Ethanol Production Using Organic Waste

Daewon Pak, Jun Cheol Lee, Jae Hyung Kim

Graduate School of Energy and EnvironmentSeoul National University of Technology

Research Background

Bioethanol in Korea

3 - 5% ethanol blends 3 - 5% ethanol blends

High oil priceHigh oil price

Reduce global warming gasReduce global warming gas

3 - 5% ethanol blends with gasoline (E3 and E5)

3 - 5% ethanol blends with gasoline (E3 and E5)

Renewable energy(5% of total energy in 2011)

Renewable energy(5% of total energy in 2011)

Low bioenergy share(5.3% of renewable energy

in ‘08)

Low bioenergy share(5.3% of renewable energy

in ‘08)

Research Background

Organic waste produced in Korea

Food waste production Food waste production (ton/day)

Separate collection (%)

Research Background

Food waste produced in Korea

ton/day

14,000

13,00013,000

12,000

11,000

10,000

2001 2002 2003 2004 2005 2006

Composition

C 46.1 ~ 48.1 %

H 6.8 ~ 7.2 %

pH 4.2~4.5

Ash 5 %

Research Background

Composition of kitchen refuse

H 6.8 ~ 7.2 %

O 32.4 ~ 36.7 %

N 3.5 ~ 4.1 %

Cl 1.9 ~ 2.2 %

Moisture content

72.99 ~ 84.96 %

Crude Protein(%) 20~25 %

Crude Fiber(%) 8~20%

Crude Lipid(%) 5~15 %

Total Sugar(%) 47~54 %

weight percentage based on dry food wastes

Research Background

Food waste as alternative substrate for ethanol production

High sugar content

High potential of ethanol production

In abundant supply (about 5 million ton per year)

Potentially promising bioresource

High potential of ethanol production

High concentration of salt ( 1.9 2.2 %)

Does not lead to resource conflict (insufficient food supply)

Materials and Methods

pHSalinity

(%)Alkalinity(mg/L)

Volatile solid(g/L)

Total solid(g/L)

SCOD(g/L)

TCOD(g/L)

4.5 – 4.8 1.5-1.8 0.1 – 0.3 130 - 138 163 - 190 62 - 98 150 - 180

Substrate

Enzyme and microorganism

Microorganisms Saccharomyces

EnzymeCarbohydrase (Asperrillus aculeatus, Viscozyme L)Glucoamylase (Asperrillus niger, Spirizyme plus FG)

Materials and Methods

Experimental set-up

Enzymatic saccharification Enzymatic saccharification &ethanol fermentation

Enzymatic saccharification of food waste using carbohydrase

control

Food wastes

Pre-treatment

Saccharification

Enzyme

Hexose

00 03 06 09 120

5

10

15

20

25

gluc

ose

conc

entr

atio

n (g

)

time (hr)

control 0.36g(about 28.8 FBGU) 1.8g(about 144 FBGU) 3.6g(about 288 FBGU) 18g(about 1440 FBGU) 36g(about 2880 FBGU)

Enzymatic saccharification of food waste using carbohydrase

DosageEnzyme Control 0.1% 0.5% 1.0% 5.0% 10.0%

Glucoamylase(Spirizyme)

0.003 0.241 0.314 0.384 0.414 0.436(Spirizyme)

0.003 0.241 0.314 0.384 0.414 0.436

Carbohydrase (Viscozyme L)

0.003 0.379 0.481 0.495 0.522 0.627

Unit: g glucose/g total solids

Effect of salt concentration on S. cerevisiae for ethanol fermentation

60

80

Eth

anol

con

cent

ratio

n (m

g/L)

control NaCl 1% NaCl 2% NaCl 3%

00 04 09 14 19 240

20

40

Eth

anol

con

cent

ratio

n (m

g/L)

Time (hr)

NaCl 3% NaCl 5% NaCl 10% NaCl 15%

Comparison between S. cerevisiae and T. Ethanolics for ethanol production

4

6

8

10

2

3

4

5

glu

cose

(g)

glucose

ethanol

Eth

anol

pro

duct

ion(

g)

(Mesophillic, yeast) S. cerevisiae T. Ethanolicus (Thermophillic, bacteria)

4

6

8

10

2

3

4

5

sucr

ose

(g)

sucrose ethanol

Eth

anol

pro

duct

ion

(g)

00 03 06 09 12 15 18 21 240

2

4

0

1

2

glu

cose

(g)

Time (hr)E

than

ol p

rodu

ctio

n(g)

Ethanol g / g-glucose

S. cerevisiae 0.51

T. ethanolicus 0.37

00 02040608 10121416 18202224 26 2830 32 343638 40 424446 48 5052540

2

4

0

1

2sucr

ose

(g)

Time (hr)

Eth

anol

pro

duct

ion

(g)

Separate enzymatic saccharification and ethanol fermentation

Saccharification

Enzyme

Food wastes Ethanol Fermentation

Microbes

Ethanol

00 12 24 36 480.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

0.4

0.6

0.8

1.0

glucose

inoculation

gluc

ose

(g/ g

TS)

time (hr)

ethanol

eth

anol

(g/

g T

S)

0.8

1.0

0.8

1.0

glucose

gluc

ose

(g/ g

TS)

ethanol

Simultaneous enzymatic saccharification and ethanol fermentation

Enzyme Microbes

00 12 240.0

0.2

0.4

0.6

0.0

0.2

0.4

0.6

gluc

ose

(g/ g

TS)

time (hr)

eth

anol

(g/g

TS)

Saccharification &Ethanol Fermentation

Food wastes

Ethanol

Comparison SHF and SSF

Ethanol production

SHF 0.43 g ethanol /g TS

SSF 0.31 g ethanol /g TS

Conclusions

• Food waste is difficult to be utilized by ethanol producing microorganism. Pretreatment using two different enzymes, carbohydrase (Aspergillus aculeatus, Viscozyme L) and glucoamylase(Aspergillus niger, Spirizyme Plus FG) were tested for saccharification of food waste. Carbohydrase was able to hydrolyze and produce glucose at 0.63 g glucose/g total solid which was higher than glucoamylase.

• The amount of carbohydrase added to food waste determines the rate of saccharification. As the amount of enzyme addition increased, the rate of saccharification was increased. At higher than amount of enzyme addition increased, the rate of saccharification was increased. At higher than 1440 FBG of enzyme activity, the saccharification rate was not increased further.

• In the separate enzymatic hydrolysis and ethanol fermentation, ethanol was produced at 0.43 g ethanol /g TS. For simultaneous saccharification and ethanol fermentation, glucose concentration increased rapidly and reached to a maximum which was less than the level obtained from the separate saccharification and ethanol fermentation. Ethanol was produced at 0.31 g ethanol/g TS which was less than the separate enzymatic hydrolysis and ethanol fermentation.