The utilization of compost heat in small-scale aquaculture

Heat generated from composting fresh animal manure was collected with steel and copper heat exchangers. Water was pumped through the heat exchangers at a constant flow of 2 L/minute. The effluent temperature showed an average increase (ΔT) of 5.7 C and 3.5 C for steel and copper, 3 respectively. A volume of 5.9 m³ of compost maintained these temperatures for an average of 15 days per run. In a series of tests, water flow rates of 1.0, 2.0, 3.0, and 4.0 L/minute experienced an average increase in temperatures of 8.1, 4.5, 3.2, and 3.2 C for steel and 5.9, 3.1, 1.9, and 1.6 C for copper, respectively. These tests were run for one 60-minute period on 6 consecutive days.

The application of this heat source in a recirculated system design showed an average increase in temperature of 4.8 C. It was observed that increased moisture of the composting material decreased the biological activity, i.e., heat generating capacity, of the compost heap. The technique showed potential for warming water when applied to small volume aquatic systems.