What is Hydrocarbon Extraction?
Hydrocarbon extraction is a method used to extract cannabinoids such as tetrahydrocannabinol (THC), cannabidiol (CBD), and terpenes from cannabis plant material. It has become a widely popular extraction method for cannabis refinement in recent years, due to its low cost, efficiency, and extraction quality, as compared to alternative methods.
The hydrocarbon extraction technique involves the use of certain hydrocarbons like propane and butane – these materials act as solvents, which, when combined with plant material, strip desired chemical compounds (such as cannabinoids) out of plant material. This isolate is then further refined through a number of other methods. Highly concentrated extracts can be used to create cannabis oils, shatter, glass, hash, wax, and other products – these extracts contain little to no hydrocarbon residue when the commercial extraction is performed properly.
What Are Hydrocarbons?
Hydrocarbons are a classification of organic compounds consisting of carbon and hydrogen. They are formed from the compression of animal and plant remains over long periods of time, and are pulled from porous rocks such as sandstone, limestone, and shale, where they pool and concentrate. The most common hydrocarbons include butane, propane, hexane.
In addition to being a common fuel source, some hydrocarbons are powerful organic solvents. Organic solvents are substances capable of dissolving or dispersing other substances – they most commonly used in natural food flavorings, soybean oil, vegetable oil, and many other food products which are consumed on a daily basis.
Butane vs. Propane
Butane is a popular solvent in the cannabis world. It’s a non-polar, Class 2 flammable liquefied gas), with a low boiling point ( 31.1°F). In cannabis extraction, this is important because it allows for the cold-boiling of any leftover solvent from the concentrate, which preserves temperature-sensitive terpenes. It’s often popular to blend butane with propane when extracting, to create a gas mixture that will strip additional terpenes and purge more efficiently than butane alone, since the boiling point of propane is so low (-43.6°F).
When used in isolation, propane extracts slightly different ratios of cannabinoids and waxes and can be purged easily without affecting the integrity of the terpenes. However, because propane exhibits different traits than butane when used as a solvent, it’s more common to find extraction equipment that relies on a blend of both butane and propane.
A Brief History of Cannabis Extraction
Extraction of cannabis is a relatively simple process that people have used for centuries. There are ancient historical records of people consuming cannabis extracted products like tea, hash or tinctures. Hash, cannabis resin, was first mentioned in records in the 12th century in Egypt and arrived in Europe in the 18th century. People traditionally ate hash; smoking did not become common until the 16th century.
The science behind cannabis extraction has greatly evolved since then. However, the reason people extract cannabis is simple and has remained unchanged even after centuries. The final product is much more potent than the fresh plant, and it contains more of the desired compounds. Therefore it is easier to know the dosage.
Hydrocarbons like propane and butane have been used since the 1970s for food extractions. Hydrocarbon extraction can produce a finished product with approximately 70-90% cannabinoids. Technologies used for extraction have acutely advanced as the demand for cannabis products quickly increases. Legalization of cannabis has catalyzed innovations in extraction methods. New solvents are sought after in order to achieve the highest quality products.
Cannabis concentrates are making huge gains in popularity, including oil. Cannabis oil is widely popular among cannabis users because it is convenient, consistent, and more concentrated. One of the fastest-growing subsets of concentrates is CBD oil. There is scientific evidence that CBD can reduce seizures in epilepsy patients and can reduce anxiety, inflammation, and chronic pain. It may also be useful in treating insomnia.
The Benefits of Hydrocarbon Extraction
Hydrocarbons are the most commonly used extraction solvents – and they provide the best results. In fact, hydrocarbon solvents have been safely used in the food-processing industry for more than 50 years.
The main advantage of hydrocarbon extraction is the large number of products you can create from a single extraction without any further refinement. And, while this is some concern over the use of hydrocarbons like butane or propane in the processing of products that are ingested, the U.S. Food and Drug Administration (FDA) recognizes butane and propane as safe ingredients, within certain limits. Some of the major advantages to using a hydrocarbon as your extraction solvent:
Efficiency & Throughput
Hydrocarbons have a cycle time of only 60 minutes, while supercritical CO₂ can range anywhere from 6 all the way up to 10 hours. Not only that – hydrocarbons are capable of operating at exceptionally low temperatures, which means greater preservation of the quality and unique characteristics of cannabis material.
While it’s common for hydrocarbon extraction equipment to utilize a blend of butane and propane (generally with a greater percentage of the former), it’s not a requirement that multiple hydrocarbons are used. Each solvent produces a different result, and these differences can be utilized to refine a large variety of end products.
Butane extraction can yield between 14% to 30% by weight. By comparison, CO2’s extraction yield will often top out around 8%. This means less wasted plant material.
Hydrocarbon extraction preserves the plant’s flavor, aroma, terpenes and flavonoids. Unwanted elements, like chlorophyll, are not extracted from the plant. Ethanol extraction can damage the plant’s flavor and aroma, thus requiring the product being masked with flavoring or scents.
Despite the belief that hydrocarbon extraction is in less safe, butane and propane extraction equipment operate at relatively low pressures (not exceeding 300 pounds per square inch). This makes them much safer for the operator and the equipment that other high-pressure techniques. Also, all major hydrocarbon solvents are regarded as generally safe to use by the FDA.
Properly maintained professional hydrocarbon extraction equipment has almost no risk, it’s simply a reality that when using a flammable solvent like butane, the entire processing laboratory should be in compliance.
A selection of equipment used when extracting using hydrocarbons
How The Hydrocarbon Extraction Process Works
The hydrocarbon extraction process is incredibly efficient and results in a high-quality end product. The main stages of this process are as follows:
Assess Quality of Plant Matter
When developing a cannabis distillate, it’s essential that the initial plant matter has been properly cared for. By avoiding exposure to degrading elements such as ultraviolet rays, heat, and oxygen, you’re ensuring that quality of the finished extraction product, regardless of extraction methodology. Base plant material should always be stored in an environment free from light or fluctuating temperatures, preferably in vacuum sealed (and nitrogen-filled) bags.
The first step in the extraction process, primary extraction involves flushing cold butane through the solvent tank into the material column. This is where the hydrocarbon washes over the base plant matter – dissolving the terpenes and cannabinoids into the solvent. Once the plant material has been washed, the solution can be directly captured, or it can be processed in any number of ways.
At this point in the process, a choice of further refinement depends entirely on the desired end product. This could mean using something like in-line de-waxing, where the initial extraction is passed through stainless steel beads or another filtering medium, in order to hold back undesired materials.
An alternative and popular refinement technique used in tandem with hydrocarbon extraction is winterization. Winterization uses a solvent such as ethanol at a high ratio to the base solvent. It is mixed with the extracted solution, and chilled to separate each element. This chilled solution then passes through a series of fine filters to separate out the waxes and lipids from the concentrated solution.
After refinement, the concentrate solution passes through to the collection pot, and any residual butane is passively removed. This purge moves the isolated butane back into the solvent tank, thus created a “closed-loop” system. This process repeats until the majority of the butane is removed from the solution –then the extraction collects the concentrate for further separation.
There are multiple techniques for purging final solvent levels from the extraction solution. The desired end product will usually dictate which method is chosen – for example, when making shatter, the collected concentrate is spread thinly to expose as much surface area as possible, and then it is placed in a vacuum oven over a lengthy period of time (36-48 hours). But, when making something like wax, the initial concentrate is whipped over time to excise any remaining butane.
Refinement & Post Processing of Hydrocarbon Extraction
After the hydrocarbon solvent has effectively isolated the desired plant material compounds, there are a number of compatible refinement techniques. Each of these methods results in a particular style of product, whether it’s shatter, live resin, CBD distillate, etc.
Centrifugal Terpene Removal: The process of separating terpenes from a primary extract using a centrifuge device.
Winterization: The process of removing plant lipids from a primary hydrocarbon extract via a secondary solvent, freezing, and filtration.
Decolorization/Carbon Scrubbing: The process of removing the dark color and undesirable components of a primary extract via various filtration media.
Dewax: The process of reducing and removing plant lipids via low-temperature single solvent isolation and filtration.
Vacuum Purge: The process of removing residual solvents via a low-pressure low heat oven cycling.
Decarboxylation: The process of removing the carbolic acid group from primary cannabinoids via heat.
Co-Solvent Separation: The process of isolating one or more cannabinoids via matching various solvents to cannabinoid polarity.
Co-Solvent Crystallization: The process of isolating cannabinoids via crystallization by matching various solvents to cannabinoid polarity.
Hydrocarbon Extraction Equipment With Precision
Hydrocarbon extraction is the preferred extraction method for the top cannabis processors in the world, and more cannabis and hemp extract awards have been won using Precision’s solvent-based extraction equipment than with any other brand.
The Best Cannabis Extraction Methods for Marijuana Concentrates
Extraction techniques are used to separate the components of cannabis and remove them from the plant matrix. Various methods can divide cannabis plant material into parts, or extracts, that contain different chemicals. With cannabis, extraction techniques are often used to isolate specific desirable compounds, and cannabis contains at least 113 cannabinoids, including cannabidiol (CBD) and tetrahydrocannabinol (THC). On the other hand, a producer may seek to create a single extract with many desirable cannabis compounds; sometimes called whole plant extracts. Including the better-known cannabinoids, scientists have identified more than 550 chemicals in cannabis in general including components like terpenes. Extraction techniques are also used to concentrate chemicals of interest.
This article goes over the most common methods of cannabis extraction. Before discussing these methods, readers should keep in mind that cannabis extraction is chemistry, not cooking. So, some skills in analytical methods plus real lab equipment is required to perform these methods correctly and safely. In many cases, the reagents and how they are used can create dangerous situations. Consequently, many of the techniques require safety equipment, like a fume hood. Just as important, the extraction process must be performed correctly to produce a safe product for human use, and the results should be confirmed independently with proper analytical testing.
Cannabis alcohol extraction
A cannabis tincture created using alcohol-based extraction.
This method can be performed at atmospheric pressure, but the temperature is carefully controlled, especially during evaporation. This process can also take time and must be done carefully to avoid danger as ethanol is highly inflammable. One of the biggest benefits of this form of extraction is that there is no risk of leaving toxic residual chemicals in the final cannabis extract and, it enables the co-extraction of all compounds of interest, chiefly cannabinoids and terpenoids.
Co2 cannabis extraction
Using a reagent of any kind can add cost and clean-up time, so various techniques should be considered, and one is CO2 extraction. Instead of using alcohol, this method removes cannabis components from the plant matrix with carbon dioxide. Here, though, high pressure and heat are used to turn the CO2 supercritical—meaning it is simultaneously like a liquid and a gas.
Cannabis CO2 extract being dispensed from a supercritical CO2 system following extraction. Credit: Eden Labs LLC.
The equipment cost for this method is orders of magnitude higher than alcohol extraction, but it 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—more likely a combination of these. Moreover, one study found that different compounds get concentrated at different rates in the same process. So, the extract should be analyzed, especially where concentrations of specific compounds are desired.
A selection of supercritical CO2 extraction equipment available from Eden Labs. Credit: Eden Labs LLC.
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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.
Despite the need for some financial investment in a CO2 extraction system, a manufacturer can consider various levels of equipment. For instance, Apeks Supercritical makes introductory through high-production extraction systems and even offers refurbished systems. This gives customers a range of prices to consider.
Cannabis butane or propane extraction
Using butane as the extraction solvent creates what is known as butane hash oil. To do this, the process starts with cannabis and liquid butane in a pressurized and heated system. By using evaporation under a vacuum, it is then possible to remove the butane solvent. The vacuum turns the butane from liquid to a vapor, making it easier to remove.
This kind of extract is also known as shatter, which is a clear material that typically includes THC, CBD and other chemical components, including terpenes. To really make shatter, which is a hard version of butane hash oil, terpene content must be kept low or it works like a solvent that makes the extract soft. The right starting sample can help to reduce the terpenes present in the final product, such as by starting with cured flowers. On the other hand, the butane hash oil can be heated to remove terpenes after extraction as they are more volatile than cannabinoids like THC and CBD.
Even without any added steps, this method 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. The removal process should reduce any residual butane in an extract. In all cases, though, analytical testing should be done to ensure butane’s removal, because it is highly toxic to humans.
That danger can make this method a less desirable choice, especially for medicinal products. Increasing analytical testing and tighter regulations on acceptable residual butane levels could limit this method for many applications—unless, the user takes special precautions to limit any residual butane in the product and uses third-party analytical testing to confirm the safety of an extract.
Nonetheless, butane extraction has been a popular method for extract producers and enthusiasts for years, largely due to the relatively low equipment and running cost. And, the fact that it produces flavorful extracts with higher terpene content than can be achieved by CO2 extraction, for example.
Instead of butane hash oil, some manufacturers opt to produce propane hash oil. In this method, liquid propane is used in the place of butane. Here, high pressure keeps the propane liquefied and extraction occurs at a lower temperature, because propane’s boiling point is less than butane’s.
The extraction temperature impacts the components removed from cannabis. So, these two similar methods—butane and propane extraction—produce dissimilar extracts. In some cases, butane and propane extraction can be used in combination to create a product with a broader chemical profile.
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.
It is worth mentioning that more basic techniques also exist for preparing cannabis and extracting desirable components from the plant matrix. Kief, for example, can be separated from cannabis buds simply by grinding and sieving. These crystalline formations make up part of structures known as trichromes which are found on many plants, including cannabis. Cannabis trichromes are primarily protective structures produced by female plants when flowering. Their intense bitter taste and strong aromas render the plant unpalatable to herbivores and, they are also believed to inhibit some fungal growth. When separated from cannabis inflorescence, kief looks just like a powder or pollen. And, as cannabinoids and terpenoid production is particularly concentrated in trichromes this powder can be added to cannabis preparations to boost potency or consumed alone as a standalone product.
Rosin has also become very popular over the last couple of years. Produced from flowers, hash or kief, rosin is a translucent substance typically with a sap-like consistency. It’s made by applying heat and pressure to the material you wish to extract from and results in a product that’s very similar to the more time-consuming, expensive and, solvent-based butane extraction. Analytical testing has demonstrated that this simple approach effectively extracts cannabinoids and terpenes with absolutely no risk of leaving behind toxic residual solvents like butane. The simplicity of this approach is without a doubt its biggest draw. Enthusiasts are able to produce highly potent rosin extracts with a hair straightener, some baking parchment, a collection tool and, some heatproof gloves. Commercial rosin presses are also available to process material on a much larger scale but the concept is essentially the same. A flat heat press mechanism is used to squeeze the material but at a specific heat and pressure and the extract is scraped off.