Hydrogen has been introduced as a potential replacement for energy resource due to the depletion of fossil fuel and raising awareness about global climate change and health problems caused by the combustion of fossil fuel. One of the attractive options to produce hydrogen is through microbial fermentation which can be classified into biophotolysis, dark fermentation, photofermentation, and microbial electrolysis cell. Among these, dark fermentation and photofermentation technologies were processes that were being studied widely. One of the reasons is that organic waste could be reused as a substrate during biohydrogen production. Although the current biohydrogen yields are low, it is expected that with improvements technology and genetic engineering, the amount of generated biohydrogen could be enhanced tremendously, and provide a sustainable way of reutilizing waste as a substrate. Thus, this paper reviews the principles of photofermentation and dark fermentation by reusing various wastes as substrates. The resulting performances, limitations, as well as future prospects of hydrogen usage and hydrogen economy are also discussed. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd

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The growth of Rhodobacter sphaeroides NCIMB8253 was investigated under photoanaerobic conditions with different concentrations of palm oil mill effluent in a dual effluent growth medium. The influence of pulp and paper mill effluent as an alternative diluting agent on the bacterial growth was also investigated. During this study, it was determined that the use of pulp and paper mill effluent as a diluting agent promoted bacterial growth compared with the use of raw palm oil mill effluent medium alone. The cell growth data for all experimental sets were well-fitted to the logistic and modified Gompertz models. The results revealed that 25% (v/v) palm oil mill effluent medium with pulp and paper mill effluent as a diluting agent, namely G5 medium, can be applied as a suitable growth medium. A maximum colony-forming-units (CFU) number of 360 × 10 8 CFU/mL was achieved in G5, which was higher than that for raw palm oil mill effluent and comparable with that for water-diluted palm oil mill effluent medium. Furthermore, chemical oxygen demand level (COD total and COD soluble ) reductions were observed in all treatments.