Use of Hydrothermal Pretreatment to Enhance Biogas Production from Pelagic Sargassum.

Excessive amounts of pelagic Sargassum arriving at Mexican coastlines result in the deterioration of soil and water quality and the endangerment of endemic aquatic species, so far proper management strategies for this biomass are not being developed. Anaerobic digestion is a well-established technology for energy recovery of organic residues. However, the conversion of Sargassum is unsatisfactory as it was confirmed in this study with only 21% of theoretical methane yield. To make this conversion strategy more favourable, pretreatment is recommended. The present work compares the effectiveness of steam explosion and extrusion to increase digestibility of Sargassum. Both methods were found to improve the bioconversion of the macroalgae by nearly 80%. The solubilization of organic matter with a yield of 145 ± 3.8 mg of chemical oxygen demand (COD) per g of dry biomass (TS) obtained by steam explosion was significantly higher than that of extrusion giving rise to 64.2 ± 7.1 mg COD g−1TS. In contrast, the methane yield evaluated in batch assays for both treatments was significantly the same with 114 ± 4 mLN CH4 per gram of volatile solids (VS) for the conversion of steam-exploded substrate and 108 ± 6 mLN CH4 g−1VS when extrusion as pretreatment method was applied. In summary, extrusion may be the preferred technology to tackle this kind of biomass as removal of salt is intrinsically tied to dewatering stream. [ABSTRACT FROM AUTHOR]