Holistic integration of biomass pretreatment and energy conversion: Pathways to sustainable biofuels

Abstract

Efficient pretreatment is the principal determinant of lignocellulosic biomass deconstruction for fuels, chemicals and materials, yet no single pretreatment technology provides universally superior performance across diverse feedstocks, product targets and sustainability metrics. This review dissects the multiscale origins of recalcitrance crystalline cellulose, hemicellulose-lignin cross-linking and lignin chemistry and links them to pretreatment objectives of deconstruction and selective fractionation. Mature thermochemical routes (steam, acid and ammonia explosions) are contrasted with emerging platforms employing designer solvents, hybrid thermo-biocatalytic sequences and process-intensified hardware. Emphasis is placed on configurations that achieve ≥95% reagent recovery while minimizing inhibitor formation. Pilot and commercial scale data indicate that pretreatment typically contributes 10–15% of total plant capital, advances such as ammonia recycling using Ammonia Fiber Expansion and Compacted Biomass with Recycled Ammonia (AFEX/COBRA), heat-integrated liquid hot-water systems and solvent-recycling organosolv processes have already reduced this burden. Techno-economic assessments show that shifting from high-severity acid pathways to mild hydrothermal or alkaline routes can reduce the greenhouse-gas emissions. Persisting bottlenecks continuous flow fouling, enzyme deactivation, solvent viscosity, lignin valorization are identified, and next generation pretreatment technologies that prioritize in-situ inhibitor mitigation and lignin-first fractionation are proposed. © 2026