Why is CO2 enrichment important for greenhouses

CO2-infused or CO2-enriched greenhouses is not a new concept for farmers, as normally, these large controlled environments are required to artificially increase the supply of carbon emissions to ensure productive yields. This is because, unlike plants that grow outside, those in greenhouses tend to be more packed, so there are more plants that have to consume a limited supply of carbon dioxide for photosynthesis.

There are multiple ways to capture the required carbon dioxide that will be infused in these greenhouses, but one of those is through the use of sorbents, which capture CO2 from the outside. Using specialized equipment, these emissions can be pumped in the greenhouse depending on how much crops consume. On sunny days, the photosynthesis process is accelerated and more carbon dioxide is needed for them to grow fast.

Deploying energy-efficient devices for carbon enrichment is an even better way to carry the process, as it will have a smaller footprint on the environment, while lowering the electricity bill.

Inside a greenhouse, the typical CO2 values are around 150-200 parts per million (ppm), while at night, these increase to around 400 ppm, due to the fact that photosynthesis is put on hold. By infusing CO2 inside a greenhouse at 800-1.000 ppm, the photosynthesis process and thus, the growth of the plants, can take place up to twice as fast, leading to more productive yields. Of course, CO2 enrichment needs to go hand in hand with the rest of the things that plants need, such as water and nutrients, while the temperature plays a key role, as well.

How CO2 enrichment works

Generally, large greenhouses or multiple-unit facilities employ the use of several CO2-infusion processes, including the use of liquid CO2 and generators, which imply burning fossil fuels to generate the required CO2. These generators can be used to power and heat the greenhouses themselves, striking two birds with one stone, as the saying goes.

Generators, however, might have a disadvantage, depending on what fuel they run on. If they are fueled by propane or natural gas, the by-products outside of CO2 can cause damage to the plants. These include sulfur dioxide, ethylene and carbon monoxide and to ensure they aren't absorbed by the plants, extra filtering is required, but that increases the complexity and operational cost.

Compressed CO2 is another option, albeit an expensive one, because it includes transportation costs, as well as specialized handling techniques for the tanks and the fuel. These can, however, be a useful source of income for industrial players that capture carbon at factories and can sell the emissions to farmers.

BioTherm is one of the companies that specializes in developing CO2-enrichment systems that can also heat the greenhouses. Using a condensing boiler, the company's system burns fuel, generating CO2 in the process, which is then pumped in the greenhouse evenly and without a significant operational cost.

CO2-infusion advantages and drawbacks

Regardless of the technology used, carbon dioxide enrichment has one major advantage, that it helps increasing the growth rates for plants. This means that the plants can reach maturity quicker and thus, more yields can be harvested in a year.

If a burner or a generator is being used to produce the carbon emissions, then the by-product heat can be used to heat the greenhouse, as well, lowering overall energy costs during winter. Carbon dioxide enrichment also enables plants to grow more efficiently, reducing the amount of water they need, so it can help save water, as well.

As far as the drawbacks are concerned, additional cost is one of those, as no matter which system is being deployed, it will imply an initial investment, as well as constant operational cost, which can be higher or lower.

Infusing too much CO2 can cause harm to the plants, as they can only consume so much at a time, which is why an intelligent control system for infusion is required. Another problem is that on very hot days, supplying CO2 is difficult, due to the fact that the ventilation system also needs to be operational in order to lower the temperatures inside, dispersing the emissions alongside it.

To summarize, CO2-infusion or CO2-enrichment has its benefits for greenhouses, as they help farmers increase production, while also finding a use-case for the planet-warming emissions.

However, this process can be expensive to implement and to operate, while over-infusion can cause harm to the plants and even kill them.