Hydrogen gas (called hydrogen here for simplicity) has been
envisaged as the clean and renewable fuel for future. Hydrogen
can be produced by a number of processes, such as water
electrolysis, steam reforming, coal gasification, and biological processes
(Azwar et al., 2014). Among these technologies, biological
conversion of renewable resources (e.g., organic wastes) to hydrogen
has received a considerable attention in recent years, as sustainability,
energy security, and climate change become
important issues to be addressed