How can we continue to produce food while making smarter use of energy, water, nutrients and scarce space? In Greenhouse in Transition, researchers from the Netherlands and the United States are exploring more sustainable greenhouse designs, more efficient growing systems and ways to connect greenhouses with their surroundings, for example by exchanging water and waste heat with farms and industrial sites.
Cameras and sensors, automated climate control and energy-efficient lighting: many Dutch greenhouses are equipped with high-tech systems. These help growers optimise plant growth while reducing energy use and costs. But more is needed to make greenhouse horticulture fit for the future, says Leo Marcelis, Professor of Horticulture and Product Physiology. Greenhouse in Transition, a project led by Wageningen University & Research (WUR), therefore takes a broad approach.
"In addition to energy, the project also looks at aspects such as water and nutrients," says Marcelis. "There are still many opportunities to make greenhouse horticulture more sustainable, for example by reusing waste streams wherever possible. Sustainability also has a social dimension. Working conditions are not equally good everywhere. Our expertise can help improve them, for example by investigating where technology could take over physically demanding or complex tasks."
New greenhouse and growing systems
The researchers are not only looking at ways to improve existing systems. They are also designing entirely new types of greenhouses and growing systems. Marcelis: "Some crops could perhaps be grown differently, such as tomatoes. During the early stages, young tomato plants could be grown in a vertical farm, when they still need relatively little light. They would only be transferred to a greenhouse after this initial growing phase, where they would continue growing until they produce fruit. This approach could make it possible to do several harvests a year. I am very curious to see what we come up with when we go all the way back to the drawing board. Would we make completely different choices?"
Interaction between the greenhouse and its surroundings
Another part of the project focuses on interaction with the surrounding area. According to Marcelis, a greenhouse or greenhouse complex could be connected to nearby residential areas, farms and industrial sites. "This could involve exchanging energy, water and heat. This exchange can work in both directions. Industrial sites, for example, produce waste heat that could be used to heat greenhouses. Treated industrial effluent or water from wastewater treatment plants could also be useful. At the same time, greenhouses themselves produce excess heat that they need to release. This could be used to heat homes. Residual water or surplus stored rainwater could in turn be useful for agriculture. Connections like these could deliver substantial sustainability benefits."
Such interaction does come with certain conditions, Marcelis emphasises. "First of all, everything should be located as close together as possible. The greater the distance, the more energy and money are required, reducing both efficiency and sustainability. Safety is also an important consideration. You need to be absolutely certain that these waste streams are clean enough to reuse. Treated wastewater, for example, may still contain traces of pharmaceuticals. These may not affect plant growth, but it would be a problem if they ended up in food products."
Collaboration with the United States
Greenhouse in Transition brings together universities, companies and research organisations from the Netherlands and the United States. According to Marcelis, the project provides a valuable opportunity to share knowledge about technology and biological control with the US, where greenhouse horticulture is less advanced in many parts of the country. "At the same time, we can also learn from them. Some things may be better suited to low-tech rather than high-tech solutions. We will examine that critically. We can also learn from the way the US deals with extreme weather conditions, which we will face more often in the Netherlands as well."
Practical application
The aim of the project is not so much to produce a blueprint for the greenhouse of the future, but rather to develop concepts showing what such a greenhouse could look like, Marcelis explains. "Growers can select elements from these concepts and apply them to their own businesses. The project will also help them do this, for example through demonstrations. We are looking at the whole process, from design through to practical application. Some solutions could be introduced in the short term, while others are intended for the more distant future."
