electricity and hydrogen production using microbial fuel cell-based

1

Electricity and hydrogen production using microbial fuel cell-based technologies

Bruce E. LoganPenn State University

EngineeringEnvironmental

Institute

2

Ethanol versus H2 from Glucose • Glucose: ∆Hc= 2808 kJ/mol

• Ethanol– Produce 2 ethanol per glucose by fermentation– 2×∆Hc= 2× 1367 kJ/mol => ∆Hc= 2734 kJ/mol

• Hydrogen– Produce up to 12 H2 per glucose– 12×∆Hc = 12× 286 kJ/mol => ∆Hc = 3430 kJ/mol

• DOE – 10-12 mol-H2/mol-glucose needed to make biological H2

production feasible (9.6 mol H2= ∆Hc for 2 ethanol from glucose)

3

Current sources of H2 Production

Electrolysis4%

Coal18%

Natural Gas48%

Heavy oils and naphtha

30%

4

Time (h)0 50 100 150 200 250

Bio

gas

(mL)

0

50

100

150

200

250

300

MolassesPotato StarchGlucoseSucroseLactate

H2 can be biologically produced from bacterial fermentation of sugars

Biogas:

- 60% H2

- 40% CO2

Source: Logan, VanGinkel & Oh Environ. Sci. Technol. (2002)

5

H2 can be produced by cellulose fermentation

0.00

0.50

1.00

1.50

2.00

2.50

3.00

C.acetobutylicum C.cellulolyticum C.cellobioparum C.celerecrescens C.populeti C.phytofermentans

CellobioseMN301Avicel

H2 Yield (mol-H2/mol hexose)

Source: Ren et al., J. Appl. Microbiol. (2007)

6

The “fermentation barrier” limits H2 yields

C6H12O6 + 2 H2O 4 H2+ 2 C2H4O2 + 2 CO2

C6H12O6 2 H2 + C4H8O2 + 2 CO2

Maximum: 12 mol-H2/mol-hexose

Maximum of 4 mol/mol (2 mol/mol in practice)Maximum of 4 mol/mol (2 mol/mol in practice)

How can we recover the remaining 8 to 10 mol/mol?

…use the MEC/BEAMR process

?

7

Energy Production using MFC technologies

• Electricity production using microbial fuel cells (MFCs)

• H2 Production from biomass using the MEC/BEAMR process: overcoming the “fermentation barrier”

• A path to renewable energy

8

Demonstration of a Microbial Fuel Cell (MFC)

MFC webcam (live video of an MFC running a fan)

www.engr.psu.edu/mfccam

9

Microbial Fuel Cells: Aqueous cathode

Proton exchange membrane (PEM)

load

Anode Cathode

bact

eria

Oxidation products

(CO2)

Fuel (wastes)

e-e-

O2

H2OH+

10

• Methanogenesis– Generation of methane– Methanogens– Anaerobic digesters

• Electrogenesis– Generation of electricity– Exoelectrogens– Microbial fuel cells (MFCs)

• Electrohydrogenesis– Generation of H2 gas– Exoelectrogens– Microbial electrolysis cells (MECs)

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Microbial community analysis (DGGE)

Lee et al. (2003)

24%=α-, 7%=β-, 21%=γ- , 21%= δ-Proteobacteria; 27%=others

Wastewater (acetate)

Kim et al. (2004)

36%=unidentified, 25%=β- and 20%=α-Proteobacteria, and 19%= Cytophaga+Flexibacter+Bacterioides

Wastewater (starch)

Logan et al. 2005

γ-Proteobacteria, 40% Shewanellaaffinis KMM, then Vibrio spp. and Pseudoalteromonas sp.

Marine sediment(cysteine)

Phung et al. (2004)

β-Proteobacteria (related to Leptothrixspp.)

River sediment (river water)

Phung et al. (2004)

α-Proteobacteria (mainly Actinobacteria) River sediment (glucose+glutamic acid)

ReferenceCommunityInoculum(substrate)

12

New finding: bacteria use “nanowires”

Bacteria that can transfer electrons directly to the electrode:

- Geobacter sulfurreducens- Alteromonas sp. - Shewanella spp.

Bacterium Electrode

e-

e-

e-

Source: Gorby et al. PNAS (2006)

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Current level of development:System architecture (not microbiology) limits power

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Power density is limited by internal (system) resistance

System resistance: 66,920 Ω

Power: 0.3-3 mW/m2

System resistance: 1,756 Ω

Power: 40 mW/m2

Source: Min et al., Wat. Res (2005)

2

int

2

)( ex

ex

RRAROCVP

+=

P= Power normalized surface area

OCV= Open circuit voltage

Rex= External resistance

Rin= Internal resistance

A= Electrode projected surface area

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- Bacteria oxidize organic matter

- Generate electricity from any form of biodegradable organic matter

load

Anode

Cathode

bact

eria

Oxidation products

(CO2)

Fuel (wastes)

e-

Oxidant (O2)

Reduced oxidant (H2O)

H+

e-

Air Cathode MFC

16

Power production (early studies)

146Domestic wastewater

269Protein 309Butryate506Acetate494Glucose

Power (mW/m2)Substrate

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Corn stover: 90% of 250 million tons remains unused in fields (largest source of solid waste biomass in USA)

Electricity from corn stover hydrolysates

Maximum Power= 860 mW/m2

~93% removal of biodegradable organic matter

0

20

40

60

80

100

1000 800 450 250Substrate (mg COD/l)

BOD

Rem

oval

%

Neutral Acidic

0

200

400

600

800

1000

0 1000 2000 3000 4000

Current Density (mA/m2)

Pow

er D

ensi

ty (m

W/m

2)

Acidic Old Cathode Acidic New CathodeNeutral Old Cathode Neutral New Cathode

Source: Zuo et al. (2006) Energy & Fuels

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Electricity from cellulose and chitin in a sediment MFC

SeawaterCathode

AnodeMarine Sediment

Chitin 80 Chitin 20

Carbon cloth filled with Chitin 80

CelluloseTime (hr)

0 50 100 150 200 250 300

Pow

er D

ensi

ty (m

W/m

2 )

020406080

100120

Rep 1Rep 2Rep 3

Time (hr)

0 50 100 150 200 250 300

Pow

er D

ensi

ty (m

W/m

2 )

0

20

40

60

80

100

Chitin80 Chitin20 Control

Cellulose

Chitin

Rezai, Richard, Brennan and Logan, ES&T (2007)

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Advances in operating conditions and materials selection

• Factors affecting performance– - Solution conductivity– - Electrode spacing – - Continuous flow

• Cathode materials– Non-precious metal cathode catalyst– Diffusion layers for water control

• Anode materials– Treatment technique for rapid power generation

(high-temperature ammonia gas)

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Power production in MFCs is improving

0.001

0.01

0.1

1

10

100

1000

10000

1998 2000 2002 2004 2006 2008Year

Pow

er d

ensi

ty (m

W/m

2 ) Air-cathode-WWAir-cathode-ChemicalsAqueous cathodeSediment MFCs

End of 2006:1970 mW/m2

115 W/m3

Start of 2007:2400 mW/m2

76 W/m3

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System Scale (Wastewater Treatment)

What will a large scale MFC system of the future look like?

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System Scale up

• Scale up covered by two Penn State patents– “Materials and configuration for scalable

microbial fuel cells.” Provisional patent.

– “A bioelectrochemically assisted microbial reactor (BEAMR) that generates hydrogen gas.” (60/588,022)

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Brush anodes and tube cathode reactors

System Scale up

Sources: Logan et al. (2007) and Zuo et al. (2007)both in: Environ. Sci. Technol. (2005)

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Essentials of the MEC Process

• Conventional MFC: oxygen at the cathode• Anode potential= -300 mV• Cathode Potential= +200 mV (+804 mV theory)• Circuit working voltage= 200 - (-300) = 500 mV

• MEC: (no oxygen)• Anode potential= -300 mV• Cathode potential: 0 mV• Needed to make H2= 410 mV (theory)• Circuit (~300 mV) augmented with >110 mV= >410 mV

Anode: C2H4O2 + 2 H2O → 2 CO2 + 8 e- + 8 H+

Cathode: 8 H+ + 8 e- → 4 H2

Anode: C2H4O2 + 2 H2O → 2 CO2 + 8 e- + 8 H+

Cathode: O2 + 4 H+ + 4 e- → 2 H2O

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Biomass H2- from any biomass using MECs

H2

Cathode

CO2 e-

H+

e-

Bacteria

Anode

PEM

No oxygen in cathode chamber

PS

Ref: Liu et al. Environ. Sci. Technol. (2005)

No oxygen in anode chamber

0.25 V needed (vs 1.8 V for water electrolysis)

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Low applied voltages used for H2 production

0

0.2

0.4

0.6

0.8

1

0.2 0.4 0.6 0.8 1Applied voltage (V)

Cur

rent

den

sity

(A/m

2 )-300

-290

-280

-270

-260

-250

Anod

e po

tent

ial (

mV)CD

AP

Minimum voltage needed is >0.25 V(=0.11 V theory)

Source: Liu et al. Environ. Sci. Technol. (2005)

BEAMR voltage much less than that needed for water electrolysis (1.8 V)

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50

60

70

80

90

100

110

0.2 0.4 0.6 0.8 1Applied voltage (V)

Rec

over

y (%

)

H2 CE

RCE= 60%-78% (electrons from substrate)

RCat=90-100% (H2 from electrons)

-Overall:RH2= >70% (>0.5 V)

(=2.9 mol-H2/mol-acetatevs maximum of 4 mol/mol)

Source: Liu et al. Environ. Sci. Technol. (2005)

H2 Recovery

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Breakthrough in H2 production rates and energy efficiencies

Cheng & Logan, PNAS (2007)

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0.0

0.5

1.0

1.5

2.0

0.0 0.2 0.4 0.6 0.8 1.0

Applied voltage (V)

H2 ra

te, Q

H2 (

m3 m

-3 d

-1)

0.0

1.0

2.0

3.0

4.0

H2 Y

ield

, YH

2 (m

ol m

ol-1)

0

50

100

150

200

250

300

0.0 0.2 0.4 0.6 0.8 1.0Applied voltage (V)

Ene

rgy

effic

ienc

y (%

)

0

20

40

60

80

100

120

140

H2

Rec

over

y, R

H2

(%)

PSPS + substrateH2

High hydrogen yields except at 0.2 V

H2 production increases with applied voltage

Source: Cheng & Logan, PNAS (2007)

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H2 production from various substrates Substrate

YH2

(mol-H2 mol- substrate-1)

RH2 (%)

Production rate

(m3 m-3 d-1)

ŋw (%)

ηW+S (%)

Glucose 8.55 71 1.23 266 64

Cellulose 8.20a 68 0.11 268 63

Acetic acid 3.65 91 1.10 261 82

Butyric acid 8.01 80 0.45 285 77

Lactic acid 5.45 91 1.04 283 82

Propionic acid 6.25 89 0.72 248 79

Valeric acid 8.77 67 0.14 263 66

Source: Cheng & Logan, PNAS (2007)

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Energy Utilization in the USA

• US energy use: 97 quad

• US electricity generation: 13 quad

• Energy used for water infrastructure 0.6 quad(water and wastewater) (5%)

97 quad [quadrillion BTUs] = 28,400 TWh (terawatt hours)

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Energy value of wastewater

• Electricity used for water infrastructure= 0.6 quad (~5% of all electricity)

• Energy in wastewater= 0.5 quad• 0.1 quad of energy in domestic wastewater • 0.1 quad in food processing wastewater • 0.3 quad in animal wastes

Wastewater has 9.3× more energy than treatment consumes

(Toronto WWTP, Shizas & Bagley (2003)

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CONCLUSIONS

• MFCs represent a viable technology for simultaneous electricity generation and wastewater treatment

• The MEC/BEAMR process can overcome the “fermentation barrier” and result in high yields of hydrogen from any source of biomass

• The technology now exists for system scaleup– pilot testing is needed.

36

Acknowledgements

Current research sponsors:

NSF (BES Program): 2003-2007

WERF (Busch Award): 2004

AFOSR: 2006-2009

Air Products: 2006-2008

Previous sponsors:

NSF & EPA TSE (CTS Program)

USDA-DOE

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Thanks to students and researchers in my laboratory at Penn State!

Left to right: Shaoan Cheng, Doug Call, KyeongHo Lim (visiting Prof), Markus Coenen (visitor), Farzaneh Rezai (PhD Ag&BioEng), Charles Winslow, Valerie Watson, David

Jones (technician), Yi Zuo, Defeng Xing, Priscilla Selembo (PhD ChE), Rachel Wagner, [Bruce Logan]

Missing: Yujie Fang and YoungHo Ahn (visiting Profs), Jooyoun Nam (visiting student)

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Further information?

• New book on MFCs (published by John Wiley, 2008)

• Microbial Fuel Cell Symposium, May 27-29, 2008, Penn State University

39

LinksEmail: [email protected]

Web page: www.engr.psu.edu/ce/enve/logan.htm

Logan MFC webpage: www.engr.psu.edu/ce/enve/mfc-Logan_files/mfc-Logan.htm

International MFC site:www.microbialfuelcell.org

MFC webcam (live video of an MFC running a fan)

www.engr.psu.edu/mfccam

electricity and hydrogen production using microbial fuel cell-based

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