Biomass Refining CAFI Auburn University Soaking in Aqueous Ammonia (SAA) for Pretreatment of Corn Stover Tae Hyun Kim and Y. Y. Lee Department of Chemical

Biomass Refining CAFI Auburn

University

Soaking in Aqueous Ammonia (SAA) for Pretreatment of

Corn Stover

Tae Hyun Kim and Y. Y. LeeTae Hyun Kim and Y. Y. Lee

Department of Chemical Engineering

Auburn University

AIChE 2004 Annual MeetingAustin, TX. Nov, 2004


University

Research objective

Overall objective

To develop a economically viable and environmentally benign process for the pretreatment of biomass.

Factors of interestsEnergy and capital costs Enzymatic digestibilityFermentability


University

Corn stover composition

ArabinanMannan

Galactan

Protein Acetyl groupUronic acid

others

Ash

Lignin

Xylan

Glucan

Note. NREL supplied corn stover to CAFI members (source: BioMass AgriProducts, Harlan IA).

Corn stover was washed and dried in small commercial operation, knife milled to pass ¼ inch round screen

36.1%

21.4%17.2%

7.1%


University

Ammonia as a pretreatment reagent

• Highly selective and effective in delignifying the biomass

• Easy to recover and reuse because of high volatility.

• One of the most widely used commodity chemicals (one-fourth the cost of sulfuric acid).

• Non-polluting and non-corrosive chemical.


University

ARP (Ammonia Recycle Percolation)

• A pretreatment method based on aqueous ammonia, which uses a flow-through column reactor (percolation).

• Lignin is believed to be a major hindrance to enzymatic hydrolysis.

• Efficient delignification; it gives a high and adjustable degree of delignification (70-85%).

• It has been proven to be effective for pretreatment of biomass; digestibility is 90% for glucan and 78% for xylan with 15 FPU/g-glucan.


University

Corn stover

ARP laboratory reactor and reaction conditions

Data Acquisition SystemOven &

Reactor

Receiver Tank

NH3 Feeding

N2 Back Pressure

Aq. NH3

50 ml of 15 wt% Aqueous NH3 (1

reactor void volume)

Reactor (15 g of Corn Stover) Reactor Volume:70.9 cm3

Reactor Void Volume: 45.0 cm3

Flow through column reactor

Flow rate; 5 ml/minReaction temp; 170°C


University

Problems in ARP

1. High capital cost (High pressure equipment).

2. High-energy cost (high temperature).

3. Half of xylan is removed (xylan recovery is difficult in the downstream processing)

• SAA (soaking in aqueous ammonia) at room temperature was proposed.


University

Features of SAA at room temperature

Reaction conditions• Room temperature/ Atmospheric pressure• 30 wt.% of aqueous ammonia• Solid-to-liquid ratio: 1:8• Treatment time: 10 days

Features• Batch Process / no agitation• Mild reaction conditions• Low equipment cost • Lignin is removed/Xylan is retained• Simple downstream process

SAA apparatus

Corn stover


University

Effect of soaking time on compositional change in SAA at room temperature-

treated corn stover

17.217.817.818.121.4

4.68.8

7.6 5.7 5.617.2

0

5

10

15

20

25

30

35

40

0 10 20 30 40 50 60

Reaction Time [days]

Co

mp

osi

tio

n [

% o

f o

rig

inal

corn

sto

ver]

Note. S:L ratio=1:12, reaction temp.=22–24ºC (R.T.), 29.5 wt.% NH3. All sugar content based on the oven-dry untreated biomass

Glucan

Xylan

Lignin


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Digestibility vs. soaking time

with 15 FPU/g-glucan

0102030405060708090

100

0 24 48 72 96

Time [h]

En

zym

atic D

ige

stib

ility

[%]

Untreated

1 d

4 d

10 d

30 d

60 d

Note. S:L ratio=1:12, 1-60 days treat.; reaction temp.=R.T., 29.5 wt.% NH3.

4 days

10~60 days

Untreated

86% with 10 days-treated corn stover

1 days


University

Problems in SAA at room temperature

1. Longer reaction time (about 10 days). -> Large capital cost (huge reactor) 2. High liquid input (S:L=1:8~1:10). -> Large operating cost

• SAA at moderate temperature was proposed.


University

Features of SAA at moderate temperature

Reaction conditions• Temperature: 60 °C• 15 wt.% of Aqueous Ammonia• S:L Ratio: 1:6• Treatment Time: 12 hours• Atmospheric pressure

Features• Batch process /no agitation• Lignin is removed/Xylan is retained• Simple downstream process


University

Effect of temperature, S/L Ratio, and reaction time on Lignin removal

50.1

67.2

77.2

40

50

60

70

80

30 40 50 60 70 80 90 100

Temperature [°C]

De

lign

ifica

tion

[%

]

15 wt.% of NH3; 24 h reaction time; 1:10 of solid-to-liquid ratio.

30

40

50

60

70

80

1:2 1:4 1:6 1:8Solid-to-Liquid ratio [-]

Del

igni

ficat

ion

[%

]

15 wt.% of NH3; 60°C of reaction temperature

24 h

12 h

6 h

Solid-to-liquid ratioAnd Reaction timeReaction temperature


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Xylan content in SAA-treated corn stover

17.916.517.2

10

12

14

16

18

20

30 40 50 60 70 80 90 100

Temperature [°C]

Xyl

an [%

of o

rigin

al c

orn

stov

er]

10

12

14

16

18

20

1:2 1:4 1:6 1:8

Solid-to-liquid Ratio [-]

Xyl

an

[%

of

ori

gin

al c

orn

sto

ver]

24 h

12 h6 h

15 wt.% of NH3; 24 h reaction time; 1:10 of solid-to-liquid ratio.

15 wt.% of NH3; 60°C of reaction temperature

Solid-to-liquid ratioAnd Reaction time

Reaction temperature


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Selectivity of delignification over xylan removal upon various temperature and

ammonia concentration

40 60 90

15 w

t.%

30 w

t.%2.1

2.3

2.5

2.7

2.9

3.1

Selectivity [-]

Temperature [C]

15 wt.%

30 wt.%

ratereduction mass ,

mwhere

m

mySelectivit

xylan

lignin


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Enzymatic Digestibility of Glucan and Xylan in SAA-treated Corn Stover

(a) Digestibility of glucan

0

20

40

60

80

100

0 24 48 72 96

Time [h]

En

zym

atic

dig

esti

bili

ty [

%]

SAA-treated a-Cellulose Untreated

(b) Digestibility of xylan

0

20

40

60

80

100

0 24 48 72 96

Time [h]

En

zym

atic

dig

esti

bili

ty [

%]

SAA-treated Untreated

85% at 72 h 78% at 72 h

-Cellulose

Untreated Untreated

Treatment conditions: 60°C, 15 wt.% NH3, 1:6 of S/L, and 12 h


University

Simultaneous saccharification and fermentation (SSF)

o Microorganism : S. cerevisiae, D5A

o Substrate : SAA-treated corn stover

o Enzyme loadings: 15 FPU of Spezyme CP + 30 CBU of Novozyme 188 per gram-glucan

o YP medium (1% of Yeast extract, 2% of Peptone)

o Anaerobic condition


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SSF of “SAA-treated” corn stover using D5A yeast

3% w/v glucan loading

0

10

20

30

40

50

60

70

80

90

100

0 24 48 72 96 120 144 168 192

Time [h]

Eth

anol Y

ield

[%

of

Theoritic

al]

or

Glu

cose

Conc.

[g/L

]

Ethanol yield, SAA-treated corn stover

Ethanol yield, a-Cellulose

Glucose, SAA-

treated C.S. Glucose, -cellulose

73% of ethanol yield is much lower than 85% of the glucan

digestibility.


University

Xylose accumulation in SSF of “SAA-treated” corn stover using D5A

3% w/v of glucan loading

0

1

2

3

4

5

6

7

8

0 24 48 72 96 120 144 168Time [h]

Sug

ar c

once

ntra

tion

[g/L

] Xylose

Glucose


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Xylose inhibition on enzyme activity in the cellulose hydrolysis

Time [h]

0 24 48 72 96

En

zym

atic

dig

est

ibili

ty [%

]

0

10

20

30

40

50

60

70

80

90

100

-cellulose-cellulose + xylose

-cellulose only

-cellulose + 3% xylose

3 wt.% of glucan loading

Lower ethanol yield (73%) than the digestibility (85%) with SAA treated sample is due to inhibition by xylose.


University

SSCF test using “recombinant E.coli ATCC ® 55124 (KO11)”

o LB medium (0.5% of Yeast extract, 1% of Tryptone)

o Substrate : 12 h SAA at moderate temp.-treated corn stover (1:6 of S:L ratio).

o Enzyme loadings: 15 FPU of Spezyme CP + 30 CBU of Novozyme 188 per gram-glucan

o SAA-treated corn stover has about 52% glucan and 26% xylan.

o 3% w/v glucan loading: (30g glucan+15g xylan)/L


University

SSCF of “SAA-Treated” Corn Stover by Recombinant E.coli ATCC® 55124 (KO11)


0

2

4

6

8

10

12

14

16

18

20

22

0 24 48 72 96 120 144

Time [h]

Co

nc

en

tra

tio

n [

g/L

]Ethanol yield, SAA-treated corn stoverTheoretical

max. based on

glucan

Ethanol yield,-cellulose

Glucose, SAA-treated C.S.

Xylose, SAA-treated C.S.

113% of theoretical maximum based on

glucan only

- Utilization of xylose contributes to increase of ethanol yield from 73% to 113%.


University

Sugar concentration in SSCF of “SAA-treated” corn stover by recombinant E.coli ATCC® 55124


0

0.5

1

1.5

2

2.5

3

0 24 48 72 96 120 144Time [h]

Co

nce

ntr

atio

n [

g/L

]

Xylose

Glucose

*Recombinant E.coli consumed the glucose and xylose simultaneously.


University

Process options based on aqueous ammonia

ARP (ammonia recycle percolation)

2004

SAA at room temp.

SAA at moderate temp.

170°C, 2.3 MPa- High capital & energy cost Remove 50% of xylan

2003

Room temp. & Atm. pressure Retain >85% of xylan in solid 30% ammonia, 1:8~10 of S:L Pretreatment time : 10 days

60 °C & Atm. pressure Retain >85% of xylan in solid 15% ammonia, 1:6 of S:L Pretreatment time: 12 h

To reduce the pretreatment time to <1 day


University

Biomass-to-ethanol process using SAA-SSCF

Lignin & xylooligomer (10-15%)

Glucan +>85%Xyla

n

SAA- SSCF (Biomass-to-Ethanol)

Lignocellulosic

biomass

Fermentation

SSCF

Pretreatment

Enzymatic hydrolysis

Lignocellulosic

biomass

Fermentation

SSCF

Xylooligomer and lignin-rich

hydrolysate

Conditioning

Lignin + Sugar

degradation products

Pretreatment

Enzymatic hydrolysis

Lignin Separatio

n

Pentose sugar

Glucan

Conventional SSCF (Biomass-to-Ethanol)


University

02468

10121416182022

0 24 48 72 96 120 144

Time [h]

Eth

an

ol co

ncen

trati

on

[g

/L]

Acid-treated solid only

Acid-treated solid +Hydrolysate

SAA-treated

Solid HydrolysateGlucan Xylan

Total Sugar LoadingGlucan Xylan

3.0 g1.38 g -None-None-- 4.38 g

ARP-treated

3.0 g 0.78 g4.78 g

0 g 1.0 gAcid-treated

3.0 g 0.12 g 5.69 g0.37 g

2.2 g

02468

10121416182022

0 24 48 72 96 120 144

Time [h]

Eth

an

ol co

ncen

trati

on

[g

/L]

ARP-treated solid +Hydrolysate

ARP-treated solid only

Sugar Loadings in SSCF ReactorSugar Loadings in SSCF Reactor

Toxicity of hydrolysates in SSCF: various treated solids + hydrolysates (soluble sugars)


University

Summary• Soaking in Aqueous Ammonia (SAA) is a simple and

technically feasible pretreatment method for corn stover. • SAA retains 85% of xylan in the solid.• SSF of SAA-treated corn stover faces significant

inhibition due to xylose accumulation in the reactor.• In SSCF of SAA-treated corn stover using recombinant

E.coli (KO11), glucan and xylan are concurrently converted.

• Ethanol yield from SSCF is 113% of theoretical maximum on the basis of glucan alone, or 73% on the basis of combined glucan and xylan in untreated corn stover.

• Leaving hemicellulose in solids is a desirable pretreatment strategy.


University

Acknowledgements US Department of Agriculture Initiative for Future

Agricultural and Food Systems Program, Contract 00-52104-9663

US Department of Energy Office of the Biomass Program, Contract DE-FG36-04GO14017

Genencor International Our team from Dartmouth College; Michigan

State, Purdue, and Texas A&M Universities; the University of British Columbia; and the National Renewable Energy Laboratory


University

Questions?

Corn stover

Corn stover

Wood chip

Bagasse

Rice straw

Sawdust

Documents

Biomass Refining CAFI Auburn University Soaking in Aqueous Ammonia (SAA) for Pretreatment of Corn Stover Tae Hyun Kim and Y. Y. Lee Department of Chemical