Recirculation aquaculture is a technology for farming fish or other aquatic organisms. It’s environmentally friendly and highly productive, and is based on closed farming systems where most of the water is reused. One of the world’s biggest smolt plants is located in Belsvik. I got to visit Lerøy Belsvik on a trip arranged by one of the courses at NTNU (BT3210 Recirculating aquaculture systems RAS).
We arrived at Lerøy Belsvik after a two-hour bus drive. After an interesting presentation, we were given a tour of the facilities. Lerøy Belsvik was opened in 2013, and consists of 11 separate recirculating aquaculture systems, with three hatcheries and 8 grow-out departments. Fertilized eggs are hatched into small salmon. After 39 weeks, these small salmon have developed into smolt. The fish is then transferred to aquaculture farms in the sea .
It was fascinating to see the amount of biomass in each tank. You couldn’t see the bottom of the tank due to the large number of fish. Lerøy Belsvik produces 14 million smolt each year. All though the water looked dirty, it is very clean and maintains optimum conditions for the fish. The plant is world class when it comes to recycling. 98% of all the water in the system is reused . The water in recirculating aquaculture systems is cleaned in several steps. Solids, such as fecal material and uneaten feed, is removed by mechanical filtration. Bacteria consume ammonia and converts it into nitrate in special bio filters. Nitrate is relatively non-toxic to fish and may safely accumulate in the tank until it is flushed out by replacement water or converted to gaseous nitrogen. Nitrogen is released harmlessly into the atmosphere. Carbon dioxide is removed, and the culture water is re-oxygenated as it is returned to the grow-tank.
The design of Lerøy Belsvik is influenced by the concern for the environment. Several filters are used to recycle the water, which reduces drainage and therefore also minimizes the risk of escapes. The energy is retrieved from the sea, and thus the usage is low. The sludge created from water filtration is used as soil, fertilizer and to produce biogas .
I had a great trip to Lerøy Belsvik, and learned a lot! You should definitely visit if you get a chance!
Written by Emilia Henriksson