Characterization of Olive Waste Ashes as Fertilizers

Wet and dry olive cakes are the most important wastes generated when olive oil is produced. In recent years, both olive wastes have been incinerated to produce electricity, and thereby large amounts of fly and bottom ash are generated. In this study, physical, physicochemical, and chemical characteristics of olive waste ashes produced in Andalusian biomass power plants were analyzed to evaluate their suitability for agriculture. High variability among fly and bottom ashes may be ascribed to the origin of the olive waste and the combustion temperature. Waste olive ashes, which contained all particle sizes, showed high values of pH, salinity, water holding capacity, calcium carbonate equivalent, and P, K, Cu, and B contents. In contrast, moderate values were recorded for Ca, Mg, Zn, and Ni. Nitrogen is scarce in olive waste ashes; they thus can only be part of any fertilization strategy.