A parametric response surface study of fermentative hydrogen production from cheese whey.

Batch factorial experiments were performed on cheese whey+wastewater sludge mixtures to evaluate the influence of pH and the inoculum-to-substrate ratio (ISR) on fermentative H production and build a related predictive model. ISR and pH affected H potential and rate, and the fermentation pathways. The specific H yield varied from 61 (ISR=0, pH=7.0) to 371L H/kg TOC (ISR=1.44gVS/g TOC, pH=5.5). The process duration range was 5.3 (ISR=1.44gVS/g TOC, pH=7.5) - 183h (ISR=0, pH=5.5). The metabolic products included mainly acetate and butyrate followed by ethanol, while propionate was only observed once H production had significantly decreased. The multiple metabolic products suggested that the process was governed by several fermentation pathways, presumably overlapping and mutually competing, reducing the conversion yield into H compared to that expected with clostridial fermentation.