Continuous dark fermentative hydrogen production by mesophilic microflora: Principles and progress

Godfrey Kyazze, Freda Hawkes, Dennis Hawkes, Richard Dinsdale, Ines Hussy

Research output: Contribution to journalArticlepeer-review


Abstract Continuous, dark fermentative hydrogen production technology using mixed microflora at mesophilic temperatures may be suitable for commercial development. Clostridial-based cultures from natural sources have been widely used, but more information on the need for heat treatment of inocula and conditions leading to germination and sporulation are required. The amount of nutrients given in the literature vary widely. Hydrogen production is reported to proceed without methane production in the reactor in the pH range 4.5–6.7, with hydraulic retention times optimally between a few hours and 3 days depending on substrate. Higher substrate concentrations should be more energy-efficient but there are product inhibition limitations, for example from unionised butyric acid. Inhibition by H2 can be reduced by stirring, sparging or extraction through membranes. Of the reactor types investigated, while granules have the best performance with soluble substrate, for particulate feedstock biofilm reactors or continuous stirred tank reactors may be most successful. A second stage is required to utilise the fermentation end products which, when cost-effective reactors are developed, may be photofermentation or microbial fuel cell technologies. Anaerobic digestion is a currently-available technology and the two-stage process is reported to give greater conversion efficiency than anaerobic digestion alone.
Original languageEnglish
Pages (from-to)172 - 184
Number of pages12
JournalInternational Journal of Hydrogen Energy
Issue number2
Publication statusPublished - 1 Feb 2007


  • hydrogen production
  • fermentation


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