FREA is the abbreviation of Fully Recirculated Aquaculture system. This innovative fish farming concept takes recirculation within fish farming to a new technical and environmental level, as the mind-set behind recirculation is implemented 100 % in the entire process.
THE BASIC PRINCIPLES IN THE FREA CONCEPT
- In a recirculation system of this type there is no direct discharge to the surrounding water environment. The particulate matter is removed and fermented for later use as fertilizer or biogas fuel. The outlet water is lead into large infiltration basins, where the water will seep for later full or partly re-usage in the production on the farm.
- If the farm is established on poor soil with a large content of sand and gravel, where the natural given conditions for water extraction and seepage of the needed water amount will be substantially better than on soil with mould and clay.
- The water extraction is constructed as drainage in 4-5 meters depth, depending on soil, and the positioning will be partly under the seepage zone and on the ground next to the seepage zone. The seepage zone is established as basins with horizontally placed overflow pipes in the centre for equal distribution of the outlet water.
- The water exchange in the FREA farm consists of the spray bar water that can be used for cleaning the drum filter (if such mechanical cleaning is installed), backflushing of bio filters and evaporation. The resulting need for fresh water will be in the range 40-80 l/s and only consists of groundwater.
- The limited exchange of water gives a residence time of water in the farm of approx. 6 days, which can be compared to the legal minimum requirement of 18.5 hours in a Danish model farm type 3. The size of the farm and the high recirculation intensity furthermore has the advantage, that the effect of the cleaning measures is substantially increased.
- The cleaning of the water is handled by leading the water over sludge cones, after which the water is lead via both fixed bed and moving bed bio filters. There are no drum filters installes in the FREA A/S project, but the design of the farm leaves up space for drum filters, if this should be deemed necessary later on.
- When the FREA farm is sectioned in separate units for hatchery, fry, fingerlings and ongrowing and further split takes place within the individual units, in which way a substantial reduction of the risk of severe disease outbreaks and contamination is established. The sectioning into separate units and sub-units also enables to use the “all in – all out” principle in the production planning, which is in line with the general principles for production of other livestock.
- As the production is purely based on draining water and groundwater the risk of pollution with substances damaging to the environment from water streams will be removed.
- When the FREA A/S project is fully built an average energy consumption of approx. 1.5 kWh per kg feed is expected.