In this study, a fixed-bed downdraft gasifier (70 kWe–245 kWth) with gas cooling and cleaning system, combined with a gas engine, was tested using olive kernel as fuel. The primary scope of this paper is to identify the most prominent utilization paths for the solid residues of the process. After a 3-day experimental work and the respective sampling campaigns, a thorough characterization study was conducted: the mineralogy of collected residues was examined by means of XRD, Loss on Ignition tests were carried out by the use of TGA up to 850 °C, their morphology was examined by means of EDS-SEM, their energetic content and elemental composition were determined by means of proximate and ultimate analysis, respectively, while their major and trace metal characterization was conducted by means of AAS. Due to its high calorific value, relatively low moisture content, and high loss-on-ignition value, it has been concluded that the olive kernel gasification residue can be utilized as a primary fuel in combustion boilers. Moreover, its reduced chlorine and sulfur content suggest minimal corrosion-related problems. Alternative utilization options, based on their morphology, are also suggested in this study, while modifications in the current gasification conditions are proposed as well.

Keywords:Gasification, Biomass, Olive Kernel, Bottom ash, X-ray diffraction (XRD),Scanning electron microscopy (SEM)