Hemp Aeration Systems & Standards
Aeration is the process of maintaining target moisture levels over time. Though aeration systems are often used in the drying process as well as in storage, we have chosen to discuss them with the Storage phase because it requires maintenance of hemp that is already dried (even if the drying was done by another aeration system in the drying facility).
Aeration Best Practices For Drying & Storing Hemp Flowers
Appropriate bin levels are determined by overall plant matter dryness. In most storage situations, bins can be filled halfway because buds will have been dried to moisture levels below 50%. When aeration systems are used for drying, the percentage shifts as follows
- +20% Moisture Content = Fill to 30% capacity
- 11-20% Moisture Content = Fill to 40%
- 10% or Lower Moisture Content = Fill to 50%
Even buds in round balers need to rotated every few days to ensure all flowers are receiving relatively equal air exposure. This further prevents buildup of condensation, especially in square balers.
Ensure the tops of bins are well-ventilated whether or not aeration systems are employed in the initial drying. If used during drying, condensation will build up on the bottom of the bin roof. This can easily seep into the bins and quickly pose a compromising situation to interior contents.
Length of Aeration Period
A period of 1-3 weeks has been suggested for grain drying, with fans set at 5 hp. A comparable timeframe should prove acceptable for hemp flowers when the goal is to bring bin contents from 10% to 8% moisture levels.
Limitations of Aeration Systems
Aeration tends to work best during the autumn when conditions are cool and dry, though this may vary by geographic region.
Aeration Systems & Methods
Generally speaking, there are two systems of consideration, Floor Aeration and Dual Aeration. We will cover Dual Aeration in greater detail.
1. Floor Aeration Systems (for Single-Factor Control)
Also called “Rocket Systems,” this method generates cool/room temperature air currents to maintain dryness without scorching or over-desiccation of plant matter as can sometimes happen with two-factor systems as described below.
2. Dual Aeration & Heating Systems (for Two-Factor Control)
These systems also feature heaters and are very useful in situations where hemp buds may require further drying while in storage, as for instance when they must be stored in square balers per processor requirement.
While ideal heat levels for flower drying in dual-purpose systems have not yet been determined, stats pertaining to seed drying are likely applicable.
When To Use A Dual Heating & Aeration System
Dual Purpose systems often come into play when very large quantities of plant materials must be dried before separation, or when previously dried materials are consistently coming into storage 1-2 percentage points above safe long-term storage levels (8-10%). In these cases, a system capable of providing additional heat as well as air circulation could be an optimal solution.
Choose a hopper-bottom bin system with fans powerful enough to project air even up and throughout the entire bin. The following specs should prove sufficient.
- Fan power = 5-10 hp
- Propane Burner = 100, 000 BTU
Be sparing with the burners, and do not exceed 95 degrees Fahrenheit (35 degrees Celsius) if using the system for secondary drying.
NOTE: See below for appropriate temperatures when dual systems are used for primary drying.
Heat Staging & Monitoring
Farmers who dry their plants whole using Dual Heating/Aeration Systems will need to keep heat staging in mind. Not every part of the plant dries at the same rate. Many of the unusable plant parts will dry first, making it necessary to back down the levels towards the end of the drying period. Use the temperatures employed in seed drying as a safe starting point, but don’t be afraid to experiment, and never use any accepted standards as a stand-in for consistent monitoring throughout the period.
- 150 to 160 degrees F for first half of drying period
- 120 to 130 degrees F for duration of drying period