Biomass Immobilization in Biohydrogen Production

In recent years, an enormous amount of research effort has been devoted to the study of immobilization methods and carrier materials for enhancement of the dark fermentation process. It is shown that immobilization has a complex multifactorial effect on the process of dark fermentation and opens up new technological possibilities, such as better acclimatization of hydrogen producers, a decrease in the lag phase, and an increase in biomass density, which provides greater resistance to inhibitory substances and shock loads. In addition, the use of carriers allows a wider variation of the main technological parameters, such as hydraulic retention time (HRT) and organic loading rate (OLR), and more flexible control. The chapter highlights the main immobilization methods, and their advantages and disadvantages. Parameters affecting attached growth systems, such as type of material, biofilm thickness, pH, substrate characteristics, are discussed. Particular attention is paid to materials that have a complex stimulating effect, such as conductive materials, as well as materials containing trace elements and nanoparticles that affect cell growth, metabolism, and enzyme activation. A comparative analysis of various types of biofilm reactors, their design, and operating modes is given. In conclusion, an assessment is given of the prospects for using immobilization to develop efficient, economical, and stable technologies for producing dark fermentative biohydrogen.