UWE John Greenman Microbial Fuel Cells Future of Renewables Low Carbon South West Bristol & Bath...
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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
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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].
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• 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
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• 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)
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MFC structure
Cathode
Pro
ton
ex
cha
An
od
e
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Fuel
2O
2O
2O2O
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
Pro
ton
exchan
ge mem
bran
e
ANODE CATHODE
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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)
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Sizes and shapes of MFC
Miniaturisation• Increases surface area to volume ratio• Minimises proton path distance• Increases power density
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Our strategy is therefore:
• Miniaturisation and multiplication
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Like batteries, they can be joined in series or parallelin order to step up voltage or current
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gre
en
pla
nts
inse
cts
, m
ollu
scs, cru
sta
ce
an
s
gre
en
pla
nts
(ca
ne
, b
ee
t)
ba
cte
ria
l fe
rme
nta
tio
n
fru
it, ve
ge
tab
le p
oly
sa
cch
ari
de
da
iry p
rod
ucts
, p
rote
in
wo
od
su
ga
r
ba
cte
ria
l fe
rme
nta
tio
n p
rod
ucts
,
da
iry p
rod
ucts
co
rn, p
ota
toe
s, w
he
at, r
ice
0
20
40
60
80
100
120
140
160
Mea
n C
urren
t o
utp
ut
[ mA
]
cellulose chitin sucrose acetate pectin casein xylose lactate starch
Substrate type
Microbial Fuel CellsSubstrate diversity: refined organic compounds
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Microbial Fuel Cells
Substrate diversity: non-refined organic mixtures
• Urine• Sewage wastewater• Waste products from the food, fermentation and biotech-industries
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Low grade organic substrates (biomass)
CO2
NaturalDecompositione.g. compost heap,e.g. anaerobic digester
MFC
e-
Immediate carbon cycle
BiofuelsCombustion
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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-basedNanotube-basedAluminium-ion based
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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 theexpensive and prone-to-fouling plastic polymer (Nafion)
The current high costs are only because of the prototype stage; oncethe process goes into mass manufacturing, then unit costs are expected to be significantly reduced
The main components of an MFC are:
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EcoBot-III
Present state of technology:
EcoBot-IV
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Soft wearable MFCs
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Origami-MFC (Biodegradable)
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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
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CogSysCognitive Systems
The Thriplow Trust
Acknowledgements