environmental control

Precision Humidity Control in Cannabis Grow Facilities

by | Jan 20, 2020

environmental control

Written by Jessica McKeil

Jessica McKeil is a cannabis writer and B2B content marketer living in British Columbia, Canada. Her focus on cannabis tech, scientific breakthroughs, and extraction has led to bylines with Cannabis & Tech Today, Terpenes and Testing, Analytical Cannabis, and Grow Mag among others. She is the owner and lead-writer of Sea to Sky Content, which provides content and strategy to the industry’s biggest brands.

In October 2019, Colorado’s commercial cannabis sector took a hit. Bonsai Cultivation issued a statewide, voluntary recall on flower, shake, trim, and pre-rolls because of possibly unhealthy levels of mold and yeast. Furthermore, only a month earlier, the state conducted random tests on 25 Denver dispensaries for mold and yeast, and 80 percent failed.

Colorado is hardly the only market where mold and fungal contamination has rocked consumer confidence. In late December 2019, headlines jolted Nevada’s cannabis market after the state closed a licensed testing facility because samples had failed secondary testing for mold, yeast, and fungus.

The cannabis economy is booming, but with the demand for ever-larger harvests, modern facilities sometimes struggle to keep the product safe and free from contamination. At every point along the supply chain, there is a risk for unhealthy pathogens to take hold and destroy the product. Controlling for humidity in the grow room, during curing and elsewhere, is essential to keeping the final product clean.

Mold in Consumer Cannabis, A Constant Battle

No matter which facility the cannabis comes from, there is always a risk of contamination. Molds, fungi, and yeasts are natural and expected components of all agriculture, indoors or out. Certain pathogens favor the very same conditions preferred by cannabis plants. Keeping these organic contaminants out of the grow room, and out of the final product, is a constant battle for the modern facility.

Moisture becomes an issue within indoor spaces during the natural growth cycle of the plants. Cannabis requires significant hydration, which it eventually expresses through a process known as transpiration. The plants express up to 90 percent of the water that enters the plant in this manner.

As the plants go through their lights-on and lights-off cycles, they “transpire” water into the environment, creating the dangerous moisture content if left unchecked. Vascular plants such as cannabis have specialized cells known as xylem, which work to raise water from the roots to the leaves and facilitate photosynthesis and cool the plant.

Small openings in the outer skin of the plants, known as stomata, allow the water stored in the plant to be evaporated and flow from the plant into the air. 

Plant transpiration increases while lights are on, but this moisture is naturally stripped by the air conditioner evaporator coil that is focused on removing the heat of those lights. The major humidity challenge comes when the plants enter the “lights out” portion of their day.

As the high heat load in the room is turned off, temperatures drop. Although the absolute moisture content may not increase, the relative humidity of the air does. At lower temperatures, the air cannot hold as much water vapor as it can when it is warmer. As a result, the water vapor begins to condense; the grow space becomes damper, and water droplets begin to form on the leaves. It becomes a perfect environment for the nasty contaminants ubiquitous in any environment to flourish.

Plus, there are additional environmental control challenges associated with transpiration beyond simply removing moisture. The transpiration rate is not constant and must be addressed rapidly when the humidity in the room begins to climb. In certain regions, where the outdoor environment is also moisture-laden, the humidity from outside air must also be taken into consideration. 

Growing anything indoors, and at scale, requires precision controls over the environment. Alongside light, temperature, and water, humidity controls are equally as critical to the health of the final harvest. Mold in the grow room can ruin a crop before harvest, but as mold issues in Colorado and Nevada have shown, it may continue to wreak havoc over products already within the supply chain.

Precision Dehumidification Control in the Modern Grow Facility

The modern grow room, no matter the scale, is responsible for creating conditions that support cannabis growth, but that prevent mold and fungi from taking over. It’s a careful balancing act, which increasingly relies on precision automated dehumidification technologies.

Today, most facilities rely on an integrated system, combining heating, ventilation, and air conditioning systems (HVAC) with additional dehumidification technology. Most HVAC systems, will, to some degree, control the environment and thus the humidity. Still, in the damp environment of an indoor cannabis facility or greenhouse, additional pieces are needed to remove excess moisture from the space.

DryGair is one of the current industry leaders, both within the cannabis grow room and within curing spaces. DryGair is the additional component commercial growers need to improve airflow and keep humidity levels in check. The standard DryGair unit is a grow room “solution that adapts a small-scale grow concept to large-scale operations,” according to a piece for MMJDaily.

The units take household dehumidifying formats to large-scale cannabis facilities. Placed strategically around the facility, DryGair units work in conjunction with other automated environmental controls and the HVAC system to remove moisture from the growing space.

Importantly, the units do so without excessive energy consumption. According to stats on the standard DG12 unit, it is capable of removing 12 gallons per house (45 liters at 64°F (18°C) and 80 percent relative humidity. What is the energy consumption per gallon (four liters)? Only one kWh of energy.

Many industrial dehumidifying brands see the need within the cannabis industry and are quickly moving to secure the market. At the time of this writing, the market potential for humidity control for indoor and greenhouse cannabis is exponential. STULZ is one such company targeting cannabis growers, and the company has already introduced units specifically geared towards grow rooms and vertical farming spaces.

Working alongside medical cannabis experts, STULZ has engineered a custom precision air conditioning and humidification solution suitable for the commercial cannabis space. It takes into account the specific environment and conditions required in cannabis, including UV-C lighting to counter microscopic pests, the need to control humidity spikes during lights off periods, and remote monitoring capabilities.

Robert Danko, in a piece for PharmOut, has also suggested the usefulness of introducing desiccant dehumidification methods within indoor cannabis facilities. Desiccant dehumidification is a common occurrence within pharmaceutical facilities.

According to Danko, “A desiccant system utilizes a chemical (desiccant) to absorb liquid (e.g., water) to reduce the humidity in the surrounding environment.” Danko explores a desiccant solution made from sodium chloride or lithium hydride, which would have a secondary benefit of scrubbing mold, fungi, and yeast from the environment.

The system is capable of regeneration by applying heat to express the moisture from the desiccant. No additional cooling is required, as the desiccant system can work at room temperature, and will significantly reduce energy consumption compared to conventional greenhouse dehumidification controls.

Better Dehumidification Control Needed for Growing Commercial Landscape

As the industry expands, so too must the technology supporting it. Historically, farmers may have relied on imprecise dehumidifying units borrowed from residential spaces, but the industry has long since outgrown these over-simplified technologies.

The industrial-sized indoor grow spaces now common in cannabis must incorporate humidity control within the original design or risk disaster. HVAC systems must work in conjunction with additional precision dehumidification controls, to effectively regulate grow room moisture. Although it’s nearly impossible to reduce mold, fungi, and yeast risk to zero within any agricultural space, new technologies are making it easier.