EXPLAINED – The Technology Behind Container Farming
A deep dive into the systems that make indoor container farming possible
On February 13th, 2020 we recorded the first of our two-part webinar series all about the Freight Farms Greenery. Part one focused on the technological systems that make the Greenery a growing powerhouse, capable of growing at a commercial scale 365 days a year. We were joined by Derek Baker, lead industrial designer and one of the architects of the Greenery farm. Check out the full webinar recording or keep reading for a comprehensive summary.
Greenery Layout and Key Features
The Greenery is an IoT-enabled, atmosphere controlled farm inside of a 320 square foot insulated container which allows anyone to grow food–anywhere in the world–365 days a year.
Nursery Station
When you first walk into the Greenery, you’re going to see a variety of components and systems. On the left, you will see the nursery station. The station is comprised of a worktop, underneath which are two independently controlled seedling troughs.
To the right of the table is a vertical 40-gallon seedling tank, and above the table are two dosing panels–one for main and one for seed. The dosing panels constantly monitor and control water pH and nutrient levels, using solutions from the wall-mounted nutrient tanks to maintain the correct levels. Finally, the nursery station is also where you can find the farm “brain”–a controller that allows you to automate and regulate many of the Greenery’s key functions.
Flexible Area
Opposite the nursery station, along the right wall, you have flexible space that is yours to customize based on your specific needs. This space can be used for extra storage, a second workbench, a sink station, or a microgreens rack. Alternatively, many operators choose to leave this space empty so that the Greenery can accommodate more people.
Cultivation Area
Occupying the majority of the Greenery is the cultivation area, located in the back 27 feet of the 40-foot container. The cultivation area has 4 LED arrays–two against either wall and two hanging back-to-back on a movable frame in the middle–and 2 grow frames that support 88 five-channel plant panels. Together with the central lights, the grow frames create four ‘rows’ of plants.
All the panels and the center LED arrays are mounted on a track system and can easily be moved laterally from left to right with a simple rack-and-pinion pulley system. The ability to rearrange the cultivation in this way means the operator can create extra space for larger plants, bring the LEDs closer to the plants to intensify the light, or can move rows temporarily for harvesting, cleaning, or maintenance.
Finally, at the very far back, you can find the main tank– a low-profile, 120-gallon aluminum water tank that supplies the cultivation area with water. Above it are two supply and return registers for the Bard HVAC unit which is mounted on the back exterior of the Greenery.
The 3 Main Systems: Hydroponics, LEDs & Climate Control
1. Hydroponics
Simply put, hydroponics is “soil-less farming”: Instead of having plants draw nutrients from the soil, they get all their vitamins and minerals from the water. There are multiple types of hydroponics, and we use two systems in the Greenery: ebb-and-flow and vertical drip irrigation. These two hydroponics systems make the Greenery super water efficient. The farm uses 0-5 gallons of water a day, on average–the amount of a typical home dishwasher in a single cycle.
Ebb-and-flow Hydroponics
Everything starts in the tank. Water flows into the seedling tank using whatever water delivery system you choose (there is an autofill function if you choose to hard-plumb the Greenery). The water is then pumped up into the seedling doser where sensors read the water’s temperature, pH and EC (nutrient concentration) levels. If these readings are outside of the norms pre-set for the farm, the Greenery farm controller automatically adds more nutrients or a pH stabilizing solution to the water in the tank. This water is then aerated to ensure proper mixing, after which another pump delivers the water to the two seedling troughs.
The ebb-and-flow system works by flooding the troughs with enough enriched water to saturate the seedling grow plugs (made of a sponge-like peat moss material). After a few minutes, the water is drained back into the seedling tank, and the process is repeated again later based on a preset watering schedule.
The decision to use an ebb-and-flow system for the seedlings was highly strategic. Using a horizontal system (in comparison to the vertical one we use elsewhere in the farm) helps develop stronger and healthier seedlings since growing ‘up’–instead of ‘out’–reduces the amount of gravity the new plant must fight, thus putting less strain on the plant’s stem.
Vertical Drip Irrigation
After reaching a certain size, the seedlings are transferred into the cultivation area. Just as in the nursery station, the cultivation area’s main tank is constantly monitored and maintained at the correct nutrient and pH level with regular dosing and constant aeration. The water from the main tank is then pumped up into pipes that run along the top of the 88 plant panels to evenly spaced pressure-regulated drip emitters.
The emitters allow water to flow into each one of the plant channels (440 total) at a rate of 2 gallons/hour. As the water drips down steadily, a wicking material located at the back of each channel helps to draw the water to the plants' roots. Any water that isn’t consumed flows to the bottom of the panel and out into floor gutters, which drain the water back into the Greenery’s main tank.
2. Indoor Grow Lights
In order to recreate the sun indoors, we expose plants to over 50,000 LEDs (light-emitting diodes) spread across 120 LED boards. Of these, 112 boards are found in the cultivation area, and eight are found in the nursery station.
If you’ve seen photos or visited the farm, you’ll have noticed that the LEDs give off a unique purple-pink color. That is because all 50,000 LEDs in the Greenery are either red or blue, with wavelengths of 440nm and 660nm respectively. We chose red and blue specifically because plants are picky about the type of light they absorb and have special, color-specific receptors and hormones that serve different and important functions.
Red light
Outdoors, red light is most plentiful during summertime. When plants sense an increased presence of red light, they release a hormone that keeps chlorophyll from breaking down to help the plant absorb as much light as possible. For this reason, exposing plants to red light yields large and healthy plants, and even triggers plants to produce flowers and fruits. However, overexposure to red light can cause lanky and spindly plants.
Blue light
In contrast to red light, blue light naturally occurs more during fall and winter. A plant’s blue light receptor triggers a hormone response to slow down the stem and leaf growth in what the plant perceives as a suboptimal growing environment.
For this reason, the initial reaction might be to use no blue light in your indoor grow operation but having some blue light is important. A plant’s blue-light hormone also controls “apical dominance” in plants–a phenomenon that is responsible for the main stem being larger than side stems. As a result, it is common to see plants with more exposure to blue light yield a short and bushy plant with a more complex stem structure. However, as with anything, too much can have an adverse effect: excessive exposure to blue light will result in stunted plants.
The red-to-blue ratio
The best approach is to leverage both types of light for their advantages while making sure one doesn’t dominate the other. The optimal combination for mature plants is a 5:1 red-to-blue ratio: The high level of red light keeps plants in their prime growing mode while the small amount of blue encourages stem growth. In the nursery station, we use a 4:1 red-to-blue ratio, since the extra blue light is helpful for the seedlings to develop strong stem structures from the very start.
With the Greenery, you can also isolate the red and blue LEDs, turning on just one color and not the other. This allows you to grow plants with certain desired characteristics. For example, exposure to only red light will grow larger and fuller plants and develop red or purple-colored leaves. Similarly, exposing plants to only blue light will develop denser and bushier plants.
“This level of control means that you can create custom lighting conditions for multiple varieties, or experiment with different light recipes to see what gives you the best taste or the highest yields.”
PPFD
The intensity of light is measured in PPFD (photosynthetic photon flux density). PPFD is a measure of photosynthetic active radiation, a.k.a. “PAR”.
PAR is a description of visible wavelengths of light that cause photosynthesis–generally the range between 400-700nm. To put it simply, PAR is the light that plants actually use.
PPFD is a ‘spot’ measurement that tells you how many of these “useful” photons are actually flowing over the plant canopy, and is expressed as micromoles per square meter per second (μmol/m2/s). LEDs in general are capable of producing over 500 PPFD, but the averages in the Greenery range from 200-250...here’s why:
Consider this graph, which represents the rate of photosynthesis compared to the availability of light energy (PPFD).
You can see that PPFD and photosynthesis have a direct relationship: the more light that reaches the plants, the more photosynthesis occurs. Between 0 and 300 μmol/m2/s, light and photosynthesis have a proportional relationship, but after 300 μmol/m2/s light stops having as much of an effect (seen by a more shallow curve). This is because chloroplasts–the plant cells that facilitate photosynthesis–can only process so much light at a time. Once the chloroplasts reach their limit, it becomes other environmental factors, like CO2, which affect the rate of photosynthesis more so than exposure to light.
The 300 μmol/m2/s point is key for figuring out the optimal spot between power and efficiency. In the Greenery, the cultivation area receives an average of 250 μmol/m2/s, which is at the top end of the ideal range, meaning all the energy the operator is using to power the LEDs is being used by the plant to grow. Any higher, and the operator would be wasting energy, any lower and the operator would be missing out on potential yields.
3. Climate Control
Keeping the outside out
The first part of a successful climate is ensuring that we keep any unwanted elements outside. For the Greenery, we took inspiration from traditional cold storage shipping containers for their standardized size, resilient construction, and imperviousness to pests when sealed properly.
These features, combined with an increased amount of insulation in the Greenery (R-28 Department of Energy rating compared to R-16 in standard containers), means the farm can operate in any climate in the world. We have seen previous models work in -40ºF-130ºF environments–whether that’s a dry, humid, polluted, snowy climate… We've even seen farms survive destructive hurricanes.
Keeping the inside in
We create the perfect environment inside the Greenery with a series of climate control components. One of the key components is the 36,000 BTU Bard HVAC unit. The Bard’s A/C function is activated automatically when internal temperatures exceed a “set point”, which for most plants is between 60º-70ºF.
On top of the cooling capabilities, the Bard also has an integrated economizer and dehumidifier. The economizer minimizes the Greenery’s power usage by sensing the external temperature and–when appropriate–using cold outdoor air to cool the farm instead of running the compressor. The dehumidifier works to condense ambient moisture, and can collect up to 1.88 gallons/hour based on environmental conditions. The water is recycled back into the main tank and fed back to the plants, creating a closed-loop system.
Once the Bard introduces cooler, dried air into the Greenery, a series of overhead and ducted fans create airflow throughout the farm in order to standardize the temperature and humidity within the container. This is an important part of the climate control system: a lack of airflow can lead to microclimates, stagnant air, and plant disease.
Finally, there is CO2 regulation. With CO2 the trick is to keep levels high enough to facilitate photosynthesis while also making sure levels are safe for the operator in the enclosed space. For this reason, the Greenery carefully monitors CO2 levels, releasing more from a storage tank directly to the ducted fans in the grow rows along with cool air. This delivers CO2 directly to the plants, while also creating a wind-like effect that helps strengthen plant stems. Contrastingly, if there is too much CO2 present, the Greenery’s exhaust fan will be activated to release CO2 out of the container.
Farmhand®
We talk a lot about creating or maintaining the “perfect growing environment”, but how do we know what that actually is? That’s the job for farmhand!
Farmhand is our IoT software which uses smart sensors to aggregate data and control certain farm functions. When setting up the Greenery for the first time, the operator and our Client Services team will create set conditions for temperature, humidity, CO2, pH, EC, etc. If any of these levels deviate from the norm, farmhand will activate the right component to re-establish control. Furthermore, farmhand will also give you access to historical data so that you can track which conditions yield the best results, or work with the Freight Farms support team to troubleshoot any problems. Best of all? It can all be done remotely! Use a phone, tablet, or desktop to “see” and control the farm from anywhere in the world (with internet access).
User advantages
To quickly summarize, here are the most advantageous aspects of the three Greenery technologies discussed in this webinar and blog:
| Hydroponics | Indoor Grow Lights | Climate Control |
|---|---|---|
Soil-less farming means a less messy process. Hydroponics always delivers the right amount of nutrients to plants. Superior water efficiency, making the operation more sustainable than conventional farming methods. |
Isolated red and blue LEDs gives plants the optimal lighting. Carefully calculated PPFD ensures maximum power and efficiency. Ability to create extended days (18-20 hours) can speed up plant growth. |
Independence from outdoor elements means year-round production. Protection from external elements (averse weather, pests, pollution, etc.) Remote control and monitoring with farmhand® gives you freedom. |
Audience Q&A
“Which crops grow best inside the Greenery?”
While you can grow most plants in the Greenery, there are certain crops that will make more ‘business sense’ as they will have higher yields. Crops that grow best in this scenario are: lettuces, leafy greens (arugula, Swiss chard, kale, etc.), herbs, root vegetables, edible flowers, and certain species of vining crops. Learn more in our complete crop guide.
“Why choose hydroponics over aeroponics?”
Aeroponics uses the same idea of nutrient-enriched water, but instead of irrigation systems, it involves misting the roots that are suspended in the air. We chose hydroponics because it's more reliable with much lower rates of failure. While aeroponics have their benefits–such as roots getting more exposure to oxygen–the upfront costs are much higher, and the system typically requires more starting experience with plant cultivation.
“Have solar panels been successfully used to power the farm?”
Several of our farmers have successfully added solar panels to their farms after purchase. However, it would be hard for a farm roof’s worth of solar panels to provide all the electricity needed to run the farm.
“Does Freight Farms ship overseas?”
Yes we do! The Greenery is designed for easy shipping by truck, train, or boat. As of February 2020, we have farms in 25 countries.
“Do you provide training to new farmers?”
We sure do! One of the main functions of our Client Services team is to support and train new farmers with a two options. The first is an intensive training at Freight Farms HQ in Boston, where you will learn everything from crop scheduling and sensor calibration, to food safety protocols and marketing strategies. For those not able to come to Boston, we offer a self-paced online version that uses lectures, videos, diagrams, and quizzes to teach all the same information. You can learn more about training when you visit our overview of client services.
View both parts of our Greenery webinar series!
Part two focuses on plant science, vertical farming, and crop scheduling. Watch for free now.
Want to learn more about the Greenery?
Download our 47-page product booklet for all the specifications and components.
