Optimizing CO2 Levels in Controlled Environment Agriculture

Almost all fourth-grade science students have created a terrarium in a jar. These experiments often follow a similar pattern.

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For the first week or two, the plants seem healthy and grow well. However, if the terrariums are not set up correctly, problems typically start to arise, leading to wilting plants. This is generally because the terrarium does not maintain the right balance of CO₂ in its environment. The same issue can arise in controlled environment agriculture (CEA), albeit on a much larger scale. Without proper monitoring and control and the right tools and technology, inappropriate CO₂ levels can significantly affect plant growth and health.

CO₂ and CEA: Fine-tuning Balance

CO₂ has a unique place in controlled environment agriculture, with the capacity to impact the success or failure of an indoor farming operation.

CO₂ can lead to similar issues in indoor agriculture as in any other enclosed space; for example, incorrect CO₂ levels can lead to decreased yields, hindered plant growth, and even crop failures.

It has a similar effect on livestock, potentially stunting growth rates, reducing reproductive performance, and adversely impacting feeding patterns.

CO₂ is also a key component in plant photosynthesis; however, without exposure to the gas, plants will not grow at all.

Anyone designing or overseeing controlled environment agriculture systems will be aware of how much time and effort can go into fine-tuning conditions within the system. A harvest or yield can face major problems if variables such as temperature, humidity, or lighting fall outside of their acceptable range.

This situation mirrors issues in traditional farming, where too much rain, insufficient sunlight, or extreme temperatures can lead to reduced crop yields or crop failure.

Maintaining the Ideal CO₂ Range for CEA

There is no one-size-fits-all answer to the ideal range of CO₂ in a controlled environment agricultural setting. Different plants have different environmental requirements, with various stages of growth requiring differing CO₂ levels.

For example, mature plants generally require less CO₂ than those in the vegetative stage. Additionally, specific crops like cucumbers and tomatoes benefit from slightly higher CO₂ levels compared to crops such as lettuce.

It is generally advisable to aim for between 1000-1500 ppm of CO₂ for most crops, but this may vary based on factors such as lighting intensity, airflow within the growing environment, or the type of crop being grown.

The ideal CO₂ range for livestock like pigs or chickens that spend a lot of time indoors is lower at around 600-800 ppm.

Advanced CO₂ Sensors for Indoor Farming

In an ideal setting, controlling CO₂ levels for indoor farming operations would be as straightforward as opening a window and waiting until levels reach an appropriate point. However, this is not the case.

Indoor agriculture, particularly for growing vegetables, requires continuous monitoring. Ambient conditions must be constantly managed, but with the right systems and automation—such as a computer handling minute-by-minute management—effective control is achievable.

CO₂ levels are typically regulated using HVAC systems equipped with advanced, robust CO₂ sensors integrated throughout the climate control system. This setup allows for real-time monitoring and adjustments and provides valuable historical data to inform future decisions and enhance operational efficiency.

NDIR (Non-Dispersive Infrared) sensors are the most commonly used technology for maintaining optimal CO₂ levels in agricultural settings.

Using NDIR CO₂ Sensors for Indoor Agriculture

NDIR CO₂ sensors measure the amount of infrared light passing through a gas sample. CO₂ molecules absorb specific wavelengths of infrared light, allowing the sensor to accurately determine the carbon dioxide concentration by detecting changes in light absorption.

NDIR technology provides a direct and reliable method for assessing CO₂ levels, making it widely used in modern indoor farming due to its non-invasive nature and low maintenance requirements.

Compared to other CO₂ monitoring options, NDIR sensors offer several advantages:

• Accuracy and reliability: These sensors provide precise CO₂ measurements by specifically targeting the gas’s absorption spectrum. This is essential for optimal plant growth.
• Straightforward integration with climate control systems: NDIR sensors’ robust design allows them to be seamlessly integrated into existing climate control systems. This affords crops a stable environment without the need for ongoing manual oversight.
• Minimal calibration requirements: Unlike other types of CO₂ sensors, NDIR CO₂ sensors do not need regular recalibration because they are designed to compensate for potential drift throughout their long, useful lives.

NDIR CO₂ sensors are available in two styles: single-channel and dual-channel.

Single-channel NDIR sensors make use of one wavelength for CO₂ measurement, relying on software algorithms to maintain long-term accuracy. In contrast, dual-channel NDIR sensors use two wavelengths for measurement, affording them built-in drift compensation for improved reliability over time.

Selecting the Most Ideal NDIR CO₂ Sensor for Indoor Agriculture

A dual-channel NDIR sensor is particularly well-suited for indoor agriculture. This type of sensor is designed for environments where spaces are consistently occupied or where CO₂ levels are relatively stable, such as in greenhouses or other indoor growing operations. Its dual-channel configuration allows for more precise and reliable monitoring in such conditions.

Indoor agriculture demands consistent and controlled environmental conditions. Dual-channel NDIR CO₂ sensors are ideally suited for such environments, as they excel in settings with minimal fluctuations in CO₂ levels.

Proactively Managing CO₂ in an Indoor Ecosystem

Nothing exists alone in nature, and the same can be said of indoor agriculture. Every element that must be managed is connected to and affects other elements.

It is important to consider a range of factors when managing CO2 alongside other ambient conditions in an indoor agriculture operation.

• Temperature: Temperature and CO₂ levels are closely linked. While higher temperatures can enhance CO₂ assimilation to some extent, excessive heat can stress plants. Maintaining a balance is crucial to ensure efficient photosynthesis while avoiding overheating. 
• Photosynthesis rates: Photosynthesis rates increase with CO₂ concentration, but only to a certain degree. A combination of excess CO₂ and inadequate light and nutrients offers no benefits to growth and can be harmful or wasteful. 
• Ventilation: Appropriate ventilation helps balance CO₂ levels by introducing fresh air and expelling excess heat and humidity. It is important to prevent over-ventilation so as not to waste CO₂, therefore maintaining its optimal levels for growth.  
• Humidity: Increased humidity can boost plants' CO2 absorption, promoting growth. However, excessively high humidity can facilitate the spread of diseases. Balancing humidity with CO₂ levels is essential for fostering healthy, vigorous plants. 

Straightforward, Connected CO₂ Management

Even when considering an environment where ambient conditions are comparatively stable, ongoing consideration must be given to keeping any metric within an acceptable range, whether this is lighting levels or air pressure.

Rather than hiring a large number of workers to monitor and manually adjust every aspect of controlled environment agriculture settings, smart advanced sensor technology can be used to maintain appropriate CO₂ levels at all times.

IoT- (Internet of Things) enabled sensor technology can be integrated into sophisticated HVAC and building management systems, essentially removing the need for manual CO₂ management.

It is possible to program these sensors to work with other connected devices, essentially creating an indoor ecosystem that is almost completely self-regulating. This can be combined with real-time alerts and historical data tracking to ensure that indoor agriculture conditions are maintained and optimized over the long term.

For example, if an unexpected event causes CO₂ levels to rise beyond normal parameters, agricultural IoT CO₂ and airflow sensors can notify operation managers via a building management system while automatically triggering countermeasures.

Once any potential risk has been averted, managers would have data available to help them understand what caused the spike in CO₂ levels and prevent this from occurring again in the future.

IoT-enabled CO₂ sensors for greenhouses or other controlled environments facilitate greater control over indoor farming. This opens the doors to improved yields, healthier plants, and more efficient operations for both managers and designers of indoor agricultural systems.

Controlling Controlled Environment Agriculture

While it is impossible to create an indoor environment with perfectly constant ideal conditions, leveraging the right technology and careful management can closely approximate this ideal.

In addition to CO₂ sensors, various agricultural sensors can monitor humidity, temperature, light levels, and other critical factors—all essential for a successful indoor growing operation.

Employing the best available hardware and software solutions is crucial to maintaining an indoor ecosystem that closely mimics natural conditions.

Acknowledgments

Produced from materials originally authored by Amphenol Sensors.

This information has been sourced, reviewed and adapted from materials provided by Amphenol Advanced Sensors.

For more information on this source, please visit Amphenol Advanced Sensors.