State-of-the-art post-harvest methodologies for the extraction of active compounds from cannabis

Published on 04/08/2022

Introduction

Cultivators is focused primarily on cannabis and lettuce cultivation and facility design. To better understand the post-harvest practices of extraction of cannabis compounds, the Cultivators worked with a team of students from Wageningen University and Research. For this research a literature review was conducted as well as interviewed current extraction operators and manufacturers from around the world.

The cannabis industry is growing rapidly as it becomes legal for recreational and medical use in new jurisdictions. The emergence of the extraction market has completely changed cannabis consumption in legal markets. For example, in Canada, the introduction of cannabis flower under legalization preceded the sales of extraction products due to evolving regulations. The introduction of extraction products changed the market so much, it was referred to as, “Cannabis 2.0”. There are opportunities and risks to consider as each market will have its own regulations and market-types. These opportunities and risks need to be balanced with the pros and cons of each extraction type. We focused on four of them: Supercritical CO₂, Ethanol, Hydrocarbon, and Solventless Extraction.

Multiple factors influence the extraction efficiency of active compounds, such as the starting plant material, the solvent and technique used, the time of extraction, pressure, temperature, both during and before the extraction; material to solvent ratio and agitation (Figure 1).

Keep in mind these findings are summarized from 15 interviews with different professionals in the industry so their testimonies might be biased towards their technique.

Figure 1: Extraction efficiency is influenced by many factors (Ubeed et al., 2022).

Supercritical CO₂

Supercritical CO₂ extraction uses the supercritical state of CO₂ (from 31 °C and high pressure) as a solvent to extract your compounds. Using different pressures can allow you to separate desired compounds like terpenoids and THC using fractionation. This method can be used to create either recreational or medicinal extracts. This method is especially good for making pharmaceutical-grade extracts. The most important factors for extraction efficiency are the pressure used and the temperature. A higher pressure leads to higher efficiency in general but leads to a less specific extraction, the same goes for temperature. The main advantages of supercritical CO2 are its precision of extraction, its lack of waste products, as the CO₂ can be reused, its safety because no flammable solvents are used, and it shows yields of cannabinoids of 82%. The main downsides are the cost of the system, the cost of scaling the system, and the drying and milling of cannabis as this can remove some of the terpenoids before the extraction if not handled properly. Furthermore, Isabelle Francois states that CO₂ could be a great extraction process once the market has finally stabilized and there is a general interest of the public and investors, otherwise the capital expenses and the uncertainty are too big.

Products: Lozenge, oral spray, edibles, drinks, pantry items (hot sauce, infused sugar), dabbing products, tinctures, vape pen, capsules/pills.

 

Figure 2: Schematic overview of a closed-loop Supercritical CO2 extraction system. Vági et al. (2019). 

Ethanol Extraction

Ethanol is a polar solvent, so it extracts many unwanted compounds that have to be removed through winterization. To avoid this, ethanol is often used at -20 to -40°C. The most important factors in ethanol extraction efficiency are the extraction time, extraction temperature, and size of the plant material. An extraction time of up to thirty minutes increases extraction efficiency, the plant material should be as small as possible for the highest extraction efficiency, and a temperature at around 21°C appears to be the most efficient temperature, but you will have to deal with waxes. The main advantages of ethanol extraction are its scalability for large businesses, ease of use, low cost of solvent, and lower upfront costs for medical products when compared to CO₂ extraction. The main disadvantages are the low specificity for the desired compounds, which requires working at really low temperatures or going through expensive winterization, the constrain on the range of products you can make, and the safety requirements (C1D2 room).

Products: Topical Creams, edibles, drinks, vape pens, tinctures, capsules/pills, liquids.

Figure 3 ethanol extraction process overview : Meri Harli, (2021) Cold Ethanol Extraction: How it Works

Hydrocarbon Extraction

Hydrocarbon extraction is used for recreational and medical products in North America. At present, there seems to be a consensus this will not be a viable path to market in Europe in the short and medium-term for recreational or medical products. The most important factor in hydrocarbon extraction is the mixture of hydrocarbons used, as this determines which compounds can be dissolved and thus what compounds are extracted. Its advantages are its wide variety of products, the ability to obtain full-spectrum products, purer than ethanol, and its scalability. Its disadvantages are difficulties with regulations and capital costs related to ensuring a safe work environment due to explosion and fire risks (C1D1 room).

Products: Dabbing Products (Budder, Badder, Wax, Caviar, Diamonds, Live resin, Shatter, Terp Sauce), vape pens and distillates.

Figure 4: End products of hydrocarbon extraction. From left to right: budder, wax, diamonds, vape pen oil, shatter, live resin.

Solventless Extraction

Solventless extraction is a technique where pressure and temperature are used to press different plant materials into a full-spectrum extract. The quality of the final product depends a great deal on the quality of the product you put into your process. For the extraction efficiency the most important factor is the product you put into the press. Kief yields a lot more extract than normal flower. Major advantages are its low up-front capital costs, its safety, and the high demand by recreational users in North America for high-quality, more “natural” products. Its downsides are maintaining quality at scale and its efficiency in terms of the percentage of cannabinoids removed from the cannabis flower. Furthermore, it is not possible to extract specific compounds.

Products: Fresh Frozen live Rosin, dabbing products (budder, badder, diamonds, shatter, etc.), vape pens, traditional hash extraction (Moroccan, Lebanese, Afghani), and edibles.

Figure 5 : Fuego, H. (2019). Strictly Solventless Dabs With Leiffa.

The Future of Extraction

Overall, in the long-term, we think this industry will likely look similar to the beer industry with many craft producers and a smaller number of large-scale producers due to consolidation. The smaller producers will likely continue to make high-quality solventless and hydrocarbon products for the recreational market and large-scale producers will likely focus on single ingredient compounds, example: THCV which are later added to products by themselves or mixed with other products. Then these different isolates are later placed into other products and formats by different companies that specialize in consumer-packaged goods and medical producers. We found examples of these large-scale extraction businesses existing already with all 4 extraction methods. Furthermore, we believe there is a chance that hydrocarbon products for recreational use will eventually be phased out. This is because solventless can result in many similar products for dabbing and vaping products, in a more natural way, and we think consumers will prefer this given the option.

Conclusion

There is uncertainty in this industry now due to the constant progression of technology and constant changing of regulations and legalization. The technological changes could well make one of these methods completely obsolete in ten years, but that remains to be seen. There is the potential for new jobs, tax revenue, and patient relief but this all must be balanced with operational safety, consumer safety, and investor caution.

Table 1. Various products and their applicability to various extraction methods. Green represents products that are commonly seen in legal markets already and were reported to be easily feasible for that method. Yellow represents products that are seen in the market but more difficult to produce with that method. Red represents products that are impossible to produce or very difficult to produce with that method. 

There’s certainly opportunity in this emerging market. What is the best one for you? Deciding what method to use is based on a number of factors such as: your location’s regulations, space available for operations, your budget, your target market and desired products for that market. Using table 1 can be helpful for matching your desired product type with extraction method. Table 2 can be useful for comparing the most important factors when choosing a technique.  If you are planning to work in Europe, it is safe assume that you should focus on CO₂, Solventless or Ethanol extraction until ambiguity around hydrocarbon extraction regulations are more clear. In Canada, all methods can be considered. In the USA, the rules vary state by state though all 4 methods are in use there in many states. There are many things to consider before moving forward into this space.

Table 2. Various extraction methods and important factors consider when deciding which extraction method to use. The € signifies increasing costs with increasing euro signs. These business assessments are subject to change as technology and markets evolve.

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