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EtOH. Ethanol Production from Lignocellulosics: Sheldon Duff. Outline. Biorefinery/Biofuels Progress Feedstocks Pretreatment Fermentation of hydrolysates Process engineering Uncertainties/Current Status. nzymes (Cellulase & b-Glucosidase). Pretreatment (chemical or physical). - PowerPoint PPT Presentation
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Ethanol Production from Lignocellulosics:
Sheldon Duff
EtOH
Outline
• Biorefinery/Biofuels
• Progress– Feedstocks– Pretreatment– Fermentation of hydrolysates– Process engineering
• Uncertainties/Current Status
Bioconversion
Pretreatment(chemical or
physical)Hydrolysis Fermentation
Plant Biomass ETHANOL
nzymes (Cellulase & b-Glucosidase)
Feedstocks
Feedstocks
• Partially pretreated– Clarifier sludges– SSL (knots/PCS)– Recycled fibre
• Urban cellulosic wastes
• Agricultural residues
Paper
Pretreatment
Pretreatment
• Focus on oxygen delignification
– Clean
– Proven
Flowsheet of MediumFlowsheet of Medium--consistency consistency OO22 DelignificationDelignification
To Bleach PlantD Eo H D E D
To Bleach PlantD Eo H D E D
Brown StockStorage
Brown StockStorage
No. 2 PressNo. 2 Press
No. 1 PressNo. 1 Press
O2 BlowTank
O2 BlowTank
O2 ReactorO2 Reactor
MC MixerMC Mixer
DeckerDecker
ScreensScreensO2O2
SteamSteam
NaOHNaOH
To Bleach PlantD Eo H D E D
To Bleach PlantD Eo H D E D
Brown StockStorage
Brown StockStorage
No. 2 PressNo. 2 Press
No. 1 PressNo. 1 Press
O2 BlowTank
O2 BlowTank
O2 ReactorO2 Reactor
MC MixerMC Mixer
DeckerDecker
ScreensScreensO2O2
SteamSteam
NaOHNaOH
Mill Oxygen Delignification
0
50
100
150
200
Lignin Sugar Rate
Reduction Increase Increase
Pe
rce
nt Mill A
Mill B
Mill C
Application of OD to Recovered Fibre
• Can be used across range of substrates
• Conditions can be extended
Application of OD to Recovered Fibre
• As with all most pulping / bleaching, limit is yield
Modelling OD Effects
• Can express sugar yield as a function of initial S, K and E
• Underpredicts high substrate case due to mixing limitations
Achievements
• Dramatic improvements in yield, using known, proven technology
• Allows reduction in enzyme loading
Fermentation
Fermentation-Challenges
• Inhibitors
• Pentose fermentation
Inhibitors
Fermentation Inhibitors
• Acetic acid
• Dissolved solids
• Furfural
pH 4 pH 6
ATP
ADP
H++CH3C
O
O-
CH3C
O
OH
H+
H+
H+
Acetic acid
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 1 2 3 4 5 6 7 8 9
Gro
wth
ra
te &
yie
ld
Undissociated acetic acid (g/L)
Maximum growth rate (/hr)
Biomass yield YX/S (g/g)
Ethanol yield YP/X (g/g)
1
X
dX
dtMAX
S
KS S
YX / SmHAc
Ac 110 pH pKa
1
X
dX
dtMAX
S
KS S
YX / SmHAc
Ac 110 pH pKa
Optimization of Prehydrolysate Fermentation
Yeast extract
Corn steepliquor
Fermaid - K
Achievements
• Mechanistic understanding of inhibitors
• Modelled using maintenance energy model
• Improved fermentation (including growth on hardwood)
Xylose Fermentation
Xylose fermentation• S. cerevisiae 259ST (Dr. N
Ho, Purdue U) NWY Ho, Z Chen, and AP Brainard, 1998
• Xylose Xylulose– xylose reductase– xylitol dehydrogenase
– xylulokinase
• Xylulose fermented via pentose phosphate pathway & glycolysis
Xylose fermentation
0
10
20
30
40
50
60
0.1
1
10
0 10 20 30 40 50 60
Eth
anol (g
/L)
Yeast bio
mass (
g/L
)
Time (hours)
Modified strain (259ST)
Parent strain (259A)
90 g/L glucose45 g/L xylose
Effect of Inhibitors
• Maintenance energy has little impact on hexose metabolism
• For xylose, metabolic rate is too slow to meet maintenance demand
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.2 0.4 0.6 0.8 1 1.2T
heo
retic
al e
than
ol y
ield
(g/
0.51
g S
)
ms(g S/g X hr)
Hemicellulose Hydrolysate Fermentation
0
5
10
15
20
25
30
0 5 10 40 80 120
Su
ga
r, g
lyce
rol, x
ylit
ol, e
tha
no
l (g
/L)
Time (hours)
Glycerol
Xylose
Xylitol
Ethanol
• High [yeast] & high pH– Rapid hexose
fermentation
– Xylose fermentation
Achievements
• Xylose fermentation in SSL
– Yield on xylose increased from 0 to 80% yield
– Increased overall ethanol yield by 20 - 30%
Process Engineering
Modelling and Simulation
• Kinetics and yields from pretreatment, hydrolysis and fermentation used
• Output– M&E balances– Equipment sizing– Capital/operating
costs– Sensitivity analysis
Summary
• No full-scale cellulose-to-ethanol plants
• Any of several pretreatment technologies effective
• Enzyme costs high/uncertain ($2.40-$70/MFPU)
Summary
• C5 fermentation possible but has problems:– Slow– Metabolically challenged
• Moving toward simulation as a plant design tool
Acknowledgements
• NSERC, NRCan, P&P Companies
• Steve Helle (UNBC), David Cameron, Bob Benson
• Students: Janet Lam, Allison Murray, Kris Draude, Tony Lin, Rob Petretta, John Ruffell, John Moritz
Thank you