Microwaves: The Best Way to Dry Hemp and Cannabis


Microwaves: The Best Way to Dry Hemp and Cannabis


Microwave Dryers

Drying freshly harvested hemp has been a vexing problem for large scale CBD processors. Traditional drying systems are not well suited for hemp because of high drying temperatures or slow process rates.  Microwave dryers have been used for many years to dry fresh herbs and botanicals on a large scale. Cellencor has tailored this technology to the specific requirements of high volume CBD processing.


Benefits of Microwave Drying Systems

  • Speed: Like your home microwave oven, microwave drying is much faster than any other method.
  • Low-Temperature Drying: Because microwave energy selectively targets water molecules, the temperature of the hemp during drying remains at about 120⁰ F. This protects the natural qualities of the terpenes and other essential molecules. CDB levels are not reduced.
  • Uniformity: The mixing action of the dryer assures highly uniform moisture content of the dried hemp.
  • Consistency: Advanced sensors and sophisticated computer control assure uniformity from batch to batch, even with varying composition and moisture content of the raw hemp input.
  • Scalability: Systems are configurable with a wide range of process capacities.
  • Ease of Operation: Operation is fully automatic with simple operator controls.
  • Efficiency: Microwave dryers typically are much more energy-efficient than convection and steam dryers.
  • All Electric: Powered by 480 VAC electric power, no natural gas is needed. It can be powered by diesel generator sets for remote sites.
  • Green: Can be significantly more environmentally friendly than other drying methods because the combustion is not needed. Your line power can be as high as 50-75% renewable in some locations.


Drying Profile

Because microwave energy selectively targets water molecules, the temperature of the biomass during drying remains at about 120⁰ F throughout the drying cycle.   This is well below the vaporization temperature of the essential oils and terpenes, so virtually no loss will occur. The mixing action of the dryer provides extremely uniform heating without hot spots, so their is no burning or overheating.  The cannabis/hemp retains its natural green color.

The graph below shows the drying cycle of a 200 cubic foot mixer/dryer equipped with 400 kilowatts of microwave power.  



Process Rates

For a given amount of biomass, the drying time will depend on the amount of microwave power available and the moisture content of the biomass.  A 2 hour cycle time is generally is a good balance between drying speed, moderate drying temperature, and equipment cost.  The tables below illustrate performance of various size mixer/dryers configured with sufficient microwave power for 2 and 3 hour drying cycle times.  These examples assume flowers and leaves chopped to 10 mm.



Significant conversion of THC-A or THC or CBD-A to CBD occurs during the microwave drying process.  The reason this occurs is not well understood, but it is clearly established by laboratory tests.   An additional heating step added to the end of the drying cycle can produce 95%+ decarboxylation.  This is a software controlled option.


A Plant Tour

This Cellencor-designed large scale drying plant is located in a remote location in Arizona where thousands of acres of hemp are cultivated for CBD oil production. The plant is equipped with a 400 cubic foot mixer/dryer with a processing capacity of about 24 tons per day of fresh hemp. The plant is pre-configured for installation of two additional dryers in the future. After drying, the hemp is pelletized and packed in bulk bags, which are then transported to an extraction facility.




The mixer dryer is installed on a steel mezzanine for easy access and to allow bottom discharge of dried product to a conveyor system.









This is a top view of the mixer/dryer, showing the loading port, exhaust duct, and waveguide which delivers microwave power from the generators.








Hemp in the dryer/mixer after drying, just before unloading. 









Freshly cut, chopped and screened hemp is dumped from an end loader into this intake hopper, which feeds a conveyor that loads the dry/mixer from the top.






This system is powered by eight Crescend Technologies 50 kilowatt solid state microwave generators.   These units have extremely high reliability and minimal maintenance, which is especially important at this remote site.

07/15/2021 9:51 AM |Add a comment
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