Botanical Extraction

The Race for a Scaled, Solventless Extraction System

The oldest form of concentration of cannabinoids is a form of mechanical separation that makes a product known as hashish. The earliest versions were very potent resins that were collected from the hands of the folks involved in harvesting cannabis plants. Anyone familiar with harvesting and trimming cannabis flower has experienced this. Technology and consumer tastes have changed since making balls of dark finger hash. Current trends show a move back towards solventless extraction and with it comes several technical hurdles that beg for innovation. For example, according to a BDSA report, rosin carts show consistent growth (~177%) year to year, while leading brands show nearly 100% growth in bubble hash sales. We’ve seen the evolution of Rick Simpson Oil to carbon dioxide (CO2) to butane hash oil to distillate to live resin. Is the revival and refinement of hash the next big thing?

Before we get too far into the world of solventless hash, we should define some terms. Solvent extraction is a common and effective method to remove cannabinoids and terpenes from biomass. The big three solvents used (ethanol, CO2, and hydrocarbons like butane and propane) all operate in the same basic manner. Biomass is introduced into an extraction bed and liquid solvent is passed across the bed. The compounds of interest are dissolved into the solvent, the solution is moved to a secondary chamber, and the solvent is removed, leaving everything that was dissolved in it behind. Further refinement is often needed involving temperature or vacuum to remove unwanted solvents and byproducts, or to concentrate specific families of molecules. For better or worse, these methods often involve “chemicals” to which consumers often have a negative connotation. And that’s where solventless has a leg up.

At its core, solventless extraction is a mechanical technique that separates trichomes from plants. This is commonly accomplished by putting the biomass into fabric bags (~200 µm mesh), then placing the bags in near freezing water. Agitation causes the trichomes to break off the biomass and pass through the mesh and into the process liquid. This process liquid is then passed through even finer mesh systems and washed with copious cold water. Common end products are bubble hash, pressed hash pucks, and rosin. Luminaries such as Frenchy Cannoli and Bubble Man have done a fantastic service covering some of these methods with online content and specific tutorials. The equipment overhead is typically quite low and accessible to the home enthusiast which only adds to the popularity. Unlike solvent-based extraction, the risk of blowing up one’s garage or kitchen approaches zero as most of this is done with water.

Current challenges in this space are focused on scale. We can break these down into three categories – cultivation, automation, and rosin pressing technique.

Cultivation proves critical. Like all processes, the garbage in, garbage out axiom holds true – certain plants simply produce more hash. What those varieties actually are is constantly argued about online while the best ones are likely privately held by breeders.

The harvesting and curing processes also play into the success of particular genetics. Paying close attention to the trichome structure during cultivation is vital. If the plants are cut too early, the yield is low; cut too late, the hash is discolored with a lower quality nose to it. Some folks do long cold curing of night-harvested biomass in refrigerated rooms and claim this provides the best material. People also run fresh, frozen biomass that has no cure process which makes the timing of harvest all the more important. Since this product isn’t a commodity – like distillate – the quality of the input is more important than other less exacting products.

While it is possible to hire loads of people to hand paddle trash cans filled with water, ice, and mesh bags of biomass, automation is the next step. Bubble hash producers use agitators from recreational vehicle (RV) style washing machines to custom made 12 cubic yard stainless steel concrete mixers. More jacketed stainless steel agitation tanks can be found on the market with volumes in the 100’s of gallons. With programmable logic controls, food grade pumps, and CE (Conformité Européenne) / UL (Underwriters’ Laboratory) listing, these products will likely become the norm in this space.

Another automation challenge is size separation and final washing. You can get as many opinions as there are people in this space about what the “best” micron size range is for hash. Either way you slice it, hash makers need to separate trichomes from their biomass and ensure they are washed clean. Current techniques involve increasingly fine fabric mesh bags and physical agitation both by hand and a stream of cold water. It won’t be long before people begin using large-scale mechanical sieving systems adopted from other industries. The people who produce sand or metal particles of a defined size range have this problem solved.

Maybe the fastest growing product line is pressed “rosin.” This is where technique is key. There are four variables to evaluate – input material, temperature, pressure, and time. The input material is typically flower (cured or freeze-dried) or bubble hash. There are curing techniques that provide better product output than others and are tightly held secrets. Temperature, pressure, and time of press all play off each other during production. There exist patented rosin presses with touch screens and programmable recipes that will ramp temperature and pressure across a time domain depending upon the input material. The geometry of the press plates varies across manufactures, but they all provide a place to collect the warm liquid as it is squished out from the input mass. These are all relatively small benchtop systems that beg to be converted to flow through instead of batch processes. Right now, the labor involved on a per-gram basis is reflected in the high price these products fetch on the market.

The last space of innovation that’s moving fast is conversion of rosin products into a form that allows them to be loaded into a vape cart. As much as “sauce” or “live resin” was an innovation in extraction technique, these products initially were not viable in vape carts. But that has changed. There exist solventless rosin cartridges in the market and they grow in popularity. Techniques developed to generate a stable (non-crystallizing) oil with proper viscosity from “sauce” or “live resin” for a vape cartridge will likely find cross-over into the solventless market.

The race is now on for a scaled solventless extraction system.

About the author

Michael Coffin, Elevation Distro