Without the process of photosynthesis, light energy would not be able to transform carbon dioxide into oxygen, an essential element for the life and growth of our crops. CO₂ enrichment promotes plant development, particularly in vegetables, as it leads to higher yields and better quality. CO₂ levels must be continuously monitored with a CO₂ analyser to ensure both greenhouse crop productivity and harvest quality. By controlling CO₂, growers can expect increased yields and improved product quality.
How to ensure accurate CO2 control?
Did you know that in addition to oxygen, our plants also produce sugar?
Photosynthesis is the source of the oxygen we breathe, as well as the food we eat.
Without this process, light energy could not transform carbon dioxide into oxygen.
Photosynthesis takes place in the presence of light, water, carbon dioxide and nutrients, all of which are essential for plant growth.
The effectiveness of this mechanism can vary according to several parameters, including the concentration of carbon dioxide in the surrounding air.
In addition to carbon dioxide, the plant needs sugar to grow. And the key point is that it produces this sugar itself.
Other essential elements include minerals, water, nutrients and light.
The photosynthesis reaction is then as follows:
CO₂ + H₂O + Light → Sugar + O₂
More precisely, the plant uses this sugar as fuel. It enables it to generate new cells and, in a way, to "breathe".
The answer is simple: to optimize the photosynthesis process, thereby stimulating plant growth and helping to control it.
Monitoring CO₂ in greenhouses is also essential for managing exposure levels, both for plants and workers, ensuring safety by keeping CO₂ concentrations within recommended limits.
Greenhouse agricultural production is now a fast-growing reality worldwide, with some 405,000 hectares of greenhouses spread across Europe.
The last 20 years have seen a revolution in greenhouse cultivation and technology.
Until recently, a tomato yield of 100 tonnes/ha in a greenhouse was considered a good performance... Today, a harvest of 600 tonnes/ha is not unusual in high-tech greenhouses.Hans Dreyer, Director of the Plant Production and Protection Division at the Food and Agriculture Organization of the United Nations.
You'd think that regions of the world with abundant sunshine wouldn't need greenhouses. But this is not the case.
Again, depending on the crop, CO2, like air temperature and velocity, is a key parameter, and its optimum level varies.
The concentration of CO2 in ambient air is known to have risen dramatically since the Industrial Revolution, and even more rapidly today.
However, its average level is currently around 400 ppm (parts per million), or 0.04% of the air we breathe.
Under the right light and temperature conditions, tomatoes grow best at 900 ppm and cucumbers at 700 ppm.
In both greenhouses and grow rooms, setpoints are used to automatically control CO₂ levels and ensure optimum plant growth.
It therefore seems obvious that CO2-controlled atmospheres, and hence greenhouses, need to be developed in all regions to meet the challenge of human food supplies in the years to come.
The Netherlands is known as a pioneer in controlled-atmosphere greenhouse cultivation. With a considerable and ever-growing number of 9,000 large greenhouses, occupying 0.25% of the country's total surface area, this market represents a significant part of the country's GDP. 150,000 workers are employed and 80% of products are exported.
Spain is also renowned for having one of the largest greenhouses in the world. It is located in Almeria, where the greenhouses cover an area of almost 200 km².
Additional CO₂ should be brought in during periods of sunny weather, but not on cloudy days or at night.
CO₂ can be extracted from burners using fuel oil or natural gas. In this case, it is essential to take care to avoid the presence of toxic gases in the greenhouse - be they gases harmful to plants (SO₂, ethylene, etc.) or humans (carbon monoxide). Combustion-powered CO₂ generators can also provide heating for the greenhouse, making them particularly effective for large-scale operations.
Another option is to use pure liquid CO₂, purchased from specialist suppliers. In this case, pressure regulation in CO₂ tanks and distribution systems is essential to control flow and guarantee safety.
The most common method of CO2 enrichment for greenhouse applications is the combustion of fossil fuels. And the most widely used fuel for CO2 enrichment is natural gas. Burning one m³ of natural gas generates around 1.8 kg of CO2.
The addition of CO2 can then lead to local variations in CO2 concentration throughout the greenhouse. Horizontal and vertical gradients in environmental conditions are disadvantageous, but unavoidable. The most important thing is to avoid a reduction in the homogeneity of plant growth and production.
For example, in the case of a distribution network, a high concentration of CO2 is found near the distribution tubes and a low level near the crest, or near open ventilation windows. In this case, it is recommended to place the CO2 distribution lines at a low level, as close as possible to the crops.
In this way, the natural diffusion of carbon dioxide towards the top of the greenhouse will ensure uniform CO2 enrichment along the vertical axis.
Horizontal distribution is also a challenge, since the entire greenhouse surface must also contain the same amount of CO2, so that all plants grow at the same speed and maturity and quality are uniform throughout the crop.
To ensure volumetric homogeneity (both horizontal and vertical) of theCO2 concentration in the greenhouse, the best strategy is to measure it at several points in the greenhouse.
This can be done with several gas analysers and/or by multi-point sampling with a single analyser, depending on the size of the greenhouse and the available budget.
In the case of a large greenhouse, severalCO2 controllers will be used to cover the entire volume. To ensure the best representation of the atmosphere, each controller will simultaneously measure several smaller zones (usually 4 or 6).
This optimized strategy ensures that CO2 is distributed evenly over all crops.
Fuji Electric's CO₂ sensor is a reliable device specially designed for greenhouse applications. Key features include adjustable parameters, alarms and connectivity options, making it versatile and easy to integrate into different greenhouse environments.
The Fuji Electric ZFP CO2 controller for greenhouses is a dedicated NDIR (Non-Dispersive Infra-Red) gas analyser . It was designed years ago for this purpose and has been improved with experience. The CO₂ sensor offers rapid response to variations in CO₂ concentration, enabling real-time detection and alerts to maintain optimal air quality for plant growth.
More than 10,000 ZFP CO2 monitors are currently in use across Europe to optimize our food production by enhancing photosynthesis through CO2 fertilization.
Equipped with its own internal filter and pump, this infrared analyser is able to draw in ambient air around its own position, and then from distant areas via a network of sampling pipes.
A common strategy, like the one illustrated opposite, is to draw in air from several areas to ensure homogeneous CO2 in the targeted zone.
Installation of the CO₂ ZFP controller is straightforward, and its unique stability allows an annual calibration frequency.
The Fuji Electric CO2 monitor's non-dispersive infrared technology has been renowned since the 1960s for its robustness and signal stability in the harshest weather conditions.
The sensor operates using an infrared (IR) source that directs light waves through a cell filled with a sample of air. This air moves towards an optical filter located in front of an IR light detector.
The IR light detector measures the amount of IR light passing through the optical filter.
The IR radiation band also produced by the IR source is very close to the 4.26 micron absorption band of CO2.
As the IR spectrum of CO2 is unique, the wavelength match of the light source serves as a signature or "fingerprint" to identify the CO2 molecule.
As infrared light passes through the cell, the CO2 molecules absorb the specific band of infrared light and allow the other wavelengths of light to pass through. At the end of the detector, the remaining light strikes an optical filter that absorbs all wavelengths of light except the wavelength absorbed by the CO2 molecules in the sample cell. Finally, an IR detector reads the remaining amount of light that has not been absorbed by the CO2 molecules or the optical filter.
The difference between the amount of light radiated by the IR source and the amount of IR light received by the detector is measured.
As the difference is the result of light absorption by the CO2 molecules present in the air inside the cell, it is directly proportional to the number of CO2 molecules. This data is then processed by the internal electronic board and output as a 4-20 mA signal used by the CO2 enrichment system.
Fuji Electric has decades of experience in the manufacture of advanced gas analysis equipment, guaranteeing high-quality performance and proven reliability.
The ZFPanalyser is also suitable for use in the grow room, offering reliable CO₂ monitoring and control to ensure optimum plant growth.
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Effective water and nutrient management is essential to support vigorous plant growth and maximize greenhouse yields. Each type of plant has specific needs, but a balanced nutrient solution with a pH between 5.5 and 6.5 is generally ideal for most crops. The use of a flow meter enables growers to accurately monitor water consumption and adjust irrigation schedules according to actual plant needs, thus avoiding under- or over-watering.
Maintaining optimal environmental conditions - such as temperature and humidity - is equally important. High levels of carbon monoxide can be harmful to plant health, which is why it's important to ensure adequate ventilation and good air quality. By closely monitoring these parameters, growers can create an environment that promotes healthy growth, reduces the risk of nutrient deficiencies and helps prevent the appearance of pests and diseases.
Constant attention to water and nutrient management not only increases yields, but also enhances the health and resilience of greenhouse crops.
Protecting greenhouse crops against pests and diseases is essential to maintaining high yields and ensuring the long-term viability of your operation. Growers can combine biological, chemical and cultural control methods to limit threats. Regular monitoring of plants to detect the first signs of infestation or disease is essential, as swift action can prevent spread and major damage.
A CO₂ monitor can be a valuable tool in this process, as sudden variations in carbon dioxide levels can indicate the presence of pests or diseases affecting plant respiration. Maintaining a clean, well-ventilated greenhouse environment also reduces the risk of pest outbreaks.
By implementing a proactive pest and disease management strategy, growers can protect their investment, maintain healthy plants and guarantee consistent, high-quality production.
The design and layout of a greenhouse are key factors influencing plant performance, operational efficiency and running costs. A well thought-out greenhouse must offer optimum light intensity, precise temperature control and efficient ventilation to create the best environmental conditions for plant growth. When designing, specific crop needs, local climate and available space must be taken into account, so that each plant benefits from an adequate supply of light and air circulation.
A sealed greenhouse provides enhanced control of carbon dioxide, temperature and humidity, offering growers the ability to maintain each parameter at the desired level to maximize productivity. However, this approach requires rigorous monitoring and management to avoid problems such as excess humidity or CO₂ build-up.
By investing in a carefully designed and fitted out greenhouse, growers can optimize plant growth, increase yields, reduce energy costs and improve the overall efficiency of their operation.
Proper post-harvest handling and storage are essential steps in the greenhouse production process to maintain the quality and value of your crops. Gentle handling reduces the risk of damage, while storage in a cool, dry environment preserves freshness and extends shelf life. Using a CO₂ controller or monitor is a simple and affordable solution for maintaining optimum carbon dioxide levels during storage, which can further improve crop longevity.
Monitoring temperature and humidity is also crucial, as excess moisture can lead to spoilage and reduce the value of the crop. A flow meter can help track water consumption and prevent unwanted moisture build-up during storage.
By applying good post-harvest handling and storage practices, growers can reduce losses, maintain high product quality and increase customer satisfaction - ensuring that the work invested in production pays off all the way to market.
