Upgrading Hydrothermal Liquefaction

Biocrude Oil from Wet Biowaste into

Transportation Fuel

Wan-Ting (Grace) Chen

Agricultural and Biological Engineering

How much crude oil is consumed

by the U.S. every year?

Let’s think about

3

More food, water, and energy is needed!

4

A new paradigm –

Environment-Enhancing Energy

Bio-waste

Liquid

Solids Bio-crude oil

Clean water

Multi-cycle

nutrients &

water reuse

Wastewater

& nutrients

from Post

HTL to

algae

Algae

production

Hydrothermal

liquefaction (HTL)

Biomass

from algae

to HTL

Chen et al., Biorecource Technology 2014, 152, 130-139

0

20

40

60

80

100

120

Nomal/Dry Normal/Wet Low N/Dry Low N/Wet

En

erg

y c

on

sum

pti

on

(MJ/

kg

fu

el

pro

du

ced

)

Oil transesterificationOil ExtractionDryingAlgae culture and harvesting

Algal Biofuel Bottlenecks: Energy Balance

Drying and oil extraction are energy intensive steps

(>75% energy) (Lardon et. al, 2009; Sander & Murthy, 2010 )

5

Harvesting

Dewatering

Oil

Extraction

ConversionCulturing Drying

Wet

Extraction

(adapted from Lardon et. al, 2009)

Biodiesel Energy

Content

Slide Credit: C.T. Kuo, Y. Zhou, L. Schideman, & Y. Zhang (2015)

Hydrothermal

Liquefaction

(HTL)

Pyrolysis Gasification

Comparison of Thermochemical

Conversion (TCC) Technologies

6

Pros：

Wet feedstocks

Similar to crude oil

Higher energy density

Cons:

High

Pressure

Unstable oil

Complex

Slide Credit: C.T. Kuo, Y. Guo, & Y. Zhang (2015)

Research Question:

How much crude oil is consumed

by the U.S. every year and how to

reduce/replace it with renewable

energy?

Proposed Solutions:

Utilizing wet biowaste

Hydrothermal Liquefaction (HTL)

7

Challenge 1

Feedstock -- Would it be feasible to convert mixed-culture algal biomass grown in wastewater into biocrude oil?

– Wet biomass contains 80~98 % moisture content

– Would this bioenergy conversion technique reach a

net positive energy balance?

8

9

Hydrothermal liquefaction (HTL) of mixed-culture

algal biomass from wastewater treatment plants

Gas

Product

Post-HTL

WW

Oil

Product

Solid

Residue

Demonstrated

HTL

Feedstocks

Reactor

Reaction Temp: 260 – 320oC

Reaction Time: 0 – 1.5 hr

Animal Manure

Microalgae

Food waste

Slide Credit: Y. Zhang (2011)

Biocrude Oil Yield Optimization

10Chen et al., Biorecource Technology 2014, 152, 130-139

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

AW:SW=1:0 AW:SW=3:1 AW:SW=1:1 AW:SW=1:3 AW:SW=0:1

En

erg

y C

on

sum

pti

on

Ra

tio

(-)

Feedstock Combination Ratios (-)

50% heat recovery No heat recovery

HTL Results in a Positive Net Energy Gain

11

ECR <1 Produce

Net Positive Energy

Chen et al., Applied Energy, 128: 209-216, 2014

AW: Wastewater Algae

SW: Swine Manure

output

input

E

E ECR

Produce Enough Biofuel to Replace Fossil Fuel !

Challenge 1

Would it be feasible to convert mixed-culture algal

biomass grown in wastewater into biocrude oil?• Yes. The reaction temperature and time are determined.

• Be able to achieve a net positive energy gain

12

Challenge 2

HTL Biocrude -- How to obtain a large

quantity of biocrude oil for downstream

analysis and upgrading?

– A 1 L batch reactor can only produce 48 g of

biocrude oil (with a 40 wt.% yield)

– Development of high pressure reactor is very

challenging (e.g., feedstock pumping and clogging)

13

The first spiral PFR that can processes

6 ton of wet biowaste per day

14

Produce Enough Biofuel for the U.S. annual consumption!

Goal 1

Would it be feasible to convert mixed-culture algal

biomass grown in wastewater into biocrude oil?• Yes. The reaction temperature and time is optimized.

• Be able to achieve a net positive energy gain

15

Goal 2

How to obtain a large quantity of biocrude oil

for further analysis and upgrading?• Developed an up-scaled continuous reactor

• Address plugging issues

16

Challenge 3

Upgrading the HTL Biocrude --Since the

composition of the biocrude oil is so

complex, how to properly upgrade it?

– High ash content in the mixed-culture algae harvestedfrom wastewater (AW) negatively affect the bio-crude oil quality

– How ash content interacts with volatile components in the feedstock under the HTL processes remains unknown

Pretreat Mixed-culture Algal Biomass from Wastewater

Treatment Plants

Harvest algae

Wash with tap water (1 h) Garbage entrained

with algae

Pulverize

Screen

Ultrasonic Centrifuge Centrifuge

+ Ultrasonic

Test Ash

Content

Scanning Electric

Microscope (SEM)

Thermogravimetric

Analysis (TGA)17

Pretreatment condition Ash content Weight percentage after

centrifugation

Pulverized 27.6 ± 0.07 % N/A

S-2 28.6 ± 1.9 % 100 %

C-1 Upper 32.5 ± 1.2 % 26.4 ± 4.27 %

Middle 18.6 ± 0.8 % 29.0 ± 0.73 %

C-2 Upper 36.7 ± 3.1 % 24.5 ± 2.15 %

Middle 21.8 ± 0.8 % 27.0 ± 0.50 %

C-3 Upper 34.1 ± 3.5 % 24.4 ± 0.18 %

Middle 21.0 ± 0.04 % 33.0 ± 7.35 %

C-4 Upper 34.4 ± 1.7 % 26.7 ± 0.63 %

Middle 19.2 ± 1.9 % 33.5 ± 1.38 %

18

Ash Contents of Pretreated Algae

Reduced by 7-10 wt.%

C1 & C2: Centrifuge at 3000 rpm with 15 min and 25 min, respectively;

C3 & C4: Centrifuge at 3000 rpm with 15 min and 25 min, respectively;

S2: Before Centrifuge.

25.0%

35.0%

45.0%

55.0%

65.0%

75.0%

85.0%

95.0%

105.0%

0 100 200 300 400 500 600 700 800

Wei

ght

Los

s(%

)

Temperate(ºC)

Pulverize

Screen#2

C-1-upper

C-1-middle

Ultrasonic

C-upper+U-0.5h

C-upper+U-1h

C-middle+U-0.5h

C-middle+U-1h

Decomposition Kinetics Analysis of

Pretreated Algal Biomass

Stage.2

Stage.1

Stage.3

19

)1( Xkdt

dX

)exp(RT

EAk a

Sample Pretreatment method Ea (kJ/ mol)

Ea1 Ea2

Algae from a

waste-water

treatment plant

Pulverize 5.60 50.2

S-2 5.63 47.6

C-1-upper 3.92 48.4

C-1-midddle 2.91 47.5

U 5.75 48.0

C+U-1-upper 2.49 37.0

C+U-2-upper 2.23 35.9

C+U-1-middle 2.53 41.1

C+U-2-middle 2.56 40.2

Chlorellaa N/A 6.32 44.4

Apparent Activation Energy (Ea) of Algae

Decreased after Pretreatments of

Centrifugation Plus Ultrasonication

a Adopted from (Gai et al., 2013), which was operated at the same condition under TGA.20

Sample Pretreatment

Method

Ea (kJ/ mol) Biocrude Oil Yields

from HTL (%)b

Higher Heating

Value (MJ/kg)

Ea1 Ea2

Algae from

a waste-

water

treatment

plant

Pulverize 5.60 50.2 30.9 ± 1.87 % 28.2

S-2 5.63 47.6 29.2 ± 3.35% 28.4

C-1-midddle 2.91 47.5 30.6 ± 4.32 % 29.9

U 5.75 48.0 35.4 ± 5.13 % 30.9

C+U-2-middle 2.56 40.2 55.3 ± 1.54 % 32.4

Chlorellaa N/A 6.32 44.4 39.6 ± 0.79 %c 37.8 c

Biocrude Oil Yield of Pretreated Algae

Significantly Improved by 20-25 wt.%

a Adopted from (Gai et al., 2013), which was operated at the same condition under TGA.b HTL processes were conducted with 25 % total solids content of feedstocks at reaction temperature of 300 °C with reaction time of 1 hour c Adopted from (Gai et al., 2014), which was operated at the same condition under HTL.

21

Produce Enough Biofuel for the U.S. annual consumption!

Goal 1

Would it be feasible to convert mixed-culture algal

biomass grown in wastewater into biocrude oil?• Yes. The reaction temperature and time is optimized.

• Be able to achieve a net positive energy gain

22

Goal 2

How to obtain a large quantity of biocrude oil

for further analysis and upgrading?• Developed an up-scaled continuous reactor

• Address plugging issues

How to properly upgrade HTL Biocrude Oil?• Remove excessive amounts of ash contents

• Understand the role of ash content under HTL

Goal 3

23

– The composition of biocrude oil would be different from feedstock to feedstock

– Simple separation methods such as extraction was not able to fractionate biocrude oil into transportation fuel

– Catalytic upgrading of biocrude oil with hydroprocessinghas not been effective to improve the fuel properties

Pretreatment of

Biowaste

Solids

Continuous Hydrothermal

liquefaction (producing 5

gallons biocrude oil /day)

Biocrude

oil

Liquid

Algae

production

Sun light CO2

Clean

water

Phenols

Fatty Acids

Hydrocarbon

s

Nitrogen-doped

Carbonaceous

Material

Aviation

BiofuelBiodiesel Functional MaterialsEngine Test 24

Chen et al., Nature Energy, in preparation

70% of the Distillates of Biocrude Oil

are in the Diesel Range

25

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

0.0 100.0 200.0 300.0

Wei

gh

t of

Bio

cru

de

( w

t.%

)

Temperature (°C)

Test 1

Test 2

Test 3

Test 4

Test 5

Diesel Range:

200-338 ° C*

*According to ASTM-D7467 and D975

Chen et al., Nature Energy, in preparation

Distillates from FPW-derived Biocrude

Contains Alkanes and Fatty Acids

26Chen et al., Nature Energy, in preparation

A B C D E F G H

10

20

30

40

50

60

70

80

90

100

% o

f Tota

l Rela

tive P

eak A

reas

(%)

Distillate Fractions

Hydrocarbons Cyclic Hydrocarbons Fatty Acids Derivatives

Fatty Nitriles N-Heterocyclic cmpds.

Phenols Amino Acids

27

Acidity of Different FPW-Distillates

Chen et al., Nature Energy, in preparation 27

203.4208.5

137.9

71.3

26.6

8.15 1.68 1.000%

10%

20%

30%

40%

50%

60%

70%

80%

0

50

100

150

200

250

A B C D E F G H

Yie

ld (

wt.

%)

Ac

idit

y (

mg

KO

H/g

s

am

ple

)

Distillation Fraction (-)

Acidity

Distillation Yield

ASTM: 0.3

28

Mild Upgrading

Esterification for FPW (food processing waste)-

derived distillates to reduce their acidity

Neutralization with NaOH for SW (Swine Manure)-derived distillates to reduce gum contents that caused by phenolic compounds

Chen et al., Nature Energy, in preparation

Energy Consumption Ratio and Process Severity

(Ro) of Different Upgrading Approaches

Distillation of HTL biocrude oil is competitive to other available

upgrading strategies, without the consumption of H229Chen et al., Nature Energy, in preparation

0

2

4

6

8

10

12

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Zeolite (425 C)

SCW (400 C)

HDT (400 C)

DL of SW DL of FPW

DL of SP

Lo

g R

o

En

erg

y C

on

su

mp

tio

n R

ati

o

Different Upgrading Strategies (-)

Severity 50% heat recovery No heat recovery

Fuel Spec

Property

Bio-diesel

(B5-20)

Diesel HTL 10 HTL20

Viscosity

(mm2/s)a

3.241f 3.746 3.737 3.050

Acidity

(mgKOH/g)b

<0.3d <0.3d 0.10 0.29

Gross Heat of

Cumbustion

(MJ/kg) c

40-41f 46.0 44.7 44.2

Cetane Number

(min)

40>d 40e 44.2 43.6

Lubricity (µm) <520d <460g-

520e

364 324

Oxidation

Stability (hr)

6 >d N/A 48> 48>

aMeasured by ASTM D445; bMeasured by ASTM D664; cMeasured by bomb

Calorimeter (ASTM D4809);d ASTM D7467;eASTM D975;fLin et al., Fuel, 2012gEngine Manufacture Association recommendation

Fuel Specification of Drop-in Biodiesel Prepared

with Upgraded HTL Distillates meets ASTM

High Cetane

number refers to

low ignition delay

before

combustion

Lower lubricity

than biodiesel

implies to a better

ability to reduce

wear and friction

Superior

oxidation stability

for long-term

storage

30

Chen et al., Nature Energy, in preparation

Fuel Specification and Engine Test of Drop-in

Biodiesel Prepared with Upgraded HTL Distillates

Competitive

power output of

HTL drop-in

fuel to

petroleum

diesel

Lower pollutant

emissions of

CO, CO2, NOx,

and unburned

hydrocarbons

31Chen et al., Nature Energy, in preparation

Engine Testa HTL10 HTL20 Diesel/

Biodiesel

Power Output (kW) 3.68-4.26 3.67-4.24 3.41-4.26

CO emission (ppm) 0.09-0.31 0.07-0.32 0.12-0.34

CO2 emission (ppm) 8.70-10.2 8.06-9.80 8.76-10.5

NOx emission (ppm) 606-1304 551-1456 540-1320

Unburnthydrocarbons

(ppm)

14-26 16-28 14-32

Soot (FSN) 0.01-0.12 0.06-0.13 0.01-0.11

aOperated at 1200-2000 rpm with injection timing of 0-12° BTDC under

medium loading of fuel (20 mg/stroke);b filter smoke number (FSN)

32

HTL 10 and 20 Leads to a Higher Power

Output in Diesel Engine

HTL 10 can achieve a higher power output than regular

diesel at 0-4 CA BTDC and 2000rpm.

HTL 20 can lead to a superior power output to diesel at 4-8

CA BTDC and 1500 rpm.

1.2 1.4 1.6 1.8 2.00

2

4

6

8

10

12

Inje

cti

on

Tim

ing

(C

A B

TD

C)

Enigne Speed (1000*RPM)

0.972

0.986

0.999

1.01

1.03

1.04

1.05

1.07

1.08

Power-HTL10 (%)

1.2 1.4 1.6 1.8 2.00

2

4

6

8

10

12

Inje

cti

on

Tim

ing

(C

A B

TD

C)

Enigne Speed (1000*RPM)

0.955

0.963

0.971

0.980

0.988

0.996

1.00

1.01

1.02

Power-HTL20 (%)

33

HTL 10 and 20 Leads to a lower NOx

emission in Diesel Engine

HTL 10 can achieve a 6% lower NOx emission than diesel

at 1500rpm for all tested crank angle, due to lower EGT.

HTL 20 can lead to a 13% lower NOx emission than diesel

at 1500-2000 rpm for all tested crank angel.

1.2 1.4 1.6 1.8 2.00

2

4

6

8

10

12

Inje

cti

on

Tim

ing

(C

A B

TD

C)

Enigne Speed (1000*RPM)

0.940

0.963

0.986

1.01

1.03

1.05

1.08

1.10

1.12

NOx-HTL10 (%)

1.2 1.4 1.6 1.8 2.00

2

4

6

8

10

12

Inje

cti

on

Tim

ing

(C

A B

TD

C)

Enigne Speed (1000*RPM)

0.870

0.901

0.933

0.964

0.995

1.03

1.06

1.09

1.12

NOx-HTL20 (%)

Produce Enough Biofuel for the U.S. annual consumption!

Goal 1

Would it be feasible to convert mixed-culture algal

biomass grown in wastewater into biocrude oil?• Yes. The reaction temperature and time is optimized.

• Be able to achieve a net positive energy gain

34

Goal 2

How to obtain a large quantity of biocrude oil

for further analysis and upgrading?• Developed an up-scaled continuous reactor

• Address plugging issues

Goal 3

How to properly upgrade HTL Biocrude Oil?• Fractionate Biocrude oil by distillation

• Mildly upgrading HTL distillates (esterification)

• Fuel Spec and Diesel Engine Test is conducted

How to properly upgrade HTL Biocrude Oil?• Remove excessive amounts of ash contents

• Understand the role of ash content under HTL

35

More food, water, and energy is needed!

US consumed 1.1 billion tons of crude oil annually

Relevant Publication List 10. Wan-Ting Chen, Yuanhui Zhang, Timothy Lee, Zhenwei Wu, B.K. Sharma, Chia-Fon Lee, Lance Schideman,

“Renewable Transportation Biofuel Production Converted from Wet Biowaste via Hydrothermal Liquefaction,” Nature Energy, in preparation, Mar, 2017

9. Wan-Ting Chen, Wanyi Qian, Yuanhui Zhang, Zachary Mazur, Karalyn Scheppe, Chih-Ting Kuo, “Hydrothermal Liquefaction of High-Ash Algal Biomass: the Effect of Ash Contents in HTL Reactions,” Algal Research, submitted, Dec 2016.

8. Peng Zhang, Yuanhui Zhang, Wan-Ting Chen, Lance Schideman, B.K. Sharma, “ Hydrothermal Liquefaction of Diatom Skeletonema costatum and the Effect of Frustules on Biocrude Oil Production,” International Journal of Agricultural and Biological Engineering, accepted, Dec, 2016

7. Wan-Ting Chen, Liyin Tang, Wanyi Qian, Karalyn Scheppe, Ken Nair, Zhenwei Wu, Chao Gai, Peng Zhang, YuanhuiZhang, “Extract Nitrogen-Containing Compounds in Biocrude Oil Converted from Wet Biowaste via Hydrothermal Liquefaction,” ACS Sustainable Chemistry & Engineering, 4 (4): 2182-2190, 2016.

6. Chao Gai, Yuanhui Zhang, Wan-Ting Chen, Peng Zhang, Yuping Dong, “An Investigation of Reaction Pathways of Hydrothermal Liquefaction Using Chlorella pyrenoidosa and Spirulina platensis,” Energy Conversion & Management, 96:330-339, 2015.

5. Giovana Tommaso, Wan-Ting Chen, Peng Li, Lance Schideman, Yuanhui Zhang, “Chemical Characterization and Anaerobic Biodegradability of Aqueous Products Generated from Hydrothermal Liquefaction of Mixed-Culture Algae from Wastewater Treatment System,” Bioresource Technology, 178:139-146, 2015.

4. Wan-Ting Chen, Junchao Ma, Yuanhui Zhang, Gai Chao, Wanyi Qian, “Physical Pretreatments of Wastewater Algae to Reduce Ash Content and Improve Thermal Decomposition Characteristics,” Bioresource Technology, 169: 816-820, 2014.

3. Wan-Ting Chen, Yuanhui Zhang, Jixiang Zhang, Lance Schideman, Guo Yu, Peng Zhang, Mitchell Minarick, “Co-liquefaction of Swine Manure and Mixed-culture Algal Biomass from a Wastewater Treatment System to Produce Bio-crude Oil,” Applied Energy, 128: 209-216, 2014.

2. Wan-Ting Chen, Yuanhui Zhang, Jixiang Zhang, Peng Zhang, Guo Yu, Lance Schideman, Mitchell Minarick, “Hydrothermal Liquefaction of Mixed-culture Algal Biomass from Wastewater Treatment System into Bio-crude Oil,” Bioresource Technology, 152: 130-139, 2014.

1. Jixiang Zhang, Wan-Ting Chen, Peng Zhang, Yuanhui Zhang, Zhongyang Luo, “Hydrothermal Liquefaction of Chlorella pyrenoidosa in Sub- and Supercritical Ethanol with Heterogeneous Catalysts,” Bioresource Technology, 133: 389-397, 2013.

36

Produce Enough Biofuel for the U.S. annual consumption!

Would it be feasible to convert mixed-culture algal biomass

grown in wastewater into biocrude oil?• Yes. The reaction temperature and time is optimized.

• Be able to achieve a net positive energy gain

37

How to obtain a large quantity of biocrude oil for

further analysis and upgrading?• Developed an up-scaled continuous reactor

• Address plugging issues

How to properly upgrade HTL Biocrude Oil?• Fractionate Biocrude oil by distillation

• Mildly upgrading HTL distillates (esterification)

• Fuel Spec and Diesel Engine Test is conducted

How to properly upgrade HTL Biocrude Oil?• Remove excessive amounts of ash contents

• Understand the role of ash content under HTL

Q&A

Learn more at:

wchen58@illinois.eduhttps://Sites.google.com/view/gracechen

Thank you

38

Acknowledgments• All the members in Prof. Yuanhui Zhang’s Group

• T. Lee, K. Nithyanandan and Prof. Chia-Fon Lee

• K.C. Tsao and Prof. Hong Yang in Dept. of CHBE

• Dr. Lance Schideman & Dr. B.K. Sharma in ISTC

• Prof. Alan Hansen in Dept. of ABE (Fuel Spec Test)

• Dave and Tom Burtons in Snapshot Energy LLC

• Dedicated Support from my family and Dr. Mei-Hsiu Lai

ReferencesW.-T. Chen, Y. Zhang, J. Zhang, L. Schideman, G. Yu, P. Zhang and M. Minarick, Applied energy, 2014, 128, 209-216.

http://www.e2-energy.illinois.edu/

B. J. He, Y. Zhang, T. L. Funk, G. L. Riskowski and Y. Yin, Transactions of the ASAE, 2000, 43, 1827-1833.

D. Cheng, L. Wang, A. Shahbazi, S. Xiu and B. Zhang, Fuel, 2014, 130, 251-256.

www.IATA.org (International Air Transportation ssociation)

ASTM standards

MIT open course provided by Chemical Engineering

Carbon, 48(13), 3778-3787.

Zhou, D., Zhang, L., Zhang, S., Fu, H., Chen, J. 2010. Hydrothermal liquefaction of macroalgae Enteromorpha prolifera to bio-oil. Energy & Fuels, 24(7), 4054-

4061.

Zhou, D., Zhang, S., Fu, H., Chen, J. 2012. Liquefaction of macroalgae Enteromorpha prolifera in sub-/supercritical alcohols: direct production of ester

compounds. Energy & Fuels, 26(4), 2342-2351.

Zhou, N., Huo, M., Wu, H., Nithyanandan, K., Chia-fon, F.L., Wang, Q. 2014. Low temperature spray combustion of acetone–butanol–ethanol (ABE) and diesel

blends. Applied Energy, 117, 104-115.

Zhou, Y., Schideman, L., Yu, G., Zhang, Y. 2013. A synergistic combination of algal wastewater treatment and hydrothermal biofuel production maximized by

nutrient and carbon recycling. Energy & Environmental Science, 6(12), 3765-3779.

Zhang, L., Champagne, P., Xu, C. 2011. Bio-crude production from secondary pulp/paper-mill sludge and waste newspaper via co-liquefaction in hot-

compressed water. Energy, 36(4), 2142-2150.

Zhang, P. 2014. Characterization of biofuel from diatoms via hydrothermal liquefaction. in: Agricultural & Biological Engineering, Vol. Master of Science,

University of Illinois at Urbana-Champaign. Urbana.

Zhang, Y. 2010. Hydrothermal liquefaction to convert biomass into crude oil. in: Biofuels from Agricultural Wastes and Byproducts, Wiley-Blackwell. Hoboken,

NJ, pp. 201-232.

Zhao, C., Camaioni, D.M., Lercher, J.A. 2012. Selective catalytic hydroalkylation and deoxygenation of substituted phenols to bicycloalkanes. Journal of

Catalysis, 288, 92-103.

Zhao, C., Kou, Y., Lemonidou, A.A., Li, X., Lercher, J.A. 2009. Highly Selective Catalytic Conversion of Phenolic Bio‐Oil to Alkanes. Angewandte Chemie,

121(22), 4047-4050.

Zhao, C., Kou, Y., Lemonidou, A.A., Li, X., Lercher, J.A. 2010a. Hydrodeoxygenation of bio-derived phenols to hydrocarbons using RANEY® Ni and Nafion/SiO

2 catalysts. Chemical Communications, 46(3), 412-414.

Zhao, L., Baccile, N., Gross, S., Zhang, Y., Wei, W., Sun, Y., Antonietti, M., Titirici, M.-M. 2010b. Sustainable nitrogen-doped carbonaceous materials from

biomass derivatives. Carbon, 48(13), 3778-3787.

39

Questions?..... Learn more at: e2-energy.illinois.edu/

Department of Agricultural & Biological Engineering University of Illinois at Urbana-Champaign

Photo Credit:

Chih-Ting Kuo