Simultaneous production of hydrogen and volatile fatty acids from anaerobic digestion of Macrocystis pyrifera biomass residues

The Macrocystis pyrifera biomass residues(MPBRs) after extraction of algin could be applied in anaerobic fermentation. The effects of different pretreatment conditions, substrate concentrations and initial pH values on hydrogen and volatile fatty acid(VFA) production during the anaerobic fermentation of MPBRs were evaluated. The optimal pretreatment conditions, substrate concentration, initial pH values were determined as thermo-alkaline pretreatment at 100 °C with 0.1 mol/L NaOH, 40 g/L and 7.0, respectively. Under these conditions, the maximum hydrogen production was 11.38 mL/g(volatile solids, VS), which was approximately 23 times higher than that of untreated MPBRs. Furthermore, the maximum total volatile fatty acid(TVFA) yield was found to be 0.055 g/g(VS) and the VFA mainly consisted of acetic and butyric acids. The results indicate that the yield of TVFA is positively correlated with hydrogen production, and the MPBRs could produce hydrogen and TVFA simultaneously. In addition, thermo-alkaline pretreatment is proven to be the best method for hydrogen and VFA production.