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Bioethanol Production: Pretreatment and Enzymatic Hydrolysis of Softwood

Tengborg, Charlotte LU (2000)
Abstract
The enzymatic hydrolysis process can be used to produce bioethanol from softwood, which are the dominating raw material in the Northern hemisphere. This thesis deals with the development of the process focusing on the pretreatment and the enzymatic hydrolysis stages.



The influence of pretreatment conditions on sugar yield, and the effect of inhibitors on the ethanol yield, were investigated for spruce and pine. The maximum yields of hemicellulose sugars and glucose were obtained under different pretreatment conditions. This indicates that two-stage pretreatment may be preferable. The added catalysts, H2SO4 and SO2, resulted in similar total sugar yields about 40 g/100 g dry raw material. However, the fermentability of... (More)
The enzymatic hydrolysis process can be used to produce bioethanol from softwood, which are the dominating raw material in the Northern hemisphere. This thesis deals with the development of the process focusing on the pretreatment and the enzymatic hydrolysis stages.



The influence of pretreatment conditions on sugar yield, and the effect of inhibitors on the ethanol yield, were investigated for spruce and pine. The maximum yields of hemicellulose sugars and glucose were obtained under different pretreatment conditions. This indicates that two-stage pretreatment may be preferable. The added catalysts, H2SO4 and SO2, resulted in similar total sugar yields about 40 g/100 g dry raw material. However, the fermentability of SO2-impregnated material was better. This pretreatment resulted in the formation of inhibitors to the subsequent process steps, e.g. sugar and lignin degradation products.



The glucose yield in the enzymatic hydrolysis stage was affected by various parameters such as enzyme loading, temperature, pH, residence time, substrate concentration, and agitation. To decrease the amount of fresh water used and thereby waste water produced, the sugar-rich pre-hydrolysate from the pretreatment step was included in the enzymatic hydrolysis of the solid fraction, resulting in a reduction in the cellulose conversion of up to 36%. Different prehydrolysate detoxification methods, such as treatment with Ca(OH)2, laccase, and fermentation using yeast, were investigated. The latter was shown to be very efficient. The amount of fresh water used can be further reduced by recycling various process streams. This was simulated experimentally in a bench-scale process. A reduction in fresh water demand of 50% was obtained without any further negative effects on either hydrolysis or fermentation. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor Saddler, John N., Department of Wood Science, University of British Columbia, Vancouver, BC, Canada
organization
publishing date
type
Thesis
publication status
published
subject
keywords
recirculation of process streams, detoxification, inhibition, hydrolysis conditions, enzymatic hydrolysis, Ethanol production, steam pretreatment, softwood, Carbochemistry, petrochemistry, fuels and explosives technology, Petrokemi, bränslen, sprängämnen
pages
82 pages
publisher
Professor Guido Zacchi, Department of Chemical Engineering 1, Lund University
defense location
Kemicentrum, Getingevägen 60, Lund, hörsal A
defense date
2000-05-26 10:15
external identifiers
  • other:ISRN: LUTKDH/(TKKA-1004)/1-82/(2000)
ISSN
1100-2778
ISBN
91-7874-069-X
language
English
LU publication?
yes
id
3d9b05b5-313e-4943-92cc-aad6792b7986 (old id 40625)
date added to LUP
2007-10-14 17:08:20
date last changed
2016-09-19 08:44:56
@phdthesis{3d9b05b5-313e-4943-92cc-aad6792b7986,
  abstract     = {The enzymatic hydrolysis process can be used to produce bioethanol from softwood, which are the dominating raw material in the Northern hemisphere. This thesis deals with the development of the process focusing on the pretreatment and the enzymatic hydrolysis stages.<br/><br>
<br/><br>
The influence of pretreatment conditions on sugar yield, and the effect of inhibitors on the ethanol yield, were investigated for spruce and pine. The maximum yields of hemicellulose sugars and glucose were obtained under different pretreatment conditions. This indicates that two-stage pretreatment may be preferable. The added catalysts, H2SO4 and SO2, resulted in similar total sugar yields about 40 g/100 g dry raw material. However, the fermentability of SO2-impregnated material was better. This pretreatment resulted in the formation of inhibitors to the subsequent process steps, e.g. sugar and lignin degradation products.<br/><br>
<br/><br>
The glucose yield in the enzymatic hydrolysis stage was affected by various parameters such as enzyme loading, temperature, pH, residence time, substrate concentration, and agitation. To decrease the amount of fresh water used and thereby waste water produced, the sugar-rich pre-hydrolysate from the pretreatment step was included in the enzymatic hydrolysis of the solid fraction, resulting in a reduction in the cellulose conversion of up to 36%. Different prehydrolysate detoxification methods, such as treatment with Ca(OH)2, laccase, and fermentation using yeast, were investigated. The latter was shown to be very efficient. The amount of fresh water used can be further reduced by recycling various process streams. This was simulated experimentally in a bench-scale process. A reduction in fresh water demand of 50% was obtained without any further negative effects on either hydrolysis or fermentation.},
  author       = {Tengborg, Charlotte},
  isbn         = {91-7874-069-X},
  issn         = {1100-2778},
  keyword      = {recirculation of process streams,detoxification,inhibition,hydrolysis conditions,enzymatic hydrolysis,Ethanol production,steam pretreatment,softwood,Carbochemistry,petrochemistry,fuels and explosives technology,Petrokemi,bränslen,sprängämnen},
  language     = {eng},
  pages        = {82},
  publisher    = {Professor Guido Zacchi, Department of Chemical Engineering 1, Lund University},
  school       = {Lund University},
  title        = {Bioethanol Production: Pretreatment and Enzymatic Hydrolysis of Softwood},
  year         = {2000},
}