Advancements in Microwave-assisted Technologies for the Production of Value-added Products from Lignocellulosic Waste Biomass

The global concerns toward sustainable development have created many paths for the employment of lignocellulosic waste feedstock for producing energy, fuel, chemicals as well as many other value-added substances. Lignocellulosic materials are comprised of the most profuse renewable carbon source. These materials can be either agro-wastes (e.g., rice husk, rice straw, wheat straw, sugarcane bagasse, and corncob) or forest (e.g., aspen and pine wood) residues. The demand for value-added products like furfural, furfuryl alcohol, and formic acid is huge in the global market. The efforts to produce these compounds from lignocellulosic waste biomass are dependent upon various techniques that can alter the structure of this base material. Microwaves signify a competent source of energy to acquire value-added chemicals and fuel from lignocellulosic biomass. Process intensification and energy saving become feasible with microwave-driven green chemical techniques. Volumetric and selective dielectric heating are some unique properties of microwaves that can be effectively exploited for hydrolyzing biopolymers and the further conversion to highly expensive fine chemicals. Microwave heating is a better option in comparison to conventional modes of heating due to its higher reaction rates (speed), throughput, yield, and purity. Uniformity of heat dispersion and less requirement of energy are other merits associated with microwave-assisted processes. Microwave-based pretreatment is a promising approach for pretreating lignocellulosic waste biomass that mediates physical, chemical, or biological reactions. This chapter focuses on some of these characteristics of microwaves and surveys the usage of microwaves as a separate pretreatment method in addition to a co-pretreatment procedure to augment the execution of further thermochemical pretreatments. It also highlights recent advancements in microwave applications for the generation of value-added chemicals, the challenges associated, and future research guidelines to resolve them.