How To Dry Hemp
It is very important that harvested plant material is dried before being moved to storage. Hemp seeds and flowers heat and expand very rapidly after being removed from the vine causing leaves and buds to sweat. This causes pockets of condensation to build up inside the bin, leading to mold growth.
Because hemp flowers tend to clump as they heat, fatty acids can quickly build up inside the oil, causing it to lose potency or even turn rancid through fermentation and bacterial exposure if left unattended for too long. Naturally, heated or moldy buds will be rejected by the processor as they will fail to meet strict purity standards required for food grade labeling.
When considering how to dry your hemp, there are many different avenues that can be taken. First, you'll need to determine if you'll be drying indoors or drying outdoors. Indoor & outdoor methods can be combined, especially in single-variety fields. Each method will require its own set of tools, although strict line drying requires minimal tool usage, whereas indoor drying is done specifically so the operation can be carried out in its own dedicated space designed (or at least suitable) to facilitate the use of large-scale industrial agricultural equipment.
You could also engage in a hemp drying service in which you pay someone else a fee to dry your hemp for you (though they'll have to be in close proximity).
If you prefer to purchase hemp drying equipment (and possibly do the drying for others as an additional service you offer), there are a number of styles and variations on the market. Below is a break down of the various types of equipment that is used during the drying phase. Note that more and more technologies are coming online as the hemp industry evolves.
Traditional Grain Drying Equipment
A drying solution that is nearly ubiquitous in the wheat industry, these large-scale drying machines can rapidly dry large quantities of freshly cut hemp and can easily keep pace with a rigorous combining schedule. Accelerated heating takes place towards the end of the drying cycle as heat builds up inside the bin, which can cause overheating when applied to hemp. Hence, while they present a powerful option for speedy drying, some care and practice are required to determine appropriate heat staging to minimize the risk of burning the bin contents.
Continuous Flow Dryers
Continuous flow dryers enlist the use of a double conveyor belt system, where one conveyor continuously feeds the drying mechanism with incoming plant matter and the other turns out the finished dried product. These devices are a favorite among farmers across many Industries due to their high throughput capacity. In the case of hemp flowers they have been shown to churn out an impressive 1,000 pounds of damp plant matter per hour.
Conveyor Belt Dryers
Similar to continuous flow dryers, conveyor belt dryers also allow for constant throughput of combined plant matter, except that these systems employ heating drums rather than pressurized airflow chambers to affect desiccation. Drums are available in multiple sizes, providing an adaptable solution that can be scaled with operations at minimal cost. They are particularly well suited to farmers who must dry large quantities of very moist hemp flowers for which conventional continuous flow dryers may not prove as effective.
Grain Drying Fans
A simple, cost-effective solution that can be used as a standalone in conjunction with that dryers or other drying systems. It should be noted that drying through direct application of air current is necessarily less efficient than drying inside a closed chamber, as a strict fan-based setup does not allow for channeling of air currents into concentrated streams that would speed up the drying process. They may however prove ideal for new farmers who do not yet possess the budget to invest in industrial scale solutions. Farmers who tough-harvest their hemp crop — that is, harvest by hand — may also find an appealing option in a well-placed array of drying fans that can apply constant airflow to freestanding bins while subsequent loads are being harvested.
As with drying fans, conventional air conditioning units can be employed as a standalone solution so long as units are sufficiently powerful to dry the targeted quantity of hemp flowers. However, their optimal use case scenario is to play a supporting role in long-term aeration during storage, and for the cooling of freshly dried hemp flowers, to bring them to room temperature before bailing for storage.
Traditional Hang Dryers
Specifically intended for use in cool, dark storage areas where whole-harvested hemp plants are to be dried in bulk. These drying systems offer both temperature and humidity control settings. In the case of hemp, a temperature setting of around 65 degrees Fahrenheit (18 degrees Celsius) and about 62% humidity has been found to be effective for some farmers.
Novel Hemp-Specific Drying Equipment
Mesh Hemp Belt Drying Machines
Designed for use by multi-cultivar hemp farmers who require more nuanced control over the drying process than is typically afforded by conventional grain drying equipment. These systems employ multiple physically isolated drying chambers, each with its own internal hot air circulation system and exhaust fan for moisture filtration. Temperature and drying time can be adjusted individually for each chamber, allowing for concurrent drying of separate flowers batches with varying moisture contents. This level of control eliminates the need to recalibrate settings for each incoming hemp batch.
Portable Hemp Dryers
These newcomers to the scene purport to possess the capacity for drying up to 75, 000 lbs of plant material per hour. Independent testing and research have yet to be done to verify these claims and anecdotal reports are sparse at present.
Nonetheless, it may be worth keeping an eye on these and similar devices slated to hit the market soon. Intrepid farmers may wish to test out such equipment themselves, especially if the manufacturer offers a rental or trial period.
Custom Hemp Drying Systems
These straightforward machines are designed to the individual farmer’s specifications along the lines of drum size and burner temperature, with components mounted in concurrent configuration. These systems are constructed to dry as many as eight tons of hemp per hour at an output moisture of between 10 and 12%. It is worth noting that while these figures are certainly impressive, many hemp processors require a flowers moisture content of between 8-9% for long-term storage. Nonetheless, it is advisable to keep an eye on these options as competition drives manufacturers to strive to achieve even lower output moisture levels.