The Future of Cannabis Sterilization

Columns - Tomorrow in Cannabis

Can growers find a balance between preventing contamination and overdrying cannabis?

November 24, 2022


GeorgePeters | iStockPhoto

While many aspects of cannabis cultivation can be measured, dialed in and optimized, the post-harvest process may be the most difficult to rein in. One predicament growers face cycle after cycle is striking a balance when drying plants to ensure bacterial and fungal pathogens do not develop while also retaining adequate moisture for quality.

Overdried cannabis is not a new problem in the industry, but drying effectively at scale has added a new wrinkle to this persistent challenge.

The well-documented costs associated with contaminated cannabis are many. These include:

  • health risks from bacterial and fungal pathogens, especially to immunocompromised patients and those with pulmonary illnesses;
  • disruption in operations, as facility and/or equipment must be decontaminated;
  • testing failures;
  • delays in providing products;
  • certificate of analysis failure registered in METRC; and
  • loss of revenue and/or product.

Compared to this non-exhaustive list of the havoc a disease outbreak can cause cultivation operations, overdried bud may seem less problematic. Many associate the cost of overdried cannabis of being one of quality, but there are potential ramifications that go beyond smokability.

The independent, nonprofit Research Triangle Institute noted in a June 1996 document that “it is advisable to emphasize to all new investigators using marijuana that the moisture content of the [cannabis] cigarettes should be raised above 14% just prior to use. At the lower moisture level, a harsh hot smoke is generated and a higher-than-normal burning temperature, which could lead to abnormally high thermal degradation of THC in the cigarette. Both of these factors can, of course, detract considerably from the efficiency.” The document also noted that “dry marijuana creates a harsh smoke, which is more difficult to inhale deeply. Possibly higher burning temperatures are also likely to contribute to more thermal degradation of the THC thereby decreasing the available drug in the smoke ... .”

Although both contaminated and overdried cannabis are problematic, some cannabis on the market is overdried to prevent the worse possibility of microbial or fungal proliferation.

The aforementioned document was written more than 25 years ago, so cannabis contaminants and the need for sterilization are not new problems. At present, however, each U.S. state has its own required regulations and testing procedures for the acceptable allowed levels of contaminants. If a sample exceeds contaminant thresholds, it cannot be sold and it must be destroyed by law. However, if and when cannabis is legalized federally, the United States Department of Agriculture (USDA) and Food and Drug Administration (FDA) could set very stringent guidelines and may require some form of sterilization via irradiation to eliminate microorganisms. They may also require that no cannabis tests positive for pesticides or heavy metals.

So, how can producers meet state microbial regulatory compliance, prepare for potential federal oversight without adverse effects on cannabis and integrate a cost-effective solution into their operational SOPs?

Some producers in the U.S. incorporate a “kill step,” similar to pasteurizing milk before sale, as part of their SOPs prior to sending samples to the lab for testing, which is also a standard in Canada. Sterilizing technology includes ionizing radiation (x-ray, gamma, e-Beam), ultraviolet light, reactive oxygen, ozone, and non-ionizing radiation (radio frequency) to treat cannabis and eliminate mold, yeast, and any other problematic contaminants before sale. Irradiation is widely used in food production, but consumers and cannabis control boards in some states, including Nevada and Michigan, have mandated or called for product labels disclosing when product has been remediated with sterilizing technology.

Consumer concern over irradiation has been documented in industries outside of cannabis. The FDA addresses this on its website, likening irradiation to milk pasteurization or canning, helping preserve the shelf life while reducing or eliminating microorganisms or insects. “Irradiation does not make foods radioactive, compromise nutritional quality, or noticeably change the taste, texture, or appearance of food. In fact, any changes made by irradiation are so minimal that it is not easy to tell if a food has been irradiated,” the website reads.

For growers considering technology to sterilize cannabis to prevent microbial contamination, there are several questions to ask remediation and sterilization companies when searching for options, including:

  • Are the technologies established and used in/proven by other industries?
  • What is the throughput (measured and dried trimmed flower per eight-hour work day)?
  • Are there any detrimental effects or negative implications to sterilized finished product?
  • Is there any potential risk for the operator/consumer?
  • What is the cost per cycle to operate, including power and labor?
  • What is the cost of the equipment and ancillaries?
  • What is the cost of ownership over five years?
  • What replacement parts/general maintenance are required?
  • What technical support is available after sale/purchase?
  • Does the company utilize outside installation contractors or their own service technicians?
  • What is the cost of warranty and extended warranty?
  • Are there any special permits required to install or utilize the equipment or technology, or required regulatory approval for the processing of cannabis with the specific equipment?
  • Are there any special infrastructure requirements?
  • How long has the equipment been utilized to process cannabis?
  • How long have you been in the cannabis space?
  • Can cannabis be exported after utilizing the technology?
  • What is the lifespan of the equipment?
  • Is the technology compliant with organic processes?
  • Is the technology sustainable? (What is the carbon footprint?)


I was recently in a production facility located in the traditionally very warm and humid Caribbean climate. I mentioned these technologies in passing and was asked if there is technology available that allows a unit to be moved from one dry room to another and sterilizes the undried cannabis while it hangs on racks, allowing a kill step prior to drying, which would arrest and stop any proliferation of any living organisms or fungal contaminants. There is currently no such technology unit available that can be utilized that way. But that question sparked and piqued my interest regarding utilizing one of these technologies to create such a unit that could sterilize or remediate a large room full of cannabis hanging on racks or screens, that could sterilize hundreds of pounds of wet/undried cannabis in less than 24 hours. Perhaps by utilizing the kill step and sterilizing the cannabis prior to drying, it might help retain moisture in the finished product and preserve as many precious monoterpenes and thiols as possible, while also preserving THC and minimizing any degradation, thus providing consumers with a safe product that delivers a more flavorful and pleasant smoking experience.

Kenneth Morrow is an author, consultant and owner of Trichome Technologies. Facebook: TrichomeTechnologies Instagram: Trichome Technologies