Estimation of CH₄oxidation efficiency in an interim landfill cover soil using CO₂/CH₄ratios

Abstract

The first objective of this study was to discuss the applicability of the CO2/CH4 ratio method in order to assess CH4 oxidation efficiency. To achieve this objective, a comparison between CO2/CH4 ratios and the mass balance method was conducted. The second objective of this study was to estimate the CH4 oxidation efficiency in an interim landfill soil cover and assess how a CH4 influx influences the CH4 oxidation efficiency. The results showed that despite the CO2 problems brought by respiration, the CH4 oxidation efficiencies obtained by the CO2/CH4 ratio method led to similar results compared to the mass balance method. In this respect, the CO2/CH4 ratio method can be an indicator of the CH4 oxidation efficiencies for landfill cover soils. The CH4 oxidation efficiencies derived in this study through the CO2/CH4 ratio method ranged between 46% and 64%, and between 41% and 62% through the mass balance method. The results imply that the Intergovernmental Panel on Climate Change's (IPCC) default value of 10% for the CH4 oxidation efficiency is an underestimation for landfill cover soils. CH4 oxidation efficiency tends to be negatively correlated with CH4 influx. Therefore, CH4 influx reaching a landfill cover should be limited in order to increase the CH4 oxidation efficiency.

Applying methane and carbon flow balances for determination of first-order landfill gas model parameters

“…According to Amini et al [7], assuming that the OX ranges from 5 to 20%, uncertainty is insignificant when estimating CH 4 emissions using the FOD model. However, the OX values obtained from this study and previous literature [18] in Korean landfills were higher than those of the criteria prescribed by Amini et al [7]. Thus, in order to reduce the uncertainty of the CH 4 emission estimation when FOD models are applied to Korean landfills, site-specific OX values need to be estimated.…”

“…CH 4 oxidation in landfill cover soils can range from negligible to 100% in field settings. According to Park et al [18], OX values in a landfill range from 46 to 64%. Börjesson et al [19] showed that OX values for closed landfill sites range from 30.8 to 46.9%.…”