Many processes have been adopted for extraction and refinement of cannabis. Much like traditional botanical extractions, the aim of these techniques is to provide the desirable qualities of cannabis in a more readily usable form for the delivery method of choice. The wide range of options available has left processors questioning the best method for their extractions. A goal-oriented approach, focused on finding the best fit between process and physicochemical product attributes is critical. Pairing this goal-oriented process development with analytically guided optimization will allow for the development of an ideal process to deliver the best end product.
One of the key challenges when designing a cannabis processing plant is the overwhelming number of options available. Within a cannabis processing plant, decisions about unit operations will need to be made around preprocessing, extraction, and purification. Even after landing on an extraction process between light hydrocarbon, ethanol, solventless, or supercritical fluid options, there are myriad equipment vendors offering the latest and greatest technologies for each process. This plethora of possibilities leads to the unfortunate, but unavoidable question: What’s the best? While this question addresses some basic design options for the process, the far more critical question to ask is, what’s the best for my products?
Answering that question demands a holistic view of the process, and not simply siloed unit operations. This question drives us toward goal-oriented process development, which invariably results in higher efficiencies and higher end-product quality. Regardless of whether the end product is as basic as a simple extract, a high-end consumable, or a pharmaceutical-grade formulation, understanding the physicochemical attributes that drive that product’s quality will assist in making decisions about how to design a cannabis process. These attributes may be things like cannabinoid potency ranges, viscosity, color, clarity, or aroma. Each of these desired properties can be carefully crafted by choosing and arranging the optimal unit operations into a complete process.
While the common parlance in the industry has become “extraction lab,” when designing a cannabis process there are three key stages: preprocessing, extraction, and purification. Each of these stages is filled with options that will affect the properties of the resulting cannabis extract. Making decisions about those stages becomes much more straightforward when you are armed with the requirements of an end product.
Preprocessing may begin as early as making decisions about how to dry and store cannabis raw material. If, for example, the end product requires fresh aroma notes like a live resin, then this unit operation may demand no drying and frozen storage. If, on the other hand, the goal is to deliver the traditional cured flavor of cannabis, then identifying the optimal temperature, humidity, and moisture content will drive the development of that process step. The key is identifying metrics by which to grade our process—in this case, perhaps moisture and terpene content—and having a way to measure it.
A recurring theme in process development is the criticality of analysis. Analytical methods provide the feedback required for design. In the above example, a drying process is proposed for delivering a targeted terpene profile. That process could then be carried out, and the resulting dry cannabis raw material could be analyzed via gas chromatography (GC) to determine if the targeted terpene profile was achieved. Because the target is rarely achieved on the first attempt, the drying process conditions (temperature, humidity) should be altered, the experiment repeated, and more terpene data collected. This iterative process design will result in an optimized approach while keeping the goals of the end product in mind, all because of the feedback provided by analysis.
Another important preprocessing step is raw material size reduction. This step is often skipped, but in many cases, it can enhance the efficiency and quality of a cannabis extraction process. The goal of this process step is to decrease the particle size of the material to be extracted, resulting in an increased surface area available for solvent extraction. Again, taking a holistic view, we might recognize that this would benefit solvent-based extraction processes such as those using butane, ethanol, or a supercritical fluid, but perhaps would be detrimental to some of the solventless extraction processes.
Next, we look to the goal of our process. Let’s assume we are interested in delivering the bioactive components of the cannabis raw material as close to their natural state as possible in our finished extract and optimizing the efficiency of our extraction process. We can then define metrics that tell us if we have accomplished those goals. For example, I may hypothesize that by creating a ground raw material with a consistent and small particle size I will increase the efficiency of my extraction. Again, we turn to our iterative process design mindset and test several size-reduction variables (that is, milling versus grinding, room temperature versus chilled, low-speed grinding versus high-speed grinding), and using an instrument such as a sieve shaker or particle size analyzer I can determine which process variable gives me the smallest and most consistent ground particle size. To achieve the goal of delivering “nature identical” bioactives, I can analyze for target compounds such as the cannabinoids and terpenes before and after the size reduction process to ensure that degradation resulting from thermal or oxidative damage is minimized.
- J.C. Raber et al., The Journal of Toxicological Sciences 40(6), 797-803 (2015), doi:10.2131/jts.40.797.
- Colorado Department of Revenue, Marijuana Enforcement Division, “Recently Adopted Retail Marijuana Permanent Rules - Effective January 1, 2018.” https://www.colorado.gov/pacific/enforcement/med-rules, p. 123.
- C. Sweeney, “Cannabis Extraction and Refinement in Colorado: A 5,280 Ft. View” presented at the Cannabis Science Conference, Portland, Oregon, 2017.
- M. Mukhopadhyay, Natural Extracts Using Supercritical Carbon Dioxide (CRC Press, Boca Raton, Florida, 2015).
How to Cite This Article
C. Sweeney, Cannabis Science and Technology 1(1), 54-57 (2018).