Anaerobic digestion has been up to now essentially applied to wastewater. However, anaerobic treatment of organic solid waste fits in well with the new requirements for waste management. The Valorga full-scale plant in Tilburg (the Netherlands) is designed to process 52,000 tons per year of organic municipal solid waste separately collected. The Valorga digestion process is a semi-continuous, high-solid, one-step, plug-flow type process. The main characteristic is the complete absence of any mechanical equipment inside the reactors. The waste to be treated consists of food and garden waste. The characterization of the waste stream revealed a seasonal fluctuation in quantity and quality, that was correlated with seasonal garden waste production. The methane yield is varying from 210 to 290 m3 STP per Mg of volatile solids. It is related to waste composition. During the slack winter period the waste contains proportionally more food waste that is more biodegradable than lignocellulosic garden waste. The biological process was stable based on volatile acidity, alkalinity and ammonia measurements in the effluent. The organic residue, after dewatering and storage under aerobic conditions, can be considered as soil conditioner.

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