Nine parts, one journey: from peelings to the flame under the cooking pot. Follow the tour or tap a part.
Or pick a part on the unit.
We don't throw it out. We fire it up.
Cassava peelings, spent grain, processing residues: in Côte d'Ivoire, much of this waste is left to rot in the open.
We feed it into an integrated biomethanation unit. Out come biogas for cooking and a controlled digestate for the soil.
Illustration
The unit, part by part
Turn the unit around and open each part: what it does, where it sits, why it is there.
Illustration
3D view: arrow keys to rotate, + and − to zoom, 0 to reset, Esc to close a card.
Guided tour
1 Preparation and hopper
Explain it simply
- What it does
- We grind the cassava peelings and mix them with pressing water, like a thin porridge.
- Where it sits
- Under the shed, next to where the cassava is peeled.
- Why it is there
- The finer the pieces, the faster the tiny living things in the digester can eat them.
- Why it is needed
- Without it, big chunks and sand would clog the unit.
Technical details
- What it does
- Grinding, dilution with pressing water and screening of the feedstock before loading.
- Where it sits
- At the head of the line, on the slab, as close as possible to the site's waste.
- Why it is there
- Fine particle size and diluted matter make digestion faster and steadier.
- Why it is needed
- The screen holds back sand and long fibres, which would foul the digester.
Dimensions
- Inlet hopper volume
- coming soon
2 Potash buffering
Key step
No buffering, no gas. Local potash keeps the mix at a stable pH (pH 6.8 to 7.4): this is what the sensors watch around the clock.
Explain it simply
- What it does
- We add a little local potash to take the acidity out of the mix.
- Where it sits
- Between preparation and the digester.
- Why it is there
- Cassava peelings make the mix sour, like a lemon.
- Why it is needed
- Without it, the tiny living things stop dead and the unit makes no more gas.
Technical details
- What it does
- Dosing of local potash, made from leached wood ash, to hold the digester's pH.
- Where it sits
- On the feed line, upstream of the digester, with a pH probe.
- Why it is there
- Cassava residues acidify the medium; a falling pH stops the methane-producing bacteria.
- Why it is needed
- This is the step production depends on: the pH probe is monitored remotely at all times.
Dimensions
- Buffering reagent
- local potash (leached ash) target
- Target pH in the digester
- pH 6.8 to 7.4 target
- Target alkalinity
- 2,000 to 4,000 mg CaCO₃/L target
- Target VFA/alkalinity ratio
- < 0.4 target
- Buffering monitoring
- pH probe + remote alert target
3 Digester
Explain it simply
- What it does
- This is the stomach. Tiny living things eat the waste here, without air.
- Where it sits
- In the middle of the unit. It is the biggest part.
- Why it is there
- Like a closed pot simmering for a long time, it gives the waste time to change.
- Why it is needed
- This is where the gas is born. Without it, no biogas.
Technical details
- What it does
- Sealed, banded high-density polyethylene tank on a masonry base, where anaerobic digestion takes place.
- Where it sits
- In the middle of the slab, between buffering and digestate separation.
- Why it is there
- The retention time of the matter determines how much of the waste becomes biogas.
- Why it is needed
- Methane-producing microorganisms only live where there is no oxygen.
Dimensions
- Phase 1 integrated biomethanation unit
- 5,000 to 10,000 L (5 to 10 m³) target
- Digester diameter
- coming soon
- Digester height
- coming soon
- Retention time of waste in the pilot
- coming soon
4 Gas-holder dome
Explain it simply
- What it does
- It is a balloon that fills up with the gas rising from the stomach.
- Where it sits
- Right on top of the digester, like a domed lid.
- Why it is there
- The gas is light: it rises on its own and collects at the top.
- Why it is needed
- It keeps the gas warm and safe until it is cleaned.
Technical details
- What it does
- Collects raw biogas above the digesting matter and evens out changes in volume.
- Where it sits
- Closes the top of the digester; the raw gas outlet leaves from its crown.
- Why it is there
- Biogas production is not constant; the dome absorbs the swings.
- Why it is needed
- It keeps the tank sealed; a mixer passes through the dome to stir the matter.
Dimensions
- Gas-holder dome volume
- coming soon
5 Digestate separation
Explain it simply
- What it does
- What is left after digestion is pressed out: a liquid on one side, fibres on the other.
- Where it sits
- At the digester outlet, on the field side.
- Why it is there
- What remains after digestion can still feed the soil.
- Why it is needed
- It is checked before use: nothing goes to the fields without control.
Technical details
- What it does
- Screw pressing of the digestate into a liquid fraction and solid fibres.
- Where it sits
- Downstream of the digester, on the digestate drain.
- Why it is there
- Separating the fractions makes them easier to store, check and spread.
- Why it is needed
- Digestate is checked before any return to the land; without that check, it is not spread.
Dimensions
- Separation equipment
- screw press target
- Dry matter of fibres after pressing
- 22 to 28 % target
- Liquid fraction
- nitrogen-rich fertiliser target
- Separation rate
- continuous, on digestate purge target
6 Storage
Explain it simply
- What it does
- It is a big soft cushion that fills up with gas.
- Where it sits
- Under the shed, in the shade.
- Why it is there
- It swells overnight and empties when cooking is under way.
- Why it is needed
- Thanks to it, there is gas when it is time to cook the attiéké.
Technical details
- What it does
- Low-pressure flexible gas bag, buffering production against consumption.
- Where it sits
- Under the metal-roofed shed, on a cradle, downstream of the dome.
- Why it is there
- Production is continuous; consumption is concentrated in cooking hours.
- Why it is needed
- It decouples production from use and keeps a steady flow at the burner.
Dimensions
- Purified biogas storage volume
- coming soon
7 Purification
Explain it simply
- What it does
- The gas goes through a cartridge filled with iron shavings.
- Where it sits
- Between the gas cushion and the kitchen.
- Why it is there
- The shavings trap the rotten-egg smell.
- Why it is needed
- Clean gas does not sting the eyes and does not damage the burner.
Technical details
- What it does
- Desulphurisation on regenerable iron filings; removal of condensed water.
- Where it sits
- Downstream of storage, upstream of the meter.
- Why it is there
- Raw biogas contains hydrogen sulphide, which is corrosive and foul-smelling.
- Why it is needed
- Only purified biogas reaches the burner; without purification, equipment corrodes.
Dimensions
- Purification flow rate
- coming soon
- Methane content of the pilot's raw biogas
- coming soon
8 Meter and burner
Explain it simply
- What it does
- The gas arrives under the attiéké pot. A meter measures what the site uses.
- Where it sits
- At the end of the line, close to the tank: the gas barely travels.
- Why it is there
- This is where the morning's peelings are put to work cooking.
- Why it is needed
- The meter says what the site pays: only the gas it uses.
Technical details
- What it does
- Volumetric metering with remote reading, then a burner set up for purified biogas.
- Where it sits
- Masonry hearth at the end of the line, on the processing site.
- Why it is there
- The gas is used on site: no compression, no bottling.
- Why it is needed
- Billing is by volume used; a burner tuned for biogas gives a steady flame.
Dimensions
- Use point power
- coming soon
- Raw biogas expected from a phase 1 unit
- coming soon
9 Remote monitoring
Explain it simply
- What it does
- It is the unit's health record. It sends news to a phone.
- Where it sits
- A small shelter with a solar panel, at the edge of the slab.
- Why it is there
- Like a thermometer, it tells us whether the stomach is doing well.
- Why it is needed
- We see straight away if something is wrong, without waiting for a breakdown.
Technical details
- What it does
- Sensors and transmission of operating data to the team.
- Where it sits
- Cabinet under a canopy, solar-powered, linked to the pH and temperature probes and to the meter.
- Why it is there
- Drifts in temperature, pressure or output signal a digestion going off track.
- Why it is needed
- It lets us step in early and document the results of every unit.
Dimensions
- Parameters monitored remotely
- coming soon
- Interval between two readings
- coming soon
From waste to flame
-
Organic waste
The site's residues are sorted. Only organic matter goes into the unit.
-
Biomethanation
Without air, microorganisms break the matter down. It stays in the unit for as long as that takes.
-
Biogas
What comes out is raw biogas. It is purified before any use.
-
Uses
Purified biogas is used for cooking. The digestate, once checked, can go back to the land.
In order of priority
What the unit changes
01 Environment
Waste no longer rots in the open. Its methane is captured instead of escaping.
02 Social
A gas flame gives off less smoke than a wood fire.
Running the unit takes staff on site.
03 Economy
- The site can cut what it pays to dispose of its waste.
- It can also buy less fuel.
Where the project stands
Done
A 600 L (0.6 m³) pilot has run. Its results were audited by a specialist firm in the sector.
Phase 1 · under way
We are selecting agri-food processing sites for the first 5,000 to 10,000 L (5 to 10 m³) unit. This stage takes 7 days at most.
5,000 to 10,000 L
i.e. 5 to 10 m³
Nature : target
7 days
Nature : target
Next
Then, selling biogas to gas-using small businesses, and equipping rural communities.
Do you process farm produce?
Your organic waste can become your cooking gas. Let's talk about your site.
Write to us