European Recirculating Aquaculture Systems (RAS): Innovations, Investments, and the Path to Sustainable Seafood Production

European aquaculture is at the forefront of integrating circular economy principles into RAS, moving beyond basic water recirculation to encompass comprehensive resource management and waste valorization.

Denmark's "Onnest" Project: A new land-based trout farming facility, named Onnest, is planned in Hirtshals, Denmark, with the ambitious goal of becoming the "world’s first fully circular aquaculture farm." This pioneering project, led by Norwegian entrepreneurs Samuel Muren and Håkon Volden, involves a multidisciplinary team dedicated to reimagining food production through circular principles, efficient resource use, and improved fish welfare.   

The Onnest facility prioritizes zero-waste operations, local resource loops, and optimal fish health. Its design includes operating without medication or vaccines, minimizing resource consumption, and maximizing the reuse of waste streams to create truly circular food chains. A notable aspect of its circular approach is the plan to produce fish feed from algae grown on-site, which will eliminate the need for imported soy, a common aquafeed ingredient. Furthermore, sludge and nutrient waste from the fish farming process will be recycled to support this algae cultivation, and excess heat from nearby industrial operations, such as hydrogen production, will be repurposed within the facility, demonstrating a holistic approach to resource synergy. Onnest aims to achieve over 95% fish survival rates and produce high-quality fish with a significantly better nutritional profile, including improved muscle quality and higher omega-3 content. The model is designed for replicability in other regions, with potential applications in countries such as the Netherlands, France, and Japan.   

Scotland's Waste-to-Biochar Initiative: In a parallel development showcasing advanced circularity, Bakkafrost Scotland secured over £630,000 in funding in July 2025 for an innovative aquaculture recycling project, part of a total investment exceeding £2.5 million. This initiative, a first for Scotland, will convert RAS wastewater into biochar via pyrolysis at its Kishorn hatchery in Wester Ross. This process heats waste in the absence of oxygen, transforming a traditional waste stream into a valuable fertilizer for the forestry sector. This not only reduces the environmental impact of aquaculture by managing waste but also minimizes transport needs, contributing to a more sustainable and localized resource economy.   

These projects in Denmark and Scotland collectively demonstrate a strong, emerging theme of deep integration of circular economy principles within RAS. This approach extends beyond basic water recirculation to encompass comprehensive waste valorization and resource synergy. Such initiatives are positioning RAS as a leader in truly sustainable food production systems, demonstrating a commitment to minimizing environmental footprint, maximizing resource efficiency, and creating value from byproducts, thereby setting new benchmarks for the industry.