Understanding Extraction Techniques
Art meets science when it comes to cannabis extraction. From lovingly hand-sifted kief to large-scale scientific isolation methods, understanding extraction techniques can help retailers to recommend the right product to customers.
Since October 2019, inhalable extracts (vape carts, shatter, hash, kief, etc.) and edibles have joined ingestible extracts (oils/capsules) in the legal non-medical cannabis market. LPs often work with white label extractors (toll processors) to create products that suit various formats, depending on how much flavour or pure cannabinoid is required.
In simplest terms, extraction involves isolating the trichomes (glands) from the cannabis plant, in order to process it as a concentrated form of cannabis that can be ingested or inhaled. It can be further distilled or refined to isolate cannabinoids like THC or CBD, for use in edibles and vape carts.
Volume/yield vs quality are the two major considerations when it comes to choosing an extraction technique. Closed loop extraction systems (e.g. CO2 extraction) are automated processes that are set to achieve a specific result, whereas open-loop systems (e.g. bubble hash/kief) require manual input into the process. Labels may say solvent-free—this could mean that solvents were used during extraction but removed after the process, whereas ‘solvent-less’ means that no solvents were used in extraction.
“The industry is making millions of different products from cannabis and hemp using many different techniques to get the product results they are seeking,” says legendary extraction expert and inventor Wacky Willy. “It really depends on the variables of the state of the botanical (fresh, cured, frozen, freeze dried), or how the extractor deploys their twist on the scientific process required to get the result.
Each method or technique can result in vastly different outcomes with just one small differentiator added to the process.
“Think of the wine industry, where every vintner has their own special twist on winemaking that makes their brand unique to all other wines. However, they will all need to practice their own creative craft using the same basic science that turns a fresh grape into a beautiful glass of Merlot or Chardonnay. For example, making white wine requires a different grape varietal and scientific process than red wine, champagne, or dessert wine. There is also the artistry side of making wine. It only takes the adjustment of a single parameter (time, temperature, varietal) to change the flavour, consistency, or colour to make the product their own special vintage.”
Wacky Willy favours a solvent-less approach to extraction that enables people to be hands-on and create a product without the use of chemicals or combustion. A harder and faster approach to aggressively washing bubble hash or shaking dry sift will give a higher yield, but a gentler approach with less processing time will have a lower yield but leave more of the precious trichomes intact and produce a higher quality extract.
Solvent-less extraction techniques range from using ice and water to create bubble hash, filtering or sifting kief with our without dry ice (cold temperatures harden the trichomes and make it easier for them to separate off the plant material)r, or dry sifting kief through a mesh screen. Rosin concentrate is made by applying heat and pressure to flowers, hash, or kief. While these hands-on techniques have been around for a long time, Wacky Willy has created new innovations that make the processes more efficients—for example, his new Boomers Big Buzz vibrating table for sifting kief and his Arctic Boomer, which uses compressed air and sub zero temperatures to create bubble hash without the need for ice.
Hydrocarbon extraction techniques dominate the US market, whereas CO2 extraction is the most common technology in Canada owing to Health Canada regulations.
The Cannabis Act specifically bans the use of ‘organic solvents’ (e.g. ethanol, butane, propane) extractions without a licence, due to the volatile nature of production.
Hydrocarbon involves the use of butane or propane solvents to remove specific molecules from plant matter—it’s one of the more affordable methods and its high yield rates and preservation of terpenes make it a popular choice, although it’s volatile (flammable) nature and storage/zoning restrictions can make it harder for producers to make it work at scale.
In an ‘open blasting’ extraction, butane is combusted through the plant matter to release oils from the trichomes, which are then collected in a container that is placed in hot water to evaporate the butane and leave the cannabis oil (aka BHO or Butane Hash Oil), which forms the basis of concentrates such as shatter, budder, or wax. Impurities in the flower (e.g. mould, contaminants) can be concentrated into the final product, so most commercial companies use a closed-loop system to keep the flammable solvents contained while they are pressurized and recovered for reuse.
Cryo-ethanol extraction involves cold ethanol being washed over biomass to extract the desired molecules. It’s a cost and time efficient process that can be done quickly to mass-produce a product, but the flammable nature of the process leads to similar zoning and storage problems as hydrocarbon extraction. Following extraction, the product can be distilled to further isolate THC and CBD, essentially scrubbing it clean of all other flavonoids and terpenes.
“All methods can be used low and slow to preserve secondary compounds or turned up to remove as many active compounds as quickly as possible,” says Tyler Robson, CEO of The Valens Company, which is Canada’s largest toll extraction processor. “Each extraction has its pros and cons, but when proper IP is applied with science and art to each extraction method, premium results can be achieved many ways. At Valens we lead the way by offering the most diverse methods of extraction, CO2, alcohol, hydrocarbon and solvent less. For pure isolated cannabinoids we defer to alcohol-based extracts for high input through-put with an in-situ process to achieve high potency distillate. From there we use very specific chemistry to isolate pure THC or CBD compounds to >99% purity.”
CO2 extraction is a natural (solvent-less) method that combines carbon dioxide with extremely high pressure to extract molecules. It is often used to create ‘full-spectrum’ oils that contain the flower’s original terpenes and cannabinoids. Lower yields, longer run times, and substantial upfront costs make CO2 extraction more of an upfront expense, but it does give producers the ability to scale up in a commercial setting. Supercritical CO2 extraction involves the use of carbon dioxide, which is considered a ‘tuneable solvent’ as it can reach a supercritical state (having properties of both a liquid and a gas) and be easily tuned to bond to any molecule the producer chooses.
“Supercritical CO2 extraction has been used for decades to extract valuable compounds from natural products, largely plant foods such as seed oils, and it is widely employed by coffee manufacturers to decaffeinate coffee beans, ” says Dr. Tait Gale, MediPharm Labs’ R&D Manager. “Supercritical CO2 extraction is generally regarded as a greener technology compared to alternative methods, given the solvent’s non-toxic and non-flammable nature. As a research-driven company, MediPharm Labs is working towards fine-tuning extraction temperatures and pressures to maximize the solubilities of cannabinoids during extraction. Our cannabis processing workflow includes extraction, winterization, filtration, and then short-path distillation. ”
Learning the various extraction techniques can help retailers to differentiate between products and intended uses. “Having a clear understanding of extraction techniques with the solvents used is a key learning,” says Robson. “Retailers should know the extraction techniques and what solvent limits to look for on a COA with each technique.”