Cannabis Processing Operations

Cannabis Processing Operations

The Process of Processing

Operations described in this document include the following methods of cannabis processing; pre-processing grinding and steam distillation, primary ethanol extraction, primary butane extraction, winterization, filtration, purging, rotary evaporation, distillation using a molecular still and post-processing terpene infusion. Other operations related to the production and of cannabis products include primary and secondary packaging. 

Prior to processing, all cannabis biomass must be tested to ensure the absence of contaminants like pesticides. All biomass is quarantined until samples return clean. Contaminated biomass is securely stored until it can be properly disposed of. Samples of the plant material undergo a microextraction. The process is relatively simple. The material is placed in a mason jar, blended with acetone and homogenized for at least 15 minutes. Next, the solution is poured on a thin sheet and placed under a fume hood. Once all the acetone has evaporated, the resulting extract is harvested, placed in a sample jar, and sent in for testing. If the sample tests clean, the material is cleared and removed from quarantine. 

Pre-processing operations encompass all processing that occurs to the cannabis trim or “biomass” prior to primary extraction. At most facilities grinding is used as a pre-processing technique. Grinding involves cutting or chopping cannabis plant material into smaller-sized particles through use of a wood chipper, shredder, mulcher or blender. The grinding process enhances the amount of surface area and facilitates a more efficient extraction process. Some facilities use Steam Distillation is used as a pre-processing technique, intended to capture terpenes prior to extraction, where they are usually destroyed. Terpenes are very light lipids and are highly volatile in nature, for this reason, they do not typically make it through most extraction and refinement techniques involving the use of heat. Steam distillation utilizes steam to extract terpenes from biomass. 

A steam distillation unit typically consists of a hot plate, boiling flask, biomass flask, still head, condenser and receiver. Steam is produced by bringing distilled water, contained in a boiling flask, to a boil. This steam travels upward into the biomass flask where essential oils and water-soluble plant compounds are removed into the vapor stream. The vapor stream travels through the still head, connected just above the biomass flask. The still head connects to a cooled condenser coil through an L shaped connection at the top. The vapor stream passes through the still head, to the water-cooled condenser where it condenses, and collects in the receiver. In the receiver, the essential oil layer phase separates. The receiver is specially designed to retain both heavier-than-water oils and lighter-than-water oils, while allowing excess water, containing the water-soluble compounds, to be drained out and collected separately (see figure 1). In this way, the essential oils are condensed. 

The resulting condensed terpene solution is collected using a tinted glass vial or mason jar. The terpenes or “essential oils” are lighter than water so they sit on top of the water in the receiver which is, essentially a separator flask. A clear line can be seen where the water ends and essential oil layer begins. The receiver flask features a drain at the bottom that allows the heavier liquid, in this case, water, to be drained first. The water is drained while watching the line of separation and taking care not to remove any essential oils. Once the water is drained, the essential oils are collected and stored wither in a freezer or in a cool dry location. 

After undergoing steam distillation, the cannabis plant material is removed from the biomass flask and dried on mesh screens on racks in a drying room. The drying room typically contains a dehumidifier to sap moisture from the air and facilitate an efficient dry process. This prevents mold or mildew from developing on the material. Once fully dry, the cannabis plant material is ready to undergo primary extraction.

Primary Extraction refers to the initial extraction of cannabinoids from biomass. There are several extraction techniques used to extract cannabinoids, the active ingredients, from cannabis plant material. The two most commonly used types of primary extraction utilizing solvents are ethanol extraction and butane extraction. Ethanol extraction, involving the use of a of a centrifugal extraction unit, utilizes a process of agitation of biomass in an ethanol solution. The biomass is contained in a filter bag that essentially acts as a tea bag. The product of this is an “ethanol-cannabis tea” commonly referred to as “loaded solvent”.  

Cannabis plant material is first loaded into a specialized micron filter bag. Figure 2 shows the cannabis plant material contained in a filter bag. This filter bag is loaded into the extraction vessel. Next, the lid is secured with a series of heavy-duty metal clamps. Figure 3 shows the filter bag securely contained in the extraction vessel. Once the lid has been secured, a digital control panel is used to set the speed, agitation style and length of extraction which is usually 15 minutes. After extraction is complete, the bag is spun to remove excess solvent, just like the spin cycle of a washing machine. Figure 4 shows the loaded solvent draining from the extraction vessel through a filter press containing charcoal to remove impurities and improve color. The loaded solvent is collected and stored in freezing conditions at or under -20 degrees Celsius to congeal fats and waxes, a process referred to as winterization.

Hydrocarbon extraction is typically conducted in a closed-loop system, this is the only style of hydrocarbon extraction that is considered safe. Closed-loop means that the system is close, allowing no solvent to escape into the atmosphere and designed as a loop that recovers all solvent into a recycler where it can be reused. The solvent most commonly used is Butane gas, though some extractors use propane or other hydrocarbon blends. Figure 5 shows a detailed flow diagram of a Butane Extraction and Recovery System. 

First biomass is loaded into extraction vessel(s) that are sealed and pressurized under vacuum. Liquid butane is fed into the vessels, where it permeates the biomass picking up cannabinoids and other fatty substances. The Butane enters as a liquid and leaves as a gas, figure 6 shows the flow of the butane. The cannabinoid-butane solution flows into the collection vessel which is heated causing the liquid butane to return to a gaseous state. After the extraction is complete, the butane is recovered and returned to the storage tank. Once all Butane gas has been recovered, the system is depressurized and the extract is collected from the collection vessel, commonly referred to as a “honey pot”. The resulting extract is set under a fume hood or placed in a vacuum oven to allow the butane to evaporate out of the solution. The butane extract is then placed into a mason jar. Cannabinoids in the extract are bound to fats and lipids. These plant waxes are undesirable for use in cannabis products and must be removed. Traditionally, ethanol is introduced to the extract in order to free the cannabinoids from the fats and lipids they are bound to, the resulting solution is a loaded solvent. Next, the solution is frozen to congeal the fats and waxes to facilitate removal through filtration. This process is referred to as winterization. Sound familiar? That’s because winterization is essentially the same process used in the refinement of loaded solvent resulting from ethanol extraction. There are some alternatives to winterization, some operators use a centrifuge for separation. Other innovative operators are experimenting with the use of cryogenics. By bringing solvents to extremely low temperatures, it is possible to bypass winterization by increasing the selectivity of solvents so they only pick up cannabinoids, not fats and waxes. When working with solvents at cryogenic temperatures, great care must be taken to ensure operators protect themselves against exposure which can cause severe frostbite.

Post-processing refers to any processing that occurs after primary extraction and is intended to prepare cannabis oils for use in consumer products. The loaded solvent that results from the primary extraction processes mentioned above is winterized and frozen to congeal fats and waxes, which are undesirable for finished products. After winterization, the loaded solvent is filtered to remove fats and waxes. The filtration process is simple, shown in figure 7, the post winterized loaded solvent is filtered through a micron filter in a Buchner funnel, under vacuum. 

After the loaded solvent has been filtered, the solvent, ethanol, is removed using a rotary evaporator as shown in figure 8. The rotary-evaporator removes the ethanol in a controlled, closed loop system. The process of solvent removal through use of a rotary evaporator is shown in figure 9. First, loaded solvent is transferred into an evaporator flask that is secured to the rotary motor and lowered into a hot water bath. The flask spins within this hot water bath causing the ethanol to evaporate. The entire system is under vacuum so the ethanol vapor is pulled out of the flask and up onto the chilled condenser coil. When the ethanol vapor reaches this coil, it condenses and drips down into a collection flask where it can be reclaimed. At the end of this process you have processed cannabis oil in your evaporator flask and solvent in your solvent flask. This solvent is recycled and stored to be used in the process again. The resulting solvent-free cannabis oil is now referred to as crude.

Post-processing continues with the preparation of the crude oil for distillation. Prior to distillation the crude oil must be decarboxylated and devolatilized to remove any remaining solvents or compounds lighter than cannabinoids. Crude cannabis oil is devolatilized through use of a vacuum oven or further use of a rotary evaporator running at a low speed and low temperature for an extended period of time. It is important to ensure maximum surface area in order to facilitate efficient removal of volatile compounds. The less distance these compounds have to travel, the easier it is for them to “escape” the solution. The result is refined crude oil that is ready for distillation.

Distillation involves further refinement of crude cannabis oils. Through the use of a molecular still, crude oil is separated into two major fractions, distillate with high cannabinoid content that is very light in color, and residue, that is very dark in color, containing plant sugars, residual waxes and chlorophylls. Figure 10 shows a wipe film molecular still, the most common still used in crude cannabis oil distillation. First the system is brought under vacuum. Next, the refined crude oil is loaded into the feeder flask at the top, the oil drips down onto the still body which is heated. Since the entire system is under vacuum, boiling points of the compounds within the oil are lowered. When the oil makes contact with the heated distillation body, the compounds within it separate. Lighter, more volatile compounds like cannabinoids, are driven to the cold internal condenser and flow down the middle, this results in the distillate fraction. Heavier, less volatile compounds, like plant sugars, remain along the outside edges of the still body and flow down into the residue flask. Remaining solvents like ethanol and other light volatiles are caught in the flow of the vacuum and are carried to the cold trap where they are condensed. The resulting high-cannabinoid distillate is quarantined and sent to a certified lab for potency and contaminant testing. Once results show the oil is free of contaminants, and potency has been determined, the distillate is deemed ready for use in consumer products.


The last stage of post processing is terpene infusion. The terpenes collected through steam distillation in the first phase are reintegrated into the high cannabinoid distillate. This process involves heating the distilled cannabis oil in a beaker on a hot plate. A mixing pill is placed in the beaker and terpenes are added to the distillate, the resulting solution is blended until homogenized. Finally, the solution is filled into consumer products like vape cartridges, baked into edibles or blended with carriers for use in tinctures, pills or patches. These processes are referred to as primary packaging. After primary packaging, the products undergo secondary packaging where they are packed into their retail containers. Next, they are sent to distribution where they are securely stored until they are required to fulfill verified sales orders. Extensive quality control measures are utilized during every phase mentioned in this document to ensure consumer safety and product consistency.

This document is intended to aid regulators, business owners and individuals in understanding the operational processes involved in the processing of cannabis. If your organization has any further questions, comments or concerns, please feel free to reach out anytime. We aim to assist regulators in bridging any knowledge gaps in order to facilitate the creation of safe operational standards that protect and promote consumer safety.