Q: What solvents can you use in an extraction? I know that you can use ethanol and, I think, you said butane, too.
RVL: In the cannabis industry, there are three main groups of solvents for extraction. CO2, hydrocarbons, and alcohols. CO2 is my least favorite, when you compare cost of the equipment versus the thruput, ethanol wins hands down every time. CO2 has very long cycle times, and operates at extremely high pressures (upwards of 5,000 PSI!) It is very hard to load the biomass into the equipment, usually having to climb a set of stairs every time on larger systems, and it also pulls a lot of water along with the cannabis oils, which is extremely frustrating to remove prior to decarboxylation. Hydrocarbons such as butane or propane have the advantage of preserving terpenes for higher end products, due to it’s low boiling point. These terpenes would be removed anyway in post processing during the quest to isolate the cannabinoids. Plant fats and waxes are also highly soluble in hydrocarbons, and the technology is also rather hard to scale up to a commercial level. Due to their low boiling point and high pressure, you need a stricter license type to deal with these gases, and special care needs to be taken with the facility design to deal with these flammables. Typically a C1D1 (explosion proof) room with a special gas detector and safety interlocks are required for butane/propane extraction. You can also extract with heavier boiling point hydrocarbons such as pentane, hexane, or heptane, but these also have the disadvantage of pulling fats and lipids.
Hydrocarbon extracts and CO2 extracts are usually defatted in a post-process using ethanol anyways, called winterization. This brings me to the last solvent group, alcohols. Ethanol has the advantage of having the perfect polarity to extract cannabis oil, while leaving undesirable compounds behind. The caveat is the extraction has to be done cold, around -40F, to leave the sugars and lipids in the biomass. This is where our equipment excels, no post-processing techniques are required to clean up the product, this reduces the time, equipment, and space it takes to get from biomass to end product.