Introduction
There has been a lot of “buzz” concerning the farming of slaughter size salmon on land. Numerous projects have been planned across the world, most of them with the use of RAS technology. However, many facilities have yet to successfully produce significant quantities of slaughter sized fish. Overall, access to investment capital has been difficult in recent years due to the turbulent international climate. In addition, the technology for landbased grow out have not had many “proofs of concept” to decrease the perceived investment risk, with several significant challenges reported from the “first movers”. Some of the more pronounced challenges communicated have been related to H2S formation and poor biological performance due to high temperatures. In the face of these challenges, some projects have focused on hybrid/ reuse technologies, and currently the worlds biggest land-based salmon farm (Salmon Evolution Indre Harøy) is a hybrid system.
What is Hybrid Technology?
Hybrid technology, or reuse technology, is a solution “between” flow through systems and RAS in terms of water consumption. Flow through systems adhere to the classical saying “the solution to pollution is dilution” and are based on flushing large amounts of water through a system, usually with limited water treatment. RAS (recirculation aquaculture systems) use minimal inlet water, continuously treating and reusing the main water volume through advanced water treatment systems, including a biofilter. Hybrid systems, being in between, usually have about 1/3rd to 1/4th of new water going into a hybrid tank, while the rest of the water volume is reuse of tank water after aeration, oxygenation and sometimes filtration.
For hybrid systems, the water intake is still low enough to allow for cost-effective treatment, typically involving pressure filtration followed by UV disinfection. Biofilters are generally omitted, as the water exchange rate keeps ammonia levels under control. Heat exchangers are used between inlet and outlet flows to ensure cost-effective heating and/or cooling.
Why and Where is Hybrid Technology a Solution?
When considering a new facility, location is a key factor. Many parameters are given and hard to control, such as temperature (both of the water source and on land), available nearby infrastructure, area at disposal, inlet water quality, and applicable discharge policy. One of the first questions in early-stage project development is the availability and quality of inlet water. If only limited volumes are accessible, or the water quality is poor, RAS may be the only viable solution (within “financial reason”). In Norway, one of the leading aquaculture nations these days, it is typically limited access to fresh water and vast access to high quality sea water. As Atlantic salmon spends its first life stages in fresh water, but displays better growth in later stages in sea water, water access will likely be variable dependent on fish size. The next consideration is local discharge regulations: if discharge allowances are highly restrictive, RAS may again be the only feasible approach. However, in locations with sufficient water availability and moderate discharge permissions, hybrid systems offer a compelling alternative.
Atlantic salmon has evolved to thrive in the Atlantic Ocean as it passes its smoltification stage, and thus logically prefer temperatures around 12 Cº. Temperature in the inlet water can be easily adjusted, it is simply a question of cost in terms of process equipment and electricity. If the temperature of the water source is far off optimal values, it is natural to minimize the amount of water needed to be heated or cooled. However, in many large aquaculture areas such as Norway, there is a high availability of water with approximately the correct temperature, making hybrid technologies not only possible, but also sensible. It is also worth noting that in warm climates, RAS can struggle with elevated water temperatures due to limited water inflow and heat from extensive pumping. Warm climates may as such profit from a larger volume of cooled inlet water, if available.
Growth of Atlantic salmon to slaughter size is beneficial in sea water, again due to the natural habitat of the species. However, recent years have unfortunately made the risks of H2S formation in sea water systems well known. Biofilters are often the areas of problem, due to a build up of particles. This problematic component is eliminated in hybrid systems, although careful design of water hydrodynamics to prevent dead zones is still crucial.
Particles are also a known challenge in RAS, and as the same organic matter is pumped numerous sequences through the water treatment loop, they disintegrate and become harder to remove and more readily available as nutrients for bacterial growth. Needless to say, less recirculation means less pumping, and thus the particles are more easily removed.
Financial Aspects – a Cost Evaluation of Hybrid Technology on Land
In January 2025 the sale of the fish farming company Nova Sea was announced, enabling the estimation of market value of the acquirement of production capacity in Norway at around 260 NOK/HOG. Recent budget prices for construction of land-based hybrid systems* presents investment cost at comparable or lower levels, thus the construction cost should be attractive for those looking to acquire more production capacity.
The Worlds Biggest Land-Based Salmon Farm – a Story of Success and Discipline
The worlds biggest land-based salmon farm, measured in yearly production, is currently the Salmon Evolution farm at Indre Harøy in mid-Norway designed and built by Artec Aqua. The farm delivered close to 5 000 tonnes (HOG) of salmon in 2024, with 6 000 - 6 500 tonnes (HOG) expected to be harvested in 2025 from its first build-out. The second build-out is under construction and will more than double the production capacity. Each building phase consists of 12 tanks of 5000 m3, and a total of 48 tanks are planned.
When designing this fish farm, the advantages of the location have played a vital part. The clean and temperate sea water in the vicinity, as well as the currents available to minimize the impact of wastewater on the recipient, has made this location a prime candidate for hybrid technology. Significant effort was made to plan and design a project with low risk. A key risk factor in RAS, the biofilter, was omitted due to the choice of hybrid technology.
The project itself was huge, with 15 000 m3 of concrete, 35 000 m of pipes and 700 000 working hours. Such a complex project demanded professional project management, but more importantly, careful planning and engineering. Experience from design of brood stock facilities, handling big fish, and smolt facilities, handling large amounts of fish, was crucial. As historical experience and references was related to smaller facilities, handling upscaling became a challenge. Numerous suppliers had to reinvent their products, such as heat exchangers, to fit the scale. Also, careful calculations related to, for instance, tank hydrodynamics and aeration needed to be performed. It all had to be done with the utmost discipline, to be correctly performed while staying withing time and budget. And thanks to the immense effort of the participants, the success became a fact, and the second building stage is on track.
What Comes Next
The first large hybrid system is up and running. More systems are on the sketching pad. What comes next? First of all, the hybrid system is not a fixed system, continuous improvement and refinement is necessary. As the operational experience from the current system is gained, feedback is implemented in the next designs. New types of technologies such as filters and pumps are considered. Optimization in terms of energy consumption will be done. Further, each facility needs to be customized for its specific location with its attributes and limitations. Nobody knows exactly what the future holds, but it is safe to say that hybrid systems are seemingly a serious competitor to RAS in many future projects.
*Numbers provided by Artec Aqua AS.