Supercritical carbon dioxide (CO2) extraction is a processing technique in which CO2 is put under pressure and at carefully controlled temperatures to extract terpenes, cannabinoids and other plant molecules. Once the extract is obtained, the crude oil is often subjected to an ethanol-winterization process to remove chlorophyll, fats and waxes.
Green Mill Supercritical is a Pittsburgh-based manufacturing and development company specializing in hemp and cannabis. The company offers a range of CO2 extraction equipment that allows users to customize and control their extraction methods. They recently announced a technological advance that would allow in-process winterization, which could eliminate the need for ethanol winterization.
We spoke with Jeff Diehl, director of marketing for Green Mill Supercritical, to learn more about this new process. Jeff was working in tech in San Francisco in 2017 when his cousin Jeremy Diehl, founder and CTO, invited him to join Green Mill.
Aaron Green: Before we talk about your new technology, can you tell us a little about the industry trends you see?
Jeff Diehl: The big thing I’m thinking about is a premium hood slot. More and more consumers are asking for high quality extracts. They want differentiated products. They want products that are safe and have some sort of meaningful connection to the specific plant they come from. CO2 currently plays a minor role in the market for these products. Most high-value products come from the production of hydrocarbons. So I see how people are using CO2 to create a new generation of safe, quality products.
Aaron: What does the normal CO2 extraction process look like today?
Jeff: The current CO2 extraction process typically involves two main stages to obtain the final extract. In the first phase, you have a mine where you get your raw product from. The second step, after extraction, is to obtain refined oil by refining. As part of this post-operational phase, ethanol-based winterization is performed in most plants.
Aaron: What exactly is done during the hibernation phase?
Jeff: The winter consists of removing the wax. Your main loot is considered unprocessed because it contains a lot of factory material that you don’t need. The vast majority of unwanted material is wax. In winter, a solvent, traditionally ethanol, is used to separate the waxes from the cannabinoids. Ethanol-based woodworking presents many challenges that result in cost, time and product loss. It’s terribly inefficient. In addition, there will always be residual ethanol in the final product, which consumers do not like.
Aaron: They recently announced a new process at the Green Mill that involves transferring the overwintering phase to a supercritical CO2 system. Can you explain how this works?
Jeff: In our process, which we call Winter in Real Time, no ethanol is used in winterization. This all happens with CO₂ during primary degradation. This is a great achievement of our process, and while there have been previous attempts, no one has been able to do this in a viable way. They take a process that normally takes four days – one day to extract the CO2 and three days to winterize the ethanol – and do it in less than one day. We have the automated software, sensors and pumps to make sure everything runs smoothly.
Aaron: How is the quality of the resulting product compared to the new process?
Jeff: You can see the difference immediately if you know what extraction is. It looks clean and shiny. The lab tests are very positive so far, but we are still testing. Our research team has conducted numerous tests, primarily on cannabis and CBD. That’s because we don’t have a license for THC. We are currently working with an accredited partner to collect more data on THC products and provide accurate figures. But with CBD, we’ve done a lot of testing to validate the method and the technology, and we consistently get great results, both in terms of the purity of the product and the efficiency of the process.
Aaron: How can we compare the yields of different processes?
hemp CBD extract straight from the SFE Pro green mill works in real time winterization.
Jeff: The data we have seen in the industry shows that during ethanol overwintering 5% to 10% of the cannabinoids remain in the wax. It’s just a loss. With real-time CO2, the recovery rate is as high as 99%. We are still investigating this result with tests to make sure it is not an aberration, but in any case the recovery rate looks promising.
Aaron: One of the other problems with ethanol are taxes and the ability to find food. Do you have a point of view you want to share?
Jeff: Ethanol removal has a number of advantages. Just the amount of ethanol is a factor. The handling of large quantities of ethanol is subject to numerous regulations and fire safety requirements. Ethanol hibernation is not a process in itself. There are several steps: mixing, freezing, filtering and removing the solvent. These are all occasions where things can go wrong, so you always have those risks under control. Many large appliances such as exhaust hoods, filter skids, cryogenic freezers and rotary evaporators are expensive and require a lot of management.
I think Elon Musk said the best process is no process. If steps can be eliminated in an industrial process, this is the way to go. And that’s exactly what we did. As a result of this recent work, we have effectively eliminated post-processing for certain categories of finished products.
Aaron: Do you have any patents on the new process?
Jeff: We have patents on both the method and the equipment, so we can talk about it like that.
Aaron: So how does this work if someone already owns a Green Mill unit? Is this something that can be adjusted? Is this a software update?
Jeff: There are two components. One is the equipment upgrade that can be made retroactive for existing customers, and the other is the upgrade of the methodology we use to help our customers. Automation software can inherently make the necessary adjustments to perform the methodology. In fact, it was this software and the rest of our existing process, the proprietary pump, the triple in-line splitting, the accuracy and stability of the entire system that made this overwintering possible.
Aaron: Where do you introduce it first? And are you thinking of going international?
Jeff: The international market is definitely in our sights, as we have already sold systems abroad. We are currently preparing to announce the opening of our beta program with the new technology. So we are not yet ready for such a wide sale, but we are accepting applications from companies who want to come early and join us at the forefront of innovation in CO₂ mining.
Aaron: Okay, great. Thanks, Jeff. That’s the end of the interview.
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