What is it?
Ragn-Sells Havbruk, together with partners in the aquaculture sector, has developed systems to collect and process fish sludge – the mix of uneaten feed, excrement, and organic matter that accumulates in aquaculture. Traditionally, much of this sludge has been discharged into fjords, contributing to pollution and nutrient loss.
Through innovations such as LiftUP technology, which captures sludge directly from pens, and the patented Ash2Phos process developed by Ragn-Sells’ innovation company EasyMining, nutrients such as phosphorus and nitrogen can be recovered, while organic matter can be converted into biogas. This approach transforms sludge from an environmental liability into valuable resources for agriculture, energy, and industry (Ragn-Sells, 2023).
Why is this important?
- Environmental impact: uncontrolled sludge release causes eutrophication and marine pollution.
- Resource recovery: phosphorus is a critical raw material, largely imported from geopolitically sensitive regions, and domestic recovery improves resilience (Ragn-Sells, 2023).
- Sector growth: as aquaculture expands, sustainable waste management is essential for maintaining license to operate.
- Circular economy: turning waste into fertilizer and renewable energy contributes to national and EU sustainability goals.
Main resource strategy
Closing the loop – capturing fish sludge and extracting nutrients and energy for reuse.
Other resource strategies
- Narrowing: efficient sludge collection and optimized processing minimize material and nutrient losses.
- Slowing: nutrients re-enter agricultural cycles, extending their utility.
- Regenerating: ecosystem degradation is reduced by preventing uncontrolled nutrient leakage to fjords.
Business model aspects
Value Proposition
- For aquaculture companies: regulatory compliance and a reduced environmental footprint.
- For agriculture: access to high-quality recycled phosphorus and nitrogen for fertilizers.
- For energy providers: renewable biogas derived from organic waste streams.
- For society: reduced marine pollution, improved food security, and more resilient nutrient cycles.
Value Creation & Delivery
- Sludge captured using LiftUP and associated filtration systems (Ragn-Sells Havbruk, n.d.).
- Processing through dewatering, anaerobic digestion for biogas, or incineration followed by Ash2Phos nutrient extraction (FishFarmingExpert, 2024).
- Sale of recovered phosphorus, nitrogen, and biogas to agricultural and energy markets.
- Partnerships across aquaculture firms, technology providers, and research institutions.
Value Capture
- Revenues from the sale of recycled phosphorus and nitrogen products.
- Energy revenues from biogas production.
- Cost savings from avoided waste treatment fees or environmental penalties.
- Recognition and funding linked to sustainability leadership (Ragn-Sells, 2024).
Strategies for degrowth / sufficiency
By recycling nutrients already in circulation, Ragn-Sells reduces the need for new phosphorus mining and fossil-based fertilizers, supporting sufficiency, resilience, and reduced dependence on finite global resources.
Business model experimentation practices
- Pilot projects, including a full-scale sludge collection system installed at Eide Fjordbruk (Ragn-Sells, 2023).
- Technology development, including an Ash2Phos facility in Helsingborg, Sweden, designed to recover more than 90% of phosphorus from sludge ash (FishFarmingExpert, 2024).
- EU collaboration through the AquaPhoenix project, with a reported budget of NOK 120 million, testing sludge collection, circular uses, and environmental outcomes (AquaPhoenix, 2023).
- Policy experimentation involving engagement with regulators to enable recovered phosphorus to be used in feed and fertilizer despite existing waste classifications.
Tools, methods and approaches used
- LiftUP technology for sludge collection from net pens.
- Ash2Phos chemical recovery process for phosphorus extraction.
- Anaerobic digestion for biogas production.
- Life-cycle assessments and environmental monitoring of pilot projects.
- Multi-stakeholder collaboration across industry, academia, and public partners.
Sustainability outcomes
- Potential to capture approximately 334,000 tonnes of fish sludge annually in Norway, increasing to over 1 million tonnes by 2050 (Ragn-Sells, 2023).
- Biogas potential estimated at 112–309 million cubic metres of methane, equivalent to the energy needs of around 600,000 households (Ragn-Sells, 2023).
- Recovery of approximately 11,000 tonnes of phosphorus annually, with potential to triple by 2050 (Ragn-Sells, 2023).
- Planned Ash2Phos facility in Sweden designed to process 30,000 tonnes of sludge ash per year and recover more than 90% of phosphorus (FishFarmingExpert, 2024).
- Recognition through the SIVA Award 2024 for sustainable innovation in the seafood industry (Ragn-Sells, 2024).
- Significant reduction in nutrient discharge to fjords, protecting marine ecosystems while creating new circular value chains.
Sources:
Ragn-Sells Havbruk. (n.d.). Fiskeslam. https://www.ragnsells.no/tjenester/bedrift/havbruk/fiskeslam/
Ragn-Sells. (2023). Circular solution for sludge recycling in Norwegian fish farming. https://newsroom.ragnsells.com/posts/pressreleases/circular-solution-for-sludge-recycling-in-norwegian-fish-farming/
Ragn-Sells. (2023). Norwegian fish poo can power 600,000 households. https://newsroom.ragnsells.com/posts/pressreleases/norwegian-fish-poo-can-power-600000-household
Ragn-Sells. (2024). Awarded for sustainable solutions in the seafood industry. https://newsroom.ragnsells.com/posts/pressreleases/ragn-sells-norway-awarded-for-sustainable-sol
FishFarmingExpert. (2024). Recycling company will recover phosphorous from salmon sludge. https://www.fishfarmingexpert.com/ash2phos-technology-helsingborg-phosphorus-recovery/recycling-company-will-recover-phosphorous-from-salmon-sludge/1881078
AquaPhoenix. (2023). EU project on sludge collection and circular uses of aquaculture waste kicks off. https://aquaphoenix.eu/article/aquaphoenix-a-unique-eu-project-on-sludge-collection-and-circular-uses-of-aquaculture-waste-kicks-off-in-person/
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About project Circular X
Project Circular X is about ‘Experimentation with Circular Service Business Models’. It is an ambitious research project funded by the European Research Council (ERC) which supports top researchers from anywhere in the world. Project CIRCULAR X runs from 2020-2026. The project is led by Principal Investigator (PI) Prof Dr Nancy Bocken, who is joined by a multidisciplinary team of researchers at Maastricht Sustainability Institute (MSI), Maastricht School of Business and Economics, Maastricht University. The project cooperates with businesses who want to innovate towards the circular economy.
Project Circular X addresses a new and urgent issue: experimentation with circular service business models (CSBMs). Examples of such new business models include companies shifting from selling products to selling services and introducing lifelong warrantees to extend product lifetimes. However, CSBMs are far from mainstream and research focused on experimentation is little understood. The research aims to conduct interdisciplinary research with 4 objectives:
- Advancing understanding of CSBMs; their emergence and impacts
- Advancing knowledge on CSBM experimentation
- Developing CSBM experimentation tools
- Designing and deploying CSBM experimentation labs
Funding source
This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme, grant agreement No. 850159.
Using this information
When you refer to this case, please use the following source:
Circular X. (2026) Case study: Ragn-Sells – Circular Valorization of Fish Sludge. Accessed from www.circularx.eu
