This paper deals with the use of simplified methods to predict methane generation in tropical landfills. Methane recovery data obtained on site as part of a research program being carried out at the Metropolitan Landfill, Salvador, Brazil, is analyzed and used to obtain field methane generation over time. Laboratory data from MSW samples of different ages are presented and discussed; and simplified procedures to estimate the methane generation potential, Lo, and the constant related to the biodegradation rate, k are applied. The first order decay method is used to fit field and laboratory results. It is demonstrated that despite the assumptions and the simplicity of the adopted laboratory procedures, the values Lo and k obtained are very close to those measured in the field, thus making this kind of analysis very attractive for first approach purposes.

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International audienceOriginal laboratory setups are used to study the moisture retention properties of municipal solid waste taking into account the porous medium's structural evolution due to compression. A controlled suction oedometer allowed the moisture retention curves (MRCs) of compacted samples to be determined for both wetting and drainage with a matric suction range of 0 to 10 kPa. Another setup utilizing an extraction plate was used to determine a drainage MRC for a non‐compacted sample with matric suction varying from 0 to 450 kPa. The experimental results demonstrated the complexity of MSW porous medium compared to soil. The MRC of lightly and uncompacted samples did not exhibit a measurable air‐entry suction. Moreover, significant hysteresis between the wetting and drainage MRCs was observed. The experimental MRCs were interpreted with two different models, and a pore size distribution evolution with compression was proposed. Finally, the concept of field capacity in relation to the moisture retention properties is discussed

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The use of geotextiles as filters involves the prior determination of filter criteria. The filtration opening size, Of, is used as characteristic geotextile parameter for the retention criterion. Until now, Of has been determined by an experimental procedure. In this paper, the authors propose a theoretical approach, based on a structural model applied to nonwoven geotextiles. The geotextile is modelled on the basis of the Poissonian polyhedra method, and the distribution of “conduits” passing through the geotextile is defined and evaluated. Once the textile structure has been modelled, particular attention is given to the hydrodynamic sieving test, which provides a means of measuring Of. A theoretical approach is used to simulate cyclic test conditions and to propose a parametric study for optimizing test conditions. This theoretical approach is systematically supported by an experimental validation. The proposed method is the first of its kind to provide a realistic means of forecasting the filtration opening size of nonwoven geotextiles.