Biohydrogen Fermentation from Sucrose and Piggery Waste with High Levels of Bicarbonate Alkalinity

This study examined the influence of biohydrogen fermentation under the high bicarbonate alkalinity (BA) and pH to optimize these critical parameters. When sucrose was used as a substrate, hydrogen was produced over a wide range of pH values (5–9) under no BA supplementation; however, BA affected hydrogen yield significantly under different initial pHs (5–10). The actual effect of high BA using raw piggery waste (pH 8.7 and BA 8.9 g CaCO 3 /L) showed no biogas production or propionate/acetate accumulation. The maximum hydrogen production rate (0.32 L H 2 /g volatile suspended solids (VSS)-d) was observed at pH 8.95 and 3.18 g CaCO 3 /L. BA greater than 4 g CaCO 3 /L also triggered lactate-type fermentation, leading to propionate accumulation, butyrate reduction and homoacetogenesis, potentially halting the hydrogen production rate. These results highlight that the substrate with high BA need to amend adequately to maximize hydrogen production.