A new sorting method produces more accepted coffee per labour hour. That sounds like a clear improvement—until the cooperative discovers that the same incoming lot took longer to finish and left less coffee meeting the agreed grade. Those outcomes can all be true at once.
FAO’s new sourcebook announcement prompted us to read the machinery chapter itself. In chapter 7 of Optimization and minimization, productivity sits alongside access, timely operations and the support needed to keep equipment working. A cooperative comparison needs that wider view.
One lot, three different measures
Consider this invented training exercise. Each method handles a comparable 1,000 kg lot of green coffee. The same acceptance specification is applied; rejected material is recorded separately. Everyone works for the full stated period. These are arithmetic inputs, not a measured machine trial or a recommendation to reject a particular share of coffee.
| Measure | Method A | Method B |
|---|---|---|
| Incoming green coffee | 1,000 kg | 1,000 kg |
| People × elapsed time | 5 × 2 hours | 3 × 3 hours |
| Total labour | 10 person-hours | 9 person-hours |
| Coffee meeting the specification | 900 kg | 850 kg |
| Accepted coffee per person-hour | 90 kg | About 94.4 kg |
| Accepted share of the incoming lot | 90% | 85% |
Method B improves the labour ratio by about 4.9%. It also produces 50 kg less accepted coffee and occupies the process for an extra hour. “More productive” describes one column; it does not settle the decision.
Nor does the table explain why the accepted quantity differs. Possible causes would need investigation against real records. The example deliberately holds the written specification constant; it does not claim that two actual incoming lots have identical quality.
The bottleneck decides which improvement matters
If available labour is the limiting resource, saving a person-hour may be valuable. If a dispatch depends on finishing within two hours, a three-hour process creates another problem. If accepted volume is scarce, losing 50 kg may outweigh the labour saving. Prices, operating costs and the destination of rejected material are missing here, so the table cannot establish profitability.
Ask the group to make its constraint explicit before voting for a method. “We need the most accepted coffee before collection” is a different objective from “we need to complete this task with three people”. A useful trial is designed around the actual objective.
The machine does not arrive alone
FAO’s chapter discusses barriers including access to finance, suitable equipment, after-sales support and repair capacity. That makes the equipment offer wider than a rated throughput. For a proposed cooperative purchase or hire, identify who can operate it, which work its quoted rate includes, how servicing is arranged and what happens during downtime.
These questions become concrete beside the trial record: setup and cleaning belong somewhere; moving a task outside the measured interval does not make the work disappear. Preserve the product form and lot identity through the comparison, using the same principles as our coffee-lot records guide.
For a training session, ask each group to choose A or B under one stated constraint, then change that constraint. If the answer changes, the exercise has done its job: a ratio has become part of a decision instead of a substitute for one.
Reading scope: FAO, 2026, Optimization and minimization – Towards sustainable plant production, chapter 7, especially printed pages 154–160. The coffee exercise and calculations are our own; FAO has not tested or endorsed them. No real equipment performance or agronomic outcome is claimed.