The Best Cannabis Extraction Methods for Marijuana Concentrates
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As the cannabis industry has grown, so too has its understanding of cannabis extraction. So much so that the field is now a science unto itself, filled with thousands of expert technicians and processors.
In short, cannabis extraction is the process of removing the desirable cannabis compounds, such as CBD and THC, from the rest of the plant matrix.
But how is this done? Well, there are a few different methods, each with their own pros and cons and champions and nay-sayers. Let’s take a look at some of them.
Cannabis extraction methods:
Good extraction method for:
- cannabis distillates
Several common forms of cannabis extraction rely on a solvent to strip the unwanted material from the desired chemicals.
One of the more popular solvents is ethanol, and for good reason. Ethanol extraction is one of the most efficient extraction methods for processing large batches of cannabis flower, and can be done in hot, cold, or room temperature conditions.
In brief, the cannabis is soaked in ethanol, the plant material is then removed, the liquid filtered, and the alcohol is removed with some form of evaporation.
“Ethanol extraction offers higher throughput compared to CO2 and hydrocarbon systems; it’s perfect for making distillates and isolates at scale,” Jim Moore, vice president of new product development at Prospiant, wrote in Analytical Cannabis.
But ethanol poses a problem, its inherent polarity. This means that it has a propensity to mix with water and molecules like chlorophyll, which should instead be removed from the extract, as it produces an undesirable, bitter flavor. As such, ethanol extraction often requires several post-processing clarification steps to fully clean the product.
Cold alcohol extraction also helps to avoid this problem, as the cooler temperatures make it harder for the unwanted polar plant waxes and chlorophyll to dissolve in a polar ethanol solvent.
On the health and safety side, ethanol is also highly inflammable, so special care should be taken when transporting and utilizing it.
Jenna Agin, cannabis product manager at Neptune Wellness Solutions, detailed the risks and rewards of alcohol extraction to Analytical Cannabis in a 2020 webinar. Here's what she had to say:
Cannabis & Hemp Extraction: Process Selection and Regulation. Ethanol extraction discussion begins at 07:51 and ends at 08:19.
Ultrasound-assisted alcohol extraction
Ethanol's polarity problem can also be amended through the careful use of soundwaves.
Once the ethanol has been added, ultrasound waves can be used to form microbubbles. These microbubbles collapse within a few microseconds of their formation, creating tiny, localized hotspots that can reach temperatures of around 5000 Kelvin and pressures above 500 bar. These extreme conditions produce powerful hydro-mechanical forces that can disrupt the cell walls of the cannabis matrix, allowing the plant’s natural oils to dissolve into an alcohol solvent more readily.
Alcohol isn’t the only popular solvent for cannabis extraction, there’s also carbon dioxide (CO2). With this process, high pressure and heat are used to turn the CO2 supercritical, meaning it’s simultaneously like a liquid and a gas. When passed over the cannabis, the fluid extracts plant waxes and oils from the matrix.
But the method doesn’t come cheap. The equipment required is much more expensive than that needed for alcohol extraction, although the process does produces higher yields and less valuable material is lost. Plus, this method can be adjusted to extract specific compounds by changing the temperature, pressure, or runtime.
“While CO2 requires a higher initial capital investment, the advantages this method offers made it the obvious choice for long-term viability,” Lo Friesen, the founder and CEO of the Seattle-based cannabis company Heylo, told Analytical Cannabis.
Once the cannabis components have been extracted, the supercritical CO2 goes into a condenser and turns into a liquid that can be filtered and used again. Consequently, very little reagent is used. That makes the method economical to run and reduces the need to dispose of waste.
In addition, if any CO2 remains in an extract after the process, it just evaporates. That is especially important for any preparations for medical uses as a producer using this method can guarantee that absolutely no residual solvent will be present in the final product.
Good extraction method for:
- THC diamonds
Other popular solvents include the hydrocarbons butane and propane.
Like alcohol extraction, the cannabis material is drenched in butane, which extracts its oils. Thanks to butane’s low boiling point, it then doesn’t take much heat (-0.5°C or 31°F at standard pressure) to boil off the solvent, leaving the desired compounds behind.
Many extractors who prize their terpenes champion this method, as the low boiling point is less likely to affect the temperature-sensitive terpenes.
“Butane/propane extraction has a lower throughput than ethanol but enables the processor to capture all major terpenes and cannabinoids in one operation,” Prospiant’s Jim Moore wrote in Analytical Cannabis.
“The method is best for concentrates such as dabs, sauce, shatter and diamonds, which are gaining popularity with consumers.”
Cannabis extract being dispensed.
The problems with butane THC extraction
But this method also includes some potential hazards. For one thing, butane burns easily in its gas phase. So, the temperature used must be managed carefully otherwise there is a serious risk of the gas exploding. In addition, a system should include circulators that remove and recycle the butane, as it is highly toxic to humans.
If using propane instead of butane, the extraction occurs at a lower temperature because propane has a lower boiling point than butane.
Like the butane process, though, special care must be taken with propane extraction to remove as much of the chemical as possible and prove it.
Jenna Agin, cannabis product manager at Neptune Wellness Solutions, detailed the risks and rewards of hydrocarbon extraction to Analytical Cannabis in a 2020 webinar. Here's what she had to say:
Cannabis & Hemp Extraction: Process Selection and Regulation. Butane extraction discussion begins at 06:00 and ends at 06:47.
While the three methods listed above are by far the most common techniques used to extract cannabis, there aren’t the only ones. Several novel methods are preferred by more rudimentary extractors, including one that uses water as a solvent.
This technique isn’t a step too far away from giving the cannabis material a cold bath. Firstly, the plant matter is frozen right after being trimmed. This frozen marijuana material is then washed in cold water. Because cannabinoids are denser than water, the compounds can separate from the leaf material during the wash. After this, the cannabinoid-rich water only needs to be filtered through a series of micron bags before it’s ready to be used.
Away from the technical, mechanical world of traditional cannabis extraction, a new, more natural method is growing in popularity: bee-assisted extraction.
Given that different flavors of honey can be made from different types of nectar, one Israeli company wondered if CBD-flavored nectar could produce a CBD-infused product. And, perhaps surprisingly, it can, according to Ilan Ben Simon of Bee-Fuse.
“The product is basically organic natural,” Ben Simon told Analytical Cannabis. “We are using a lot of fruit and vegetable juices to create a natural fructose nectar.”
Not only is Bee-Fuse’s CBD honey viable, it’s apparently quite potent.
“[One theory behind the high bioavailability] is that when the bees are processing cannabinoids and simple sugars and glycoproteins, they are making a new molecule that contains the cannabinoids inside the glycoprotein and the blood brain barrier does not distinguish between both of them. It takes it as sugar. And this is why the penetration to the body so fast,” Ben Simon added.
Update: This article was updated on August 23, 2021, to provide up-to-date information on cannabis extraction methods.