Rethinking CO2 vs. Other Extraction Solvents

Guest Post by Jesse Turner, Independent Extraction Consultant

Here’s a controversial statement: CO2 done properly can meet or exceed the throughput rates typically seen with ethanol-based extractions.

I got my start in this industry on the hemp side. I was the original manager for Charlotte’s Web CBD extraction laboratory that was providing extracts for children with epilepsy. We started with ethanol and about six months in we decided to bring supercritical CO2 onboard. It changed the way I think about my job.

I’d met Dr. John MacKay from Waters and he pointed me in the right direction as far as peer reviews to read and background on how to properly method-develop. I then took that from the hemp industry onto the recreational cannabis side with Willie’s Reserve.

In my experience, the biggest challenge with CO2 as an extraction solvent is properly understanding the flexibility that it provides as far as targeting specific compounds or specific analytes from your plant matrix. It has the ability to pull out or leave behind many of the compounds — something that you really can’t do with ethanol-based or even light hydrocarbon-based extractions. The opportunities for extraction efficiency due to this property are massive.

There’s also a misconception around the throughputs that are possible with supercritical CO2, and that goes back to methodology and the way that some of the current equipment is manufactured. Most extraction managers can, with some proper training and knowledge, get the results that they want relatively quickly. But there’s another level of knowledge that pushes the possibilities with this solvent into uncharted territory. That’s where I want this community to go.

For instance, one of the big selling points of ethanol-based extraction is the ability to get high throughput. But any ethanol system that you use is going to require winterization, whether it’s in-line with equipment, or further down the production pipeline. And that requires a big capital expenditure for equipment, plus it adds labor and time — often days — to your process.

From my experience and data that I’ve collected, if we start with industry-standard CO2 extraction methods on equipment that’s typically used, there’s room for productivity gains as high as 4X just from changes in methodology alone — while maintaining a really high purity in the crude.

I’ve developed a methodology that requires no winterization equipment and no flammable solvent. If you’re looking to create a high quality distillate as your end result you can have a CO2 extractor and your method, and you can go straight from your extractor into your distillation rig without a need for that time-consuming process.

Another big issue in the extraction equipment market is that manufacturers will claim higher and higher solvent flow rates, and to somebody that hasn’t had experience with this technology that may seem like a selling point. In actuality a lot of the systems on the market are going to have issues with solvent channeling as flow rates get too high, and what channeling is going to do is reduce your efficiency so that, at the end of the run, you’re going to be throwing out material that’s full of THC and CBD. And that loses you money.

Something I’m going to be focusing my future research on is dialing in the specifics on all the analytes’ solubilities, whether it’s the cannabinoids, minor cannabinoids, or monoterpenes, and start to build a map of the densities when these reach their maximum solubility. Because at some point there’s going to be the best method for Product X, and to find that you really have to find the maximum solubility for some of these target analytes, and that simply has not been done.

Once it has been done, there are features that I’d like to see on all future CO2 machines to track density not only in the extraction chamber but also in the fractionation vessels after extraction. It’s something that’s missing and it is absolutely the key component to running a proper CO2 extraction.

We’re on the cusp of some big discoveries in cannabis extractions, and I’m excited to do my part to bring them into the light. But the community of extraction managers, and the businesses that rely on us, will only succeed if we all learn to throw off some of the default thinking that’s driving machine purchasing decisions today.

About the author:

Jesse Turner is an Independent Extraction Consultant helping companies push the limits of what’s possible with CO2

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