To estimate the cost of expenses for environmental control in growing rooms the following must be considered:
- Inlet and exhaust fans
- Air ducts
- Air conditioning
- Water mixing valves
- Control and measuring instruments
- Humidity system
Additionally it is necessary to take into account the costs for preparing a hot water (boiler), the coolant (chiller), steam (steam generator), etc.
These costs depend on the volume of substrate loaded to the growing room, rate of automation and specifications of the production process.
We will consider some recommendable air conditioning systems for oyster mushroom and button growing rooms, and variants how to simplify and reduce them in price.
Air Conditioning For Growing Rooms
Features of air conditioning for mushroom cultivation are:
- air recirculation loop
- installing cooller before heater
- temperature of the cooler surface in the cooling mode at a constant moisture content is equal to the dew point
- temperature of the cooler surface in the cooling mode with simultaneous dehumidification must be below the dew point temperature
- temperature of the cooler surface at the adiabatic cooling is equal to the wet thermometer temperature
- air heating, cooling, humidification should be produced in the air duct
The air recirculation loop saves the energy resources of a mushroom farm. Otherwise, a mushroom grower spends money on heating (cooling), humidification (dehumidification) of inlet air and... eventually throws out all prepared air through the exhaust. Without using circulation during a winter period when the air outside is very cold with a low moisture content, a flow of cold air can hit the fruiting zone which affects the yield.
If the cooler is installed before the heater, it allows to dry air in the growing room by lowering its temperature below the dew point with the help of cooler and then to warm it to the required temperature with the help of heater.
The recommended air handling unit is shown on the picture below.
The three-phase snail fan is recommended for air supply. It increases the service life of fans. The fan capacity is calculated based on the substrate (compost) volume loaded to the growing room.
|1 - outside air damper or slide valve
2 - circulation air damper or slide valve
3 - cooler
|4 - heater
5 - inlet fan
Environmental Control System in Button Growing Rooms
|1 - pressure damper
2 - exhaust fan
3 - humidifier
4 - humidifier valve
5 - inlet fan
|6 - frequency inverter
7 - hot water valve
8 - cold water valve
9 - circulation air damper
10 - outside air damper
The purpose of units included in the environmental control system can vary at different phases of growth.
When the growing room is loaded, the compost temperature is very uneven. The inlet fan is used to level the temperature of compost. It should rotate the stronger, the more the temperature difference. At the same time, the outside air damper should be completely closed and the circulation damper fully open. Heater and cooler (usually, on this phase the heater is ON) maintain the set compost temperature. Humidity is not adjustable.
When the compost temperature has become equal, the inlet fan operates at minimum speed, the heater if necessary works on heating. The cooling can be accomplished by adding an outside air. But on this cultivation phase the amount of outside air should be limited. The humidification is started if needed.
After adding a casing layer, the amount of outside air is still limited (accumulating CO2), the temperatures of compost and air, as well as air humidity are kept constant. CO2 is not even measured in order to avoid a sensor failure.
The main purpose of the Spawn Run III phase is to accumulate carbon dioxide. Therefore, it is better to close the outside air damper and cool by the cooler. The compost and air temperatures, as well as air humidity should remain stable.
The air in the room is cooled by both the outside air and the cooler, lowering the compost temperature at a given speed. The number and size of future mushrooms depend on the performed cooling. Simultaneously CO2 level is rapidly decreasing. At the end of the Cool Down Pinning phase CO2 measuring is started. On this phase, the inlet fan RPM depends on the compost temperature (the stronger the cooling, the more it rotates).
On the Pinheading and Harvesting phases the outside air damper is used to control the level of CO2, the heater and cooler are used to maintain the air temperature, and the humidifier maintains humidity. The inlet fan also controls CO2 concentration. Depending on the circumstances the technologist can change the priority and make the outside air and inlet fan operate for cooling or drying. If there is a need, the heater is also used for drying.
Climate Control System In Oyster Mushroom Cultivation Rooms
|1 - frequency inverter of exhaust fan
2 - exhaust fan
3 - humidifier
4 - humidifier valve
5 - inlet fan
|6 - hot water valve
7 - cold water valve
8 - circulation air damper
9 - outside air damper
In oyster mushroom growing rooms it is recommended to insert two temperature probes in each control block of substrate. One of them should be in the middle of the block, another one is under the film. It helps the mushroom grower to control the quality of the blocks during the incubation and fruiting process.
Another feature of oyster mushroom growing rooms is that the blocks themselves are never watered, so the main task of the system is to keep a high level of humidity in the room. It’s done by using a frequency inverter which is connected to the exhaust fan. With the help of the frequency inverter a zero or a slight negative pressure is achieved in the room.
On the Warming phase only the air temperature is regulated, the outside air damper is fully closed.
On the Incubation phase both temperature and humidity are regulated. The compost temperature is controlled. CO2 is not measured. The heater, cooler and humidifier are used for creating climate. The outside air damper is closed or used for cooling and drying. The readiness of blocks for cooling is determined by the ratio of the temperature in the center of the block, under a film and in the air of the room.
On the Cooling phase outside air is actively used for cooling.
On the Fruit formation and Fructification phases the outside aire damper is used to maintain the required CO2 concentration, heater and cooler are used for achieving the required air temperature, and the humidifier – for maintaining the required air humidity.
Ways To Reduce The Cost Of Environmental Control System
Simplified automation schemes are used for small growing rooms.
The simplification is done in order to save equipment costs.
The environmental control system remains the same, only the proportion of automation is reduced and some of the processes are simplified.
Here are the ways how to simplify the system:
- Frequency inverter is not installed. On the Temperature Compost Leveling phase the inlet fan is always ON, and it’s turned off for the entire period of incubation. Then it’s turned on the Cool Down Pinning phase and is kept ON until the end of mushroom picking.
- Slide valves are used instead of inlet air and recirculation valves. They are opened and closed by hand.
- Carbon dioxide transmitter is not purchased. Starting with the Cool Down Pinning phase the degree of opening outside air damper is selected empirically.
- Cooler is not installed. The production is closed for the summer period.
- Automatic humidification is not made. The floors, walls and compost are watered manually (only for white button).
The list of used devices and sensors depends on the size of the growing room and whether the substrate is incubated in a separate room or not.
Therefore, the cost of creating environmental control system in growing rooms varies widely.