Anthropogenic emissions of methane in the United States

Abstract

This study quantitatively estimates the spatial distribution of anthropogenic methane sources in the United States by combining comprehensive atmospheric methane observations, extensive spatial datasets, and a high-resolution atmospheric transport model. Results show that current inventories from the US Environmental Protection Agency (EPA) and the Emissions Database for Global Atmospheric Research underestimate methane emissions nationally by a factor of ∼1.5 and ∼1.7, respectively. Our study indicates that emissions due to ruminants and manure are up to twice the magnitude of existing inventories. In addition, the discrepancy in methane source estimates is particularly pronounced in the south-central United States, where we find total emissions are ∼2.7 times greater than in most inventories and account for 24 ± 3% of national emissions. The spatial patterns of our emission fluxes and observed methane-propane correlations indicate that fossil fuel extraction and refining are major contributors (45 ± 13%) in the south-central United States. This result suggests that regional methane emissions due to fossil fuel extraction and processing could be 4.9 ± 2.6 times larger than in EDGAR, the most comprehensive global methane inventory. These results cast doubt on the US EPA's recent decision to downscale its estimate of national natural gas emissions by 25-30%. Overall, we conclude that methane emissions associated with both the animal husbandry and fossil fuel industries have larger greenhouse gas impacts than indicated by existing inventories.climate change policy | geostatistical inverse modeling

Exploring the influence of ancient and historic megaherbivore extirpations on the global methane budget

“…However, the authors' computations greatly underestimated per capita enteric emissions by wild mammals (35). Moreover, recent work suggests that inventories also underestimate the contribution of domestic mammals by a factor of 1.5-1.7 (14), perhaps because of flaws in Intergovernmental Panel on Climate Change (IPCC) methodologies, which only perform well over a fairly narrow range of animal body mass (35). Our results suggest modern enteric emissions by domestic and wild mammals total ∼160 Tg CH 4 y −1 (Table 2), substantially more than the ∼90-100 Tg CH 4 y −1 currently in IPCC inventories (12).…”

“…Although a variety of natural and anthropogenic sources produce methane, for many countries, domestic mammals are the primary source (12). Although ∼200 times less abundant than carbon dioxide in the atmosphere, methane's greater efficiency in trapping radiation and reactions with other trace gases leads to a significant role in the radiative forcing of climate (12)(13)(14)(15). Moreover, CH 4 is an attractive and relatively inexpensive target for mitigation because it has a relatively short residence in the atmosphere (14).…”

“…Although ∼200 times less abundant than carbon dioxide in the atmosphere, methane's greater efficiency in trapping radiation and reactions with other trace gases leads to a significant role in the radiative forcing of climate (12)(13)(14)(15). Moreover, CH 4 is an attractive and relatively inexpensive target for mitigation because it has a relatively short residence in the atmosphere (14). Although total global emissions are constrained reasonably well (∼500-600 Tg CH 4 y −1 ), quantification by source sector has proven more difficult, with estimates varying by a factor of 2-3 (12,15).…”

Long-Path Quantum Cascade Laser–Based Sensor for Methane Measurements

“…The open-path-integrated sensing platform is especially advantageous for spatially heterogeneous and temporally variable CH 4 sources with large uncertainties, including agricultural emissions and petrochemical activities ranging from natural gas infrastructure leakage to hydraulic fracturing wells and waste facilities (Howarth et al 2011;Alvarez et al 2012;Peischl et al 2012;Péron et al 2012;Karion et al 2013;Miller et al 2013). Finally, open-path-integrated CH 4 measurements at long (kilometer) pathlengths can also be used to detect emissions for comparison with CH 4 model simulations and emission inventories on comparable spatial scales.…”

Methods of preparing internal combustion engine cylinder bore surfaces for frictional improvement

“…According to the Intergovernmental Panel On Climate Change (IPCC), 57% of the total greenhouse emissions in 2007 came from the burning of fossil fuels alone which amounts to 32 billion metric tonnes of CO2 [4]. The average CO2 levels in the atmosphere has risen from 328 ppm in 1970 to 399 ppm in 2013 [5]. As ICEs still are an integral to modern day living and its fuel source is not renewable, it is wise to invest some effort to make it cleaner and more fuel efficient to stretch oil reserve lifespans; allowing for more time for alternative renewable energy sources such as solar power to mature.…”