Abstract:
Biogas production from organic wastes from the recirculating aquaculture systems was conducted in this study. The experiment aimed to evaluate biogas production potential with 3 types of organic wastes including (1) Biofloc; suspended solid collected from biofloc aquaculture system (2) Feces; fish feces separated from recirculating aquaculture tank by continuous sludge separator and (3) Sludge; aquaculture waste that consist feces and uneaten feed from close system aquaculture tank. The experiment was conducted in 100 ml serum bottles using Biochemical Methane Potential (BMP) technique for a duration of 42 days. The result showed that Feces had the highest methane yield production of 175.28±16.62 mL CH4/g VS substrate. Then the ratio between organic waste and biogas inoculum i.e. 1:4, 2:3, 1:1, 3:2 and 4:1 were varied in serum bottles, in order to determine the optimum ratio that offer the maximum biogas yield. The optimal substrate to inoculum ratio at 3:2 gave the highest methane yield of 194.10±1.98 mL CH4/g VS substrate. However, statistical analysis indicated that methane yield of substrate to inoculum ratio at 3:2 and 4:1 was not significant different (p>0.05). Hence, feces with the inoculum ratio of 4:1 was chosen for further experiments. The effect of total solids content and retention time on anaerobic digestion were investigated in batch reactors with 3 total solid (TS) concentrations of feces i.e. 30, 50 and 100 g TS/L. The results showed that organic aquaculture waste at 50 g TS/L provided the highest methane yield of 111.72 mL CH4/g VS substrate. On the other hand, high organic waste concentration of 100 g TS/L inhibited the methane yield as due to a result of high volatile fatty acids concentration. The results from this research revealed that the optimal retention time of organic aquaculture waste (feces) for batch biogas production was 15 days with the methane yield of 138.23 mL CH4/g VS substrate, respectively.