Evaluation of Net Energy Obtainable from Combustion of Stabilised Olive Mill By-Products

This work is aimed at calculating the energy content of the residues from olive oilproduction. Olive pulp, olive husk and sludge (a mixture of olive pulp and husk) have beenanalyzed separately. Olive Mill Effluents (OME) are normally a problem for olive millfarms, yet they may be used as feedstock for biomass-fuelled power plants. Nonetheless,OMEs are characterized by a relatively high humidity content and are produced only duringthe olive season. Thus, OME need a stabilization process to be employed as a solid biofuelthroughout the year. The analyses conducted attempt an evaluation of the energyconsumption of a three-stage stabilization process: drying, milling and pelletising. The netelectrical energy available from OME is then calculated as a difference between grossenergy available and energy consumed for stabilization. The gross available electricalenergy was calculated based on direct energy conversion of the stabilized feedstock on asmall scale direct combustion and Organic Rankine Cycle (ORC) turbine. Results show thatOME are suitable for energy production. Approximately 4500 kJ/kg of net electrical energymay be obtained out of olive sludge or olive pulp, while olive husk shows a potential grossenergy of 3400 kJ/kg.