Supplying extra carbon dioxide is a frequently used method to increase the yield of greenhouse horticultural crops. Depending on your location, the amount of carbon dioxide in the outdoor air is 350 parts per million. This amount is sufficient to grow plants, but if you place many plants together in a greenhouse, the carbon dioxide level decreases because all plants use carbon dioxide for photosynthesis. By adding CO2 (CO2 enrichment) it is possible to increase the photosynthetic potential of the crops, especially on sunny days.
CO2 enrichment in greenhouses
Methods for CO2 enrichment
Supplying CO2 may lead to local variations in CO2 concentration throughout the greenhouse, because the concentration declines from source to sink. Horizontal and vertical gradients in environmental conditions are disadvantageous, but inevitable. The most important thing is to prevent a decrease in the homogeneity of plant growth and crop production.
In a distribution network, a high CO2 concentration is found near the distribution pipes and a low level near the ridge, or near the open ventilation windows. In Dutch greenhouses, the distribution lines of CO2 are placed underneath the growing gutter, near the crops. With the natural diffusion of the carbon dioxide to the top of the greenhouse, the plants are sure to benefit from the CO2 enrichment.
The most common method of CO2 enrichment for greenhouse application is the combustion of fossil fuel. The flue gases used must not contain dangerous amounts of harmful components. Therefore, the most used fuel for CO2 enrichment in Dutch greenhouses is natural gas. With the combustion of 1 m3 of natural gas, approximately 1.8 kg CO2 is generated.