Postcards from Switzerland
During a visit to Switzerland, I visited The Tropical Greenhouse Project in Ruswil. This was a pilot project that demonstrated how tropical food production can be established in a temperate climate by using industrial waste resources.
The project was based on a simple yet strategically strong idea: transforming stable industrial waste heat into value-creating, local food production with high resource efficiency and low environmental impact.
The facility utilized waste heat from a gas compressor station, which, via a closed heat-exchanger system, provided both heating for the greenhouse and temperature control for process water used in aquaculture. This enabled year-round operation under tropical climate conditions without the need for conventional fossil energy sources, significantly reducing energy costs compared to traditional greenhouse solutions.
Photo: Knut Werner Lindeberg Alsén (2024)
Photo: Knut Werner Lindeberg Alsén (2024)
Interaction between plant production and aquaculture
The production system was based on an integrated interaction between plant production and aquaculture. Tropical fruits such as bananas, papayas, and guavas were grown in polyculture, while fish—primarily tilapia—were farmed within the same system. Water and nutrient cycles were largely closed: rainwater was collected from roof surfaces and used in the facility, nutrient-rich fish water was applied for plant irrigation, and fish feed constituted the main external nutrient input. In this way, waste streams were converted into productive resources.
The project documented that this type of system can operate with technical stability even in an alpine climate, and that the combination of waste heat utilization, circular water use, and integrated production results in high resource efficiency per square meter. The experiences gained in Ruswil formed the basis for further development and commercialization of the concept, including the Tropenhaus Wolhusen.
Tropenhaus Wolhusen was a large, innovative tropical greenhouse and aquaculture facility in Wolhusen, developed as a continuation and commercialization of the Ruswil pilot project. The facility used waste heat from a gas compressor station to create and maintain a tropical climate in an alpine environment, demonstrating how industrial waste energy can be converted into food production, employment, and public experiences.
The production area consisted of a greenhouse of approximately 5,300 m², where tropical fruits such as bananas, papayas, and guavas were cultivated, combined with aquaculture in which warm-water fish were farmed. The system was built around circular principles: rainwater was collected from roof surfaces, nutrient-rich fish water was used for plant irrigation, and waste heat provided both air and water temperature control. The objective was high resource efficiency, low energy costs, and reduced environmental impact.
In addition to food production, Tropenhaus Wolhusen had a strong experiential and educational profile, featuring a publicly accessible tropical garden, restaurant, and visitor center. This made the facility both an agricultural, energy, and tourism project.
The facility opened around 2010 and later had Coop Switzerland as its main shareholder. Despite technical success and significant attention, the project struggled with economic sustainability. The company behind the facility was dissolved in 2017, commercial operations ceased in 2019, and after several attempts at alternative use, the facility was permanently closed in 2024.
Today, Tropenhaus Wolhusen is regarded as an iconic demonstration project for waste-heat-based, circular food production. It showed that the concept is technically feasible in cold climates, but also that economic sustainability, scale, market integration, and operating models are decisive for long-term success in such complex hybrid projects.