Recently, a growing interest has emerged on the development of new and efficient energy sources, due to the inevitable extinction of the nonrenewable energy reserves. One of these alternative sources which have a great potential and sustainability to meet up the energy demand is biomass energy. This significant energy source can be utilized with various energy conversion technologies, one of which is biomass gasification in supercritical water. Water, being the most important solvent in nature, has very important characteristics as a reaction solvent under supercritical circumstances. At temperatures above its critical point (374.8 o C and 22.1MPa), water becomes more acidic and its diffusivity increases. Working with water at high temperatures increases the thermal reaction rate, which in consequence leads to a better dissolving of the organic matters and a fast reaction with oxygen. Hence, supercritical water offers a control mechanism depending on solubility, excellent transport properties based on its high diffusion ability and new reaction possibilities for hydrolysis or oxidation. In this study the gasification of a real biomass, namely olive mill wastewater (OMW), in supercritical water conditions is investigated with the use of Ru/Al 2 O 3 catalyst. OMW is a by0product obtained during olive oil production, which has a complex nature characterized by a high content of organic compounds and polyphenols. These properties impose OMW a significant pollution potential, but at the same time, the high content of organics makes OMW a desirable biomass candidate for energy production. The catalytic gasification experiments were made with five different reaction temperatures (400, 450, 500, 550 and 600C) and five reaction times (30, 60, 90, 120 and 150s), under a constant pressure of 25MPa. Through these experiments, the effects of reaction temperature and time on the gasification yield, gaseous product composition and OMW treatment efficiency were investigated. Catalyst, Gasification, Olive mill wastewater, Ru/Al 2 O 3 , Supercritical water. I. INTRODUCTION UPERCRITICAL water gasification (SCWG) has recently received much attention as a potential alternative to energy conversion methods applied to aqueous/non0aqueous biomass sources [1]0[3] or fossil fuels such as coal [4], [5], due to the unique physical properties of water above its critical conditions (374.8 o C and 22.1MPa). At supercritical conditions, water behaves both as an acidic and alkaline Ekin Kıpçak is with Yildiz Technical University, Department of Chemical Engineering, Davutpasa Campus, 34210 Esenler, Istanbul, Turkey (phone: 0090021203834728; fax: 0090021203834725; e0mail: eyildir@yildiz.edu.tr). Mesut Akgün is with Yildiz Technical University, Department of Chemical Engineering, Davutpasa Campus, 34210 Esenler, Istanbul, Turkey (e0mail: akgunm@yildiz.edu.tr). precursor for acidic or basic reactions on account of the higher concentrations of H 3 O + and OH − ions. This is due to the fact that the ionic product of subcritical and supercritical water at high pressures is some orders of magnitude greater than that of ambient water [6]0[8]. Therefore, supercritical water is considered both as a solvent for organic materials and as a reactant at processes such as the oxidative treatment of wastewaters, the gasification of aqueous organic solutions and production of fine metal oxide particles. Since organic compounds have complete miscibility and a high solubility in supercritical water due to its much lowered dielectric constant, chemical reactions with high efficiencies and without interfacial transport limitations can be obtained in the case of water0organic mixtures. Therefore, supercritical water offers a control mechanism depending on solubility, excellent transport properties based on its high diffusion ability, a low viscosity and new reaction alternatives for hydrolysis or oxidation [1], [9]. Energy production based on fossil fuels causes high import expenditures, environmental problems and a major consumption of the world’s nonrenewable energy reserves. Hence, a growing interest has emerged on the development of new and efficient energy sources. Biomass energy is among these sources, which can be utilized with various energy conversion technologies. One of these technologies is biomass gasification in supercritical water that has many advantages, such as high gasification efficiency and considerable amounts of flammable component production in the gaseous effluent during the process. Extensive investigations have been conducted in the recent years on this topic, which included model compounds such as glucose, cellulose, lignin and some real biomass compounds [1], [3], [10], [11]. In this study, the catalytic gasification of a real biomass, olive mill wastewater, was investigated. OMW is a by0product obtained during olive oil production, which is a fundamental economic activity for countries along the Mediterranean coast. OMW is generally composed of the water content of the olive fruit, water used to wash and process the olives, soft tissues from the olive pulp and a very stable oil emulsion [12]. The annual OMW production in the Mediterranean countries is estimated to range from 10 to 30 million m 3 . This quantitative diversity results from different factors such as the oil extraction method, cultivation soil, the use of pesticides and fertilizers, olive harvesting time, degree of ripening, duration of aging, olive variety and climatic conditions [13]. The typical OMW composition by weight is 83096% water, 3.5015 % organic compounds and 0.502% mineral salts. The organic Ekin Kıpçak, Mesut Akgün Catalytic Gasification of Olive Mill Wastewater as a Biomass Source under Supercritical Conditions S World Academy of Science, Engineering and Technology International Journal of Chemical and Molecular Engineering Vol:7, No:9, 2013 690 International Scholarly and Scientific Research & Innovation 7(9) 2013 ISNI:0000000091950263 Open Science Index, Chemical and Molecular Engineering Vol:7, No:9, 2013 publications.waset.org/16857/pdf