Computer simulation of gas generation and transport in landfills. III: Development of lanfills’ optimal model (original) (raw)
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The municipal solid waste (msw) is a source of landfill gas (msw)-with methane gas content. Preoccupations for landfill gas (msw) management date back since 1976 when, at a landfill (msw) in California (USA), it turned out practically that the landfill gas (msw) with methane gas content contains a gas with high caloric value that can be collected and used for economic purposes. The landfill gas (msw) contains methane gas (30% -60% volume), carbon dioxide (45% -50% volume), hydrogen sulfide and other gases. Methane gas, carbon dioxide, nitrous oxide and other gases are listed in Kyoto Protocol as high greenhouse gases. Their ecological-rational management is both a national and global preoccupation. In terms of greenhouse gases, especially methane gas, the landfill (msw) is held responsible for 3.5% -5% of the total global greenhouse gases. Practically, the quantitative estimation of the methane gas in a municipal solid waste landfill can be done by measuring the landfill gas (msw) flow in an extraction-collection well. In Romania, a quantitative estimation relationship of methane gas from deposits (msw) was made, approaching the problem in a different way. This paper presents the calculation formula, the working algorithm, the municipal waste landfill equation and the NOMOGRAMA of a municipal solid waste landfill (msw). The NOMOGRAMA allows us to define the values for parameter -m-(number of months needed for an amount of municipal solid waste (msw) to degrade, starting with the year from which the landfill gas (msw) emission with methane gas content is calculated). Taking into account the environmental conditions for each location of municipal solid waste landfill, the calculation uses various indexes and approximations, while the fundamental parameter remains -m-defined by the NOMOGRAMA of the municipal solid waste landfill (msw). A municipal solid waste landfill (msw) is a conglomerate of waste Journal of Geoscience and Environment Protection with various biodegradation periods between 2 -3 years and 5 -10 -30 years. Degradation of waste (msw) in to dissolved organic carbon will take place in a number of months defined -m-starting with the year from which the methane gas emission with the NOMOGRAMA of the municipal solid waste landfill (msw) is calculated. The -m-values for the year of the quantitative emission of methane gas can be also done analytically, which requires good experience in the ecologic-rational management of the municipal solid waste (msw).
Environmental Technology Modeling gas generation for Landfill
A methodology was developed to predict the optimum long-term spatial and temporal generation of landfill gases such as methane, carbon dioxide, ammonia, and hydrogen sulphide on post closure landfill. The model incorporated the chemical and the biochemical processes responsible for the degradation of the municipal solid waste. The developed model also takes into account the effects of heterogeneity with different layers as observed at the site of landfills morphology.
Modelling gas production in managed sanitary landfills
Waste Management & Research, 1988
Gas production and recovery from managed sanitary landfills can be simulated by describing the time and space variation of the total pressure and composition of the mixture of gases (CH 4 , C0 2 , and N 2) in the landfill . The variation of the total pressure and the composition of the gas mixture is described by the equations for mass conservation for each component (including a generation term for CH 4 and C0 2 ), the equation of motion, and the equation of state . Simulations of gas production compare well with field data from the Mountain View controlled landfill project field experiment . The function used to approximate the shape of the methanogenesis curve (based on equations describing the biochemical processes) consists of a rising hyperbolic branch and a decaying exponential branch . The conceptual framework of the model has been designed to incorporate equations describing the physics, biology, and chemistry of gas production in landfills .
Numerical Modelling of Generation and Transport of Gas and Heat in Landfills I. Model Formulation
Waste Management & Research, 1996
A mathematical model for the generation and transport of gas and heat in a sanitary landfill was developed based on earlier work on the Mountain View Controlled Landfill Project (MVCLP) in California, U.S.A. The present model incorporates biokinetic model equations describing the dynamics of the microbial landfill ecosystem into multi-layer, time-dependent transport and generation of gas and heat models. It is based on the fundamental principles governing the physical, chemical and microbiological processes in a porous media context such as a sanitary landfill. The model includes biochemical and temperature feedback loops to simulate the effects of their corresponding parameters on microbiological processes. The resulting integrated biokinetic, gas and heat generation and transport model was used to simulate field data from the MVCLP and to assess the sensitivity of model results to biological parameters. The model can be used to predict the rate and total production of methane in a landfill. The present work is presented in a series of three papers: (I) model formulation; (II) model application; and (III) sensitivity analysis * .
A coupled model for prediction of settlement and gas flow in MSW landfills
International Journal for Numerical and Analytical Methods in Geomechanics, 2009
Prediction of long-term settlement and control of gas pollution to the environment are two principle concerns during the management of municipal solid waste (MSW) landfills. The behavior of settlement and gas flow in MSW landfills is complicated due to the combined effect of mechanical deformation of the solid skeleton and continuous biodegradation of the waste. A one-dimensional settlement and gas flow model is presented in this paper, which is capable of predicting time evolution of settlement as well as temporal and spatial distribution of gas pressure within multi-layered landfills under a variety of operating scenarios. The analytical solution to the novel model is evaluated with numerical simulation and field measurements. The resulting efficiency and accuracy highlight the capability of the proposed model to reproduce the settlement behavior and gas flow in MSW landfills. The influences of operating conditions and waste properties on settlement and gas pressure are examined for typical MSW landfills. settlement becomes critical to the successful operation and further maintenance of the MSW landfills. Early models used to predict long-term settlement for MSW landfills are either adjusted from soil mechanics [1] or empirical functions based on best-fit approximation of field measurements . These models are used extensively in the practice for their simplicity. Abundant experiences have been accumulated in the determination of the model parameters.
Environmental Modeling & Assessment, 2010
A model to simulate gas, heat, and moisture transport through a sanitary landfill has been developed. The model not only considers the different processes that go on in a landfill but also the oxidation of methane in the final cover. The model was calibrated using published results and field data from a pilot scale landfill in Calgary. The model captures the physics of the different processes quite well. Simulations from the model show that waste permeability had a significant impact on the temperature, pressure distribution, and flux from a landfill. The presence of the final and intermediate covers enhanced the gas storage capacity of the landfill. Biodegradation of the waste was enhanced as the final cover minimized the atmospheric influences. In addition, the composition of landfill gas emitted to the atmosphere was significantly different from the composition of gas generated in landfill due to the presence of covers as some of the methane is oxidized to carbon dioxide. There was no significant benefit of using a final cover of higher depth. The presence and number of intermediate covers had an impact on gas flux and temperature distribution within a landfill.
A numerical model for methane production in managed sanitary landfills
Waste Management & Research, 1989
A mathematical model for the production and transport of biogenic gases in a landfill is developed based on earlier work on the Mountain View Landfill Project in California. The present model incorporates biokinetic model equations for the microbial landfill ecosystems dynamics in a multi-layer, time-dependent gas flow and production model. It is based on first principles of the physics, chemistry, and microbiological processes controlling the production and transport of biogenic gases in a porous media context such as a landfill. The model includes chemical/biokinetic feedback loops for chemical parameter influence on microbiological rate processes. The resulting integrated biokinetic/gas transport model is based on the first principles governing the biokinetics of municipal landfill environment, and the physics of gasmigration. The model was calibrated and verified using approximately 4 years of methane production data from the Mountain View Controlled Landfill Project. Hydrolysis rate appears to be the most sensitive parameter controlling gas generation production. The model can be used to predict the rate and total production of methane in a landfill .
Depsim: numerical 3D-simulation of the water, gas and solid phase in a landfill
International Journal of Sustainable Development and Planning, 2016
The model depSIM is a dump simulation model, which allows a detailed and time-scaled focus into the complex processes of a landfill. Description of the mechanical model: The biological, chemical and physical processes in the waste body are closely connected with each other and can be described mechanically. Therefore, a number of differential equations are needed and implemented in the model. The porous media body is examined under the acceptance of a compressible gas phase, a materially incompressible solid state, an organic phase and a liquid phase. For the verification of the numerical model the long-time behaviour (100 years) was simulated. Further details about the model and the mechanical background are summarized in Robeck, Ricken et Widmann: A finite element simulation model of biological conversion processes in landfills [1]. Use potentials: The developed model allows a differentiated, time wise and locally calculation and representation of the temperature, the organic conversion rate, the local pressure ratios and the gas current speeds. There were several case studies with the depSIM model in Germany which show the correlation between the temperature, gas production and gas potential. Therefore three different landfills were evaluated. Here, in the correlation between measured temperature in the landfill body and the temperature in the model was shown. The average divergence between both was less than 2 degree. By the detailed calculation of the gas speeds in every point of the dump an essential improvement arises compared with conventional arithmetic models for gas forecast and gas capture. These forecast models are based on estimated initial parameters. This allows only forecasts for a complete dump or a dump segment, but allows no coupled calculation of the relevant parameters. The model depSIM offers a spatially differentiated consideration of the gas production. However, just a spatially exact, quantitative forecast of the gas production is necessary for dump operator and authorities. The right forecast is elementary for the right dimensioning of the gas collection system and gas treatment and the possible use in combined heat and power units. All gas streams can be shown with the simulation model along the dump surface spatially and time wise differentiated. This allows a locally differentiated dump gas management with a division in areas with active or passive gas collection or to estimate the feasibility of a methane oxidation layer.
Numerical Simulation of the Radius of Influence for Landfill Gas Wells
Vadose Zone Journal, 2004
The physical properties of waste (e.g., density, porosity, saturation, permeability) largely influence gas migration In North America, most domestic waste produced is disposed in rates. Several studies treat physical properties of waste landfills. These sites generate leachate and gas, mainly CH 4 and CO 2 , which are harmful for the environment if not properly controlled.
Determination of first-order landfill gas modeling parameters and uncertainties
Waste Management, 2012
Using first-order kinetic empirical models to estimate landfill gas (LFG) generation and collection rates is well recognized in the literature. The uncertainty in the estimated LFG generation rates is a major challenge in evaluating performance of LFG collection and LFG to energy facilities. In this investigation, four methods for quantifying first-order LFG generation model parameters, methane generation potential, L 0 , and methane generation rate constant, k, were evaluated. It was found that the model is insensitive to the approach taken in quantifying the parameters. However, considering the recognition of using the model in the literature, the optimum method to estimate L 0 and k is to determine L 0 using disposed municipal solid waste composition and laboratory component specific methane potential values. The k value can be selected by model fitting and regression using the first-order model if LFG collection data are available. When such data are not available, k can be selected from technical literature, based on site conditions. For five Florida case-study landfills L 0 varied from 56 to 77 m 3 Mg À1 , and k varied from 0.04 to 0.13 yr À1 for the traditional landfills and was 0.10 yr À1 for the wet cell. Model predictions of LFG collection rates were on average lower than actual collection. The uncertainty (coefficient of variation) in modeled LFG generation rates varied from ±11% to ±17% while landfills were open, ±9% to ±18% at the end of waste placement, and ±16% to ±203% 50 years after waste placement ended.