Dissertation
OPTIMIZING CHEMICAL-FREE PRETREATMENTS FOR THE BIOCONVERSION OF LIGNOCELLULOSIC BIOMASS FROM DOUGLAS-FIR (PSEUDOTSUGA MENZIESII VAR. MENZIESII) FOREST WOOD RESIDUALS
Doctor of Philosophy (PhD), Washington State University
01/2018
Handle:
https://hdl.handle.net/2376/111539
Abstract
Lignocellulosic biomass is an abundant and sustainable resource to produce biofuel as an alternative energy resource for fossil fuels. The biomass is mainly composed of cellulose, hemicellulose, and lignin. Monosaccharides can be produced from cellulose and hemicellulose through enzymatic hydrolysis and subsequent fermentation of the mono-sugars to fuels. To effectively obtain the sugar content from the biomass, suitable pretreatments are required since enzymatic hydrolysis is negatively impacted by the sturdy structure of the biomass. The external layers of the biomass act as barriers of the internal cellulose against enzymes attachment, reducing sugar yield through hydrolysis.
Thermo-mechanical pretreatment is an effective method to enhance enzymatic hydrolysis by opening the recalcitrant structures and thus increasing sugar yield from the biomass without the generation of inhibitors of hydrolysis and fermentation. Pulverization is useful to decrease the particle size of the biomass and increase the specific surface area where enzymes can attach to degrade the polymers to monomer sugars. Extrusion process improves the cellulose accessibility to enzymes by disrupting the complex rigid structures due to continuous shear stress during the process. Direct steam injection process enhances the degradation of hemicellulose and modification of lignin.
The potential of thermo-mechanical pretreatments for increasing sugar yield was explored in this research. A multi-step milling process was developed to optimize energy requirement. Extrusion process variables were studied to improve enzymatic hydrolysis. Direct steam injection process was evaluated for its ability to increase solubility of hemicellulose and the denaturation of lignin.
The combination milling strategies showed great potential with better energy efficiency. Extrusion process effectively opened the recalcitrant structures, increasing the accessibility of enzymes to the substrate. Extrusion process with high temperature resulted in recrystallization and re-agglomeration. To prevent the re-agglomeration a new screw configuration was developed. The addition of the direct steam injection process in conjunction with the extrusion processing did not result in significant increase in the sugar yields.
Thus, an effort was made to develop physical and thermal pretreatment technologies with higher energy-efficiency to increase the production of fermentable sugar from lignocellulosic biomass.
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Details
- Title
- OPTIMIZING CHEMICAL-FREE PRETREATMENTS FOR THE BIOCONVERSION OF LIGNOCELLULOSIC BIOMASS FROM DOUGLAS-FIR (PSEUDOTSUGA MENZIESII VAR. MENZIESII) FOREST WOOD RESIDUALS
- Creators
- Bon-Jae Gu
- Contributors
- Girish M Ganjyal (Advisor)Barbara A Rasco (Committee Member)Helen S Joyner (Melito) (Committee Member)Michael P Wolcott (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Food Science, School of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 221
- Identifiers
- 99900581818501842
- Language
- English
- Resource Type
- Dissertation