ɪkˈstrakʃ(ə)n | Noun
The action of separating hemp cannabinoids and terpenes from plant material. Manufacturers use various machines, solvents, and techniques to extract cannabis compounds.
“The CBD hash I got from a local dispensary is made using mechanical separation as an extraction method.”
“Most CBD oils on the market are made using a chemical extraction method that includes supercritical CO2.”
Mechanical Separation vs. Chemical Extraction
Mechanical (physical or solventless) separation and chemical (solvent) extraction are the two main processes used for pulling out cannabis components from plant material. The physical separation is older and has historically been used in India and the Middle East to make hashish. This extraction employs pressure or physical action to remove entire trichomes.
On the other hand, chemical extraction uses a chemical solvent to dissolve the trichomes from the plant. In the late 19th century, North American companies introduced solvent extraction to create reproducible doses of cannabis extracts. In 1896, Parker, Davis and Co., today owned by Pfizer, developed a cannabis fluid extract that stayed on its physicians’ catalog until 1937.
Overview of Mechanical Separation
Manufacturers use methods like centrifugal action, gravity separation, and filtration to separate the trichome glands from the plant. These are the most common methods:
- Sieving the plant matter
This method involves sieving the ground plant by hand or in mechanical tumbles made of screens. It delicately removes the trichomes, which results in a powder called kief. Kief is a hemp CBD concentrate that can be smoked or vaped on its own or sprinkled onto CBD flower in a bowl, joint, or bong. Kief can be further pressed into hash for long-term storage.
- Ice-water method
This method combines plant material, ice, and water in a vessel. As part of this mix, the plant material is agitated until the trichome glands fall off the plant and sink to the bottom. The end product is the concentrate known as bubble hash, which, as the name implies, bubbles when burned. Bubble hash can be smoked on its own or combined with CBD flower. Top-shelf hash can be dabbed, while low-grade can be pressed into rosin.
- Cold and warm press methods
These methods involve heat and pressure to make rosin or remove the cannabinoids and terpenes from the plant material. Manufacturers apply heat and pressure to the plant material until the resin glands are removed. This concentrate can be dabbed or consumed using a dab pen.
Aside from rosin presses that can be costly, most solventless methods are easy and inexpensive to set up and operate. But, the downside of these methods is that they are not efficient for commercial-scale production. Using dry-ice (frozen carbon dioxide, or CO2) to create kief may come as the greatest hazard due to the potential for freezer burns if the person is not cautious.
Overview of Chemical Extraction
To remove trichomes from the cannabis plant on a commercial scale, manufacturers use solvent-based extractions. As non-polar compounds, trichome glands require a non-polar solvent to remove them from the plant. The main solvents employed during this type of extraction are:
- Supercritical carbon dioxide
These solvents display toxic, flammable, and asphyxiant properties but are generally recognized as safe (GRAS) by the Food and Drug Administration (FDA) if handled properly. The pharmaceutical and food industry has used these solvents for decades. If managed in proper labs of a closed-loop system, engineering, and administrative controls, these chemicals are safe.
Chemical processes use a liquid solvent to “wash” the plant matter of its therapeutic compounds. After the initial extraction, processors remove the solvent from the extract for it to be made safe to consume. As cannabinoids are sensitive to temperature, manufacturers use solvents with extremely low boiling points. That way, they maintain the full spectrum of compounds without boiling them off during the process of removing the solvent.
Extractions based on solvents typically occur under relatively low pressures (15 to 150 PSI or pounds of pressure per square inch) and low temperatures (-30 to -70 degrees Fahrenheit). New methods based on supercritical fluids use much higher pressures (1,000 to 9,000 PSI) and temperatures (35 to 215 degrees Fahrenheit) to dissolve therapeutic compounds.
Types of Chemicals
Depending on the end goal, manufacturers use several types of solvents and chemicals to extract cannabis compounds — with varying efficiency.
For example, if they want to strip all compounds from the trichomes, they use butane, a light petroleum gas-based solvent. If they aim for selective compounds, like terpenes and certain cannabinoids like cannabidiol (CBD), they use a selective solvent like CO2. Repeated movement of this solvent through the plant material in a closed-loop system gradually approaches all of the cannabinoids.
Supercritical Fluid Extraction (SFE)
This type of extraction uses a fluid that has been heated and pressurized above its critical point to pull CBD (and other phytocannabinoids) from the plant. At certain temperatures and pressures, CO2 exhibits gas and liquid properties. When it reaches this phase, the liquid’s solubility increases, and it moves through the plant material like a gas but breaks down trichomes like a liquid. Carbon dioxide (CO2) is the preferred solvent for SFE because it’s relatively available and low cost.
The CO2 cannabidiol (CBD) extraction is divided into supercritical, subcritical, and ‘mid-critical’ categories. Supercritical is the most commonly used, it’s safe and provides a pure end product.
Solvents like ethanol, butane, and propane are among the most common solvents used in industrial-sized extraction systems to pull cannabinoids and other compounds from plant matter. All of these chemicals generally do the same thing but are preferred over one another based on desirable outcomes.
Ethanol is low-grade alcohol that extracts the full range of cannabinoids and terpenes from the hemp plant. This makes the final product safe for consumption, but ethanol also extracts chlorophyll, leading to unpleasant side effects. Processors filter the extract to remove the chlorophyll, but this significantly reduces the potency of the oil. Butane creates a stronger oil than ethanol, but it’s more likely to contain solvents that could irritate the lungs.
Processors add the liquid to the plant material. The liquid strips away the cannabinoids and flavor from the plant material but leaves some green coloring. Once the cannabinoids are pulled out, they heat the liquid to evaporate the solvent.
Before extraction, processors grind or mill the plant material. Then, they load it into the material column, where a vacuum pump removes all oxygen from the system. The solvent column is then cooled to -40 degrees Fahrenheit, and the material is soaked with a liquid solvent. Once the solvent does its job, they heat the residual solvent via a vacuum oven under proper heat to return it to gas form. As a gas, the solvent returns to its original column, performing the loop in a closed-loop system.
- Cured nugs – the nugs of the cannabis plant hold the greatest concentration of trichomes over the rest of the plant material. Processors use them to create “nug run” concentrates. These concentrates vary from shatter to budder to sauce and display fantastic aromas, flavors, and potent effects. They are considered better than “trim” runs or concentrates made from cannabis trim.
- Trim – This plant material is made up of trimmed sugar leaves that cup the buds. CBD concentrates made from this material have fewer terpenes and cannabinoids than nug run concentrates or live resin extracts.
- Live resin – A new method of creating cannabis concentrates. To make live resin, extractors freeze a freshly chopped plant immediately, using liquid nitrogen or a freezer. Once they freeze the entire plant material, the extraction begins. The method of extracting live resin is highly rated for its preservation of aromatic, flavorful terpenes. It produces the most potent, aromatic concentrates on the market.
Extraction is a process that refers to pulling out cannabinoids and terpenes from the hemp plant material using a solvent or mechanical separation.