Hydrocarbons are very non-polar compounds made of only carbon and hydrogen atoms. These compounds are manufactured by the petrochemical industry and are highly flammable and explosive at certain vapor concentrations. They are selective for the non-polar cannabinoids leaving chlorophyll and color pigments. Hydrocarbon are also extremely volatile, meaning that they can be easily evaporated from the cannabis matrix to form different forms of shatter. Hydrocarbon are also able to extract a greater amount and variety of terpenes than both the ethanol extraction and supercritical carbon dioxide extraction techniques.
Supercritical Carbon Dioxide
Supercritical carbon dioxide is a non-polar solvent that is pressurized to at least its minimum critical pressure of 1070 psi (72. Atm or 73.8 bar) and at least its minimum critical temperature of 87.8°F (304.13K or 31.0°C). Typically, scCO2 extractions in commercial cannabis extraction setting operates between 1500 – 5000 psi. Carbon dioxide at its supercritical state can effuse through solids like a gas and dissolve materials like a liquid. The extraction strength can also be increased by increasing the pressure of carbon dioxide in the system. CO2 is an odorless, colorless and fairly inert gas. The solvent like behavior of supercritical carbon dioxide along with it non-toxic nature make it an excellent way to extract compounds from products being consumed. Supercritical CO2 is used in the decaffeination of coffee beans and in making vanilla extract sometimes. These food applications have been repurposed to the cannabis industry.
One drawback with supercritical CO2 is that it doesn’t have great solubility with cannabinoids. As a result, extractors in the industry have a long cycle time of at least 2 hours and the more potential for decreased extraction efficiency depending on time and amount of product used. Supercritical carbon dioxide extraction equipment is also the most expensive of any technique.
Ethanol extraction can be done in cold, room temperature, or hot conditions. Hot ethanol extractions often extract unwanted chlorophyll and plant waxes due to the polarity of ethanol which require several processing steps to fix. Cold or room temperature (to a slight extent) ethanol extractions mitigate this issue with plant waxes and chlorophyll. In the industry ethanol extractions are usually performed at -40C or below to inhibit chlorophyll, wax, and lipid extraction during the process. At the end of the process, the ethanol is boiled off, which both decarboylate the carboxylic acid form of certain cannabinoids (THCA, CBDA, CBGA, etc.) and leaves a high purity cannabis oil.
Ethanol extraction of cannabinoids generally has the lowest startup costs. You don’t need to deal with the immense pressures needed for supercritical carbon dioxide extraction and has less flammability compared to hydrocarbons.