Treating waste where it is produced

We install an integrated biodigester on the processing site. The waste no longer travels. The gas is made right next to the stoves.

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

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.

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

Raw biogas and purified biogas are not the same gas

Raw biogas

Raw biogas comes straight out of the digester. It is wet and contains a corrosive gas. It is not burned as it is.

Purified biogas

Purified biogas has had its water and hydrogen sulphide removed. This is the gas used for cooking. (Biomethane goes one step further: its carbon dioxide is removed too.)

Why it works on an attiéké site

The waste is already there: peelings and pressing water. No collection, no transport.
The site only pays for the gas it uses. The equipment stays with us.
Sensors monitor the unit remotely: any drift is corrected before it stops production.

Built for a humid tropical climate

A banded high-density polyethylene tank, resistant to UV and heat, on a masonry base.
Electronics and the solar panel sit under a canopy, sheltered from rain and overheating.
The gas is used on site: no compression, no cylinders, no costly wearing parts.

What is already established

A 600 L (0.6 m³) pilot has run; it is now complete.
Laboratory tests analysed the gas and the digestate.
The results were audited by a specialist firm in the sector.

The phase 1 unit

Volume: 5,000 to 10,000 L (5 to 10 m³).

5,000 to 10,000 L

i.e. 5 to 10 m³

Phase 1 integrated biomethanation unit

Nature : target

Scope: One unit, agri-food processing site
Method: Sizing chosen for phase 1

What the unit does not do

It does not treat plastics, metals or glass.
Its output depends on how much waste there is, and how regular the supply is.
It does not replace all of a site's energy; it covers part of it.

Phase 1 starts on agri-food processing sites. See the phases

Do you process farm produce?

Your organic waste can become your cooking gas. Let's talk about your site.

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