초록
<P><B>Abstract</B></P> <P>Continuous H<SUB>2</SUB> and CH<SUB>4</SUB> production in a two-stage process to increase energy recovery from agave bagasse enzymatic-hydrolysate was studied. In the first stage, the effect of organic loading rate (OLR) and stirring speed on volumetric hydrogen production rate (VHPR) was evaluated in a continuous stirred tank reactor (CSTR); by controlling the homoacetogenesis with the agitation speed and maintaining an OLR of 44 g COD/L-d, it was possible to reach a VHPR of 6 L H<SUB>2</SUB>/L-d, equivalent to 1.34 kJ/g bagasse. In the second stage, the effluent from CSTR was used as substrate to feed a UASB reactor for CH<SUB>4</SUB> production. Volumetric methane production rate (VMPR) of 6.4 L CH<SUB>4</SUB>/L-d was achieved with a high OLR (20 g COD/L-d) and short hydraulic retention time (HRT, 14 h), producing 225 mL CH<SUB>4</SUB>/g-bagasse equivalent to 7.88 kJ/g bagasse. The two-stage continuous process significantly increased energy conversion efficiency (56%) compared to one-stage hydrogen production (8.2%).</P> <P><B>Highlights</B></P> <P> <UL> <LI> 56% of the energy contained in the agave bagasse was recovered by two-stage process. </LI> <LI> Energy recovery from two-stage process was 7 times higher than one-stage process. </LI> <LI> The increase of stirring speed decreased the H<SUB>2</SUB>-consumption by homoacetogenesis. </LI> <LI> In the second-stage, methane yields of 90% were obtained at high OLR and short HRT. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>