An Investigation on Methane Flux in Landfills and Correlation with Surface Methane Concentration
Date
2020-04-29
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Abstract
With growing concerns over greenhouse gas emissions increase on one hand, and methane’s high global warming potential on the other, direct methane emission measurement techniques from area sources such as landfills are receiving increased scrutiny. The static enclosure chamber method is the only technique that allows direct measurement of landfill gas fluxes. However, due to the large footprint of landfills, as well as the temporal and spatial variability of landfill methane emissions, the static enclosure method may not be the best option under some situations because it is time-consuming and labor-intensive. Collecting surface methane concentration (SMC) data through the instantaneous emission measurement (IEM) technique is relatively easy and inexpensive, however it is merely a qualitative means of evaluating surface methane emissions. This study investigated the development of a relationship between SMCs and methane flux across the soil-atmosphere boundary in a small-scale test cell under a partially controlled environment, in an attempt to translate SMC data into quantitative estimates. In addition, the study investigated the effect of wind speed on surface and flux measurements and the correlation between the two. The results demonstrated a significant positive correlation between SMCs and surface flux measurements. However, a better correlation was achieved when the analysis was performed under calm wind conditions and mild-to-moderate wind conditions separately. Under calm wind conditions, a linear correlation was found between SMCs and flux measurements with a resulting R2 of 0.94 and 0.90 for regression through origin and regression with intercept, respectively. These findings were in agreement with those of various researchers who have suggested surface flux has a positive and, in some cases, strong relationship with methane concentrations. The results also suggested that the presence of wind caused a decrease in average measured flux for the majority of inlet flowrates. It also significantly decreased concentrations measured in the test cell, while shifting the gas to defuse from areas that are further away from the wind source. Under windy conditions, the results of statistical analysis showed that SMCs have a linear correlation with flux divided by wind speed with a resulting R2 of 0.88, and other independent variables were found to be statistically insignificant. This finding was in agreement with the findings of researchers who observed an inverse relationship between SMCs and wind speeds. It is also in line with the Gaussian steady-state dispersion model which shows a direct relationship between SMC and emission rate divided by wind velocity.
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Keywords
landfill gas, methane, flux, surface concentration
Citation
Irandoost, E. (2020). An Investigation on Methane Flux in Landfills and Correlation with Surface Methane Concentration (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.