Biohydrogen Production by Fermentation and Microbial Electrolysis Cells

This chapter is to review recent research progress on the three technologies for biohydrogen production from wastes and wastewater, i.e., dark fermentation, photo-fermentation, and microbial electrolysis cells (MEC). Among the three technologies, the development of dark fermentation is the most advanced, as evidenced by the installation of a full-scale demonstration plant, whereas the development of the other two still remains at infancy stage. For dark- and photo-fermentation, discussions are mainly focused on the development in China. Discussion of dark fermentation includes reactor types, startup strategies, and factors affecting the hydrogen production process, such as pH, partial pressure of hydrogen, hydraulic retention time, organic loading rates, sludge pretreatment, and metal toxicity, as well as pilot and full-scale production experiences. Discussion of photo-fermentation includes inoculums, light intensity, carbon and nitrogen sources, pH, metal ions, and the process of coupling with dark fermentation. Discussion of MEC includes its architecture, startup, membrane and electrode materials, anode potential, methane production, etc. Examples of producing hydrogen from MEC using fermentation effluent of molasses, lignocellulose, and cellobiose are also reviewed. Lastly, a conceptual flow diagram for a proposed biohydrogen production system treating wastes and wastewater is discussed.