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

Table 2 A selection of commonly utilised pretreatment methods

Method	Active agent	Mode of action
Dilute-acid pretreatment	H₂SO₄, H₃PO₄ and other strong acids	Hydrolysis of hemicelluloses
Alkali pretreatment	NaOH, lime, Na₂CO₃ and similar alkaline compounds	Extraction of lignin
Steam pretreatment/steam explosion	High-temperature steam; catalyst may be added	Hydrolysis of hemicelluloses, fibre separation
Ionic liquids	Large organic cation and a small inorganic anion	Fractionation of polymers
Deep-eutectic solvents	Mixtures of Lewis and Brønsted acids and bases	Fractionation of polymers
Organosolv	Organic solvents, e.g. ethanol, butanol. Catalyst can be added	Extraction of lignin
Milling/grinding	Particle size reduction	Surface increase and improved access
Biological treatment	Degradation of the material	Brown-rot degrades hemicelluloses and cellulose White-rot break down lignin Soft-rot breaks down cellulose

ISSN: 2731-3654