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How to Optimize Your Structure for Odor Control

Don’t let your crop's smell cause you trouble.

Phantom

While many U.S. cities are open to having cannabis-cultivating neighbors, one element seems to bother them: odor. Not only can their complaints frustrate you, they can also lead to fines, depending on where you are cultivating. To help customize your structure for best odor control, RBI's Dan Halcomb provides some tips.

Cannabis Business Times: What types of problems does odor cause for cannabis cultivators (neighbor complaints, fines, etc.)?

Dan Halcomb, RBI.: Depending on local regulations, there may be an official penalty for detectable odor. These penalties can range from a small fine to an outright loss of your cultivator license. Even in locations without strict regulations, neighbors may be bothered by the smell; it never hurts to be a considerate member of the community. When talking to customers who live in an area where unchecked odor can result in loss of license, we always tell them to think smart when choosing their site — [in other words], don’t build near a neighborhood, but rather go outside densely populated areas to a site with land buffers.

CBT: Why is cannabis odor so difficult to control?

DH: There are many reasons odor can be an issue, including:

  • Cannabis has a strong and distinctive odor that is not easily masked.
  • Cost of odor neutralizers.
  • Supply of odor neutralizers.
  • Additional system to control and maintain. High pressure fogging systems are popular for odor control, but the nozzles used to produce fog are prone to clogging if not properly maintained. 
  • Traditional ventilation (roof or wall vents) and evaporative pad cooling both rely on high-volume air exchange to be effective. Reliably treating these massive volumes of air is quite an endeavor, both technically and financially.
  • In many other private industries where odors are a problem (think poultry farms or food processing plants), the facilities are placed far away from residential areas. A lot of these cannabis cultivation facilities are much closer to “civilization.” The negative stigma some hold against marijuana also contributes to its odor being an issue in places where other strong aromas may be tolerated.

CBT: What are some ways odor can escape from a structure (possibly cracks in retrofitted warehouses, greenhouse doors/vents)?

DH: Odor can escape through:

  • Greenhouse glazing / extrusion connections
  • Vents
  • Inside/outside equipment sealing points
  • Exhaust locations
  • Doorways
  • Any weak points in the sealing in general
  • Mechanical room exhaust

CBT: What type of RBI structure would work best to mitigate odor? And what about this structure makes it ideal?

DH: The solution has more to do with operational changes than general structure type (though some types do tend to seal a bit more snugly, with RBI’s Venlo taking the top spot among our offerings). Many greenhouses rely on natural forces for ventilation, specifically convection, which drives hot air up to the roof peaks and out through vents. Where venting is insufficient (and the climate is not overly humid), evaporative pad-and-fan cooling systems have been the go-to answer. These two methods are basic environmental functions of most greenhouses and essential systems for the facilities that use them, and they both exchange a huge amount of air. If scrubbing all this air as it exits the greenhouse is not practical or reliable, what can you do? I tend to recommend mechanical cooling, both to do away with the need for massive air exchange, and for the gained ability to finely control temperature and humidity. With mechanical cooling, growers are able to operate within a fully-sealed greenhouse. If odor is a potential crisis for your operation, consider a negative-pressure design; this negative pressure is slight and best suited for cultivation sites with strict odor regulations. Maintaining an inside air pressure lower than ambient outside pressure inhibits odor leakage through the escape points listed above. Also think about controlled exhaust ports, which concentrate air exiting the facility to locations of our choosing. This air can be passed through carbon filters and/or treated as it exits the low-volume exhaust fans for a fraction of the operational cost required to scrub the air leaving traditionally-ventilated greenhouses.