Mechanical-biological treatment of municipal solid waste has become popular throughout the UK and other parts of Europe to enable compliance with the Landfill Directive. Pretreatment will have a major influence on the degradation and settlement characteristics of the waste in landfills owing to the changes in the composition and properties of the wastes. This paper presents and compares the results of long term landfill behaviour of the UK and German MBT wastes pretreated to different standards. The gas generating potential, leachate quality and settlement characteristics are highlighted. The results reveal that it is possible to achieve stabilisation of MBT waste within a year and the biogas yield and leachate strength of German MBT waste was significantly reduced compared with the UK MBT waste. The settlement resulting from mechanical creep is more significant than the biodegradation induced settlement in both cases.
"The L 0 values of simulator tests were between 10 and 194 L/kg dry waste for a variety of waste compositions. The L 0 values of five simulator tests were below 30 L/kg dry waste, because of mechanically-biologically pretreatment of biodegradable waste (tests 8 and 9, Siddiqui et al. 2012), incomplete waste biodegradation (test 14, Staub et al. 2013) or because of the high percentage of non-biodegradable waste (tests 2 and 3, Fei et al. 2013). "
[Show abstract][Hide abstract] ABSTRACT: Methane (CH4) is generated during anaerobic biodegradation of municipal solid waste in landfills and can be collected as an energy source. CH4 generation rate (k) and potential CH4 generation capacity (L0) are two key parameters of the EPA LandGEM model used to estimate CH4 generation in full-scale landfills. These parameters can be measured in laboratory batch and simulator tests. The relationships of these parameters with waste composition - specifically, the percentages of biodegradable constituents - were investigated. k was positively correlated to the percentage of biodegradable constituents. L0 correlated well with volatile solids inthe waste. A k-L0 chart was developed to delineate the boundaries of CH4 generation rate and potential CH4 generation capacity during MSW biodegradation in laboratory tests. Waste composition and heterogeneity, moisture content and temperature likely contributed to the differences of k and L0 values obtained between batch and simulator tests.
Geo-Shanghai 2014; 05/2014
"The load, settlement , temperature, and biogas outflow were monitored and logged continuously. The gas measurement system is described by Siddiqui et al. (2009), and an initial discussion of some of the results (with a focus on leachate quality) is given by Siddiqui et al. (2012). Fig. 3 "
[Show abstract][Hide abstract] ABSTRACT: The legal limitations on the amount of biodegradable municipal solid waste (MSW) disposed of to landfill have led to the development of a range of pretreatment processes known generically as mechanical biological treatment (MBT). This paper presents the results of a detailed study of the degradation and settlement characteristics of two such MBT waste residues. The effects of mechanical creep and biodegradation are quantified separately, and compared with each other and with those for raw (untreated) MSW. The effects of different degrees of treatment prior to landfilling are considered in the context of the relationship between biodegradation and settlement. The results are discussed with reference to uncoupled models for estimating consolidation, creep, and biodegradation-induced settlements in MBT wastes. The methods for determining appropriate parameter values and applying these models to practice are also suggested. (C) 2013 American Society of Civil Engineers.
Journal of Geotechnical and Geoenvironmental Engineering 10/2013; 139(10):1676-1689. DOI:10.1061/(ASCE)GT.1943-5606.0000918 · 1.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mechanical biological treatment (MBT) is an effective technique, which removes organic carbon from municipal solid waste (MSW) prior to deposition. Thereby, methane (CH4) production in the landfill is strongly mitigated. However, direct measurements of greenhouse gas emissions from full-scale MBT landfills have not been conducted so far. Thus, CH4 and nitrous oxide (N2O) emissions from a German MBT landfill in operation as well as their concentrations in the landfill gas (LFG) were measured. High N2O emissions of 20-200gCO2eq.m-2h-1 magnitude (up to 428mgNm-2h-1) were observed within 20m of the working face. CH4 emissions were highest at the landfill zone located at a distance of 30-40m from the working face, where they reached about 10gCO2eq.m-2h-1. The MBT material in this area has been deposited several weeks earlier. Maximum LFG concentration for N2O was 24.000ppmv in material below the emission hotspot. At a depth of 50cm from the landfill surface a strong negative correlation between N2O and CH4 concentrations was observed. From this and from the distribution pattern of extractable ammonium, nitrite, and nitrate it has been concluded that strong N2O production is associated with nitrification activity and the occurrence of nitrite and nitrate, which is initiated by oxygen input during waste deposition. Therefore, CH4 mitigation measures, which often employ aeration, could result in a net increase of GHG emissions due to increased N2O emissions, especially at MBT landfills.
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