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dry cannabis plants

Moisture Matters: Why Humidity Can Make or Break a Cannabis Cultivator’s Bottom Line

By Sean Knutsen
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dry cannabis plants

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.

trichome close up
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.

dry cannabis plants
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.

Why the Central Chiller Isn’t So Central to Grow Room HVAC

By Geoff Brown
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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.

solsticegrowop_feb
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.

Talltrees
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.

control the room environment

Environmental Controls: The Basics

By Vince Sebald
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control the room environment

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.

control the room environment
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!