Challenges of Ethan
nol Production from
Lignocellulos
sic Biomass
Maha Dakar
Varieties of Ca
arbohydrates
y
Sugar
Starch
h
Cellulose/Hemicellulose
What All Plants Have
H
in Common
Cellulose
Gluco
ose
Why is it difficult to hyd
drolyze lignocellulosic
bi
biomass
into
i t sugarr to
t make
k ethanol?
th
l?
Lignocellulosic
c Biomass
•
Biomass: biological material derive
ed from living organisms. Biomass
for energy
gy related to plant
p
•
Lignocellulosic biomass: cellulose
e, hemicellulose (complex
carbohydrates) & lignin
•
Cellulose: structural material in pla
ants & most abundant biomass in
earth
•
Lignocellulose: strength, resistanc
ce to degradation
•
Cellulose & hemicellulose: polyme
p y ers of sugars,
g
potential
p
source of
fermentable sugars
•
Lignocellulosic biomass do not dirrectly go into food
Lignocellulosic Bio
omass Feedstock
• Woody Biomass
- Forest
F
t residues
id
- Wood waste
• Non-Woody
Non Woody Biomass
- Agricultural Residues:
¾St
¾Straws
(wheat,
( h t barley,
b l
riice))
¾Bagasse (sugarcane, sw
weet sorghum)
¾Stover (corn
(corn, milo)
• Organic Waste
- Animal waste
- Sewage sludge
What is Lignocellulosic Material?
lignocellulose = lignin + celllulose + hemicellulose
Cellulose
Hemicellulose
Lignin
g
Composition of Lignocellulose
1st Generation vs
s. 2nd Generation
2nd
1st
2nd
1st
How Do We Go
G From
This
Switchgrass
To
Bagasse
This?
Plants Ce
ell Walls
Plants Cell Walls:
- Middle lamella: pectin
- Primary cell wall: cellulose, hemicellulose
- Secondary cell wall: lignin
Middle lamella
Primary ce
ell wall
Secondary celll wall
Plasma membran
ne
O ti i i plant
Optimizing
l t biomass
bi
for
f efficient
ffi i t processing
i
requires
i
understanding
d
t di
of plant cell wall stru
ucture and function
Primary C
Cell Wall
Cellulose microfibril
Plasma memb
brane
Hemicellulose
Cellulose, Hemic
cellulose, Lignin
Compo
osition
iti
(C-5, C-6, uronic acid, acetyl derivatives)
(Phenolic monomers)
Very high energy content
What We Know About
A
Cellulose ?
Intrach
hain
hydrog
gen
bond
Intercha
ain
hydroge
en
bond
Intersheet
hydrogen
bond
What We Know About
A
Cellulose…
1- Cellulose fibers
2- Macrofibril
3- Microfibril
Mi
fib il
4- Chains of
Cellulose
molecules
What We Know About
A
Cellulose…
Lignin
Cellulose
Amorphous
regions
Cellulos
se consists of:
crystalline regions (blue)) & amorphous/disordered regions (red)
Crystalline
regions
Hemicellulose
Blue
e : Red
3 : 1
How An Engineer Can
C Visualize This?
=
Starch vs. Cellulose
C
Starch
Monomer:
glucose
Linkage:
α(1-4)(1-6)
Dimer sugar:
maltose
Used for:
storage
Enzyme Hydrolysis:
fast
Branch:
branched
Chains:
coiled/branched (bend)
Result:
granules
Cellulose
glucose
β(1-4)
cellobiose
structural (support)
very slow
unbranched
extended (rigid)
long fibers
Ethanol Productio
on Flowchart
Lignocellulose Process
Grain (starch) Process
Cane (Sugar) Process
Sugar
Starch Conversion
(cook/hydrolysis)
Lingocellulose
Pretreatment
Cellulose Conversion
(hydrolysis)
Fermentation
Distillation
BIOETH
HANOL
SUGAR
STARC
CH
CELLULOSE
Steps of Biomas
ss Processing
g
1
2
3
4
5
Grains
Ethanol
Milling
Cooking
Liqueffaction
SSF
Distillation
Ethanol
1-Crush
hing
g
• Size reduction: milling
g or chiipping
pp g
• Accessibility for pre-treatment step
Obstaclles
C ll ti
Collection:
-
Type/sequence of collection operattions & equipment efficiency
-
E i
Environmental
t l restrictions
t i ti
(control
(
t l erosion,
i
soil
il productivity,
d ti it carbon
b
level)
l
l)
Transportation:
-
Distance from plant & biomass amo
ount
-
Bulky in nature
-
Increase density by chipping, grind
ding or shredding
Storage:
-
Hauled to plant
-
production site
Stored at p
2- Pre-Trea
atment
The main purpose for pretreatm
ment:
-
Destroy
y lignin
g
shell p
protecting
g cellu
ulose and hemicellulose
-
Decrease crystallinity of cellulose
-
Increase porosity
-
Must break this shell for enzyme to
o
A
Amorphous
access substrate (sugar)
r
region
Pre-Treatment methods:
-
Chemical
Physical
y
Biological
Crystalline
region
Chemical Prre-Treatmet
Physical
y
Pre
e-Treatment
Biological Pre
Pre--Treatment
Treatment
fungi
Obsta
acles
• Most expensive stage in 2nd generation bioethanol
• Inhibitors such as:
- Phenolic from lignin degra
adation
- Furfural from C-5 degradattion
- HMF from C-6 degradation
n
• Corrosion
C
i problems
bl
• Acid recovery
y is expensive
p
• Material loss
• Better understanding of plan
nt cell wall structure & function
3- Hydro
y olysis
y
Polysaccharides break down in
nto monomers followed by
fermentation and distillation
Cellulose can be hydrolyzed us
sing:
-
Acid hydrolysis (Traditional method)
Enzymatic hydrolysis (The current statte-of-art method)
Acid hydrolysis advantages:
-
Faster acting reaction
Less residence time in reactor
Enzymatic hydrolysis advantag
ges:
-
Run at lower temperature
Higher conversion
Environmentally friendly
3- Hydro
olysis…
• Cellulase enzyme depolymerize c
cellulose into fermentable sugars
• Cellulase synthesized
y
by
y fungi
g an
nd bacteria work together
g
to
degrade cellulose
• Cellulosic enzyme system:
1- Endo-ß-glucanase
2 Exo-ß-glucanase
2E ß l
3- ß-glucosidase
From Cellulose
e to Glucose
Reaction Pathway:
O ti
Optimum
Parameters:
P
t
pH: 4-5
Tempt:
p 40-50C
Inhibitors: glucose, cellobiose, some minerals
Obstac
cles
•
Problems for industrial application:
1- High production cost (~40% of
o total )
2 Low yield
2-
•
Few microorganisms are capable off degrading cellulose
•
Trichoderma produces endo-ß-gluca
anase, exo-ß-glucanase & low levels of
ß-glucosidase
•
Aspergillus produces endo-ß-glucan
nase, ß-glucosidase & low levels of
exo-ß- glucanase
•
Inhibitors formation
•
Optimizing/understanding enzymes regulation and activity
•
Understanding of plant cell wall stru
ucture & function
4- Fermen
ntation
•
Convert sugars (C-5
(C 5 and or C-6)
C 6) to ethanol using microbes
•
se (C-6)
S.cerevisie for ethanol from glucos
•
S.cerevisie not able to ferment (C-5
5)
•
Some bacteria ferment C-5 & C-6 (E
E.coli & Z.mobilis)
Obsta
acles
•
Inhibitors such as:
- Phenolic from lignin deg
gradation
- Furfural from C-5 degrad
dation
- HMF from C-6 degradation
• R&D strategies:
- Robust organism to ferm
menting C-5 & C-6
- Robust organism toward
d inhibitors/temperature
• Integrate hydrolysis and ferme
entation into a single microbe
• Low conversion rates for C-5 sugars
s
• Technology to remove inhibito
ors is expensive
After All These
e Challenges In
Cellulose Hydroly
ysis What About
ysis,
Hemicelllulose?
Hemicelu
ullose
Polysaccharides that arre more complex
than sugar and less com
mplex than cellulose
The second
Th
d abundant
b d t re
enewable
bl biomass
bi
in
i
earth after cellulose
Hemicellulose vs
v Cellulose
Hemicellulose
Polysaccharides:
Monomer:
hetro-polysaccharrides
different sugar mon
nomers
(xylose, glucose, mannose, galacttose, uronic acid)
Acid
A
id Hydrolysis:
H d l i
Branch:
DP:
Structure:
f t
fast
branched
150-200
amorphous
Cellulose
homo-polysaccharides
same monomer
(glucose)
slow
l
unbranched
800-17000
crystalline
Bagasse
g
Cha
aracteristics
Brazil Strategy
S
Cane
Extraction
Bagasse
Sugar Cane
Ethanol
Ethanol
Plant
Boiler
Steam
m
Steam
Electric
city
Generator
Electricity Grid
Bagasse
e Usage
Bagasse Pulp
and Paper Mill
NaOH
Bagasse
Boiler
Digester
g
Electricity Steam Electricity
Grid
Suspended
Pulp Liquor
Pulp/paper
Bagasse
g
Usage…
g
Bagasse
Steam
Digester
H2SO4
Sludge
Boiler
Furfural
(Vapor)
Bagasse
g
Usage…
g
Bagasse
H2SO4
Digester
Wate
er
Separa
ator
C5
Neutralization
C5
C6, Lignin
Boile
er
Fermentation
CO2
Ethanol
t a o
Bagasse
g
Usage…
g
Bagasse
W
Water
Steam
H2SO4
Digester
Se
eparator
C5
Neutralization
C5
Enzymes
CO2
C6, Lignin
Fermentation
CO2
Boiler
Lignin
Ferm
mentation
Extra
Ethanol
Ethanol
t a o
Brazil Strrategy
Cane
Extraction
B
Bagas
sse
H2SO4
Digester
Sugar Juice
Ethanol
Plant
Neutrallization
C5
Ethanol
Extra
Ethanol
CO2
Fermen
ntation
C5
Separator
C6
Lignin
Boiler
Water
Where is KATZE
EN From This?
KATZEN has worked with cellullose feedstock for ethanol
ethanol,
pulp and paper & sulfite liquor over 50 years
After this long history, we say C6 will have contribution as
ethanol feedstock but limited to
o special circumstances
After this long history
history, we say Y
YES for C5