초록
<P><B>Abstract</B></P> <P>This study compared single- and two-stage mesophilic fermentation of <I>Laminaria digitata</I>. The two-stage system comprised a hydrolysis reactor (H<SUB>1</SUB>) with a hydraulic retention time (HRT) of 4days followed by two methanogenesis reactors M<SUB>1</SUB> and M<SUB>2</SUB> with HRT of 20 and 14days respectively. The single-stage reactor (M<SUB>3</SUB>) had an HRT of 24days. Specific methane yields of 176, 234 and 221L/kg VS were obtained for M<SUB>1</SUB>, M<SUB>2</SUB> and M<SUB>3</SUB>. The methane concentration of the biogas was 22% higher for the two-stage system (58–61%) than the single-stage system (50%). Hydrolysis yielded a hydrogen yield of 26L/kg VS. The two-stage system (H<SUB>1</SUB>, M<SUB>2</SUB>) provided an overall energy yield of 8.66MJ/kg at an HRT of 18days compared to 7.89MJ/kg in the single-stage system with an HRT of 24days. Thus, the two-stage system reduced the HRT by 33% whilst improving the energy conversion by 9.8%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two-stage fermentation of <I>L. digitata</I> was compared with single-stage fermentation. </LI> <LI> Hydrolysis produced a yield of 26L H<SUB>2</SUB>/kg VS with butyric acid the dominant VFA. </LI> <LI> The two-stage system provided an optimal CH<SUB>4</SUB> yield of 234L/kg VS. </LI> <LI> The CH<SUB>4</SUB> content in the two-stage system was 22% higher than the single-stage system. </LI> <LI> The retention time of the two-stage system was 33% less than the single-stage system. </LI> </UL> </P>