Indoor hydroponic systems

In recent years, agricultural practices have rapidly developed due to improvements in technology, leading to better disease resistance, greater nutrient density, and overall higher yields for various crops.

One of the most important agricultural developments driving such increased productivity has been recent widespread popularization and commercialization of indoor hydroponic farming systems. The main components of modern indoor hydroponic farms include indoor growing spaces, nutrient solutions, pumps, timers, artificial lights, plants, water, and often vertical growing chambers where the plants grow directly over each other in series.

These systems offer several advantage over other growing systems:

• Eliminates need for soil
• Full control over the environment
• 5-30x increased crop yields per square foot, especially in vertical hydroponics systems
• Requires 70-95% less nutrients and water
• Fewer pest issues
• Permanent growing seasons of temperature sensitive crops

What plants need to grow and how to add it

To grow, plants need a combination of sufficient heat, sunlight, and 18 nutrients derived from soil, air, and water. The most common nutrients used by plants are the macronutrients carbon, oxygen, hydrogen, nitrogen, phosphorous, and potassium. Carbon is the most abundantly used macronutrient, required for both photosynthesis and the formation of cellulose and starch.

Since the beginning of agriculture, humans have been helping plants to grow faster and stronger by adding fertilizers to the soil. However, because carbon, oxygen, and hydrogen are mainly derived from air, it can be challenging to add them by conventional granular and water soluble fertilizers. Therefore, the primary method to increase levels of these nutrients is by adding gases to the growing environments.

CO₂ and its ideal concentration for growing plants

One of these “fertilizer” gases is carbon dioxide (CO₂), an important greenhouse gas which originates naturally from volcanic eruptions and wildfires, and artificially from burning fossil fuels, cement production, deforestation, and biomass burning. CO₂, as the main source of carbon for plants, greatly improves plant growth when it is added as a gas at ideal concentrations. Major carbon sinks such as plant life and the oceanic and continental lithosphere trap excess CO₂, storing carbon in greater amounts than exist in the atmosphere. The Earth’s oceans alone capture as much as fifty times as much CO₂ as exists in Earth’s atmosphere.

Before the industrial revolution, CO₂ levels in the atmosphere existed around 280 PPM. However, due to the effects of the industrial revolution this has risen to about 420 PPM. According to recent studies, this increase in global CO₂ has also lead to an increase in plant growth and plant CO₂ use by 30%. Although this aspect of global warming has been beneficial for plants, it still leads to overall negative climate outcomes when offset with the effects of water scarcity.

CO₂ control in indoor growing environments

Within an indoor farm where water scarcity is not an issue, the optimal concentration of CO₂ for most plant species is ideally raised to around 1000 PPM. CO₂ control is especially practical for indoor growing environments such as indoor vertical hydroponic farms as unventilated indoor growing environments will deplete their natural CO₂ levels over time, leading to an eventual decrease in crop yields. Furthermore, CO₂ control is best suited for indoor growing environments since CO₂ cannot escape outdoors, thus being entirely utilized by plants.