Background The olive oil extraction industry is important for the Mediterranean region, especially Spain, Italy and Greece, the largest olive oil producers in the world. In the Mediterranean region, most olive oil mills (OOM) are small domestic enterprises scattered around the country. Owners are commonly unaware of the environmental risks of olive oil production and the availability of alternative waste treatment solutions. They are also often unwilling to bear extra costs for such alternatives. Therefore, the disposal of Olive Mill Wastes (OMW) on soil or in non-properly constructed evaporation ponds/lagoons is a common practice. The physical/chemical characteristics and the polyphenolic content of OMW pose serious threats to the environment. There is a need to identify and study potentially contaminated sites, document them in special national registries of contaminated sites and suggest and implement integrated technologies and practices that aim to recover the quality of affected systems. At the same time, it is essential to gain the acceptance and confidence of stakeholders and local communities. The application of soil protection/remedial methods could lead to soil remediation as well as the development and restoration of its functions. Objectives The PROSODOL project sought to protect soil and water quality from the wastes of olive oil mills in the Mediterranean region with the aim of contributing to the sustainable development of the olive oil producing industry. The project's main objectives were to: Develop and disseminate innovative, environmentally friendly, low-cost technologies for the protection of soil and water pollution from olive oil mill wastes; Establish an info-library/knowledge-base system for assessing the environmental impact of OOM wastes on Mediterranean regions; Promote the implementation of a Soil Thematic Strategy in OMW disposal areas; Design, implement and support a monitoring system for the assessment of the quality of soil and water directly or indirectly affected by OOM activities; Identify the safest uses in the agricultural sector of OMW and their potential recycling in the agricultural production. Results The PROSODOL project succeeded in developing an integrated approach to the problem of disposing OMW on agricultural soil. To do so the project developed a soil monitoring system which includes: An optimised set of soil quality indicators; Threshold values for soil quality indicators; A GIS based tool for the risk assessment of the OMW disposal sites; A system to facilitate decision-making; A land application system to ensure the safe disposal/use/application of OMW on soil; Software application tools for soil monitoring; A web GIS application for the interactive representation of surfaces indicating variations of different soil parameters such as pH, polyphenols; and An Inspire Geoportal accessible through the IMS-FORTH web GIS server (www.ims.forth.gr:8080/geoportal). PROSODOL also developed a monitoring system for water bodies and validated innovative methods for analysing olive waste. PROSODOL developed a low-cost OMW pre-treatment technology and applied it on a pilot scale. It also applied a bioremediation technology for soils contaminated by the disposal of such waste through in situ land treatment or land farming also on a pilot scale. The project foresaw the implementation of an integrated management system suitable for areas where olive oil mills' wastes are disposed, and includes: A practical low-cost waste pre-treatment stage with the use of active reagents; Application of soil remedial/protective techniques to improve soil quality; Practical small-scale composting procedure; and Controlled use of solid/liquid wastes in olive trees fertilisation. In summary, the project results included: An extensive analysis of soil quality was conducted in the area where the selected OMW disposal lagoons were located (it helped to develop specific soil quality indicators for the specific waste type); Risk assessment for soils in the vicinity of OMW disposal lagoons was also conducted. In order to effectively carry out these assessments, the project also developed a Soil Monitoring Tool to monitor basic soil parameters in areas affected by the disposal of waste and evaluate soil risk. The project then aimed to find the best soil remedial/protective techniques. It demonstrated methodologies for soil remediation and protection – i.e. bioremediation and zeolite application on soil. These practices, which are well-known worldwide, have never been implemented for OMW disposal areas. Thus, it was proven that there are low-cost methods for soil protection suitable for any Mediterranean country. Apart from the two demonstrated methods, the beneficiaries evaluated other available and known soil remediation methods and provided a useful guide on how to select the most appropriate one. After this step, the process was applied on a pilot scale at one of the five disposal areas of the municipality. In the Liguria region of Italy, young olive trees were grown under controlled conditions in dedicated containers. Two types of wastes were considered: solid and liquid or partially liquid wastes. Plants were periodically fertilised with processed olive oil wastes previously analysed for their chemical properties and constitution and composted with other leftover plant materials, such as organic wastes deriving from vegetable processing and/or field production, tree bark, gardening wastes, pruning wastes (including residues coming from olive trees). The effect on plant growth, yield, and soil physicochemical parameters, as well as the potential phytotoxic effect deriving from OMW application, was evaluated. Where positive outcomes were observed, the trials were repeated on a larger scale in some selected farms following common cultivation practices. These trials aimed to evaluate the environment impact and financial benefits for growers of establishing a small-scale virtual cycle of wastes within olive farms. Soil quality was monitored continuously during the entire duration of the pilot actions. The development of the monitoring systems was highly innovative, given that nothing similar had been devised prior to the project. The project also developed easy and rapid methods for determining OMW’s Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) values. The mill owners will be able to measure COD/BOD of their wastes in situ, thus enhancing waste management and safe disposal. The next step was to draw up a set of measures and strategies for monitoring and improving soil quality at OMW disposal areas. These measures should be considered by national policy makers in the Mediterranean region. For this reason, the project developed a legislative framework for the disposal and management of OMW in English, Greek, Italian and Spanish. PRODOSOL also developed guidelines (in English, Greek, Italian and Spanish) for the agronomic use of olive oil mill waste. Moreover, the project assessed the suitability of pre-treated waste for lettuce cultivation, as well as developing a methodology for co-composting OOM waste with other agricultural wastes and clinoptilolite. Further guidelines were drawn up for the potential use of waste in crop production based on soil characterisation. PROSODOL developed and continuously updates an info-library with open access to the public through the website of the project. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan, as well as in their publications (Good practices and Strategy document) (see "Read more" section).