Biohydrogen production from dark fermentation of cheese whey: Influence of pH G. De Gioannis a,b , M. Friargiu a , E. Massi c , A. Muntoni a,b , A. Polettini c,* , R. Pomi c , D. Spiga a a Department of Civil and Environmental Engineering and Architecture, University of Cagliari, Piazza d'Armi, 1, Cagliari, Italy b Environmental Geology and Geoengineering Institute (IGAG), National Research Council (CNR), Italy c Department of Civil and Environmental Engineering, University of Rome “La Sapienza”, Via Eudossiana, 18, Rome, Italy article info Article history: Received 2 July 2014 Received in revised form 15 September 2014 Accepted 12 October 2014 Available online xxx Keywords: Biohydrogen Fermentation Cheese whey Metabolic pathways abstract Hydrogen production from cheese whey through dark fermentation was investigated in this study in order to systematically analyse the effects of the operating pH. The effluents from pecorino cheese and mozzarella cheese production were the substrates used for the fermentation tests. Either CW only or a mixture of CW and heat-shocked activated sludge were used in mesophilic pH-controlled batch fermentation experiments. The results indicated that hydrogen production was strongly affected by multiple factors including the substrate characteristics, the addition of an inoculum as well as the pH. The process variables were found to affect to a varying extent numerous interrelated aspects of the fermentation process, including the hydrogen production potential, the type of fermen- tation pathways, as well as the process kinetics. The fermentation products varied largely with the operating conditions and mirrored the H 2 yield. Significant fermentative bio- hydrogen production was attained at pHs of 6.5e7.5, with the best performance in terms of H 2 generation potential (171.3 NL H 2 /kg TOC) being observed for CW from mozzarella cheese production, at a pH value of 6.0 with the heat-shocked inoculum. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Introduction The dairy industry, like other activities in food manufacturing, is a large contributor to the production of liquid effluents, which are often highly problematic due to both the specific quantities generated (i.e., per unit of manufactured product) and the high associated organic load [1,2]. According to European Commission statistics [3], the overall production of dairy products in 2012 in the EU-28 area accounts for 90.7 million tonnes. The main dairy products include drinking milk (35.0% of the overall production in 2012), whey (47.6%), cheese (10.2%), cream (2.8%), milk powder (2.3%), as well as butter and other yellow fat products (2.2%) [3]. In Europe, Italy is the third cheese producer after Germany and France, with an annual production of 1.2 million tonnes in 2012 [3]. * Corresponding author. Department of Civil and Environmental Engineering, University of Rome “La Sapienza”, Via Eudossiana, 18, 00184 Rome, Italy. Tel./fax: þ39 06 44585037. E-mail address: alessandra.polettini@uniroma1.it (A. Polettini). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2014) 1 e12 Please cite this article in press as: De Gioannis G, et al., Biohydrogen production from dark fermentation of cheese whey: In- fluence of pH, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/j.ijhydene.2014.10.046 http://dx.doi.org/10.1016/j.ijhydene.2014.10.046 0360-3199/Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.