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​Han van der Kooij​​​
Product manager Fertilizers | November 7, 2020 | 3 min. reading time

• CO2 via cogeneration
• Adminisistering CO2 via supply tank
• Measuring CO2

The most common way to increase the CO2 concentration in the greenhouse is by making use of the exhaust gases from the cogeneration. These exhaust gases contain a significant concentration of CO2. However, they also contain the harmful gases NOx and Ethylene. For a proper purification of the exhaust gases, in the cogeneration a flue gas cleaner is used, in which a reaction takes place between harmful gases and urea. As a result, the harmful gases will combust.
  
Please note: impurities in the urea may cause the flue gas cleaner to wear as a result of which harmful gases could still reach the plant. Therefore, you must regularly check the flue gas cleaner for wear and perform timely maintenance.

In addition, CO2 can be delivered as a ready-to-use product. If you want to make use of this, you should have a supply tank at your disposal. A tank truck will be used to replenish this supply tank with pure CO2, coming from ammonia manufacturing facilities.

For a good dosing of CO2, it is important to measure the CO2-value, both inside and outside the greenhouse, by use of a CO2 meter. This way, you can make adjustments where required. Make sure that the CO2-meteris calibrated regularly. As you use a CO2-meter for a longer time, a measurement error could arise in the instrument, due to which you do not measure the correct values.

One condition when administering CO2 in the greenhouse, is that the CO2 is pure. If the concentration of other gases becomes too high, the crop will not grow properly. This risk will increase as the windows are opened less often. The gases able to cause most damage, are the previously mentioned gases NOx and ethylene. In practice they could cause production and quality loss of 10 to even 20%. 

These gases do not only end up in the greenhouse atmosphere as a result of administering CO2, but also, for example, due to use of machines with a combustion engine in the greenhouse (like a Pulsfog) and due to exhaust gases of trucks that are loaded and unloaded at the company. Therefore, make sure that engines are always turned off on the premises.

So, if you apply CO2 to the greenhouse air, it is important that you monitor the air quality. As such, you can take timely measures in case of too high concentrations of NOx and ethylene in the greenhouse atmosphere. The risk limit value for NOx at 40 ppb and ethylene at 11 ppb is applicable to all greenhouse crops. These values are established in case of continuous exposure to these gases.

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