Valorization of crude glycerol and eggshell biowaste as media components for hydrogen production: A scale-up study using co-culture system.

The properties of eggshells (EGS) as neutralizing and immobilizing agent were investigated for hydrogen (H2 ) production using crude glycerol (CG) by co-culture system. Eggshells of different sizes and concentrations were used during batch and repeated-batch fermentation. For batch and repeated-batch fermentation, the maximum H2 production (36.53±0.53 and 41.16±0.95mmol/L, respectively) was obtained with the EGS size of 33μm<x5 <75μm. Hydrogen production increased with the decreasing size of EGS. Eggshells maintained the fermentation pH (6.00-6.30) and provided immobilization support as confirmed by scanning electron microscopy. As media components, the EGS concentration of 0.25% (w/v) was found to be optimum for maximum H2 production (31.66±0.55mmol/L) and the production profile was comparable to H2 production (32.07±0.92mmol/L) obtained with all media components. In scale-up study with semi-continuous bioreactor (7.5L), almost 1.5-fold increase (in comparison to mono-culture) i.e. 312.12mmol-H2 /L-of medium with 86.65% glycerol utilization was obtained.