The Best Cannabis Extraction Methods for Marijuana Concentrates

There is a broad portfolio of cannabis extracts and concentrates which support a wide range of products and uses. Below we take a dive into the various types of cannabis concentrates and the extraction techniques involved in production -- offering insight regarding benefits and costs associated with each process.

What are the benefits of cannabis concentrates?

Concentrates are enriched preparations which may contain a mixed population of cannabinoids, terpenes, flavinoids, and other compounds. The concentrations of these components are related, not only to the plant strain, but to the methods and techniques used in the extraction process. The term “enriched” means these components are present in much higher concentrations over raw plant material such as cannabis flower. Moreover, these preparations can be amenable for a wider spectrum of formulations including topical analgesics, edibles, and other products. The chemicals involved in a given extraction, and the residuals carried over into the concentrates, can have serious implications on a given application or product. For these reasons and more, it is important to understand the different extraction processes and realize the preferred applications and safety risks associated with each technique.

Cannabis extraction methods – products – considerations

Solvents are a preferred method for extraction of volatile aromatic and aliphatic compounds from complex backgrounds -- i.e. cannabinoids and terpenes from the rich plant-based milieu in milled cannabis material. As with many chemical processes, the extraction yield and quality depend heavily on the consistency and quality of the input material. This speaks to requirement for high-performance equipment at the harvesting, grinding, and milling stages of cannabis processing.

Butane extraction

Butane solvent extraction results in the formation of butane hash oil (BHO) which can be further processed into shatter and other formulations. Extraction steps are as follows:

• Cannabis material is first heated and incubated with liquified butane in a closed-loop system under increased pressure.
• After passing through the bed of cannabis material, the solvent is removed through evaporation under a vacuum.
• Similar to other liquid extractions, dropping the pressure below the boiling point causes the conversion of butane from liquid to vapor, facilitating the removal process.
• Extreme care must be taken as butane is highly flammable and pressurization is involved.
• Low temperatures must be strictly controlled to maintain butane in liquified form during the extraction.
• Heating circulators facilitate removal and recycling of gas phase butane following extraction.
• The presence of residual solvent can be dangerous to human health and therefore, depending on the application, certified analytical testing labs are often required to quantify residuals.
• The rather crude concentrates and the potential for residual solvents can limit the use of this technique and extract for medicinal purposes.
• Butane extraction is popular and requires a capital investment on the low end of the spectrum – however, limitations for medicinal use and residual solvent lab testing costs may complicate the expense of the technique. This is especially relevant as new production and testing guidelines continue to emerge, bringing with them stringent parameters for residual solvent content.

Propane extraction

Liquid propane can be used in a similar extraction approach to generate propane hash oil (PHO), which has slightly different consistency and composition compared with BHO.

• Higher pressure treatment is required to maintain propane in liquified form during extraction.
• The lower boiling point of propane equates to a lower temperature for solvent removal, and subsequently leads to a different chemical profile compared to BHO.
• Since these extraction techniques result in distinct ratios of cannabis compounds, butane and propane methods should not be used interchangeably for a given application.
• A combination method which includes both butane and propane can be used to produce a hybrid extract with unique properties.
• Similar safety and testing considerations are required for propane as for butane extraction.

Alcohol extraction

An alternative the hydrocarbon methods described above, isopropanol or ethanol can be used to extract cannabis compounds under atmospheric conditions without the need for increased pressure.

• Liquid alcohol removal requires precise temperature control and is typically time intensive compared with other solvent evaporation techniques.
• A benefit over hydrocarbons is the absence of significant health threats from residuals, not to mention the improved safety factor – although caution should still be taken as alcohol is flammable.
• Excess time and reagent usage, in additional to traditionally lower yields, can equate to sizable cost differences compared to other modern approaches such as super critical CO2 extraction described below.

Carbon dioxide extraction

The approaches described thus far have certain drawbacks that can contribute to practical limitations. The environmental impact and the costs associated with reagent disposal can severely impact an extraction lab’s budget. Although the processes and reagents are rather simple to run and inexpensive to acquire, disposal, suboptimal yields, the impact of residuals, and the expenses of testing can more than make up for upfront cost savings. Supercritical CO2 extraction can minimize the environmental costs (and impact) while boosting yields and safety profiles. This however, can come with higher upfront costs, especially at the large-scale processing level.

• CO2 extraction is based on a similar liquid extraction premise as described above, a major difference is more extreme pressures are required for supercritical CO2 formation and stability.
• A typical system uses a compressor downstream of a liquid CO2 pressurized vessel which brings the pressure 75 psi or greater.
• A heating apparatus increases the liquid CO2 past a certain point at which time the CO2 adopts the supercritical state – possessing qualities of both a gas and a liquid.
• The supercritical fluid has expansive gas-like properties but maintains the elevated density of a liquid.
• The extraction activity of the fluid has a gentler effect on the cannabis material, resulting in higher yields and less target compound losses compared with other extractions.
• Another benefit is that the extraction process can be finely “tuned” to adjust the selective extraction of certain cannabis compounds by varying the conditions (pressure, temperature, time).
• Following collection of extracted compounds, the supercritical CO2 is directed into a condenser which converts it back into a stable fluid – at which time it can be filtered and reused.
• An obvious difference with this approach is very little waste is produced with virtually no reagent consumption.
• Therefore, the technique is cost effective from both waste disposal as well as environmental impact perspectives.

Any residual CO2 that remains in the extract readily evaporates under atmospheric conditions in a safe and environmentally friendly manner – an critically important benefit of this extraction method for medicinal cannabis preparations.

Read more about cannabis extract refinement and processing of concentrates in a subsequent article: Downstream Processing and Refinement of Cannabis Concentrates

Be sure to peruse our growing resource library of cannabis related articles for further information and insight.

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