Shrimp and tropical fish, raised in the far north of Sweden – warmed by the waste heat of a power plant that would otherwise release that energy, unused, into the surroundings. What sounds at first like a contradiction is becoming a research project in the northern Swedish city of Umeå. A team at Umeå University is building a closed, land-based fish farm designed to move resources in a loop rather than consume them.
The backdrop is a familiar environmental problem. Overfishing strains marine ecosystems, lost fishing gear accounts for a significant share of the plastic in the ocean, and effluent from open farms can trigger algal blooms. Land-based systems in closed tanks sidestep many of these risks – provided they are built cleverly. That is exactly where the project comes in.
At its heart lies the principle of multi-trophic farming: several species at different levels of the food chain live together, so that the waste of one becomes the food source of the next. Water flows through a succession of tanks; at each stage, microorganisms convert the residues into fresh nutrients – an optimised ecosystem in miniature. The research is led by Olivier Keech of the Umeå Plant Science Centre, who first tested the approach around a decade ago.
Why it matters
The decisive trick is the heat. The facility is to be run on surplus heat from Umeå's combined heat and power plant, drawn off as both air and liquid and fed in through the district-heating network. Because room temperature comes close to a tropical climate, the system can support species such as tilapia and shrimp that would otherwise have to be imported from Southeast Asia or Latin America. Local production removes the long transport routes – and the reused waste heat cuts the energy cost of warming the water still further.
The project is funded through the EU research programme Horizon Europe and run by Umeå University together with the city of Umeå, the energy utility Umeå Energi and the research institute RISE. A digital twin is planned to optimise the heat and water flows. Small-scale trials are due in the spring, and within a year they are meant to grow into a larger pilot plant. If the concept proves out, an entire region could one day supply itself with fish and shrimp – far more climate-friendly than today.