Closed-loop extraction is a method used for extraction of cannabinoids like tetrahydrocannabinol (THC), cannabidiol (CBD), and terpenes from cannabis plant material. This extraction method occurs entirely within a closed vessel, so the hydrocarbon solvent used to extract cannabinoids never makes contact with the outside atmosphere – hence the name “closed loop extractor.”
Closed-loop extraction is not new or unique to the cannabis industry. Industries also use this extraction method to extract essential oils for things like food additives and perfumes. However, in recent years, it has become a widely popular cannabis extraction method. Closed-loop extraction is efficient, produces a clean product, and industry professionals regard it as safer than open-loop, or “open blast”, extraction.
Solvents for Closed-Loop Extractors
Closed-loop extractors use hydrocarbons like butane as solvents to extract cannabinoids. Butane is the most popular solvent in the cannabis industry – It’s a non-polar hydrocarbon with a low boiling point ( 31.1°F), which allows for the cold-boiling of any residual solvent from the concentrate and preserves temperature-sensitive terpenes.
Extractors can also use propane. Propane can be purged easily because of its low boiling temperature and makes a slightly different extraction than butane. However, because propane is much more expensive than butane, it’s common to find closed-loop equipment that works on a blend of butane and propane. Blending butane with propane creates a gas mixture that strips additional terpenes and purges more efficiently than just butane alone.
In both open and closed-loop extraction, the initial process is the same. The pressurized solvent (usually butane) is washed over the cannabis plant matter, extracting the desired cannabinoids from the biomass material. In closed-loop extraction, the concentrate is then purged of all solvent in a separate vacuum oven, and then subsequently heated. In open-loop extraction, there is no purge, and some butane residue remains in the concentrate.
After the wash, and in closed-loop extraction, purge/heating, the concentrated oil can be collected and further refined.
History of Closed-Loop
Cannabis extraction is a relatively simple process that people have utilized for centuries. Historical documents describe people consuming cannabis extracted products like tea, hash, or tinctures. Records first mention hash in 12th century Egypt. People traditionally ingested hash until the 16th century, when smoking it gained popularity. Hash arrived in Europe in the 18th century.
The science behind cannabis extraction has dramatically evolved, but the reason people extract cannabis remains the same. Cannabis extraction provides a much more potent product and contains more of the desired compounds. Cannabis concentrates are making considerable gains in popularity, including oil. Cannabis oil is a favorite among cannabis users because it is convenient, consistent, and more concentrated. Extraction technology continues to advance as the demand for cannabis products increases, and the legalization of cannabis has spurred research and innovation.
The Essential Oils Industry Discovery of Closed-Loop Extractors
Essential oil industrial professionals have used closed-loop hydrocarbon extraction since the 1970s. The United States Food and Drug Administration (FDA) considers butane and propane as food-safe ingredients, within certain limits. Hydrocarbon extraction is a popular choice among cannabis industry professionals because it produces a finished product with approximately 90-99% cannabinoids. Hydrocarbon extraction also creates many quality concentrate products from a single extraction, without any further refinement. Thus, hydrocarbons are the most commonly used extraction solvents.
Many people initially used open-loop extraction methods for cannabis extraction. It wasn’t until recently that cannabis industry professionals adopted a closed-loop methodology to create cannabis concentrates. The development of closed-loop technologies represents a paradigm shift in the way both producers and consumers approach concentrates.
Advantages of Closed-Loop Extractors
The closed-loop method uses an extractor vessel that is completely closed to the outside atmosphere, so the hydrocarbon solvent used in extraction never comes in contact with the air. The solvent is looped through the system, washing over the cannabis plant material repeatedly. This repeated washing extracts as many cannabinoids as possible.
Cannabis industry professionals chose closed-loop extraction systems over open-loop because they are safer, more efficient, cost-effective, and more capable of producing higher quality products.
Cannabis industry professionals regard closed-loop extractors as one of the least dangerous ways to extract cannabinoids. Hydrocarbon solvents are flammable, pressurized gases. In a closed-loop system, there are no opportunities for leaks if the equipment is maintained and operated at the appropriate standards. A contained system is safe to operate and approved to OSHA standards.
Fully contained solvents in closed-loop extraction equipment provides a higher pressure capacity than open-loop extraction equipment. The greater the pressure, the more interface time is available between the hydrocarbon solvent and the cannabis plant material. High pressure allows for the maximum extraction of cannabinoids. Closed-loop systems are more capable of regulating temperature. It’s essential to be able to control the temperature because temperature directly controls the solubility of cannabinoids. Closed-loop extractors also prevent the solvent from being evaporated into the atmosphere and allows the solvent to be used many times without needing to be recharged.
As their name implies, closed-loop extraction systems are closed. Ideally, no hydrocarbon solvent leaks out into the atmosphere. Equipment operators can continuously reuse the solvent for extraction after extraction. A closed-loop extractor can provide huge savings on solvent purchasing costs for businesses.
Closed-loop systems offer unrivaled control on pressure and temperature in the system, which results in the ability to produce the strongest, purest cannabis concentrate available. The vacuum purge and heating remove most or all of the solvent’s residue, so many consumers also regard the by-products as the safest to consume.
Breaking Down The Process
The main steps of the closed-loop extraction process are as follows:
- Quality plant material: Cannabis plant quality directly affects the quality of the finished concentrate, regardless of which extraction method is used. Plant material should be stored in vacuum-sealed bags in a cool, dark place. Proper storage limits exposure to ultraviolet rays, heat, and oxygen, which all degrade cannabinoids.
- Primary extraction: Cold, pressurized hydrocarbon solvent moves from the solvent tank into the material column, where it washes over the cannabis plant material. The closed-loop system recycles the solvent, so it washes over the cannabis many times repeatedly. This washing dissolves the cannabinoids and terpenes from the cannabis plant material.
- Refinement of the concentrate: After the wash, the concentrate can be further refined. Which refinement technique you will use will depend on the desired end product. Some common refinement techniques include in-line dewaxing and winterization.
- Solvent purge and concentrate collection: The concentrate is then purged of all hydrocarbon solvent as the solvent is pushed back into the solvent tank. Purge methods and durations vary depending on what is the goal of the finished product. For example, to create shatter, the concentrate is then put into a vacuum oven for two days, to purge all remaining solvent with low heat slowly. Once the purge is complete, the system operator collects the concentrate.