Study of the Application of Alkaline Extrusion to the Pretreatment of Eucalyptus Biomass as First Step in a Bioethanol Production Process

Abstract

Eucalyptus biomass was studied as a feedstock for sugars release using an alkaline extrusion plus a neutralization-based pretreatment. This approach would be a first step in a bioconversion process aimed at obtaining fuel bioethanol from eucalyptus biomass. The best operation conditions of extrusion (screw speed, temperature, liquid to solid ratio and NaOH amount) that lead to an effective destructuration of lignocellulose and enhanced sugar release were investigated. Two process configurations, with and without filtration inside the extruder, were tested. In the case without filtration, washed and not washed extrudates were compared. It was demonstrated that filtration step was convenient to remove inorganic salts resulting from neutralization and to promote the mechanical effect of extrusion, but limitations in the machine used in the work prevented testing of temperatures above 100 °C using this configuration. In the no filtration strategy, a temperature of 150 °C allowed attaining the highest glucan and xylan conversion rates by enzymatic hydrolysis of extruded biomass, almost 40% and 75%, respectively, of the maximum yield that could be attained if all carbohydrates contained in raw eucalyptus were converted to sugars. Some of the mechanisms and individual effects underlying alkaline extrusion of eucalyptus were figured out in this work, providing guidelines for a successful pretreatment design that needs to be further studied.

Feasibility Assessment of a Bioethanol Plant in the Northern Netherlands

“…Several studies investigated the effect of pretreatment on bioethanol production efficiency. However, it is not clear which technique favors maximal glucose and xylose release from the carbohydrate polymers, as well as is cost-efficient, as a financial analysis is required [54][55][56][57][58][59][60][61].…”

Energy Efficiency of Comminution and Extrusion of Maize Substrates Subjected to Methane Fermentation

“…The fact that the energy balance of comminuted maize straw silage was worse than that of maize silage may have been caused by the poor susceptibility of maize straw to comminution (the share of the largest fraction >1.25 mm was up to 45.6%), which resulted in a lower increase in the active surface. On the other hand, the positive energy balance of the maize straw extruded at 175 • C may have been caused by the formation of products (simple sugars) [42] of thermal hydrolysis as the extrusion temperature process increased (the content of cellulose decreased by more than 5% and the content of hemicellulose decreased by over 4%). Such an increase may also have been caused by the lack or a minimal amount of anaerobic digestion inhibitors in extrudates, thus enabling the acclimation of methanogenic bacteria (the lignin content decreased by only 0.75%).…”

A Two-Step Ferric Chloride and Dilute Alkaline Pretreatment for Enhancing Enzymatic Hydrolysis and Fermentable Sugar Recovery from Miscanthus sinensis

“…Step Note: 1 The total soluble sugar yield through the whole process was calculated on the basis of raw stalk. SS: soluble sugars; RS: raw stalk; PS: pretreated stalk; PTS: pretreatment stage; EH: enzymatic hydrolysis.…”

“…Energy, environmental pollution, public health and food safety are the most important issues for global sustainable development, and production of renewable energy from different organic wastes is attracting increasing attention [1][2][3][4][5][6][7][8]. Lignocellulosic biomass (e.g., corn stalk, wheat straw, and rice straw), which is a sustainable and renewable energy source with reduced net CO 2 emission, has been widely investigated as substrates for ethanol and biogas fermentation [8,9].…”