Spatial variation in landfill gas composition under different precipitation condition and waste age in Sri Lanka

Abstract

A study was conducted to assess the effect of precipitation and age of waste on the stabilization of the dumped waste. Landfill gas samples at 1-m depth were collected from 13 waste landfill sites in Sri Lanka with different annual precipitation ranging from 1,000 to 4,000 mm and waste age ranging from 1 to 120 months. Typical landfill gases O2, N2, CH4 and CO2 were measured quantitatively by a gas chromatograph. Buried waste samples at 1-m depth were also taken from all locations to determine organic carbon contents in the residue (< 2 mm). With the age of wastes, the measured O2 and N2 concentration (ranged in 1 - 20% and 2 - 80% respectively) in collected landfill gas samples were increased and the CH4 and CO2 concentration (ranged in 0-60% and 1-68%, respectively) decreased, implying the buried wastes are getting stabilized within 120 months after dumped (typically in several decades in mid-latitude regions). However, the correlations between measured gas concentrations and the annual precipitations at the sampling site show no definite results. Organic carbon contents in the waste residues (ranged in 24-236 mg g-1) were not fully related to the waste age and the precipitation amount, while significant time-dependent decreases of the organic carbon contents can be observed in some investigated landfill sites. Further studies are needed with continuous monitoring of rainfall with gas emission.