Extracting CBD, Insight, & Info
Updated: Nov 22, 2022
Naturally derived compounds and mixtures were the only medicinal products available for use for thousands of years. Likely, humans have used botanical “medicines” for as long as we’ve been around. Archaeological excavations have found opium poppies and cannabis in sites as old as 60,000 years B.C.! Many times in years gone by, these plants were crudely formed into a paste, cake, tincture, or otherwise compounded and consumed or applied topically. Thankfully, we now have better ways to get at the goods lurking in so much of the world around us.
There are many extraction techniques that help target compounds residing within plants. Some are more specific to the compounds they seek and some are found almost universally, but we’ll discuss the big ones related to Cannabis s. today.
Generally, extraction techniques can be broken down into two categories: solvent-based and solventless-based. Both approaches attempt to dissolve the wanted compounds (in this case, cannabinoids) and move them away from the plant matrix and unwanted compounds. Solvent-based extraction is by far the most common in the hemp and cannabis industries.
The first of these solvents is most likely the most well-known in the medical and recreational Cannabis market: Butane. Butane-extracted resin or butane honey oil (BHO) occurs when liquid butane (liquid at -0.5℃) is passed over and through hemp or Cannabis s. biomass. Generally (and more safely), this is done at both cryogenic temperatures and at pressure to ensure the butane does not evaporate into a gas. Gaseous butane is very dangerous! Butane is not the only alkane to be used in this way. Other alkanes such as propane, hexane, and heptane are all known to be used in this same way. Alkanes are a good choice since water-soluble compounds such as chlorophyll and some plant sugars are left behind, and doing this at cryogenic temperatures will also allow for in-line winterization, which we’ll discuss later. This process usually takes place in what is called a “closed loop” extractor. This term means that the butane and cannabinoids are not introduced to the open air and/or handled otherwise before separating both the butane and cannabinoids. We’ll also discuss this process later, but for now let’s move on to another favorite in the industry: Ethanol.
Ethanol has been the major extraction method in solvent-based extraction for many years, but access can sometimes be limited. Being a highly flammable and lightly corrosive liquid, proper steps must be taken to ensure safety in handling within the laboratory. Generally, this is also done at cryogenic temperatures to ensure fewer fats and sugars are gathered, but temperatures vary across the industry. There are two other problems that come with ethanol: legality and water. Alcohol (ethanol, ethyl alcohol; the same compound that makes fermented and distilled beverages so desirable) is, of course, regulated under the Federal Alcohol Agency (part of the Department of Treasury). Getting a liquor license to serve your fellow humans a nice, cold Moscow Mule is one thing, but a license to store many gallons of high-purity ethanol and use it in extraction is another. It’s also quite heavily taxed no matter the size, turning a $10 bottle of vodka into a $30 bottle of Everclear. Water is another issue: properly distilled ethyl alcohol comes out of the still at 200 proof (100%) but quickly lowers to 190 (95%). This is because ethanol is not stable in this purity and snatches water from wherever it can (generally from the air) until it reaches a new maximum of 95%. After that, it is still quite capable of gathering water when passing over and through Cannabis biomass through hydrogen bonding. Even properly cured and dried biomass can contain anywhere from 5-13% water by weight, so compounding water in ethanol during extraction over time is easy and frustrating. More water means more sugars and chlorophyll. Many in the industry also move towards denatured ethanol, which starts as 200-proof ethanol and is then stabilized by the addition of heptane, isopropyl, or another solvent compound. There are those that believe this can lead to issues in removing the solvent from the end product due to what’s called an azeotrope or lead to dangerous compounds during post-processing, but there isn’t much information to support this claim and denatured ethanol is undrinkable so it isn’t taxed the same as pure ethanol, meaning a lower cost to the extractor. Ethanol is a tried and true method for extracting oils, terpenes, and flavonoids, which makes it a common and well-tried choice in the industry.
Now for a grey area: carbon dioxide. Carbon Dioxide (or CO2 as it is commonly called) is similar to butane in the way it is used; in a closed-loop system under pressure. The grey area comes in the pressures and temperatures used. CO2 is a liquid under high pressure. It stays liquid under even higher pressure when heated as well. These pressure and temperature differences can make CO2 act in a very particular and special way: as both a fluid and a gas. As we all remember from our 5th-grade science class, gasses fill the space they are in. CO2 keeps its density as a “liquid” and can get into spaces just like a gas. It’s not the best solvent for extraction and machines that can safely handle the pressure are generally fairly expensive, but it can be a great option, especially for products like “shatter” and “wax”.
Now for solvent-less extraction methods. Some companies have started using high-pressure steam to push cannabinoids out of the trichomes in a similar way to CO2 but even less efficiently. This is very similar to the steam distillation of water-soluble plant compounds but works with pressure to target the cannabinoids.
The other most common solvent-less extraction method is Rosin Pressing. Rosin is produced by using mechanical pressure and heat to squish the cannabinoids out of the trichomes. This is a great option for small batches and gives an automatically concentrated product.
Solvent-based extraction is by far the most efficient and common way to extract across both the industrial hemp and medical and recreational Cannabis industries. Depending on the final product that you’re looking for, different methods may be better suited to manufacturing them. Going back to our post on ‘Reading a CoA’ (certificate of analysis) this can be critical in making sure that proper safety has been carried out in making that product - you don’t want excessive butane or heavy metals from an unclean preparation lab in a product you’re choosing to consume!
After extraction, there are many ways to further refine cannabinoids. Some cannabinoids will crystallize, (like CBD, CBG, and even THCa under special circumstances) making it easy to single them out and purify them. Winterization can be used to filter out and remove fats. Distillation uses different amounts of heat and vacuum to remove all solvents and can be used further to separate cannabinoids from other plant constituents. Isolates (crystalized cannabinoids), distillate (distilled cannabis oil), and crude oil all have their place in final products and depending on your circumstances or needs, may be better suited to you.
We encourage you to learn about the products you like, how they’re made, and what works best for you! As always, Blackhouse Botanicals is happy to answer any questions you may have and is here to help you in the search for the best and most efficacious Cannabis s. products for you, which we just so happen to have!