The effect of reduced pressure and glucose concentration on hydrogen and volatile fatty acid yield: The role of homoacetogenesis

Abstract

In this study, the influence of headspace pressure (HP; 20–100 kPa) and organic loading rate (OLR; 10–30 g/L) on H2 and volatile fatty acid (VFA) yield were investigated. The experiments were carried out in the semi-continuous mode, the main products in VFAs were ethanol and butyrate, which accounted for more than 75%. More than 79% generated H2 was consumed through homoacetogenesis pathway when HP was 100 kPa, and lowing HP could effectively promote the accumulation of H2 (increased by at least 2 times). Even though consumed H2 through homoacetogenesis was related to OLR and HP, the lower HP was more likely to reduce this part H2 consumption, especially under 10 g/L condition. As for acid production rate, both OLR and HP have a significant effect (p < 0.05). Maximum acid production rate was 489.86 mg-COD/g-CODdegrade·d−1when OLR was 20 g/L and HP was 40 kPa.