ABSTRACT
Anaerobic digestion is carried out in four stages: hydrolysis, acidogenesis, acetogenesis, and methanogenesis. Among these, hydrolysis is the initial and very important stage that breaks the complex structure into simpler molecules. Improving hydrolysis by pretreatments can increase biogas yield by increasing the performance of anaerobic digestion. Various pretreatments can be used to improve biogas yield such as mechanical, thermal, chemical, biological, and combined pretreatments (Bougrier et al., 2006; Muller et al., 1998; Weemaes et al., 1998). These treatments help to solubilize and/or reduce the size of organic compounds in order to make them more easily biodegradable (Lehne et al., 1998; Weemaes et al., 2000). This chapter presents a comprehensive review of various pretreatment methods used for improving biogas production through the anaerobic digestion process.
