Impact of changes in barometric pressure on landfill methane emission

Abstract

Landfill methane emissions were measured continuously using the eddy covariance method from June to December 2010. The study site was located at the Bluff Road Landfill in Lincoln, Nebraska, USA. Our results show that landfill methane emissions strongly depended on changes in barometric pressure; rising barometric pressure suppressed the emission, while falling barometric pressure enhanced the emission, a phenomenon called barometric pumping. There was up to a 35-fold variation in day-to-day methane emissions due to changes in barometric pressure. Wavelet coherence analysis revealed a strong spectral coherency between variations of barometric pressure and methane emission at periodicities ranging from 1 day to 8 days. Power spectrum and ogive analysis showed that at least 10 days of continuous measurements was needed in order to capture 90% of the total variance in the methane emission time series at our landfill site. From our results, it is clear that point-in-time measurements taken at monthly or longer time intervals using techniques such as the trace plume method, the mass balance method, or the closed-chamber method will be subject to large variations in measured emission rates because of the barometric pumping phenomenon. Estimates of long-term integrated methane emissions from landfills based on such measurements could yield uncertainties, ranging from 28.8% underestimation to 32.3% overestimation. Our results demonstrate a need for continuous measurements to quantify annual total landfill emissions. This conclusion may apply to the study of methane emissions from wetlands, peatlands, lakes, and other environmental contexts where emissions are from porous media or ebullition. Other implications from the present study for hazard gas monitoring programs are also discussed.

Reconciling divergent estimates of oil and gas methane emissions

“…1, left column). We hypothesize that some of the residual daily variation in total CH 4 emissions was caused by biogenic sources (33)(34)(35). The agreement also suggests well-designed TD or BU surveys can characterize emissions with sufficient accuracy to verify overall regional effectiveness of any future regulation of CH 4 emissions.…”

Assessing the optimized precision of the aircraft mass balance method for measurement of urban greenhouse gas emission rates through averaging

“…If we assume that the CH 4 average we obtained (67 mol/s) for the city-wide total is representative, the Lamb et al (2016) value for the SSLF represents 46% of the city-wide total. Variability of CH 4 emissions from landfills is partially dependent on the local climate, which can influence the seasonal oxidation of landfill covers (Xu et al, 2014;Spokas et al, 2015). To better understand the variability of the SSLF emissions, we considered several factors known to influence landfill emissions, such as change in barometric pressure over time, air temperature and precipitation (Xu et al, 2014;Spokas et al, 2015).…”

“…Variability of CH 4 emissions from landfills is partially dependent on the local climate, which can influence the seasonal oxidation of landfill covers (Xu et al, 2014;Spokas et al, 2015). To better understand the variability of the SSLF emissions, we considered several factors known to influence landfill emissions, such as change in barometric pressure over time, air temperature and precipitation (Xu et al, 2014;Spokas et al, 2015). However, no particular correlations were found between aircraft-determined CH 4 emission rates (the part attributed to the landfill) and average atmospheric temperature recorded at Indianapolis International airport during the experiments (data downloaded from http://www.ncdc.noaa.gov/qclcd/QCLCD, accessed on 10/05/2015), as well as with relative humidity and barometric pressure.…”

Methane emissions as energy reservoir: Context, scope, causes and mitigation strategies

“…Site precipitation, preferential flow paths within the waste mass, the distribution of methanotropes in cover soils, and underlying waste quality and history all affect measurements at a particular place at a landfill. Barometric pressure has also been identified as a key environmental control on measurements of release rates [139]. Although approaches to integrate areal site releases are available (see Section 4.4), the most common means to estimate a site's gas emissions is through a model [125].…”

“…The methane integrals are usually measured by either Fourier transform infra-red (FTIR) spectroscopy [179] or tunable diode laser adsorption spectroscopy [177]. These create one-time estimates of CH4 emissions, and are difficult to replicate because of high labor requirements and changes in particular measurement topographies because different wind conditions require changes in the locations of the transects [139]. The modeling approach was developed to measure gas releases over flat ground, and so has been modified to work on landfill settings that often have steep slopes; often these adjusted modeling results did not meet QA/QC expectations [177].…”