CBD Extraction Methods: How to Make CBD Oil?

Sylvester Spoon
February 19, 2018

CBD is the acronym that is seemingly on everybody’s lips (and in blog posts) these days. Yet, most of the members of the public are not familiar with the history behind its isolation from the cannabis plant, and the processes that go into obtaining the concentrated form that is available for purchase.

As is the case with many aspects in life and business, there is no single route to the desired effect, and there are numerous ways for extracting cannabidiol from the variants of cannabis, each method has its advantages and disadvantages.

In this article, we will consider the most widely used extraction techniques – from the user-friendly and home-oriented procedures inspired by Rick Simpson for his full spectrum cannabis oil to methods that are only suitable for industrial-scale facilities. We will approach the subject in a chronological fashion, by taking a look at how cannabidiol and cannabis concentrates were obtained in the industry’s infancy, and how that changed into the multifaceted methods of today. Firstly though, we should clarify the jargon.

Concentrates and Solvents

Plant concentrates have existed since ancient times, with the first such products being the result of purposeful dehydration. Compared to the raw vegetal material, concentrates have distinct advantages: a more pronounced effect, a better resistance to natural degradation, easier transportation, etc.

In the case of cannabis, the above statement is also true, with hashish being a rudimentary concentrate of cannabis. It seems that the term originated in writing around the 11th century AD, meaning that the practice of making hashish from a mixture of the female plant’s trichomes, leaves, and flower buds is without doubt much older than that.

With the advent of modern chemistry, obtaining plant concentrates became a more sophisticated process, yielding higher concentrations from lower quantities of raw material. Across the last couple of centuries, a large number of techniques have been used, yet only a handful have proved their worth from both a scientific and economic point of view.

The current popularity of cannabis concentrates has two main causes – a scientific one and an ethical one. Using a chemical extraction process is the only manner in which certain cannabinoids can be fully singled out in the end product because the average cannabis plant has more than one hundred such biochemical compounds. This is how one obtains THC oils and edibles (products containing predominantly tetrahydrocannabinol), CBD products or other cannabinoid concentrates, though the aforementioned largely overshadow the others. Obviously, the cannabinoid make-up of the plant providing the raw material for the concentrate is also of vital importance.

Secondly, one must also take into account the social stigma associated with cannabis consumption. While the idea that cannabis and cannabinoids may have substantial medical applications, how they are delivered into the system is still a subject of heated debate. As smoking and injecting are definitely frowned upon, ingestion of edibles and oils is much more socially acceptable, being deemed even harmless by more and more categories of the public.

Simply put, the concentrate is a (more or less) liquid solution extracted from the solid plant material. Broadly speaking, the extraction can be achieved with or without using solvents (substances that have the property of dissolving the initial solid, and then removed from the concoction, typically by through evaporation). Extraction techniques that involve solvents usually yield a product that is less dense (compared to the solventless methods), yet that can be addressed through further filtering if the oily texture was not the goal from the beginning.

Throughout the extraction process, the end-product is chiefly dependent on the quality of the plant material and the method of extraction. The same quality product may be obtained in any way, however, each method has its advantages and disadvantages.

As cannabis was not the first plant subjected to chemical extraction of concentrates, it is important to state that the process originates in other applications of agro-industrial chemistry. These techniques were first used on a small scale by scientists studying cannabis, cannabinoids and the endocannabinoid system in the sixties and seventies.

The Generic Cannabinoid Extraction Method

As social, economic, and medical attitudes toward cannabis slowly changed at the end of the 20th century, several companies moved towards devising a larger-scale production method for cannabinoid concentrates. One such company, a Canadian outfit by the name of Websar Innovations patented one of the most influential early extraction methods, in the 1990’s.[1]

The patent mentioned above describes a straightforward sequence in which either full spectrum cannabinoid oil can be obtained from the cannabis plant – in this situation industrial hemp was used due to obvious legal considerations – which can be further filtered and separated into specific cannabinoid concentrates, according to the preferences of the user.

Cannabinoid concentrates are best derived from the chaff od the cannabis plant, with the two following conceptions: still, green chaff to incorporate a quantity of chlorophyll and terpenes which supposedly enhance the effects of cannabinoids, or dried and ground chaff to limit the presence of compounds other than cannabinoids in the end-product.

The chaff remains, whether green or dried, are then transformed into an extract with the aid of a solvent. The solvents may be any of the following types of organic substances:

  • A weight alcohol – in the quasi-totality of cases ethanol is used due to its availability and the lower risks compared to methanol, for example.
  • A chlorinated hydrocarbon – compounds in this category include dichloromethane or chloroform. As one might imagine, this is a method that is not recommended as these chlorinated hydrocarbons are notoriously volatile and dangerous for direct human manipulation.
  • A petroleum hydrocarbon – a whole range of substances, including butane and toluene.
  • A supercritical fluid.
  • Subcritical
The resulting extract may be consumed as such – this is actually what vendors call full spectrum cannabis oil, wholly dependent on the cannabinoid, terpenes, and essential oils of the harvested plant – or selective cannabinoids can be further isolated from it. This individual purification is achieved through a technique ubiquitous in chemistry known as column chromatography[2]. Describing column chromatography is beyond the scope of this article. Nevertheless, we should add that it does not require sophisticated expertise or equipment (though there are automated devices available for purchase). According to the amount of extract, through column chromatography one can have a yield of concentrate from a few milligrams to a few kilograms, though the method has the downside of being extremely time-consuming if done manually.

At present, by applying the technique described above, one can obtain concentrates of the following cannabinoids: THC (tetrahydrocannabinol), CBD (cannabidiol), THCBC (tetrahydrocannabichromene), CBN (cannabinol), THCBG (tetrahydrocannabigerol), CBG (cannabigerol), THCBD (tetrahydrocannabidiol), CBC (cannabichromene), CBDV (cannabidivarol). Naturally, the hype is all about CBD, and different compositions of THC : CBD extracts.

Different concentrations, flavors, and consistencies can be obtained by experimenting with the various solvents, with different times in which the plant material is immersed in the solvent, different pressures when supercritical fluids play the part of the solvent, or with the volume of solvent used. Exceptionally concentrated products may result if the end-product is then suspended in another round of solvent and the steps are followed again.

From carefully reading this patent, one may conclude that the technology for producing cannabis concentrated is by no means a novel one, with the CBD boom taking place about 15 years later than the filing of this patent.

There are also additional techniques of purification, in case the quality of the ground chaff is subpar, or even if it is overly green. One of the best known is the so-called winterization of the resulting concentrate: any product obtained through any of the methods described above gets re-dissolved in an ethanol volume at least five times higher, which then is frozen below -40° F for at least a day. The impurities are then collected, the alcohol is evaporated, and the concentrate is thus significantly improved.

Before we proceed with the description of the methods utilizing each solvent (and the non-solvent techniques), some general considerations should be made.

While the yields vary widely when using different solvents (to which the quality of materials and skill of the person in charge should also be contemplated), one should expect no more than 10 percent of the initial plant mass to make its way into the final product, considering that one needs at least 10 times as much solvent than plant volume. Taking into account the fact that none of the proposed solvents could be regarded as cheap, we can safely conclude that extracting cannabinoid concentrate is an expensive affair. Especially if the desire is to produce on an industrial or commercial scale.

Then there is the matter of evaporating the solvent. Most of the substances which act as a solvent for cannabis, as you have seen, are highly flammable. Therefore the accumulation of their vapors is hazardous. One needs to be highly knowledgeable of the interactions between these compounds, so cannabinoid extraction does not turn into a dangerous matter.

Another aspect that cannot be stressed enough is that the quality of the concentrate depends enormously on the characteristics of the cannabis involved in the extraction.

CBD Solvent Extraction Methods

We should add that besides the solvents discussed in this section, there is also the possibility of obtaining small amounts of cannabinoid concentrate using olive oil as the agent. However, this method is time-consuming, very expensive, and limited to household amateurs, as there are virtually no products on the market obtained in this manner. This is why we did not bother bringing it up until now, and will not go into further detail.

Extracting with Petroleum-Based Solvents

There are two obvious problems when considering CBD extraction via petroleum-based solvents: the combustible nature of these compounds and the possible residues which are toxic when ingested by humans. Nevertheless, it works with both small and large quantities of cannabis, and when done in an appropriate setting, almost all of the solvent is vaporized.

There are instances where “connoisseurs” apply this method for homemade CBD, but especially for high-THC cannabis oils, but a professional extraction kit costs more than $30000. This assortment of equipment can transform upwards to 3 kilograms of dried cannabis material into concentrate in approximately three hours.

Butane is the most widely-used petroleum-based solvent in extracting CBD and other cannabinoids, and the sequence of steps is fairly simple, at least theoretically: the ground plant is placed tightly in a tube that is fixed at one end with a screen that lets liquids out but not solids. Butane, via a torch, is inserted into the tube with the cannabis extract, alongside the residual butane seeping through the screen. This mixture is collected into a waiting container, and then the butane must be purged either by heating in a very hot liquid or introduced into a vacuum oven (when done in industrial settings). The resulting oil can then be further filtered through the technique of column chromatography to transform it into a single cannabinoid concentrate.

Besides butane, many other hydrocarbons are known to be successfully used, although most cases involve propane or a propane-butane amalgamation, following the same sequence as described before.

Extracting with Ethyl Alcohol

Though this technique should not, at first glance, cause much disturbance in the community, it is the most debated and has strong advocates both for and against. The “for” side underlines its suitability to obtaining both small and large quantities of isolate (which makes it perfect for both informal and industrial settings), while the “against” party decries it is more of an art than a science – it takes far too long when aiming for large batches of product, and it is very easy to for ethanol traces to not be wholly purged from the concentrate, as exact timing and control of temperature is required when using alcohol as a solvent.

Describing the process would be redundant, as it is very similar to the butane technique, although it does not need the same towering temperatures of water to evaporate the ethanol. Another point of disagreement when it comes to alcohol extraction is the amount of time the ground cannabis should soak in the ethanol.

Large companies have the possibility of purchasing ready-made kits for alcohol extraction, although the prices for such “cannabis distilling machines” does not make it cost-efficient, with the large majority of manufacturers turning towards the CO2 extraction method.

This does not mean that alcohol extraction does not have its share of fans, especially considering the aftermath of the Rick Simpson “phenomenon.” Nevertheless, using this method at home usually means obtaining a full spectrum cannabis oil rather than a CBD oil, as further filtering is not very effective for the everyman.

Supercritical Carbon Dioxide Extraction

As is the case with the other solvent-based techniques, supercritical CO2 works in much the same way, with the added consideration that one needs special equipment in order to transform carbon dioxide from its natural gaseous state to be able to “act as a solvent.” Almost all specialists agree that this is the “greenest,” least dangerous, and the dependable manner in which cannabidiol concentrate can be achieved.

Using a condenser and a compressor, gaseous CO2 becomes liquid carbon dioxide at a temperature of -68.8° C and a pressure of 73 atmospheres. From this liquid state, with added pressure and a sudden increase in temperature, the fluid transforms into a state called supercritical – not a fluid, but not quite a solid. We will not get into the technicalities here; the main point is that supercritical CO2 has the density of a fluid, all the while having gaseous properties when introduced into a separate container. This basically means that it acts like a solvent (the fluid), but it does not require external manipulation (in the pressure and the temperature) in order to evaporate, as was the case with the other solvent-based techniques.

Temperature changes still occur in the CBD extraction process, because the degree of solubility in the fluid carbon dioxide varies with temperature. This means that this method can yield, almost on cue, either full spectrum oils or a single cannabinoid concentrate, without further filtering. Furthermore, the extraction process does not produce any (detectable) residue, as carbon dioxide is a component of the Earth’s atmosphere.

The advantages of this method are self-evident, though there is a drawback, which is redundant if you are a large-scale outfit. Naturally, we are talking about costs, as the majority of sources list a price in excess of $100,000 for a machine capable of extracting concentrates from a 3 kilogram batch of cannabis in a 16-hour round. Furthermore, some outliers argue that given the high pressures involved, some properties of the cannabis plant may be compromised from the start, although no definitive evidence was ever brought forward to sustain this viewpoint.

Isolates and Non-Solvent Techniques

An apt metaphor for those who prefer non-solvent techniques could be that they are the master miniaturizers of Antiquity and the Middle Ages, while those who prefer solvent-based solutions are the industrial Leviathans of the present day. This means minimal yields and works for artisans, not suitable for general consumption. We dedicate to them only a tiny place in this article in order to point out that there is an alternative for the passionate individuals out there.

CBD Isolates refers to the extra-concentrated CBD crystals that some vendors have in their offer,  boasting a purity of around 99 percent. Obtaining those crystals is an arduous, repetitive and potentially dangerous process of taking an already formed batch of full spectrum cannabinoid oil, adding pentane while heating and cooling it a few times, then placing the result in special-made crystals with the aid of a vacuum pump, then actually “cooking” them at high temperatures.

Dry Sifting is actually an exercise in ultra-filtering the ground cannabis trichomes with the aid of several silk screens that have openings of just several microns. The result is a very fine powder that is not more CBD-rich than the plant that was involved in its production. It is simply a manual way of achieving purer cannabis that is somewhat more concentrated.

Rosin Tech is one of a number of techniques that use industrial presses and a heat generator to extract the oil from flower buds (rarely) or, more often, an already produced batch of hashish. Again, this technique does not isolate or filter the cannabidiol.

Life would be mirthless if getting from point A to point B would entail a single route. The same is the case for obtaining CBD oils and edibles, and the whole range of adjacent cannabinoid concentrates. The methods presented here by no means constitute an exhaustive list. They may be thought of a simple starting point into putting one’s imagination to work, whether in an industrial capacity or strictly a personal one. Because for absolute pragmatists, there is no denying that cannabidiol attained through the supercritical carbon dioxide technique is the best solution for the near-future at least.