Batch and continuous biogenic hydrogen fermentation of acid pretreated de-oiled jatropha waste (DJW) hydrolysate

Abstract

In an attempt to tailor the efficient hydrogen fermentation from hydrochloric acid-pretreated hydrolysate of de-oiled jatropha waste (DJW), batch tests were conducted to find the optimal hydrolysate concentration, temperature and pH. The optimal values were found as 10.2 g reducing sugar (RS) per L, 37 °C and 5.0, which were subsequently applied in a CSTR (continuously stirred tank reactor) using suspended biomass at various hydraulic retention times (HRTs). Peak hydrogen production rate (HPR) values were 0.86 L H₂ per L per d and 0.15 L H₂ per L per d from batch and CSTR operations, respectively. Lowering HRT (at 24 h) resulted in the wash-out of microbial biomass. Pretreatment enlarged the pore size of the unhydrolyzed biomass (UHB) from 0.6 to 3.9 mm³ g⁻¹. The structural characterization of the unhydrolyzed biomass (UHB) was assessed via SEM, XRD and FTIR and BET. BET hysteresis loops proved that increased pore size might be attributed to better accessibility of microbes for enhancing hydrogen production performances.