2. Commercial Cannabis Extraction Methods
2.1. General Considerations
- Extraction efficiency, the percentage of bioactive compounds recovered through the entire extraction process;
- Extract quality and consistency, including the purity or “potency” of cannabinoids in the extract and also the relative amounts or “profile” of other potentially synergistic compounds such as terpenes;
- Throughput capacity and scalability, assessment of the extraction method and its efficient implementation at commercial scales vs. market demand;
- Environmental control, e.g., carbon footprint and safety, i.e., minimize risks to the consumers and worker safety.
- Decarboxylation, the process of converting non-active native acidic cannabinoids into their active, neutral forms via a thermal reaction;
- Winterization, the process of removing plant lipids and unwanted waxes by a secondary solvent, freezing and filtration;
- Decolorization, the process of removing chlorophyll and unwanted pigments;
- Secondary purification, the process of further purifying the extract to increase the potency or alter the composition of cannabinoids and other components, via various methods including distillation, chromatography, or crystallization.
2.2. Scale-Up Considerations
2.3. Available Methods Currently Used for Commercial Cannabis Extraction
- Supercritical CO2 (SC-CO2) extraction
- Pressurized gas (hydrocarbon) extraction
- Conventional organic solvent extraction
2.3.1. Supercritical CO2 (SC-CO2) Extraction
2.3.2. Pressurized Gas (Hydrocarbon) Extraction
2.3.3. Conventional Organic Solvent Extraction
3. Microwave-Assisted Extraction
3.1. General Considerations
3.2. MAE of Cannabis via MAPTM
- Continuous-flow method at atmospheric pressure which allows for much higher volumes of cannabis biomass to be processed in much less time than existing extraction methods.
- Achieved higher rates of consistency and quality because the process does not require stopping and restarting material flows.
- Scale-up to industrial scale without the need to purchase an endless supply of new machinery and without the use of pressurised batch vessels.
- Eliminates additional steps required in most extraction methods, such as winterisation.
- Ability to achieve high extraction efficiency at industrial scale. Typical recovery of active compounds via MAE is up to 95%.
- The contact time between the biomass and solvent before, during and after microwave treatment can be adjusted much more easily.
- It is possible to precisely control biomass residence time in the microwave zone and—if desired—separate the biomass from the solvent very quickly after treatment, or continue contact for any length of time at any temperature, depending on the desired outcome.
- The use of multiple microwave field deposition points through the use of a split waveguide and a “ridge wave deposition” allowing for non-uniform dispersal of the wave from the inlet to the outlet to account for changing dielectric properties as the material is treated.
- It has an automatic impedance matching unit that allows for constant, automatic adjustment of the field strength and microwave energy absorption maximization.
- It has a built-in mechanical agitator with variable speed control to randomize movement of biomass thus making the field uniform for the materials at all times.
- It is fully automated (operators simply input desired MW parameters on an HMI and it runs itself while connected to the plant PLC systems).
- It is fully ATEX or “hazardous zone” classified, meaning it can be used with any flammable liquid and be completely safe.
3.3. Economics of MAE
- Badly designed reactors (geometry & chosen microwave frequency) vs. quantity & type of reaction mixture.
- Changes in the microwave absorbance of the reaction mixture due to modifications of its temperature, chemical composition, and phase when applicable (e.g., evaporation). This results in a gradual or rapid shift in the power absorbed by the reaction mixture and therefore, for a fixed Pf, an increase in Pr, which is a common problem in obtaining good quality products with good energy efficiency.
Conflicts of Interest
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|Conventional Extraction||Microwave Assisted Extraction|
|Mechanism via diffusion||Pressure-enhanced mass transfer|
|Concentration gradient of actives between the biomass and the solvent is the driving force||Microwave energy is selectively absorbed by the residual water present in the biomass cells|
|Diffusion is slow, particularly as the actives become more concentrated in the solvent||Results in rapid pressure buildup within cells leading to a pressure-driven mass transfer of actives (pop-corn effect)|
|Eventually reaches a saturation point||Extraction is very fast and not limited by an equilibrium state—transfer continues as long as energy is applied|
|Requires high solvent ratios and multiple extraction stages to achieve reasonable recovery of actives||Results in short extraction times, reduced solvent requirements and fewer extraction stages|
|Run||Mass of Biomass kg||Purity of Cannabis Extract THC %||THC Recovery in the Extract %|
|1||100||61.4 ± 0.04||92.6|
|2||100||55.1 ± 0.4||93.4|
|Frequency||915 MHz a||2450 MHz a|
|Number of generators to deliver 75 kW||1 (×72 kW)||12 (×6 kW)|
|Generator price b|
Total price for microwave generators
1 × 90 k$
= 90 k$
12 × 10 k$
= 120 k$
|Microwave transmission line (waveguides, impedance tuners, and other waveguide components required to transmit the microwave power from the generator to the reactor)||1 × 15 c k$|
= 15 k$
|12 × 5d k$|
= 60 k$
|CAPEX (microwave generators and microwave transmission line)||105 k$||180 k$|
|Main consumable, magnetron|
|Operation lifetime e|
| 6000 h|
= 8 k$
| 7000 h|
= 30 k$
|Mains electricity consumption f,g||~85 kW||~100 kW|
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