Microbial Electrochemical Systems
The living battery hiding in wastewater
Certain bacteria breathe by pushing electrons onto solid surfaces. Give them an electrode and they turn sewage, sediment, and CO₂ into electricity, hydrogen, clean water, and recovered nutrients. This is the science — and the machines it makes possible.
- 1911
- first observed by M.C. Potter
- 5
- physics families
- 14
- system types
- 21
- interactive reactors
Follow one electron
The journey of a single electron
Forget the whole cell for a moment. Follow one electron from the acetate a bacterium just split, out through the wire that lights a lamp, and home again to make a drop of water — one step at a time.
A bacterium in the anode biofilm oxidizes acetate and releases an electron.
How it works
One skeleton, fourteen machines.
A microbial anode, a cathode, a membrane, a wire. Change the cathode reaction, the applied voltage, or the number of chambers and that one skeleton becomes fourteen different machines — grouped here by the five physics families they belong to. Pull each one apart, click any layer for its material and the literature behind it, and scroll to watch the next device build on it.
Microbial fuel cell
MFC
Assembling 3D model…
drag · scroll to zoom · click a layer
Graphite-brush bioanode
Graphite-fibre brush + exoelectrogen biofilm
A graphite-fibre brush on a titanium core, colonised by exoelectrogens that oxidise organic matter and transfer their electrons directly to the electrode. The huge fibre surface area gives the biofilm enormous room to grow per unit volume.
Design note
Brush anodes give far more biofilm area per volume than flat carbon — the reason they dominate high-power MFCs and the electron source every downstream device inherits.
Sources
Logan, B.E. et al. Environ. Sci. Technol. 41, 3341–3346 (2007)
Graphite-fibre brush anodes raise air-cathode MFC power.
Act I · Anodic oxidation
3 layersMicrobial fuel cell
MFC
Assembling 3D model…
drag · scroll to zoom · click a layer
AGraphite-brush bioanode
Graphite-fibre brush + exoelectrogen biofilm
A graphite-fibre brush on a titanium core, colonised by exoelectrogens that oxidise organic matter and transfer their electrons directly to the electrode. The huge fibre surface area gives the biofilm enormous room to grow per unit volume.
Design note
Brush anodes give far more biofilm area per volume than flat carbon — the reason they dominate high-power MFCs and the electron source every downstream device inherits.
Explore in the research corpus →Sources
Logan, B.E. et al. Environ. Sci. Technol. 41, 3341–3346 (2007)
Graphite-fibre brush anodes raise air-cathode MFC power.
Explode01 · MFC · Microbial fuel cell
Start with electricity
Electroactive bacteria oxidise organic waste at the anode and release their electrons. Wired through a load on the way to an air cathode — where oxygen simply becomes water — that current is harvested directly. A bioanode, a membrane, an air cathode, no voltage supplied. This is the skeleton every other device inherits.
Key moveO₂ + 4H⁺ + 4e⁻ → 2H₂O
- 4 layers
Microbial solar cell
MSC
Assembling 3D model…
drag · scroll to zoom · click a layer
PCulture panels
Cyanobacterial culture between ITO glazing
Glazed panels of photosynthetic microbial culture that are also the photosynthetic + electrogenic working electrode; panel colour intensity is a visual proxy for biomass density.
Design note
Biophotovoltaics: oxygenic phototrophs export electrons under illumination, turning a facade into a light-driven bioelectrochemical array.
Explore in the research corpus →Sources
McCormick, A.J. et al. Energy Environ. Sci. 8, 1092–1109 (2015)
Biophotovoltaics — phototrophs in bioelectrochemical systems.
Explode02 · MSC · Microbial solar cell
Let sunlight be the fuel
Swap the heterotrophs for phototrophs. Photosynthetic microbes split water with sunlight and hand those electrons to the anode — solar power with a self-repairing, self-replicating light harvester. Tile the cells across a curtain wall and the building quietly generates its own current.
Key movelight + H₂O → O₂ + H⁺ + e⁻
- 3 layers
Electrochemical snorkel
MESNORK
Assembling 3D model…
drag · scroll to zoom · click a layer
ABuried anodic end
Carbon/graphite in anoxic sediment + biofilm
The lower end of the conductor, buried in anoxic sediment and colonised by the native exoelectrogenic biofilm, which oxidises organic matter and releases electrons.
Design note
No inoculation, no added substrate — the sediment is the fuel, so the snorkel is essentially maintenance-free.
Explore in the research corpus →Sources
Erable, B. et al. Bioresour. Technol. 102, 5622–5625 (2011)
The microbial electrochemical snorkel concept.
Explode03 · MESNORK · Electrochemical snorkel
Short it out for fast cleanup
Drop the external circuit entirely. A single conductor runs from a buried anodic end straight to an aerated one, so electrons take the shortest path. You harvest no power — but organic-matter removal races ahead, which is exactly the trade you want when treatment, not electricity, is the goal.
Key moveelectrons → shortest path · no load
- 4 layers
Microbial rechargeable battery
MRB
Assembling 3D model…
drag · scroll to zoom · click a layer
AMicrobial anode
Graphite-brush + exoelectrogen biofilm
The familiar bioanode; while substrate is available it drives current into the capacitive electrode, storing charge.
Design note
A living anode’s output is intermittent — it tracks feeding. The battery exists to smooth that.
Explore in the research corpus →Sources
Deeke, A. et al. Environ. Sci. Technol. 46, 3554–3560 (2012)
Capacitive bioanodes for internal energy storage in BES.
Explode04 · MRB · Microbial rechargeable battery
Store the trickle, discharge on demand
A living anode’s output is intermittent — it comes and goes with feeding. Add a capacitive electrode and it charges while fed, then releases a burst of power when you need it. The fuel cell becomes a rechargeable battery, buffering biology into dispatchable power.
Key movecharge ⇄ discharge · capacitive
Act II · Cathodic reduction
5 layersMicrobial electrolysis cell
MEC
Assembling 3D model…
drag · scroll to zoom · click a layer
AGraphite-brush bioanode
Graphite-fibre brush + exoelectrogen biofilm
A graphite-fibre brush colonised by exoelectrogens that oxidise organic matter and hand their electrons to the electrode — the same bioanode as a microbial fuel cell. The MEC changes the cathode and adds a voltage, not the anode.
Design note
Anode microbes do most of the thermodynamic work, which is why the applied bias can be so small — the electrode is deliberately identical to a high-performance MFC anode.
Explore in the research corpus →Sources
Logan, B.E. et al. Environ. Sci. Technol. 41, 3341–3346 (2007)
Graphite-fibre brush anodes for bioelectrochemical systems.
Explode05 · MEC · Microbial electrolysis cell
Add a nudge, make hydrogen
Now make the cathode do the work. Seal it from air and apply about 0.4 V — a tenth of what plain electrolysis demands. Starved of oxygen, the cathode reduces protons instead of making water. The load became a supply, and the waste stream becomes a storable fuel.
Key move2H⁺ + 2e⁻ → H₂
- 5 layers
Microbial electrosynthesis
MES
Assembling 3D model…
drag · scroll to zoom · click a layer
AAbiotic anode
Dimensionally-stable inert anode (Ir/Ru-MMO)
An inert, non-biological anode oxidising water to supply the electron stream that drives CO₂ reduction at the biocathode.
Design note
No biofilm here — keeping the anode abiotic avoids competing biology; this electrode’s only job is the electron source.
Explore in the research corpus →Sources
Rabaey, K. & Rozendal, R.A. Nat. Rev. Microbiol. 8, 706–716 (2010)
Microbial electrosynthesis — the electrical route for microbial production.
Explode06 · MES · Microbial electrosynthesis
Reverse it to synthesise chemicals
Move the biofilm to the cathode and run electrons the other way. Fed CO₂ and a small applied voltage, cathodic microbes fix carbon into acetate and ethanol. The anode now oxidises water; the device is a biological power-to-X reactor.
Key moveCO₂ + H⁺ + e⁻ → acetate
- 5 layers
Microbial electro-Fenton
MEFS
Assembling 3D model…
drag · scroll to zoom · click a layer
ABioanode
Graphite-brush + exoelectrogen biofilm
The standard bioanode, oxidising organic matter to feed electrons to the peroxide-generating cathode.
Design note
Unchanged from an MFC — the Fenton chemistry all happens at the cathode.
Explore in the research corpus →Sources
Zhu, X. & Logan, B.E. J. Chem. Technol. Biotechnol. 88, 1624–1630 (2013)
Bioelectrochemical Fenton systems for pollutant degradation.
Explode07 · MEFS · Microbial electro-Fenton
Make radicals, shred pollutants
Aim the cathode at oxygen with an iron catalyst and it manufactures hydroxyl radicals — among the strongest oxidants known. They tear apart persistent micropollutants the biofilm alone cannot touch, turning the reactor into an on-site advanced-oxidation plant.
Key moveO₂ → H₂O₂ → ·OH
Act III · Ion transport
5 layersMicrobial desalination cell
MDC
Assembling 3D model…
drag · scroll to zoom · click a layer
ABioanode
Graphite-brush + exoelectrogen biofilm
The familiar MFC bioanode oxidising organic matter. Its electrons — and the electric field they set up across the cell — are what pull the salt ions out of the middle chamber.
Design note
An MDC adds chambers, not applied voltage: the desalination runs entirely on the microbial potential.
Explore in the research corpus →Sources
Cao, X. et al. Environ. Sci. Technol. 43, 7148–7152 (2009)
The first microbial desalination cell.
Explode08 · MDC · Microbial desalination cell
Split the cell to desalinate
Now put the current to work moving ions. Insert a third chamber between the electrodes, bounded by an anion- and a cation-exchange membrane. No extra voltage needed — the field the bacteria already generate pulls Na⁺ and Cl⁻ out of the middle stream, desalinating on waste energy.
Key moveNa⁺, Cl⁻ → out of the middle
- 4 layers
Capacitive deionization
MCDI
Assembling 3D model…
drag · scroll to zoom · click a layer
ABioanode
Graphite-brush + exoelectrogen biofilm
The bioanode; the current it drives is what pulls salt ions onto the capacitive electrodes.
Design note
MCDI is MFC-driven — the microbes replace the external pump/power that ordinary CDI needs.
Explore in the research corpus →Sources
Yuan, H. et al. Bioresour. Technol. 195, 116–123 (2015)
Microbial capacitive desalination cells.
Explode09 · MCDI · Capacitive deionization
Adsorb the salt, store the charge
Instead of a third chamber, flank the stream with capacitive electrodes. As the cell runs they electrostatically pull salt ions out of the water and hold them in the same double layer that stores charge — then release a concentrated brine on regeneration.
Key moveions → electrode double layer
- 3 layers
Reverse electrodialysis cell
MREC
Assembling 3D model…
drag · scroll to zoom · click a layer
ABioanode
Graphite-brush + exoelectrogen biofilm
The bioanode supplies the base microbial potential that the salinity-gradient stack then augments.
Design note
The microbes provide most of the voltage; the membrane stack only has to make up the last bit for H₂.
Explore in the research corpus →Sources
Kim, Y. & Logan, B.E. PNAS 108, 16176–16181 (2011)
Microbial reverse-electrodialysis cells for H₂.
Explode10 · MREC · Reverse electrodialysis cell
Add a salinity gradient, free hydrogen
Stack river-versus-sea membrane pairs into the cell. The blue energy of mixing waters adds to the microbial voltage — just enough extra push that the cathode evolves hydrogen with no power supply at all.
Key movegradient + microbe → H₂
- 4 layers
Nutrient recovery cell
MNRC
Assembling 3D model…
drag · scroll to zoom · click a layer
ABioanode
Graphite-brush + exoelectrogen biofilm
The bioanode both treats the organic load and supplies the migration current that moves nutrient ions.
Design note
Recovering N and P is far less energy-intensive than oxidising them away — that is the case for MNRC.
Explore in the research corpus →Sources
Kuntke, P. et al. Water Res. 46, 2627–2636 (2012)
Ammonium recovery in a bioelectrochemical system.
Explode11 · MNRC · Nutrient recovery cell
Migrate the nutrients, recover fertiliser
Point the migration current at ammonium and phosphate. Selective membranes concentrate them into a recovery chamber where, with magnesium, they crystallise as struvite — turning an energy-hungry nitrogen-removal problem into a saleable slow-release fertiliser.
Key moveNH₄⁺ + PO₄³⁻ → struvite
Act IV · Selective reduction
4 layersMetal recovery cell
MMRC
Assembling 3D model…
drag · scroll to zoom · click a layer
ABioanode
Graphite-brush + exoelectrogen biofilm
The standard MFC bioanode. Its oxidation of organic matter both treats the waste stream and supplies the electrons that reduce the metal at the cathode.
Design note
The anode is unchanged from an MFC — an MMRC is defined entirely by what happens at the cathode.
Explore in the research corpus →Sources
Logan, B.E. et al. Environ. Sci. Technol. 40, 5181–5192 (2006)
Canonical MFC methodology — the bioanode this inherits.
Explode12 · MMRC · Metal recovery cell
Aim the cathode to recover metal
Collapse back to two chambers and feed the cathode a metal-laden effluent. The same electrons that once made water now reduce dissolved copper, silver, or chromium to solid, plating them onto the electrode. The reactor becomes a mine.
Key moveCu²⁺ + 2e⁻ → Cu⁰
- 4 layers
Electroremediating cell
MERC
Assembling 3D model…
drag · scroll to zoom · click a layer
ABioanode
Graphite-brush + exoelectrogen biofilm
The bioanode oxidises organic matter and feeds electrons to the reductive-remediation cathode.
Design note
Standard MFC anode — an MERC is defined by the cathode reaction it targets.
Explore in the research corpus →Sources
Gregory, K.B. & Lovley, D.R. Environ. Sci. Technol. 39, 8943–8947 (2005)
Electrode-driven reductive remediation.
Explode13 · MERC · Electroremediating cell
Reduce the pollutant to harmless
Point those same electrons at a contaminant and it comes out reduced: nitrate to nitrogen gas, chlorinated solvents dehalogenated, azo dyes decolorised. The reactor treats the water by reduction, without adding a single chemical.
Key moveNO₃⁻ + e⁻ → N₂
Act V · Sensing
4 layersBioelectrochemical sensor
MBES
Assembling 3D model…
drag · scroll to zoom · click a layer
ASensing bioanode
Graphite-brush + exoelectrogen biofilm
The bioanode is the transducer: the current the biofilm produces tracks the concentration of what it is fed, so the electrode reads the water directly.
Design note
No separate transducer — the biology is the sensor, and it powers itself.
Explore in the research corpus →Sources
Kim, B.H. et al. Biotechnol. Lett. 25, 541–545 (2003)
A mediator-less BOD sensor using a microbial fuel cell.
Explode14 · MBES · Bioelectrochemical sensor
Stop harvesting — start measuring
Read the current instead of drawing it. The signal a biofilm produces tracks exactly what it is fed, so the electrode becomes a self-powered probe: a steady reading reports oxygen demand, and a sudden drop flags a toxicity spike — no separate transducer, deployable for years.
Key movecurrent ∝ analyte
Coda
7 layersLab-on-chip MFC
CHIP
Assembling 3D model…
drag · scroll to zoom · click a layer
L1ITO optical window
Indium-tin-oxide on glass
A transparent conductive-oxide lid that doubles as a current path and an optical/microscopy readout window — the interrogation port the inline O₂/pH sensor spots are read through.
Original ✕
Halide-perovskite PV cover
Reviewed ✓
ITO optical + conductive window
What the review caught
A halide photovoltaic perovskite is lead-bearing and hydrolyses within hours in a wet, salty, biological cell. Re-specified as ITO for optics + conduction; any photoactive layer must be a water-stable oxide perovskite kept outside the wet zone.
Explore in the research corpus →Sources
Leijtens, T. et al. Adv. Energy Mater. 5, 1500963 (2015)
Instability of metal-halide perovskites in humid / aqueous conditions.
Explode15 · CHIP · Lab-on-chip MFC
Now shrink the whole thing onto a chip
Every machine above changes what the cell does. This one changes what it is: the entire fuel cell — graphene-foam bioanode, microfluidic reactor, air-breathing cathode, wireless power takeout — miniaturised onto a glass slide and rebuilt layer by layer by a rigorous review. Same principle, in millimetres, self-powering a wireless sensor.
Key moveµW harvest → wireless sensor
A marketing render built to survive a specialist’s read, not a fabricated datasheet. Citations point to the literature behind each material choice; specific geometry and dimensions are illustrative.
Applications
21 reactors, one living principle
Each card below is a real, interactive 3D reactor from the MESSAI lab — spanning microlitre chips to full municipal plants. Filter by what they do, then open one to spin the model and see its performance envelope.
Emerging frontiers
Where these systems are heading
Beyond the reactors already in the catalogue, the same handful of device types is opening up new territory. Each of these is an active research direction — powered by one of the machines from the story above.
Agriculture & food
Food-and-beverage effluent and farm runoff are strong, sugary streams — ideal fuel-cell feedstocks. On-site cells treat winery, dairy, and brewery wastewater while trickling power to sensors, and nutrient-recovery cells pull nitrogen and phosphate back out as fertiliser.
Carbon capture → fuels
Fed captured CO₂ from flue gas or direct air, a biocathode fixes it into acetate, ethanol, and other platform chemicals — storing renewable electricity as liquid carbon instead of venting it. Power-to-X, run by microbes.
Powered by
Medical & implantable
The self-powered biosensing that reads a river can read a body. Ingestible and implantable cells run on gut or interstitial fluid, powering diagnostics and reporting biomarkers in real time — with no battery to replace.
Powered by
Off-grid & humanitarian
Where the grid doesn’t reach, a sediment or wastewater cell is a battery you feed with mud or sewage. It powers remote sensors for years and, at village scale, pairs sanitation with a steady trickle of electricity.
Perspectives
The same reactor, five different stories
A microbial fuel cell is a science experiment, a business case, a permit strategy, a climate lever, and a classroom demo — all at once. Choose who’s reading and the story reframes itself.
Read as: Researcher
A hypothesis you can finally test against the whole literature.
“You see an experiment waiting for its priors.”
MES research is gloriously noisy — power-density coefficients of variation run past 1,000%. MESSAI treats that honestly: it extracts parameters from thousands of open-access papers, sorts every system into five physics families, and fits hierarchical Bayesian priors so a point estimate always arrives with its uncertainty attached.
- Reproducibility
- n, units & CoV on every number
- Physics families
- 5 — not 3 hard-coded types
- Uncertainty
- hierarchical priors, calibrated CIs
Start with these
Settings
The same tech, five settings
A microbial reactor that thrives on the seafloor is a different machine in a megacity treatment plant, a brewery, or a spacecraft. Choose where it’s deployed and the binding constraint — and the story — reframes itself.
Deployed in: Off-grid village
With no grid to lean on, a microbial system earns its keep by being self-powered and stubbornly simple. A jar of sediment and two electrodes treats local waste, powers a sensor, and asks for nothing back — no pumps, no chemical inventory, no service truck. The reward is decentralized treatment and trickle power exactly where centralized infrastructure never reaches.
What dominates here: self-sufficiency — every watt and every part has to be local.
- Power budget
- 1–50 µW per device — enough for a sensor
- Infrastructure
- zero grid, zero dosed chemicals
- Maintenance
- buildable and repairable at the bench
Start with these
Impact calculator
What could a plant recover?
Move the inputs — or start from a scenario — to see live, order-of-magnitude estimates of what a microbial-electrochemical treatment train might recover from a waste stream. These are illustrative figures for building intuition, not design numbers for any specific plant.
Start from a scenario
Inputs
Illustrative organic (COD) load: 150 kg/day. Estimated installed capital: $60,000.
Illustrative recovery
Energy recovered
60
kWh / day
from 120 kg COD removed / day
CO₂ avoided
19
t CO₂ / year
recovered + avoided-aeration electricity
Recovered value
$8k
per year
energy sold + aeration saved + resources
Simple payback
8
years (rough)
undiscounted, pilot-era capex ±2×
Order-of-magnitude only. Real microbial-electrochemical performance varies by more than one order of magnitude with substrate, temperature, geometry, and biofilm maturity.
From a curiosity in a petri dish to infrastructure that treats, powers, and recovers.
MESSAI turns the published literature on these systems into models you can query, compare, and design against.