Peak Purity: Supercritical Extraction and Fractional Distillation of Cannabinoids

Monday, June 17, 2019 8 min

Cannabis products are currently in a state of rapid evolution, reflecting the cannabis market’s expanding technological applications and changing consumer tastes. There now exists a wide array of cannabis experiences for people to choose from, ranging from basic flower products to extracts and potent distillates. The field of CBD research is still new, but preliminary studies suggest the compound may carry benefits in areas like pain management, mental health, seizure control, and more. Following the Farm Bill of 2018, demand for cannabis products, and entrepreneurial freedom to supply them, is set to increase significantly.

Much of the cultural progression surrounding these products has to do with extraction and distillation techniques — processes which aren’t necessarily new, but which have only recently been applied to cannabis. The search for more control over purity has led to distillates that exceed 99% potency for both THC and CBD. In this post, we’ll cover the main methods of cannabis extraction, the differences between distillates and extracts, and the basics of CBD fractional distillation.

The Workflow of High-Quality Cannabis Distillates — Cannabis Extraction Methods

Before you can refine a distillate, you first need to produce a crude extract. Hash oil was one of the first types of cannabis extract to become popular. In the 2000s, other forms of extracts began to dominate the scene. These are often referred to as “concentrates” and include types as varied as rosin, shatter, wax, oil, crumble, dabs, and many similar products.

As a concentration, an extract basically amplifies the components of a strain of cannabis, so a high-CBD extract will most commonly come from a high-CBD plant. Crude extraction does not allow the producer to alter composition by isolating certain cannabinoids or terpenes, though CO2 extraction allows for some “steering” from the chemotype of the input material to minor variations in the chemotype of the output extract. ThatThis is commonly acheieved through short-path distillation. Depending on variety, cannabis plants tend to have a cannabinoid concentration of 10-25%, whereas crude extraction can increase that concentration to 50-80%. The most widely used extraction methods use a solvent to dissolve the desired compounds out of the plant and then separate the solvent from the compounds by evaporation.

Butane extraction has been used in industrial applications for many years. Cannabis products produced by butane extraction include BHO (butane honey/hash oil), dabs, and wax. Butane is regulated as a volatile organic compound. It’s an explosive and flammable hydrocarbon and requires extensive risk mitigation when handling.

Ethanol can also be used in extraction. Ethanol is a liquid at room temperature, and the FDA classifies it as GRAS (Generally Regarded as Safe for human consumption). It’s a little easier to work with, but it is also flammable Further, its polarity gives it the tendency to dissolve undesirable compounds such as chlorophyll in addition to terpenes and cannabinoids.

Another method, known asUnlike the butane and ethanol methods, supercritical CO2 extraction, works without the use of these chemical solvents. CO2, or carbon dioxide, is non-toxic and non-flammable, and it has many of the benefits of these solvents without the safety risks. Strictly speaking, CO2 extraction does not simply use CO2 gas but rather uses supercritical CO2 (scCO2), which is capable of acting with the properties of both a liquid and a gas. This means it can pass easily through the raw plant material, while dissolving cannabinoids as a solvent would. It’s also possible to control the parameters of scCO2 through temperature and pressure, tuning it to pick up certain compounds more efficiently, while leaving others behind. —tThis can avoid undesirable components such as chlorophyll in the finished extract.

Once the process is complete, the CO2 can be recycled or released into the atmosphere. It does not create a carbon footprint, because nearly all commercially available CO2 is recaptured from the atmosphere in the first place. The cannabis extract or concentrate produced this way can then be further refined into a distillate, and many turn to fractional distillation to accomplish this.

What Is Cannabis Distillate? — Full Spectrum CBD, CBD Isolate, and More

Distillates are becoming more popular with today’s cannabis consumers. CBD fractional distillation offers a high level of control over distillate purity, such that it can be rendered odorless and flavorless. Many people who enjoy incorporating cannabis into their foods prefer to add a distillate that won’t change the flavor or aroma. Additionally, certain CBD distillates can guarantee the complete absence of THC. This is important for patients who use CBD in treatment and don’t want any THC.

CBD isolate is just that — isolated CBD. It’s a type of cannabis distillate that often comes in the form of a powder and is usually 99% CBD. People can add CBD isolate to their foods or create their own oils at home with it. To produce CBD isolate, high-CBD cannabis undergoes an extraction process, followed by further refinement. This can include winterization, which gets rid of any plant fats, and rotary evaporation to remove any ethanol left over from the winterization process. Fractional distillation further refines the finished product.

Full-spectrum CBD distillate is a high-CBD product that includes other cannabinoids like CBN, CBL, and CBCVA. The principle behind full-spectrum CBD is based on the entourage effect: the idea that a plant compound can be more effective in synergy with other compounds. Fractional distillation of cannabinoids allows for the separation of each cannabinoid, so a producer can choose what goes in the spectrum and in what proportions. Full-spectrum CBD products can havecontain other cannabinoids, terpenes, and even some residual non-fibrous plant matter.

Because fractional distillation of cannabinoids involves separating all cannabinoids and then adding them back together to achieve particular blends, both CBD isolate and full-spectrum CBD distillate can be made THC-free. For THC-free products, fractionally distilled THC is removed. This process adds value to the product and increases cost to the consumer, but it’s worth it for people who need to be sure that there’s no THC in the product. Fluid distillates can be used sublingually, topically, orally, or through inhalation. Fractionally distilled THC can also be used on its own as THC distillate.

Cannabis Distillate Process—What Is Fractional Distillation?

Think of terpenes and cannabinoids as fractions of cannabis. Each of the compounds that make up the plant is unique, and each one has a particular boiling point. Fractional distillation of cannabinoids separates these compounds based on their boiling points.

Let’s say we have a mixture that’s made up of three compounds. Compound A has a boiling point of 95°, B has a boiling point of 105°, and C’s boiling point is 115°. If we heat the mixture slowly until it just reaches 95°, compound A will begin to evaporate. We can then collect the evaporated compound and cool it down to distill it. This is a simplified example, but it’s an easy way to understand the benefits of fractional distillation. Working incrementally up in temperature, the remaining constituents can be likewise individually distilled.

Now for a more in-depth description of fractional distillation. A typical fractional distillation machine starts with a flask of extract to be distilled. The flask is heated, and vapors begin to rise into a glass column. The vapor that is the most volatile will exit the column into the next stage — a glass tube that cools the vapor, causing it to condense and drip down into the final flask. This process can be repeated a number of times at different temperatures to separate all the components of a mixture. Fractional distillation can be performed on an industrial scale, but a benchtop fractional distillation kit can also facilitate small-batch CBD and THC distillation. With fractional distillation, there’s no solvent. All there is to manage is a heating element, a vacuum pump, and a condensation apparatus.

Back to our simplified example. Say the three compounds have boiling points just one degree apart. Vapors from all three could evaporate simultaneously. To solve this problem, fractioning columns have steps, or glass trays, built into them. The temperature slowly cools as vapors go up the column, so compounds with slightly higher boiling points will condense on the lower steps and drip back down into the heated flask. This allows for a high degree of control over fractioning individual compounds.

Supercritical CO2 Extraction and Fractional Distillation of Cannabinoids — The Way of the Future

The recent Farm Bill will hopefully pave the way for more scientific research on CBD. Whether that happens sooner or later, hemp is poised to become the new cash crop right away, with experts saying the hemp CBD market could triple in size by 2022. Those predictions have had a huge influence on hemp farming; in 2018, 78,000 acres of hemp were grown, and that number is expected to jump to 125,000 in 2019.

What’s the best way to keep up with the times? Supercritical CO2 extraction combined with fractional distillation is the simplest way to produce in-demand CBD distillates. OCO Labs can provide affordable CBD extraction machines that give you precise control over every run. Our Modular Tabletop Extractors are designed to be easy-to-use and safe for any operation. With our extraction products, you can cater confidently to the cannasseur market.

We update our blog regularly, so stay tuned for the latest on fractionally distilled THC, CBD fractional distillation, cannabis-derived extracts, supercritical CO2 extraction, and much more!