As part of the DBU project “Climate-friendly offshore production of algal biomass” at the Universities of Rostock and Kiel and GEOMAR Kiel, a test facility in Eckernförde Bay is using various raft structures to investigate whether and how bladderwrack (Fucus vesiculosus) can be grown on the foundations of offshore wind turbines. From the perspective of marine nature conservation, these foundations represent ecologically problematic structures, but are necessary for sustainable energy production. The project aims to achieve dual use of offshore wind turbines already built in the Baltic Sea. If successful, the water quality can be improved because the bladderwrack removes nutrients from the Baltic Sea as it grows. After harvesting, it will be used in agriculture via a value chain for cosmetic raw materials and biogas as well as the digestate as a mineral-rich fertilizer substitute.