Electricity and hydrogen production using microbial fuel ...€¦ · 1 Electricity and hydrogen...
Transcript of Electricity and hydrogen production using microbial fuel ...€¦ · 1 Electricity and hydrogen...
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Electricity and hydrogen production using microbial fuel cell-based technologies
Bruce E. LoganPenn State University
EngineeringEnvironmental
Institute
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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)
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Current sources of H2 Production
Electrolysis4%
Coal18%
Natural Gas48%
Heavy oils and naphtha
30%
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Time (h)0 50 100 150 200 250
Bio
gas
(mL)
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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)
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H2 can be produced by cellulose fermentation
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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)
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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
?
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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
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Demonstration of a Microbial Fuel Cell (MFC)
MFC webcam (live video of an MFC running a fan)
www.engr.psu.edu/mfccam
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Microbial Fuel Cells: Aqueous cathode
Proton exchange membrane (PEM)
load
Anode Cathode
bact
eria
Oxidation products
(CO2)
Fuel (wastes)
e-e-
O2
H2OH+
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• 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)
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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)
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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
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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
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oval
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Neutral Acidic
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Current Density (mA/m2)
Pow
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ensi
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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)
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Pow
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ensi
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W/m
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Time (hr)
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ensi
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W/m
2 )
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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
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Pow
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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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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
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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
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0.2 0.4 0.6 0.8 1Applied voltage (V)
Cur
rent
den
sity
(A/m
2 )-300
-290
-280
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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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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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Applied voltage (V)
H2 ra
te, Q
H2 (
m3 m
-3 d
-1)
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H2 Y
ield
, YH
2 (m
ol m
ol-1)
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rgy
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ienc
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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 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
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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.
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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
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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