Growing Cannabis Using Ozone for Disinfection

31st Mar 2021

With the passage of recent legislation in many states, combined with over two decades of legal use in Canada, the interest in cannabis production amongst private growers is at an all-time high. But what role does ozone play in cannabis production?

As of early 2021,15 states and the District of Columbia had legalized cannabis use for recreational purposes, and 33 states have approved cannabis use for medicinal purposes. There are nearly 250,000 cannabis industry jobs, and the market size is expected to surpass $80 billion by 2027. The industry is thriving!

But with growth comes added demands on growers as well as added government regulations that affect other agricultural environments. Growers need to address microbial contamination, including aspergillus, E. coli, molds, and other contaminants. To conform to these regulations, cannabis producers need to assess which disinfectant options are available. That assessment has led to greater awareness of the effectiveness of ozone for the industry.

How effective is ozone?

Ozone is an incredibly powerful oxidizing agent. It is 2.5 times more effective than chlorine at tackling mold, pathogens, fungi, and bud rot, and its effectiveness is backed by research. A study published in the American Journal of Infection Control found that “an ozone dosage of 25 ppm [parts per million] for 20 minutes, with a short burst of humidity” was able to inactivate most of the bacteria present “both in a laboratory test system and simulated field conditions. In many cases, complete eradication was achieved.” The researchers concluded that an “ozone generator can provide a valuable decontamination tool for the removal of bacteria in many institutional and communal settings, including hospitals and other health care institutions.”

Antibacterial properties are just one of the benefits of ozone generators. The most appealing to cannabis growers is that ozone generators work as an antifungal device, as demonstrated in a study by researchers at The Journal of the International Ozone Association. The study showed that one or two cycles of treatment of 35 ppm for 20 minutes with a short burst of humidity inactivated most of the 13 separate species of environmental fungi on a variety of surfaces.

However, those treatment levels are still unsafe for humans to be present. The National Institute for Occupational Safety and Health recommends an exposure limit to ozone of 0.1 ppm and considers levels of 5 ppm or higher “immediately dangerous to life or health.” We strongly discourage using high levels of gaseous ozone while humans are present! Fortunately, that is not your only option.

How is ozone used in cannabis production?

There are many applications and potential uses for ozone in the cannabis industry, both in growing and processing. And most of these options pose little to no health risk to growers, especially in aqueous form.

Aqueous Ozone Use

  • Irrigation and Hydroponic – Cannabis can be grown in many ways, but each requires some form of irrigation. Ozone can be used to treat well water to remove harmful bacteria and other pathogens, but also harmful minerals that may be present. Ozonated water is also a great way to cleanse a hydroponic system without having to drain it down and spend hours disinfecting everything. Pumping ozone into water can clean entire hydroponic systems as the ozone molecules will bind to harmful pathogens in the water. You could even use the ozone generator during a grow cycle, to purify both the water and root systems at the same time, avoiding root rot. And as ozone is more soluble into water than oxygen, and ozone will revert to oxygen naturally in water, adding ozone to your water will naturally increase dissolved oxygen levels in that water.
  • Surface Sanitation – Dissolved ozone can be used for sanitation or surfaces, equipment, and even plants. This is a common application in many food processing environments, and numerous studies have confirmed its effectiveness. Dissolved ozone in water for surface sanitation is safe, there are no harmful side effects to humans or plants from ozone in water. However, if set-up incorrectly ozone in water can off-gas, and in its concentrated gaseous form can cause danger to humans and plants.

Gaseous Ozone Use

  • Exhaust and Odor Control - Place ozone generators on the exhaust pipes of a ventilation system to capture evaporated terpene molecules. Terpenes are the compounds responsible for giving marijuana its sweet, seductive aroma. If discretion is the name of the game, then consider adding an ozone generator to the exhaust. Any ozone molecules escaping outdoors would be quickly dispersed.
  • Room Disinfection - Ozone gas can be used in rooms to inactivate airborne pathogens or as a supplement treatment after aqueous ozone is used for surface sanitation. This will ensure all pathogens in the room are destroyed before starting a new crop, or between processing batches of harvested product. The room must be empty of plants and people for effective shock treatment. Ozone monitors can be used to control ozone levels and ensure the room is safe when finished – generally a few hours. This type of treatment is also an effective way to eliminate offensive organic odors that may develop during growing, cultivation, or processing.
  • Plant Disinfection - In most states, the final harvested product must meet specific mold, and bacteria standards to be sold to the end-user for consumption. Ozone can be used to provide disinfection for this final product to meet the most stringent mold and bacteria standards.

Careful - too much ozone can damage cannabis plants

Even if you could make sure that proper controls were in place to remove the potential harm to humans caused by ozone, too much ozone can potentially hurt plants. Excessive levels of ozone can inhibit a plant’s ability to produce chlorophyll, an essential part of photosynthesis. The effect is the death of healthy cells, which will inevitably lead to an inability to produce buds.

In any application, it is imperative to follow the guidelines provided with each Ozone Solutions generator and monitor. If you have any questions about using ozone in your cannabis operation, or you want to develop a system to match your specific needs, please contact us.