The interest in growing plants indoors in vertical farms keeps increasing. But many investors who thought they could simply buy an empty warehouse, plug in some grow lights and turn out perfect heads of lettuce to make money have been disappointed. Here are a few key lessons learned from city farming expert Roel Janssen on successful vertical farm projects.

The most crucial part when starting an indoor farm is to have a grower that understands how to grow plants indoors. New (sensor) technologies and the internet of things offer great opportunities for indoor farming, but if you don’t have a grower you will not get out the most of your operation. You can have great packaging and attractive marketing tools, but the product itself will determine your success. That being said; these are some of the most important factors that can determine the success or failure of your vertical farm investment:

When we look at how to get the highest return on an investment for a vertical farm, we focus a lot of attention on creating a facility that allows you to produce the highest yield of crops (measured in grams) using the most ideal amount of light (measured in moles or mol). That’s because your LED grow lights are amongst the highest expenses in terms of the city farming infrastructure and operation. Keeping that in mind, here are a few of our most valuable tips for increasing your grams per mol. The information is gathered from research done at the Philips GrowWise Center as well as commercial projects ranging from US, Japan to Europe.

One aspect that many new vertical farm growers overlook when they are creating an indoor farming environment is maintaining the best climate conditions. If we assume 50% of the electrical input power is converted into light, the remaining 50% is converted directly into heat. A proper airflow can remove this direct heat, but also the light that will be absorbed by the crop will indirectly be converted into heat. Typically the crop evaporates water into the air to get rid of this heat, therefore this process will result in a higher humidity of the air. To keep increasing humidity and temperature under control, you must start with a good ventilation and air handling system in your vertical farm. Not installing a proper climate control and air handling system will decrease your yields, resulting in additional costs and hassle after installation to fix inefficiencies. 

Once you have a good climate, how can you get the highest yields from it? We have done hundreds of research projects on growing plants indoor focusing on yield and the most optimal light intensity for a certain crop or variety. Yield however is not always the most crucial and single most important part. Let’s take red oak lettuce as an example. When this lettuce is grown outside in a field, it turns red because it is stressed by the sun or large temperature changes and it typically yields less compared to its’ green version. When the same variety is grown indoors, it remains mostly green because there is no UV light, but it does develop fast and shows comparable or sometimes even better growth than a green version. At Philips lighting’s GrowWise Center, we have four full-time plant specialists who develop so-called light and growth recipes for specific crops. Based on their research, we developed a coloration light recipe for red oak lettuce that turns a mostly green head of red oak lettuce into a dark red lettuce in just three days. Growers can grow a large head of lettuce in their regular growth cycle, apply this light recipe as a pre-harvest treatment, and get a great quality crop with much higher yields and the proper appearance. Together with breeding companies we screen and help them develop varieties that could support growers to help them differentiate even more based on taste, quality or color.