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Choosing Your Ideal Cannabis Extraction System

By Alexander Beadle

Published: Mar 28, 2019   
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The history of cannabis extraction dates back centuries. There are references to hashish in Arabian writing dating back as far as 900 AD, including in one story in the famous 10th century manuscript One Thousand and One Nights. In the 12th century, the Jewish philosopher Maimonides even included a cannabis oil substance in his Materia Medica, a lexicon of known pharmaceutical products at the time. 

And the technology used in the production of cannabis extracts, such as these resins and oils, has only become more advanced over the centuries. Hashish, which used to be produced by hand rubbing or sieve rubbing, is now made using industrial-sized machines that are capable of performing processes that could not be done in previous centuries, such freezing/refrigeration and high-pressure compression

As science progressed, new cannabis extraction techniques were developed. For example, the production of hydrocarbons from the petroleum industry gave rise to solvent-based cannabis extraction techniques which could produce much greater volumes of extract than previously possible.

Butane hash oil (BHO) was the first modern cannabis concentrate produced. Butane had already been adopted in the food industry as a way of producing canola and corn oil, and so was quickly adopted as a solvent for cannabis extraction. In basic BHO preparations, the cannabis plant matter is steeped in a butane solution which draws the desirable cannabis oils out from the plant matrix. The resultant oil/solvent mix is then heated in a vacuum to evaporate off the butane, leaving behind the BHO product. The resultant extract comes in many different consistencies depending on the exact process used, ranging from a liquid oil to a stiff wax, and can contain up to 90 percent pure tetrahydrocannabinol

With solvent extraction proving a successful way to create potent cannabis extracts in large volumes, solvent extraction techniques became increasingly popular. Modern technological advancements have resulted in the development of several highly efficient extraction techniques — a number of those being solvent-based — that can produce high-quality extracts. These extracts can then be consumed using vaporizers or dab rigs (dependent on the consistency of the extract), or further processed and made into the likes of oral tinctures and edibles.

The ‘Big Three’

The three most prominent cannabis extraction techniques used today are alcohol extraction, hydrocarbon extraction, and carbon dioxide (CO2) extraction. 

Alcohol extraction is a relatively simple and straightforward extraction method that can be done under hot or cold conditions. Hot alcohol extraction is usually a small-batch process that uses the Soxhlet extraction technique to cycle alcohol solvent, usually ethanol, through the solid cannabis flower where it strips the flower of its oils. Alternatively, cold or room-temperature alcohol extraction can be more easily scaled up to larger batch sizes. This sort of alcohol extraction is best explained as like tea in a cup, the cannabis material is placed in a porous bag or vessel and left to rest in a vat of alcohol solvent, again, usually ethanol. After the cannabis ‘teabag’ is removed, the resulting ethanol/cannabis oil solution can be heated to evaporate off the solvent and leave behind a pure cannabis oil. 

Hydrocarbon extraction, usually done using butane or propane as a solvent, has matured from the early days of making BHO. In essence, it still operates by soaking the cannabis plant material in a hydrocarbon solution to draw out the cannabinoids, terpenes, and other essential oils from the plant, but the equipment involved has become much more sophisticated. Closed loop extractor systems have been developed which ensure that the hydrocarbon solvents, which can become highly volatile when mixed with air, are kept within the protective atmosphere of the closed apparatus. Within these systems, refrigerated hydrocarbon solvent is washed over the plant material and dissolves the cannabinoids and terpenes from the flower. The resultant extract solution is then passively heated to remove the butane and afford the cannabis oil. Within a closed loop system, the evaporated butane can be condensed back into the starting solvent tank and recycled in this way.

Supercritical CO2 extraction is the extraction technique, which requires the most specialized equipment. Instead of using a liquid solvent, as in alcohol or hydrocarbon extraction, CO2 extraction uses controlled pressure and temperature to turn gaseous CO2 into a supercritical fluid, a special state of matter which demonstrates properties similar to both gases and liquids, such as diffusion and solvation. By varying the temperature, pressure, and runtime of the extraction process, supercritical CO2 can be used to extract waxes, heavy oils, and light oils in individual steps by fractionation. Additionally, conditions could even be finely controlled to promote a specific concentration of compounds in the final extract, as different cannabis compounds have been found to concentrate at different rates in the CO2 extraction process. 

Dewaxing Cannabis: Temperature & Extraction Guidelines

Cloudy, murky extracts are not desirable to today’s picky cannabis consumer.

Download this free guide to learn more about the importance of dewaxing cannabis, separating lipids and waxes from cannabinoids and the techniques involved

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How to evaluate what is best for your needs

These three methods are the most prevalent methods used in today’s cannabis industry for producing cannabis extracts on a commercial-scale. Each method is distinctly different in operation, and so each comes with its own list of pros and cons, with no one method being outrightly better than the others.

When it comes to choosing ‘the best’ extraction method for a business to use, this will be heavily influenced by the properties of the final product, and the priority that each is given. Do you need a full-spectrum extract with a cannabinoid and terpene profile that closely reflects that of the original plant matter? Is that more important than the operational costs? Do you have a specific target in terms of the volume of product you can make in a day?

In order to properly evaluate the extraction methods and give each a fair comparison, there are four criteria that are arguably the most key to consider. These are the cost of production and associated equipment cost, the quality and makeup of the final product, any safety considerations, and the efficiency and throughput of the process. 

Equipment Costs

Perhaps unsurprisingly, given the specialized equipment needed, CO2 extraction has the largest associated equipment costs and running costs — even a small-scale introductory CO2 extraction set up costs $86,000 USD, compared to approximately $20,000 USD for a similar introductory hydrocarbon extraction set-up. High-end CO2 extraction equipment capable of producing cannabis extract on a commercial scale often retails for in excess of $400,000 USD.

Operational costs also aren’t limited to the equipment. If you are using complex equipment then you will also need to employ highly skilled technicians to operate them, as well as pay for the extra energy consumption that is used to power any heating or pressurization systems in the apparatus.

Quality of the Final Product

One of the factors that may make a steep initial investment worth it, is whether you need specific chemical components of the cannabis plant to be present in the final product. 

Alcohol extraction can be great value for money, but the polarity of ethanol solvents means that the ethanol will often bind to all the water soluble components in cannabis, which could result in a less potent final extract that might need further post-processing steps. Of course, if you want to produce a full-spectrum extract, this could actually be a point in favor of ethanol extraction.

Hydrocarbon solvents such as butane and propane are non-polar and will thus tend to preferentially bind to the fat-soluble components of cannabis, such as the lipophilic cannabinoids and terpenes, and give a much more potent extract that is rich in these compounds. 

Given the tunable nature of high-end CO2 extraction equipment, it is normally possible to adjust the temperature and pressure of the extraction vessel in a way that can control the concentration of terpenes in the resultant extract. In addition to this customization, CO2 apparatus is also able to extract the flavonoids and carotenoids in the cannabis plant, as well as the cannabinoids and terpenes. If the final product is desired to be as close as possible to the starting material in terms of aroma, flavor and effects, this can be good justification to make the investment in CO2 apparatus. 

Safety Concerns

When cannabis extraction is carried out by properly trained personnel in a fully licensed laboratory there is unlikely to be any real danger of a catastrophic failure that results in injury or property damage. However, it is still important that those offering cannabis extraction services fully assess any potential risks, in the event that these safeguards fail and an incident occurs. 

Despite the high pressures and temperatures it uses, CO2 extraction is generally regarded as a very safe extraction method. Equipment is manufactured with these high-pressure forces in mind, so any sort of catastrophic explosion or sudden release of pressure is unlikely. However, CO2 can present a danger if there is a leak in the apparatus, as exposure to the colorless and odorless gas can result in rapid breathing, an elevated heart rate, and even complete asphyxiation and death if present in high enough concentrations. To mitigate this risk, facilities using CO2 extraction are usually required to install audio-visual CO2 alarm systems and externally vented relief points in case of emergency.

Comparatively, hydrocarbon and ethanol extraction procedures carry more potential risk than CO2 extraction. Both hydrocarbon and ethanol solvents are flammable, and so staff must be aware of this potential fire risk when carrying out the extraction. Closed-loop extraction systems are commonly used in hydrocarbon extraction on account of the extreme volatility of the light hydrocarbons. Fortunately, the closed system prevents the solvents from mixing with the air and exploding. However, additional care must still be taken when working with these systems as a leak could result in gaseous butane or propane being released into the laboratory, causing both an explosion risk and an asphyxiation risk. To reduce these dangers, operations that use hydrocarbon or alcohol extraction will take steps to ensure that the working area is well-ventilated and removed of any potential sources of ignition.

Throughput and Efficiency

Depending on what the final product will be used for, a key priority for extraction companies can be the efficiency or rate at which extracts can be produced. 

The ‘tea-like’ methodology of cold ethanol extraction can allow large batches of cannabis material to be processed at a time, limited only by the volumes of solvent and flower that the extraction vats are able to hold. This sort of bulk-processing makes the technique an attractive prospect for businesses that require a high throughput process. Hydrocarbon closed-loop extraction systems normally cannot process as much plant matter in a single run compared to alcohol extraction, but the runtime of modern hydrocarbon extraction equipment nonetheless results in a healthy throughput, with some machines capable of processing several hundreds of pounds of cannabis plant matter in 24 hours.

The throughput and efficiency of CO2 extraction is generally much lower by comparison; even the most expensive high-volume CO2 extraction equipment is only capable of processing around 140-200 pounds of dried cannabis plant matter in 24 hours. Additionally, the pressurization and heating/cooling systems in CO2 extraction apparatus can result in high operational energy costs. Still, given that CO2 extraction can extract some of the more minor compounds in cannabis, this trade off in efficiency could be worth it if the goal is to create an end product that contains these compounds. 

The most optimal method

When comparing the most prevalent methods with the four identified criteria, there is no outright ‘best’ cannabis extraction system to purchase. The best cannabis extraction system for a company will be the one that is the most compatible with the company’s aims. It should be efficient, fit within the planned budget, and target the specific compounds that are derived to be extracted.

Alexander Beadle

Science Writer

Alexander Beadle has been working as a freelance science writer since 2017 and has covered the cannabis industry for Analytical Cannabis since 2018. He has also written for our sister publication, Technology Networks, and the cannabis industry consultant firm Prohibition Partners, among others. Alexander holds a Master's in Materials Chemistry from the University of St. Andrews, where he won a Chemistry Purdie scholarship, and conducted research into zeolite crystal growth mechanisms and the action of single-molecule transistors.


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