Liquid Gold: Engineers Strike Oil Making Customized Extractors for Cannabis

Cannabis use is on the rise, even as smoking pot is becoming passé

By Caroline Seydel

The weed industry is experiencing a cultural shift, from a “wild west” atmosphere to a legal and highly regulated field, creating opportunities for trained chemists and engineers to develop customized equipment and ensure safe procedures as small operations scale up.

Cannabis use is on the rise, even as smoking pot is becoming passé. The percentage of cannabis users who partake by smoking is dropping off, as concentrated inhalation products, such as vapes or dabs, become more popular. Plenty of people, it seems, seek marijuana’s effects but prefer not to smell like a Grateful Dead concert. Concentrated cannabis oil products deliver higher amounts of cannabinoids in smaller, more discreet packages.

Crafting these new products requires an expertise in chemical extraction and purification of cannabis oil. Cannabis cultivators know their stuff when it comes to growing different varieties, and how the physiological effects differ among strains. Yet they still may feel intimidated by extraction, which requires specialized chemistry and engineering skills. Many now turn to extraction experts to help transform their plants into different consumer products.

Plant extractions involve grinding up the organic material and bathing it in a solvent to pull out the desired components. The three main solvents in common use are hydrocarbons, supercritical CO₂, and ethanol.

Hydrocarbon solvents, specifically N-butane and propane, have been popular because they’re easy to use and powerful, able to capture a wide array of compounds at reasonable temperature and pressure.

They also leave behind more of what isn’t wanted. The cannabis plant contains a multitude of chemicals that contribute not only to the drug’s effects, but also to the aroma and flavor profile of the finished product. Because butane is nonpolar, it efficiently pulls out the cannabinoids and the terpenes, while ignoring the polar chlorophyll molecules, which can lend an unpleasant “grassy” character to the final extract.

But hydrocarbons are highly flammable, and dangerous to work with in huge quantities.

CO₂, meanwhile, is a less powerful solvent, but it’s non-flammable, inexpensive, and environmentally friendly. Supercritical CO₂ means the carbon dioxide is brought to a temperature and pressure above the “critical point,” where the boundary between liquid and gas becomes fuzzy.

Supercritical CO₂ has liquid-like density and gas-like diffusivity and viscosity, making it better able to penetrate the cell and draw out the soluble compounds.

Ethanol, for its part, extracts the cannabinoids and terpenes more efficiently than CO₂ and more safely than hydrocarbons, but it also pulls out undesirable components, such as chlorophyll.

The extract requires more distillation and purification steps to clean it up. It’s a very effective method for producing purified compounds. But different strains contain unique combinations of cannabinoids and terpenes, so operators who want to preserve that individual character prefer to minimize the post-processing steps.

Tune in, turn on

“What extractor is the best? It depends on what you’re trying to accomplish, and at what scale,” says Garret Nicodemus, PhD, COO of Xabis. Based in Colorado, Xabis works with cannabis and hemp growers to design and operate extraction facilities that meet their needs.

“It’s fun, because there’s the chemistry side, and then for us as engineers, it’s how do you scale it up?

How do you do it in an efficient and economical way?” says Nicodemus, who has a PhD in chemical and biological engineering. At Xabis, they focus on CO₂-based extraction, because of the versatility of the solvent.

“CO₂ is a really interesting solvent,” says Nicodemus. “CO₂ is ‘tunable.’ You can change the pressure and the temperature of the CO₂ to selectively extract. If you’re aiming for certain components or ratios of compositions, you can tailor the extraction process with greater selectivity.”

For instance, extracting with low pressure, low temperature liquid CO₂ brings out more of the molecules responsible for flavor and aroma. “People would use subcooled liquid typically to capture a higher content of terpenes, and more volatile species from the plant,” says Nicodemus. “It will do a decent job of extracting cannabinoids, but not nearly the same throughput as operating as a supercritical fluid.” Extracting with supercritical CO₂ improves the efficiency for the cannabinoids, but may degrade some of the more volatile chemicals.

Although most research has focused on tetrahydrocannabinol (THC) and cannabidiol (CBD), cannabis contains dozens of potentially interesting cannabinoids. Tweaking the conditions of the extraction can allow for targeting of different molecules, without the need to start over with a different solvent. Xabis adjusts their processes to maximize efficiency while preserving the desired characteristics of the end product. “It’s more than just extraction,” Nicodemus says. “Throughout the process, from the moment you have harvested material to the moment you get product out the door, there’s efficiencies at every step. For us, it’s about focusing on each of those efficiencies, measuring, analyzing, and improving upon them, so your overall efficiency is as high as possible.”

This analytical approach sets Xabis apart in the emerging field of cannabis and hemp processing.

“It’s so cool being in a brand new industry,” Nicodemus says, and the company has a commitment to educating lawmakers on safe and sensible practices. “We’ve seen a lot of ways people have skirted laws and regulations,” he says. “We want to believe we’re doing things right, we want the clients to feel like they’re doing things right.”

All in good taste

After working with an expensive, cumbersome, and inefficient extractor, Shane Lander thought he could do better. Lander, the co-founder of Soma Labs and current chief R&D officer of Quadron Cannatech, decided to design his own machine, one that wouldn’t require months of training to operate. “Generally when an engineer designs something, they will never operate that machine,” Lander says. “For us, that will not be the case.” Soma, now a wholly owned subsidiary of Quadron Cannatech, uses their own equipment. They offer extraction services in addition to selling the CO₂ extractor they call “The Boss.”

The Boss by Soma Labs.

To improve efficiency and reduce the device’s footprint, Lander hit on the idea of incorporating a heat pump to reclaim the wasted energy and recycle it back into the extractor. Conventional extractors require separate heating and cooling units, and all the excess energy is vented into the room.

The Boss recaptures 40% of that energy, dramatically reducing both its footprint and its electricity requirements to around 20–25% of extractors with similar throughput. “The Boss’ most current updates have included the addition of a proprietary Clean-In-Place System that reduces the amount of down time otherwise required for regular cleaning maintenance,” Lander says.

There was one thing he didn’t want to change about that big, old machine, though. “That ‘monster’ did make really nice stuff, because it wasn’t capable of high pressures and high temperatures,” Lander says. “People go to high pressure and high temperature to get high throughput. I wanted to design this thing so we can get high throughput at the low temperature and low pressure, and have the best of all worlds.”

CO₂ reaches its supercritical point above a temperature and pressure around 32°C and 1070 psi. The higher the pressure, the more efficiently the CO₂ pulls the soluble chemicals out of the plant. But too high, and the extract acquires undesirable qualities. Soma’s extractor keeps the CO₂ at temperatures not exceeding 50°C and pressure up to about 2000 psi. This achieves efficient extraction without imparting a “burned” aroma and flavor to the resulting extract. “You don’t get that caramelization of the product,” Lander says.

Once the supercritical CO₂ has collected all the oils, it’s put through into the separator, where the drop in pressure and a bit of heat vaporizes every last droplet of CO₂, separating the gas from the valuable oils. “The operator can, at his convenience, just open the valve up and push out a whole bunch of product that looks like soft serve ice cream.”

After the cannabis oil is extracted, it’s “winterized,” meaning the oil is cooled until the heavier fats and waxes solidify. After they are removed, the resulting oil can be sold as-is, with its complex profile of terpenes and cannabinoids, or further refined by distillation or chromatography to obtain pure THC, pure CBD, or some mixture containing a combination of various cannabinoids and terpenes.

Helmed by CEO Rosy Mondin, Quadron Cannatech not only sells extractors but provides a variety of processing services and technical support for the cannabis industry, continually innovating the equipment, techniques, and formulations necessary to develop new cannabis products.

Beyond CO₂

Radient Technologies uses microwaves to coax the oils from the cannabis biomass. Zapping the plant material with microwaves heats it up fast and allows precise control over the length of time that the material is heated. This method gives Radient’s method an advantage when developing commercial-scale facility, says Steven Splinter, PhD, CTO of Radient.

Drawing on their many years of expertise producing other botanical extracts, Radient turned their attention to cannabis a few years ago. Legalization of cannabis for nonmedical uses in Canada heralded a wave of change in marijuana and hemp production, Splinter says. “There would be a significant need to be able to extract cannabinoids, not just with high efficiency, but to be able to make safe, standardized products to specific concentrations,” he says. “We were well positioned.”

The company uses a continuous-flow extraction system whereby the dried, ground-up plant material is mixed with a liquid, generally ethanol, and then heated with microwaves. Unlike conventional heating methods, like convection or radiation, microwaves heat by direct interaction with the molecules themselves, allowing an entire volume to be heated instantly. The microwave energy, mostly absorbed by water molecules inside the plant, creates pressure and drives the extraction.

“You’re not waiting for the slow process of diffusion,” Splinter explains.

Another benefit of microwave extraction, Splinter says, is that different materials heat differently.

This allows the extraction of just the desired cannabinoids and terpenes, without co-extraction of undesirable waxes and pigments. The method uses far less solvent than conventional extractions, and requires less post-processing. Extract analysis shows that the complex cannabinoid and terpene profile present in the plant are preserved in the extract. Even for medical purposes, it’s not just a single component that’s required. Often the various chemicals exert a synergistic effect, so extracting them all together could help patients get the full spectrum of cannabinoids.

With microwave-assisted processing, Radient has achieved dramatically reduced extraction times, and report processing capacity of 200 kg of cannabis biomass per day at their Edmonton, Canada location. The company is currently both expanding their Edmonton operation and building a new facility in Europe, each capable of processing 1000 kg of cannabis or 10000 kg of hemp per day.

Partnered with Aurora Cannabis since 2016, Radient could soon be standing at a profitable intersection of high yields, high purity, and tight quality control standards.