초록
<P><B>Abstract</B></P> <P>The feasibility and performance of applying a two-stage configuration for co-production of hydrogen and methane from maize silage in continuously stirred reactors was investigated under mesophilic conditions. The high organic loading used in the first-stage hydrogen producing reactor (e.g. load shock treatment) was effective at ensuring hydrogen-producing conditions, with no methanogenic activity observed for more than 60 days. A hydrogen yield of up to 53.8 Nl<SUB>H2</SUB>/kg volatile solid (VS) was measured in the first reactor, with a hydrogen content of 33.1%. The methane yield in the second stage reactor was 133.9 Nl<SUB>CH4</SUB>/kgVS, with a methane content of 65%. Abnormally low concentration of acetic acid and high concentrations of caproic acid were measured in the first reactor in the pH range 5–5.5, which could be explained by the presence of strains such as <I>Clostridium kluyveri</I>. Of the estimated total energy yield in the two-stage system, only 4% was from hydrogen production. The mixture of hydrogen and methane produced in the system (after carbon dioxide removal) is in the range recommended for use as vehicle fuel.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The feasibility of co-producing H<SUB>2</SUB> and CH<SUB>4</SUB> in a two-stage system using maize silage was investigated. </LI> <LI> The load-shock treatment suppressed efficiently the activity hydrogen consuming bacteria. </LI> <LI> A yield of up to 53.8 Nl<SUB>H2</SUB>/kgVS and an average hydrogen content of 33.1% were measured in the first reactor. </LI> <LI> Abnormally low concentration of acetic acid and high concentrations of caproic acid measured. </LI> <LI> The hydrogen production only contributed to 4% of the estimated total energy yield. </LI> </UL> </P>