Marine Donut was a technological breakthrough for closed aquaculture at sea. Now we have taken the next step. Marine Donut 2.0 has been developed based on several production cycles with close to 400,000 salmon in total.
And in close collaboration with SalMar, one of the world’s largest aquaculture companies. The experience gained during the pilot phase has been analysed and actively used in the redesign.
The result is a structure that is stiffer, easier to build and more predictable in operation — and developed for industrial-scale production.
Marine Donut 1.0 has completed several production cycles, from stocking salmon of around 2 kg to harvesting market-size fish of approx. 5 kg. The results show a stable water environment with good oxygen levels and safe CO₂ values. The fish displayed normal behaviour, low stress levels and good welfare throughout the period, with low mortality (0.2%) and no need for delousing or lice treatment.
Harvest results were very good, with strong product quality and a high superior share (98.5%). No escapes have been recorded either.
“ This confirms that the biological foundation for closed aquaculture at sea works in practice — not just in theory. Nils Johan Tufte, CEO Bluegreen Group
Marine Donut 1.0 was, and still is, the world’s largest structure built in thermoplastics. This also meant that we moved into an area with limited experience and few established standards. The final report points in particular to one key area for improvement: how the structure and material behave over time at sea.
During operation, damage was observed in the structure related to temperature impact, long-term material loading and how the stiffness of thermoplastics develops over time. Fortunately, this did not affect biological performance, but it is crucial for how robust the structure is, how long it lasts, and which sites it can be used at.
No escapes were recorded, and the barrier solutions at the inlet and outlet worked well. But the incident illustrates how important it is to have good control of how the structure behaves over time — and that it must be robust enough to handle different operating and production conditions.
This is important learning in development projects of this kind, and insight that we are turning into concrete improvements before the technology can be industrialised.
Marine Donut 2.0 has been developed directly on the basis of measurements, operational experience and analyses from 1.0. The changes are not cosmetic, but the result of a targeted redesign of the structure.
Simplified and reinforced structure
The structure has been made stiffer and better adapted to the loads it is exposed to over time at sea. Based on the experience from 1.0, new structural reinforcements have been added, including twin-wall elements, reinforcement along the centre line and reinforcements in the outlet areas. At the same time, the design has been further developed with greater consideration for how the thermoplastic material behaves over time, where temperature, load level and duration all affect the material properties.
In practice, this means that loads are distributed more effectively throughout the structure, critical areas have been reinforced, and the design takes greater account of creep and long-term deformation. Together, this provides better control of how the structure develops during operation and reduces the risk of unwanted deformation over its lifetime.
While Marine Donut 1.0 was designed and certified for more sheltered conditions, 2.0 has been developed to handle higher wave loads and more demanding sites. This expands the area of use and makes the technology relevant for a larger share of fish farmers’ site portfolios.
The result is a solution that is more robust, more stable in operation and more predictable throughout its full 20-year service life.
Illustration of Marine Donut 1.0 vs 2.0. The reinforcements in the structure are marked in blue.
The result is a structure that is stiffer, easier to build and more predictable in operation — and developed for industrial-scale production.
Optimised for installation and operation
The experience gained from the pilot facility has also led to concrete improvements in installation and day-to-day operation.
The machine room has been moved above the waterline, simplifying both construction and maintenance. Pipe routing and technical installations have been redesigned according to lean principles to reduce complexity and weight.
The structure is now more stable during construction, transport and launching. This makes logistics easier and reduces the need for adjustments at the construction site and location.
Accessibility has been improved, hatches have been made lighter for easier handling and fish husbandry, and the fish emptying system is more user-friendly and adapted for exposed sites. The latter can now be operated from one of the facility’s three walkways, rather than from a separate barge. These are not just technical improvements — they are practical HSE improvements for the operator who uses the facility every day.
Smarter oxygenation — lower operating costs
In Marine Donut 2.0, the water handling system has been further developed with the aim of smarter integration and better overall economics. At lower water exchange rates in the facility, the oxygenation system is now designed so that it does not depend on the main pumps for oxygen addition. Instead, dedicated oxygen systems are used to add oxygen directly into the fish volume.
Based on measurements and analyses from Marine Donut 1.0, the water flow has also been optimised. The flow generator design has been further developed, and the placement of both flow generators and intakes has been adjusted to provide a more even and efficient flow-through. The outlet area has been increased to reduce water velocity across the screens.
Better control of sludge and feed
In Marine Donut 1.0, sludge collection worked visually, but the pilot setup provided a limited basis for fully documenting the effect. In 2.0, sensor technology, camera placement and feeding control have therefore been further developed to provide better control of feed input, reduce waste and improve documentation of particle transport and sludge collection.
This provides a better basis for both operations and continued documentation of environmental impact.
Biology integrated into the development
Technology and biology must be developed hand in hand. The pilot facility has already delivered very strong biological results, and we intend to continue that.
Bluegreen’s own marine biologist, Ina Kristine Andersen, has therefore been closely involved in the further development of 2.0 to ensure that structural changes do not negatively affect fish welfare — and to optimise conditions even further.
Among the measures are:
The outlet area has been increased to ensure better handling of dead fish
Light placement has been evaluated with feed factor in mind
Sensor technology and camera placement have been assessed for better feeding control
The goal has been to combine a robust structure with strong biological performance and control.
Designed for assembly-line production
One of the biggest differences in 2.0 lies in how it has been adapted for production.
Marine Donut 2.0 has been developed to be produced according to an industrialised model, where bottom sections and top sections are prefabricated, outfitted, assembled and completed in a structured production flow.
The patented twin-wall panels are produced in-house and can either be delivered directly to a project or built up as stock. This enables better planning, higher delivery reliability and scalable capacity.
Standardisation has been a key principle. For example, the facility can now be delivered with or without UV treatment without requiring extensive customisation in production. Less tailoring results in better flow, lower cost and more predictable delivery.
“ Marine Donut 2.0 is quite simply designed to be built again and again — efficiently and profitably, in Norway and internationally. Henrik Thorstensen, CTO Bluegreen
For fish farmers, this ultimately comes down to one thing: long-term profitability.
With Marine Donut 1.0, the technology has been documented to work biologically. With 2.0, the structure has been further developed to be more robust, more predictable and better suited for operation at a wider range of sites.
One of the biggest advantages of closed aquaculture at sea is precisely the level of control it provides. In open systems, production is continuously affected by conditions in the sea — with lice, algae, jellyfish and temperature fluctuations as part of everyday operations. In a closed structure, these factors can largely be kept out, creating a more stable production environment throughout the entire cycle.
The structure is developed for long service life, high operational reliability and industrial production. This means that fish farmers can invest in a facility that delivers on what matters most: good fish welfare, high biosecurity, and stable, predictable production conditions — resulting in consistent fish quality with a high superior share.
All in all, this provides strong profitability with a short ROI.
