Ethanol extraction is a simple concept. Ethanol is a hybrid molecule meaning it has both polar and nonpolar properties. This means ethanol can dissolve both water soluble (polar) and fat-soluble (nonpolar) molecules. Ethanol is a great solution for extraction, because the polarity can be changed slightly depending on its temperature when introduced to the plant material. The colder the Ethanol is, the more nonpolar it acts, giving the solvent a higher affinity to Cannabinoids and Terpenes, as these molecules are fat-soluble. Warmer temperatures will pick up more of the water soluble (polar) molecules like Chlorophyll and Lipids, which can be beneficial to extractors looking for a full plant extract.
Cannabis or Hemp trim, flower, and biomass are loaded into one of the many types of extraction vessels (most commonly a centrifuge) and soaked with ethanol. This mixture begins a washing process where the compounds in the Cannabis plant are extracted and dissolved into the Ethanol. The solution is then moved into a solvent recovery process where the ethanol is separated from the extracted Cannabis molecules. In the final step of extraction, the small amount of remaining solvent is evaporated and removed from the extract as much as possible. Through this process, enough heat is applied to decarboxylate the Cannabis extract. The process ends with a thick, often dark color oil referred to as Full Spectrum Cannabis / Hemp Extract or Cannabis/Hemp Crude Oil, as the appearance can resemble crude oil itself.
Now that we’ve given you a brief overview of the ethanol extraction process, we can now discuss the types of equipment used to perform the extraction process.
Jacketed and insulated tanks, heat exchangers, and cryogenic temperature control units are
typically used in this process. Ethanol is then pre chilled before washing the plant material in the extraction process. This allows the user to chill the ethanol to optimal extraction temperatures before entering the extraction vessel minimizing the extraction of undesirable compounds eliminating the need for further post processing known as winterization.
The first piece of equipment is the extraction vessel. There are several vessels used to load the Cannabis or Hemp into before soaking the plant material with Ethanol. The most commonly used vessel is the centrifuge.
A centrifuge is a machine with a rapidly rotating cylindrical basket that applies centrifugal force to its contents to separate liquids from solids. Hemp and Cannabis processors typically load the material into a mesh bag to hold the material inside the basket. Ethanol is then loaded on top of the material and allowed to soak for a specific amount of time.. The longer the soak time, the more plant material will dissolve into the ethanol. Processors try to find the optimal amount of soak time to pull as many cannabinoids as possible, while pulling as few undesirables as possible.
Once the material has soaked for the designated amount of time, the centrifuge will spin at very high speeds, allowing the Cannabinoid infused ethanol to spin out of the bag holding the plant material, this process works very similar to a clothes washing machine. The material is then sent to a holding tank to be further processed. The ethanol may be used multiple times before the solution becomes saturated with Cannabinoids to fully extract the material. Reusing the ethanol multiple times can help optimize the extraction process by allowing the extractor to evaporate less ethanol in the downstream solvent recovery process.
The solution is then ejected from the extraction vessel and sent to a storage tank. Storage tanks are used to house both clean solvent and solutions containing a mixture of solvent and Cannabis or Hemp oil. At this stage, the solution has a very high dilution ratio, meaning there is very little concentrate and a large amount of solvent.
The next step in the process is ethanol evaporation; commonly referred to as solvent recovery. This is where the solvent (ethanol) is separated from the Cannabis or Hemp oil and recovered to be recycled and reused in the starting extraction process. With a high dilution ratio, Cannabis and Hemp processors first use an evaporator to concentrate the solution down to a lower dilution rate.
There are many types of evaporators that can be used for this application: rising film evaporators, falling film evaporators, short tube vertical evaporators, plate evaporators, etc. One of the more common evaporators used in Cannabis and Hemp concentration are rising film evaporators.
Rising film evaporators are basically vertical tube and shell heat exchangers. The solution flows up externally heated tubes, which causes the Ethanol to turn to vapor. The Ethanol vapor is pulled with vacuum to a condenser which cools the vapor, turning it back into a liquid. The clean Ethanol is stored in a collection vessel and can be reused in the extraction process over and over.
Once the solution is semi evaporated, it is sent to a concentrator.
In the concentrator, more vacuum and heat are applied while the Crude Cannabis or Hemp oil is agitated, allowing Ethanol to evaporate out of the solution. Again, the Ethanol vapors are pulled with vacuum to a condenser, where they are converted back to a liquid and stored in a clean solvent tank to be reused in extraction once again. In the concentrator, enough heat is applied in this process to Decarboxylate the oil. Once the product is decarboxylated and the majority of the Ethanol has been evaporated out of the concentrate, the Crude Cannabis or Hemp oil is ready to be ejected.
Crude oil can be used for product formulation, or be sent to further refinement such as short path molecular distillation. For more information on molecular distillation check out our blog. While Crude oil is used for certain products, most infused Cannabis and Hemp products use further refined products like Distillate or Isolate.
Now you understand how Ethanol extraction is performed to extract and refine Cannabis and Hemp. Take a look through the links throughout this blog to see the equipment used to perform these processes. You can also learn more about the downstream refinement processes by visiting our blog page.