Extraction: Common Misconceptions
Ethanol vs. Supercritical CO2 vs Hydrocarbon Extraction
The below article was submitted by the author Sarah B and first appeared as an educational paper published by Harmony CBD.
Cannabidiol (CBD), one of the three main chemicals found in the trichomes of the cannabis plant, has gained a lot of attention in recent years as more studies show a variety of potential applications for it. You can find CBD in almost every type of cannabis plant including:
• cannabis plants containing THC, the psychoactive chemical that makes you feel ‘high’
• varieties of the cannabis plant specifically bred to be high-CBD/ low-THC
• industrial hemp plants that contain no THC and have no psychoactive effect
There are a number of ways of extracting CBD from any of these varieties of cannabis. If the plant you start with contains only CBD (like industrial hemp or a high-CBD cannabis strain); there are multiple extraction methods which are very simple and require little equipment.
The most common methods use some type of solvent. This can be a liquid solvent, CO2, or an oil solvent. If the plant material you start with contains THC as well as CBD (such as smokable cannabis), the process to separate CBD from other cannabinoids is more complex and generally requires professional equipment. To avoid getting too technical, let’s look mainly at extraction methods for CBD-only plants.
In this method, plant material like flowers and trim are put into a container. Liquid solvent (usually butane, isopropyl alcohol, hexane, or ethanol) is run through the plant matter to strip it of cannabinoids and flavours and transfer them into the liquid. Then, the liquid is evaporated away from this mixture to leave only concentrated chemicals and flavours in the form of an oil.
benefits of this method are many— it is the most simple, equipment-free, and inexpensive way to extract CBD, but not without some downsides. One concern is that solvents can leave traces of impurities in the finished CBD oil (meticulous processing methods and the right solvent can minimise this). Also, some liquid solvents remove chlorophyll from the plant along with cannabinoids and flavours, giving the finished oil a greener colour and more bitter taste.
Also, some liquid solvents remove chlorophyll from the plant along with cannabinoids and flavours, giving the finished oil a greener colour and more bitter taste.
However, because these negative effects can usually be countered by adjusting specifics in the process, this remains the most common method for CBD extraction.
Carbon Dioxide (C02) is a unique molecule that can function as any state of matter— solid, liquid, or gas— depending on the pressure and temperature it is kept under. Because variables like pressure and temperature have to be kept very specific in a C02 extraction, this extraction method is usually done with a piece of equipment called a ‘closed-loop extractor’.
This machine has three chambers: the first chamber holds solid, pressurised C02 (commonly known as ‘dry ice’), the second chamber contains dry plant material and the third chamber separates the finished product.
When performing the extraction, the solid C02 from the first chamber is pumped into the second with the plant material. This second chamber is kept at a specific pressure and temperature which causes the C02 to behave more like a liquid (although it’s actually somewhere between a liquid and gas in this state, referred to as supercritical C02) so that it runs through the plant material and extracts chemicals and flavours, much like in the liquid solvent process. Then, the C02-cannabinoid mixture is pumped into a third chamber where it is kept at an even lower pressure and higher temperature so that the C02 gas rises to the top of the chamber while the oils containing chemicals and flavours from the plant material fall to the bottom to be collected for consumption.
There are many benefits of this method. It doesn’t require a long evaporation process like a liquid solvent extraction and there is minimal risk of contaminants in the finished product.
Because this method carefully controls temperature and pressure, it can also be used to separate CBD from cannabis also containing THC.
CBD extracts from the plant at a lower temperature and pressure than THC, so careful adjustment of the pressure and temperature in the second chamber can isolate the specific cannabinoid you want to extract. Closed-loop extractor systems are very pricey, however, which is why this type of extraction is generally only used by professional CBD producers.
Using oils, especially olive oil, to extract cannabinoids from hemp and cannabis is a practice that dates back to biblical times or even earlier.
Many home-producers who make their own CBD products still employ this simple extraction method. First, raw plant material must be decarboxylated, or heated to a specific temperature for a certain length of time to activate the chemicals in the plant. Plant material is then added to olive oil and heated to 100°C for 1-2 hours to extract the cannabinoids. With this method, the olive oil cannot be evaporated away after the process, so users must consume much higher quantities of this type of extracted oil than the highly-concentrated oil produced by other methods. Infused olive oil is also highly perishable, and so must be stored in cold, dark place.
This makes it unviable for commercial CBD producers, but a simple, safe, and inexpensive option for individual enthusiasts.
While these are currently the most common methods in which CBD is extracted from cannabis or hemp; technology in this exciting new field is constantly updating, so new methods will surely be seen in the coming years as the industry expands.
Each extraction method is best suited to specific circumstances: whether you are a company or an individual, for what type of product you are extracting CBD, desired flavour, strength and consistency all play a part in which method should be chosen. Companies producing CBD often put extracted CBD through subsequent processes to make a variety of other products, such as Harmony’s CBD e-liquids, CBD crystals, cosmetics and much more.
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