Background Olive oil is the principal source of fats in the Mediterranean diet and is credited with a range of health benefits. Its popularity supports a huge industry with around 3 million tonnes produced annually worldwide – 70% of it by EU countries, principally Spain, Italy and Greece. But production carries a significant environmental problem. The extraction process generates a dark effluent characterised by high organic carbon content, particularly phenols and polyphenols which are highly polluting. Treatment and disposal of this olive-mill waste is a major problem for Mediterranean producers. Around 30 million cubic metres of waste water are produced annually, during a three to four-month period. The presence of phenols make it difficult to purify. The compounds are not degraded by bacterial techniques, and anaerobic digestion allows for only 80 to 90 % COD removal, insufficient to permit effluent to be discharged into the environment. Many olive oil producers are small enterprises. They cannot afford the high capital costs of complex water treatment solutions. There is a danger that untreated or partly treated effluent will be discharged, with a resulting adverse effect on ground and surface water resources, soil quality and the heath of eco-systems. Objectives The OLEICO LIFE project was designed to establish a demonstration plant which would use a cost-effective and innovative approach to solving the problem of waste water in the olive oil industry. The new model would use natural resources to provide producers with an efficient, economical and environmentally friendly system to dispose of the waste. It would have the potential to increase profitability for these small to medium-sized businesses by reducing present treatment costs. Quite simple technology was to be involved, using the natural treatment technique of phytodepuration. This process is based on the interaction between plants, soil and micro-organisms. The project planned to excavate a pit close to an olive-oil mill. Waste water would be fed in and trees introduced to this artificial wetlands area. Pollutants from the water would be removed by the evapotranspiration process of the trees’ growth and the bacterial action of associated micro-organisms. Dissemination of the project’s results was seen as an important aim, in particular for information on the method to reach olive-grove farmers’ committees and a range of other organisations involved with oil production. An ambitious additional aim was to have the technique officially recognised and for it to become approved procedure within the legal framework. Results The project successfully constructed a pilot artificial plant which proved capable of treating 60 m3 of waste water per year at an Italian olive oil mill. Waste effluent was fed from the production plant to a 200m2 phytodepuration pit area where it was either taken up by trees or evaporated from the soil. Poplar trees were found to flourish despite the water’s toxicity, but cypress - also used in the early stages - died. The project continued using 24 poplars. All pollutants in the effluents were successfully degraded and no negative impacts on soil or water were detected. In addition, the system proved to work without the need for specialised manpower, was low on energy, did not require transport as there was a direct connection to the mill outflow, had no adverse impact on the landscape and generated a useable final product in wood for energy. It worked without chemical re-agents and there were no issues with odours. The beneficiary estimates that savings on previous treatment costs mean an economic pay-back time of six years for businesses investing in similar systems. The technique was granted a European patent during the project and proved so effective that the Italian Environment Ministry authorised the building of a full-scale plant based on the demonstrated characteristics. This is already up and running and another 30 organisations have expressed interest in introducing similar systems. There may also be possibilities for use with waste from farms, food factories or wine producers. Integration of the technique as an official procedure under Italian law has not yet been achieved but the Umbria region is seeking to explore the matter further. Some limiting factors have been identified: The system does not appear suitable for the large quantities of waste from the biggest producers, and visual impact may only be regarded as zero where poplars really fit the landscape.