Surveys and market research studies have found that an increasing number of consumers are seeking out sustainable and environmentally friendly food options. Some of the key factors driving this trend include concerns about the health and environmental impacts of conventional agriculture, a desire for transparency in the food production process, and a growing awareness of the role that consumers can play in promoting sustainable agricultural practices. Fruits and vegetables are one of the top categories in which consumers base their purchasing decisions on sustainability [1].
An obvious question here is often whether fruits and vegetables grown locally in the greenhouse are more sustainable than those flown in or driven from Spain or Morocco. The answer, as so often, is: it depends.
Greenhouse produce can be sustainable depending on different factors. Sustainable greenhouses aim to reduce waste, conserve resources, and maintain soil health through practices such as integrated pest management, water recycling, and using renewable energy sources. A greenhouse for tomatoes that uses oil for heating would have to burn 1 liter per square meter, depending on the area of cultivation. If we consider the area covered by greenhouses, this number quickly grows to a very large amount, resulting in a high emission of carbon dioxide. With renewable energy sources, this amount can be drastically reduced.
This month, we take a look at this topic and talk with two growers that use renewable energy sources in their greenhouses:
Wittenberg Gemüse
"Especially in our own shop and in contact with customers, we notice the high demand for regional and sustainable products," says Kevin van Ijperen, authorized officer at Wittenberg Gemüse. The company has a total of around 40 hectares of greenhouses in Germany, where tomatoes, peppers, cucumbers, and strawberries are grown.
In 2009, the company from the Netherlands found a perfect location in Saxony-Anhalt - because a neighboring nitrogen plant allows fruit and vegetables to be grown in a CO2-neutral manner. This is made possible by the waste heat of the chemical processes which, for Wittenberg Gemüse, are a welcome heating option for their greenhouses.
"We need heating for our cultivation, and through this cooperation we manage to still produce sustainably,"
van Ijperen continues. Previously, the warm water was cooled down in the nitrogen plant and then discharged into the Elbe River, but now it flows through the greenhouses. CO2, which is a waste product from the nitrogen plant, is also used at Wittenberg Gemüse. "We mix it with the air to create a higher CO2 concentration in the air. This gives the plants optimal growing conditions." It is a common practice to use CO2 for better plant growth in the greenhouse – using the gas that already exists saves costs every day – and is more climate-friendly.
Their goal?
"In the long term, our goal is definitely to be able to operate self-sufficiently. Therefore, in addition to district heating, we also work with rainwater storage, among other things." The aim to be self-sufficient thus does not only concentrate on energy, but also water and all resources available. They are also a great opportunity to be more environmentally-friendly – because water is also a limited and endangered resource.
Gemüsebau Steiner
More than 500 kilometers further south and still in Germany are the greenhouses of Gemüsebau Steiner. They too have found a sustainable solution for heating their 26 hectares of greenhouses: Geothermal energy. A borehole close to their site allows them to fully work without fossil fuels for heating. Alongside this, they use photovoltaics to produce most of their electricity, as well as rainwater storage for irrigation.
"Geothermal energy makes us independent from fossil fuels," says Christian Reichtalhammer, operations manager at Gemüsebau Steiner. “This gives us freedom, especially in times of unsure and rising gas prices”. They began using renewable resources for their crops in 2014. "We have not yet achieved complete self-sufficiency, because when it is dark, we currently still need electricity from external sources," Reichtalhammer continues. Since last year, Steiner also publishes a sustainability report on how their fruits and vegetables are grown sustainably. Here, consumers and interested people can see how their roughly 10.000 tons of produce perform in terms of environmental aspects like energy, heat or water usage.
And what's the point? "During our regular tours of the farm, we notice that there is a lot of consumer interest in cultivation and sustainability." Regionality also convinces many customers. It is one of the crucial aspects of greenhouses – they allow the cultivation of plants that need heating to grow in different climates – with the mentioned methods, even in a sustainable way.
In addition to these practical applications, research is also being carried out on sustainability in the greenhouse: for example, in a project in the Netherlands called "Greenhouse 2030". Here, methods are being researched for Wageningen University to reduce CO2 emissions, integrate renewable energies, grow without pesticides, and not discharge chemicals into the environment. Green electricity is also used for heating here, and by optimizing the cultivation process, even avocados and vanilla can be grown. One of the drivers for this research and changing process is the decision of the Dutch government to have all greenhouses climate-neutral by 2040.
The question as to whether products from the greenhouse can be sustainable in terms of heating can therefore be answered with an unequivocal yes - if the company strives to act sustainably. Renewable energies and partnerships, as in the case of Wittenberg, mean that sustainability and greenhouses are not mutually exclusive.