Valorization of brown macroalgae Sargassum plagiophyllum for biogas production under different salinity conditions

This study investigates the biogas production from Sargassum plagiophyllum under different salinity using a semi-continuous reactor. Inoculum preparation was conducted by mixing the two prepared S. plagiophyllum juice (deionized and saline water) with the cow manure using a ratio of 1:1. Once every two days, 5 % of the substrate was replaced with 5 % of fresh macroalgae juice continuously. The results found that cumulative biogas production in deionized water was 3.7 times higher than in saline water after 30 days. It could be attributed to anaerobic bacteria growth inhibited by salt. The maximum cumulative methane and biogas yields in the deionized water digester were 266.18 mL/g-VS and 371.76 mL/g-VS, respectively. The kinetics of the methane production was also determined, and the experimental data fitted well with the modified Gompertz model. These results indicate that S. plagiophyllum, under low salinity conditions, can be developed as a feedstock for biogas production.