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Annually, the olive oil industry generates a significant amount of by-products, such as olive pomace, olive husks, tree prunings, leaves, pits, and branches. Therefore, the recovery of these residues has become a major challenge in Mediterranean countries. The utilization of olive industry residues has received much attention in recent years, especially for energy purposes. Accordingly, this primary experimental study aims at investigating the potential of olive biomass waste for energy recovery in terms of synthesis gas (or syngas) production using the thermal arc plasma gasification method. The olive charcoal made from the exhausted olive solid waste (olive pomace) was chosen as a reference material for primary experiments with known composition from the performed proximate and ultimate analysis. The experiments were carried out at various operational parameters: raw biomass and water vapour flow rates and the plasma generator power. The producer gas involved principally CO, H 2 , and CO 2 with the highest concentrations of 41.17%, 13.06%, and 13.48%, respectively. The produced synthesis gas has a lower heating value of 6.09 MJ/nm 3 at the H 2 O/C ratio of 3.15 and the plasma torch had a power of 52.2 kW.

This investigation has established a complete environmentally friendly strategy for the valorization of olive mill wastewater (OMW). This valorization process includes different steps, namely, OMW impregnation on sawdust, drying, biofertilizer production, and soil amendment. The OMW impregnation on raw cypress sawdust (RCS) was performed using batch procedure mode. During this impregnation, 59% and 71% of the chemical oxygen demand and total dissolved salts of OMW were adsorbed on RCS. The drying of the impregnated sawdust (IS) and OMW was realized in a convective dryer at temperature ranging between 40 and 60 °C and air velocity ranging between 0.7 and 1.3 m/s. Comparison between both samples demonstrated clearly that the impregnation procedure accelerated the drying process and consequently allowed an ecologic recovery of water from OMW that could be reused. The IS sample was pyrolyzed at 500 °C for green fuel (bio-oil, gas) and char production. This residual char (IS-Char) exhibited higher mass fraction of 34.5%. The IS char characterization showed the presence of important nutrients (potassium, nitrogen, and phosphorus) contents. The application of the IS char as a biofertilizer for rye-grass growth studies under controlled conditions showed promising results in terms of leaf dimensions and mass yields of the plant. These preliminary results indicated the validity of the established strategy to convert OMW from a pollutant to green fuels, agricultural water source, and biofertilizer.