August 20, 2019

Cannabis Oil Extraction Machines [The Ultimate Guide]

There has been an explosion in research and interest in the use of cannabis extracts. These extracts are appearing in everything from health supplements to beauty products to lotions. They’re everywhere! It’s easy for the consumer to get confused and feel overwhelmed with the range of products that are available to them.

What is Cannabis Oil?

Cannabis oil is essentially the extract from the Cannabis plant. If unprocessed, then it contains over 100 different cannabinoids from the plant. In fact, ongoing research has identified anywhere from 104 to 111 different ones. Furthermore, the two most relevant and valuable cannabinoids are: cannabidiol (CBD) and tetrahydrocannabinol (THC).

It’s also important to remember that cannabinoids are highly lipophillic. This means that they are not water soluble and are chemically “attracted” to lipids (the technical term for fats and waxes). 

In addition to these various cannabinoids, high-quality cannabis oil will also have high levels of  terpenes. These are a diverse group of hydrocarbons (chemical compounds that are long chains of carbon and hydrogen atoms) that are produced by a variety of plants. Colloquially, they are also known as essential oils. 

The most notable terpenes are: 

  1. Beta-Caryophyllene 
  2. Alpha-Pinene
  3. Myrcene

The cannabinoids and terpenes are the most desirable parts of the cannabis oil. This is because the cannabinoids are the active compounds that have medicinal and recreational properties while the terpenes effectively potentiate the physiological activity of the cannabinoids. This is commonly known as the entourage effect. 

What Are the Different Types of Cannabis Oil Extraction?

In order to properly extract this cannabis oil, you will have to employ the use of a cannabis oil extraction machine. This will make the process safer, more efficient, and faster, especially if you are looking to extract commercial quantities of cannabis oil. 

Consequently, there are 3 primary types of cannabis oil extraction:

  1. Hydrocarbon extraction
  2. Carbon dioxide (CO2) extraction
  3. Ethanol extraction

Each of these methods have their respective pros and cons. Furthermore, each method has the corresponding machinery in order to properly execute the cannabis extraction. It is crucial to remember that the needs of the manufacturer will govern the type of extraction machine used. For example, the essential parameters to consider when choosing a type of extraction machine include:

  1. Safety profile. 
  2. Yield output.
  3. Type of solvent used. 
  4. Extraction time
  5. Rate of efficiency and return on investment (ROI) 
  6. Amount of post-processing required

Let’s start with hydrocarbon extraction. So what exactly is a hydrocarbon? In organic chemistry, a hydrocarbon is a chemical compound that is composed of hydrogen and carbon in various chemical configurations and ratios, usually arranged in a long chain. These are the chief components that you find in natural gas and petroleum.

What Is Hydrocarbon Cannabis Extraction?

This is an especially popular system; one of the oldest forms of cannabis oil injection is, in fact, butane injection. In this system of extraction, hydrocarbons are used as a solvent to extract the cannabinoids and terpenes necessary for the manufacture of high-quality cannabis oil. For the purposes of cannabis extraction, there are 3 primary types of hydrocarbons used:

  1. Butane – This hydrocarbon has the chemical formula C4H10. The primary structural isomer that is used in this process is n-butane. 
  2. Methane – This is the simplest hydrocarbon and is the principal component of natural gas. It has the chemical formula CH4.
  3. Propane – This is a byproduct of natural gas processing and petroleum refining. It has the chemical formula C3H8.

All three of these are known as alkanes, and they are all gases at room temperature and standard pressure. However, they can easily be liquefied for the purposes of cannabis extraction by applying pressure. Additionally, they are nonpolar and have light boiling points. Consequently, these various hydrocarbons (and butane especially) can easily pull the desirable elements out of the plant material while leaving chlorophyll behind. 

A typical hydrocarbon closed loop extraction machine will have several major components, including: 

  1. Recovery cylinder – This houses the hydrocarbon solvent. 
  2. Material column – This is a large container that contains the plant material (also known as the biomass). It is connected to the recovery cylinder, whereby the hydrocarbon solvent is piped from the top down into the material column. As the solvent travels down and comes into contact with the plant material, it will extract the cannabinoids and terpenes for the final cannabis oil product. 
  3. Collection vessel – The solvent and cannabis oil is piped over from the material column  and gathers in the collection vessel. 
  4. Warm water bath – Below the collection vessel is a scissor lift that is propelled upward pneumatically in order to submerge it in a warm water bath. The water is usually heated by a Class 1/Division 1 immersion heater in order to provide optimal heating conditions to preserve the terpenes in the cannabis oil product. As the solvent is vaporized out, the cannabis oil remains at the bottom of the collection vessel and is harvested at the end of the overall process. 
  5. Molecular sieve – The solvent is vaporized by the warm water bath and flows over the molecular sieve, thereby removing any residual moisture. 
  6. Condensing coil – A pneumatic pump drives the process and pushes the vaporized solvent into the condensing coil which is submerged in an ice bath. This effectively re-liquefies the solvent so that it can be returned back to the recovery cylinder. 

Using the condensing oil to return the solvent back into the closed loop extraction cycle is simply a cost-effective measure to protect the return on investment (ROI). 

What Are The Pros and Cons of Hydrocarbon Extraction?

As with any other form of cannabis extraction, using hydrocarbons as the solvent does have its fair share of pros, including: 

  1. The actual extraction equipment is less expensive than CO2 extraction gear. However, safety precautions largely negate this benefit (see below). 
  2. The extraction rates are fast; when compared to CO2 extraction, this is where hydrocarbon extraction machines really shine. 
  3. The resulting cannabis product tends to be highly potent and is actively sought out by cannabis enthusiasts and connoisseurs. This includes final products used for dabbing, like shatter, crumble, or honeycomb.

However, hydrocarbon has major drawbacks as well. The most notable one is that every hydrocarbon is extremely flammable and combustible. This makes hydrocarbon extraction potentially very dangerous and requires any extraction equipment to be housed entirely in a Class 1, Division 1 (C1D1) facility. This can be prohibitively expensive; even the least expensive option for creating a C1D1 room to house and operate the hydrocarbon extraction equipment consists of repurposing an old shipping container and converting it. This high initial cost does not even include the various pieces of machinery and necessary components. 

Other potential cons to hydrocarbon extraction include: 

  1. Due to the C1D1 requirement (by law), automation is expensive and difficult to implement. 
  2. The use of highly flammable and combustible hydrocarbons means that local laws limit their use and the entire facility will be regularly scrutinized by inspectors and regulators. 
  3. The extraction machinery is not highly customizable or tunable. 
  4. Extraction efficiency and yield is not easily scalable due to limitations on the amount of hydrocarbons that can be on site at any given time. Remember, your C1D1 site will be closely and regularly examined by safety regulators. 
  5. Hydrocarbon extraction can result in final products that have undesirable levels of residual solvent. Consequently, all final products must be tested and the parts per million (also known as PPM) established through extensive testing. 

As you can see, although butane injection was, for many years, the industry standard, it has since been supplanted by other, less dangerous and more efficient methods and machines.

What Is Supercritical Versus Subcritical?

Before we dive into CO2 extraction, let’s quickly examine its chemical properties. CO2 is usually a gas at standard temperature and atmospheric conditions; for example, it surrounds us at all times in the air that we breathe. In order for it to act as a solvent in cannabis extraction, it has to enter either a subcritical or supercritical phase. In essence, you are compressing and heating the CO2 gas, with the subcritical phase occurring at the lower end of the spectrum, in order to liquefy it.

  1. Supercritical state – This refers to a chemical state when the CO2 is at or above its critical pressure and critical temperature. Essentially, this means that the CO2 is between its liquid and gas state and takes on chemical properties of both these states. That means that it can both effuse through solids like a gas and dissolve materials like a liquid. In order for the CO2 to be considered supercritical, the pressure must be above 1083 pounds per square inch (psi) and 88 F / 31 C. 
  2. Subcritical state – If the temperature drops to below 88 F / 31 C, then the CO2 becomes a liquid and is referred to as subcritical. It can still act effectively as a solvent, but it becomes considerably less powerful than supercritical CO2. Subcritical CO2 is also quite cold, thereby making it effective for the extraction of temperature-sensitive oils and terpenes. This makes it ideal for extracting and preserving the lighter oils from the plant material.  

Furthermore, if the pressure of the CO2 drops to below 600 psi, then it will become a gas and no longer effectively function as a solvent. This means that subcritical CO2 has much lower solvency power, thereby pulling only lighter oils and leaving most resins, waxes, paraffin, and lipids behind. On the other hand, supercritical extractions at very high temperatures (above 120 F / 49 C) or pressures (above 5000 psi) will likely cause thermal degradation to the oils. It will also likely result in the unwanted extraction of chlorophyll from the plant material. In other words, the solvency of CO2 can be increased or decreased based on the amount of pressure being applied in the system.

What is Carbon Dioxide (CO2) Extraction?

This brings us to carbon dioxide (CO2) extraction. Now, a major drawback to CO2 extraction, at least when compared to hydrocarbon or ethanol extraction, is that it is a very weak solvent. This means that it is not terribly effective at actually extracting the terpenes and cannabinoids. Consequently, CO2 extraction machines require a great deal of power and pressure in order to forcefully extract the cannabis oil – in fact, most machines operate anywhere between 1500 and 5000 psi. 

This is also why CO2 extraction machines have such long cycle times, with the shortest cycle usually being somewhere around 2 hours (assuming that the system is working in a higher pressure range). Of course, if you are working at such high pressures, there are fundamental safety concerns regarding the structural integrity of the equipment. 

CO2 extraction systems usually have three primary components: 

  1. Extraction vessel – This is filled with the plant material (also known as biomass or trim).  
  2. Accumulator – This is charged with supercritical carbon dioxide and then pumped into the extraction vessel. 
  3. Separator – The mixture of supercritical carbon dioxide and cannabis material flows into the separator due to the fact that it has a lower pressure than the extraction vessel. Furthermore, because the CO2 is less dense than the cannabis oil, they naturally separate in this lower pressure environment. 

This CO2 can be recycled back into the system and used for the next cycle. Reusing solvent allows for a more cost-effective extraction system to operate and an improved ROI.

What Are The Pros and Cons of CO2 Extraction Machines?

The machines used for CO2 extraction have their respective benefits, including: 

  1. They are tunable and customizable for varying molecular weights. 
  2. There are no residual solvents in the final product (this means that the resulting cannabis oil is especially suited for vape pens). 
  3. Machines that use cold extractions and/or separations are well suited to temperature-sensitive extractions, like easily preserving terpenes. 
  4. The safety requirements and costs are minimal for the facility where the extraction machines are housed and operated.

Furthermore, the high tunability and customization of CO2 extraction machines means that they can effectively do fractional extractions. This just means that the user can first extract at lower temperatures and pressures to remove lighter, volatile oils (remember that these are more susceptible to thermal degradation). The parameters may then be changed so that the remaining parts of plant material can be extracted at higher temperature or pressure. This approach is considered to be better than fractional separation. This is when extractions are done at high temperatures and then multiple separators have differing, cascading levels of pressure. This also means that the cannabinoids and terpenes are never exposed to high heat.

However, these extraction machines also have their share of drawbacks, including: 

  1. CO2 extraction machines are especially expensive, with most startup costs being at least several hundred thousand dollars. 
  2. It is difficult and complex to learn how to operate manual systems; any operator will have to have an advanced understanding of the process and mechanics. 
  3. Extraction rates and yield are low on less expensive equipment; all CO2 extraction machines have a fundamental issue with scalability. Furthermore, to increase output and yield, it requires a disproportionate level of investment, thereby eating into the profit margins of the company in question. For example, a standard CO2 extraction machine operating at an extraction time of 4 to 8 hours (with proportionately higher pressure) will only have 60 to 70% efficiency. 
  4. These extraction systems operate at extremely high pressures (over 2000 psi, frequently), thereby putting an inordinate amount of wear and tear on the mechanical components. Consequently, the pump usually has to be rebuilt every 4 to 6 months. 

In other words, CO2 extraction machines are extremely safe, but they are slow, expensive, and not easy to make profitable. Hydrocarbon injection, on the other hand, is efficient but dangerous. 
Furthermore, CO2 extraction has always been pitched as an extraction method that does not use a solvent, which is emphatically not true. Solvent (in the form of ethanol) is required during the process of winterization, whereby the raw extract is further distilled down to only the desirable elements (terpenes and cannabinoids).

What Is Winterization?

Winterization is a specific process designed to remove the undesirable elements that were extracted from the cannabis plant material. This includes fats, lipids, and waxes.  

In other words, this extracted oil is like crude petroleum and needs to be further refined. To effectively perform winterization, the extracted oil is mixed with pure 200 proof (100%) ethanol and agitated vigorously until uniformly mixed. This is then placed in a deep freezer for 12 to 24 hours (remember that the ethanol will not freeze). 

Once removed from the deep freezer, the extracted oil/ethanol mixture will appear cloudy. You can either use a paper filter or a Buchner funnel to filter out the undesirable elements as you pour the mixture into an extraction jar. Now that you have filtered out the waxes, lipids, and fats, you are left with cannabis oil (terpenes and cannabinoids) and the ethanol solvent. 

Remember, you only want the cannabis oil, so you have to get rid of that ethanol solvent. This can be done with the gentle application of heat. By gently warming the oil plus ethanol, you can evaporate the ethanol off without causing thermal degradation to the cannabis oil. This is because the boiling point of the ethanol is considerably lower than that of the cannabis oil. 

You can also use centrifugal force; a piece of machinery known as a centrifugal evaporator or rotary evaporator (known colloquially as a roto-vap) can be used to gently evaporate the solvent without any damage to the cannabis oil. Finally, this ethanol can be reused (by collecting and condensing the vapors) in order to improve ROI.

What is Ethanol Cannabis Extraction?

It is also possible to use ethanol as the primary solvent (not just in the final step of winterization). This third type of cannabis extraction is ethanol extraction. There is a sizable contingent in the cannabis extraction industry that considers ethanol extraction to have the best properties of hydrocarbon (high efficiency) and CO2 (safety). In fact, the development of ethanol extraction machines shows the most promise in delivering a high-quality cannabis oil with safe and efficient equipment. 

However, it is crucial to remember that ethanol is an “abrasive” solvent. What does this mean, exactly? Room-temperature ethanol will extract just about everything from the plant material: terpenes, cannabinoids, lipids, fats, and even chlorophyll. In fact, it will basically strip the cannabis material down to everything but the cellulose fibers. This is because of the chemical properties of this solvent, specifically the dual polarity of ethanol. In fact, old-school methods of ethanol extraction frequently ran into this problem: the solvent was pulling everything out of the plant material. 

So how do you selectively extract the desirable elements (like terpenes and cannabinoids) while leaving the rest (chlorophyll, waxes, lipids) behind? 

The answer lies in the temperature of the ethanol. Supercooled, or cryogenic ethanol, is highly effective at selectively pulling out only the desirable parts of the plant material. By using it at such a low temperature, the polarity of the ethanol is being effectively manipulated so that it effectively acts as a nonpolar solvent. This is why newer machines that use supercooled ethanol have the same high level of efficiency as hydrocarbon extraction machines. In fact, supercooled ethanol is so efficient as a solvent that the extraction machines are designed to combine the ethanol and plant material only briefly. In the context of the extraction machine, the process of pouring the ethanol over the plant material is known as the wash. With supercooled ethanol, the short wash times ensure that only the desirable elements are extracted.  

Furthermore, supercooled or cryogenic ethanol extraction machines operate under negative pressure. To boil it down in the simplest terms, the two types of pressure are: 

  1. Positive – Where forces are pushing (measured in psi).
  2. Negative – Where forces are pulling (measured in inches of Mercury, or inHg).

By using negative pressure, the various parts of the ethanol extraction machine can use pressure differentials to effectively move solvent and plant material between the three primary components: 

  1. Solvent storage (supercooled or cryogenic ethanol)
  2. Holding tank
  3. Extraction vessel

In order to properly filter out plant material so that it does not gum up the works, most ethanol extraction machines will have a series of sock filters installed between the various primary components. These can range anywhere from ultra-fine to coarse, depending on the consistency of the plant material that is being exposed to the solvent. 

Furthermore, using negative pressure makes the entire system exceptionally safe and the use of motors unnecessary. Instead, the pressure differentials are driven by pneumatic actuators rather than mechanical pumps. Furthermore, these supercooled ethanol extraction machines do not need to common post-processing techniques, including: 

  1. Winterization. The plant material is only momentarily exposed to the cold ethanol before it passes quickly through and only pulls out the desirable elements (terpenes and cannabinoids).
  2. Filtration. The cold ethanol does not pull out any chlorophyll or lipids. 

So what does all this mean? Well, the industry has seen a sea change in the types of machines used, with the most processing being ethanol extraction machines that use supercooled solvent. This is because the high solvency of supercooled ethanol makes it efficient like hydrocarbon extraction and the negative pressure of the machines makes it safe like CO2 extraction machines. Supercooled ethanol extraction machines effectively combine the best parts of hydrocarbon and CO2 extraction machines. They can also be easily automated and operated by entry-level technicians. 

Furthermore, as the market evolves and more states legalize cannabis, the efficiency of systems will become increasingly important. Remember that the process of expanding the industry will increase competition and make profit margins much narrower. Consequently, supercooled ethanol extraction machines are the most promising for the future of the industry.

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