Possibility of hydrogen production during cheese whey fermentation process by different strains of psychrophilic bacteria Marcin De ˛bowski a , Ewa Korzeniewska b, *, Zofia Filipkowska b , Marcin Zieli  nski a , Rafal Kwiatkowski b a Department of Environmental Engineering, Faculty of Environmental Sciences, University of Warmia and Mazury in Olsztyn, Poland b Department of Environmental Microbiology, Faculty of Environmental Sciences, University of Warmia and Mazury in Olsztyn, Poland article info Article history: Received 7 June 2013 Received in revised form 14 November 2013 Accepted 20 November 2013 Available online 22 December 2013 Keywords: Psychrophilic bacteria Fermentation Hydrogen Whey Anaerobic respirometer abstract The aim of this study was to determine the possibility of applying psychrophilic bacteria for hydrogen production in whey biofermentation process. Experiments were conducted in 500-mL anaerobic respirometers at a temperature of 20  C. The initial organic load of fermentation tanks reached 10 g COD/L. Depending on the experimental variant, analyses were carried out for psychrophilic bacteria isolated from underground water and from demersal lake water that represented Gammaproteobacteria class e Rahnella aquatilis (9 strains) and Firmicutes phylum: Carnobacterium maltaromaticum, Trichococcus collinsii and Clostridium algidixylanolyticum. The effectiveness of biogas production was diversified and strain-specific, ranging from 126.48 to 4737.72 mL/g bacterial biomass. The highest con- centration of H 2 in biogas, ranging from 65.15% to 69.12% and effectiveness of H 2 pro- duction from 1587.47 to 3087.57 mL/g bacterial biomass, were determined for R. aquatilis strains isolated from the demersal lake water. The lowest H 2 concentration in the gaseous metabolites, i.e. 15.46% to 20.70%, was noted for bacteria of the phylum Firmicutes. Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Climate change, dwindling fossil fuel supplies, health issues resulting from fossil fuel combustion (air pollution and emission of green house gases) and economic security are the principal factors driving an intense global research effort into developing clean, renewable and CO 2 -neutral energy sources [1]. Among various biofuels, hydrogen (H 2 ) is a promising source of alternative and renewable energy for the future. Systems that can operate with hydrogen fuel are clean since they do not emit CO 2 and H 2 , and do not pollute soils or groundwater reserves. In addition, the energy content of H 2 is 122 kJ/g, a value 2.75 times higher than the one of hydrocarbon fuels [2]. The H 2 energy value (122 kJ/g) is also approximately 2.6 times greater in comparison to methane with a heating value of 55 kJ/g [3]. Today, hydrogen gas is produced by costly chemical processes since it is not available in nature. As an alternative to chemical processes, fermentative hydrogen production from renewable raw materials (biomass and * Corresponding author. Prawoche  nskiego 1 Street, 10-957 Olsztyn, Poland. Tel.: þ48 89 5233752; fax: þ48 89 5234532. E-mail addresses: ewa.korzeniewska@uwm.edu.pl, ewakmikr@uwm.edu.pl (E. Korzeniewska). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 39 (2014) 1972 e1978 0360-3199/$ e see front matter Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijhydene.2013.11.082