Advancing technologies have paved the way for a range of new and sophisticated cannabis extraction methods. Whereas butane extraction was once the dominant player, we’re now seeing a range of alternative extraction methods—each with its own list of pros and cons.
But with more options comes greater confusion. How do you decide between the growing list of options? It starts with a basic understanding of how each extraction method works.
The Most Popular Cannabis Extraction Methods
There are several common cannabis extraction methods, but the most popular and efficient methods are:
- Supercritical CO2
If you’re looking to produce cannabis extracts at a commercial level, you’re most likely going to rely on one or more of these methods.
Hydrocarbon extraction involves the use of a hydrocarbon solvent, usually butane or propane. The actual extraction generally takes place within a closed-loop extractor vessel (open-blast systems were once common but have fallen out of favor as a result of being unstable, dangerous, and illegal for use in commercial extraction facilities).
In a closed-loop system, the extraction process follows these basic protocols:
- The solvent is chilled to a temperature below its boiling point.
- The solvent is flushed through a narrow material column where it absorbs the cannabis plant material and collects the cannabinoids and terpenes; the plant matter dissolves.
- The resulting crude oil mixture passes into a collection tank.
- The collection tank is heated to evaporate the solvent.
- A gas compressor pulls the remaining solvent vapors from the collection tank and cools them back into liquid form.
- The liquid solvent cycles back into the solvent tank, and the process is repeated until the remaining solvent is purged from the system.
- The cannabis extract is removed from the collection tank.
After the extraction has been completed and the solvent has been purged, the extract may undergo post-processing including dewaxing and/or winterization.
Benefits of Hydrocarbon Extraction
- Hydrocarbon extraction doesn’t require a high-quality starting material. It can produce potent cannabis concentrates even if you start with a lower-quality batch.
- Excellent throughput when compared to ethanol and CO2. A good closed-loop system can produce larger quantities in less time.
- Hydrocarbons like butane and propane are ideal for full-spectrum extracts as they can effectively pull all types of active compounds from the plant.
Drawbacks of Hydrocarbon Extraction
- Hydrocarbons are flammable, so extreme caution and skill are required even when working with a closed-loop extraction system.
- While hydrocarbons are effective for producing full-spectrum extracts, they’re not a good choice for isolating individual cannabinoids like THC or CBD because the dissolution process results in some of the cannabinoids being lost.
- Post-processing—like dewaxing or winterization—is usually required with hydrocarbon extraction.
- Hydrocarbon labs generally cost more to build, not just due to the equipment but due to the regulatory requirements.
Ethanol extraction is similar to hydrocarbon extraction in that the solvent is used to draw out the cannabinoids and terpenes via dissolution. However, the process is a bit different. Whereas hydrocarbon solvents pass over the plant material, ethanol extraction generally involves submerging the cannabis within the solvent. There are two main types of ethanol extraction (each with its own variations): warm ethanol extraction and cold ethanol extraction.
A typical cold ethanol extraction might look something like this:
- The ethanol is chilled to a temperature as low as -40°F.
- Cannabis flower is submerged in the solvent.
- An ethanol filtration skid is used to filter out any unwanted lipids, chlorophyll, and other plant matter.
- The solvent is heated and purged, usually with the help of a falling film evaporator (FFE) or by means of rotary evaporation. As with hydrocarbon extraction, the extract may undergo multiple rounds of purging.
Once the initial processing is complete, the extract may undergo various forms of post-processing, including distillation, decarboxylation, or dewaxing.
Benefits of Ethanol Extraction
- Ethanol is subject to more lenient storage regulations than hydrocarbons, meaning that you can keep more solvent on hand and process more extract with fewer restrictions.
- Ethanol is ideally suited to making full-spectrum tinctures. The extraction process allows you to boil off any unwanted terpenes and flavonoids, leaving just the desired cannabinoids (which can then be combined with a carrier liquid and processed as a tincture).
- Ethanol extraction is slightly more cost-effective than hydrocarbon extraction because it typically has lower electrical costs and lower labor costs per pound.
Drawbacks of Ethanol Extraction
- Because ethanol is a polar solvent, it tends to draw out more unwanted plant matter (including chlorophyll) than other solvents, especially when you opt for warm ethanol extraction.
- Ethanol recovers fewer cannabinoids than other solvents and extraction methods. On average, you can expect 50%-80% cannabinoid recovery. By comparison, butane hash oil (BHO), CO2, and solventless extraction can achieve around 90% cannabinoid recovery.
- Ethanol extraction is slower than hydrocarbon extraction, due in part to its extremely high boiling point (173°F).
- As with hydrocarbons, ethanol is flammable and must be treated with caution.
Supercritical CO2 Extraction
Supercritical carbon dioxide is another solvent that has gained popularity in recent years. Granted it’s not the only CO2 extraction method, as you can also use liquid and subcritical CO2 to extract cannabinoids and terpenes. It is, however, the most common and most efficient way to use carbon dioxide in the cannabis extraction process.
The extraction process is similar to the hydrocarbon method, but the solvent (carbon dioxide) must be tightly controlled with precise temperature and pressure levels so that it remains in a supercritical state. In this state, the solvent is held at or above its critical pressure and temperature so that it behaves less like a gas and more like a liquid solvent. Carbon dioxide reaches its supercritical state at 1071 psi and 87.8°F (31.1°C).
In a supercritical CO2 extraction:
- Cannabis is ground up and placed into an extraction vessel.
The solvent is exposed to pressure and heat so that it reaches a supercritical state.
- A pump pushes the supercritical CO2 into the extraction vessel where it passes over the cannabis plant matter, breaking up the trichomes and dissolving the plant material.
- A pressure release valve helps to transfer the resulting crude oil into a separate collection vessel.
- The pressure, temperature, and flow rate are adjusted to separate the CO2 from the extract and route it away from the collection vessel. The CO2 may be purged or routed into a separate tank for later reuse.
Once the initial CO2 extraction is complete, winterization is almost always required for post-processing.
Benefits of CO2 Extraction
- CO2 is considered a uniquely eco-friendly extraction method, as the same solvent can be reused again and again.
- Because CO2 is a natural cleaning agent, it automatically destroys microbial bacteria during the extraction process.
- Residual solvent isn’t as much of a concern, as CO2 returns to its gas form at room temperature and ultimately evaporates.
Drawbacks of CO2 Extraction
- CO2 extraction systems are among the costliest in the cannabis industry. A good CO2 extraction lab can easily run you seven figures. The operational costs are also exceedingly high.
- Since CO2 solvents almost always need to be winterized, you inevitably have to add other solvents (like ethanol) into the mix.
- Supercritical CO2 extraction is extremely complex and should never be undertaken by an amateur extraction tech.
Solventless extraction is another method that has gained massive popularity in recent years, not only among extraction techs but also among consumers. Solventless extraction requires no liquids and no dissolution. The resin is extracted using only heat and pressure—as well as ice and water if you’re making hash rosin.
While it’s possible to carry out this method using a hair straightener or T-shirt press, professionals will typically use a machine called a rosin press. The resulting extract is known as rosin.
Solventless extraction with a rosin press generally looks something like this:
- The cannabis starting material (usually flower, sift, or hash) is inserted into filter bags or rosin wraps and placed between two stainless-steel or (preferably) aluminum plates.
- The plates are heated at a temperature that generally ranges between 130°F and 220°F. Cold pressing typically results in a budder- or batter-like consistency while warm pressing generally gives you more of an oily or shatter-like consistency.
- The plates are pushed together with several tons of force, causing the heated resin to squeeze out from the sides, where it’s collected onto parchment paper.
The rosin is collected.
Post-processing generally isn’t required for rosin, but some extractors may choose to cure the extract or subject it to additional processing in order to achieve a desired result.
Benefits of Solventless Extraction
- Solventless extraction equipment is the most cost-effective type of extraction machinery available. There are fewer regulatory requirements, and you can sometimes get up and running with just a rosin press and some basic hash-washing equipment.
- Because there are no solvents used, there are never any residual solvents that can compromise the quality of your batch or show up in a certificate of analysis.
- Solventless extracts can be sold at a premium because they’re a connoisseur-grade product, appealing to the most discerning consumers who want to avoid the use of chemicals in their vape products and dabs.
- Solventless extracts are easier to produce, and there are fewer safety risks since no flammable materials are being used. You don’t need an advanced chemistry degree to run the lab; it’s possible to build a smooth operation with just a bit of cannabis extraction training.
- By adjusting the temperature of the heated plates, you can achieve a variety of different textures (e.g. glassy, waxy, viscous, or oily) without the need for extensive post-processing.
Drawbacks of Solventless Extraction
- Solventless extraction requires a high-quality, trichome-rich starting material. You can’t input poor-quality cannabis and expect a high-quality extract (as you might with ethanol or hydrocarbon extraction).
- To achieve the highest-quality rosin, some pre-processing might be required—such as freezing fresh cannabis and transforming it into ice water hash prior to pressing.
- Rosin pressing doesn’t allow you to isolate individual cannabinoids, so it’s not a good choice for making broad-spectrum or isolate products (unless the starting material already has the cannabinoid profile you’re looking for).
Which Cannabis Extraction Method Is Best?
As you can see, there are serious pros and cons to each extraction method out there. Choosing the right one ultimately comes down to your needs as a processor.
Hydrocarbon is the traditional choice, and it still offers excellent throughput for all types of popular extracts. Ethanol may be ideal for processors who enjoy BHO extracts but are looking to cut costs, increase storage, and decrease their post-processing requirements (and who don’t mind the tradeoff of slightly slower output and reduced cannabinoid recovery). CO2 is great for processors who love the benefits of solvent extraction but are seeking a more eco-friendly solution.
And for those who want to avoid solvents entirely and create premium, connoisseur-grade extracts at a lower cost and with a higher ROI, solventless extraction is the way to go. It’s just one reason why so many seasoned extraction techs are introducing solventless equipment into their existing labs.