Quantifying Uncontrolled Landfill Gas Emissions from Two Florida ...

[6.5 g/s CH4 / 8800 m 2 surface area] *3600 sec/hr *24 hr/day = 64 g/day/m 2 CH4
The methane emission factor from the slopes is estimated by calculating the methane emission
factor for each of the two source slope areas contributing to the methane emissions measured
during the time of the VRPM surveys. For the control area, this is the southern and western
slopes, based on the prevailing wind direction during the time of the measurements (see Section
3.1.1). The total surface area of each slope was calculated. Because the prevailing wind
direction was not perpendicular to the configuration plane of the survey area while the
measurements were conducted, it is likely the measurements only capture a portion of the
methane emissions. So the results will be biased low.
Previous validation studies using trace gas released have been used to evaluate plume capture. If
the trace gas is released up to 100 meters upwind of the configuration for a plane length of 200
meters. This is under ideal wind conditions that are close to perpendicular to the configuration
place (U.S. EPA, 2007). In order to more accurately estimate the methane emission factors from
the slope areas, a slope area is defined as an area bounded by the distance of the VRPM
configuration and a distance one-half the distance of the VRPM configuration. In the case of the
control area, the distance of the southern VRPM configuration plane was 180 meters and the
distance of the western VRPM plane was 51 meters. The following steps detail the calculation of
the contributing emission surface areas from the southern and western slopes of the control cell:
1) 180 meters * 90 meters = 16,200 m 2 , which is the contributing emission surface area from the
southern slope of the cell
2) 51 meters * 25.5 meters = 1,300 m 2 , which is the contributing emission surface area from the
western slope
These values were input into Equation 2 with the values of the methane flux values measured
along each VRPM configuration to calculate the emission factors from the southern and western
slopes. The calculated emission factors from the southern and western slopes were 14 g/day/m 2
and 130 g/day/m 2 , respectively.
The next step is to calculate the average measured methane emission factor from the two slopes.
This was done using a weighted average calculation. According to the calculations above, the
contributing emissions surface area from the western slope is approximately 7 percent of the total
contributing emission surface area. The surface area from the southern slope is approximately
93 percent of the total contributing emission surface area. The following details the calculation
of the weighted average measured methane emission factor from the two slopes of the control
cell:
0.07 *130 g/day/m 2 methane western slope + 0.93 * 14 g/day/m 2 methane southern slope =
22 g/day/m 2 from the slopes of control cell
As mentioned previously, the total surface area of the top of the cell was 8800 m 2 . The total
surface area of the slopes of the cell was estimated by multiplying the length of the VRPM
configuration plane by 100 meters, which was the estimated distance from the top of the landfill
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