Advanced Post-Harvest Methods for Extracting Active Compounds from Cannabis

Published on 04/08/2022

Introduction

Cultivators primarily focus on cannabis and lettuce cultivation and facility design. To better understand post-harvest practices for extracting cannabis compounds, Cultivators collaborated with students from Wageningen University and Research. They conducted a literature review and interviewed current extraction operators and manufacturers worldwide.

The cannabis industry is expanding rapidly as it becomes legal for recreational and medical use in new jurisdictions. The emergence of the extraction market has completely transformed cannabis consumption in legal markets. For example, in Canada, the legalisation of cannabis flower came before the sales of extraction products due to changing regulations.

The introduction of extraction products shifted the market significantly, earning the term “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 must be weighed against the advantages and disadvantages of each extraction method. We focused on four of them: Supercritical CO2, Ethanol, Hydrocarbon, and Solventless Extraction.

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

Keep in mind that we based these findings on 15 interviews with different industry professionals, whose testimonies may reflect bias toward their own techniques.

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

Supercritical CO₂

Supercritical CO₂ extraction utilises the supercritical state of CO2 (at temperatures above 31 °C and high pressure) as a solvent to extract compounds. Using different pressures can allow you to separate desired compounds, such as terpenoids and THC, through fractionation. This method can be used to create either recreational or medicinal extracts. This method is perfect for making pharmaceutical-grade extracts. The most critical factors for extraction efficiency are the pressure used and the temperature. A higher pressure generally leads to higher efficiency, but it also results in less specific extraction.

The same applies to 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 yields cannabinoids at 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 appropriately handled. Furthermore, Isabelle Francois states that CO₂ could be a great extraction process once the market has finally stabilised and there is a general interest of the public and investors; otherwise, the capital expenses and the uncertainty are too big.

Products: Lozenges, oral sprays, edibles, drinks, pantry items (hot sauce, infused sugar), dabbing products, tinctures, vape pens, 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 must be removed through winterisation. 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 of 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 solvent cost, and lower upfront costs for medical products compared to CO₂ extraction. The main disadvantages are the low specificity for the desired compounds, which requires working at extremely low temperatures or undergoing expensive winterisation, the constraint on the range of products that can be made, 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

Producers in North America use hydrocarbon extraction to create both recreational and medical cannabis products. However, industry experts currently agree that this method won’t offer a viable path to market in Europe in the short to medium term for either product category.Operators play a critical role in the process by selecting the type of hydrocarbon mixture, which determines which compounds dissolve and, ultimately, which ones they extract.

This method offers advantages such as a broad product range, the ability to produce full-spectrum extracts that are purer than those made with ethanol, and strong scalability. On the downside, it presents regulatory challenges and requires significant capital investment to ensure workplace safety due to explosion and fire risks, which demand C1D1-rated facilities.

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: butter, wax, diamonds, vape pen oil, shatter, live resin.

Solventless Extraction

Solventless extraction is a technique that utilises pressure and temperature to press different plant materials into a full-spectrum extract. The quality of the final product depends significantly on the quality of the materials you put into your process. For the extraction efficiency, the most important factor is the product you put into the press. Kief yields significantly more extract than regular flower. Significant 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 believe this industry will likely resemble the beer industry, characterised by a large number of craft producers and a smaller number of large-scale producers resulting from consolidation. The smaller producers are likely to continue producing high-quality solventless and hydrocarbon products for the recreational market.

In contrast, large-scale producers will likely target single-ingredient compounds like THCV, which they can add to products individually or blend with other ingredients. Companies that specialize in consumer-packaged goods and medical products then incorporate these isolates into various product formats. We identified several large-scale extraction businesses already operating and using all four major extraction methods.

Additionally, we anticipate that the industry may eventually phase out hydrocarbon-based products for recreational use. Solventless methods can produce similar products for dabbing and vaping, but in a more natural form—and we believe consumers will choose these options when given the opportunity.

Conclusion

The constant evolution of technology and the frequent shifts in regulations and legislation now create uncertainty in the industry. Advancing technology could render one of the current methods completely obsolete within the next ten years, although that remains uncertain. The industry holds potential to generate new jobs, increase tax revenue, and provide patient relief. However, stakeholders must balance these opportunities with operational safety, consumer protection, and investor caution.

Table 1. We categorized various products based on their compatibility with different extraction methods. Green indicates products commonly found in legal markets and easily produced with that method. Yellow shows products currently available but more difficult to make. Red marks products that are very challenging or nearly impossible to manufacture using that method.

There’s certainly an opportunity in this emerging market. What is the best one for you? Deciding on the method to use is based on several factors, including your location’s regulations, the available space for operations, your budget, your target market, and the desired products for that market. Using Table 1 can help match your desired product type with the appropriate extraction method. Table 2 can help compare the most important factors when choosing a technique.

If you plan to work in Europe, focus on CO₂, solventless, or ethanol extraction, as regulators have yet to clarify the rules around hydrocarbon extraction. In Canada, authorities permit all extraction methods. In the USA, state governments set their own regulations, and many states already use all four methods. Before moving forward in this space, you should evaluate several  factors.

Table 2. We outline various extraction methods and highlight factors to consider when choosing the appropriate method. The € symbols represent increasing costs, with more symbols indicating higher expense. These business assessments may change as technology and market conditions evolve.

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