Parametric analysis of fermentative hydrogen production from cheese whey

Cheese whey (CW) is one of the most abundant by-products of cheese manufacturing, as about 9.0 kg of CW are generated for each kg of cheese produced. Due to its origin, it is a high strength wastewater characterized by high chemical and biochemical oxygen demand. Thus, identification of proper strategies for CW management is a challenging topic in view of reducing both treatment cost and environmental impacts. Among the different options, anaerobic digestion can be regarded as one of the most promising, being able to reduce the organic load of CW while harversting its energy content. Recently, an increasing attention has been paid to dark fermentation of CW, as according to theoretical calculations, 8 mol H2 can be produced per mole of degraded lactose in quite short digestion time. H2 may be used as fuel or in fuel cells, whilst the effluent may be fed to a second-stage conventional anaerobic digester for CH4 production. In the present study, the effect of pH conditions and inoculum addition on H2 production from CW was investigated under continuously stirred batch conditions by designing the experiments according to the principles of a factorial design. According to this approach, the set-point of the pH values of the system and the amount of inoculum added to CW was varied over four values. As inoculum, the aerobic sludge from a wastewater treatment plant was used, after heat-shocking at 110°C for 30 minutes so as to harvest the hydrogenogenic biomass. Process performance was evaluated in terms of H2 production and substrate conversion efficiency, by three process indicators: 1) amount and composition of the produced biogas evolution of the metabolic pathways, 2) evolution of substrate degradation, expressed as the removal total organic carbon (TOC) and carbohydrates.