Microwave-Assisted Pretreatment of Lignocellulosic Residues

This chapter summarizes recent advances in research on microwave-assisted pretreatment applications for biomass valorization from a biorefinery perspective. First, the fundamentals of microwaves are covered, including the mechanisms responsible for the structural modification of biomass that allow the extraction of the different components or their further transformation. The main components present in microwave equipment and the main operating parameters that can affect the performance of the process are analyzed. Subsequently, a review of the state of the art regarding the extraction of such value-added compounds by microwave (MW) as oligosaccharides, pectin, and protein is carried out, studying the influence of the operating conditions and the type of catalyst on the recovery of these compounds. The application of MW as a pretreatment of lignocellulosic biomass to alter the lignocellulosic structure and the subsequent bioconversion of carbohydrates into biofuels (bioethanol, biobutanol, biohydrogen, or biomethane) or the obtaining of other compounds (biochar, bio-oil, etc.) through the thermochemical utilization route is also reviewed. Finally, the scale-up is approached from the perspective of the power and energy required in the process, which also allows the viability of the process to be analyzed. Lastly, the challenges and prospects for the future are discussed.