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- ItemOpen AccessDataset associated with "A cautionary report of calculating methane emissions using low-cost fence-line sensors"(Colorado State University. Libraries, 2022) Riddick, Stuart; Ancona, RileyMethane is emitted during extraction, processing, and transport processes in the natural gas industry. As a powerful greenhouse gas, methane releases are harmful to the environment. Operators aim to minimize methane loss, and continuous monitoring using low-cost fence-line sensors are now being developed to observe methane enhancements downwind of operations. However, it is not clear how useful these systems are and whether they can be used to quantify emissions or simply identify the presence of a leak. To investigate this, we deployed four calibrated low-cost sensors 30 m from emissions of known rates over a 48-hour period. The aims were to determine: 1) how much of the time a fence-line system would detect a leakage event from a single, point source of the size typically seen at oil and gas production well pads; and 2) how accurately a fence-line system can estimate emissions using a relatively simple downwind dispersion method. Our results show that during the 48-hour measurement period the sensors could detect mixing ratios greater than an enhancement threshold of 2 ppm for methane releases of 84 g h-1 40% of the time, 100% of the time for emissions of 167 g h-1 and 100% of the time downwind of the 313 g h-1. We show that emissions can be overestimated by as much as 4 x 10102 times using a simple Gaussian plume equation, which was attributed to the inability of the equation to parameterize lateral dispersion at distances less than 100 m. Using two other methods, near real-time average emissions can be calculated to be within 23% of a known emission rate of the source, however individual emissions can vary by -100% and +1,885%. This study provides evidence to support the use of low-cost sensors as autonomous fence-line monitoring systems to detect and potentially quantify emissions. If the sensors are properly calibrated and sensor deployment location is optimized for prevailing wind directions at each site, fence-line systems could be used routinely to quantify emissions from oil and gas infrastructure.
- ItemOpen AccessDataset associated with "A laboratory assessment of 120 air pollutant emissions from biomass and fossil fuel cookstoves(Colorado State University. Libraries, 2018) Bilsback, KelseyCookstoves emit many pollutants that are harmful to human health and the environment. However, most of the existing scientific literature focuses on fine particulate matter (PM2.5) and carbon monoxide (CO). We present an extensive dataset of speciated air pollution emissions from wood, charcoal, kerosene, and liquefied petroleum gas (LPG) cookstoves. One-hundred and twenty gas- and particle-phase constituents—including organic carbon, elemental carbon (EC), ultrafine particles (10-100 nm), inorganic ions, carbohydrates, and volatile/semi-volatile organic compounds (e.g., alkanes, alkenes, alkynes, aromatics, carbonyls, and polycyclic aromatic hydrocarbons [PAHs])—were measured in the exhaust from 26 stove/fuel combinations. We find that improved biomass stoves tend to reduce PM2.5 emissions, however, certain design features (e.g., insulation or a fan) tend to increase relative levels of other co-emitted pollutants (e.g., EC, ultrafine particles, formaldehyde, or PAHs depending on stove type). In contrast, the pressurized kerosene and LPG stoves reduced all pollutants relative to a traditional three-stone fire (≥93% and ≥79%, respectively). Finally, we find that PM2.5 and CO are not strong predictors of co-emitted pollutants, which is problematic because these pollutants may not be indicators of other cookstove smoke constituents (such as formaldehyde and acetaldehyde) that may be emitted at concentrations that are harmful to human health.
- ItemOpen AccessDataset associated with "Temporal variability largely explains difference in top-down and bottom-up estimates of methane emissions from a natural gas production region"(Colorado State University. Libraries, 2018) Vaughn, Timothy L.; Bell, Clay S.; Pickering, Cody, K.; Schwietzke, Stefan; Heath, Garvin, A.; Petron, Gabrielle; Zimmerle, Daniel; Schnell, Russell, C.; Nummedal, DagThis study is the first to spatially and temporally align top-down and bottom-up methane emission estimates for a natural gas production basin, using multi-scale emission measurements and detailed activity data reporting. We show that episodic venting from manual liquid unloadings, which occur at a small fraction of natural gas well pads, drives a factor-of-two temporal variation in the basin-scale emission rate of a US dry shale gas play. The mid-afternoon peak emission rate aligns with the sampling time of all regional aircraft emission studies, which target well-mixed boundary layer conditions present in the afternoon. A mechanistic understanding of emission estimates derived from various methods is critical for unbiased emission verification and effective GHG emission mitigation. Our results demonstrate that direct comparison of emission estimates from methods covering widely different time scales can be misleading.
- ItemOpen AccessData associated with the manuscript: Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas(Colorado State University. Libraries, 2017) Jathar, Shantanu H.; Heppding, Christopher; Link, Michael F.; Farmer, Delphine K.; Akherati, Ali; Kleeman, Michael J.; de Gouw, Joost A.; Veres, Patrick R.; Roberts, James M.Isocyanic acid (HNCO), an acidic gas found in tobacco smoke, urban environments and biomass burning-affected regions, has been linked to adverse health outcomes. Gasoline- and diesel-powered engines and biomass burning are known to emit HNCO and hypothesized to emit precursors such as amides that can photochemically react to produce HNCO in the atmosphere. Increasingly, diesel engines in developed countries like the United States are required to use Selective Catalytic Reduction (SCR) systems to reduce tailpipe emissions of oxides of nitrogen. SCR chemistry is known to produce HNCO as an intermediate product, and SCR systems have been implicated as an atmospheric source of HNCO. In this work, we measure HNCO emissions from an SCR system-equipped diesel engine and, in combination with earlier data, use a three-dimensional chemical transport model (CTM) to simulate the ambient concentrations and source/pathway contributions to HNCO in an urban environment. Engine tests were conducted at three different engine loads, using two different fuels and at multiple operating points. HNCO was measured using an acetate chemical ionization mass spectrometer. The diesel engine was found to emit primary HNCO (3-90 mg kg-fuel-1) but we did not find any evidence that the SCR system or other aftertreatment devices (i.e., oxidation catalyst and particle filter) produced or enhanced HNCO emissions. The CTM predictions compared well with the only available observational data sets for HNCO in urban areas but under-predicted the contribution from secondary processes. The comparison implied that diesel-powered engines were the largest source of HNCO in urban areas. The CTM also predicted that daily-averaged concentrations of HNCO reached a maximum of ~110 pptv but were an order of magnitude lower than the 1 ppbv level that could be associated with physiological effects in humans. Precursor contributions from other combustion sources (gasoline and biomass burning) and wintertime conditions could enhance HNCO concentrations but need to be explored in future work.
- ItemOpen AccessMid-continent methane emissions study(Colorado State University. Libraries, 2016) Zimmerle, Daniel; Howell, Cynthia; Nummedal, Dag; Smits, KathleenIn this first-of-its-kind Mid-Continent Methane Emissions Study, researchers from across the region, universities, government agencies, and industries joined forces determined to reconcile discrepancies between measurement methods in methane loss rates from onshore oil and gas developments in multiple basins. Seeking to bring public and private sectors better understanding of this issue, the combined resources of these groups resulted in weeks of field study and conclusive data. This team discovered that in other studies, top-down measurements reported much higher methane leak rates than bottom-up methods. Equipped with that knowledge this team used paired measurements from the same natural gas sources to determine the inconsistencies in measurement methods. The result of a field campaign, which happened over a five week period from late September to early October, 2015 is described in the study overview.