Hemp Extraction methods:

To make CBD products, we need to first process the cannabis plant to obtain crude extract or raw oil. Most of the CBD and other cannabinoids are found in the resin which is coating the plant. With a closer look at the cannabis flowers, which is the part with the most resin, we can see little white crystals. These are called trichomes. They are the resin glands containing different cannabinoids and terpenes. Because of their bitter taste, strong smell, and sticky feel, they make the plant unappealing for animals to eat.

Back in the day, more primitive ways were used to strip the resin from the cannabis flowers. By simply rubbing hands on the cannabis blooms, and then scrape the sticky resin of hands, we obtain hashish. This is still a traditional way of capturing the plants’ essence in India. In Marocco, a different approach is taken. They sift the dry cannabis flowers through a fine screen and then press the sifted trichomes into hashish. The goal of separating trichomes from the plant is to concentrate the cannabinoid content. Also, to make cannabis edibles, some sort of fat or alcohol is needed as the cannabinoids are also not water-soluble. The 4000 years old bhang recipes, where the ancient Asian tribes infused milk or ghee with cannabis, and the space cookies from the hippie generation, where they infused butter with cannabis, are also some forms of cannabis extracts.

All these different techniques found their way into the modern world but got left behind for other methods that result in a much better end product.

As laws regarding cannabis are changing for the better, several methods of botanical extractions from other industries (pharmaceutical, food, cosmetics) are being implemented to separate the cannabinoids from the cannabis plant. Let us analyze the 3 most popular ones.

Because cannabinoids are not soluble in water, some kind of solvent is needed in the process.

The idea is simple:

to soak plant matter in a solvent => after infusion, to discard the plant matter => to separate the cannabinoids from the solvent.

Alcohol is both a polar and non-polar solvent. It quickly takes off the resin from the plant matter, making it a great candidate for extracts.

As alcohol-based tinctures were pretty common in medicine, cannabis tinctures were available until its prohibition in the 20th century. At the beginning of the 21st century a Canadian cannabis activist Rick Simpson, claimed to have cured his skin cancer with a cannabis tincture applied topically. Despite his doctors not believing him and having troubles with law enforcement officials, Rick set out on a mission to share the cure for cancer. Thanks to the internet, his story spread like a viral tidal wave and he became one of the most influential figures in the history of cannabis. Sharing his method in detail, which only involves cannabis, a couple of home utensils and ethanol (other solvents in case alcohol is unavailable) the recipe reached many patients around the world, suffering from cancer and other illnesses.

Because of the extremely positive effects, the Rick Simpsons oil (RSO) had on all kinds of ailments, a lot of companies entering the medical cannabis business based their products on his technique. Moving from home kitchens to professional labs, extractions involving alcohol got fine-tuned and adapted to large scale production.

The principle remains the same, soaking cannabis plant matter in alcohol (usually ethanol derived from grains).

The downside of this process is the polarity of ethanol, which also brings unwanted water-soluble compounds like chlorophyll into the extract. With minimizing the amount of time ethanol and plant matter stay in contact, along with lower temperatures, this too can be solved. After the resin is dissolved in the ethanol, ethanol needs to be evaporated. During the distillation process, most of the ethanol is recaptured, which can be reused, greatly diminishing the processing costs. After the evaporation, we are left with high-quality cannabis oil which can be used in many different ways or purified further. The ethanol extraction proves to be on par with others with one main issue. High proof ethanol is a flammable fluid, so its use and storage are dangerous and even prohibited in some countries.

Hydrocarbon extraction (butane, propane, hexane,..)

Derived from petroleum and natural gases, these volatile substances are great solvents for cannabis extraction. They have been made famous in the food industry by torching steaks for a nice sear and as fragrance extractors in perfume industries. Now they are repurposed for cannabis extraction due to efficiency and excellent terpene retention. The two main disadvantages are associated with this method:

-compared to ethanol hydrocarbons are even more flammable, making the process a potential fire hazard

-leftovers of these chemicals, which are considered toxic, might still be present in the end product

Even though both of the problems can be avoided if the extraction is done professionally, the industry doesn’t seem to favor hydrocarbon extractions. This extraction method got its bad reputation because of accidents where amateurs at home attempted to make extracts with canned butane using steel/glass tubes. These well-publicized accidents, ranging from light burns to basement explosions, were further criticized in campaigns supported by CO2 extraction companies to put a bad image on competition.

The principle of this method is very similar to ethanol extraction, where the solvent passes through plant matter, removing the resin. Done correctly in a closed-loop system, no gasses can escape, diminishing the fire danger. After the solution with gasses and resin is obtained, the gas needs to be recollected for later use and purged from the extract to remove toxic compounds. The extract we remain with is of remarkable quality, favored by many for the higher terpene content, resulting in a better taste and flavor. With improved safety measures, hydrocarbons definitely have a spot in cannabis extraction.

Considered the best in the industry, this safe, non-toxic, environmentally-friendly method doesn’t seem to have any flaws. A relatively new way of processing cannabis, the method is widely spread among other industries.

A few examples where co2 is used for:

-removing caffeine from coffee beans,

-removing nicotine from tobacco,

-crafting essential oils

-hop extraction for beer

-Producing carbonated drinks

Carbon dioxide is a non-toxic, non-flammable compound, with all the pros of the previous solvents. It is no wonder the leading form of cannabinoids extraction at this time. We can perform the CO2 extraction in 2 different ways, subcritical or supercritical.

As CO2 is a gas, it first needs to be put into a liquid form. This is done by heating it above 31.10C (critical temperature) under 1,071 psi (critical pressure) to become a supercritical fluid. This supercritical fluid, with both the properties of a gas and a liquid, then passes as a solvent through cannabis material to extract all the valuables. The liquid CO2, now rich in extracted cannabinoids and terpenes passes through a separator where we collect the extract. CO2 is moved into a condenser vessel where it is liquefied and recycled back to a storage tank.

We end up with a high-quality raw extract that can be used for products or refined even more.

The less popular of the two, this extraction uses the least pressure and the lowest temperatures. This way we are preserving more terpenes and other heat-sensitive chemicals we desire to extract, at the expense of time required for the process. Also, with the slower process, large molecules of lipids, waxes, and chlorophyll are not extracted which results in lesser yields but a purer product.

It seems logical for the industry to favor the supercritical extraction as a faster and better yielding method. With tuning the pressure and temperatures, we can greatly impact the time, yields, and quality of the extract. That is why co2 extractions appear to be the future of cannabis processing, with its only disadvantages being the initial investment and maintenance costs.

Other processes involved in cannabis extraction:

a process of extract refinement where the crude extract containing unwanted waxes, fats and lipids is mixed with ethanol and then frozen. With freezing, the unwanted compounds become bigger or float on top which eases the filtration. After filtration, the ethanol needs to be distilled to separate it from the oil. With we create a cleaner extract of superior quality.

Usually referred to as the distillation of ethanol after winterization. The cannabinoids have a much higher boiling point than ethanol so the cannabis extract/ethanol mixture is put into a rotary evaporation system. This solution is then gently heated to evaporate the ethanol until all of it is boiled off. Because of the higher boiling point, no cannabinoids were lost, but some more volatile terpenes might not be present in the refined oil we end up with. At the expense of losing some terpenes during the evaporation process, we are activating more cannabinoids in a process called decarboxylation.

the cannabinoids present in the resin of the cannabis plant are in a form of acid and are inactive if ingested. The decarboxylation is a natural process where cannabinoids in the form of acid are transformed into active form (CBDA-> CBD, THCA->THC). Natural decarboxylation occurs very slowly, so we can speed it up by applying heat to the cannabinoids. In the case of smoking or vaporizing, the cannabinoids are decarboxylated almost instantly because of high heat. When we want to activate cannabinoids to put them in an edible form we want to apply less heat. Way below their boiling point, like in the process of distillation.

The decarboxylated cannabinoids are activated and better absorbed, making the extract more potent.

Conclusion

At the end of the day, the extracts obtained with all 3 methods can be of very similar quality. With the biggest difference being the costs involved, it mostly depends on the size of the business which method is gonna be adapted.

It is also hard to predict which extraction method is gonna prevail as new technologies are making it into the field to optimize operations. Extractions assisted by microwave energy are way more efficient for large scale processing in terms of time and returns. Ultrasound-assisted extractions, used to obtain vitamins and antioxidants from herbs, show great promise in preserving delicate compounds like cannabinoids and terpenes.

It also depends on the needs of the end-user on how the market behaves.

Rosin method, where heavy multi-ton presses provide high-end extracts without the use of any solvents, might keep satisfying the cannabis connoisseurs on a commercial level.

Simple extractions of macerating cannabis in alcohol or cold-pressed oil will definitely stick around for the DIY home experiments, which might diminish the need for commercial extractions.

And lastly, the law will have the last word on what, where and how can be extracted, dictating how the market evolves, hopefully at the benefit of the consumer.