Quantifying the loss of processed natural gas within California's South Coast Air Basin using long-term measurements of ethane and methane

Abstract. Methane emissions inventories for Southern California's South Coast Air Basin (SoCAB) have underestimated emissions from atmospheric measurements. To provide insight into the sources of the discrepancy, we analyze records of atmospheric trace gas total column abundances in the SoCAB starting in the late 1980s to produce annual estimates of the ethane emissions from 1989 to 2015 and methane emissions from 2007 to 2015. The first decade of measurements shows a rapid decline in ethane emissions coincident with decreasing natural gas and crude oil production in the basin. Between 2010 and 2015, however, ethane emissions have grown gradually from about 13 ± 5 to about 23 ± 3 Gg yr−1, despite the steady production of natural gas and oil over that time period. The methane emissions record begins with 1 year of measurements in 2007 and continuous measurements from 2011 to 2016 and shows little trend over time, with an average emission rate of 413 ± 86 Gg yr−1. Since 2012, ethane to methane ratios in the natural gas withdrawn from a storage facility within the SoCAB have been increasing by 0.62 ± 0.05 % yr−1, consistent with the ratios measured in the delivered gas. Our atmospheric measurements also show an increase in these ratios but with a slope of 0.36 ± 0.08 % yr−1, or 58 ± 13 % of the slope calculated from the withdrawn gas. From this, we infer that more than half of the excess methane in the SoCAB between 2012 and 2015 is attributable to losses from the natural gas infrastructure

Quantifying the loss of processed natural gas within California's South Coast Air Basin using long-term measurements of ethane and methane

Methane emissions inventories for Southern California's South Coast Air Basin (SoCAB) have underestimated emissions from atmospheric measurements. To provide insight into the sources of the discrepancy, we analyze records of atmospheric trace gas total column abundances in the SoCAB starting in the late 1980s to produce annual estimates of the ethane emissions from 1989 to 2015 and methane emissions from 2007 to 2015. The first decade of measurements shows a rapid decline in ethane emissions coincident with decreasing natural gas and crude oil production in the basin. Between 2010 and 2015, however, ethane emissions have grown gradually from about 13 ± 5 to about 23 ± 3 Gg yr⁻¹, despite the steady production of natural gas and oil over that time period. The methane emissions record begins with 1 year of measurements in 2007 and continuous measurements from 2011 to 2016 and shows little trend over time, with an average emission rate of 413 ± 86 Gg yr⁻¹. Since 2012, ethane to methane ratios in the natural gas withdrawn from a storage facility within the SoCAB have been increasing by 0.62 ± 0.05 % yr⁻¹, consistent with the ratios measured in the delivered gas. Our atmospheric measurements also show an increase in these ratios but with a slope of 0.36 ± 0.08 % yr⁻¹, or 58 ± 13 % of the slope calculated from the withdrawn gas. From this, we infer that more than half of the excess methane in the SoCAB between 2012 and 2015 is attributable to losses from the natural gas infrastructure

Methane Mitigation:Methods to Reduce Emissions, on the Path to the Paris Agreement

The atmospheric methane burden is increasing rapidly, contrary to pathways compatible with the goals of the 2015 United Nations Framework Convention on Climate Change Paris Agreement. Urgent action is required to bring methane back to a pathway more in line with the Paris goals. Emission reduction from “tractable” (easier to mitigate) anthropogenic sources such as the fossil fuel industries and landfills is being much facilitated by technical advances in the past decade, which have radically improved our ability to locate, identify, quantify, and reduce emissions. Measures to reduce emissions from “intractable” (harder to mitigate) anthropogenic sources such as agriculture and biomass burning have received less attention and are also becoming more feasible, including removal from elevated-methane ambient air near to sources. The wider effort to use microbiological and dietary intervention to reduce emissions from cattle (and humans) is not addressed in detail in this essentially geophysical review. Though they cannot replace the need to reach “net-zero” emissions of CO2, significant reductions in the methane burden will ease the timescales needed to reach required CO2 reduction targets for any particular future temperature limit. There is no single magic bullet, but implementation of a wide array of mitigation and emission reduction strategies could substantially cut the global methane burden, at a cost that is relatively low compared to the parallel and necessary measures to reduce CO2, and thereby reduce the atmospheric methane burden back toward pathways consistent with the goals of the Paris Agreement

Factors Impacting Observation-Based Estimates of Urban Greenhouse Gas Emissions

Urban areas are responsible for a large and increasing fraction of anthropogenic greenhouse gas emissions. Accurate methods for quantifying and monitoring those emissions are needed to suggest and evaluate mitigation policies, as well as for fundamental carbon cycle science as anthropogenic carbon dioxide emissions become a dominant source of uncertainty in closing the global carbon budget. I present investigations into several factors that can impact our ability to characterize urban greenhouse gas emissions using observations in the atmosphere. An automated method is developed for estimating the mixing depth, a key meteorological variable affecting the sensitivity of mole fraction observations to emissions fluxes, using optical remote sensing instruments. In a long time series of mixing depth estimates in Pasadena, California, day-to-day variability is shown to be large in comparison to seasonal trends. Significant mixing depth biases are demonstrated in meteorological models, and the likely impacts on emissions estimation are discussed. Optimized estimates of methane emissions in the South Coast Air Basin, California, are made using several flux inversion or regularization methods, with four sources of meteorological information, and with all or some of the mole fraction observations taken at nine within-basin observing sites associated with the LA Megacities Carbon Project. Using the full observational dataset in a geostatistical inversion, the capability to detect seasonal and event-driven emissions changes is demonstrated with generic meteorology, opening the door to near-real-time monitoring. Differences in absolute methane emissions flux magnitude according to the source of driving meteorological information are shown to be largely removable by calibration to a trusted model. The choice of inversion or regularization method is shown to have substantial impacts both on the estimated emissions time series and on the capacity to detect emissions changes, especially when the observational constraint is reduced.PHDPhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/145986/1/johnware_1.pd

Focusing Events in Environmental Policy: Exide Technologies, Aliso Canyon, and Industrial Health Crises in Southern California

Focusing events are sudden, rare events that become known to policymakers and the public simultaneously, highlighting issues with existing public policy. Two case studies, the gas leak from the Aliso Canyon natural gas storage facility near Porter Ranch, and the publication of the Health Risk Assessment and discovery of lead contamination from Exide Technologies’ battery recycling facility in Vernon, are used to deepen theoretical insights into the development and functionality of industrial health crises as focusing events. The case studies suggest four key areas relevant to understanding focusing events. The first is the unique characteristics of industrial health crises, which often involve anthropogenic risks and a degree of contestation unusual in other focusing event literature. The second is the scale of analysis, balancing geospatial realities with local histories, broad social dynamics and power structures, and the multiscalar nature of policy change. Third, community activism plays multiple vital roles in pushing a potential focusing event towards lasting policy change. Finally, the incorporation of ideas from environmental justice into the focusing event framework results in a better understanding of power and privilege in the creation of, and response to, industrial health crises. All four aspects have been written about in other bodies of literature, but have not yet been brought to bear on the concept of focusing events. These four domains thus add nuance to the scholarly understanding of one aspect of the policy change process, and provide a starting point for further research into the processes governing our public policy systems

Cavity Ring-Down and Multi-Pass Spectroscopies for Methane Source Attribution and Chemical Kinetics Studies

Methane is the most abundant hydrocarbon in the Earth atmosphere, is also an important greenhouse gas, energy source, and microbial metabolic energy source and product. With the rapid increase of atmospheric methane concentration, it has become very important to quantify methane emissions from different sources. This thesis describes the applications of cavity ring-down applications on atmospheric ethane measurements and measurements of doubly substituted methane for methane source attributions. We also present our work on chemical kinetics studies of an alkene ozonolysis intermediate, Criegee intermediate, using a multi-pass absorption technique. In Chapter 2, we demonstrated the performance of a continuous-wave (cw) interband cascade laser (ICL) based mid-infrared cavity ring-down spectroscopy (CRDS) sensor for atmospheric ethane (C2H6) detection. A 3.36 µm cw ICL with an was used to target two ethane absorption bands at 2976.788 cm-1 and 2983.383 cm-1. This technique utilizes the long effective pathlength (~ 4.5 km) of CRDS to increase sensitivity of atmospheric ethane detection. Our spectrometer can measure atmospheric ethane concentration as low as 200 pptv at standard temperature and pressure. We have used this instrument to measure the atmospheric ethane composition in ambient air collected in Pasadena, California. We have utilized this instrument to aid in the study of soil microbial response post the Porter Ranch gas leak. Results were shown in Chapter 3. In Chapter 4, we demonstrate high sensitivity measurements of both 13CH3D and 12CH2D2 isotopologues using a high precision and high resolution spectroscopy technique, frequency stabilized cavity ring-down spectroscopy (FS-CRDS). Measurements of the abundances of doubly-substituted methane isotopologues (13CH3D and 12CH2D2) are important in methane source attributions. Currently, methods developed for 13CH3D and 12CH2D2 measurements have been mostly focused on the use of isotope ratio mass spectrometry (IRMS), which faces the challenges of mass resolutions. In this work, we focus on measuring these low abundant methane isotopologues optically, taking advantage of the distinct absorption features of them. This technique can be used as a potential complement to IRMS measurements for its ability to measure abundances of rare methane isotopologues with a short time average (~1 hour average per isotope ratio measurement). In Chapter 5, we utilized our IR kinetic spectroscopy (IRKS) apparatus to study the formation of HCO radicals from the smallest Criegee Intermediate (CH2OO), which is an important intermediate from oznolysis of the smallest alkene.</p

Unconventional Oil and Gas Development: Evaluation of selected hydrocarbons in the ambient air of three basins in the United States by means of diffusive sampling measurements

The impact of emissions associated with the extraction of crude oil and natural gas upon air quality in the United States (US) is widely recognised to have an impact on climate change, human health and ground-level ozone formation. A number of measurement approaches are being applied to evaluate the environmental impact of the oil and gas (O&G) sector, including satellite, airborne and ground-based platforms. Measurement based studies, in particular those that estimate flux rates, are critical for the validation of emission inventories that often under-report actual emissions of methane and volatile organic compounds (VOC) from the O&G sector. On-going research projects in the US are investigating the consistency of emission rates from O&G emission sources associated with extraction, transmission and distribution activities. The leakage rates of methane, as related to production levels, in the US for O&G developments varies from less than 1% (e.g. Upper Green River Basin, Wyoming) to over 6% (Uintah Basin, Utah). European research and policy approaches can learn from efforts in the US that are improving the accuracy of reporting emissions from O&G sources, enhancing our understanding of air quality impacts, and reducing emissions through regulatory controls. The Joint Research Centre (JRC) of the European Commission performed a diffusive sampling project, with the collaboration of the University of Wyoming, in conjunction with the SONGNEX (Studying the Atmospheric Effects of Changing Energy Use in the US at the Nexus of Air Quality and Climate Change) project led by the US National Oceanic and Atmospheric Administration. The SONGNEX project is an airborne measurement campaign supported by a number of associated ground based studies. The applicability of the Pocket Diffusive (PoD) sampler, for measurement of VOC (C4-C10), heavy hydrocarbons and volatile polycyclic aromatic hydrocarbons (PAHs) in areas heavily influenced by O&G development, is evaluated. Three sampling surveys were performed to assess three basins (Upper Green River, Uintah and North Platte) characterised by different management regimes, meteorology and hydrocarbon products. This first extensive field deployment of the PoD sampler demonstrates the effectiveness of the sampler for time-integrated measurements of targeted pollutants over wide spatial areas. The ambient air at these basins reveal different compositional profiles of hydrocarbons (C4-C10). Analysis of aromatics supports a finding of relatively elevated levels in the Pinedale Anticline (Upper Green River). From an evaluation of the behaviour of alkanes, it is evident that there is a relatively high leakage rate in the Uintah Basin. Heavy hydrocarbons (C11-C22) and PAHs are measured at relatively low levels. Despite low concentrations, analysis of these compounds improves the accuracy of source identification. A comparison of ground based PoD data and airborne SONGNEX data showed good agreement for commonly reported VOCs. The utility of the PoD sampler for analysis of emission sources was enhanced with reporting of a wide range of compounds. Spatial Positive Matrix Factorization analysis showed the possibility of using PoD samplers for differentiating emission sources, characterizing different areas and estimating the relative contribution of different emission sources.JRC.C.5-Air and Climat

Experimental investigation of elastomer performance for underground hydrogen storage wells

The "Power-to-Gas" concept is vital in the envisaged Hydrogen Economy as it ensures sustainability and energy security. The process involves converting surplus energy from various sources like conventional fossils, wind and solar into hydrogen for storage in underground structures and reproducing them during periods of high energy demand. Depleted hydrocarbon reservoirs are the most common underground structures for hydrogen storage. Being a relatively new concept, Underground Hydrogen Storage (UHS) in depleted hydrocarbon reservoirs is associated with challenges related to several aspects of well integrity, including elastomers as seen in well bore seal assemblies. This study investigates the behavior of general-purpose oil and gas industry elastomers in UHS environments. Three general-purpose elastomers, Ethylene Propylene Diene Monomer (EPDM), Flouroelastomers (FKM), and Nitrile Butadiene Rubber (NBR), are exposed to varied gas mixtures at different aging conditions via autoclave aging experiments and their physio-mechanical properties examined. In addition, observed cavities on the elastomers are statistically analyzed to ascertain the onset of elastomer failure due to cavity formation. Furthermore, changes in the surface morphology of elastomers due to aging were also investigated via Scanning Electron Microscopy (SEM). The result showed that exposure of elastomers to gaseous hydrogen environments at the specified environmental conditions causes changes in their physio-mechanical properties which may subsequently result in material failure. Furthermore, two main phenomena were identified to be the primary cause the changes in the mechanical properties of elastomers samples for the given test conditions: Plasticization effect by gases and elastomer chain rupture or cross-linkage formations due to chemical ageing. Carbon dioxide was identified to have the most deteriorative effect on the mechanical properties of elastomers due to its low diffusivity coefficient and high plasticization effect on polymer chains. The effects of pure hydrogen and hydrogen-methane mixtures on the mechanical properties of elastomers were identified to be similar. EPDM showed increased hardness and compressional resistance when aged in 100% hydrogen and hydrogen-methane mix environments at high temperatures and poor compressional resistance at low temperatures. EPDM also maintained its thermal resistance properties in gaseous hydrogen environments. The most significant elastomer degradation in gaseous hydrogen environments was seen in NBR. FKM remained thermally stable in gaseous hydrogen environments, although its compressional resistance reduced at elevated temperatures. Furthermore, SEM showed rougher surfaces of EPDM and NBR elastomers after aging in a pure hydrogen environment at 70oC for 7 days, which was proposed to be due to the formation of cross-links. Also identified on the surface of these elastomers after aging are haphazardly distributed micro-cavities and precipitates proposed to be additives used in material production. Finally, statistical analysis indicated that for all samples aged in 100% H2 and (50% H2 + 50% CH4) for 3 days at 70oC, there is statistical evidence of cavity formation due to aging except for NBR samples aged in 100% H2 at 70oC for 3 days.This thesis has been revised, with changes approved by the Graduate College on June 24, 2023. The original version is available at: https://shareok.org/handle/11244/33756