Mechanistic insights into thermal degradation of lignocellulosic biomass components for bioenergy and biofuel: A review

• This study reviewed thermodegradation of lignocellulosic components. • Hemicellulose decomposes earliest at 150-180°C, producing higher volatiles. • Cellulose degrades sharply at 320-400°C, producing volatiles with 10-30% char. • Lignin shows broad degradation from 250-600°C, yielding the highest solid char. • Lignin-derived char exhibits higher HHV values of 23-26 MJ·kg-1. Lignocellulosic biomass is a pivotal renewable resource for sustainable energy systems, offering significant potential to reduce reliance on fossil fuels and mitigate greenhouse gas emissions. Its thermochemical conversion leads to advanced bioenergy and combustion technologies; however, the intrinsic complexity of biomass, arising from the distinct physicochemical properties of individual lignocellulosic components, poses substantial challenges for process optimization. This review critically examines the thermal degradation behavior of cellulose, hemicelluloses, and lignin, emphasizing their reaction mechanisms, thermal stability, and product formation pathways under key thermochemical processes, including torrefaction, pyrolysis, gasification, and direct combustion. Particular attention is given to the influence of molecular structure, bond dissociation energies, and functional group chemistry on devolatilization, char formation, and gaseous emissions. Advanced analytical techniques, such as thermogravimetric analysis coupled with spectroscopic and chromatographic methods, are discussed in relation to their role in elucidating degradation pathways and validating kinetic models. The comparative assessment highlights how component-specific behavior governs energy yield, syngas composition, tar formation, and combustion reactivity. Finally, current challenges related to feedstock heterogeneity, scale-up, and process integration are identified, along with future research directions to improve predictive modeling and enable component-informed reactor design. By integrating mechanistic understanding across multiple thermochemical pathways, this review establishes a basis for advancing more efficient, cleaner, and adaptable bioenergy and combustion technologies.