Producers in Greece Generate Electricity with Olive Mill Wastewater

Producers can save money and be more sustainable by shipping olive mill wastewater to local biogas production plants.

Following the production of biogas from livestock waste, anaerobic digestion technology is now emerging as a solution for managing olive mill wastewater in Greece.

With the first biogas plants now processing liquid waste produced through olive oil extraction, a small group of olive oil producers in northern Greece can rid themselves of the responsibility of disposing of the toxic material while contributing to the production of green energy.

However, there are still some challenges involved. The quantities of olive mill wastewater currently feeding biogas plants are extremely low in relation to the total amount produced across the country.

However, experts point to Italy, suggesting there are similar prospects for applying the technology to those of their neighbour. 

No Need for Evaporation Tanks

For the Kyklopas SA olive mill, in Evros, in northeastern Greece, the disposal of olive mill waste for biogas production is a welcome solution in the management of the toxic residues.

“Our cooperation with the production unit of Biogas Komotini SA has taken a burden off our backs,” Niki Kelidou, of Kyklopas SA, said. “Despite the fact that we have a license to dispose of the residue in our unit, the management of wastewater is a job that requires significant effort and costs as the quantities we produce are high.”

The family-owned olive mill produces 3.4 million litres of liquid wastewater annually as a byproduct of its annual production of 260 tons of olive oil.

“The cost of building the reservoir where the liquid waste was deposited for evaporation was €40,000 (AUD$6,958.00) and we built it just two years before we started collaborating with the biogas plant,” Kelidou said. “Had we struck the deal earlier, we would not have built the tank.”

In addition to construction costs, the maintenance of the discharge basin incurs additional expenses.

“Every two to three years, the tank must be emptied and the thick sludge has to be scraped,” Kelidou said. “Moreover, we incurred transport costs because the tank is located at a distance of 20 kilometers from the olive mill.”

An additional factor that enabled the cooperation with the biogas plant is the short distance that separates them, which keeps transportation costs relatively low.

“The Komotini biogas plant is only 50 kilometers from the mill,” Kelidou said. “This is crucial because, during the operation of the mill, about five tanks are loaded on a daily basis and transported to the biogas plant.” More