Exploring spatial and economic feasibility of olive mill wastewater disposal and reuse in sicily through GIS analysis

Olive mill wastewaters (OMWWs) present a substantial environmental challenge due to their high organic content. This study investigates sustainable OMWW management, focusing on field application, using a GIS-based approach to identify suitable areas in Sicily, Italy. Integrating regulatory, agronomic, hydropedological, and economic factors, the research offers a comprehensive evaluation of OMWW disposal strategies by explicitly linking spatial suitability to operational feasibility. The methodology included four phases: (I) identifying legally compliant areas; (II) agro-environmental suitability, assessing soil and environmental conditions; (III) economic suitability, based on a cost comparison between field application and transport to biogas plants; and (IV) final suitability mapping, locating olive oil mills with adequate land for OMWW disposal within defined service areas. Results showed 650,822.06 ha (25.19% of Sicily) were legally compliant, reduced to 216,368.98 ha (8.38%) after agronomic and hydropedological assessments. Economic analysis identified a break-even transport distance of 20 km, below which field application is more cost-effective than delivery to biogas plants. Mapping identified 553 mills (91.71%) with sufficient land for OMWW disposal within this threshold, while 50 mills (8.29%) lacked adequate areas and require alternative management solutions. By converting regulatory and environmental constraints into service-area polygons and introducing a quantified economic threshold, this study moves OMWW management from suitability screening to feasibility-oriented planning. These findings support targeted, cost-efficient, and environmentally sound strategies for OMWW reuse, providing practical guidance for policymakers and operators in Mediterranean olive-growing regions.