Anaerobic digestion of fish waste and seagrass/macroalgae: potential sustainable waste management for tropical Small Island Developing States

This study presents the preliminary investigation of the biogas production potential from fish wastes (FW) and seagrass (SG) mixed with macroalgae (MA). Substrates were prepared for total solids of 10-12% and were analysed in Biochemical Methane Potential (BMP) assays. The inoculum used in all BMPs was acclimated sludge in a ratio of 1:3 for inoculum to substrate on a mass basis. There were effectively four vessel reactors (VRs) with different compositions: VR1 100% fish wastes, VR2 60% fish wastes and 40% seagrass/macroalgae, VR3 40% fish wastes and 60% seagrass/macroalgae, and VR4 100% seagrass/macroalgae. VR5 acted as control with 100% inoculum. The maximum cumulative biogas productions (CBPs) reached 8288 ml for VR1, 8410 ml for VR2, 4236 ml for VR3 and 2746 ml for VR4 with a concentration of methane gas of 61.1, 65.07, 68.07, and 53.28%, respectively. One-way ANOVA test results (p < 0.05) indicated that there was significant difference in the variations in VS, salinity, COD, soluble COD and cumulative biogas production amongst the test vessel reactors. This potential for biogas production represents a clean source of cheap fuel for sustainable development in Small Island Developing States having aquaculture and seafood industries along coastal regions.