Bio-H2 production from cheese whey and wastewater sludge in semi-continuous systems

In the present work, a lab-scale experimental campaign on dark fermentation of milk powder (used as a surrogate of cheese whey) was conducted in order to assess the bio-hydrogen production potential of cheese whey. The experiments were performed in automated semi-continuous reactors and were aimed at estimating the effect of the Organic Loading Rate (OLR) and Hydraulic Retention Time (HRT) on the H2 yield. Hydrogenogenic biomass was harvested from aerobic wastewater sludge by applying a thermal pre-treatment (105 °C, 30 min) and used as the initial inoculum. The experiments were conducted at a set-point pH of 6.5, which was automatically adjusted by the control system. In total, 20 fermentation tests were run, with HRT ranging from 4 to 20 h and OLR from 16 to 129 g TOC/(L·d). The biogas composition was evaluated by periodic gas sampling. The evolution of digestate composition was monitored through periodic measurements of volatile fatty acids, total organic carbon and soluble carbohydrates in order to derive information about the prevalent metabolic pathways and draw the carbon mass balance.