A guide to the most common methods of extracting compounds from cannabis
Why so many different extraction methods?
The cannabis plant is incredibly complex and contains more than 120 different (so far identified) cannabinoids, terpenes and flavonoids. Using various extraction methods, you can "target" each of these compounds. The right method can vary depending on the desired derivative, the scale at which you are working and the desired quality of the final product.
For example, large producers often use solvent-based extraction methods that allow large-scale extraction. The most commonly used solvents are ethanol, CO2 or hydrocarbons. In contrast, smaller producers who want to produce high quality live resin in small batches should consider a professional press kit.
In the first part of the text, we discuss how to choose an extraction method. In the second part we discuss in detail the different extraction methods using solvents (ethanol, carbon dioxide, hydrocarbons such as butane, propane, hexene, etc.) and carrier oils. In the third part, we present the methods of extraction of cannabis without solvents (ice-water extraction - so-called mechanical separation; cold pressing; resin pressing and kif made using sieves).
1. How to choose a cannabis extraction method
So what is the best extraction method for your business? The answer is not so simple. In the cannabinoid production industry, you can never say unequivocally that one extraction method is better than another, because it all depends on what you are trying to produce, what the final product is.
So it is much better to ask yourself the following question: What are you trying to produce? Are you going to produce CBD isolate on a large scale? Or a full-spectrum oil for vaporizing a specific strain? Or a water hash without solvents? Choosing an extraction method can be challenging. Especially with regard to the cost of acquiring extraction equipment. So you can start by doing your market research and finding out what products are in demand and/or will soon be. Once you know which end products you want to produce first, your decision making will be much easier. Starting with the end product (i.e. deciding WHAT to produce) and working backwards will ensure that you are able to produce exactly what you intended.
And then there's the market. What happens when the market changes and you need to change your process and switch to a different product? Therein lies the real dilemma. Consumer demand, and therefore your desired end product, is bound to change over time. If you consider where the market may evolve before investing in equipment, you will save money when it does. Of course, this is easier said than done, but it pays to invest in resources that help you predict where the market may move. In our experience, however, it doesn't pay to buy a crystal ball. To help you decide which extraction method will work best for you to produce your chosen product, we'll explore the most commonly used solvent-based methods of cannabinoid extraction as well as solvent-free methods.
2. Solvent-based extraction methods for cannabis
The use of solvents to extract cannabinoid derivatives has been popular in the cannabis industry for many years. They are popular for good reason: they are easy to adjust their composition, they are effective and their use is relatively safe as long as you follow the guidelines and regulations.
The following extraction methods represent the primary (first) stage of cannabis processing (following cultivation, harvesting, drying, curing, etc.). After this first stage, most of the derivatives (e.g. crude oil) will proceed to further refinement stages. Others end up as final products ready for sale (e.g. full spectrum extracts or live resins).
Extraction with ethanol
Ethanol or ethyl alcohol is a colourless, volatile and flammable liquid. We are talking about the same intoxicating substance that is in all spirits, liquors, beer and wine, and is also used as an additive in motor fuels - alcohol. Ethanol has been used to extract botanicals for thousands of years and there is no reason to stop doing so today. This is one of the reasons why ethanol is still one of the most popular solvents for use in extracting rare cannabinoids such as CBD, CBG, CBN and THC from cannabis. And not only is ethanol relatively easy and safe to use.
The biggest advantage of ethanol is that it is incredibly versatile in what it can deliver. It's great for extracting a very diverse range of cannabis products. And when handled properly, it leaves no residual solvent in the final end product, which is why it is considered a "clean" solvent. Ethanol's ability to produce a wide range of cannabinoid derivatives makes it an ideal solvent for both small-scale cannabis processors (who can target a wide range of full-spectrum products) and larger processors seeking to isolate specific cannabinoids on a large scale.
In direct comparison to the other two most popular solvents used for cannabis extraction (CO2 and hydrocarbons), the ethanol extraction process is generally safer and easier: ethanol is less explosive and toxic and therefore considered safer to use than hydrocarbon extraction systems. The risk of explosion is much lower with ethanol than with extraction systems using CO2 , which must operate under high pressure. The purchase price of ethanol extraction equipment is much lower compared to CO2 extraction equipment.
Alcohol extraction also allows for a much higher throughput (how much biomass or plant material can be extracted in a given time period or batch) compared to carbon dioxide. Ethanol extraction is one of the easiest forms of cannabis extraction to learn, making operator training easier and faster. Its simplicity is mainly due to the fact that the ethanol extraction process does not require a change in the solvent phase, as is the case with other methods (using CO2 and hydrocarbons). Phase changes involve handling pressure in closed systems and require more thorough training to ensure a successful outcome. The solubility of ethanol, or the "similia similibus solvuntur" property (like dissolves like), makes it highly effective. Understanding the principle of solubility (the ability of a substance to dissolve in another substance) and the mechanisms underlying it is probably the most important thing to understand in the extraction of cannabinoids with ethanol.
At the molecular level, there are generally two different categories of molecules, polar and non-polar:
- Polar compounds mix or dissolve with other polar compounds.
- Non-polar compounds mix or dissolve with other non-polar compounds.
This is what we mean when we say "like dissolves into like".
The most common non-polar molecules we encounter are lipids and fats, such as cooking oils or motor oils. The most common polar molecule we encounter is water. Ethanol can be polar or non-polar. This makes it incredibly versatile and therefore ideal for extracting a wide range of cannabinoids and other compounds such as aromatic terpenes. Ethanol's ability to extract a wide range of compounds is great for full spectrum derivatives. Ethanol is uniquely well positioned to dissolve most of the slightly non-polar and slightly polar molecules that are abundant in cannabis!
How does ethanol extraction work?
Target compounds (the molecules we are trying to extract and separate from the others) usually include cannabinoids such as THC and CBD, as well as terpenes. All of these compounds are fat soluble. Ethanol dissolves fats quite well. Therefore, if you intend to produce edible, full-spectrum end products derived from cannabinoids, ethanol's ability to extract these compounds may be an advantage. The polarity of ethanol can be slightly modulated/adjusted by simply changing its temperature. This makes it a very flexible extraction tool.
The colder the ethanol, the higher its affinity (ability to combine with another substance or particle) for fat-soluble compounds, and therefore its extraction of cannabinoids and terpenes is more efficient. And if extraction is done with ethanol at room temperature or higher, it "extracts" from the plant not only cannabinoids but also a wider range of terpenes and other water-soluble compounds.
As flexible as ethanol is, it has its limitations. If your goal is to isolate only specific cannabinoids - for example, to make a CBD isolate - ethanol may not be the ideal solvent because it doesn't target individual compounds very well. Before deciding whether ethanol is right for you, you should be clear about the end product you want to obtain.
Ethanol extraction process
The ethanol extraction process begins by soaking the biomass in chilled ethanol or room temperature ethanol to extract terpenes and/or cannabinoids. The resulting solution is then evaporated to remove residual solvent by heat and vacuum to produce the crude extract. The crude concentrate can then be further distilled and refined. The result is a not so purified CBD, THC or CBG distillate. The ethanol extraction process typically proceeds as follows (for the purposes of this article we refer to the cold ethanol extraction process):
Cooling: pre-cooling the ethanol solvent to -40℃ to reduce the need for post-extraction steps.
Extraction: soaking and stirring the biomass in a cooled ethanol solvent to extract the cannabinoid compounds using a closed-loop mechanical centrifuge.
Particulate filtration: removal of suspended particles and adsorbents.
Solvent evaporation: Removal of ethanol from crude oil using a falling film evaporator (FFE).
Decarboxylation: heating the raw 'acidic' versions of cannabinoid molecules (such as THCA, CBDA and CBGA) releases the carboxyl group of the molecules and converts them into their active versions (such as THC, CBD and CBG).
Separation (distillation) of purified THC, CBD, CBG or other desirable molecules from crude oil by distillation.
Chromatography can be used for spectral analysis or to separate the distillate into isolated compounds.
Advantages of ethanol extraction
Ethanol is a great choice for high-volume output, making it an attractive option if you are producing cannabinoids in bulk for a large commercial operation. It is considered (by most) to be the safest and most efficient solvent for cannabis extraction. Given ethanol's versatility and ease of use, its position makes it uniquely advantageous for almost any type of botanical extraction. This is especially true for cannabis extraction because:
- Dissolves most non-polar and polar compounds.
- It has an affinity for cannabinoids when extracted at low temperatures.
- It is a non-viscous liquid at atmospheric pressure, which means it extracts quickly.
- It boils at relatively low temperatures, which allows efficient ethanol recapture and subsequent separation of the extracted compounds.
- Its relatively safe to use, easy to work with and easy to produce.
- Easy to store: ethanol storage regulations are usually more lenient, allowing your lab to store more solvent and extract larger volumes of cannabis at a time. When done properly in cool conditions, it eliminates the need for wax removal or winterization (a process used to crystallize and remove waxes in the filtering process to prevent the liquid fraction from forming cloudiness at lower temperatures).
- Great for creating full-spectrum cannabis extracts and tinctures.
For the production of which products is ethanol extraction ideal?
Ethanol extraction is ideal for the production of almost all cannabinoid derivatives. The first output of the initial stage of ethanol extraction is the crude oil, aka "crude" - the main building block of almost all cannabis derivatives. The other end products start as crude and are only subsequently refined and purified.
Finally, the crude oil is converted into oil for vaporization cartridges, gel capsules, edibles, tinctures, drops and topical preparations.
Ethanol is also an ideal solvent for large-scale production of isolates. After distilling the crude oil to further refine its potency, we can isolate compounds (such as CBD) to a very high level of purity (over 98%) using methods such as column chromatography.
CO extraction2 (carbon dioxide)
What is carbon dioxide extraction?
CO extraction2 is used to extract CBD and other cannabinoids from hemp by carbon dioxide under high pressure. This acts as a solvent at certain temperatures and pressures. It is used to extract concentrates using high pressure and extremely low temperatures, isolating and stabilising the extracted oil while maintaining its purity. Extraction with CO2 requires sophisticated equipment and considerably more training than ethanol extraction, but when done properly, the final product is very pure, potent and chlorophyll-free.
Is extraction via CO2 safe?
Extraction using carbon dioxide is generally considered a safe method because the solvent used (CO2 ) is not volatile. It is used to extract substances from plants in many industries for purposes such as decaffeination of coffee and the production of essential oils from a myriad of plants. The resulting derivative extract is pure because the solvent leaves no trace behind. CO2 also protects the fragile terpenes from cannabis by allowing cold separation. Setting up the process is very easy - the operator can choose their own pressure and temperature to achieve the desired results. Best of all, CO2 is environmentally friendly.
What is supercritical, subcritical and midcritical CO2 extraction?
When discussing CO2 extraction you will often hear the terms supercritical, intermediate critical and subcritical used. However, by far the most commonly used method of extracting cannabinoid derivatives using CO2 is the supercritical method because it is safe and provides a pure end product. In supercritical extraction, liquid CO2 is used and the temperature and pressure are raised to a level where the CO2 reaches the so-called supercritical point, i.e. it has the properties of both a gas and a liquid at the same time. This state is ideal for extracting cannabinoids because it dissolves THC and CBD like a liquid, but is easy to handle and completely fills the container like a gas.
Subcritical extraction means that CO2 is used at low temperatures and low pressure. Although subcritical extraction takes longer and provides lower yields than supercritical extraction, it preserves fine terpenes and other desirable compounds. This makes subcritical extraction ideal for producing final products that retain the 'full spectrum' of beneficial cannabis compounds. Conversely, if you would like to produce an isolate such as CBD isolate, you should not choose subcritical extraction because it requires many additional steps to isolate the desired molecules. Intermediate critical extraction refers to a general range of temperatures and pressures that lies between subcritical and supercritical extraction. It is not as commonly used as supercritical, but you can use it to combine supercritical and subcritical methods to produce full-spectrum cannabis extracts.
How does the CO2 extraction process work?
The extraction process using CO2 begins with the conversion of carbon dioxide from a gaseous to a liquid state. This is achieved by lowering the temperature while increasing the pressure. The next step involves raising the temperature using a heater and pressure above the point where the liquid becomes "supercritical", so that the CO2 now has the properties of a gas and a liquid simultaneously. At this point it is ready to be fed into the plant material for extraction purposes. CO2 passes through the plant material, dissolving the membranes of the trichomes and extracting terpenes and cannabinoids such as CBD and THC. After extraction, the resulting solution is passed through a separator to separate the desired compounds (cannabinoids, terpenes, etc.). The carbon dioxide is then condensed and converted back into a liquid ready for reuse.
What equipment is needed for CO2 extraction?
The extraction of CO2 is carried out using a "closed loop extractor". All CO2 extraction plants have essentially three chambers:
- The first chamber contains liquid CO2 under pressure;
- The second chamber contains hemp biomass;
- The third chamber separates the resulting extracted product.
The cooled CO2 is pumped from the first chamber to the second chamber. In the second chamber, supercritical conversion takes place. The supercritical CO2 then passes through the cannabis biomass and extracts cannabinoids and terpenes. The resulting solution is then pumped to the third chamber where the CO2 changes state back to a gas, leaving the precious cannabinoid extract at the bottom and the CO2 is ready for reuse.
Advantages of CO2 extraction
CO2 extraction has many advantages that are attractive to both consumers and producers. One of the biggest is that it is an environmentally friendly - or "green" - solvent. It leaves no unpleasant chemical residues, resulting in a cleaner and healthier end product.
It is safe: CO2 is food safe (used in soft drinks), non-flammable, inert and non-toxic. It is effective: You can fine tune its strength by adjusting the density of the liquid. Compared to other solvents, it leaves almost zero residue after extraction, resulting in a cleaner end product. The critical temperature of CO2 is close to room temperature, making it an ideal solvent for temperature sensitive materials.
For the production of which products is extraction using CO2 ideal?
Its ability to extract the "full spectrum" of cannabinoid derivatives makes CO2 ideal for the production of full-spectrum cannabis distillates and their accompanying fine terpenes, which give each cannabis strain its unique flavor and odor profiles. Carbon dioxide is especially prized for its ability to preserve the unique, fragile terpenes that cannabis connoisseurs appreciate.
Trained extractors can extract different cannabinoid derivatives by adjusting the pressure, temperature and solvent ratios. As a result, CO2-based products have become the main choice in the cannabis and hemp market for the production of all types of cannabis products, from edibles to isolates. CO2 technology is incredibly customizable and adaptable to changing market needs and is ideal for small start-ups and large companies alike.
Extraction with hydrocarbons (butane, hexene, etc.)
One of the main advantages for beginning extractors is that purchasing equipment for hydrocarbon extraction is usually less expensive than purchasing equipment for extraction using CO2 or ethanol. Hydrocarbon extraction can provide a potent end product suitable for dabbing, but it may not be the best method for producing other cannabinoid derivatives such as CBD isolates. Hydrocarbons such as propane and butane have been used to extract edibles for over fifty years. In the right hands, their ability to extract cannabis derivatives to a high degree of purity is exceptional - resulting in up to 90% concentration of plant cannabinoids.
How does hydrocarbon extraction work?
Hydrocarbon extraction usually uses butane as the primary solvent, although other hydrocarbons such as propane and hexane can sometimes be used depending on the desired end product. Butane has a low boiling point of -1 °C and is used as a liquefied gas in extraction. This low temperature preserves the integrity of temperature-sensitive terpenes and other fine derivatives. Propane is also commonly used for the extraction of cannabinoids. Its boiling point is even lower than that of butane, at -42 °C. A mixture of the two hydrocarbons is often used because propane can extract other compounds from the plant, such as fine terpenes, and residual hydrocarbons are less likely to remain in the resulting solution.
Hydrocarbons extraction process
The hydrocarbon extraction process typically begins with the release of cold liquid butane from a solvent tank into a column containing hemp biomass. This process dissolves terpenes and cannabinoids (THC, CBD and other minor cannabinoids) along with plant waxes and lipids. The cannabinoid concentrate is then ready for further refinement (depending on the desired end product): the dewaxing can be carried out using a dewaxing element, which is usually part of most closed-loop hydrocarbon extraction equipment.
Fine plant terpenes can be separated by centrifugation if necessary. Winterization with chilled ethanol then separates the lipids and waxes from the cannabinoid solution. Although this is a more thorough process than waxing, it can degrade the terpenes, so use with caution! The concentrated cannabinoid solution then ends up in a collection vessel where the butane (or other hydrocarbon solvent) should be degassed using heat and vacuum. The separated butane solvent is then collected for reuse in the next batch.
Advantages of hydrocarbon extraction
The use of hydrocarbons for cannabinoid extraction is becoming increasingly popular. Not only because of the lower cost of hydrocarbon extraction equipment, but also for several other reasons: purity and authenticity of the strain: If your goal is a high-end product for connoisseurs, using hydrocarbons helps preserve the authentic flavor profile of the strain. Time and performance. This is much faster than using supercritical CO₂, where the process can take 6 to 10 hours. Use of cuttings: Hydrocarbons allow extraction of cannabinoids from less desirable parts of the cannabis plant. Residues, such as the small leaves cut from the buds after harvesting, are an economical way to extract high-quality, cannabinoid-rich resins.
Versatility to produce a wide range of end products: depending on the variety of plant material and the production method, an experienced extractor can adjust the amount of butane and propane to produce a wide range of end products. Higher yields: Hydrocarbon extraction can yield between 14 and 30 % by weight, resulting in greater recovery of plant material.
For the production of which products is hydrocarbon extraction ideal?
Hydrocarbon extraction is ideal for the production of cannabinoid derivatives intended for dabbing, such as budder, BHO, crumble, honeycomb, shatter, resin and wax. However, hydrocarbon derivatives are not limited to dab-able products, but can also be used in ointments, edibles, vaping cartridges, tinctures, capsules and many other products.
Vegetable oils: coconut oil, olive oil and other edible oils
Edible oils: extra virgin olive oil, coconut oil, butter and other edible oils can be used to extract fat-soluble cannabinoids. The basic idea is to heat the decarboxylated cannabis flower directly in edible oil. While this extraction method is popular for small-scale home extractors, the resulting oil has much lower efficiency and lower shelf life than other extraction methods, so it is not recommended for large-scale commercial cannabinoid extraction. However, some producers consider it a more natural alternative to chemical extraction methods.
Vegetable oils are perishable and should be consumed quickly or stored in a cool, dark, temperature-controlled place. You can also use inert nitrogen to 'back fill' the storage container to increase shelf life. This is a common practice often used in the wine industry to reduce oxidation of wine.
Vegetable oil extraction process
Plant oil extraction, which is suitable for home extract makers, begins by heating the plant material to convert the cannabinoids into their more bioavailable versions, such as CBDA to CBD and THCA to THC. This process is called decarboxylation. It is usually recommended to use a temperature of approximately 140 °C for 30 minutes or 120 °C for 60 minutes for decarboxylation. However, this is only a rough guide as it will depend on your plant material and variety, as well as the quality of your furnace.
Once this step is complete, the plant material is added to vegetable oil (coconut and olive oil are popular) and heated to 100°C for 1-2 hours. This allows the decarboxylated cannabinoids, which love fats, to bind to the fat molecules in the oil, leading to the extraction of the cannabinoids. The plant material is then filtered out and only the leached edible oil remains. The resulting solution is a mixture of vegetable oil, terpenes, waxes and cannabinoids, etc. Unlike other forms of solvent-based extraction, the cannabinoid solution does not separate from the solvent. Edible oil infusions are distinctly 'unrefined' and are suitable for those who don't mind their CBD or THC oil tasting like cannabis.
This form of extraction is ideal for complete beginners and home makers who like to safely make their own extracts from cannabinoid derivatives without having to spend too much on equipment. However, the end product is not as potent as those obtained by more industrial extraction methods such as CO2 , ethanol or hydrocarbon extraction.
3. Solvent-free extraction methods for cannabis and hemp
An increasing number of consumers are now seeking cannabinoid derivatives that are produced using a solvent-free method. This is because they are perceived as safer to consume because they are obtained by a more 'natural' method. Whether this is true or not remains a subject of endless debate in the industry.
In fact, solvent-free separation is not technically an "extraction" at all, but actually a "mechanical separation". This means that the cannabinoid is not extracted from the plant material by a chemical process, but is separated from it by physical force.
Ice water extraction (mechanical separation)
Separation using ice water is ideal for the production of the so-called bubble hash. This method is a very popular method of producing a high quality product without the use of chemical solvents. It works by mechanically separating the cannabinoid-rich trichomes from the biomass by breaking them off using a combination of water and/or ice and physical agitation. This method is often referred to as 'water extraction', but in reality it is not technically 'extraction' in the true sense of the word. This is because the cannabinoids are not actually extracted from the biomass, but physically separated.
After the process, the trichomes remain in the water as suspended, undissolved solids. Once this mixture of water and trichome slurry is separated from the remaining biomass, it is filtered and separated. The recovered trichomes are then processed into hash "patties" and dried to produce a high quality end product. Cannabis derivatives created using ice water, such as bubble hash, are ideal for dabbing and are considered one of the highest quality forms of cannabis concentrates available.
Extraction by cold pressing
Cold-pressed hemp oil is exactly what you would expect from its name. Similar to cold-pressed olive oil (or any other plant extract), the plant material is cooled, crushed using high pressure to extract the hemp oil from the biomass. The cold pressing process involves applying pressure to the pre-cooled plant matter (flowers, leaves, seeds and stems) to extract a usable oil that can be used alone or in combination with other ingredients to create the desired end product.
Although cold pressing at lower temperatures preserves the desired terpenes, flavonoids and cannabinoids, the yield of this extraction method is relatively low. Cold-pressed cannabis oil is found in wellness products such as tinctures and external-use preparations.
Resin extraction by pressing
Resins and live resins are cannabis derivatives made by exposing cannabis plant material to heat and pressure to literally "squeeze" terpenes and cannabinoids from the flower's trichome glands. Behind the popularity of resins among cannabis connoisseurs is the feeling of purity when consuming a product that has never come into contact with any man-made chemicals. Resins are usually made from either trichome-rich flowers, dry kif, or low-quality hash. 'Live' resin is produced in the same way as these products, but from plant material that has been frozen immediately after harvesting to preserve the 'live' plant compounds.
Resin extraction by pressing is a similar technique to the cold pressing extraction method mentioned above, but adds the use of heat and pressure to extract hemp oil from biomass. Due to its relative safety, quick adoption and low cost, it is a popular method of small-scale extraction without the use of solvents.
While home enthusiasts may use a hair straightener, professional resin extractors use a small hydraulic press with a heat regulator to produce larger quantities. Whichever method you choose, the basics of how the press works are the same: A lightly crumbled curing mallet is placed between two pieces of parchment paper. If dry sifted kief or hash is used, it is better to also place the raw material in a sieve before placing it between the parchment. This will reduce the amount of plant particles in the finished product. Then simply place the parchment 'packet' in the press, heat it up and press it.
The oil is literally squeezed out of the biomass and drips through the parchment paper that is there to "catch" the precious crop. The quality of the biomass chosen and the temperature used play a large role in determining the yield and quality of the resin extract. Generally speaking, the temperature range for resin is 149-168℃. If you are trying to get a stiffer end product (e.g. shatter), you should use a temperature of 121-149℃.
Kif made using a sieve
Kif is one of the oldest known cannabis extracts. Its history goes back thousands of years. The sieves used for manual extraction have been found in archaeological excavations dating back to 3000 BC. And the kif extraction method is still very similar to the method used thousands of years ago. Kif is made from the cannabinoid-rich tiny sticky resinous glands at the end of the trichomes of the cannabis plant. The attraction for consumers is that kif provides high cannabinoid potency in a single coating.
As the most natural cannabis flower extract obtained without the use of solvents, its popularity is due to its purity, potency and versatility of consumption. Kif can be smoked, pressed into hash, added to butter, added to edibles such as biscuits, or made into moonrocks. After the plant material has been dried and curried, crushers and/or sieves are used to produce kif. The resulting product can then be pressed into hash if necessary using a press.
Summary
Most of the extraction methods mentioned above are usually only the first stage in the processing of cannabis. After this initial stage, the raw product, often in the form of crude oil, can proceed to further processing steps.
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