA and THC demonstrated stability, with very slight concentration decreases seen with time. However, CBDA degraded more quickly in solutions with a pH leaching effect of 12,5. The leached solution could be processed quickly in successive LLE stages, the storage temperature could be lowered, or the leached solution’s pH could be changed to neutral or acidic conditions.
Green processing methods for cannabis and cannabinoid
In order to enrich and recover high-purity cannabis from aqueous leached solutions, a whole LLE method might be developed with the success of this work as a good starting point. The one goal of future research is to find substances present in the fractions that contain cannabinoids. Another aim is to optimise precipitation conditions to maximise efficiency and minimise losses.
The cannabis sector can both increase its sustainability and meet the demand for cannabinoid-based goods. Improving the leaching strategy is one of the options to do it. Organisations, such as EIHA promote hemp as a sustainable source. What is more, hemp presents a potential to be an alternative crop in some countries dealing with climate changes. Thus, any processing improvements will be necessary to stay on a good track in the cannabis market.