Mechanical Pretreatment of Lignocellulosic Biomass

Mechanical pretreatment serves as a vital first step in the valorisation of lignocellulosic biomass, facilitating downstream fractionation, saccharification and conversion into bio-based products and biofuels. Lignocellulosic biomass consists predominantly of cellulose microfibrils embedded in a matrix of hemicellulose and lignin, which together impart strong resistance to enzymatic and chemical attack. Size reduction by milling or grinding disrupts the hierarchical plant structure, increases accessible surface area, diminishes cellulose crystallinity and improves mass transfer during subsequent chemical or biological treatments. Common equipment ranges from batch-operated ball mills to continuous knife and hammer mills, each offering trade-offs between achievable particle size, energy consumption and throughput. Optimisation of mechanical pretreatment seeks to minimise specific energy demand while achieving sufficient structural disruption to reduce biomass recalcitrance, enhance bulk density for transport and storage, and tailor particle shape and porosity for compatibility with chemical reagents or microbial systems. As global interest intensifies in sustainable biorefineries and circular bioeconomies, advances in mechanical pretreatment underlie more efficient and cost-effective routes to bioethanol, biochemicals and advanced biomaterials.

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Mechanical Pretreatment of Lignocellulosic Biomass publication trend

The graph below shows the total number of articles in mechanical pretreatment of lignocellulosic biomass across all publications each year (not limited to Nature Index journals).

Technical terms

Lignocellulosic biomass: Plant material composed of cellulose, hemicellulose and lignin forming a recalcitrant matrix.

Milling: Mechanical size reduction by impact, shear and compression to produce powders or granules.

Ball mill: A tumbling chamber containing grinding media that pulverises biomass by repeated impact.

Knife/hammer mill: Continuous grinders that slice or shatter material using rotating blades or hammers.

Enzymatic hydrolysis: Biochemical cleavage of cellulose and hemicellulose into fermentable sugars.

Biomass recalcitrance: The inherent resistance of lignocellulosic structures to physical, chemical or biological degradation.

References

1. Comminution of Dry Lignocellulosic Biomass, a Review: Part I. From Fundamental Mechanisms to Milling Behaviour. Bioengineering (2018).
2. Comminution of Dry Lignocellulosic Biomass: Part II. Technologies, Improvement of Milling Performances, and Security Issues. Bioengineering (2018).
3. Effect of combined wet alkaline mechanical pretreatment on enzymatic hydrolysis of corn stover and its mechanism. Biotechnology for Biofuels and Bioproducts (2022).
4. Mechanical pretreatment of lignocellulosic biomass toward enzymatic/fermentative valorization. iScience (2022).
5. Mechanochemical and Size Reduction Machines for Biorefining. Molecules (2020).