Biochemical conversion: Anaerobic Digestion

This chapter describes the anaerobic digestion process for production of methane-containing biogas from various feedstocks. Anaerobic digestion is a biotechnological process by which a complex organic feedstock is first converted into a range of simpler water-soluble organic compounds that are subsequently converted into methane-containing biogas. To enable rational bioreactor engineering, it is crucial to describe the anaerobic digestion process in terms of reaction stoichiometry and kinetics. The chapter describes a strongly simplified version of the anaerobic digestion model that focuses on the most common rate-limiting steps in the process. For anaerobic digestion of particulate substrates like those considered here, there are two potentially rate-limiting steps in the overall process and one boundary condition that needs to be fulfilled. Wet anaerobic digestion is implemented for dry substrates by recycling of the water after filtering of the digestate.