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A comprehensive review of various processes and possible sources of hydrogen production are discussed in this paper. The various process for hydrogen production reviewed includes industrial process i.e. steam reforming, thermal cracking, partial oxidation of fossil fuels, coal gasification, electrolysis, thermochemical etc. and new emerging processes like photolysis, photo-voltaic electrolysis, photochemical, photobiological, pyrolysis, etc.
Kothari et al. (2004) studied this question.