Techniques for THC Remediation
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As the commercial CBD market has exploded in popularity in recent years, THC remediation has become a similarly exciting field for processors and CBD product manufacturers to explore. But how is it done?
Why is THC remediation important?
At the botanical level, hemp and drug-type cannabis plants are both of the same Cannabis sativa species. As defined by law under the 2018 farm bill, however, the term hemp refers only to Cannabis sativa plants containing less than 0.3 percent THC by weight.
Sticking to these strict statutory cannabinoid limits can be more difficult than expected. Cultivators sometimes discover that their hemp crop has grown “hot,” meaning that it has exceeded the 0.3 percent THC limit.
“A lot of the plants that are grown, hemp wise, they naturally just have a percentage of THC that is over the legal limit, which is 0.3 percent,” Danielle Coluccio, a formulation chemist at Hemp Synergistics, told Analytical Cannabis.
“You can go ahead and take that biomass through the entire process until you have an oil, but, unfortunately, that illegal limit is going to be carried over into your final product oil. So unless you have a license to be selling something over the legal limit, you’re stuck with an oil that you can’t work with.”
THC remediation services are a solution to hot hemp, making sure that the resultant hemp oil contains low THC levels, in keeping with local and federal law. Depending on the process used, THC remediation can also be used to create more novel products, such as THC-free broad-spectrum oils or cannabinoid isolates.
THC remediation techniques
Remediation is a broad term, encompassing almost any method or process that can reduce the level of THC present in a given cannabis or hemp product. Although chromatography-based methods are arguably the most popular approach, there is a range of different remediation methods currently in use within the mainstream processing industry. Each of these methods comes with its own unique advantages and disadvantages that need to be managed as the sector progresses.
Chromatography systems can be very expensive to implement for some operators. However, if this high price point is not an issue, chromatography can be an extremely effective method for THC remediation, as it is capable of removing almost 100 percent of the THC present in a starting product.
Chromatography works by taking advantage of the difference in polarity between CBD and THC, THC being less polar. This means that when a solution of solvent and hemp oil is placed over polar chromatography column media, the THC will flow through the column more quickly, as it is not hampered by any polar attractions. This fraction of THC can be collected and disposed of, resulting in THC-free oil, once the solvent is evaporated off of the remaining eluent mixture.
This basic principle of chromatography is the same whether a standard column chromatography, flash chromatography (chromatography assisted by applying a positive pressure differential), or high-performance liquid chromatography (HPLC) approach is used. Tinkering with the polarity of the mobile and stationary phases involved can also further affect the separation of the cannabinoids in the hot hemp starting sample, and processors will use this to their advantage in creating different types of finished products.
“We prepare the oils in a solvent-to-oil ratio mixture, and then we feed this into our [chromatography] units that do all of the magic. During that time, we can also create a method,” Coluccio explained.
“Every single oil that comes in the door is a little bit different, and we will either create or adjust an existing method that we already have. What we get out is the separation of cannabinoids, and depending on what the customer wants, we might have one fraction, we might have three fractions, six fractions, it can really get complicated.”
Reverse phase flash chromatography is one of the most popular chromatography variants used in THC remediation, and is the methodology employed by Hemp Synergistics. In reverse phase chromatography, the stationary phase is a non-polar substance, meaning that THC will be the slowest compound in the mixture to elute. This allows for the rest of the hemp oil to easily pass through the chromatography apparatus, leaving the THC behind to create a simple THC-free broad-spectrum oil.
Centrifugal partition chromatography (CPC) is also gaining ground in the THC remediation space. CPC is a liquid-liquid chromatography technique that does not rely on the same solid phase chromatography column as seen in other methods, eliminating the need for this costly consumable. Instead, CPC uses two immiscible liquids that act as the stationary and mobile phases needed in chromatography, with the various compounds eluted according to their partition coefficients rather than polarity. These two liquid solvents can also be largely recycled between runs, negating a lot of the environmental impact common with other chromatography setups.
Alternatives to chromatography
While CPC does represent a step forward in this regard, chromatography-based methods do generally involve the use of significant amounts of harsh chemical solvents and expensive stationary phase consumables. This can be costly for processors to upkeep, even if the upfront costs of a chromatography apparatus are manageable. But for the processors who do not have the means to invest so heavily in a THC remediation operation, there are alternatives to explore.
Over time, THC naturally degrades into CBN when left at ambient conditions. For the cannabis industry, this is usually considered to be an unwanted process, and much time has been spent investigating how to slow this natural degradation so that users of drug-type cannabis are not given stale products. But for the hemp industry, this degradation opens up a new avenue for THC remediation.
More research is still needed before these techniques can be considered to be fully developed, but processors are already experimenting with chemical conversion using solvent techniques, UV light degradation, and heat oxidation to speed up this natural degradation and act as a THC degradation protocol.
Challenges and trends in THC remediation
Efficiency in THC remediation goes further than just which remediation method is selected. Proper testing of the hot hemp sample before, after, and sometimes even during remediation treatment, can help to personalize the remediation process for each sample to minimize potential losses.
“I will say that whenever we first started this process, there was [an issue with loss]. We took really, really big strides, very quickly, to ensure that we were no longer getting that loss,” recalled Coluccio.
“The biggest challenge we were seeing, which we were not addressing, is that every oil that we get in is different. Every single oil has a different profile of cannabinoids, every customer wants a different end product. So we just weren’t changing and adjusting the method, or creating new methods, as often as we should have. [Now] it is like second nature.”
“Whenever we first get an oil, one of the first things we like to do is do an in-house analytical test on it,” Coluccio said. “In doing that, we can actually go ahead and remove any of those residual solvents and waxes to make the remediation process better and easier, so that we can give them a better end product.”
Extensive testing also revealed another challenge for THC remediation, the acidic cannabinoids. These cannabinoids are present in significant amounts in raw hemp material and have recently attracted attention following the discovery of cannabidiolic acid’s (CBDA’s) powerful anti-inflammatory action. The trouble is, CBDA and the other acidic cannabinoids are relatively unstable compounds and will very readily convert into their neutral forms when exposed to high temperatures or left to degrade over time. Working to maintain high levels of these acidic cannabinoids in finished remediated hemp oils is one of the most exciting challenges facing the cannabis processing sector, Coluccio believes.
“These cannabinoids are pretty high maintenance, if you will. They’re really sensitive to a lot of things and we had to nail down what we had to change our process to have a whole different method to process and remediate and work with this set of cannabinoids,” Coluccio said. “I would say that that’s our most exciting project that we have going on in the lab right now.”