Dark Fermentation and Principal Routes to Produce Hydrogen

Abstract

Interest in biohydrogen (bioH2) production from dark fermentation (DF) has increased due to green routes involving reusing by-products, wastewater, and residues from agroindustry. Moreover, bioH2 as an energy carrier of the future leads to clean combustion with the formation of a single product (water) and also releases 242 kJ mol−1 or 121 kJ g−1 energy per mass unit. As a result, it could be transformed into electrical energy using a fuel cell or an internal combustion engine. However, several studies state that the yield of bioH2 production in anaerobic reactors by dark fermentation (DF) is still low when compared to the yields of conventional hydrogen processes and technologies such as water electrolysis CH4 reform, and gasification coal, among others. Therefore, in the literature, different anaerobic technologies have been investigated, for example, changing the conventional systems to high-rate reactors and studies on the pre-treatment of inoculum, types of substrates, and genetic modifications of hydrogen-producing microorganisms. Therefore, this chapter shows the principal biochemical routes and main types of reactors used in wastewater-fed bioH2-producing systems. Finally, essential recommendations are highlighted.