Analysis of economic and biological factors of waste heat aquaculture

A waste heat aqualculture system using extensive culture techniques is currently under investigation at the Oak Ridge National Lab. The system uses nutrients in waste water streams to grow algae and zooplankton which provide feed for fish and clams. A tilapia polyculture association and the freshwater clam Corbicula are the animals cultured in the system. The investigations detailed in this study have been performed to determine the economic and biological fesibility of the system and to examine energy utilization. The economic study indicated that fish producion costs of $0.24/lb were possible. This cost, however, depends upon the fish production rate and food conversion efficiency and could rise to as much as $0.75/lb. The biological studies have examined growth relationships and production potential of the cultured organisms. In the laboratory, growth-temperature optima have been deinfed (32/sup 0/C, with good growth rates between 26 and 34/sup 0/C) for tilapia hybrids. Using cage culture techniques in sewage oxidation ponds, we have obtained production estimates in excess of 50,000 lb/acre/yr. The energy utilization study indicated that, when all energy costs are included, fish from the aquaculture system may require only 35% of the net energy now required for fish products from the ocean. However,more » the energy requirements also depend on system parameters and could be large as those required for ocean-caught products. The analyses indicate that the system is economically feasible. They also indicate that significant energy savings are possible if waste heat aquaculture products replace ocean-caught products.« less