Surviving the Commoditization of Cannabis
As the cannabis supply increases and the industry regulations become stricter, with more prevalent testing for both medical and recreational grade, producers of cannabis should become aware of the issues that can make or break them. Growers are tasked with keeping the cost of production reasonably low while battling fungal contamination. To achieve standardized purity, many producers are turning to automation to control growth parameters, thus minimizing labor and human error. Another cost saving measure is the use of LED lighting to reduce energy. These are good first steps, but they are hardly enough to make a dent in the cost of production or in the mitigation of disease. In fact, some cost saving methods contribute to the risk of fungus in the crop. In this article I discuss how controlling the Psychrometrics can address these challenges.
The biggest opportunity for cost savings is Heating, Ventilating and Air Conditioning (HVAC) energy. Generally speaking, the HVAC system regulates the environment by adding and removing heat (sensible load) and moisture (latent load). The sensible and latent loads are two independent variables that affect the quality of the crop and the propensity for fungus growth.
Lights add sensible load. LEDs lights add less sensible load than traditional HPS and HID lights, thereby reducing lighting costs. However, this is not a sufficient solution, because using LED lights with the traditional HVAC systems exacerbates the system’s inability to control the moisture (latent load). It is the latent load that drives all phases of cannabis production.
The biggest challenge for the HVAC is when the lights are off, or the sun is down. That is when sensible load must be artificially added to the system to compensate for the inefficient, comfort cooling methods employed to remove moisture. Not only is this very energy intensive but it creates conditions conducive to fungal growth, regardless of the microclimate of the cultivation and processing location. Due to the nature of the cannabis plant the potential for fungus is as bad in a dry desert climate as it is in a humid climate. In Israel, for example, where the climate is apparently ideal, they use light deprivation in ventilated greenhouses and still lose 20% - 50% of the crop to mold.
Growers who understand, and fear, the danger of fungus attempt to maintain environmental conditions that are outside of the plant’s “Comfort Zone”. Cannabis wants to be warmer in the light and cooler in the dark, with humidity always controlled to maintain a constant Vapor Pressure Difference (VPD). VPD is the difference in the vapor pressure of the environment vs. that at the leaf surface, which drives the plants’ transpiration. Like all plants, cannabis transpires for a number of very important reasons. It is done for temperature control - it is how the plant cools itself and regulates its own temperature. It is also how plants draw minerals and nutrients from the roots. As water is released through the leaves, the plant draws more from the roots, allowing for the absorption of nutrients from the soil. Finally, transpiration is how cannabis plants get the carbon dioxide they need out of the air – plants open their stomata to let water vapor out, and in the process carbon dioxide gets in. If you are injecting CO2 into the air without controlling the humidity you could be wasting money.
The process of transpiration interacts with the atmosphere of the cultivation environment. During transpiration, plants release water vapor into the air. This process functions along the same lines as osmosis – the water levels inside and outside the plant will seek equilibrium. This means that when humidity in the growing space is low, plants will rapidly transpire. When humidity in the space is high, plants will transpire at a much slower rate. It should be noted that cannabis plants have a “humidity” rating of pretty much 100%, so they will always transpire. This is okay as it is an essential part of the plant’s functioning. However, for optimal growth, the plant requires precise environmental control.
If the humidity is too low, then cannabis plants are going to do a lot of transpiring and it will play havoc with their transpiration systems. They will lose a lot of water and begin to exhibit the damage usually caused by dryness – stunted new leaves, shriveled older leaves and dying flowers. Oftentimes, growers compensate for low humidity by over irrigating, which can lead to nutrient burn. This also wastes water, another precious and often expensive resource.
High humidity has its own perils. In a grow room with excessive humidity, plants are susceptible to fungal disease, mold, mildew, bud rot, and root rot. However, these plants thrive in higher grains of moisture and temperatures. In addition, they may not receive the nutrients required due to the lack of transpiration. The trick, which is no trick at all, is to maintain homogeneous conditions above the dewpoint. The dewpoint is the temperature at which water will condense out of the air and it is contingent on the absolute moisture content of the air. Many people use Relative Humidity as a control parameter to ascertain optimal conditions in the grow room environment. But Relative Humidity is really meaningless. The key environmental parameters for healthy, disease-free plants are the absolute water content (ὠ), the dry bulb temperature (Tdb), and the dewpoint (Tdp). The humidity of a cannabis grow room plays a large part in how plants function. It can affect the growth and final yield as well as having implications for the spread of disease, mold and mildew. Understanding exactly what plants need and how to make sure they have it, will assure growers that their cannabis crop will be of the utmost quality and consistency.
Growers who learn to modulate temperature in a controlled manner will mitigate the propensity for fungal growth and will see the following additional advantages: The energy will be massively reduced, the size of the equipment required will be smaller (and will cost less) and the humidity/VPD will be easier to control.
Drying & Curing Solutions
Humidity affects cannabis plants throughout their entire life cycle, including the drying and curing stages. The question is, why harvest and then hang to dry? Now that we understand the plant physiology, we should realize that the crop can be dried to perfection overnight prior to harvesting. The Psychrometric conditions of the room (ὠ, Tdb, and the Tdp) can be simply reset and the irrigation and lights turned off. The plants will seek equilibrium with the environment and dry to the precise desired moisture content overnight. By morning, they will be ready to harvest, trim and cure. Less space is needed because there is no need for a drying room. Less time is needed because you are controlling the process. Less time and space mean lower cost. Of course, this is an industrial process that requires precise environmental control, which cannot be achieved with the status quo of comfort cooling equipment. Nevertheless, this process need not cost more. While some of the industrial process equipment may be more expensive, the cost is off-set by equipment that is no longer needed along with a c.50% reduction is energy. Hence, the Life Cycle Cost (LCC) is greatly reduced and the Net Present Value (NPV) seriously increased.
Curing is another phase that, when treated as an industrial process, can be accomplished in less time and with better results. It is important to retain all of the terpenes through the drying and curing procedures. Terpenes are Volatile Organic Compounds (VOC). Volatility is the tendency of a substance to evaporate at normal temperatures. To keep those compounds in the plant, we must control the psychrometric properties of their environment. In the controlled environment, the biological processes required for curing will still occur and will still require time. The difference is that it will take less time and remain fungus-free while retaining the terpenes.
The Cannabis Industry needs more conferences that provide scholarly information to educate industry operators and decision makers. Unfortunately, many of the current conferences focus on product promotion under the guise of educational sessions. Genuine professional organizations, while they have expos at their events, present scholarly information absent of product promotion. They are out there, but unfortunately, they are few and far between. To gain credibility as well as to prosper, the industry must seek a more professional approach that is science driven. We must encourage innovative critical thinking as we are progressing towards efficiency and sustainability in the cannabis industry. As an engineer and an educator, I am an avid advocate for challenging the status quo. I am passionate about generating solutions for what I believe are going to be the defining issues of the industry: the ability to produce non-contaminated crops of consistent quality at competitive cost of production. We must recognize that comfort cooling systems that work well in office buildings, hospitals and other structures, are not efficient in the cultivation world. As Nadia Sabeh, said, “Plants are not people”. We must not be afraid to change the way we think about environmental control of cannabis facilities.
To learn more about how your facility can achieve precise environmental control using half the energy, contact Bryan at email@example.com.
You can read more about the Psychrometrics of Cannabis here.