Landfill gas distribution at the base of passive methane oxidation biosystems: Transient state analysis of several configurations

Abstract

The design process of passive methane oxidation biosystems needs to include design criteria that account for the effect of unsaturated hydraulic behavior on landfill gas migration, in particular, restrictions to landfill gas flow due to the capillary barrier effect, which can greatly affect methane oxidation rates. This paper reports the results of numerical simulations performed to assess the landfill gas flow behavior of several passive methane oxidation biosystems. The concepts of these biosystems were inspired by selected configurations found in the technical literature. We adopted the length of unrestricted gas migration (LUGM) as the main design criterion in this assessment. LUGM is defined as the length along the interface between the methane oxidation and gas distribution layers, where the pores of the methane oxidation layer material can be considered blocked for all practical purposes. High values of LUGM indicate that landfill gas can flow easily across this interface. Low values of LUGM indicate greater chances of having preferential upward flow and, consequently, finding hotspots on the surface. Deficient designs may result in the occurrence of hotspots. One of the designs evaluated included an alternative to a concept recently proposed where the interface between the methane oxidation and gas distribution layers was jagged (in the form of a see-saw). The idea behind this ingenious concept is to prevent blockage of air-filled pores in the upper areas of the jagged segments. The results of the simulations revealed the extent of the capability of the different scenarios to provide unrestricted and conveniently distributed upward landfill gas flow. They also stress the importance of incorporating an appropriate design criterion in the selection of the methane oxidation layer materials and the geometrical form of passive biosystems.

Medidas De Fluxo De Dióxido De Carbono E Metano Em Um Depósito De Resíduos Insalubre Na Amazônia

“…These results confirm the enormous spatial variability of gas fluxes in the Aurá dump, which shows an uneven residue distribution (AHOUGHALANDARI; CABRAL, 2017b;RÖWER et al, 2011). The variogram is an essential tool in a geospatial analysis, determining the amount of spatial dependence (autocorrelation) in the spatial data underlying the variations (SPOKAS et al, 2003).…”

“…Both flux measurements showed large variability, with CO 2 fluxes ranging from 61.69 to 1,655.43 g m -2 d -1 (coefficient variation -CV = 140.99%), and CH 4 fluxes ranging from 2.77 to 455.95 g m -2 d -1 (CV = 67.04%). These results confirm that the surface emissions in dumps are not uniform, with paths of lower resistance, creating hotspots (AHOUGHALANDARI; CABRAL, 2017b;ALLEN et al, 2019;GONZALEZ-VALENCIA et al, 2016;RACHOR et al, 2013). It is possible that emission areas have a higher air-filled porosity or improved pore connectivity compared to the larger dump area (BIAN et al, 2018b;RACHOR et al, 2013), resulting in preferred pathways for gases.…”

“…However, the results for the gas emissions indicated that the non-spatial variability was high in comparison with the spatial variability. Most studies show intense spatial variability (ABUSHAMMALA et al, 2016;CABRAL, 2017b;CHANTON et al, 2011;DI TRAPANI et al, 2013). However, if the variables had been studied in greater detail, the heterogeneity defined as non-spatial variability may have exhibited a spatial structure.…”

“…Current estimates from the Intergovernmental Panel on Climate Change (IPCC) for the annual CH 4 emissions from landfills range from 67 to 90 Mt CH 4 y -1 , which is equivalent to a CO 2 emission (CO 2 -e) of 500 to 800 Mt CO 2-e (IPCC, 2013). Brazil has a considerable unexplored potential for landfill biogas production (LIMA et al, 2018), which is lost due to the lack of technology in the construction of landfills (AHOUGHALANDARI; CABRAL, 2017b;BARROS et al, 2018).…”

Influence of Carbon Uniformity on Its Characteristics and Adsorption Capacities of CO2 and CH4 Gases

“…Methane (CH 4 ) and carbon dioxide (CO 2 ) gases coexist often in nature, forming gas mixtures, such as natural gas, biofuel gas, landfill gas, coal bed methane, etc. [1][2][3][4][5]. Separation of CO 2 gas from CO 2 /CH 4 mixed binary gas is a core and strategic target in enhancing the gas purity and efficiency.…”