Overview of Radiation-Based Technologies and Implementation of Microwave Thermochemical Technologies in the Development of Biomass-Based Biorefinery

Waste biomass valorization intends to play a crucial role in facilitating transitions toward green and sustainable development. Currently, a cascade of technologies broadly classified under thermochemical and biochemical processes are extensively studied to optimize resource efficiency and extract potentially beneficial biomolecules from multi-varied waste materials. Identification and subsequent adoption of optimal and economically viable biomass valorization methods are essential for ensuring the efficient synthesis of different classes of value-added products like biofuels, bio-oil, biochar, bioplastics, biofertilizers, biosurfactants, biomethane, biogas, etc. Currently, thermochemical processes like pyrolysis, hydrothermal liquefaction (HTL), torrefaction, and gasification are mostly used for biomass-to-biofuel technologies due to their higher efficacy and sustainability. However, instead of relying solely on conventional thermal sources to carry out biomass-to-biofuel conversion, irradiation can be employed to generate the necessary heat, resulting in a more sustainable bio-recovery. Irradiation-assisted conversion approaches offer the notable advantage of rapid and homogeneous heating while also ensuring higher product quality, thereby making them cost-effective. Additionally, single-step processes utilizing different chemical catalysts can be employed to effectively convert the products or by-products obtained from the preceding processes into chemically valuable compounds. Therefore, these valorization strategies offer direct and efficacious conversion of biomass to bio-products, adding value to the waste and thereby contributing towards a circular bio-economy. In this chapter, we will comprehensively analyze the existing irradiation-based direct conversion techniques, elucidate their underlying mechanisms, and assess their effect on diverse biomasses for enhanced production of biofuel and value-added products.