UWE John Greenman Microbial Fuel Cells Future of Renewables Low Carbon South West Bristol & Bath Science Park 220415

1. Microbial Fuel Cells for the near and distant future
John Greenman1* and Ioannis Ieropoulos2
1Faculty of Health & Applied Sciences, University of the West of England,
Bristol BS16 1QY, UK
2Bristol BioEnergy Centre, BRL, University of the West of England, Bristol
BS16 1QY, UK

2. Microbial Fuel Cells
1911 M.C. Potter (University of Durham); first “discovery”
1985: Picked up again by P. Bennetto in King’s College
1991: Habermann and Pommer; sulphide-mediated MFC,
operated over 5-years
2004: Lovley et al.: Electron transport out of the bacterial cell
via conductance (“anodophiles”)
2008: Ieropoulos, Greenman, Melhuish: Stacks of small MFC.
[Microbial fuel cells based on carbon veil electrodes: Stack
configuration and scalability. International Journal of
Energy Research, 32(13): 1228-1240].

3. • Organic waste IN electrical energy OUT –
a truly green technology
• Biochemical energy in waste turned directly
into electricity by bacteria resident in the
anode
• Now a rapidly expanding international
research field
What are microbial fuel cells and how do they work

4. • Microbial Fuel Cells (MFCs) consist of two compartments
(anode and cathode): each containing an electrode with
battery-like terminals
• In the MFC, bacteria form a living community (called a
biofilm) around the anode (biofilm-electrode)
(This is ecologically and physiologically stable and self-
sustainable giving steady state conditions)
• The biofilm-electrode is fed waste organic matter as
biofuel and the microbes metabolise the fuel into electrons,
H+ (protons), CO2 and new cell progeny.
(It is the new cell progeny that “fixes” the soluble elements
into new biomass material, highly suitable for fertilizer)

5. MFC structure
Cathode
Protonexch
a
Anod
e

6. Fuel
2O
2O
2O
2O
2O
2O
2O
2O
2O
2O
2O
2O
2O
2O
How do they work
H+
H+
H+
H+
H+
O
H+
OH+
C/E
C/E
e-
e-
e-
e-
H+
H+
H+
H+
H+
C/E
Protonexchangemembrane
ANODE CATHODE

7. In May 2007, the University of Queensland,
Australia completed its prototype MFC as a
cooperative effort with Foster's Brewing.
The project failed
(now used as a system to produce caustic soda)

8. Sizes and shapes of MFC
Miniaturisation
• Increases surface area to volume ratio
• Minimises proton path distance
• Increases power density

9. Our strategy is therefore:
• Miniaturisation and multiplication

10. Like batteries, they can be joined in series or parallel
in order to step up voltage or current

12. greenplants
insects,molluscs,crustaceans
greenplants(cane,beet)
bacterialfermentation
fruit,vegetablepolysaccharide
dairyproducts,protein
woodsugar
bacterialfermentationproducts,
dairyproducts
corn,potatoes,wheat,rice
0
20
40
60
80
100
120
140
160
MeanCurrentoutput[mA]
cellulose chitin sucrose acetate pectin casein xylose lactate starch
Substrate type
Microbial Fuel Cells
Substrate diversity: refined organic compounds

13. Microbial Fuel Cells
Substrate diversity: non-refined organic mixtures
• Urine
• Sewage wastewater
• Waste products from the food, fermentation and biotech-industries

14. Low grade organic substrates (biomass)
CO2
Natural
Decomposition
e.g. compost heap,
e.g. anaerobic digester
MFC
e-
Immediate
carbon cycle
Biofuels
Combustion

15. Power outputs:
The first MFC invented by Potter in 1911 produced a few nanoWatts
(nW) of power
Our early nafion-based MFC produced units of (1-2) microWatts (mW)
Our best ceramic based MFC now produce milliWatts (mW),
So a stack of 1000 should produce over 1 Watt of power
MFC-technology combined with new systems for energy storage such as:
Batteries, capacitors, supercapacitors and ultracapacitors
Graphine-based
Nanotube-based
Aluminium-ion based

16. What are the Key challenges:
Economic costs of material fabrication and mass manufacture
Carbon veil electrodes – essential but low cost (pence)
Stainless steel net and wires – could be made redundant since relatively expensive
Plastic end bits and tubes – certainly redundant since very expensive
Proton exchange – essential process which now is conducive with
economies of scale, due to ceramic materials, which have replaced the
expensive and prone-to-fouling plastic polymer (Nafion)
The current high costs are only because of the prototype stage; once
the process goes into mass manufacturing, then unit costs are
expected to be significantly reduced
The main components of an MFC are:

17. EcoBot-III
Present state of technology:
EcoBot-IV

18. Soft wearable MFCs

19. Origami-MFC (Biodegradable)

20. In summary
• Electrical energy produced
• Treatment of waste
• Re-cycling of essential elements (e.g. phosphate)
• Production of clean water
• Working without adverse environmental effects
• Near future: Stacks distributed widely to enable humans to
charge phones, laptops, LEDs, small pumps, robots & gadgets
• Distant future: charging batteries for Electric vehicles?
MFC stacks embodied in households, factories and farms
encourage humans to see the advantages of sludge over oil

21. CogSys
Cognitive Systems
The Thriplow Trust
Acknowledgements