Mechanical Pretreatment of Lignocellulosic Biomass for Biofuel Production

Abstract

Lignocellulosic biomass (LB) sources which are readily available in abundance are widely considered as a potential future sustainable raw materials for biofuel production. Typically, biofuel production involved several chemical and mechanical steps consisting of pretreatment, hydrolysis, fermentation and separation. The pretreatment step is considered as one of the most vital part of the whole processing scheme due to the impact it had on the efficiency of the subsequent processing steps. In this study we reviewed the mechanical pretreatment of LB focusing mainly on the size reduction technique by grinding process. Grinding is one of the proven preliminary pretreatment techniques employed in biomass conversion to liquid biofuel. However, this technique is known to be costly due to high energy consumption. In view of this, an efficient and cost effective pretreatment technology is required in order for the biofuel to be produced at a competitive level. At the same time, the impact on environment caused by the conventional pretreatment processes can be minimized. Thus, a new combined chemical-mechanical pretreatment is considered whereby a green ionic liquid (IL) solvent is introduced.

A New Model for Environmental Assessment of the Comminution Process in the Chain of Biomass Energy Processing †

“…Grinding processes are one of the most commonly used preparatory processes for energy carriers (fossil and alternative) intended for combustion and co-combustion [1,2] and biofuel production [3][4][5]. These biomass forms may include plant-based lignocellulose waste [6,7], sewage waste [8,9], and animal-based meat processing waste [10]. To enhance the utilization of these biomass forms for direct combustion [11,12] or as a biorefinery feedstock [1,7], size reduction approaches typically constitute a significant pre-treatment step that must be undertaken [13].…”

Energy Consumption at Size Reduction of Lignocellulose Biomass for Bioenergy

“…In general, mechanical pre-treatment is considered the most important and promising preliminary stage for treating and transforming biomass into bio-fuel before passing to the next pre-treatment processes [10].…”

“…Energy consumption for biomass grinding depends on the grinding machine variables, the feeding flow and the material properties, including initial particle dimensions [14][15][16]. Practically, size reduction can be achieved through dividing or shearing with sharp knives, in which the particle geometry is altered due to impact or compression [10][11][12].…”

Lignocellulose, Cellulose and Lignin as Renewable Alternative Fuels for Direct Biomass Fuel Cells

“…By the pretreatment, the recalcitrant structure of lignocellulose is disrupted resulting in breakage of lignin sheath, degradation of hemicellulose and reduction in crystallinity and degree of polymerization of cellulose [80,81] . The degree of polymerization and crystallinity of cellulose, particle size and porosity of the LCB, which determine its solubility, can be modified by a crushing mechanism using mechanically grinding processes [82,83] . Crushing was employed to reduce the crystallinity and particle size of barley straw: barley straw was crushed into powders of different particle sizes; from 0.42 to 0.15 mm.…”