Landfill gas distribution at the base of passive methane oxidation biosystems: Transient state analysis of several configurations. (November 2017)

• Record Type: Journal Article
• Authors: Ahoughalandari, Bahar; Cabral, Alexandre R.
• Is Part Of: Waste management. Volume 69(2017)
• Page Start: 298
• Page End: 314
• Publication Date: 2017-11
• Subjects: Passive methane oxidation biosystems -- Numerical simulation -- Unsaturated hydraulic behavior -- Landfill final covers -- Design -- Landfill gas flow; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2017.08.027
• Languages: English
• ISSNs: 0956-053X

Abstract

Highlights: Study shows the importance of having criteria in design of passive methane oxidation biosystems. Using a design criterion, the onset of restriction in upward flow of landfill gas was predicted. Choosing the appropriate materials, a permanently unrestricted flow of landfill gas was assured. 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.