Biochemical Methane Potential of Recirculating Aquaculture System Sludge Under Different Salinity Conditions and Biochar Effects

In this study, the biochemical methane potential (BMP) of recirculating aquaculture system (RAS) sludge in freshwater, brackish, and seawater conditions was determined, with and without biochar. Freshwater conditions yielded the highest biogas (804 ± 16 mL·gVS⁻¹), followed by brackish (744 ± 3 mL·gVS⁻¹) and seawater (571 ± 13 mL·gVS⁻¹). Adding biochar increased biogas yields by 6%, 4%, and 10% under freshwater, brackish, and seawater conditions, respectively. CH₄ content was between 63.2–65.8% in all conditions, but it required longer time in seawater (12.9 days) to reach over 63% while it took 7.2 days in both freshwater and brackish water. These findings underscore biochar's potential to enhance anaerobic digestion across varying salinity levels.