Drying Services

DRYING HEMP FOR STORAGE

Hemp must be dried and stored immediately after it is harvested. Because of this, drying is often counted among post-harvest operations. Yet despite their proximity in time, these operations are perhaps better thought of as two distinct phases in the overall hemp cultivation and production process. There are a number of reasons for this.

First, a different set of equipment is employed at this stage than during the harvesting stage.

Second, drying can be seen as part of a larger process of product preparation and maintenance pending its approval and delivery for processing.

Thirdly, many of the techniques and methods employed at this stage of the production process are sufficiently nuanced and extensive enough to deserve treatment as their own category.

Similarly, drying and storage should be treated as discrete steps within the overall post-harvest operational schematic for purposes of establishing production protocols and managing workflow.

Following this logic, we present the following drying & storage guide in two parts. In Part 1, we will consider

  1. DRYING

Hemp is always harvested at a higher moisture content than is safe to put into storage in order to prevent shattering loss during trimming or combining. For this reason, it should always be dried as soon after harvest as is practicable. Sometimes, when moisture content is particularly high, it should even be dried immediately after harvesting.

  1. DRYING METHODS

1) Outdoor drying (Drying on the vine)

Natural Approach

Deceptively less labor intensive but leaves a lot to chance (even if uncertainties can be minimized with sufficient knowledge, it’s never a sure thing and drying may be       inconsistent, especially on dual variety farms)

2) Drying in a Facility

Typically done inside a barn used exclusively for drying crops

If possible, dry hemp in its own dedicated facility to avoid contamination through   contact with other crops

If total isolation is not possible, clean thoroughly to remove residual matter from previous crop, especially wheat if crop is to qualify as food grade hemp          (Food grade hemp must be certified gluten free)

NOTE: Doesn’t apply to farmers growing exclusively for industrial fiber or              biomass)

Best Practices For Selecting & Maintaining Hemp Drying Facilities

Combining Methods

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.

Outsourcing Drying Operations

This is a third option for new and small-scale farmers who do not yet have on-site facilities required for large scale hemp production, or for those desiring to produce smaller yields and for hobbyists.

One possible downside for next few years is price. Hemp is booming. Everyone    wants in, and drying facilities will continue to remain in high demand until the market      stabilizes.

These services often tend to be highly regional, and there is no guarantee that they may be available in any given state or locale.

  1. HEMP DRYING EQUIPMENT

Commonly Used Hemp Drying Equipment                                                                                                                                                                                                                                                                

Grain Drying Fans                                                                                                                                                                                                                             

AC Units                                                                                                                                                                                                                                                                   

Continuous Flow Dryers                                                                                                                                                                                                                                                                   

Batch Dryers                                    

Conveyor Belt Dryers                                  

Less Common Hemp Drying Equipment                                                                                             

Mesh Hemp Belt Drying Machine     

Traditional Hang Dryers                                                                              

Novel Hemp-Specific Drying Equipment

Hemp Drying Systems                                                                                                                                                                                                                              

Portable Hemp Dryers           

  1. STEPS TO COMPLETE (OUTDOOR DRYING)

This method is often used prior to removal of hemp flowers to reduce the amount of time required to batch dry after trimming or combining has been completed. Allowing the hemp plant to dry naturally on its own can be useful when desiring to jumpstart the curing process.

STEP 1: Dry Until Stems Split When Bent

Leave hemp plants hanging on the line for 3-10 days until stems begin to split when bent. This will serve as a cue that flowers are dry enough to be trimmed.

NOTE: Do not allow stems to become so dry that they snap under pressure as this can lead to the loss or damage of trichomes as they will be more susceptible to flaking when casually brushed or carelessly handled.

Length of Drying Period

The exact duration will depend on several factors including heat and sunlight exposure nearing the time of harvest, as well as the size of the buds to be dried.

  1. STEPS TO COMPLETE (INDOOR DRYING)

STEP 1: Determine Moisture Content

Hemp is always harvested at higher moisture than what is considered safe for storage. This is to mitigate the risk of crop loss due to shattering that occurs when plants are harvested too dry. Farmers should therefore test the overall moisture content of the crop prior to harvest to determine whether immediate drying is necessary before moving to storage.

  1. Immediate Drying (High Moisture Content)

Use grain dryer before moving to storage when seed moisture is over 13 or 14%

  1. Standard Interval Between Harvest and Drying (Average Moisture Content)

Urgency is somewhat diminished when moisture content is closer to the standard 10-12% at harvest time. However, hemp should always be dried as soon as possible and should not be allowed to retain harvest moisture levels for more than a          few hours after trimming or combining.

STEP 2. Dry Before Storing

It is very important that harvested plant material is dried before being moved to storage. Hemp seeds 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 seeds 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 seeds will be rejected by the processor as they will fail to meet strict purity standards required for food grade labeling.

STEP 3. Use A Dedicated Drying Facility

Hemp plants should not be stored in the same place they are dried, as the drying process will cause seeds and buds to sweat out any dirt or other impurities that may have built up during the growing stage. This is true even for plants that have been grown inside a greenhouse or other indoor facility. Hemp must be cleaned before it is stored, and it is best to do this away from the storage site so that it may remain free of foreign debris and contaminating agents.

Maintaining a dedicated facility for drying also facilitates operational workflow. Because plants will not be stored there, space can be made available for incoming batches as dry, clean batches are moved out to be placed into storage.

STEP 4: Arrange Plants Correctly In The Drying Facility

Most hemp plants can be hung upside down as whole plants or divided into large branches to undergo drying before separation of large stems before plants undergo further processing.

However, plants intended for for medicinal use are best separated immediately prior to hanging, as this arrangement facilitates greater air flow and consequently a more even drying experience. This becomes particularly necessary when dealing with large plants or stems carrying thick, dense buds.

STEP 5: The Drying Process

Several options are available for large scale machine drying. Some of these machines use excess heat, which could potentially degrade the cannabinoids and even vaporize the terpenes, so much care and research should be done prior to financially committing oneself to a particular setup.

Continuous Flow v. Batch Dryers

Either continuous flow and batch dryers can be used for bulk drying of hemp. However, standard batch dryers tend to pose a higher risk of overheating seeds, causing hot spots to form, particularly in areas where seeds where less densely packed together and subjected to greater exposure to hot air currents.

While this limitation does not impact the efficacy of the drying process, it can nevertheless slow down workflow since each newly dried batch must be given time to cool down and subsequently be checked for any overheated plant material that must be removed before the batch is transferred into storage.

Heat Levels & Monitoring

Grain dryer temperatures must be continuously monitored in order to prevent overheating of hemp seeds. Overheated seeds can be recognized by their yellowish color indicating a loss in oil quality due to scorching.

Moderate heat levels are advised, with a recommended plenum temperature of about 45 degrees Celsius in order to maintain batch temperatures at around 35 degrees Celsius. These levels will facilitate slow, consistent drying of hemp seeds with minimal shattering loss.

STEP 6: Allow Dried Hemp To Cool

Cool After Drying

After drying, hemp seeds need to be cooled to ambient room temperature.

before baling can be commenced. This is particularly true when drying is done in facilities that do not have or cannot accommodate continuous drying systems.

Ventilation at room temperature with a rate of 0.6 to 0.8 m3/min/ton will typically suffice.

When bin depth is in excess of 1.5m, air pressure must also be calibrated to improve penetration. A setting of around 2.5-5cm W.G. is well tolerated and generally effective. Fine tuning can be applied as needed once familiarity with the equipment is established.

Target Moisture Content

The industry has agreed upon a 10% moisture level for hemp to qualify as dry. However, because hemp destined for the marketplace can sit in storage for as much as 1-2 years before being shipped out for processing, many processors require storage moisture levels closer to 8-9%. It is best to consult the processor well in advance of harvest to ascertain what they consider safe for long-term storage.

STEP 7: Clean Hemp Seeds & Harvest Equipment Before Baling

Seed Cleaning

Seed Cleaning Equipment

Equipment Cleaning