Role of Cover Systems to Control Methane Migration from Dumpsites
Publication: Journal of Hazardous, Toxic, and Radioactive Waste
Volume 24, Issue 4
Abstract
The emission of landfill gases from dump sites due to anaerobic biodegradation of waste is a matter of increasing public concern as they significantly contribute to global warming. In order to assess the methane emissions from dump sites and to quantify the effects of clay covers and geosynthetic clay liners (GCLs) in reducing them, numerical simulations were conducted. From the simulations, it was noted that clay covers reduced the atmospheric methane flux fourfold and GCLs produced a sixfold reduction in comparison to open dumps. Atmospheric methane fluxes far above the safe limit were observed for the open dumps, which were significantly lower when covers were in place. Development of large pressures owing to reduced migration and continuous methane production were also observed when covers were present. A study of the effect of geotechnical properties of cover and material types suggested that they affect methane emissions significantly. Absolute permeability, porosity, saturation, and van Genuchten properties influenced methane migration to a large extent and hence should be taken into consideration in a cover design.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article.
Acknowledgments
The study is part of the research from the Indo-Sri Lanka joint project, DST/INT/SL/P-13/2016 “Characterising landfill gas emissions: Experimental and numerical investigation (CLEAN),” funded by Department of Science and Technology, Govt. of India, which is gratefully acknowledged.
Notation
The following symbols are used in this paper:
- d
- diffusion coefficient;
- g
- gravitational acceleration (m · s−2);
- F
- Darcy flux (kg m2 · s−1);
- k
- intrinsic permeability (m2) = Kμ/ρg where, K = hydraulic conductivity (m · s−1); μ = dynamic viscosity (kg m−1 · s−1); and ρ = density of the fluid (kg m−3);
- kr
- relative permeability;
- M
- mass accumulation term (kg m−3);
- n
- outward unit normal vector;
- P
- total pressure;
- q
- mass flux (kg m−2 · s−1);
- S
- saturation;
- T
- temperature (°C);
- t
- time (s);
- V
- volume (m3);
- X
- mass fraction;
- β
- phase index (subscript);
- Γ
- surface area (m2);
- κ
- mass components (superscript);
- λ
- van Genuchten m;
- τ
- tortuosity; and
- φ
- porosity.
Subscripts and Superscripts
- g
- gas;
- l
- liquid;
- max
- maximum;
- Pcap
- capillary pressure (Pa);
- r
- residual;
- S
- saturation;
- w
- water; and
- 0
- reference value.
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Journal of Hazardous, Toxic, and Radioactive Waste
Volume 24 • Issue 4 • October 2020
Copyright
© 2020 American Society of Civil Engineers.
History
Received: Sep 24, 2019
Accepted: Feb 25, 2020
Published online: Jun 22, 2020
Published in print: Oct 1, 2020
Discussion open until: Nov 22, 2020
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