Vertical farming is gaining ground, but it does not save more water than Danish greenhouses

In Nordic Harvest’s farming hall in Taastrup, various types of lettuce and kale are grown on 1500 m2 with 14 “floors”, each of which is 70 centimetres high. Illustration: Nordic Harvest

Vertical farming is emerging all over the world, including Denmark. But although food production in which edible plants are grown at heights inside buildings with only artificial light may be a good idea in some parts of the world, that is not the case in Denmark.

This is the assessment of Carl-Otto Ottosen, professor at the Department of Food Science at Aarhus University who is currently working on a report on vertical farming in Denmark. Although the report will not be completed until October, he is already confident in the findings.

“We can discuss is on a global scale, but I find it difficult to see the point of vertical farming in Denmark, because it is far more energy-intensive than an ordinary greenhouse,” he says to WaterTech.

According to Carl-Otto Ottosen’s calculations, vertical farms consume as much as 30–60 percent more electricity than a commercial greenhouse, which receives sunlight all year round and artificial light during the darkest periods.

And unlike other places in the world, we have space for greenhouses and no problems with getting enough water, he explains.

Denmark has plenty of water

Denmark differs from other places in the world, among other things when it comes to water resources. Recently, the world’s largest vertical farm, the 30,000 m2 “Bustanica”, opened in Dubai. The company behind it claims to be able to produce leafy greens with 95 percent less water consumption, which is in short supply in the desert country.

Here, vertical farming can make sense, because the increased energy consumption can be offset by the fact that valuable resources such as water and land are not seized, and according to Carl-Otto Ottosen, it also makes sense in other places. For example, in Singapore, which has a population of just under 5.5 million people and an area smaller than Lolland, or in Japan, which has very little arable land and a large population willing to pay high prices for quality food.

However, it is not quite the same in Denmark, where according to Carl-Otto Ottosen, we have plenty of space for greenhouses, where water is recirculated just like in vertical farming and rainwater is often used. He therefore believes that it makes no sense to put forward arguments that vertical farming saves water in Denmark.

“You have to remember to compare apples to apples. If you compare it to an agricultural field, vertical farming uses about 10–100 times less water. But when you compare with a greenhouse, there is no difference in water consumption between the two,” he says.

Just like in vertical farming, no pesticides are used in greenhouses and no nutrients are washed away into nature, which are otherwise some of the most important arguments for vertical farming. In addition, both farming methods are used for the exact same crops, which today mainly consist of lettuce and herbs. These are plants that have never been grown in fields in this country. Therefore, it does not make sense to compare vertical farming with traditional agriculture here, Carl-Otto Ottosen says.

However, he sees a certain potential in Denmark—albeit not a very strong one. If we start growing the plants in a vertical farm, and then move them to a greenhouse with natural light when they have grown, we can make a better use of land, as well as achieve a higher quality product and less losses.

But is there no point in growing plants exclusively in vertical farms?

“I actually discussed this with a colleague the other day. We came to the conclusion that there is a certain potential for medicinal plants from which certain substances are extracted. You can control the production very carefully, which is an advantage because you get the same result every time.”

If one instead managed to grow high-value crops with a higher protein and carbohydrate content, such as beans, strawberries, and potatoes, then vertical farming could make sense according to Carl-Otto Ottosen, but he points out that it does not seem realistic—not even in the long term, because it has to also make sense in terms of energy.

“You have to look at things in a more nuanced way”

Professor Carl-Otto Ottosen’s conclusion that vertical farming has no or only a very limited potential in Denmark meets resistance from Anders Riemann, who is the founder of Nordic Harvest in Taastrup, Denmark’s largest vertical farm. Lettuce and kale are grown in a 1500 m2 area with 14 “layers”, each of which is 70 centimetres high.

“You have to look at things in a more nuanced way,” he says.

“We are amidst a climate crisis. That is why we are now developing a technology that can secure our food supply over the next decades. Denmark can become a pioneering country in this field, just as we have been in the field of wind turbines.”

Anders Riemann also questions Carl-Otto Ottosen’s assessment that there should be no difference in water consumption in vertical farming compared to greenhouses—at least when it comes to Nordic Harvest’s farming method. In addition to “reusing” the water, the company also recirculates the air and extracts the condensation (evaporation from the plants’ transpiration), so that the water is fed back into the system, he says.

He acknowledges, however, that the technologies within vertical farming are still immature, but says that Denmark can get to the forefront thanks to the many skilled engineers and a long tradition of agriculture and food production.

“We can’t start by growing potatoes and then think that we can mature the potato farming technology with a chronic deficit. We need to start with the crops where we can make a profit, such as lettuce and cabbage, and then we can start digging into some slightly more substantial vegetables that also contain protein, more fibre, and that can give the consumer a greater feeling of satiety.”

He also denies that vertical farming is a bad idea because of the energy consumption. Vertical farms use only electricity and no wholly or partly fossil-based district heating, as the greenhouses do. In addition, plant production can take place at night, which, according to him, can also help promote the green transition.

“If you are an investor in a wind farm, you will see more and more often that the electricity price becomes negative at night, because there is a large supply of wind energy and almost no demand. But we can make use of that wind, so it will be more attractive to build more wind turbines,” he says and adds that plant production at night can help balance the electricity grid.

He also rejects the claim that there is plenty of space in Denmark for greenhouses, referring to a report from the Danish Board of Technology, which concludes that “the many different activities that unfold on open land together challenge Denmark’s limited area.” Because if all the adopted plans and targets for the use of Denmark’s surface area are added together, then “it covers 130–140 percent of Denmark’s surface area.”

As vertical farming can produce more food on the same horizontal surface area compared to a greenhouse, the advantage is obvious, Anders Riemann believes.