Biohydrogen production in an outdoor panel photobioreactor on dark fermentation effluent of molasses

Hydrogen is regarded as an ideal energy carrier if it is produced from renewable resources such as biomass. Sequential operation of dark and photofermentation allows a highly efficient production of hydrogen from biomass, as maximal conversion of the energy in the carbohydrates to hydrogen can be achieved. In this study photofermentative hydrogen production was carried out in a solar panel photobioreactor by Rhodobacter capsulatus wild type (DSM 1710) and Rhodobacter capsulatus hup− (YO3) strain on the molasses dark fermentation effluents which were obtained using an extreme thermophile Caldicellusiruptor saccharolyticus in the dark fermentation step. Continuous hydrogen production on the molasses dark fermentation effluents was achieved up to 55 days with R. capsulatus wild type and 75 days with R. capsulatus hup− in outdoor conditions during summer 2009, in Ankara Turkey. The maximum hydrogen yield obtained using R. capsulatus hup- was 78% (of the theoretical maximum) and the maximum hydrogen productivity was 0.67 mmol H2/Lc.h. The maximum hydrogen productivity and yield of the wild type strain on the molasses dark fermentation effluents were 0.50 mmol H2/Lc.h and 50%, respectively. The changes in climatic conditions, particularly daily global solar radiation, affected the hydrogen productivity and yield.