Cannabis Extraction MethodsDecember 13, 2018
While there are various cannabis extraction methods to choose from, there are advantages and disadvantages to each method.
Water, just about the most polar solvent, is repelled by the lipid bilayer, and cannabinoids have no solubility in it. Most organic solvents are relatively non-polar and are capable of extracting the oils within the plant matter. Non-polar solvents commonly used in virtually all cannabis extraction methods include hydrocarbons, alcohols, and supercritical carbon dioxide. Let’s examine the benefits and downsides of each.
Hydrocarbons, as the name implies, are very non-polar compounds made up of only hydrogen and carbon. Almost all hydrocarbons are manufactured by the petrochemical industry and are components of natural gas, diesel fuel, and gasoline. As you might expect, these compounds are highly flammable: but they are efficient cannabinoid extractors. While all hydrocarbons could potentially be used for cannabis extraction, in practice only the lower hydrocarbons such as propane and butane are used. Why are these highly volatile, extremely flammable solvents employed? Well, they work, and they evaporate very easily, making recovery of the dissolved cannabinoids easy. The lower hydrocarbons are also fairly selective for the non-polar cannabinoids, leaving the colored pigments and chlorophyll behind. The ease of solvent removal (due to the hydrocarbons low heat of evaporation) allows the resulting oil to be worked into the various forms of “shatter”, “bubble hash” and the like.
Unfortunately, the properties of lower hydrocarbons that are ideal for cannabis extraction (high volatility, low viscosity) make them extremely dangerous. All the lower hydrocarbons form explosive mixtures (butane will explode at concentrations between 2 and 8% in air) leading to the well-documented explosions at hydrocarbon processing labs.
Supercritical CO2 Extractions
scCO2 is run at many times atmospheric pressure and uses a large quantity of compressed carbon dioxide. Aside from the harmful effects, CO2 has on the environment, the high pressures and large volumes of the highly poisonous carbon dioxide lead to major safety concerns. Engineering controls must be in place in the event of CO2 release, or else rapid suffocation is possible in the event of failure. Because of the extreme pressures involved, scCO2 systems must be made of pressure rated steel, increasing the capital outlay for startup and dramatically increasing the need for diligent preventative maintenance.
scCO2 is an efficient extractor, perhaps too efficient. Everything gets stripped from the plant material, including waxes, pigments and cell-wall fragments. Thus, “winterization” is needed to obtain usable extracts. Winterization is done by dissolving the sludge from the scCO2 apparatus into ethanol, chilling and filtering off the mass of unusable waxes, etc., and then evaporating the ethanol.
scCO2 extractions are really a set of two extractions run in series: the CO2 run followed by an ethanol extraction.
This begs the question: why do the scCO2 pre-extraction when an ethanol extraction by itself would do the job?
Alcohol Extractions (Ethanol)
Alcohol extraction of cannabis has been done for centuries. Cannabinoids have excellent solubility in lower alcohols such as ethanol and isopropanol, provided that the water content of the alcohol is low. Ethanol tinctures of cannabis are a part of the Pharmacopeia, and before prohibition, were readily available for various ailments.
While many lower alcohols can be used for efficient extraction of cannabinoids from cannabis, ethanol is the preferred solvent, since it is relatively non-toxic.
Our various CBD products are produced using both scCO2 and Ethanol extraction.