초록
Biological H<SUB>2</SUB> production from anaerobic digestion (AD) is not a sustainable pathway, based on both the efficiency of energy recovery and operation possibility in practice. Because of this, the use of AD for producing CH<SUB>4</SUB> ought once again to be considered and some exopathic measures should be studied to enhance CH<SUB>4</SUB> production. Among these, the intervention of exogenous CO<SUB>2</SUB> and/or H<SUB>2</SUB> has been demonstrated as an external approach to stimulating CH<SUB>4</SUB> production. When exogenous H<SUB>2</SUB>/CO<SUB>2</SUB> was intervened in mesophilic AD, the H<SUB>2</SUB> consumed pathways were found to change due to increased H<SUB>2</SUB> partial pressure (P<SUB>H'2</SUB>) in this study. At P<SUB>H'2</SUB>=0.96bar, hydrogenotrophic methanogens (HMs) and homoacetogens (HAs) contributed 60% and 40% respectively to the H<SUB>2</SUB> consumption, which resulted in an increased CH<SUB>4</SUB> production via the combination of homoacetogenesis and aceticlastic methanogenesis. The enumeration experiments determined that the amount of HMs was two orders higher in magnitude than that of HAs, and that K<SUB>s</SUB> (half-velocity constant) and V<SUB>max</SUB> (maximum specific substrate utilization rate) of HAs were respectively 10 times higher and 4 times lower than those of HMs. The determined kinetic parameters reveal that a low P<SUB>H'2</SUB> as in normal AD makes HAs contribute much less (2-5%) to the H<SUB>2</SUB> consumption. Based on the fact that there was an upper limit to the capacity of HMs for the H<SUB>2</SUB> consumption due to their limited amounts in the reactor, any attempts to inhibit the pathway of HAs for H<SUB>2</SUB> consumption would have no use in technology.