Second generation ethanol - Technology, a key to success

Second generation ethanol -Technology, a key to success

Guido ZacchiChemical engineering, Lund University

Sugars

Ethanol

Solid residue

Hemicellulose

Cellulose

Lignin

ResidueProcess energy

Raw material

Ethanol from Lignocellulose

36.8-

22.25.52.9

23.19.5

41.53.0

15.01.82.1

25.211.4

45.013.56.61.21.627.94.2

GlucanMannanXylanArabinanGalactanLigninOther

SalixSpruce

Raw material composition (% of DM)and theoretical ethanol yield (L/ton DM)

Ethanol from C6 425 330 280 290 307C5 57 122 200 195 186

Cornstover

Barleystraw40.5

-24.23.00.4

19.812.1

Sugarcanebagasse43.4

-24.31.50.4

22.38.1

Schematic process

SSF

Enzymatic hydrolysis

Ferment-ation

DistillationEthanolPre-

treatmentBiomass

Lignin

• Steam pretreatment – 1 or 2 stages – SO2 vs H2SO4

• SHF vs SSF - Batch vs Fed-batch

• Optimisation of SSF

• Fermentation of pentoses

• Energy integration

Steam pretreatment

Flash-vapour

Pretreatedmaterial

Computer

Steam

Biomass

Boiler

T

Reactor

Temp

Time

100 C

160 – 230 C 1–30 min

Steam pretreatment unit

Main purposes

Hydrolysis of hemicellulose

Improve the enzymatic hydrolysis of cellulose

10 litre reactor160 - 230 °CImpregnation with H2SO4 or SO2

Assessment – Ethanol production

Reactor

Biomass

Enzymatic hydrolysis (EH) of solids or SSFWashed or whole slurrySubstrate concentration (and inhibitor)Enzyme dosageType of enzymes (cellulases/hemicellulases)

Fermentation or SSFType and amount of yeastCultivated on hydrolysate or sugar solution

Makes comparison difficult

Impregnated wood chips

Steam pretreatedSO2, 210 C, 5 min

Contains potential inhibitorsExtractivesSugar degradation products e.g. Furans and acidsLignin degradation products (phenolic compounds)

StrawSteam pretreated

0.2 % H2SO4, 190 C, 10 min

0

5

10

15

20

25

30

2 5 10 2 5 10 2 5 10

Enzymatic hydrolysisPretreatment: oligoPretreatment: mono

Ove

rall

yiel

d of

xyl

ose

(g/1

00g

dry

straw

)

Pretreatment conditions

190 200 210 ºCmin

Maximum theoretical

Pretreatment of wheat straw (Xylose yield)

Linde et al Biomass and Bioenergy (in press).

Pretreatment of wheat straw (Glucose yield)

0

10

20

30

40

50

2 5 10 2 5 10 2 5 10

Enzymatic hydrolysisPretreatment

Ove

rall

yiel

d of

glu

cose

(g/1

00g

dry

straw

)

Pretreatment conditions

190 200 210 ºCmin

Maximum theoretical

Linde et al Biomass and Bioenergy (in press).

Pretreatment of wheat straw

0

0.2

0.4

0.6

0.8

1

1.2

2 5 10 2 5 10 2 5 10

HMFFurfuralAcetic acid

Yie

ld in

the

liqui

d af

ter p

retre

atm

ent

(g/1

00g

dry

stra

w)

200

Pretreatment conditions

190 210 ºCmin

(By-products)

Linde et al Biomass and Bioenergy (in press).

Improvements in SSF-stage

Recirculation of process streams

Higher ”DM-content” in SSF (fed batch)

More tolerant yeast(for increased closure of water balance)

Equipment for enzymatic hydrolysis and fermentation (SSF)

Overall yields in 2-stage pretreatmentof softwood

0102030405060708090

SSF EH

Ove

rall

yiel

d (%

of t

heor

etic

al)

SO2-caseH2SO4-case

Ethanol yield Sugar yield

5% WIS in SSF and EH

Fed-batch SSF of spruce with cutivated yeast

• 2 g/l yeast > 45 g/l ethanol

12 % FibresFed-Batch SSF

05

101520253035404550

0 50 100 150 200

Time (h)

Con

cent

ratio

ns(g

/L)

Glucose

Ethanol

Distillation: Energy demand

0

5

10

15

20

25

30

0% 1% 2% 3% 4% 5% 6% 7% 8%

Ethanol feed concentration (% [w/w])

Ene

rgy

dem

and

(MJ/

L e

than

ol)

Influence of dry matter concentration in the SSF step

(Steam pretreated spruce)

10

12

14

16

18

20

22

24

26

28

5 6 7 8 9 10 11 12 13 14 15WIS concentration in SSF (%)

Prod

uctio

n co

st (U

S$/L

et

hano

l)

0.50

0.55

0.60

0.65

0.70

0.75H

eat d

uty

(MJ/

L e

than

ol)

External process integration

Integration with heat and power plant

Combined 1st and 2nd generation ethanol production

Integration with pulp and paper

BIOREFINERY & ENERGYCOMBINE(Ethanol- Electricity-, District heating production)

585 GWh district heatingfor about 40.000 normal houses 260 GWh electricity

300.000 ton DS/1400 GWh 50.000 ton DS/250 GWh

90.000 ton DS/540 GWh

62.500 m3 ethanol / 350 GWh

Energy efficiency >70%

CO2 efficiency >90%

Steam, Water, Byproducts

(90.000 m3 ethanol / 500 GWh)

(200 GWh electricity)

Remaining challengesImproved pretreatment

Yeast that ferments all sugars in real hydrolysates

Cheaper and more effective enzymes

Increased consistency (higher DM)

Improved process integration

Prove the whole process in pilot scale

feedback to R&D

http://staff.chemeng.lth.se/~matsg/PDU/index.htm

Thanks for your attention