Start-up test of an underground digester treating organic waste Kalloum Slimane Attaché de Recherche Unit of Research in Renewable Energies in Saharan Medium Adrar Algeria Kalloum_sli@yahoo.fr Djaafri Mohammed Attaché de Recherche Unit of Research in Renewable Energies in Saharan Medium Adrar Algeria Kaidi Kamel Technicien supérieur Unit of Research in Renewable Energies in Saharan Medium Adrar Algeria Khelafi Mostafa Attaché de Recherche Unit of Research in Renewable Energies in Saharan Medium Adrar Algeria Tahri Ahmed Chargé d’Etude Unit of Research in Renewable Energies in Saharan Medium Adrar Algeria Salem Fethya Chargé d’Etude Unit of Research in Renewable Energies in Saharan Medium Adrar Algeria Touzi Abdelkader Unit of Research in Renewable Energies in Saharan Medium Adrar Algeria Abstract— In this paper we studied the start-up of an underground digester with a useful volume of 4 m 3 in Saharan medium. 320 kg of waste taken from Adrar city slaughterhouses were treated during 60 days. During this study, we followed several parameters evolution such as: pH, volatile fatty acid (VFA), the temperature inside the digester, chemical oxygen demand (COD), pressure and the volume of biogas produced. The results obtained showed in the beginning of anaerobic digestion a fast drop in the pH. The VFA variation was inversely proportional to the pH variation. We noted a temperature decrease inside the digester during hydrolysis phase. Biogas inflammability was obtained since the 25 th day of digestion. The results showed also an organic mater reduction in order of 49%. Keywords- underground digester; anaerobic digestion; organic waste; biogas, VFA; COD I. INTRODUCTION Questions related to the solid waste final disposal and treatment constitutes one of the most serious problems faced by contemporary societies. The volume of waste has increased, and due to the lack of control and treatment alternatives and absence of regulations in developing countries, most of this material is disposed on open land, which causes serious environmental problems. Organic solid waste anaerobic digestion, especially urban solid waste organic fraction, is of great importance in solid waste management, because in most of the developing countries the fermentable organic solid waste represents the major fraction (50wt.%)[1]. Anaerobic treatment consists of organic material decomposition in the absence of free oxygen and produces methane, carbon dioxide, ammonia and traces of other gases and can reduce half of organic matter[2]. Anaerobic digestion is carried out in reactors called digesters, or bioreactors. Digesters are generally composed of a closed container, airtight and thermally insulated from the outside in which different microorganisms are joining together to degrade the substrate. The choice of the digester depends on the type of waste to be treated and the target application. There are several types of reactors such as upflow anaerobic sludge blanket (UASB) reactor, anaerobic packed-bed (APB) and underground reactors [3]. The latter is better adapted for developing countries because it is easy to build, does not require much maintenance and is the unless cost[4]. In this work we are interested in testing an underground digester built in the Renewable energy research unit in the Sahara medium in order to check its feasibility and its working. The results obtained were encouraging; we succeed digestion of slaughterhouse waste with a yield of organic matter removal of 49% and production of a combustible gas (biogas). 978-1-4244-8782-0/11/$26.00 ©2011 IEEE