Ultrasound-Assisted Pretreatment of Sustainable Biomass

Depleting nature of the fossil fuels raises the demand for alternative clean and renewable sources such as biofuels and methods for obtaining platform chemicals from sustainable feedstock to minimize the usage of fossil reserves. Various types of sustainable biomass including different agricultural, municipal, and food wastes emerge as prominent feedstock for the production of biofuels and platform chemicals. The recalcitrant nature of biomass due to the presence of a complex lignocellulosic matrix does not allow direct and effective biomass conversion. Therefore, pretreatment to break down the complex lignocellulosic chain is an essential step for the effective utilization of biomass. Ultrasonic pretreatment presents a cost-effective and eco-friendly option enhancing the efficacy of the bioconversion process. This chapter presents an overview of different aspects of ultrasonic pretreatment in terms of its mechanism, reactor configurations, affecting parameters (processing time, frequency, solvent viscosity, sonication density, and intensity and operating temperature), environmental footprint, advantages, and limitations. The chapter also provides discussion on the combination of ultrasonic pretreatment with other processes such as alkaline, dilute acid, ionic liquid, and organic solvent-based pretreatments. It has been conclusively demonstrated that ultrasound offers promise for effective removal of lignin in an intensified manner allowing better utilization of cellulose and hemicellulose content for variety of applications.