Vertical farming is spreading across Europe and research is being done into all kinds of new crop types. But there are still challenges to be overcome.
Empty office buildings, where crops can grow stacked on top of each other, layer after layer. Or in a container in your neighbourhood, vertical farming offers many possibilities. You can grow crops wherever you want. You don’t need fields for it. The cultivation is sustainable, efficient and fully controlled. You don’t need any pesticides, there are no nutrient emissions and the water consumption is only between 2 and 4 liters per kilo of vegetables. There is still a big problem: energy consumption. We are still working hard on that.
Vertical farming is on the rise all over Europe. It is particularly suitable for growing crops in urban areas where space is at a premium. It can even guarantee food security in countries less adapted to conventional agriculture. But although the first crops are already on sale in some countries, it will certainly be several years before products from vertical farms reach the supermarket shelves en masse.
Changing diet and increased demand
Along with cultured meat, vertical farming is often presented as the key solution to combat future food crises. But why do we need vertical farms anyway? Why don’t we just keep doing it the old fashioned way, like we’ve been doing for the past 10,000 years?
The demand for food is increasing every year. According to the United Nations, the world population will grow to 9.7 billion people in 2050. All these people need food. But growing crops in the traditional way is becoming an increasing problem. Due to climate change, growing conditions are changing, so that you can no longer grow some crops where you used to be able to. Extreme weather events and severe storms destroy more crops every year. And in some places the soil is less nutritious than it used to be.
As well as having to meet the future demand for fresh food, our eating habits are also very different from a century ago. “We no longer eat seasonally. In the winter we eat salads and berries that we import,” says CEO Anders Riemann of Nordic Harvest, Europe’s largest hydroponic farm.
Growers in a vertical farm wear protective clothing to prevent unwanted bacteria from entering the farm. In this way they can avoid the use of pesticides.
Summer harvest from the Arctic
Vertical farms can be built almost anywhere. Which means that you no longer have to import kiwis from New Zealand, but that you can grow them in such a farm in your own region. This saves a large amount of CO2 emitted.
How does it work?
“For me, complete control is the big advantage of vertical farming. We can really optimize the process and know exactly how much we want to grow and of what quality,” says Leo Marcelis, professor of Horticulture and Product Physiology at Wageningen University & Research.
From water supply to daylight, temperature, and access to minerals and bacteria. Vertical farming takes place under extremely controlled conditions. Crops are grown indoors, with LED lights instead of sunlight. LED bulbs are small, durable, cost-effective, and they don’t emit any heat. As the sun sets at the end of the day, these lights can shine for as long as needed.
The farmer can manipulate the plant’s day and night rhythm to optimize the growth yield. During the day, plants form starch in the leaves, which is broken down into sugar and transported to the rest of the plant at night. Some plants need more than 12 hours of light per day to grow, others need less. Vertical farming allows any type of plant to get the amount of daylight it needs to grow at its best.
Growth with different colors of light
The colors of these lights are particularly important to optimize growth yield. Researchers have mainly focused on the effect of red, blue and green light on plant growth. Red light is very efficient for photosynthesis, but plants also need some blue light, which is especially useful for chlorophyll production. For some time, researchers sought to reduce the use of green light, believing it did not contribute to photosynthesis.
However, a 2016 study from Utah State University shows that the green light can drive photosynthesis to lower leaves more efficiently than red or blue light can. The farmer can use different color combinations to emphasize different traits. With the right combination, the farmer can grow plants that are much more nutritious than conventional farming. This can be useful as most plants have become less nutritious in recent decades. Another combination can be used to increase the growth rate so that more food can be produced at one time. From an economic point of view, that could be desirable, as vertical farming remains cost-intensive.
But there are more reasons why this method is so popular. Vertical farming does not require pesticides. Growers can grow exactly the amount of crops they want, within a set time frame and of a specific quality chosen by themselves. Weather or seasonal conditions no longer affect production. More food can be grown on a smaller surface area.
Agriculture without fields
Vertical farming today mainly comes in two forms: hydroponic and aeroponic. According to Leo Marcelis, both techniques are excellent alternatives. In hydroponics, plants grow on shelves with their roots in nutrient-filled water instead of soil. It is considered the easiest of the two main systems.
Nordic Harvest has an experimental farm near Copenhagen where it grows different types of salads, kale and spinach. The farm is surrounded by other industrial complexes. It is a building the size of a football field. In 2023, the company wants to expand with a farm in Oslo, followed by farms in Scandinavia and Finland.
According to Riemann, Nordic Harvest’s current production capacity is already noticeable: “We produce about 1000 tons of vegetables annually. The Danish market consists of about 20,000 tons per year. 6,000 tons are grown conventionally and the rest is imported.” The vegetables are leafy greens. As vertical farming expands, it will make up a larger percentage of food production. Other companies growing crops in vertical farms are Jones Food Company in Great Britain, Hydropousse in France and Robbes Lilla Trädgård in Finland.
Aeroponically grown crops have their roots in the air. India Langley, food systems researcher and PR lead at indoor farming technology provider LettUs Grow, explains how it works. “You have a series of nozzles with very small holes with which you atomize the nutrient solution. That solution is applied to the roots of the free-hanging crops.”
Aeroponics was developed in the 1990s when NASA was looking for ways to grow plants in space. According to the US National Center for Appropriate Technology, aeroponics is “by far the most efficient plant breeding system for vertical farms.”
In an aeroponic system, the roots have easy access to oxygen. The plant’s growth rate is up to twice that of a hydroponic system, where the plant would absorb dissolved oxygen in the water. It is still not used as much as hydroponics, due to its complexity. The nozzles used in production can easily clog or break. But LettUs Grow has found a solution to the problem.
“We have completely removed the sprinklers. The mist is generated on a completely flat surface, so there is nothing to clog or break. We believe this simple solution will allow us to take aeroponics to a much larger scale,” says Langley.
LettUs Grow produces growing systems that fit in a shipping container. These containers are mobile and can be placed anywhere there is space.
Farming fish and plants together
Although hydroponics and aeroponics are two important techniques in vertical farming, they are not the only ones. Other techniques are also used. In Europe, several companies use the aquaponic breeding method. Similar to hydroponics, aquaponic plants are grown with their roots in water. Only those roots hang in a tank where fish also swim. These fish produce very nutritious waste products that the plants can use again.
The plants absorb the nutrients and thus also clean the water for the fish. According to Marcelis, aquaponics will only make up a small part of the vertical farming market in the future. “The great thing is that you use waste from the fish as food for the plants. But be careful and make sure you keep the plant system optimal,” he says of the technique.
New types of vegetables
Both Nordic Harvest and LettUs Grow first started experimenting with growing leafy greens before switching to herbs and microgreens. Then follow tomatoes and strawberries. According to Langley, multiple vertical farms follow the same stages of development. For good reasons. They are delicate, high-value crops that are widely used and can cover production costs. They also grow quickly and are small in size meaning many plants can be grown at once.
As production scales up, it becomes possible to grow a wider variety of crops. Marcelis thinks that in a few years we may be able to buy new varieties that have been specially developed for vertical cultivation. But developing new crop recipes is no sinecure. It takes 5-10 years to grow a new type of plant that is suitable for this method of cultivation.
An ideal plant is small with a short root system, grows quickly, is easy to harvest and has a high yield. In addition to the growth qualities, the ‘plant recipe’ must also be carefully composed. “The biggest challenge is keeping track of every variable that affects the plant. You need the right nutrients and you have to make sure that the plant has continuous access to the nutrients during growth,” says Riemann.
But while any crop can theoretically be grown vertically, this won’t happen in the foreseeable future. Bulk crops such as wheat and maize can be grown much more cheaply using regular methods. “I think vertical farming is currently particularly suitable for fresh produce. Technically, we can grow any crop, including wheat. But vertical farming is also relatively expensive. I think growing that kind of bulk product with a relatively low value is not realistic at the moment. Even now wheat prices are rising because of the war in Ukraine,” says Marcelis.
Still, in places like Singapore and countries like the United Arab Emirates, where about 90 percent of all food is imported, growing low-value bulk products in this way can pay off. In Europe, on the other hand, growing wheat vertically may be an option in the long term, but certainly not in the next five years.
High energy consumption
Although the future looks bright for vertical farming, there is one big problem. It requires a lot of energy and is therefore very expensive. Exact energy consumption varies from farm to farm, from system to system and depends on location, season and crop. For example, a company in Greece uses 2.87 kWh of energy in winter to produce one kilogram of lettuce, but only 1.73 kWh in summer. The Finnish iFarm calculated that growing their lettuce for 90 days costs 62.26 kWh per m2. For strawberries, that is 117.10 kWh per m2.
The additional energy consumption compared to regular methods is between 14 and 251 percent, depending on where the greenhouse and the vertical farm are located.
Wageningen University & Research and Delft University of Technology conducted a study in which they compared greenhouses and vertical farms, referred to in the study as plant factories. This concerned greenhouses and vertical farms located in the Netherlands, the United Arab Emirates and Sweden respectively. For the latter country, both greenhouses with and without artificial light were included in the comparison.
“The production of one kilogram of dry weight lettuce requires an input of 247 kWhe in a plant factory, compared to 70, 111, 182 and 211 kWhe in greenhouses in the Netherlands, the United Arab Emirates and Sweden respectively (with and without additional artificial lighting),” says the scientists in the study.
In harsh climates, the difference in energy consumption between the two growing methods decreases. Vertical farms may be the most energy-efficient choice in some extreme climates. But even in the arctic north of Sweden and in the desert conditions of the UAE, greenhouses may still be the most cost-effective way to grow.
Vertical farms can overcome the problem of high electricity consumption to some extent by optimizing production. By optimally adjusting the LED lighting and the color, you can influence both the growing time and the crop quality. Farm production costs can also be reduced as the farm becomes more automated. Robots that work 24/7 to apply nutrients at the right time, monitor growth yield and harvest when the plant is mature can be an expensive initial investment.
But over time, the robots make up for the costs through their continuous work. Despite the high demand for energy and the currently limited range of crops that are cheap enough to grow, vertical farming is gaining popularity. Although it will take a while before you also get your strawberries from the cultivation container in your area.
A source: https://innovationorigins.com