Optimizing Feedstocks Mixing Ratio and Hydraulic Retention Time for Biogas Production From Anaerobic Codigestion of Dairy Manure and Aquaculture Sludge

Aquaculture sludge (AS), rich in nutrients, can pose environmental risks such as eutrophication, threatening aquatic ecosystems and water quality if not properly managed. However, AS can also be used as a feedstock for bioenergy production. This study investigated bioenergy (methane) production from AS and dairy manure (DM) under anaerobic codigestion using the biochemical methane potential test. Results showed that anaerobic codigestion of DM and AS produced higher methane production compared with their individual monodigestion. The DM:AS ratios of 50:50, 30:70, and 10:90 showed synergistic effects, with codigestion performance indices of 1.2, 1.3, and 1.5, respectively. A DM:AS ratio of 10:90 provided the highest methane production of 341.80 mL g⁻¹ volatile solids, being 65% and 52% greater than those from monodigestion of these two feedstocks, respectively. A hydraulic retention time of 16 days was found optimum, attaining 90% of the cumulative methane production. The experimental data of methane production fitted perfectly with the superimposed model, reflecting contribution from both readily degradable and harder fractions of the feedstock mix. These findings present an approach to effective valorization and management of the nutrient-rich AS through enhanced energy recovery and promote sustainability in the aquaculture industry.