Effect of inoculum to substrate ratio (ISR) and pH on fermentative hydrogen production from cheese whey

This paper evaluates the effect of both pH and inoculum to substrate ratio (ISR) on fermentative H2 generation from cheese whey. Among the most relevant parameters influencing the anaerobic digestion process and particularly the hydrogenogenic stage, the ISR, also indicated as F/M (food to microorganism) ratio, is recognized to affect both yield and kinetics of the degradation process. In the present study we performed an investigation of the joint influence of pH and ISR on the time evolution and final yield of the hydrogenogenic process. To this aim, hydrogenogenic batch fermentation tests were conducted on a mixture of CW and sewage sludge at two different ISR values, namely 1:1 and 1:3 w/w, and operating pHs (6.5-7.5). The two parameters, along with the age of cheese whey, were found to significantly affect the performance of the process in terms of H2 production potential, process kinetics and type of metabolic products formed.