Investigating methane production potential of Sargassum muticum (Yendo) Fensholt via response surface methodology

This study investigates the influence of inoculum to substrate ratios, substrate length, and freezing on the anaerobic digestion of the brown macroalga Sargassum muticum through batch experiments. Methane production optimisation was performed using response surface methodology with a central composite design. Biochemical methane potential tests conducted on frozen algae underscore the significant impact of the inoculum to substrate ratio, revealing that a ratio of 2 enables a high hydrolysis rate without apparent phenomena that limit methane production. In terms of modelling, the first-order model provided more accurate biochemical methane potential estimations than the Gompertz model. Furthermore, using fresh algae resulted in a 21% increase in methane production per kilogram of volatile solids compared to frozen samples. The study also confirms that high endogenous methane production can compromise BMP assay reliability. A methane potential range of 170-270 NL CH₄·kg VS^-1 was established allowing an initial assessment of energy production. The examination of Sargassum muticum contributes to the understanding of marine biomass anaerobic digestion processes and demonstrates its potential as a renewable energy source.