초록
<P><B>Abstract</B></P> <P>Aquatic weed, <I>Lemna minor</I> was evaluated for its potential as a feedstock for gaseous fuel production (biohythane) in an integrated strategy. Three approaches viz., acidogenic fermentation (H<SUB>AF</SUB>), electrohydrogenesis (H<SUB>MEC</SUB>) and methanogenesis (M<SUB>AD</SUB>), were evaluated in single stage as well as in different combinations of two stage (H<SUB>AF</SUB> → H<SUB>MEC</SUB>, H<SUB>AF</SUB> → M<SUB>AD</SUB>) and three stage (H<SUB>AF</SUB> → H<SUB>MEC</SUB> → M<SUB>AD</SUB>, H<SUB>AF</SUB> → M<SUB>AD</SUB> → H<SUB>MEC</SUB>) to tap the maximum feasible energy. Compared to single and two-stage operations, three-stage operation evidenced higher biogas (H<SUB>2</SUB> + CH<SUB>4</SUB>) yield with remarkable total organic carbon (TOC) reduction. Irrespective of the integration sequence, H<SUB>AF</SUB> in first stage depicted the possibility of harnessing higher energy by accumulation of volatile fatty acids (VFA) along with H<SUB>2</SUB> production. Similarly, integration of M<SUB>AD</SUB> in second stage showed the possibility of tapping higher energy rather than H<SUB>MEC</SUB> due to higher carbon loss as CO<SUB>2</SUB> coupled to more H<SUB>2</SUB> fraction in biogas in case of H<SUB>MEC</SUB>. Among, three-stage integrations, higher biogas yield and energy recovery was observed in H<SUB>AF</SUB> → M<SUB>AD</SUB> → H<SUB>MEC</SUB> (38.77 mol biogas/kg TOC<SUB>R</SUB>; 25,415 KJ/kg TOC<SUB>R</SUB>) as compared to H<SUB>AF</SUB> → H<SUB>MEC</SUB> → M<SUB>AD</SUB> (37.79 mol biogas/kg TOC<SUB>R</SUB>; 15,416 KJ/kg TOC<SUB>R</SUB>). Along similar lines, analysis of organic carbon flow exhibited significant substrate degradation in three stage integrations (72.5–81.4%) as compared to second (66.2–70%) and first stage (39.7–56.5%).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biogas (CH<SUB>4</SUB> + H<SUB>2</SUB>) production from <I>L. minor</I> by integrated approach has high potential. </LI> <LI> Three-stage integration was effective for highest energy yield (38.7 ± 1 mol/kg TOC<SUB>R</SUB>). </LI> <LI> Maximum biogas recovered resulting in recycling of 530.7 dm<SUP>3</SUP> of CO<SUB>2</SUB> per kg TOC<SUB>R</SUB>. </LI> <LI> Analysis of organic flux elucidated the effectiveness of each process on integration. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>