Plasma technology for lignocellulosic biomass conversion toward an electrified biorefinery

Lignocellulosic biomass conversion to renewable, carbon-neutral materials, fuels, and chemicals is the cornerstone of the transition to a sustainable future bioeconomy. Green energy in the form of electricity needs to be coupled with or substitute conventional thermally driven processes to realize small-scale, economically viable and environmentally friendly biorefineries. Gas discharge plasmas enable the conversion of renewable electric energy, supplied in the form of an electric field, to chemical energy through the formation of a highly reactive environment that can induce several transformations related to agricultural waste valorization processes. Herein, we review the application of plasma technology to lignocellulosic biomass upgrade, aiming to provide the scientific background and technical challenges in this rapidly emerging research field. To bridge the gap between plasma science and biomass valorization technologies, we initially present the technical aspects of plasma reactors related to biomass processing and further discuss the advances in plasma processing for each biomass conversion technology, providing insights into the related plasma chemistry and interaction mechanisms. We first focus on the low and medium-temperature biomass conversion processes, including biomass pretreatment and delignification to promote enzyme or acid-catalyzed hydrolysis to sugars and biomass liquefaction using plasma electrolysis. Then we discuss the high and very high-temperature conversion processes, such as plasma-assisted pyrolysis and gasification to syngas and plasma application to tar removal, combustion, and vitrification. Overall, this review provides knowledge at the interface of plasma science and biomass conversion technology to promote the interaction between the individual communities, which is crucial for the further advancement of the field.