Vintners have known for centuries that every step in the winemaking process—from cultivation and harvest techniques to fermentation, aging and bottling—has immense impact on the quality and value of the final product.
And that same level of scrutiny is now being applied to cannabis production.
As someone who has worked in the consumer-packaged goods (CPG) space for decades, I’ve been interested in finding out how post-harvest storage and packaging affect the quality and value of cannabis flower. After digging into the issue some more, storage conditions and humidity levels have indeed come into focus as major factors, beyond just the challenges of preventing mold.
Weighty Matters
I enlisted my research team at Boveda, which has studied moisture control in all manner of manufactured and natural CPG products, to look closer at what’s happening with cannabis once it leaves the cultivation room. There’s not a lot of research on cannabis storage—we checked—and so we explored this aspect further. We were frankly surprised by what a big effect evaporation has on quality and how this is playing out on the retail level.
We suspected moisture loss could affect the bottom line too, and so we did some number-crunching.
It’s well understood that the weight of cannabis flower directly correlates with its profitability—the heavier the yield, the higher the market value. Here’s what our analysis found: A mere 5% dip below the optimal relative humidity (RH) storage environment eliminates six pounds per every 1,000 pounds of cannabis flower. At $5 per gram wholesale, that works out to upwards of $13,500 in lost revenue—and that’s with just a 5% drop in RH below the target range of 55-65% established by ASTM International, an independent industry standards organization.
We also purchased flower at retailers in multiple state markets and commissioned a lab to test the samples, which revealed that most strains sold today are well below the optimal RH range (55-65%). Regardless of fluctuating wholesale prices, when you do the math it’s clear that tens of thousands of dollars in revenue are simply evaporating into thin air.
Why So Dry?
Historically, cultivators, processors and packagers have emphasized keeping flower below a particular humidity “ceiling” for a reason: Flower that’s too moist is prone to hazardous mold and microbial growth, so it’s understandable that many operators err on the side of being overly dry.
The misconception that cannabis flower can be “rehydrated” is another cause of dryness damage. But this method irrevocably damages the quality of the flower through trichome damage.
The fine outgrowths, referred to as trichomes, house the majority of the plant’s resin
Those delicate plant structures that house the all-important cannabinoids and terpenes become brittle and fragile when stored in an overly dry environment, and are prone to breaking off from the flower; they cannot not be recovered even if the flower is later rehydrated.
When trichomes are compromised, terpenes responsible for the aroma, taste and scent of cannabis also can evaporate. Overly dried-out cannabis doesn’t just lose weight and efficacy—it loses shelf appeal, which is particularly risky in today’s market.
Today’s consumers have an appreciation for how premium flower should look, smell and taste. Rehydration cannot put terpenes back in the flower, nor can it re-attach trichomes to the flower, which is why preservation of these elements is so key.
Cannabis Humidity Control
Cured cannabis flower can remain in storage potentially for months prior to sale or consumption. By the time it reaches the end consumer, much of the cannabis sold in regulated environments in the U.S. and Canada has suffered from dry damage.
Rows of cannabis plants drying and curing following harvest
There are various humidity controls available for cannabis cultivators: desiccants that absorb water vapor; mechanical equipment that alters RH on a larger scale; or two-way humidity-control packets designed for storage containers.
In the CPG sector, with other moisture-sensitive products such as foods and electronics, we’ve seen that employing humidity controls will preserve quality, and cannabis flower is no different.
Saltwater-based humidity control solutions with two-way vapor-phase osmosis technology automatically add or remove water vapor as needed to maintain a constant, predetermined RH level and ensures a consistent level of moisture weight inside the cannabis flower.
Here’s one more notable finding we discovered in our storage research: Third-party lab tests commissioned by Boveda showed cannabis stored with humidity control had terpene and cannabinoid levels that were 15% higher than cannabis stored without.
Cannabis stored within the optimal humidity range maximizes all the qualities that attract and retain customers. Similar to wine-making, when cannabis cultivators focus on quality control they need to look beyond the harvest.
There’s a better way to design HVAC for cannabis grow rooms, and it may seem a little odd at first.
Central chillers are a tried-and-true solution for projects requiring large refrigeration capacity. They’re found in college campuses, hospitals, office buildings and other big facilities.
While central chillers are a good default for most large-scale applications, they fall short in this industry. Grow rooms, with their need for tight, variable conditions and scalable, redundant infrastructure, have HVAC requirements that the central chiller model simply can’t deliver on.
Let’s unpack the shortcomings with the central chiller in this niche and explore some possible solutions.
What’s Wrong With Chillers?
Building a scalable HVAC system is essential for the cannabis industry as it continues to ramp up production in the U.S. and Canada.
Many growers are building their large facilities in phases. In Canada, this is common because growers must have two harvests before they can receive a production permit, so they build just one phase to satisfy this requirement and then build out the facility after the government’s approval.
This strategy of building out is less feasible with a central chiller.
Indoor cultivator facilities use high powered lights that give off heat, requiring an efficient air cooling system.
A chiller and its supporting infrastructure are impractical to expand, which means it and the rest of the facility needs to be built to full size for day one, even though the facility will be in partial occupancy for a long time. This results in high upfront capital costs.
If the facility needs to expand later down the road, to meet market demand for example, that will be difficult because, as mentioned, it’s expensive to add capacity to a central chiller.
Additionally, the chiller creates a central point of failure for the facility. When it goes down, crops in every room are at risk of potentially devastating loss. Grow rooms are unusual because of their requirement for strict conditions and even a slight change could have big impact on the crop. Losing control due to mechanical failure could spell disaster.
One Southern Ontario cannabis grower met with some of these issues after constructing their facility, which uses a central chiller for cooling and dehumidification. The chiller was built for full size, but the results were disappointing as early as phase one of cultivation. While sensible demands in the space are being easily met, humidity levels are out of control – flowering rooms are up to 75% RH.
Humidity is one of the most important control aspects to growers. Without a handle on it, growers risk losing their entire crop either because there’s not enough and the plants dry out, or there’s too much and the plants get mold disease. This facility has fortunately not yet reported serious crop issues but is mindful of the potential impact on harvest quality.
By going unitary, capital costs scale on a linear basis.If tight control over humidity is what you need, then a chilled water system needs very careful consideration. That’s because typical chiller system designs get the coils cold enough to lower the air temperature, but not cold enough to condense water out of the air as effectively as a properly designed dehumidifier coil.
A chilled water system capable of achieving the coil temperatures needed for adequate dehumidification in a typical flower room will also require full-time reheat to ensure that air delivered to the plants isn’t shockingly cold — either stunting their growth or killing them altogether. This reheat source adds complexity, cost and inefficiency which does not serve growers well, many of whom are under pressure from both utilities and their management to minimize their energy usage.
How Do Unitary Systems Solve These Problems?
Compared to central chillers, a unitary setup is more agile.
A facility can commence with the minimum capacity it needs for start-up and then add more units in the future as required. They’re usually cheaper to install than a central system and offer several reliability and efficiency benefits as well.
The real business advantage to this approach is to open up the grower’s cash flow by spreading out their costs over time, rather than a large, immediate cost to construct the entire facility and chiller for day one. By going unitary, capital costs scale on a linear basis.
One of the flowering rooms in an indoor set up (Image: Tall Trees LED Company)
Growers can have more control over their crop by installing multiple units to provide varying conditions, room-by-room, instead of a single system that can only provide one condition.
For example, flowering rooms that each have different strains of crop may require different conditions – so they can be served by their own unit to provide variability. Or, rooms that need uniform conditions could just be served by one common unit. The flexibility that growers can enjoy with this approach is nearly unlimited.
Some growers have opted for multiple units installed for the same room, which maximizes redundancy in case one unit fails.
A cannabis facility in the Montreal area went this direction when building their HVAC system. Rather than build everything in one shot, this facility selected a unitary design that had flowering rooms served independently by a series of units, while vegetation rooms shared one. The units were sized to provide more capacity than currently required in each room, which allows the grower to add more plants and lighting in the future if they choose.
This facility expects to build more grow rooms in a future phase, so it was important to have an intelligent system that could accommodate that by being easy to add capacity to. This is accomplished by simply adding more units.Multiple, small systems also have a better return-on-investment.
The grower, after making a significant investment in this facility, was also averse to the risk of losing crop due to mechanical failure, which is why they were happy to go with a system of independent grow room control.
Multiple, small systems also have a better return-on-investment. Not only are they easier to maintain (parts are easier to switch out and downtime for maintenance is minimal) but they can actually be more efficient than a large, central system.
Some units include heat recovery, which recycles the heat created by the dehumidification process to efficiently reheat the unit’s cold discharge air and keep the space temperature consistent, without needing expensive supplementary heaters. There’s also economizer cooling, which can be used to reduce or even eliminate compressor usage during winter by running the unit on dry outside air only.
Demand for cannabis continues to increase and many growers are looking to expand their businesses by adding new facilities or augmenting existing ones. Faced with the limitations of the traditional chiller system, like the lack of flexibility, scalability and redundancy, they’re looking for an intelligent alternative and the unitary approach is earning their trust. It’s expected this option will soon become the leading one across North America.
The outside environment can vary widely depending on where your facility is located. However, the internal environment around any activity can have an effect on that activity and any personnel performing the activity, whether that’s storage, manufacturing, testing, office work, etc. These effects can, in turn, affect the product of such activities. Environmental control strategies aim to ensure that the environment supports efforts to keep product quality high in a manner that is economical and sensible, regardless of the outside weather conditions.
For this article, let us define the “environment” as characteristics related to the room air in which an activity is performed, setting aside construction and procedural conditions that may also affect the activity. Also, let us leave the issue of managing toxins or potent compounds for another time (as well as lighting, noise, vibration, air flow, differential pressures, etc). The intent here is to focus on the basics: temperature, humidity and a little bit on particulate counts.
Temperature and humidity are key because a non-suitable environment can result in the following problems:
Operator discomfort
Increased operator error
Difficulty in managing products (e.g. powders, capsules, etc)
Particulate generation
Degradation of raw materials
Product contamination
Product degradation
Microbial and mold growth
Excessive static
USP <659> “Packaging and Storage Requirements” identifies room temperature as 20-25°C (68-77 °F) and is often used as a guideline for operations. If gowning is required, the temperature may be reduced to improve operator comfort. This is a good guide for human working areas. For areas that require other specific temperatures (e.g. refrigerated storage for raw materials), the temperature of the area should be set to those requirements.
Humidity can affect activities at the high end by allowing mold growth and at the low end by increasing static. Some products (or packaging materials) are hydroscopic, and will take on water from a humid environment. Working with particular products (e.g. powders) can also drive the requirement for better humidity control, since some powders become difficult to manage in either high or low humidity environments. For human operations without other constraints, a typical range for desirable humidity is in the range of 20 to 70% RH in manufacturing areas, allowing for occasional excursions above. As in the case of temperature, other requirements may dictate a different range.
In some cases, a locally controlled environment is a good option to reduce the need to control the room environment as tightly or to protect the operator.
In a typical work environment, it is often sufficient to control the temperature, while allowing the relative humidity to vary. If the humidity does not exceed the limits for the activity, then this approach is preferred, because controlling humidity adds a level of complexity (and cost) to the air handling. If humidity control is required, it can be managed by adding moisture via various humidification systems, or cooling/reheating air to remove moisture. When very low humidity is required, special equipment such as a desiccant system may be required. It should be noted that although you can save money by not implementing humidity control at the beginning, retrofitting your system for humidity control at a later time can be expensive and require a shutdown of the facility.
Good engineering practice can help prevent issues that may be caused by activities performed in inappropriately controlled environments. The following steps can help manage the process:
Plan your operations throughout your facility, taking into account the requirements for the temperature and humidity in each area and know what activities are most sensitive to the environment. Plans can change, so plan for contingencies whenever possible.
Write down your requirements in a User Requirement Specification (URS) to a level of detail that is sufficient for you to test against once the system is built. This should include specific temperature and RH ranges. You may have additional requirements. Don’t forget to include requirements for instrumentation that will allow you to monitor the temperature and RH of critical areas. This instrumentation should be calibrated.
Solicit and select proposals for work based on the URS that you have generated. The contractor will understand the weather in the area and can ensure that the system can meet your requirements. A good contractor can also further assist with other topics that are not within the scope of this article (particulates, differential pressures, managing heating or humidity generating equipment effects, etc).
Once work is completed, verify correct operation using the calibrated instrumentation provided, and make sure you add periodic calibration of critical equipment, as well as maintenance of your mechanical system(s), to your calibration and maintenance schedules, to keep everything running smoothly.
The main point is if you plan your facility and know your requirements, then you can avoid significant problems down the road as your company grows and activity in various areas increases. Chances are that a typical facility may not meet your particular requirements, and finding that out after you are operational can take away from your vacation time and peace of mind. Consider the environment, its good business!
Maintaining an environment that supports cultivation and keeps plants healthy is not an easy task. In cannabis growing, there are a variety of factors that greenhouse managers and personnel must monitor to ensure that their plants are in a healthy environment that fosters growth and development. Temperature, humidity, lighting and CO2 levels are a few of the conditions that need to be tailored to each cannabis greenhouse operation. However, it can be difficult to constantly monitor the status of your equipment and the greenhouse environment, especially after hours or during the off-season.
A remote monitoring system that’s properly selected and installed can help greenhouse managers keep their cannabis plants healthy, multiply their yields and increase return on investment. This type of system also helps operators identify patterns and trends in environmental conditions and get insight into larger issues that can prevent problems before they arise.
Cloud-based monitoring system base unit in weatherproof enclosure
Here are some tips on key conditions to monitor and what you need to consider when selecting a monitoring system for your cannabis greenhouse operation:
Temperature
Temperature plays a crucial role in any cannabis grow operation. The climate in your greenhouse must be warm enough to nurture photosynthesis and the growth of cannabis plants. Setting the incorrect temperature will significantly impact the potential yield of the plant and the rate at which it develops. A temperature too low will slow the growth of the cannabis, but too hot can lead to heat stress for your plants. The ideal temperature for a standard greenhouse is between 70 and 80 degrees Fahrenheit. However, depending on the stage of plant and desired growth densities, the temperature of the greenhouse needs to be adjusted accordingly.
Humidity Levels
Humidity directly affects plant photosynthesis and transpiration, so controlling humidity is vital in greenhouse growing. The ideal relative humidity (RH) for cannabis growth is around 60%. A low humidity level can cause water to evaporate too quickly for photosynthesis, while a humidity level that is too high can cause poor growth and possible mold and fungal disease. Monitoring the moisture content in the air of your greenhouse will help the plants during the transpiration process, increasing absorption of nutrients and overall health of the cannabis.
Lighting
Your cannabis may be getting an abundance of natural light during the summer months, but maintaining adequate sunlight during the winter months can be a challenge. As a solution to this, many greenhouse managers equip their facilities with additional lights to supplement natural light during off-seasons or off-hours. To achieve the best possible yield, a cannabis plant in the budding stage should receive twelve hours of light each day, while other stages could require additional lighting. For example, the growth stage could require your cannabis to be exposed to sunlight for up to eighteen hours a day.
CO2 Levels
Like any other plant, cannabis requires CO2 to breathe. Greenhouse managers must set and monitor the CO2 levels in their facility to make sure that there is an adequate amount for the plants to develop, grow and be healthy. The amount of carbon dioxide required for your cannabis depends of the size of the facility and the amount of light the plants are receiving. However, a standard grow area for cannabis can maintain a CO2 range from 1000 to 1500 parts per million (PPM). A level below that threshold can result in slower growth of the plants, while a level above would lead to unused and wasted CO2.
Soil moisture sensor
Irrigation and Soil Moisture
One way to ensure a good yield from your cannabis is to water it regularly and monitor your soil moisture. Overwatering your plants can have the same effect, if not worse, than letting the soil become too dry. Plants’ roots need oxygen to survive, unlike leaves that breathe CO2, and when the soil is waterlogged the roots can’t provide their function. The lack of oxygen interferes with the roots’ nutrient uptake and photosynthesis causing the cannabis plant to wilt. The exact moisture content of the soil depends on the size of your greenhouse, temperature and humidity. Whether you hand water or are using a drip irrigation system, being aware of your soil moisture is vital to the long-term health of your cannabis.
Air Circulation
Your greenhouse environment should mimic the ideal conditions in which cannabis plants flourish. With an indoor facility, you have the ability to control air circulation by venting hot air out and blowing fresh air in. Creating a circulation of air inside your greenhouse will increase your cannabis plant’s growth speed and yield. Additionally, an exhaust system helps control the temperature and humidity, while also preventing the invasion of mold and pests that thrive in hot, stagnant air.
Greenhouse Security
When growing something of value, like cannabis, there will always be a threat of intruders. Whether your greenhouse is in a populated area or around hungry wildlife, any intruder could be detrimental to your overall yields and profit. Remote monitoring systems can give you peace of mind and instantly alert you when there is an unwanted presence in your greenhouse.
Knowing all the possible threats to your cannabis greenhouse helps you evaluate your specific needs, and ultimately identify the proper remote monitoring system.
Selecting the Right Monitoring System
Other factors to consider when choosing a monitoring system right for your operation include:
Base unit and sensors
Wireless or hardwired sensors
Communications to your site (Phone, cellular, Wi-Fi, etc.)
Alarm notification
Programming and status checks
Data logging
Return on investment
Base Units and Sensors
Each condition in your greenhouse that you want to monitor requires its own input on the base unit of the monitoring system. You must match your needs with the number of inputs available. A good fit for a smaller cannabis greenhouse may be a lower-cost, non-expandable monitoring system. However, larger facilities have many monitoring points and more people to alert when there’s a problem. If your cannabis operation is poised for growth, purchasing an expandable system could add value to the initial purchase because you wouldn’t have to replace your entire system in the future.
Your monitoring system should also have an internal rechargeable battery backup to ensure continuous monitoring and alerts in the event of a power outage. It is also recommended to have each base unit in a sheltered enclosure to protect it from moisture, dirt and other hazards.
Placement of sensors is also crucial. For example, temperature sensors in your greenhouse should be placed throughout the facility. They should be next to your thermostat and in the center of your greenhouse, preferably away from direct sunlight.
Wireless or Hardwired Sensors
Remote monitoring systems offer the option to have sensors hardwired directly to the base unit or sensors wirelessly connected. A hardwired monitoring system connects the sensors to the base device with wires. Generally, trenching long distances for wires is time consuming and costly. So alternatively, a wireless system uses built-in radio transmitters to communicate with the base unit. Some monitoring systems can accommodate a combination of hardwired and wireless sensors.
Communications to Your Site
Monitoring devices that use cellular communications must be registered on a wireless network (like Verizon or AT&T) before you can send or receive messages. Because cellular devices perform all communications over a wireless network, it is important that there be sufficient signal strength at the greenhouse. It is a good idea to check the signal quality in the area before purchasing a cellular product. If the cellular network has less than desirable coverage, it is possible to install an external antenna to help increase cellular signal.
Alarm Notifications
When monitoring systems identify a change in status, they immediately send alerts to people on the contact list. If you don’t want all of your personnel to receive notifications at the same time, certain devices can be programmed to send alerts in a tiered fashion. It is important to consider the reach of the communications, so that you’ll be notified regardless of your locations. Multiple communications methods like phone, email and text provide extra assurance that you’ll get the alert. Also, note of the number of people the system can reach and if the system automatically cycles through the contact list until someone responds. Make sure the system allows for flexible scheduling so that it doesn’t send alarms to off-duty personnel.
Programming and Status Check
If you’re responsible for maintaining a commercial greenhouse facility, you want a system that will provide real-time status of all monitored conditions on demand. There are a few different ways to access your sensor readings. Options include calling to check status, viewing a web page, either on a local network or on the cloud, or accessing the information via an app on your mobile device. With a cloud-based system, the devices supervise themselves. This means if the internet or cellular connection goes down, the device will send an alarm to alert the appropriate personnel.
If you don’t select a cloud-based system, you will be limited to logging in through a local area network, which will allow you to make programming changes, access status conditions and review data logs. If internet connectivity is not available at your location, you will want to choose a cellular or phone system rather than Ethernet-based option.
Data Logging
Sample greenhouse monitoring data log
Data history is valuable in identifying patterns and trends in your cannabis greenhouse conditions. Manually monitoring and recording environmental parameters takes a significant amount of personnel time and detracts from other important workplace demands. However, many monitoring systems automatically save information, recording tens of thousands of data points, dates and times. Cloud-based logging provides an unlimited number of records for users to view, graph, print and export data trends.
Analyzing data samples may lend insight to larger issues and prevent problems before they arise. For example, if the data log shows power fluctuations occurring at a regular time, it could be indicative of a more serious problem. Or, if the data shows signs of a ventilation fan or supplementary lighting beginning to malfunction, they can be repaired or replaced before total failure occurs.
Return On Investment
When deciding how much you should pay for a remote monitoring system, tally up the entire cost, fully installed with additional peripherals and sensors and any labor fees for installation. Then consider the value of your cannabis plant inventory and greenhouse equipment. Finally, factor in the cost of downtime, should an environmental event shut down your operation for a period of time.
Final Thoughts
Choosing the right greenhouse monitoring system and sensors could mean the difference between life and death for your cannabis plants. Understanding the conditions you need to watch and monitoring systems’ capabilities are they best way to protect your investment.
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It’s well understood that the weight of cannabis flower directly correlates with its profitability—the heavier the yield, the higher the market value. Here’s what our analysis found: A mere 5% dip below the optimal relative humidity (RH) storage environment eliminates six pounds per every 1,000 pounds of cannabis flower. At $5 per gram wholesale, that works out to upwards of $13,500 in lost revenue—and that’s with just a 5% drop in RH below the target range of 55-65% established by ASTM International, an independent industry standards organization.
