Glossary of co2 extraction process

The following glossary of terms is definitions used throughout the CO2 for botanical extraction industry.

INDEX

A | B | C | D | E | F | G | H | I | J | K | L | M

N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

Alcohol extraction

Ethanol alcohol can be used to make cannabis tinctures and other concentrates such as Full Extract Cannabis Oil (FECO). Isopropyl alcohol can be used to make hash, but many are shy away from it because of concerns of its toxicity. Denatured alcohol is toxic and should not be drunk or used to make cannabis concentrates at all.

“When a product was made with alcohol extraction, it’s a good idea to ask what type of alcohol was used.”

What is alcohol extraction?

Ethanol alcohol can be used to make cannabis concentrates. It’s important to note there are different types of alcohol, all with their own uses:

Ethanol, also called drinking alcohol because it’s the only alcohol that’s safe to drink, is the active agent in alcoholic drinks, such as beer, wine, and spirits. It is safe to use for making cannabis concentrates.
Isopropyl alcohol has been used by some hashmakers but it can be toxic at certain levels, and many in the cannabis community shy away from it.
Denatured alcohol is poisonous if consumed and should only be used for cleaning tools or surfaces. It should not be used for making cannabis concentrates.

How to make an alcohol extraction

When using ethanol alcohol to make extracts, many extractors use something close to 100% pure ethanol. Most spirits, such as rum, vodka, gin, tequila, whiskey, etc., have around 40% alcohol by volume (ABV), or are about 80 proof. If making a cannabis extract, 190 proof or stronger (95-100% ethanol) is ideal.

There are various ways alcohol can be used to extract cannabinoids, and the simplest method is to make an alcohol-based tincture, where cannabis is soaked in alcohol at room temperature for weeks. Alcohol tinctures are common in herbalism with non-cannabis herbs and usually have around 40% ABV. Since only a few drops are consumed at a time, it is not enough for one to feel drunk.

Alcohol is considered a polar solvent, which makes it wonderful for extracting cannabinoids, alkaloids, and other chemicals from cannabis and other herbs, although it also extracts chlorophyll, usually giving alcohol extracts a deep green color. Alcohol tinctures are usually consumed under the tongue but can also be added to drinks or food and consumed like an edible, or even rubbed into the skin like a topical.

Ethanol, and all other types of alcohol, are highly flammable as liquids and vapors, so alcohol extraction should be done in a well-ventilated area.

An alcohol extraction can also be heated or left out to let the alcohol evaporate. The result will be a dark, tar-like substance rich in cannabinoids with no residual alcohol—this is often called Full Extract Cannabis Oil (FECO).

Analyte

Chemical compounds that are being analyzed, measured, or quantified. This would include cannabinoids and terpenes which are typically reported in the Certificate of Analysis of any cannabinoid products.

B

BHO (Butane hash oil)

Butane is burned off of raw, unprocessed Purple Dream hash oil (Daniel Brenner for Leafly)
Butane hash oil, or BHO for short, is a specific type of cannabis concentrate made using the chemical solvent butane. BHO extracts can be either hard and glass-like, soft and waxy, or a sticky, stretchy in-between. Because BHO can vary so widely in appearance and texture, they may go by other names such as “honeycomb,” “crumble,” “icing,” and other descriptive monikers. BHO is most commonly consumed via dabbing.

What is butane hash oil (BHO)?

BHO, or butane hash oil, is a cannabis concentrate produced using butane solvent extraction. The butane separates cannabis compounds from the plant, resulting in a concentrated oil containing THC, CBD, and other chemical constituents, and leaving undesirable plant material behind. The resulting hash oil can range in potency, but may reach heights of 80-90% THC.

Butane hash oil can vary widely in color and appearance. Typically, it ranges between a light gold to a dark amber color. Some BHO is hard and translucent, called “shatter,” but it may also be soft and wax-like, hence the term “wax.” BHO can also fall somewhere in between, in a sticky, stretchy form sometimes called “pull-n-snap.”

Most consumers buying BHO intend to enjoy it by dabbing, a consumption method that involves flash vaporization using a specialized water pipe. However, BHO may also be added to bowls of cannabis flower or used to enhance the potency of joints and blunts.

How is butane hash oil (BHO) made?

BHO cannabis extracts are made using butane, a chemical solvent. Professional extractors use what is called a “closed-loop system” that allows the butane to travel through cannabis plant material in contained chambers, preventing the flammable solvent from entering the air. The butane separates marijuana’s essential compounds like THC and CBD and forms a potent oil that may be further refined.

Producing BHO at home is incredibly dangerous and not recommended because butane is highly flammable and can cause explosions.

Is butane hash oil safe?

Because BHO is made using chemical solvents, some question whether it is safe to consume. Regulated cannabis markets require all cannabis concentrates to be tested for traces of butane to ensure that every product on legal shelves has been adequately refined for purity and does not exceed the legal limit of residual solvent levels.

The most serious risk associated with BHO is not related to consumption, but rather, production; clandestine home setups that lack proper ventilation and closed-loop systems have been the cause of several explosions, some of which have been lethal.

Another danger associated with BHO is the use of butane torches used to heat dab rig nails. These torches should be used with caution, or alternatively, you may consider investing in torch-free dabbing setups like e-nails (electric nails).

BHO is a potent concentrate that should be approached with caution by cannabis novices. When dabbed, BHO can bring on intense effects that can lead to dizziness, anxiety, or other psychological distress. It’s a good idea to only dab when seated and to have a comforting environment to retire to in case the high becomes psychologically challenging.

Biomass

Organic material is derived from plants or animals, in this case, any plant matter from hemp or cannabis.

Butane

Butane is a highly volatile, colorless hydrocarbon gas with an odor similar to petroleum. Like propane, pentane, hexane, and other hydrocarbons, it is used to extract cannabinoids, terpenes, and other compounds from the cannabis plant to make concentrates, collectively called BHO, or butane hash oil, which can vary in consistencies and textures. Butane is one of the most ubiquitous hydrocarbons in the world. It is highly flammable and needs to be handled by licensed, trained professionals.

What is butane?

Butane is a colorless hydrocarbon gas with an odor similar to petroleum. Like propane, butane is primarily obtained from liquid natural gas but can also be a byproduct of industrial refining processes. Butane is commonly used as an aerosol propellant, a fuel in lighters or blowtorches, and to make other chemicals.

Butane is normally stored and shipped under pressure as a liquified gas, which is so cold it can cause frostbite. It is highly flammable and easily vaporizes at room temperature. Since butane vapor is heavier than air, there is a major risk of ignition from any flame or spark nearby. Butane is highly volatile and can explode even if storage containers are exposed to intense heat or flames. As butane is colorless, unlike smoke or other vapors that are visible, there is no way to see how much butane is in the air, which makes the risk of explosion even higher.

Butane, like pentane, propane, hexane, and other hydrocarbons, is commonly used in the cannabis industry to make extractions, which strip cannabinoids, terpenes, and other compounds from the cannabis plant in BHO, or butane hash oil. BHO can have a wide range of consistencies, ranging from crumble on the dry end, to shatter, budder, and oil on the wet end.

BHO vs CO2

BHO is an inexpensive extraction method compared to CO2 extraction or short path distillation, making it popular in the illicit cannabis market and resulting in explosions and injuries due to improper handling. It is imperative that butane extraction is always conducted by licensed, trained professionals.
BHO must be obtained through the legal, regulated cannabis market, which ensures it has been tested and is safe for consumption. Inhalation of butane can lead to cardiac damage and organ failure, among other serious harms, but this usually results from BHO obtained illegally through the unregulated market.

C

Cannabinoid

A class of compounds found typically in the resinous trichome heads of the cannabis plant. There are over 140 identified cannabinoid compounds in cannabis with the most prevalent being THC, CBD, and CBG. Cannabinoid compounds can also be found in other plant species (phytocannabinoids) and within the body (endocannabinoids).

Cannabidiol (CBD)

A non-psychoactive phytocannabinoid found in cannabis and hemp. Cannabidiol is the “active” form of CBD.

CBDa

Cannabidiolic Acid, also known as CBDa, is the “inactive” precursor to cannabidiol, and is the major cannabinoid found in hemp. CBDa must first be “activated” through decarboxylation and converted to CBD.

Channeling

The uneven flow of solvent through the botanical matrix inside an extraction column. The solvent will take the path of least resistance and if there are issues with the material, grind size, or system design this can lead to the solvent creating tunnels through the biomass causing uneven extraction.

CO2

The chemical formula for carbon dioxide. CO2 can be used as a solvent to extract cannabinoids and terpenes from the cannabis plant into a concentrate, commonly known as CO2 oil. Also, in indoor cannabis growing, CO2 can be added to the environment in small amounts to aid photosynthesis, helping marijuana plants grow quicker and stronger.

CO2 oil

A cannabis concentrate made through CO2 extraction, which uses CO2 as a solvent to strip the cannabis plant of cannabinoids and terpenes into a concentrate. CO2 oil can be high in THC, CBD, or another cannabinoid or specific terpene, and be of varying consistencies—the “CO2” in its name merely defines the process used to make it.

What is CO2 oil?

CO2 oil is a term used to describe any cannabis concentrate created by CO2 extraction. CO2 extraction relies on a closed-loop system and the chemical is purged from the final product.

CO2 oils can be of varying consistencies, such as shatter, crumble, honey, oil, etc. They can also be high in THC, CBD, or another cannabinoids or specific terpene.

How to use CO2 oil

CO2 oil is vaporized. It can come in vape cartridges and consumed through a vape pen, or as a concentrate, or dab, in the form of a shatter or wax. If in one of these forms, CO2 oil needs to be flash vaporized and consumed through a dab rig.

Compound

Multiple chemical elements are held together by chemical bonds. Carbon, oxygen, and hydrogen are chemical elements that comprise the compound tetrahydrocannabinol.

Condensation

The process of changing a vapor or gas into a liquid. The liquid in this case is called condensate. The term thin film is also applied to a condenser because as condensable vapor gas encounters a cold condenser, a thin condensate film will form automatically. Careful engineering of the condensation path is a crucial aspect of the overall distillation process. The thin condensate film is typically removed by gravity.

Condensers are typically situated in two positions relative to the evaporator. The first position is in close proximity to the evaporator. This is called a short path. In the second position, the condenser equipment is located remote from the evaporator.

Constant Extraction Rate (CER)

The first stage of the extraction curve is where the solute (cannabinoids, terpenes, waxes, etc.) on the surface of particles are easily available to interact with the solvent for extraction. Usually, this is very linear and is controlled by the solubility of the solute in the solvent.

Cosolvent (Modifier)

Organic solvents that are used in small quantities in many SFE procedures have become apparent as the technique has matured. These cosolvents are generally used to increase the solubility of the analyte or possibly to increase the separation of co-extractives. Cosolvents such as ethanol have been used to increase the solubility of phospholipids in supercritical carbon dioxide (SCCO2). Performing SFE with cosolvents usually results in a higher weight percent of fat over that recorded with pure CO2.

Critical Temperature

The critical temperature (Tc) is the maximum temperature at the critical point at which a gas can be converted into a liquid by an increase in pressure.

Critical Pressure

The critical pressure (Pc) is the minimum pressure that would suffice to liquefy a substance at its critical temperature. Above the critical pressure, increasing the temperature will not cause fluid to vaporize to give a two-phase system.

Critical Point

The characteristic temperature (Tc) and pressure (Pc) above which a gas cannot be liquefied: A point on a phase diagram where the gas and liquid phase density is the same.

At this point, the substance will inherit the good quality of both gas and liquid phases. It is defined by the critical temperature and critical pressure.

Crude

Unrefined oil from any oil extraction process, requiring further post-processing for product formulations.

Crystallization

A process whereby chemical elements under certain conditions arrange themselves in a fixed pattern to make a solid. Crystallization is often used to make highly purified oils by dissolving a cannabinoid distillate in a warm solvent and slowly cooling it to make crystals.

D

Decarboxylation

The removal of a carboxyl group from either CBDa or THCa to create the active forms of the compounds, CBD and THC. This process is driven through thermal conversion.

Density

Mass of a substance per specific volume. For supercritical CO₂ the density of the solvent tells us how tightly packed the CO₂ molecules are in a chamber. In general the higher the solvent density, the greater the solvating power of the CO₂.

Diffusion

The movement of solvent into the packed biomass to interact with cannabinoids.

Diffusion Controlled (DC)

This is the final stage in the extraction curve, where extraction rate depends on solvent movement through the matrix to solute. Usually, this occurs toward the end of extractions but improper system designs, large vessel size, high flow rate, and channeling lead to this stage occurring earlier, resulting in longer run times or poor extractions.

Distillation

Refers to the thermal process of evaporation of a volatile from a fluid and condensation of that volatile to produce a separation between the components that are not evaporated and the components that are condensed.

The evaporation of a liquid will produce gas. That gas then travels (called diffusion) to a condenser where it cools and condenses back to a liquid. This is typically accomplished under the power of a vacuum pump.

Distillation systems and distillation equipment

Typically incorporates both an evaporator and a condenser so as to provide a separation between the evaporated fluid and condensate.

E

Extraction Curve

A non-linear curve that demonstrates the rate of extract recovery, and comprises three stages: diffusion controlled, constant extraction rate, and falling extraction rate. Useful for determining method efficiency, solvent flow, and run-time variables.

Extraction Efficiency

The percentage of target analyte that moves from the biomass and into the solvent stream during the extraction period.

Evaporator

A piece of equipment designed to remove selected volatile components from a fluid. Selectively removing solvents from fluids is accomplished by controlling the temperature and pressure of the fluid.

Evaporation

Evaporation refers to the thermal process of a liquid changing to a gas under pressure or thermal influence. This change is also known as a “phase change”. This happens when water boils and makes water vapor. In the case of cannabis processing, evaporation refers to two different processes. First, a phase change of cannabinoids like CBD from the liquid state evaporates to a gas at a high temperature and vacuum. This change happens at the evaporator surface. Second, evaporation refers to the phase change of a solvent such as ethanol as it is being removed from the oil. An evaporator typically has an external condenser.

Evaporator equipment is typically designed to produce a thin film on a heated surface so that solvents will volatilize quickly and efficiently.

F

Falling Extraction Rate (FER)

The middle stage of the extraction curve. During this phase of the extraction process all of the readily available analyte from the CER stage is exhausted and the extraction is transitioning towards the DC stage.

Falling Film

The falling film refers to a film that spreads over an evaporative surface by gravity. The fluid, in this case, must have low viscosity at the evaporator temperature so that it can flow and evaporate.

Fractional Distillation

Fractional Distillation refers to the ability to start distilling at a low temperature and ramp up the temperature to sequentially boil the components. The components are also sequentially condensed thus allowing separate fractions to be collected.

Fractionation (Retrograde Fractionation, Inline Fractionation)

The process of conducting molecular weight separations, typically higher and lower weight molecules from the cannabinoid content, during a CO₂ extraction run utilizing three in-line collection vessels. Each vessel will have a lower density than the previous one allowing for collections of distinct compound fractions from a single extraction method.

H

Heat Exchanger

A system that exchanges heat between two different liquids or gases. In supercritical CO₂ extraction systems, heat exchangers are used to help control solvent temperatures.

Heat Transfer

The transfer of thermal energy, or heat, between two separate systems. An example would be the thermal exchange between a vessel heating band and the stainless steel vessel itself.

M

Mass Flow

The mass of a compound, fluid or supercritical fluid passing through a meter in a specific time period. Mass flow in regards to CO₂ extraction is the amount of solvent passing through a flow meter per time period. This is usually reported in grams per minute.

Molecular Distillation

Molecular distillation is distillation under high vacuum pressure that reduces the probability or frequency of one evaporated molecule encountering another. Under a high vacuum, evaporation of cannabinoids from oil purportedly migrates unimpeded from the evaporator to the condenser. However, the conditions for true molecular distillation do not occur in the case of cannabis or hemp oils as there are always other compounds that co-distill with the cannabinoids.

Molecular Weight

The total mass of a specific compound. In supercritical CO₂ extractions, the molecular weight of a compound will play a huge role in determining its solubility in the solvent. For example, terpenoid compounds have a much lower molecular weight compared to cannabinoids and will have greater solubility in supercritical CO₂ due to their lower molecular weight.

Monoterpene

Light, volatile, C10-based terpenes are composed of two isoprene units. The fragrant aroma of many botanicals is created by these compounds.

N

N-alkane waxes

Compounds with nine or more carbon atoms that are solids under normal conditions. These waxes are usually found on plant leaves as a barrier to the external environment. They can be used as a qualitative marker for wax presence in extracts by utilizing an acetone test.

P

Potency

In pharmacology, potency is defined as the measure of a drug’s activity. In the cannabis industry, this term is colloquially used as a replacement for analytical purity, or the percentage of cannabinoids present in the biomass or extract.

Pressure

Force exerted by the solvent on the inside of a pressure vessel. This data is usually reported in psi, bar, or MPa and along with temperature is the other force that affects solvent density.

Pressure Regulator

A valve that controls the pressure of a fluid or supercritical fluid and holds the pressure at a specified value.

R

Reduced Pressure

The reduced pressure (Pr) is the ratio of the pressure in the system (P) to the critical pressure (Pc).

Pr = P/Pc

Reduced Temperature

The reduced temperature (Tr) is the ratio of the temperature (T ) in the system to the critical temperature (Tc).
Tr = T/Tc

Residence Time

The total time a fluid, supercritical fluid, or even a solute spends inside a vessel or chamber. For cannabis and hemp extractions it would be the total time the solvent spends in either the extraction chamber or fractionation vessels.

Rotary Evaporators (Rotovaps)

Maybe the most common way to accomplish solvent removal in the hemp and cannabis industries. A form of short path distillation equipment using a spinning round bottom flask, a vacuum pump, a heating bath, and a chilled condenser, to evaporate and collect volatile fluids into a receiving flask.

Run

Complete extraction cycle, from the loading of biomass into the extraction vessel, to the collection of extracted oil.

Run Time

The total active extraction time of a run.

S

Sesquiterpene

Similar compounds to monoterpenes but C15 is based on three isoprene units instead of two. These compounds have heavier molecular weights than the monoterpenes and require a higher CO₂ solvent density to fully extract. As with the monoterpenes, the sesquiterpenes are responsible for the aroma.

Short-Path

Short-Path refers to the distance that the evaporated liquid-vapor travels from the evaporation surface to reach the condenser. In practice, a “short path” describes the location of the condenser in relation to the evaporator. The short path has an internal condenser whereas an evaporator has an external condenser.

Solubility

The solvent conditions determine the quantity of solute (cannabinoids) that is able to be dissolved in a solvent (CO₂). This is one of the key metrics to be maximized when conducting any botanical extraction.

Solvent

Liquids or supercritical fluids are able to dissolve certain solutes. In the case of cannabis, the solvent is supercritical carbon dioxide and the solutes are the cannabinoids or terpenes. The cannabinoid potency of the biomass will determine how much solvent is required to complete an efficient extraction. As the potency increases so will the need for additional CO₂.

Subcritical CO₂

The state of CO₂ where it becomes a liquid. Found at higher pressures and temperatures past the triple point. Liquid CO₂ usually has a higher density than supercritical CO₂ but less solvating power for cannabinoids.

Supercritical CO₂

The state of CO₂ where it acquires the properties of both a liquid and a gas with excellent solvating power for all non-polar compounds. Found at higher temperatures and pressures past the critical point.

Supercritical Fluid

The defined state of a compound, mixture, or element above its critical pressure (Pc) and critical temperature (Tc). It is a gas-like, compressible fluid that takes a shape of its container and fills it. It is not a liquid but has liquid-like densities (0.1–1 g=mL) and solvating power.

Supercritical Fluid Extraction

Extraction of a material using a supercritical fluid. The extracted material is usually recovered by reducing the pressure or increasing the temperature of the extraction fluid and allowing the volatile components of the mobile phase to evaporate. Instrumentally, supercritical fluid extraction can use many of the components of a supercritical fluid chromatographic system. It can be used either as an online sample introduction method for a chromatographic separation or as an offline sample preparation method.

Supercritical Fluid Chromatography – Coupled Supercritical Fluid Extraction

In this system, a sample is extracted with a supercritical fluid, which is then placed the extracted material in the inlet port of a supercritical fluid chromatographic system. The extract is then chromatographed directly using a supercritical fluid.

Still

Still refers to an apparatus where distillation (evaporation and condensation) are taking place independent of whether the still is a short path, falling film, molecular, or wiped film.

T

Temperature

Quantitation of the thermal conditions inside an environment or system. Usually reported in °C, °F, or K. Along with pressure, is a force that determines the solvent density.

Terpene

Class of naturally occurring unsaturated hydrocarbon compounds found in cannabis and many other botanicals. This class of compounds includes monoterpenes (C10), sesquiterpenes (C15), and diterpenes (C20) as well as other terpenoid compounds.

Tetrahydrocannabinol (THC)

The decarboxylated form of THCa and the primary psychoactive cannabinoid used for both recreational and medicinal purposes.

Tetrahydrocannabinolic acid (THCa)

The precursor compound to the primary psychoactive phytocannabinoid is found in cannabis and hemp. The acid version is not biologically active and must be decarboxylated to unlock its psychoactive effects. In unrefined cannabis biomass, most of the THC will be found in this carboxylated form.

Thin Film

The process of coating the solution to be evaporated into a thin film on a heated surface. Wiped film apparatus used in hemp and cannabis distillation are not usually fixed distance but typically use “comb” shaped wipers to mix the oil on the surface of the oil while simultaneously creating a thin film at the surface. A thin film is important so efficient evaporation can occur.

Thin Film also applies to a condenser because as condensable vapor gas encounters a cold condenser, a thin condensate film will form automatically and is typically removed by gravity.

Throughput

The output of a system is based on the amount of material that can be processed in a given time period.

Trichome

The resin heads are found on cannabis and hemp flowers at proper maturity. The trichomes house the majority of the cannabinoids produced by the plant.

Trim

Slang for non-flower biomass. This is usually the “waste” material that is not of the quality for sales, used in joints, or unsuited for niche extraction products. Trim material is usually used to create “full spectrum” cannabis and hemp crudes or high purity distillates.

Triple Point

In carbon dioxide, the triple point occurs at -56.6°C and 75 psi. Small changes in either pressure or temperature in this range can change carbon dioxide to (1) a gas, (2) a liquid, or (3) a solid.

V

Vacuum Distillation

A distillation that takes place under ultra low-pressure conditions. This allows the compounds to phase change from a liquid to a gas with much less heat required. In cannabis, this is used to separate cannabinoids from other undesirable compounds.

Vapor Pressure

The addition of heat to a closed extraction system will increase the volatility of compounds like cannabinoids. These compounds as they excite and are volatile will increase the vapor pressure in the system. The increase in vapor pressure can be utilized to increase cannabinoid solubility.

Volumetric Flow

The volume of fluid or supercritical fluid passing through a meter in a specific time period. In supercritical CO₂ this would be the measurement of the volume of solvent versus the mass (mass flow).

W

Winterization

Utilization of a cold solvent to solidify the plant waxes, cause them to crystalize, and thus drop out of the solution. The process is considered fractionation based on melting point.

Wiped Film

The wiped film refers to the existence of a wiper to wipe a fluid over a hot evaporation surface. Wiped film evaporation refers to evaporation from the hot surface as the wiper creates a thin film on the evaporation surface.