Sustainable anaerobic technologies for biogas and biohythane production

This chapter focuses on the application of anaerobic technologies for circular bioeconomy. The realization of recycling society requires acceleration to drive the biomass flowing along with the cycles while the anaerobic approaches are generally slow. To improve the efficiency of anaerobic conversion, different types of anaerobic processes were developed, e.g., codigestion, anaerobic membrane bioreactor (AnMBR), and the recirculated two-phase anaerobic digestion (R-TPAD). In this chapter, stoichiometry, biochemical reactions, and operating parameters for typical anaerobic processes are briefly introduced. Recently, many researches are growing rapidly on codigestion. Codigestion might show synergetic, linear, and antagonistic effects depending on the combination of different biowaste. Different types of biowaste are classified by the sources and the synergetic mechanisms are specially discussed for adjusting C/N ratios, adjusting the moisture contents, supplying trace elements, and suppressing inhibitors. For AnMBR, the key parameters are discussed based on its configuration. The relations among hydraulic retention time, sludge retention time, microbial growth, and removal rates are presented. Current approaches of fouling control or membrane cleaning are compared. The basic principle of hydrogen is explained before introducing the coproduction of hydrogen and methane. The configuration and characteristics of the R-TPAD are then discussed. Recent studies are summarized to conclude that food waste is considered an indispensable component of the coproduction of hydrogen and methane. As the perspectives, the bottlenecks of codigestion, AnMBR, and R-TPAD are listed for further study to overcome.