TETRAS Project Pilot Studies There are four pilot studies within the TETRAS project, investigating different topics around the operation and management of RAS. We spoke to representatives of two pilot activities in Denmark, Mette Jørgensen and Annette Løttrup-Moore, about the project's work and how it will support the transition towards a circular blue economy. EUR: What is your role in the TETRAS project?
EUR: What is the current status of the pilot?
Annette Løttrup-Moore: I am business development manager at Business LollandFalster, a business support organisation, one of the partners in the project. We are working to bring a very large, land-based fish production facility to our local region, which will produce around 5,000 tonnes of fish a year. In the pilot study we are looking at how to treat water from the facility to avoid discharging large amounts of nitrogen into the Baltic Sea. Saltwater will be extracted from the ocean for use in the facility. Instead of then discharging it straight back into the ocean, we want to treat it so that it can be used for industrial purposes. How can we treat this water and use it for something else? What can we do with the residue filtered out of the wastewater?
AM: We've got the result from our pilot tests, and an expert is currently writing up a report. We've shown that we can clean wastewater to drinking water quality levels, at a competitive price. One of our recommendations is to conduct further research into the feed supply – where does the feed come from? What goes in it? We also recommend looking into the treatment of residue from the cleaning of the water. That is the big issue, how can we separate the residue? And what can we do with it?
EUR: What kind of water quality levels are you looking to achieve? AM: We have been looking at cleaning the wastewater to the same quality as drinking water. If we can achieve this, we can then look to re-use the water in industry, for example in power-to-x, or for cooling water, rather than relying on limited groundwater resources. Water recovered from saltwater RAS can be re-used by many different industries.
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Raising awareness EUR: What is your role in the TETRAS project? Mette Jørgensen: Guldborgsund Municipality works on pilot 4,which is about raising awareness about RAS and new value chains. We are demonstrating a mini version of a commercial RAS to produce ca. 1-2 tons of African catfish (Clarias gariepinus). Delicious recipes using Clarias have been developed by CELF Food, a local vocational school for cooks and nutritional experts. The students served almost 4,000 tastings at the Danish National Food Summit in May 2025, introducing Clarias, a fish that is currently not farmed in Denmark. The potential of the fish was highlighted and debated at the summit.
EUR: If you produce a fish using RAS, I guess you need to make sure there's a market for it? MJ: Very much so. That is why it is important to expose young people and future consumers to RAS and Clarias and generate interest. We also need a skilled labour force to build and maintain RAS, which is a big issue in the aquaculture sector. EUR: Are you looking to provide training to try and grow the workforce? MJ: At the moment we're still at a relatively early stage, so we're focused more on supporting interest in RAS via (bio) technology and biology at gymnasium and vocational school level, which is relevant across many different subjects. At the gymnasium lab they can test the RAS water for nutrients, and measure water chemistry parameters important for the welfare of the fish. They can reuse nutrients to grow plants. Equally importantly, electricians and mechanics can experience at an early stage of their career how their expertise can be crucial to PLC-programming, or how to perform a quick repair if a pump sets out or a filter is blocked. For all activities, including creating interest for RAS among farmers, we find that having a physical, commercially relatable pilot plant makes a big difference. It makes the potential tangible and concrete.
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