Does Activated Carbon Cause Yield Loss in Cannabis Extract?
Updated: 10/29/2021
One of the biggest obstacles cannabis processors face when using ethanol as a solvent is how to deal with dark extract caused by the presence of chlorophyll.
Besides having an unattractive color, chlorophyll is also known for having a bitter taste. It’s understandable why a processor would want to purge this pesky compound from their tincture. The process of removing unwanted color bodies such as chlorophyll from extract is known as color remediation or decolorization.
There are several methods used to remediate color from ethanol extract. The most efficient method involves using activated carbon—also known as activated charcoal—which has been shown to be highly effective at removing chlorophyll. However, there has been heavy debate among processors as to whether activated carbon has a negative impact on yield.
Thankfully, a recent study done by Seedless Analytical LLC provides concrete, empirical data to quash the anecdotal claims and hearsay.
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What are the Concerns Regarding the Use of Activated Carbon?
Despite activated carbon's effectiveness at removing color from ethanol extract, there are some who voice concerns about potential damaging effects on their tincture.
Concerns generally relate to claims made by other processors regarding heavy yield loss after carbon scrubbing. These claims are largely based on anecdotal evidence and provide little in the way of empirical data to back them up.
The process of removing unwanted color bodies such as chlorophyll from crude extract using Activated Carbon.
There are two common allegations regarding yield loss due to carbon scrubbing.
Claims of Cannabinoid Retention
Perhaps the most common claim about activated carbon is that, while it does a good job of removing color, it also removes desired cannabinoids. It's easy to understand why this notion would discourage processors from using activated carbon. After all, what good is an amber tincture if it has the potency of tap water?
Claims of Isomerization
One of the more alarming rumors about activated carbon is that it acts as a catalyst to chemically convert delta-9 THC into delta-8 THC—a process commonly referred to as isomerization. Unwanted isomerization is a significant concern for distillers looking to meet a specific cannabinoid profile.
Amidst the slew of anecdotal reports and rumors, how is a processor supposed to separate fact from fiction?
Third-Party Evaluation by Seedless Analytical
In collaboration with ErtelAlsop, CLEAR Solutions tasked a third-party lab testing and consulting company—Seedless Analytical LLC—to objectively evaluate ErtelAlsop’s Micro-Clear™ Activated Carbon media and measure any negative effects on yield.
Parameters of the Evaluation
The experimental trials were conducted using ethanol tincture obtained from a Delta Separations CUP-15 at -40°C. The tincture was filtered through a 4T Lab Filter Housing using ErtelAlsop’s MC55C Carbon Filter pad. A BYK LCS IV Spectrophotometer was used to measure the CIELAB color space values of the tincture before and after filtration through the carbon media.
To test results on yield, the samples were run on an Agilent 1100 HPLC with UV detection at 220 nm. The equipment was calibrated for 11 common cannabinoids, but only THCA, THC and CBDA were able to be reliably quantitated. Control samples were taken from the initial tincture to establish a valid starting point.
Effectiveness of Color Remediation
The results of the pigment removal testing showed that ErtelAlsop’s MC55C carbon filter media was extremely effective at removing green pigment from the tincture.
After circulating the same sample of tincture through the same MC55C filter pad five times, there was only a 40% difference in the reduction of green pigment between the 1st and 5th pass. The results show that while the amount of pigment removal decreases with each pass, the MC55C carbon filter was still able to reduce green pigment by 30% on the 5th pass.
Results on Cannabinoid Retention
The HPLC cannabinoid quantitation data showed that the average concentrations of THCA, THC and CBDA in the post-filtered tincture were virtually unchanged from the initial (control) readings.
| Cannabinoid | Initial (Control) | Final |
|---|---|---|
| THCA | 1.75% | 1.74% |
| THC | 0.180% | 0.177% |
| CBDA | 0.0594% | 0.0582% |
Results on Isomerization
After testing over 30 samples, there was not a measurable signal for delta-8 THC in any control or experimental sample. This suggests that the MC55C carbon media is not capable of isomerizing cannabinoids to form delta-8 THC on its own.
What Is Causing the Yield Loss?
So now that we’ve eliminated activated carbon as the sole source of yield loss, what is causing the loss of potency and isomerization for these processors?
There are many reasons why a processor could experience yield loss during the manufacturing process. With so many variables at play and the vast diversity of equipment setups, it is impossible to provide a definitive answer that covers everyone.
To minimize the potential for yield loss, it is crucial to employ proper quality control measures throughout the processing line. Making sure your team has up-to-date SOPs and is fully trained on all processing equipment will help you to avoid these pitfalls in your process.
Hold-Up Volume Causes Cannabinoid Loss
Cannabinoid loss can occur during the filtration process if a significant amount of hold-up volume remains in the system after the filtration run.
The amount of leftover liquid retained in filter media or equipment after a filtration run is complete.
The leftover crude can be recovered by flushing the filtration system with clean solvent. Additionally, it is important to make sure your equipment is setup with sufficient drain ports to allow for full purging of any remaining liquid.
Leftover Carbon Fines Cause Isomerization
In regards to isomerization, the most likely culprit is carbon fines that shed from the filter and end up in downstream equipment where the tincture is heated for evaporation or distillation. With significant heat applied over an extended period of time, the carbon fines can cause isomerization.
The remedy for that is to add a polishing filtration step downstream of your carbon filter to make sure that evaporation and distillation equipment is protected.
While some activated carbon filters feature a built-in filter cloth to mitigate the shedding of carbon fines, a single layer of filter cloth is not enough to guarantee that carbon won’t make it into your downstream tincture.
The only way to make sure your downstream equipment is protected is to use an absolute rated filter after your carbon scrubbing step.
Conclusion
As you can see, much of the hysteria surrounding activated carbon is simply inaccurate. When these types of unsubstantiated claims arise, it is essential to objectively evaluate them using controlled experiments.
In this case, the data proves that you can safely make use of activated carbon’s exceptional color remediating capabilities without sacrificing yield.