In April 2017, Cannabis Business Times published what remains one of my most popular columns: “Master the Art of Drying and Curing Cannabis.” While much of the information it contains remains valid, nearly a decade of technological, scientific, and economic advancement has happened since it first ran.
Cannabis legalization at the state level in the U.S. and at federal levels in other jurisdictions drove investments in innovative companies whose products enhance all methods of commercial cannabis production.
So, to build on that 2017 article, we examine just a few of the technologies advancing the process of drying and curing cannabis.
Drying and Curing Racking
In 2017, there were few tools specifically designed to facilitate drying and curing cannabis at a commercial scale. For instance, few purpose-built hang-dry systems were available. Many growers still utilized a clothesline system to hang dry their flower. Some of the more engineering-savvy growers customized huge rack systems from traditional agriculture to process massive hemp harvests.
Today, many companies manufacture incredibly efficient hang-dry systems for small-, medium-, and large-scale applications that offer growers options on how to hang the plants or branches for drying. For example, in lieu of hang-drying, some companies offer stackable bins that allow easy access to each batch. Others offer movable vertical hanging units that allow growers to maximize space usage.
Advancements have also been made on the curing side. Instead of plastic storage bins purchased at hardware stores, cannabis growers today have dedicated containers and advanced systems to control the environmental conditions within them. For example, some suppliers have designed barrels that can be stacked sideways to allow them to be rolled and turn over their contents, with custom racks offered that are capable of holding multiple barrels.
Adding environmental control monitors to curing containers can allow growers to “burp” the container when gasses need to be released. These systems are capable of measuring temperature, humidity, as well as CO2 in the container environment. Once conditions hit certain grower-designated thresholds, some units even automatically vent the unwanted gases and moisture, helping maintain the optimal water activity to ensure the cannabis stays fresh and sticky.
HVAC and Environmental Control
In 2017, advanced commercial cannabis facilities utilized HVAC systems to facilitate the drying and curing of their crops, using the same systems as their cultivation rooms.
That proved a workable solution—ultimately, the goal of drying cannabis is to ensure bacterial and fungal pathogens do not develop while retaining proper moisture and terpene content.
Unfortunately, to minimize the potential to fail microbial and fungal testing (and remove what is often seen as a production bottleneck), some commercial cultivators purposefully overdry their cannabis as fast as possible. This practice damages delicate trichome heads, releasing those volatile terpenes into the environment. A good rule of thumb is if you smell cannabis in your drying or curing environments, you are essentially losing flavor and aroma.
Preserving trichrome integrity throughout the cultivation, harvesting, drying, and curing stages is paramount as it contributes to the potency and quality of the finished product. When trichome heads remain uncompromised, they can better preserve valuable cannabinoids and terpenes and minimize oxidation damage. As a trichome oxidizes, the color of its contents darkens, which can influence the final color of the consumer-ready flower and any extract made from it.
Science validates that maintaining consistent vapor pressure levels ensures that trichome heads are uncompromised, resulting in superior terpene retention, elevated quality, as well as a more consistent final product. If the vapor pressure deficit (VPD) in a drying or curing area is ever-changing due to dehumidifiers and HVAC systems cycling on and off, the stress will compromise the integrity of the trichome head membrane (cuticle)—as the VPD fluctuates, the cuticles expand and contract.
This constant change, combined with the rapid drop in water content, can cause the cuticle to rupture like a popping balloon. Terpenes begin to evaporate, and cannabinoids begin to oxidize and degrade, negatively affecting flavor, potency, and product value.
When a trichome head properly cures in a consistent, equalized environment, the cuticle membrane has time to thicken and stabilize. Science has proven it is best to utilize a stable and gentle drying process that is consistent to produce the highest quality finished product.
Today, companies produce HVAC systems capable of precise environmental control that also reduce airborne particles to minimize bacterial and fungal threats. Air sanitizers and sterilizers are also readily available today for use in both cultivation and post-processing environments to reduce the contamination risk (and the need to overdry cannabis to pass microbial testing).
Since 2017, there have been significant advancements in the environmental control sector of the industry. Companies are producing advanced grow room monitors and technologies that measure leaf surface temperatures, photosynthetically active radiation (PAR), daily light integral (DLI), humidity, CO2, temperature, and VPD.
Some of these monitoring technologies have applications in the drying and curing environments as well. Tight monitoring contributes to a replicable and predictable drying and curing process, which is critical to producing a consistent product that consumers (and patients) can rely on.
To that end, some companies have gone so far as to design environmentally controlled devices, pods, or custom-built rooms specifically designed for drying, curing, trimming, packaging, and storage. These systems aim to seal in terpenes by preventing large swings in temperature, humidity, and VPD. This results in an equalized environment that encourages the trichomes to cure while preserving their valuable contents, contributing to an overall high-quality final product.
In the trimming and packaging rooms, climate-controlled technologies can mitigate the loss of moisture in the cured product. Loss of moisture in trim and packaging rooms leads to weight loss and overdried flower.
Advanced HVAC systems have also been designed to recirculate and treat air from cultivation as well as drying and curing environments for reuse in those rooms (air should never be moved across rooms or facility areas). Traditionally, growers utilized dehumidifiers in both cultivation and drying environments to rid the air of moisture. But dehumidifiers can also add an unneeded heat load that can trigger cooling systems.
More recently, HVAC systems called “reheat” allow growers to remove moisture from the air without introducing heat into the environment. These systems recirculate air from the cultivation area (or drying and curing spaces) through a finned condenser that cools the air and condenses the moisture it contains into water (which is drained away for filtration and reuse). The cooled and dried air is then reheated within the unit to the desired temperature and reintroduced into the needed space, and the process begins again. This creates a very predictable environment with a consistent VPD.
Dedicated research into the conditions that yield the highest quality cannabis has led to the development of these innovative technologies. Yet these are just a sample of what has been released in the last eight years and what is being conceptualized and tested in facilities globally. I, for one, cannot wait to see what solutions are in store for this industry.
Kenneth Morrow is an author, consultant and owner of Trichome Technologies. Facebook: TrichomeTechnologies Instagram: Trichome Technologies Email: [email protected].
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