Source of the photo
http://en.wikipedia.org/wiki/File:Photo_pathway_draft.png
Author of the description
GK
Biohydrogen is produced biologically, most commonly by algae, bacteria and archaea. Biohydrogen is a potential biofuel obtainable from both cultivation and from waste organic materials.
The attached document gives detailed information on hydrogen fermentation.
Source of description
http://www.fao.org/docrep/w7241e/w7241e0g.htm
http://www.doiserbia.nb.rs/img/doi/1451-9372/2008/1451-93720802057D.pdf
http://en.wikipedia.org/wiki/Biohydrogen
Attached pdf