https://faculty.washington.edu/renatab/courses/PSE490/downloads/pretreatment.pdf

Features of promising technologies for pretreatment of lignocellulosic biomass.

Pretreatments to enhance the digestibility of lignocellulosic biomass

Phenolic compounds in plants and agri-industrial by-products: Antioxidant activity, occurrence, and potential uses

Lignocelluloses are often a major or sometimes the sole components of different waste streams from various industries, forestry, agriculture and municipalities. Hydrolysis of these materials is the first step for either digestion to biogas (methane) or fermentation to ethanol. However, enzymatic hydrolysis of lignocelluloses with no pretreatment is usually not so effective because of high stability of the materials to enzymatic or bacterial attacks. The present work is dedicated to reviewing the methods that have been studied for pretreatment of lignocellulosic wastes for conversion to ethanol or biogas. Effective parameters in pretreatment of lignocelluloses, such as crystallinity, accessible surface area, and protection by lignin and hemicellulose are described first. Then, several pretreatment methods are discussed and their effects on improvement in ethanol and/or biogas production are described. They include milling, irradiation, microwave, steam explosion, ammonia fiber explosion (AFEX), supercritical CO2 and its explosion, alkaline hydrolysis, liquid hot-water pretreatment, organosolv processes, wet oxidation, ozonolysis, dilute- and concentrated-acid hydrolyses, and biological pretreatments.

/pdf/pretreatment-of-lignocellulosic-wastes-to-improve-ethanol-zbwx58h962.pdf

Pretreatment of lignocellulosic wastes to improve ethanol and biogas production: a review.

Hydrothermal technologies are broadly defined as chemical and physical transformations in high-temperature (200–600 °C), high-pressure (5–40 MPa) liquid or supercritical water. This thermochemical means of reforming biomass may have energetic advantages, since, when water is heated at high pressures a phase change to steam is avoided which avoids large enthalpic energy penalties. Biological chemicals undergo a range of reactions, including dehydration and decarboxylation reactions, which are influenced by the temperature, pressure, concentration, and presence of homogeneous or heterogeneous catalysts. Several biomass hydrothermal conversion processes are in development or demonstration. Liquefaction processes are generally lower temperature (200–400 °C) reactions which produce liquid products, often called “bio-oil” or “bio-crude”. Gasification processes generally take place at higher temperatures (400–700 °C) and can produce methane or hydrogen gases in high yields.

/pdf/thermochemical-biofuel-production-in-hydrothermal-media-a-57itjyvhnt.pdf

Thermochemical biofuel production in hydrothermal media: A review of sub- and supercritical water technologies

Hydrothermal processing of lignocellulosic materials (wood or agricultural residues) causes a variety of effects including extractive removal, hemicellulose hydrolysis and alteration of the properties of both cellulose and lignin. This article reviews the chemical composition of raw materials potentially useful for hydrothermal processing as well as the results reported on the kinetics of hemicellulose hydrolysis by water treatments. The fundamentals of the mathematical modelling of hemicellulose degradation reactions by pseudohomogeneous kinetics and by severity factors are reviewed. Additional information on the effects caused by hydrothermal treatments on lignin and cellulose is also provided.

Hydrothermal processing of lignocellulosic materials

Kinetic study of the acid hydrolysis of sugar cane bagasse

Eucalyptus globulus wood samples were subjected to hydrothermal treatments under mild operational conditions (145–190 ° C, liquor to solid ratio 6–10 g g−1, reaction times up to 7.5 h). Residual xylan, xylooligosaccharides, other sugars, furfural, glucan and lignin contents were determined. Negligible effects were caused by hydrothermal treatments on both cellulose and lignin. Kinetic models were developed which describe the hydrolysis of hemicelluloses. Xylan degradation, xylooligosaccharide and xylose generation, and xylose dehydration to furfural were accurately described by models based on pseudohomogeneous, first-order kinetics with Arrhenius-type temperature dependence. These models are useful for a technical evaluation of this environmentally friendly technology.

© 1999 Society of Chemical Industry

Gil Garrote

Papers

Hydrothermal processing of lignocellulosic materials

Kinetic study of the acid hydrolysis of sugar cane bagasse

Mild autohydrolysis: an environmentally friendly technology for xylooligosaccharide production from wood

Study of the hydrolysis of sugar cane bagasse using phosphoric acid

Autohydrolysis of corncob: study of non-isothermal operation for xylooligosaccharide production