Duurzame doeners #10 Brothers Vahl

Water from 1,800 meters deep
Quality, the environment, and sustainability are key priorities for the nursery. Pests, for example, are controlled using natural methods. As early as 2008, the idea emerged to heat the greenhouses with geothermal energy instead of natural gas. André Vahl: “Together with Voorhof Nursery, we took the initiative for the geothermal energy source through the Greenhouse Geo Power Koekoekspolder project. In the spring of 2011, the physical work for this unique geothermal drilling began. On March 30, 2012, the geothermal source was officially opened. The concept of geothermal energy is simple: from a depth of 1,800 meters, water of over 70 degrees Celsius is pumped up from a hot water reservoir beneath the company. This highly saline water transfers its heat via heat exchangers to fresh water. The warm fresh water then flows into a buffer tank with a capacity of 2 million liters — which allows quick response to heating demands in the greenhouses. Finally, the fresh water circulates through a system throughout the greenhouse. Once it has cooled down, the water is pumped back down to the same depth. The system reduces natural gas consumption by 90%, and CO₂ emissions have also decreased significantly. Moreover, the system not only heats the Vahl greenhouses but also several neighboring greenhouses and homes.”

Growing cucumbers is top-level sport
Growing cucumbers in greenhouses is top-level sport. It’s essential that the plants grow in an optimal climate — the right temperature, not too humid or too dry, enough sunlight, and proper ventilation. Sufficient water and nutrients are also key. Without these conditions, the plants can't produce well. André Vahl: “That’s why we use a modern ventilation system. It allows us to remove moisture in a controlled way without directly affecting the temperature in the greenhouse. This system also helps cool the geothermal energy source. In addition, energy screens help retain heat in the greenhouse.”

Still not profitable
For every kWh of electricity, Gebroeders Vahl extracts 17 kWh of heat. However, geothermal heating is often still more expensive than using a gas-powered Combined Heat and Power (CHP) system, which many other greenhouses use. A CHP system burns gas to generate both heat and electricity. André Vahl: “We still have to buy electricity to pump up the water and power the greenhouse lighting.

Other growers can earn money by selling electricity back to the grid when prices are high. That’s unfortunate. In my view, the government does not provide sufficient direction to truly support the sustainability transition in agriculture.”

Caring for employees
The nursery employs twenty-three full-time staff and a number of part-time workers. During weekends and holidays, many students work there as well. “In the high season, we also employ Polish and Bulgarian workers,” says Vahl. “Employee well-being is our top priority. Most heavy labor has been automated or robotized. Automation is essential to address the growing labor shortage. For example, we recently invested in a fully automated packaging machine. As a result, staff no longer have to do as much heavy lifting and can instead be placed in roles where they add more value. We’re also always looking for ways to make work as pleasant as possible. For instance, we provide housing for several employees at the nursery and only work with certified employment agencies when necessary.”