Aeroponics: Growing in the mist

Due to the drought risk that has become common across our planet in recent years, hydroponics and especially aeroponics are gaining much attention for food production.

Aeroponics uses very little water and labour

Aeroponics involves plant roots hanging suspended in a closed, dark space and receiving a sprayed or misted nutrient solution, but although it uses very little water and labour, it has other aspects that have stymied its adoption since its invention in the late 1950s.

Very high capital and operating costs

Chiefly, it comes with very high capital and operating costs, and in addition, does not allow for easy transition between different crop types, notes Joseph (JC) Chidiac, a horticultural engineer at Cultivation Bioengineering in Colorado, US. He says aeroponics is undertaken in all developed nations as well as most developing nations, primarily in residential or educational settings, and that it’s used in less than 5% of controlled cultivation (greenhouse/warehouse) commercial operations.

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Chidiac has examined the merits of all types of hydroponic and aeroponics systems, and he mainly uses Shallow Aero Ebb-and-Flow (SAEF) hydroponics. – Photo: Joseph Chidiac, Cultivation Bioengineering

Aeroponics entering a new technological era

However, aeroponics is entering a new technological era, and the use of precision sensors, actuators and software, along with new patented atomizers, are helping to facilitate its advancement, says Seth Swanson, director of Global Plant Sciences at AEssenseGrows in California.

He adds that “because of the relative growth rate of the cannabis industry and the price premium for cannabis in comparison to the fresh-produce market, we see the fastest growth for aeroponics in cannabis.”

Spray nozzles

There are two ways of delivering a spray or mist of nutrient solutions to plant roots in an aeroponics system, spray nozzles and atomizers. With regard to nozzles, Chidiac explains that whilst there is wide array of quality available at various price points, the price of high quality is probably too high.

“Using spray nozzles for aeroponics necessitates the deployment of 0.25 to 1 nozzle for every single square foot (929 cm2),” he says, “and this makes the cost of using high-quality nozzles prohibitive for most operators, especially at scale, as they range from $ 15 to over $ 400 USD (€ 13 to € 356) apiece.”

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Clogging

The AEssenseGrows ‘AEtrium’ system uses low-pressure spray nozzles. Possible clogging issues, a historically common problem in aeroponics due to the components in the nutrient solutions, is picked up through the use of in-line pressure sensors. The real-time feedback they provide about particulate build-up enables immediate corrective action.

“This sensor-software communication coupled with redundant nozzle placement ensures that the root zone conditions are precisely maintained,” says Swanson. There are also multiple fine-screen filters in the system, and Swanson says that whilst it’s optimized for cannabis, it has been used to successfully produce more than 100 other plant types.

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Atomizers

Several major aeroponics firms, for example Avid Growing Systems of Niagara Falls, Canada (cannabis only), LettUs Grow of England and AeroFarms of New Jersey US (with operations in United Arab Emirates) employ atomizers (also called misters or aerosols) in their aeroponics systems. They did not respond to inquiries.

For his part, Chidiac believes that atomizers of the ultrasonic type hold merit. “New piezo disk ultrasonic atomizers are being developed…and these comprise materials that resist corrosion by the long list of mineral salts used in hydroponic nutrient solutions,” he explains. “The disks themselves are made of lead zirconate titanate and are being made thinner so that they can resonate at higher frequencies and produce even smaller droplet sizes.”

In addition, Chidiac says the way these atomizers operate, with pulses instead of continual running, provides longer equipment lifespans and reduced energy usage.

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The AEssenseGrows ‘AEtrium’ system uses low-pressure spray nozzles. Possible clogging issues, a historically common problem in aeroponics due to the components in the nutrient solutions, is picked up through the use of in-line pressure sensors. The real-time feedback they provide about particulate build-up enables immediate corrective action. – Photo: Allen Li, AEssenseGrows

Looking forward

Although it presents a highly-attractive opportunity to produce food with very little water, and continues to evolve, aeroponics will in Chidiac’s view have a hard time being adopted for commercial plant cultivation on a large scale.

Even NASA is on the fence about whether to proceed with aeroponics as a final solution for extra-terrestrial farming

“Even NASA is on the fence about whether to proceed with aeroponics as a final solution for extra-terrestrial farming or revert to systems deploying drip or wick irrigation and reusable substrate options to simplify the process and reduce the risk of component failures,” he says. “In my opinion, novel aeroponic systems will be altered to reduce energy usage further by becoming perpetually pressurized using pressure tanks and solenoid valves, such as in existing greenhouse fog cooling systems.”

He adds that overall, the superior precision of aeroponics “is not warranted for excellent results in commercial crop production and its complexity is impractical in most scenarios.”

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While the AEssenseGrows ‘AEtrium’ system is optimized for cannabis, it has been used to successfully produce more than 100 other plant types. – Photo: Allen Li, AEssenseGrows

Shallow Aero Ebb-and-Flow (SAEF) hydroponics

Chidiac has examined the merits of all types of hydroponic and aeroponics systems, and to avoid the clogging risk of spray nozzles as well as the overall high capital costs of aeroponics, he mainly uses Shallow Aero Ebb-and-Flow (SAEF) hydroponics. This involves plant roots in a sealed space receiving pulses of nutrient solution delivery at very low water pressure, with complete drainage between treatments. Chidiac claims that with this system, he is able to achieve exceptional results with a diverse array of crops, results close to those of the most fine-tuned aeroponic systems.

Aeroponics expected to grow

Swanson, however, has a different view. He believes that because aeroponics has “direct applications” to support worldwide consumer demand for transparency and efficiency and more in our global food system (and in cannabis cultivation), its use will grow. Indeed, according to Allied Market Research, aeroponics, is expected to grow at a compound annual rate of 25.6% for the next six years.