Very Low-Temperature Geothermal Utilization in Fish Farming in Iceland - A Case History from the Silfurstjarnan Ltd, Iceland

Abstract

Due to limited knowledge on geothermal resources in the lowest temperature range Orkustofnun initiated a research programme in and joined with local authorities or companies in combined studies of a number of target areas suitable for fish farming. A case history from the Silfurstjarnan Ltd fish farm is presented. This fish farm utilizes a huge artesian ground water reservoir (4-6?C) in a pillow lava formation, located below the fish farm. Below the layer of cold fresh water, warm water reservoir (20-38") exists in the same rock formation at greater depth. In a model of cascaded use, the warmest water is first used for domestic heating, then used for snow melting, before being mixed with the fish rearing water. At present no water is recycled nor reinjected. A unique set up for draining cold seawater from an open ocean sand beach was invented and installed. About of clear seawater at ambient temperatures are collected and pumped to the fish farm, where they are mixed with 800-900 of cold fresh water and 100-200 of warm water. The fish rearing temperature can be decided at will, but is most commonly maintained about which is the optimal growing temperature for salmon. Due to the seasonal temperature variations of the seawater (1-9?C) and the cold groundwater, the geothermal water is vital for the temperature control. Thus, the geothermal reservoir is one of the chief benefits of the fish farm. Another important factor is the superb quality of the natural resources being entirely free of pollution. Not a single dose of medicine has been used hitherto, nor has the farm suffered any kind of fish disease. These benefits have resulted in high prices for the fish product so far. Three times a week, the year around, fresh fish products are on European and American markets, 1-3 days after despite the remoteness of the fish farm. The authors believe that huge possibilities exist for land based fish farming of salmonides by using existing resources of geothermal energy.