How can vertical farming contribute to (inter)national food production? This question is more complex than it initially seems. The answer does not only depend on the production, but also on the costs for water, energy and CO2. The Greenhouse Horticulture Business Unit of Wageningen University & Research and TU Delft are investigating the feasibility of this new production system.

Take a head of lettuce for example: how much does it cost to produce one? The answer is fairly well known when it comes to cultivation in greenhouses in the Netherlands. Greenhouse models and growth models can be used to predict the production at a certain consumption of water, energy and CO2. Those models are not suitable, however, for cultivation in a vertical farm. The combination of high-density crop production and a closed construction necessitates a different approach with respect to heat, cooling and dehumidification.

The key question when comparing both cultivation systems is: how much energy does a vertical farm need? The required amount of water and CO2 can be reduced compared to a 'traditional' greenhouse, but this is not the case for the cooling and dehumidification demand. The high internal heat load and the lack of natural ventilation ensure a high cooling demand, which consequently results in residual heat.

USING RESIDUAL HEAT IN THE CITY

The question is whether this residual heat could be used in the surrounding urban environment. One of the key features of vertical farming is that it can take place in the city, which would allow it to exchange energy with other users. Those other users could become customers of the residual heat from the vertical farm.

FEASIBILITY OF VERTICAL FARMS IN FIVE STEPS

WUR and TU Delft have joined forces to calculate the feasibility of vertical farms in five steps. The first step investigates how plants process energy in a closed cultivation system. The second step concerns the total energy demand: how much energy does vertical farming need? Step three focuses on optimising this energy consumption and step four on the integration of the vertical farm into the city. Ultimately, this information is used in step five to calculate the financial feasibility of (urban) vertical farming. The research project will be completed by the end of 2019.

This work was supported jointly by Staay Food Group, Westland Infra and the Top Sector Horticulture & Propagation Materials (EU-2016-01) via EFRO Fieldlab Freshteq.

Photo credit: Guy Ackermans