Kraft Pulping of Eucalyptus Globulus as a Pretreatment for Bioethanol Production by Simultaneous Saccharification and Fermentation

Abstract

The kraft pulping process was evaluated in this study as a pretreatment of Eucalyptus globulus for bioethanol production. Wood chips were pretreated under different pulping conditions (155°C and 165°C; 15 and 20 % alkali active AA, 15-60 min). A total of 12 pulps were obtained, with pulp yields ranging from 49 to 57%. Glucan remained in pulps were from 77% and 90%, while 50% of the hemicelluloses were solubilized. Lignin removal increased with increased severity of cooking (high active alkali charge, pretreatment time and temperature) reaching delignification over 78%. The enzymatic hydrolysis of kraft pulps with cellulase presented a rapid glucan conversion rate to glucose with values over 90%. Lignin, hemicellulose removal, as well as, cellulose polymerization degree showed an effect on the increment of enzymatic hydrolysis. The degree of crystallinity increased slightly between 1-5%, having no effect on the enzymatic hydrolysis. The simultaneous saccharification and fermentation was performed (SFS) at 10% substrate consistency with a production at 30-38 g ethanol/L. The maximum amount of ethanol that could be produced from E. globulus is 258 g ethanol/kg wood, assuming total glucose conversion into ethanol. The amounts of ethanol obtained from the different pulps varied between 168-202 g ethanol/kg wood. The ethanol yields obtained from kraft pulps varied between 65 and 78% (wood basis). The maximum ethanol yield was 78% at 155°C, 15% AA and 60 min reaction, while the yield was 74% at 165°C, 15% AA and 30 min of reaction time. Results showed that an efficient enzymatic hydrolysis at low enzyme loads could be obtained from kraft pulps employing less severe conditions than those used to produce bleachable -grade pulps.

Bioethanol Potential From High Density Short Rotation Woody Crops on Marginal Lands in Central Chile

“…Similar recovery of glucan from the solid fraction of Eucalyptus wood have been reported by Muñoz et al (2011) and Monrroy et al (2012), whereas for Acacia, the studies by Muñoz et al (2007) and Yáñez et al (2009) can be mentioned.…”

Chemical and Microstructural Changes in Eucalyptus Globulus Fibers Subjected to Four Different Pretreatments and Their Influence on the Enzymatic Hydrolysis

“…However, after homolytic disruption of the β-O-4 linkage from lignin, the formed radicals undergo rearrangement and radical coupling (condensation), resulting in a variety of phenolic subproducts derived from lignin 12 . Kraft process, currently used for pulp production, has also been reported as a pretreatment for the production of bioethanol via high efficiency delignification 13 . This is due to the presence of OH-and SH-ions in the pretreatment liquor that facilitate the formation of smaller and hydrophilic lignin molecules 14,15 .…”

Fourier transformed near infrared (FT‐NIR) spectroscopy for the estimation of parameters in pretreated lignocellulosic materials for bioethanol production

“…Samples were treated in a 1 L Parr reactor (Moline, IL, USA) loaded with 50 g of E. globulus wood chips (dry basis) and a liquor:wood ratio 5:1 (v/w). 17 During this treatment the liquor composition was either 15% or 20% of active alkali (AA) and 25% of sulfidity (both calculated on a dry wood basis and expressed as Na 2 O equivalents). The reactor was heated at 1.6 ∘ C min −1 and the experiments were performed at two different temperatures, 155 ∘ C and 165 ∘ C, with treatment times of 15, 30 and 60 min.…”