What is vertical farming?

In 2010, when the Pasona City Farm opened in a 9-storey building of a Japanese company, it was a glimpse of a future where people could grow food right next to them.

In the meeting rooms, tomatoes hung from lighting fixtures and mushrooms sprouted from drawers hidden under benches. In the center of the conference room was a huge rice field. The office looked more like an agricultural museum than a workplace.

The history of vertical farming

Although the modern practice of vertical farming – growing food in trays or pipes stacked on top of each other – is considered to have started in the 1990s, the quest to farm with less land and space has been around for centuries. The stepover technique, in which a tree rises about 45 cm and grows sideways to cover 2 meters (meaning that the tree is tall enough for you to step over it), has its roots in the cultivation of trees used to grow grapes in Ancient Rome.

Vertical farming trend is spreading fast

One example is the Oishii brand of vertical farming strawberries in New Jersey. In 2021, Omakase strawberries went on sale at an upscale supermarket in New York City for $50. While this was seen by some as evidence that vertical farming could rival conventional agriculture in terms of quality, for others, the sale price highlighted the challenges of making vertical farming commercially efficient.

If we could find a way to overcome problems like budget and energy, what would a world where all food was grown on such farms look like?

Is there a way to go completely hydroponic?

The real test of the limits of vertical farming seems to be growing fruit trees.

What is vertical farming?

There is no clear definition of vertical farming, but it usually consists of shallow trays stacked on top of each other inside a building, with LED lighting on each floor. Most vertical farms have no windows; some are even built underground.

Such farms need to supply everything from water to nutrients, sunlight, pollinators and even pesticides. Vertical farms built in huge greenhouses can take advantage of the sunlight and heat, but factors such as water need to be controlled.

There are still vertical farms that use soil, but more and more farms are turning to hydroponics or aeroponics – methods where nutrient-enhanced water (in hydroponics) or water vapor (in aeroponics) is diffused directly around the roots of the plant.

“Water and nutrient yields are extremely high in hydroponic and aeroponic systems because the roots absorb them much more quickly,” says plant biologist Laura Vickers of Harper Adams University. “There’s no organic matter in the environment; there’s nothing for the plant to compete with or absorb water.

This means that the water and fertilizer needed to grow plants in vertical farms is significantly reduced. In addition, the closed, controlled environment in these systems prevents pests from entering, reducing the need for pesticides.

Benefits of vertical farming

Natalia Falagan, an engineer at Cranfield University, says that the small amount of land needed for vertical farming means that food can be grown close to cities.

Getting food to our tables quickly means less food spoilage and less invisible toxins such as mycotoxins, so a shorter supply chain means better food safety and quality.

It also means that food travels less than imported alternatives, ensuring the provenance of crops and reducing the burden on natural resources such as soil, water and atmosphere.

Challenges of vertical farming

Greens and grasses do not need flowering and fertilization. So for now, greens and grasses are the most suitable for vertical farming compared to other crops. Most fruits and vegetables require pollination, which in vertical farming has to be done artificially at a cost.

Commercial bees are already used by farmers to maximize pollination and fruiting in both indoor and outdoor farming. The almond industry, for example, is sustained by billions of honeybees that are shipped in from thousands of kilometers away and pollinate almond flowers every year. The hives are brought in on trucks and released one by one in whole groves before being taken to the next farm.

But using bees indoors brings with it a specific problem: Artificial lights interfere with the bees’ ability to navigate. To the human eye, indoor farms appear to be lit in neon pinks and purples. This is because the best way to grow plants is to expose them to blue and red wavelengths of light – two colors that appear pink or purple to our eyes from a distance. But bees’ vision mechanisms are different from ours. Bees cannot see the color red, but unlike humans, they can see it in the ultraviolet spectrum. In outdoor areas, the petals of plants reflect UV rays, helping bees to find their way around. In vertical farms where UV rays are not used, bees are at a disadvantage. Integrating these rays into indoor farms means high budgets – especially considering that these rays are freely available in nature.

Costs in vertical farming

Crops like grain are pollinated by the wind, and it’s not hard to create some indoor airflow. But while there are a number of vertical farms working on growing grains, there are only a handful of them. Grains like wheat and barley, which take months to grow, are not considered cost-effective.

The reason for this high cost is seen as the biggest obstacle to expanding vertical farming: the sheer amount of energy and infrastructure required. Being able to harvest crops all year round increases the efficiency of vertical farming, but the challenge is to somehow find a way to minimize energy use on vertical farms compared to the alternative outside with free sunlight and rainwater. This reliance on energy can also make vertical farming vulnerable to volatile energy prices.

The challenges of growing fruit in vertical farming

But Vickers says the real test of the limits of vertical farming will be the cultivation of woody crops such as fruit trees, especially given the amount of support required in a soil-free environment. But from a botanical science point of view, there is no reason why the idea of indoor orchards is impossible.

The tree is already a vertical farm. Trees take water full of nutrients and distribute it throughout their layers for the development of leaves and fruits. Nature, as always, is one step ahead of us.

Mark Horler, president of Urban AgriTech, is currently working on growing willow saplings to accelerate their growth and increase their chances of survival in indoor vertical farms before they are planted outside. The failure rate of reforestation and afforestation practices is incredibly high, Horler informs us. Indeed, very small saplings are extremely sensitive to natural elements. It is known that about 83% of newly planted trees die within 10 years. Very few trees are able to save themselves. But Horler believes that the saplings he is working on have a better chance.

There is no reason why trees cannot be grown permanently indoors to produce food, says Horler. Vertical farming is not about a single tree bearing all its fruit at once, but about thin saplings bearing fruit at frequent intervals. Most apple trees are already dwarfed versions of wild species, and it is perfectly possible to make them even smaller, he adds.

Dwarf mango trees are being studied in Asia. These smaller varieties help farmers pick the fruit more easily. In 2019, a group of researchers grew a tomato plant that looked just like a bunch of grapes. According to reports, the tiny plants become completely covered in ripe tomatoes.

Diseases in vertical agriculture

Protecting vertically grown trees and crops that take a long time to mature from disease can be tricky. In the case of greens and herbs, vertical farmers can clean between harvests and sterilize trays before the next crop is planted. But mango trees, for example, take years to mature – and this is an ideal time for mold and bacteria to grow.

In this case, the diseases live their lives just like the plant, because it has the perfect environment, heat, sufficient oxygen, access to all kinds of nutrients and a variety of plants.

According to Horler, given the ideal conditions, a vertically grown tree can nourish its fruit much more efficiently. According to Horler, the plant is programmed to make the best use of its resources. When tested, it tries harder to protect itself from difficult conditions. But in a scenario where it has ideal conditions and a comfortable life, it devotes its resources more to developing leaves, flowers and fruits; it doesn’t need all those meters-long root systems.

So, from a botanical science point of view, there is no obstacle to growing all our food in the vertical plane, but for this to become a reality, plant scientists need to come up with answers to a number of long-standing problems. And of course, urban planners, renewable energy providers and farmers have a lot of responsibility in this process.

So, from a botanical science point of view, there is no obstacle to growing all our food vertically, but for this to become a reality, plant scientists need to provide answers to a number of long-standing problems. And of course, urban planners, renewable energy providers and farmers have a lot of responsibility in this process.

These benefits and limitations of vertical farming are considered in the context of extensive cultivation in developed countries. Smallholders provide 30-34% of the global food supply. Some nations depend heavily on agriculture for their livelihoods; perhaps the idea of converting this staple food supply to vertical farming, which is entirely dependent on electric power, is unrealistic.

Yes, all of these innovations could find their place among sustainable agricultural methods in the future, but given the money involved, it is unlikely that they will all be realized in the near future.

The Pasona City Farm experiment in Tokyo, for example, has already ended. The rice has been uprooted, the tomatoes picked, the mushrooms emptied from the drawers. For now, until our cities are filled with orchards, it looks like we will have to settle for greens, small fruits and vegetables.