Study on landfill gas migration in landfilled municipal solid waste based on gas–solid coupling model

Abstract

Gas migration rule is of great significance to the safe disposal of landfill. In this article, a gas–solid coupling model was developed and used to simulate the effects of various factors on gas migration. The simulation results showed that gas pressure in landfill decreased with the increase of extraction pressure, anisotropy ratio, coverage gas permeability, extraction well depth, and coverage thickness. The maximum value of gas pressure could reach 683 Pa. Among these factors, extraction pressure played the largest role in the gas pressure, while coverage thickness played the smallest role in it. The radius of influence (RoI) and gas flow rate increased with the increase of extraction pressure, refuse gas permeability, coverage thickness, and the extraction well depth, but with the decrease of coverage gas permeability. The effect of extraction well depth on RoI and gas flow rate was the most significant. When extraction well depth increased from 0.5 landfill height to 0.9 landfill height, the maximum values of RoI and extraction volume increased by 20 m and 20 m3/hr, respectively. It was suggested that the design of landfill gas (LFG) collection system should consider the influence of various factors in practical engineering.

Design of gas collection systems: Issues and challenges

“…Work done Townsend et al (2005) Developed one-dimensional (1D) gas flow model for horizontal GCS Tinet and Oxarango ( 2010) Proposed an axis-symmetric unsteady Laplace equation to analyse gas pressure distribution Liu et al (2011) Estimated gas and water pressure distributions by solving the governing equations of a proposed liquid-gas fluid migration theory Li et al (2012) Developed a gas pressure model for layered MSW landfills Li et al (2013) Presented a 1D transient analytical solution for gas pressure profiles in MSW layers Xi and Xiong (2013) Estimated gas pressure distribution in landfills with numerical modelling Feng et al (2015) Developed a two-dimensional model for estimating the gas pressure distribution Shi et al (2016) Modelled gas pressure distribution in landfills by extending the symmetric theory of gas migration Ni and Ng (2019) Estimated the effect of grassroots on gas permeability and hence the pressure distribution in a simulated landfill Zeng (2020) Estimated gas pressure distribution with a developed gas-solid coupling model Zheng et al (2020) Estimated gas pressure distribution below landfill covers with analytical methods GCS: gas collection system; MSW: municipal solid waste. was also imposed on the top element to simulate atmospheric conditions, as mentioned in Table 3.…”

“…Gas collection systems (GCS) can capture 60% to 90% of the produced landfill gases (Larson et al, 2021;USEPA, 2017). The critical parameters in the design of a GCS (active and passive) include the radius of influence (ROI), suction pressure, number of wells and their spacing (Feng et al, 2017;Zeng, 2020;Zheng et al, 2018Zheng et al, , 2019. One of the issues existing in relation to the design of a GCS is the interpretation of the ROI for a gas extraction well (GEW) in the literature.…”

A Temperature-Controlled Apparatus for Gas Permeability under Low Gas Pressure

“…Among these fields, the increase in gas pressure above atmospheric pressure is typically below 10 kPa and falls within the measurement range of the gas supply equipment (20 kPa). In the field of landfill, the gas pressure generated by anaerobic decomposition of organic waste under the cover system is usually less than 10 kPa [16]. Likewise, in the agricultural field, the applied gas pressure for measuring soil permeability is recommended to be lower than 8 kPa (that corresponds to a single water column of 0.80 m high) [7].…”

Analytical Solution for One-Dimensional Gas Pressure Distribution Considering the Variation of Gas Permeability Coefficients with Burial Depth

“…The model analyzed the effects of the gas generation rate, intrinsic permeability coefficient, intermediate cover layer, high-permeability horizontal permeable layer, and landfill gas drainage channel on the gas pressure distribution. Analytical solutions for the gas migration process through layered MSWs have also been proposed in Zeng [27], Zhang et al [28], and Wu et al [29].…”