Hydrothermal Extraction Techniques in Lignocellulosic Biorefineries

Hydrothermal extraction, often termed autohydrolysis, employs pressurised hot water to fractionate lignocellulosic biomass into its constituent polymers—cellulose, hemicellulose and lignin—without the addition of mineral acids or alkalis. Operating typically between 160 °C and 200 °C under self-generated pressure, the process leverages the in situ formation of organic acids from acetyl groups bound to hemicellulose, which catalyse selective depolymerisation. Hemicelluloses are solubilised as oligomers and monomers, leaving a cellulose-rich solid residue amenable to enzymatic saccharification. Concurrently, partial redistribution or depolymerisation of lignin occurs, producing phenolic streams of variable molecular weight. Control of severity factors—integrating temperature, time and feedstock properties—enables the tuning of product yields and quality. Hydrothermal extraction is inherently scalable, energetically efficient through heat recovery and compatible with integrated membrane or solvent-extraction units for downstream separation. Globally, this technique underpins biorefineries converting agricultural residues, dedicated energy crops and forestry by-products into biofuels, platform chemicals and advanced materials, aligning with circular-economy imperatives and reducing reliance on fossil resources.

Research from Nature Portfolio

No recent Nature Portfolio content available.

Hydrothermal Extraction Techniques in Lignocellulosic Biorefineries publication trend

The graph below shows the total number of articles in hydrothermal extraction techniques in lignocellulosic biorefineries across all publications each year (not limited to Nature Index journals).

Technical terms

Autohydrolysis: Hydrothermal extraction in which acetyl groups released from hemicellulose catalyse further depolymerisation without added chemicals.

Hemicellulose: A heteropolysaccharide matrix in plant cell walls, readily solubilised under hot-water conditions to yield oligomeric sugars.

Lignin–Carbohydrate Complex (LCC): Covalent assemblies of lignin fragments and hemicellulose chains formed or cleaved during hydrothermal treatment, affecting fractionation efficiency.

Severity Factor: A composite measure combining temperature, time and biomass characteristics to quantify the intensity of hydrothermal treatment.

References

1. The mechanisms of hydrothermal deconstruction of lignocellulose: New insights from thermal–analytical and complementary studies. Bioresource Technology (2011).
2. Hydrothermal treatments applied to agro- and forest-industrial waste to produce high added-value compounds. BioResources (2016).
3. Effects of pH and temperature of ultrafiltration on the composition and physicochemical properties of hot-water-extracted softwood galactoglucomannans. Industrial Crops and Products (2023).
4. Formation and Identification of Lignin–Carbohydrate Complexes in Pre-hydrolysis Liquors. Biomacromolecules (2023).