ABSTRACT
Numerous organic wastes could be exploited as low-cost substrates to produce hydrogen. This considerably decreases the production costs of hydrogen. Moreover, biohydrogen generation from organic wastes could accomplish multiple advantages such as managing diverse wastes, reducing pollution, and producing clean energy. Different organic wastes utilized as feedstocks (such as municipal wastes, agricultural residuals, algal biomasses, waste-activated sludges, and cellulose-based biomasses) for biological hydrogen generation are reviewed in this chapter. It is noticed that anaerobic cultures lead to low hydrolytic enzymatic activities. So, a pretreatment process is usually needed to hydrolyze organic wastes to improve the efficiency of hydrogen generation. The pretreatment procedure could break the crystalline structure of macromolecular substances and decrease their degree of polymerization. This will lead to the release of the trapped constituents via lysing of the cell walls and delignification of lignocellulosic biomasses to provide more amount of easily fermentable ingredients available to microorganisms. Physical treatment processes (such as ionizing radiation, microwave, freeze and thaw, heat, ultrasonication, grinding, and milling), chemical pretreatment methods (such as the addition of methanogenic inhibitors, oxidation by oxidizing agents, and alkaline or acid treatments), biological pretreatments (mostly involving bacterial hydrolysis and enzymatic treatments), and a combination of these diverse pretreatment processes are commonly applied. Different pretreatment processes exploited for the treatment of organic wastes as feedstocks for hydrogen generation are reported and discussed. Pretreatment is a vital process to efficiently produce hydrogen from organic wastes. This has properly been reviewed in the present chapter.
