Rural drying centre network — Mali design scenario
Bring the processing to the fruit.
A hub-and-spoke network of small drying centres across Mali’s mango regions, each built around a 200,000 kcal/h burner and two chambers. Processing goes to the fruit rather than the fruit to a central plant, with one shared protocol so output from any centre is interchangeable to a buyer.
Mali presents a geography problem more than a technology problem: cultivation scattered across a wide area, poor roads, limited electricity, severe post-harvest losses, and producers without capital for individual investment.
The approach — hub and spoke
Rather than one large central facility — which would require moving fruit long distances over poor roads, defeating the purpose — the design deploys multiple small processing centres located in the growing areas themselves.
- 200,000 kcal/h burners at each site, appropriate to village-level operation.
- Two-tunnel configurations per centre.
- Standardised quality protocols identical across all locations, so output from any centre is interchangeable to a buyer.
- Centralised marketing — collective sales aggregating volume for negotiating leverage.
Projected outcomes (modelled design targets)
- Multiple processing centres serving a large number of producers.
- Substantial reduction in post-harvest loss across project areas.
- Meaningful average income increase for participating farmers.
- Reduced rural out-migration through local opportunity.
- Development of local technical expertise.
Principles we design around
Local ownership drives maintenance discipline in a way contracted management does not. Scale must match local production, not aspiration. Quality consistency across sites is what makes collective marketing possible — one bad centre discredits the whole network. And regular exchange between centre operators is, by design, the most effective ongoing training mechanism.
What this scenario is
A costed design we are ready to build, not a delivered project. GreenMach has one commissioned installation — a cashew shell burner firing a steam boiler at PCCL in The Gambia — and no drying line, and no network, has been built yet.
The centre count and the per-centre volume below are assumptions. They would be set from real production mapping across the growing areas before anything is manufactured.
One centre, item by item
| Item | Specification |
|---|---|
| Burner | 200,000 kcal/h, appropriate to village-level operation |
| Hot air generator | Double chamber, three-pass, indirect exchange |
| Chambers | Two, standard tunnel format at 1,500 kg fresh per batch |
| Control | PLC with a fixed recipe set — identical at every centre |
| Product contact | SS 304 trays, wagons and wearing decks |
| Protocol | One written procedure, the same at every site |
| Marketing | Centralised, aggregating output across centres |
How a centre would be sized
The method is the one set out for Banfora, run at village scale. The difference is that the sizing question is answered twice: once for a single centre, and once for how many centres a growing area needs.
The efficiency chain is the same wherever the equipment sits: combustion 0.85 × hot air generator 0.78 × ducting 0.95 × envelope 0.97 × exhaust 0.68, multiplying to 0.415 and carried at 0.40. A small burner does not get a worse chain; it gets a smaller one.
Centre count is set by haulage distance rather than by tonnage. Fruit that has travelled two hours on a poor road arrives bruised and part-fermented, and no drying regime recovers it — so the network is laid out around how far fruit can move before it stops being export-grade, and the chambers follow.
What we would need to confirm on site
The network questions come before the equipment questions, and three of the four below are not engineering.
- Production mapping. Where the fruit actually is, week by week, and how far it can travel before quality is lost. This sets the number of centres and their locations.
- Who owns each centre. Local ownership drives maintenance discipline in a way contracted management does not. It is the single strongest predictor of whether a centre is still running in year three.
- Fuel at each site. Shell availability varies across the growing areas. Some centres may need to be specified for a residue mix from the outset rather than retrofitted later.
- The buyer for aggregated volume. Collective marketing only works if a buyer wants the aggregate. One centre off-protocol discredits the whole lot.
Modelled design targets, not measured results
These are modelled design targets for this configuration, not measured results — we have not yet built this network.
Frequently asked questions
Why many small centres rather than one large plant?
Because the constraint is the road, not the equipment. A central plant means moving fruit long distances over poor roads, and fruit that arrives bruised after two hours cannot be dried back to export grade. Two chambers at 1,500 kg in the growing area beats twelve chambers two hours away.
What keeps quality consistent across separate sites?
One written protocol and one fixed recipe set, identical on every PLC — mango at 65 to 70 °C on a 16 to 20 hour cycle, the same at every site. Operators are not asked to tune locally. A centre that drifts to its own settings produces output that cannot be aggregated, and one such centre discredits the network.
Is a 200,000 kcal/h burner less efficient than a large one?
No. The efficiency chain is the same five terms and the same 0.40 overall, because the losses are proportional rather than fixed. What a small burner does change is fuel handling: the same daily ash removal and cleaning discipline applies, spread across more sites and more operators.
Planning a distributed network?
We standardise the protocol so every centre’s output is interchangeable to buyers.
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