The production of biological agents for pest control — such as entomopathogenic fungi, bacteria, viruses, mites, and beneficial insects — demands rigorous environmental control that goes far beyond simple thermal comfort. In biofactories, relative humidity (RH) is the most critical variable, directly impacting biological viability, reproduction rate, shelf life, and the stability of the final product.
This technical article compares the two main dehumidification technologies available in the market: mechanical (refrigerant-based) dehumidifiers and desiccant (rotary) dehumidifiers. Understanding the differences between these technologies is fundamental for correctly specifying the HVAC system of a biofactory.
Why Humidity is Critical in Biofactories
Uncontrolled humidity can completely compromise a batch of biological production. The impacts vary according to the deviation:
| Condition | Consequence |
|---|---|
| High RH (>70-75%) | Proliferation of contaminant fungi |
| High RH | Spore agglomeration |
| High RH | Reduced product shelf life |
| Low RH (<40%) | Desiccation of living organisms |
| RH fluctuations | Biological stress and loss of efficiency |
The technical conclusion is direct: unstable humidity = biologically unstable product.
Typical Humidity Ranges by Application
Each stage of the biological production process demands specific humidity ranges:
| Application | Ideal Relative Humidity |
|---|---|
| Entomopathogenic fungi production | 50-65% |
| Beneficial insect rearing | 55-70% |
| Incubation rooms | 60-75% (fine control) |
| Processing and packaging | 45-55% |
| Storage | 40-55% |
The critical point is not just reaching the average value, but ensuring stability and repeatability throughout the entire process.
Product Drying: Why Use Desiccant Below 20% RH
One of the most critical steps in biopesticide production is the final product drying. Unlike the production and incubation phases (which typically operate between 50-70% RH), the drying stage requires extremely low humidity levels — often below 20% RH.
Why Dry Below 20% RH?
Proper drying of the biological product is essential for:
| Objective | Required RH Range | Technical Justification |
|---|---|---|
| Spore stabilization | 15-20% | Reduces metabolic activity, increasing shelf-life |
| Viability preservation | 10-18% | Prevents premature germination during storage |
| Contamination prevention | <20% | Inhibits growth of contaminant fungi and bacteria |
| Dosing ease | 12-18% | Dry product flows better in application equipment |
| Transport stability | <15% | Prevents reactivation during logistics |
Why Can Only Desiccants Achieve These Levels?
Mechanical (refrigerant-based) dehumidifiers have a fundamental physical limitation: the minimum achievable dew point is determined by the evaporator coil temperature. In practice, this means:
- Mechanical dehumidifier: Minimum achievable RH of 45-50%
- Desiccant dehumidifier: Minimum achievable RH of 10-15% (dew point down to -20°C)
To achieve RH below 20%, a desiccant unit is the only technically viable option. The hygroscopic material in the rotor (silica gel) can adsorb moisture even when the air is already relatively dry, which is impossible for condensation systems.
Drying Applications in Biofactories
| Process Stage | Typical RH | Recommended Technology |
|---|---|---|
| Spore drying in trays | 15-20% | Desiccant |
| Granular formulation drying | 12-18% | Desiccant |
| Final packaging room | 18-25% | Desiccant or hybrid |
| Stabilization chamber | 10-15% | Desiccant |
| Long-term storage | 15-25% | Desiccant |
Typical Drying Configuration
A drying system in biofactories typically includes:
- Mechanical pre-treatment: Removes most of the moisture (from 70% to 45-50% RH)
- Desiccant dehumidifier: Final polishing (from 45% to 15-20% RH)
- Temperature control: Maintains ideal conditions for the product
- Continuous monitoring: High-precision sensors (±1% RH)
This hybrid configuration optimizes energy consumption while ensuring the necessary humidity levels for final product quality.
"In biopesticide drying, every percentage point of humidity can mean months more or less of product shelf life."
Mechanical (Refrigerant-Based) Dehumidifier
A mechanical dehumidifier operates on the condensation principle: humid air passes over a cold coil (evaporator), where the temperature drops below the dew point, causing moisture to condense and drain. The dry air is then reheated before returning to the environment.
Advantages:
- Generally lower initial cost
- Good energy efficiency in high ambient temperature conditions
- Widely known and available technology
- Relatively simple maintenance
Limitations:
- Efficiency drastically reduces at low temperatures (<15°C)
- Difficulty in achieving very low RH (<45%)
- Can cause unwanted cooling of the environment
- Less precise for fine humidity control
Ideal Applications: Environments with ambient temperatures above 20°C and requiring RH between 50-70%.
Desiccant (Rotary) Dehumidifier
A desiccant dehumidifier uses a rotor impregnated with hygroscopic material (silica gel) that adsorbs moisture from the air. The rotor continuously rotates, passing through a regeneration zone where hot air removes the adsorbed moisture, which is then exhausted to the outside.
Advantages:
- High precision in humidity control
- Operates independently of ambient temperature
- Ideal for achieving very low RH (<45%)
- Dew point down to -20°C
- Stable even with frequently opened doors
- Does not cause cooling of the environment
- Excellent for environments with dominant latent loads
Limitations:
- Higher initial cost
- Higher energy consumption (requires heating for regeneration)
- Requires exhaust to the outside
- Rotor maintenance requires specialized attention
Ideal Applications: Environments requiring RH <55%, operation at low temperatures, or fine and stable humidity control.
Hybrid Systems: The Best Solution
For biofactories with variable demands, combining both technologies offers the best cost-benefit:
- Mechanical dehumidifier as the first stage, removing most of the latent load
- Desiccant dehumidifier for final polishing, ensuring precision and stability
This hybrid architecture provides:
- Greater energy efficiency
- Precise control under variable loads
- Operational redundancy
- Reduced wear on each piece of equipment
Recommended System Architecture
The typical technical flow for a biofactory includes:
- Outside air filtration
- Pre-cooling (if necessary)
- Dedicated dehumidification (mechanical and/or desiccant)
- Controlled reheating
- Homogeneous distribution
- Continuous monitoring (RH + Temperature)
Sensors should be strategically placed: at the air intake, at the return, and in the critical process zone.
Control and Automation
The control system should include:
- High-precision RH sensors (±1-2%)
- Proportional-integral-derivative (PID) control logic
- Historical logging for traceability
- Process deviation alarms
In mature biofactories, environmental control is an integral part of quality control.
Conclusion
The choice between a desiccant and a mechanical dehumidifier is not a question of which is "better," but rather which is more suitable for each specific application. For biopesticide biofactories, where humidity stability is critical for product quality, desiccant dehumidifiers generally offer significant advantages, especially when combined with mechanical systems in a hybrid configuration.
"In biological control environments, humidity is not comfort — it is process."
Helioterm offers complete industrial dehumidification solutions, including desiccant and mechanical dehumidifiers, with capacities ranging from 150 to 12,500 m³/h. Contact us for a customized sizing.