CO2 sensorCase Study: Effectiveness of CO2 Concentration Control in Greenhouse Horticulture

One of the challenges in the greenhouses and plant factories used in greenhouse horticulture is improving crop yields and quality. Toward that end, it is necessary to accurately measure CO2 concentrations and supply CO2 at the right times to promote photosynthesis in plants.

Although the global average concentration of CO2 in the atmosphere is roughly 400 ppm, it is lower in greenhouses during the day due to the promotion of photosynthesis. Thus, the customer needed to correctly measure CO2 concentrations below 400 ppm, but measurement errors by the CO2 sensors they were using made it difficult for them to control the concentrations. Furthermore, because CO2 sensors tend to produce measurement errors as they age, the customer needed to calibrate them using calibration gas or atmospheric pressure, a process that took a lot of time and effort.

Another challenge was to reduce costs by limiting fuel consumption to the system supplying thermal energy and CO2 to the greenhouses.

The customer’s main objective was to improve crop yields and quality by optimizing growth in greenhouses.

Controlling CO2 concentrations by supplying the right amounts of CO2 at the right times is key for achieving this, and the customer needed CO2 sensors capable of accurately measuring concentrations below 400 ppm with highly consistent readings over the long term.

Murata’s CO2 sensors are single-beam non-dispersive infrared (NDIR) sensors capable of accurately measuring CO2 concentrations below 400 ppm and correcting the deterioration of CO2 light sources, optical paths, and photodetectors.

Their accuracy, long-term consistency, and durability are outstanding.

With our unique mechanism and algorithm-based automatic calibration using the local environment, our CO2 sensors are maintenance-free.

Nepon’s photosynthesis promotion system promotes photosynthesis and improves crop quality by supplying the right amount of CO2 to greenhouse interiors at the right times.

They saw the advantages of using Murata’s CO2 sensors, which provide the high accuracy of CO2 concentration measurement, durability, and maintenance-free automatic calibration they need to control CO2 in greenhouses.

In greenhouse horticulture, it is important to provide plants and crops with consistent environments optimized for growth. To achieve this, sensing of data (e.g. temperature, humidity, solar radiation, illuminance) inside the greenhouses is essential. CO2 concentration is especially vital for plant photosynthesis; therefore, accurate control of CO2 concentration is key.

However, sensing and controlling CO2 concentrations in greenhouse horticulture is no simple task. CO2 concentrations in greenhouses vary greatly from day to night—they increase at night when plants respire and decrease during the day because of photosynthesis. Additionally, various factors affect greenhouse environments, including seasonal variance in the amount of solar radiation and outdoor temperatures, greenhouse size, and the type of plants and their daily growing conditions.

Greenhouse horticulture requires sensors that are durable enough to withstand these changes in greenhouse environments while providing accurate measurements. Murata’s CO2 sensors accurately measure rapidly changing CO2 concentrations in greenhouses throughout the seasons, and by linking to climate control panels make it possible to maintain greenhouse environments that are ideal for photosynthesis.

This makes it possible to control greenhouse environments in line with harvest plans and how well the crops are growing while also reducing costs, leading to improved yields and quality.

We interviewed Hisashi Taguchi, who grows tomatoes in two differently sized greenhouses (18 a and 13.5 a) in the city of Kazo, Saitama Prefecture. He uses Murata’s carbon dioxide generators, carbon dioxide controllers, and duct fans in both greenhouses.

In the past, Mr. Taguchi used the equipment to raise the CO2 concentration to 1,000 ppm in the morning, but the effects were not so good. However, since adding Murata’s CO2 sensors and control panel, he has been able to use fuel more efficiently while adding CO2 at low concentrations during the day.

He changes the settings from 400–440 ppm to 410–470 ppm depending on the time of year, and is also looking into applying fertilizer in a way more suited to the CO2 application. In fact, Mr. Taguchi said his yields have improved by about 30%.

“It stands to reason that if you grow things the same way, you make less money,” he said. “Productivity and profits only increase when you combine science-based methodology with new technologies. I would definitely recommend this to other growers. It’s fantastic!”