Resources, Conservation and Recycling 54 (2010) 271–277 Contents lists available at ScienceDirect Resources, Conservation and Recycling journal homepage: www.elsevier.com/locate/resconrec Thermal degradation of olive solid waste: Influence of particle size and oxygen concentration Ajmia Chouchene a,b , Mejdi Jeguirim a,∗ , Basma Khiari b , Fathi Zagrouba c , Gwénaëlle Trouvé a a Laboratoire Gestion des Risques et Environnement, 25 rue de Chemnitz, 68 200 Mulhouse, France b Laboratoire d’Energétique et des Procédés Thermiques, CRTE Technopole de Borj-Cedria B.P. 95, 2050 Hammam-Lif, Tunisia c Institut Supérieur des Sciences et Technologies de l’Environnement, Technopole de Borj-Cedria B.P. 95, 2050 Hammam-Lif, Tunisia article info Article history: Received 7 November 2008 Received in revised form 1 April 2009 Accepted 8 April 2009 Keywords: Biomass Olive solid waste Pyrolysis Oxidation Thermogravimetry Kinetics abstract The aim of this work is to study the effect of the particle size and the oxygen content on the thermal degra- dation of olive solid waste (OSW). Thermogravimetric analyses of different particles sizes (0.5–2.8 mm in diameter) were performed. Three different atmospheres were used: on the one hand, an inert atmosphere (N 2 ) in order to study the pyrolysis of the olive solid waste and on the other hand two oxidative atmo- sphere (10% O 2 /N 2 ; 20% O 2 /N 2 ). Pyrolysis under oxidative conditions (10% O 2 /N 2 ; 20% O 2 /N 2 ) takes place according to three stages: drying, volatiles emission and char oxidation whereas in the case of pyrolysis under inert conditions only the two first stages occur. Loss of humidity and volatiles are independent of the oxygen concentration. However, the initial temperature of char oxidation is decreasing with the increase of oxygen concentration. Weight loss profiles as well as CO and CO 2 emission rates during the oxidative pyrolysis are depending on the particle size of OSW. In fact, thermal degradation and emis- sion rates of carbon oxides emissions proceed at lower temperatures for the smallest particle size. The temperature ranges of volatilization and char oxidation as well as the amount of remaining ash are also depending on the particle size. Reaction kinetic parameters are obtained under inert and oxidative conditions using global independent reactions model and compared with other biomass. Activation energy and preexponential factor of the devolatilization step increase with oxygen concentration. However, the reaction order was not affected by the variation of the oxygen concentration and the particle size with a value between 0.6 and 0.8. © 2009 Elsevier B.V. All rights reserved. 1. Introduction The continuous increasing of energy consumption in all eco- nomic sectors leads to the emerging of new sources of energy. Biomass in general and agricultural waste in particular seems to be a realistic alternative power generation leading to environmen- tal, technical and economical benefits (Bridgewater, 1995; Sami et al., 2001; Abu-Qudais, 1996; Dornburg et al., 2006; Prasad et al., 2007). In Mediterranean countries, olive solid waste seems to be a promising energy source to mitigate greenhouse gas emissions. On one hand, their thermal valorisation eliminates them and on the other increases the exploitations output and decreases their production costs. With high heating values, agricultural biomass offers number of advantages compared to fossil fuels. Biomass is regarded as a renewable energy source with zero to low CO 2 emissions. Ther- ∗ Corresponding author. Tel.: +33 3 89327658; fax: +33 3 89327661. E-mail address: mejdi.jeguirim@uha.fr (M. Jeguirim). mal utilization of waste and residual materials as OSW, along with reducing the CO 2 emissions helps to solve the waste disposal prob- lem. Gradual introduction of increasingly restrictive legislations on emissions from combustion sources has been increasing the inter- est in biomass combustion (Gogebakan et al., 2009). Biomass for combustion in industrial-scale combustors must meet a number of criteria, including availability throughout the year to ensure secu- rity of supply, high density to minimize transport costs and exhaust control (Kazagic and Smajevic, 2009). Indeed, the combustion of this waste produces effluents charged with organic acids, nitrogen oxides, sulphur oxides, tar and fine particles of carbon, which are carcinogens and very prejudicial in vicinity. Furnaces and boilers performances are not well known yet, particularly with regard to the corrosion related to the com- bustion emanations. If economic aspect is simple to approach, few references make it possible to consider the technical and the envi- ronmental impacts of these practices. One of the economic stake of this study is to be able to contribute to the technical knowledge (such the ageing of the installation) and then to the calculation of the economic profitability of the bioenergy field. It seems therefore necessary to have reliable knowledge concerning these pollutants 0921-3449/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.resconrec.2009.04.010