Vertical farming or city farming – the growth of plants indoors stacked in vertical layers – fully depends on the artificial lighting instead of sunlight. Philips Lighting started working on light products for indoor farming in 2010 together with HAS university and eventually created Philips GrowWise – the research centre in Eindhoven that finds optimal LED-light recipes for indoor farming and develops custom-built vertical farms projects.


Global Director City Farming in Signify, Roel Janssen, says that vertical farming has three main benefits. The first advantage of city farming is a higher yield of produce from a square meter of the floor space due to the use of multiple layers – this is very useful in the densely populated areas like Mumbai, Tokyo or Singapore, where a square meter of land is quite expensive. “On one square meter, a vertical farm can produce much more than you would have in a normal field. For example, for growing around 20 kg of lettuce on 1 m2 in California farmers use 200 litres of water per kilogram but in GrowWise facility, we harvest 100 kg from 1 m2 with less than 2 l of water per kilogram.” So vertical farming helps to increase the yield per square meter of actual floor space.

One more merit of a vertical farm is the quality of produce, and Roel Janssen emphasises that quality is the main advantage of city farming: “The quality greatly depends on operating the indoor farm in a right way: if you make sure that the hygiene is up to the proper standards, if you automate most of your production and keep close control over the facility, you can improve the nutritional value of the crops.” Researchers of GrowWise have found light recipes to increase vitamin C content in mint and rocket, and to increase the content of volatiles (aromatic components) in basil. The strawberries that are grown in the controlled environment of GrowWise have a higher Brix value – they are sweeter than strawberries from the open field.

Nowadays lettuce is the most popular crop that is grown in vertical farms, and its quality can be improved. Janssen says: “If you have a bagged salad, often there are red varieties in there, such as lollo rosso. This lettuce is red because of the response to the ultraviolet in the spectrum of the sun. Since we grow the red variety without UV, our ‘red’ lettuce stays mostly green. Three days before the harvest we have a specific pre-harvest light recipe that triggers the colouration of the lettuce. We use a different combination of red and blue and change the daylength, which intensifies the production of anthocyanins (important antioxidants) and makes the lettuce red again after only three days of treatment. This is how we can grow the lettuce in the most optimal way, have a high yield and increased nutritional value. When the lettuce is grown outside, the accumulation of anthocyanins is gradual, and the growth is slower.”

Janssen says that the reliability of the growing process belongs to the benefits of indoor farming as well: “If you do everything properly and get no foreign bodies in your produce, you will always have a constant quality and you can have the same produce all year round.” The reliability of farming indoors also means that the growers can be flexible on the market – they can regulate the growth of produce in accordance with the demands of the customers.


Climate, says Janssen, is the most important tool of indoor farming: most of the water captured by the plant is evaporated, the air becomes humid and it is necessary to remove it from the room. “Light, temperature and CO2 are the main drivers of production and yield. For us in GrowWise the main drivers are, obviously, light and light recipes,” says Janssen. Irrigation and fertigation in the water can influence the growth but also can influence nutrient uptake: “If you want to have low-potassium lettuce, at the end of the growth cycle you can stop adding potassium to the water.”

Seed variety is also an instrument of ‘tweaking’ the crops. “The main goal of the seed breeders is to develop varieties that can resist the environment: breeders want to develop crops that can resist bugs, diseases and temperature shifts. For an indoor farmer, the weather is not crucial – it is always springtime in our climate cells, and the temperature is constant. If we do everything with proper hygiene, there are no diseases. Breeders have already developed seed varieties for indoors: for greenhouses and hydroponic systems. The next step would be to develop specific varieties for the vertical farming – to breed and select for the yield, quality or reliability.”

Currently, GrowWise selects from the available seed varieties together with the breeders. “We work with six-seven breeders to make a selection of the best varieties of crops for indoor farming: we carry out the selection trials to see how the plants perform in the environment without daylight. Maybe we can find varieties that meet our needs and are interesting for us – then the breeders will scale up production. Testing the varieties of crops with us helps the breeders because we will give advice to our customers: we know for sure that this variety works well and gives big yields.”

By far the most cultivated crops in GrowWise facilities are lettuce and basil. “We have tried over 200-300 varieties of lettuce here,” says Roel Janssen. “Our main focus is on leafy greens because all the energy that you put into those plants is paid back when you sell the produce. If you grow, for example, strawberries, you first need to grow the plant for about two months before it starts fruiting.”

On the racks of the climate cells in GrowWise there are also various baby leaves – 6-10 cm high – red sorrel, mustard leaf, mint, rocket. “We have grown strawberries, cucumbers, kohlrabi, broccoli, even melons – all sorts of crops. It was purely experimental – to see what the possibilities are. However, not all of the crops have commercial viability at his point. The ones that we think are the closest to be economically viable are all the leafy greens, then fruits.” GrowWise is planning to start growing raspberries soon. One of the cells is being re-equipped for the high-wire crops: tomatoes, cucumbers, peppers.

“In about two months we will grow tomatoes here, on the third floor of a building,” says Janssen.


Why do vertical farming startups fail? Roel Janssen says that the outcomes greatly depend on the mindset of a company toward innovation. “In the Netherlands, we have a very open way of innovating, especially in the horticultural industry, so cooperation, communication and transfer of knowledge are the basis of the business. But in the USA, for example, people who set up a vertical farm often plan to create intellectual property, patents and a unique design system all by themselves – so, basically, they try to reinvent the wheel and that makes the whole thing difficult. So, they do a lot of things by themselves and eventually they come to the strategy of open innovation and try to find the best partners in different segments, but it takes time. Most of such companies eventually come to us – when they visit us, look at automation, light, and climate control, they typically end up being our partners as well.” “Philips GrowWise obviously supplies the light solutions for indoor farming but also the knowledge on growing crops in a vertical farm and the knowledge on the design of the indoor farming facilities. We have a global partnership program that includes 40 technical parties – they do the full engineering and implementation of the ideas that we develop with the customers.”

Another reason why indoor farms are not feasible is that some vertical farming startups keep their capex as low as possible in the very beginning of their work: “There are vertical farming startups that install indoor farm racks in a warehouse and then stop caring about hygiene factors, climate and scalability. Lots of them produce some crops, come to the market early without knowing how to scale, they are not consistent in supply and they don’t have a good distribution channel – that is why they fail,” says Janssen. “In order to succeed, startups should be able to sell the added value of a vertical farm – the higher nutritional value of the produce, which is also always clean and has a longer shelf life. If the companies don’t have a reproducible, scalable business model and operational mode, they don’t sell that added value, hence fail – that is what is seen in lots of cases, especially in the USA. If someone puts some containers to grow leafy greens then delivers them on a bike around the city and supply some produce to the market, this is not really scalable and financially feasible.”

Janssen admits that a certain level of professionalism in indoor farming needs to be built, but there is no standard yet – and this is the biggest challenge for the industry. “If you look at the example of greenhouses, there is a standard for all of the constructions of that type – it’s a Dutch Venlo greenhouse. Almost all over the world, you can see greenhouses that are very comparable to it in size and dimensions, so all of the technology is built for those dimensions. Here, in our vertical farming facility, we have done research on at least 20 different substrates and at least on 5 different growing systems, but there is no one winning model yet. People are still developing a standard for vertical farming. And we try to develop it in a very open way – together with our customers in order to be successful.”


Roel Janssen says: “If a crop is not in the greenhouse at this point we don’t expect it to be in a vertical farm very soon, because first it is much more convenient to grow something in a greenhouse – you can build greenhouses around the city and then transport the produce.”

According to Janssen, most of the food shortage issues nowadays are caused by the logistics problems – grains, potatoes are relatively easy to transport, they are just not always transported to the right regions due to the economic and political reasons. What can be achieved with indoor farming is the possibility of supplying more nutritious local food – and that is what is already being done. Greenhouses can be gradually transformed to produce more nutritious crops than they do to feed the regions with food quality problems. Janssen concludes: “I don’t think indoor farming is the solution to this world’s food shortage problem. Greenhouses combined with indoor farming cannot prevent the global food crisis, but they can play a role in improving the situation.”

Vertical farming also has the potential for the production of functional food: if one has kidney problems and would like to eat lettuce with less potassium, it makes sense to produce this lettuce in an indoor farm. It is more difficult to grow low-potassium lettuce in a greenhouse or in an open field because there the growers have to rely on sunlight, which influences the nutritional content in an uncontrolled way. Indoor farming can also develop its potential for the cultivation of pharmaceutical crops – to influence their nutritional content in a controlled way.


The process of creating an indoor farm for GrowWise begins like that: customers look through business cases based on ten years’ experience to have a better understanding of what might meet their requirements. Then the research centre with its partners prepares a model, which helps the customers to assume a cost per kilogram of produce: “We take the growing results that we have achieved in all the project done in GrowWise and in Brightbox (vertical farming expertise centre at the Brightlands Campus Greenport Venlo) and also done for our customers to come up with the yield prediction, which is based on a facility of a certain dimensions. We assume certain costs of the investment, and we can come up with the price per kilo of produce. We put it into the business model and if that kind of model works for the customer, we start to discuss the system architecture. We involve our partners who do the detailed engineering: automation, sowing lines, transplanting, germination, growing rooms, climate and irrigation control, CO2 control, spacing, lighting – all of that is considered. Our partners also implement engineering for customers. Typically, the process of creating a vertical farm from the beginning to the implementation takes at least a year. The construction lasts roughly six months and during this time we repeatedly grow the leafy greens to validate the results, so as in three months the customers can have a pretty solid, validated reproducible growth recipe. Then it is necessary to design the facility, make sure that all the partners communicate well, integrate everything, engineer that and implement it. This is how you build a large-scale automated vertical farm.”

“If someone wants to create a small scale research room such as the ones we have here, it’s fairly easy to build – but it can only be useful for a first rough estimation before doing research. If you want to make a vertical farm scalable, automation is the best way to do it.”


“In Asia vertical farms are called “plant factories” which may sound as something very artificial for us here, in Europe, but in fact it is quite a good name for an indoor farm facility, because if you run it as a factory, you make sure that everything is controlled, reproducible and scalable – that us what is important if you really want to be successful as an indoor farmer. In Asia consumers view a factory as something well controlled, hence maintaining good quality standards, that is why a “plant factory” term is appealing to the Asian customers. In Europe consumers like the term “indoor farm” more, because “a farm” sounds nicer and warmer than a factory. People prefer to imagine somebody with a beard and dirty hands growing crops because it resembles a farm. By the way, when we introduced bumblebees into our facilities to pollinate the strawberries, everybody loved it and then, all of a sudden, an indoor research facility from artificial and factory-like became nice and cosy.”