From waste biomass to chemicals and energy via microwave-assisted processes

Lignocellulosic waste material serves as a considerable renewable feedstock that could be used to replace oil refineries with biorefineries. Indeed, all biomass components can be converted into platform chemicals, bioenergy and materials. However, thermochemical and conventional catalytic conversions suffer from a number of drawbacks. Enabling technologies, such as microwave (MW) technology, can reduce process times and energy consumption, leading to improvements in product quality and yields. The remarkable advantages of MW over conventional heating, which originate from its direct dielectric interaction with biomass, are documented in this comprehensive survey. Moreover, the use of alternative solvents that interact strongly with MW in biphasic systems can circumvent the need for additional upgradation and separation steps. Finally, this review discusses some of the challenges that MW irradiation faces, including the poor dielectric properties of some substrates and issues related to its large-scale application in pyrolysis, hydrothermal conversion and catalytic routes to biofuels, materials and platform chemicals. Waste biomass may well be the benchmark feedstock for the development of a circular bioeconomic approach.