Greek Olive Mills Face a Wastewater Squeeze
Greek olive mills can no longer simply pour their wastewater away: a new environmental law in force since April sets limits that more than half of the country’s mills cannot meet with the equipment they have. About 2,300 mills still use the older three-phase system. Here is what the law demands, why the old mills struggle, and why switching to two-phase is not the simple fix it looks like.
What happened
A report this week from Kalamata sets out the squeeze. Under the new law, most mills are for now spared the need for special environmental permits, but the limits on the organic load of their liquid waste have been cut drastically. That load is usually measured as biochemical oxygen demand, the oxygen needed to break down the organic matter, and the new ceiling is thousands of times lower than before. Treating the waste with lime, as many mills do, cannot get anywhere near it. Technology that can exists, but at a cost most mills cannot bear.
In practice, three-phase mills can no longer discharge their wastewater into any river, stream, pond or the sea. Their options are to hold it in purpose-built ponds and let it evaporate, or to clean it well enough to use for irrigation. Both are expensive and uncertain, and both need permits from the water authorities, who must be satisfied that the ponds do not leak and that the water is safe.
Why three-phase mills make so much of it
The difference is water. A three-phase decanter adds water to the olive paste and splits it into oil, solid pomace and a large stream of dark “vegetable water”. A two-phase decanter adds little or no water and sends the olives’ own water out with the pomace as a wet sludge. A technical guide from a Common Fund for Commodities and International Olive Council project puts the numbers side by side.
| Per ton of olives | Traditional press | Three-phase | Two-phase |
|---|---|---|---|
| Liquid waste or water in by-product | 450 to 650 liters | 850 to 1,200 liters | About 80 liters |
| Pomace produced | About 350 kg | About 500 kg | About 800 kg |
| Pomace moisture | 25 to 28% | 40 to 55% | 55 to 65% |
Why switching is not simple
- Two-phase moves the problem. It cuts the liquid waste but produces a heavy, wet pomace that must be dried before its residual oil can be extracted, which costs energy at the pomace plants.
- Mill owners like the old income. The Kalamata report says owners of an average mill, pressing about 50 tons of olives a day, earn more selling three-phase pomace than two-phase pulp, about €37,500 against €28,800 in its example, even though its figures show two-phase mills are more profitable overall.
- The crisis leaves no cash. Greek mills are already struggling through the economic crisis, and new equipment means borrowing at the worst possible time.
The report sees the season that starts in October as the test: how hard officials enforce the new limits, and whether the mills can comply.
Every olive mill in the Mediterranean has a wastewater story, and in many places it was simply a ditch. Stricter rules are overdue, but they fall hardest on the small village mills that press local growers’ olives, not on big industrial plants. If enough of them close, growers have to haul their fruit further, and olives that wait longer before milling make worse oil.
We covered one attempt to treat the waste in Pilot plant to treat olive vegetable water. For what happens to the pomace, see Light, Pure and Pomace: The Lesser Olive Oils, Explained, and for the village mill tradition, Family traditions and olive milling.
Sources
- Olive Oil Times: New Phase for Greek Olive Mills
- CFC and International Olive Council project CFC/IOOC/04: Good practice in vegetable water and compost spreading on agricultural land (archived PDF)