Solid waste biotreatment. Ethanol production from lignocellulosic materials. Lecture 4

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BIOPROCESS TECHNOLOGY
Dr. TERESA FERNANDEZ ALDAMA
“SAMARA UNIVERSITY”
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LECTURE No. 4. SOLID WASTE
BIOTREATMENT/Ethanol production
from lignocellulosic materials (I)
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LCM are promissing feedstock for ethanol
production without affecting the food
sector
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Objective
To describe components of lignocellulosic
materials, their characteristics and how to
prepare them for ethanol production.
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Outline
Lignocellulosic materials (LCM) for ethanol
production
LCM. Composition
Characteristics of cellulose, hemicellulose and
lignin
Hydrolysis of cellulose and hemicellulose
Pretreatment methods
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Environmental importance of the use of
fuel ethanol
Ethanol
CO2
Decreasing of gas
emissions
No net production of
CO2
It does not contribute
to the greenhouse
effect
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Lignocellulosic materials
Forest residues
Agricultural and food industry residues
Municipal solid wastes (Recycled paper)
Energy crops
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Sugarcane bagasse
Cassava stems
Rice husks
Peanut shells
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Alternative for production of ethanol
Second generation
biofuel
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Composition of LCM
Cellulose
35-50%
β-glucose
O, Ca, K, Si, etc.
D-glucose
D-galactose
Hemicellulose D-mannose
20-35%
D-xylose
L-arabinose
Lignin
10-25%
Ash
0-2%
Phenolic
compounds
Extractives
Phenolic
compounds
1-5%resin
and Wood
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Cellulose
Cellobiose
Glucose
Hemicellulose
Hexoses:
D-mannose
D-glucose
D-galactose
Lignin
Pentoses:
D-xylose
L-arabinose
Phenylpropane units
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Molasses
Inoculum
propagation
Fermentation
Distillation
Ethanol
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Ethanol production from LCM
Ethanol
Hydrolysis
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Ethanol production from LCM
Cellulose
Hemicellulose
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Hydrolysis of cellulose
Acid hydrolysis
With concentrated acids
With diluted acids
Enzymatic hydrolysis
With cellulases and hemicellulases
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Acid hydrolysis
H2SO4 at high concentration:
☺
☺
☺
High sugar yields
Use of low temperature
Few by-products
☹ Equipment corrosion
☹ Need of expensive drying the raw material
☹ High acid recovery costs
☹ Incrustation (Neutralization)
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Acid hydrolysis
Dilute-acid Hydrolysis
☺ Lower requirement of acid (compared with
the previous one)
☹ High temperatures
☹ Sugar degradation
☹ Formation of by-products
☹ Equipment corrosion
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Enzymatic hydrolysis
Bacterial cellulases (Clostridium and Bacillus)
Fungal cellulases (Trichoderma, Aspergillus,
Penicillium)
Endoglucanase (EC 3.2.1.4)
Cellobiohydrolase (EC 3.2.1.91)
-glicosidase (EC 3.2.1.21)
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Enzymatic hydrolysis
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Hydrolysis of cellulose
Cellulose
Cellobiose
Glucose
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Hydrolysis of hemicellulose
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Enzymatic hydrolysis
☺ High conversion yield
90-100% for cellulose
70-75% for hemicelluloses
☺ No sugar degradation
☹ High cost of enzymes
☹ Slow process
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Enzymatic hydrolysis
The cellulases must be able to:
Reach and adsorb onto cellulose
surface (Accessibility)
Find, or make, reactive ends of
cellulose chain (Reactivity)
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Enzymatic hydrolysis
☹ Low accessibility (Association with
hemicelluloses and lignin)
☹ Low reactivity (High degree of crystallinity)
PRETREATMENT
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Pretreatment of LCM
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Sugarcane juice
or molasses
Substrate
Inoculum
propagation
Fermentation
Distillation
Ethanol
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Flowchart for ethanol production from LCM
Lignocellulosic Materials
Pretreatment
Hydrolysis
Physical
Biological
Chemical
Physico-chemical
Fermentation
Distillation
Ethanol
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Pretreatment of LCM
Physical methods (milling and irradiation)
Increase in specific surface and size of pore.
Decrease degree of
cristallinity of cellulose.
polymerization
☹ High consumption of energy
☹ Low efficiency
☹ High cost
and
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Pretreatment of LCM
Biological methods: decrease the degree of
polymerization and crystallinity of cellulose.
☹ Slow
☹ High cost
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Pretreatment of LCM
Chemical and physico-chemical methods
Delignification
Reduction of degree of polymerization and
crystallinity
Degradation of hemicellulose
Increase of the surface area and porosity
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Pretreatment of LCM
Chemical and physico-chemical methods
Steam explosion
Wet oxidation
Dilute-acid prehydrolysis
Autohydrolysis
Liquid hot water
Ammonia fiber explosion
☺ Efficient
☺ Low cost
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Steam explosion
High pressure
saturated Steam
Pretreatment
reactor
Raw material
T = 205 0C
t = 10 min.
P = 12 bar
Flash vapor
☺ Good yields in short time
☺ Minimal use of chemicals
☹ Inhibitor formation
Cyclone
Boiler
Pretreated
material
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Wet oxidation
Raw material + Water
Pretreatment reactor
T = 195 0C
t = 15 min.
Pretreated
material
O2 (or air)
☺ Low formation of inhibitors
☺ Good results at alkaline condictions
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Control questions
1. Describe the composition of lignocellulosic materials.
2. What characteristics distinguish cellulose from
hemicelluloses?
3. Mention the hydrolysis methods that can be used to obtain
fermentable sugars. Explain one of them.
4. Why is necessary to pretreat lignocellulosic materials before
their use for ethanol production.
5. Describe one pretreatment that can be used before
hydrolysis of lignocellulosic materials. Specify the most
important goals to achieve an efficient pretreatment?
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Suggested literature
- Harmsen P., Huijgen W., Bermudez L., Bakker R. Literature
review of physical and chemical pretreatment processes for
lignocellulosic biomass. Biosynergy, September 2010, Report
1184. ISBN 978-90-8585-757-0.
- Zoghlami A., Paës G. Lignocellulosic Biomass:
Understanding Recalcitrance and Predicting Hydrolysis.
Frontiers in Chemistry, 2019, Volume 7, Article 874.
- Galbe M., Zacchi G. A review of the production of ethanol
from softwood. Appl Microbiol Biotechnol, 2002, 59:618–628.
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THANK YOU FOR YOUR
ATTENTION!
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