Steam Explosion of Eucalyptus grandis Sawdust for Ethanol Production within a Biorefinery Approach

Abstract

In this work, Eucalyptus grandis sawdust was subjected to steam explosion as the first step in cellulosic ethanol production within a biorefinery approach. The effect of the moisture content in the eucalypt sawdust (8 and 50%) and pretreatment process variables, such as temperature and residence time, were evaluated along with the influence of the water washing of steam-exploded solids on enzymatic hydrolysis and C6 fermentation yields. All other process streams were characterized to evaluate the recovery yield of valuable co-products. A recovery of nearly 100% glucans in the solid fraction and 60% xylans in the liquid fraction, mainly as partially acetylated oligomers, was obtained. The best enzymatic hydrolysis efficiencies (66–67%) were achieved after pretreatment at 205 °C for 10 min. The washing of pretreated sawdust with water improved the hydrolysis efficiencies and ethanol production yields by 10% compared to the unwashed pretreated solids under the same experimental condition. The highest ethanol yields were achieved after pretreatment of the sawdust with an 8% moisture content at 205 °C for 10 min, enzymatic hydrolysis at 13 wt% total solids with 25 FPU/g glucans, and fermentation with S. cerevisiae PE-2. In this case, 227 L ethanol and 40 kg total xylose (including xylo-oligomers) were obtained per ton of dry eucalypt sawdust.

Sustainability Assessment of 2G Bioethanol Production from Residual Lignocellulosic Biomass

“…These sugars' yields are quite close to those (69% for glucan and 79% for xylan conversion) previously reported [26] for the enzymatic hydrolysis of eucalyptus bark, subject to the same steam explosion pretreatment, by applying a lower enzyme dosage (3% (w/w)) to a lower solid load (17.5% (w/v)) under a batch configuration. Also, Guigou et al [27] reported efficiencies of 66% for enzymatic hydrolysis of Eucalyptus grandis sawdust, at 15% (w/v) solid load, following pretreatment by steam explosion (205 • C for 10 min). The pre-liquefaction and enzymatic hydrolysis steps were simulated in Aspen Plus with an RStoic reactor based on the reactions and respective conversions.…”

Maximizing Bioethanol Production from Eucalyptus globulus Using Steam Explosion Pretreatment: A Multifactorial Design and Fermenter Development for High Solid Loads

“…Several works using the fed-batch SSF approach have been performed using different raw materials and pretreatments, demonstrating the feasibility of this strategy, not only due to the improvement of the ethanol concentration obtained, but also due to the product yields achieved [17,23]. Guigou et al [24] published a comparison of ethanol yields and concentrations achieved using different species of Eucalyptus, with initial solid percentages ranging from 4%wt to 27%wt and concentrations between 5.4 g/L to 30.7 g/L. The highest ethanol concentration was achieved using the presaccharification and simultaneous fermentation (PSSF) strategy for Eucalyptus grandis pretreated by steam explosion and S. cerevisiae PE-2 as the fermentative microorganism.…”