Vertical farming is the practice of growing plants in vertically stacked layers in a building. This makes it possible to grow vegetables close to consumers, such as next to a supermarket. Since the conditions in a vertical farm are fully controlled, crops can also grow in extreme environments like deserts or cold, dark areas. However, before vertical farming can be implemented on a large scale, several challenges need to be resolved, such as high energy consumption. Smarter use of artificial light can make significant savings, according to research conducted by Wageningen University & Research. And plant health improves too.
In a vertical farm, every detail of the growing conditions can be controlled. This is important for high yield, good quality and efficient use of resources such as water and plant nutrition. Creating optimal conditions for crops requires high levels of energy consumption. Moreover, constant environmental conditions are also a feature in many vertical growing systems. For instance, the lamps required for plant growth give the same amount of light every day, and the thermostat always remains at the same setting. The researchers concluded that this is often unnecessary. "Adopting a more dynamic approach can significantly reduce energy costs while plant development remains the same or even improves," says Leo Marcelis from Wageningen University & Research.
Variable 'lighting plan'
According to the researchers, lighting plays a key role: plants need light for photosynthesis, and different light wavelengths, which we perceive as colours, affect plant growth in various ways. "Because plants do not always need the same light for optimal development, dynamic environmental control provides a better response to the specific needs of plants at different times. That results in better plant growth and quality," says Marcelis. It also enables a smart response to fluctuations in energy prices by using more electricity when tariffs are low, thus saving costs. Dynamic environmental control enhances the efficiency of vertical farming, increasing the likelihood that this cultivation method will become a viable alternative to greenhouse farming in the future.
Developing the model
The researchers developed a model using knowledge of plant physiology, combined with new sensors, and modelling techniques. In addition, plant species grown specifically for vertical farming were used. The computer model was designed to keep plant photosynthesis constant throughout the day while at the same time minimising electricity costs. Just by varying light intensity within a day, it is possible to reduce costs by 12%, the research shows.
The researchers also studied the influence of variable light intensity on the growth of leafy vegetables like spinach, which are often grown in vertical cultivation systems. They found no negative effects, even when the plants were exposed to irregularly varying light intensity instead of a fixed pattern.
Opportunities for greenhouse horticulture
Growing factors such as light intensity and temperature can also be dynamically controlled in traditional greenhouses, where sustainable energy sources such as solar and wind energy are increasingly being used. The erratic availability of these energy sources causes large fluctuations in the supply and price of electricity. Both greenhouses and vertical cultivation systems can benefit by responding to these fluctuations.
Developing new cultivars
New cultivars developed specifically for vertical growing systems can help make vertical farming more profitable. These cultivars can be specifically tailored to the conditions in controlled environments. Furthermore, this offers the opportunity, more so than with existing cultivars , to focus on improvements in flavour and nutritional value rather than on firmness and shelf life, which has often been the focus until now.
Before vertical farming can fully contribute to food production, other key obstacles must also be addressed, say the researchers. Many of the proposed solutions have not yet been widely tested, for example. Moreover, farmers using vertical growing systems need good sensors and models to optimally control environmental factors. "If we dynamically control environmental factors in vertical farms, we can reduce both energy consumption and costs. In turn, that will increase the profitability and sustainability of these farms," Marcelis concludes.
