IVL Swedish Environmental Research Institute

This prefeasibility study assesses halocline ventilation as a solution to oxygenate hypoxic and anoxic bottom waters in the Baltic Proper. The method requires pumping 10,000 m³/s of water between stratified layers, demanding 600 GWh of energy annually, at an estimated cost of €50 million. While promising for mitigating eutrophication, technical barriers, including the lack of suitable submersible pumps, remain significant.

Powered by offshore wind, the method’s carbon footprint (10 kg CO₂eq/kg separated phosphorus) is lower than alternative strategies, with ecological benefits such as improved habitats, increased fish reproduction, and reduced harmful algal blooms. However, risks like halocline disruption and sediment mobilization require thorough evaluation.

The integration of wind energy and ecological restoration highlights the need for marine spatial planning and stakeholder dialogue to balance ecological, technical, and societal considerations. Further research and pilot studies are essential to validate its feasibility and long-term impact.