Editor’s note: This story is a follow-up to Kenneth Morrow’s Tomorrow in Cannabis column “The Problem with Drying Cannabis,” published in Cannabis Business Times’ May 2020 issue.
From seed to sale, plenty of considerations exist to ensure cannabis is properly hydrated.
If the importance of not overdrying is lost on anyone, comparing cannabis as raw flower to maintaining moisture in cigars could be an analogy that emphasizes its importance. I could take two cigars, place one in a humidor and the other on the dashboard of a car for the summer, then at summer’s end, place the cigar from the dashboard back in the humidor with the other cigar.
After a week rehydrating in the humidor, both cigars would again have the same moisture content, but the rehydrated cigar would have lost its true flavor, its delicate aromas and complexities that contribute to the overall flavor experience. The dashboard cigar would be inferior due to the evaporation of essential oils that occurred when the cigar was exposed to high heat, low humidity and lots of UV light.
While this is an extreme example, the result would be comparable to overdried cannabis, in that both have lost their aromatic terpenes to evaporation from overdrying.
Commercial Drying Methods: Close, But No Cigar
Many large-scale producers have experienced bottlenecks in production at the drying and curing stage. Because they need to run as efficiently as possible to maintain their margins, many investigate alternative plant-drying technologies used in other industries, such as infrared (IR) dryers, dehydrators, microwave dryers (tunnel dryers), kiln dryers used for hops, and other similar industrial plant biomass dryers. These drying methods can be problematic because they tend to overdry cannabis, resulting in terpene loss from excessive heat.
Some large-scale producers may prefer or only have the ability to hang dry en masse in large warehouses converted to drying areas. These setups typically do not allow employees to closely monitor each plant or bud due to the sheer volume of product on floor-to-ceiling hangers and racks. In addition, these warehouses usually contain product that the operation harvested over a period of time (whether over a few days or a few weeks), instead of keeping products sequestered by their harvest dates. This can lead to fluctuations in moisture levels across different batches (some will be too dry, and some not dry enough), which can then turn into mold and mildew contamination when there is inadequate ventilation to exhaust excessive moisture.
When done properly, all of the above methods are typically acceptable for drying hemp destined for textile use or cannabinoid-only extraction. However, they are not ideal for drying hemp or cannabis destined for consumption in raw flower form or for THC- and terpene-rich material intended for extraction for concentrates.
Cultivators drying hemp or cannabis must closely monitor many environmental conditions, especially these top three factors:
- Dry room temperature
- Dry room humidity level
- Dry room air flow
The key is to properly manage all three at once, which requires specialized equipment that suits the application, such as professional HVAC systems. The wrong approach is to attempt to reinvent the wheel, as one licensed grower in Colorado attempted to do with a new device. When humidity levels dropped significantly to unacceptable levels, the grower compensated by employing a piece of equipment that released “steam” into the drying chambers. Adding steam ultimately was counterproductive because drying slowed, as the company had no air exhaust or intake capability, just the ability to heat and cool and humidify and dehumidify. The result was cannabis that reeked of ammonia, a byproduct of plant degradation.
An Arizona grower designed a similar “closed-loop” system for his cultivation facility, with no fresh air intake nor air exhaust capabilities for both the cultivation areas and the drying/curing areas. They relied solely on dehumidifiers and air conditioning, which resulted in elevated humidity levels and a proliferation of mildew and the production of subpar cannabis. They should have employed a proper HVAC system that, in essence, provides total control of a given environment, whether cultivation or drying.
Proper HVAC systems employ or utilize a combination of fresh air intake and exhaust, with heating and cooling, humidification and dehumidification, and oxygen-rich filtered and sterilized intake air, combined with proper air flow. Anything less can rapidly result in overdrying, fungal contamination, or greatly reduced terpene levels. An HVAC system should be able to handle a multitude of weather climates and do so as efficiently as possible.
Besides creating a proper drying environment, growers must consider other terpene- and moisture-loss situations and environments. Here’s an example: Sorting buds by size, such as small, medium and large, allows for better control of each group’s drying rate, because all three dry at different rates. The small will dry before the large. If an employee mixes them together during drying, it encourages the inevitability of waiting for the large buds to dry, and the small and medium buds usually become overdried. By sorting buds by size and drying them in separate rooms, consistency can be achieved without sacrificing moisture and terpenes.
Prevent Moisture Loss in Packages, Pre-Rolls
There is also a risk of moisture and terpene loss during packaging.
Many years ago, I consulted for a high sales volume dispensary. To prevent any interruptions in the supply chain, 650 pounds of flower had to be in inventory at all times. The facility stored it in a refrigerated (not frozen) storage area. Inventory sold very rapidly, so the flower did not sit in storage for more than two weeks. From storage, it went to the packaging area in 1- to 5-pound batches, where it was weighed and placed in various-sized containers for sale.
I’ve seen during this process—depending on climate, environment and how fast a worker could break down that pound into smaller packages—that a pound could lose between 1 and 5 grams from moisture evaporating. Moisture evaporation also caused terpene loss.
The solution for this dispensary was to create a climate-controlled weighing and packaging room for 15 people to weigh and package product. The climate control not only aided in preserving the delicate essential oils that are responsible for the aroma and flavor of cannabis, it also mitigated product weight loss by preventing moisture evaporation in the cannabis. This resulted in a much more desirable product with respect to preferred moisture content, aroma and flavor of the packaged buds, in addition to helping with compliance tracking (because inventory weights aligned).
I believe an excessively dry or warm environment also can dry out cannabis when it is in the process of being ground, rolled and packed into pre-rolls. A climate-controlled environment with a set temperature and humidity discourages moisture evaporation, so it would seem to help prevent overdrying the product and provide a more pleasant pre-roll consumer experience.
A customer does not desire a dried-out pre-roll, therefore an employee rolling and packing pre-rolls should not start with dried-out cannabis material that crumbles under the slightest touch.
Pre-rolls should be placed in airtight containers, not cardboard cigarette box-type of packaging; the latter can absorb moisture from the pre-roll contents, resulting in over-dried cannabis, and again, a less-than-desirable consumer experience.
Airtight containers should then be placed in refrigerated storage, while displacing all oxygen in the containers with nitrogen gas to minimize oxidation. The containers also should be opaque to prevent light transmission to the products and minimize THC degradation.
Even if properly stored, cannabis is ultimately a perishable item that is in a constant state of degradation. It has a shelf life of six months to one year maximum, if stored properly. I personally prefer cannabis fresh after curing, i.e., two to three months after harvest. (Are you putting both harvest and packaging dates on your product labels?)
After curing, the goal should be to minimize the moisture evaporation at every stage, from weighing to pre-rolling to packaging. Rehydrating overdried cannabis addresses the overdried aspect, but once overdried, many terpenes are lost forever, resulting in less aromatic and flavorful cannabis.