Optimization of Biogas Production from Anaerobic Co-Digestion of Fish Waste and Water Hyacinth

Abstract

Fish waste (FW) and water hyacinth (WH) are biodegradable wastes that remain underutilized and unexploited and cause environmental problems since the existing disposal techniques result in environmental pollution and health risks. Anaerobic Co-digestion of FW and WH can be used to improve biogas generation as a source of energy to replace fossil fuel consumption. The conversion of waste to energy can provide an answer to environmental pollution, waste treatment and management, and rising energy costs. Experimental variable levels for biogas were substrate ratio (WH: FW, 25-75g), inoculum concentration (IC, 5-15g), and dilution (85-95mL). Design-Expert 13 was used for optimization and results analysis. Response surface methodology (RSM) was used to examine the effects of operating parameters and identify optimum values for biogas yield. Optimum values for maximum biogas yield of 690mL with the highest methane yield of 68.15% were found to be WH: FW ratio, 25:75g, 15g of IC, and 95 mL for dilution. The yield was 16.1% and 32.4% greater than FW and WH mono-digestion, respectively. Using a quadratic equation, the biogas yield was expressed as a function of operating variables. The model was significant (P < 0.05). All factors had significant linear and quadratic effects on biogas while only the interaction effects of the two factors were significant. The coefficient of determination(R2) of 99.9% confirms the good fit of the model with experimental variables.