Ultrasound-Enhanced Biogas Production from Different Substrates

Among the biofuel production processes using different substrates, the biogas generation process is one of the simplest. Compared with bioethanol or biodiesel production processes, anaerobic digestion is a process where all theorganic matter (carbohydrates, lipids and proteins) can be biologically degradedfor methane production. Biological degradations of those polymeric substrates are carried out by several enzymes during the first stage of hydrolysis. Nevertheless, due to the substrates physical state, microbial degradation is frequently hampered. Substrate pretreatment enhances the performance of anaerobic digestion by improving the bioavailability of the substrate for anaerobic digestion and thus accelerating the hydrolysis step. Appropriate methods are currently under development in order to increase accessibility of the enzymes to the materials and therefore optimise the ultimate methane production. The present chapter is dedicated to providing a review of ultrasound pretreatment applied to different substrates (lignocelullosic materials, manures, sludge and microalgae). The advantages and constraints, that ultrasound pretreatment exhibit towards biogas production, are discussed and compared with other pretreatment methods