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Table 2 A selection of commonly utilised pretreatment methods

From: Pretreatment for biorefineries: a review of common methods for efficient utilisation of lignocellulosic materials

MethodActive agentMode of action
Dilute-acid pretreatmentH2SO4, H3PO4 and other strong acidsHydrolysis of hemicelluloses
Alkali pretreatmentNaOH, lime, Na2CO3 and similar alkaline compoundsExtraction of lignin
Steam pretreatment/steam explosionHigh-temperature steam; catalyst may be addedHydrolysis of hemicelluloses, fibre separation
Ionic liquidsLarge organic cation and a small inorganic anionFractionation of polymers
Deep-eutectic solventsMixtures of Lewis and Brønsted acids and basesFractionation of polymers
OrganosolvOrganic solvents, e.g. ethanol, butanol. Catalyst can be addedExtraction of lignin
Milling/grindingParticle size reductionSurface increase and improved access
Biological treatmentDegradation of the materialBrown-rot degrades hemicelluloses and cellulose
White-rot break down lignin
Soft-rot breaks down cellulose