초록
<P><B>Abstract</B></P> <P>This study was aimed to increase both the methane content and yield from rice straw by adding extra H<SUB>2</SUB> into a two-stage anaerobic digestion system. The results showed that the efficiency of H<SUB>2</SUB> utilization was 36.43%. Of the total amount of H<SUB>2</SUB> used, 47.3% was converted to CH<SUB>4</SUB>, thereby increasing the CH<SUB>4</SUB> content and yield by 45% and 101%, respectively. This conversion was performed at a H<SUB>2</SUB>/CO<SUB>2</SUB> ratio of 4/1 and a recycling frequency of two times a day in an up-flow reactor (UR). Due to the different ways of CH<SUB>4</SUB> production in continuously stirred tank reactor (CSTR) and UR, ethanol and acetate were produced as intermediaries, accounting for 65% and 87% of total intermediaries, respectively. Moreover, the pH values in CSTR and UR were 6.7 and 8.1, respectively. The results of the microbial community structures showed that the archaea genera of <I>Methanosaeta</I> and <I>Methanobacterium</I> were the most dominant in CSTR, whereas, <I>Methanosaeta</I> was the most dominant in UR. In terms of the bacterial community, Clostridia was the most abundant class in UR. Based on the results mentioned above, it is feasible to simultaneously improve both the CH<SUB>4</SUB> content and yield from rice straw by adding extra H<SUB>2</SUB> into the two-stage anaerobic digestion system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel method to improve the methane content and yield was studied. </LI> <LI> The methane content and yield simultaneously increased by 45% and 101%, respectively, after extra hydrogen addition. </LI> <LI> The community structures of archaea and bacteria were both investigated to analyze the effects of extra hydrogen addition. </LI> <LI> Function of energy production and conversion of genes of archaea was found. </LI> </UL> </P>