California's methane super-emitters Duren, Riley M; Thorpe, Andrew K; Foster, Kelsey T ...
Nature,
11/2019, Letnik:
575, Številka:
7781
Journal Article
Recenzirano
Odprti dostop
Methane is a powerful greenhouse gas and is targeted for emissions mitigation by the US state of California and other jurisdictions worldwide
. Unique opportunities for mitigation are presented by ...point-source emitters-surface features or infrastructure components that are typically less than 10 metres in diameter and emit plumes of highly concentrated methane
. However, data on point-source emissions are sparse and typically lack sufficient spatial and temporal resolution to guide their mitigation and to accurately assess their magnitude
. Here we survey more than 272,000 infrastructure elements in California using an airborne imaging spectrometer that can rapidly map methane plumes
. We conduct five campaigns over several months from 2016 to 2018, spanning the oil and gas, manure-management and waste-management sectors, resulting in the detection, geolocation and quantification of emissions from 564 strong methane point sources. Our remote sensing approach enables the rapid and repeated assessment of large areas at high spatial resolution for a poorly characterized population of methane emitters that often appear intermittently and stochastically. We estimate net methane point-source emissions in California to be 0.618 teragrams per year (95 per cent confidence interval 0.523-0.725), equivalent to 34-46 per cent of the state's methane inventory
for 2016. Methane 'super-emitter' activity occurs in every sector surveyed, with 10 per cent of point sources contributing roughly 60 per cent of point-source emissions-consistent with a study of the US Four Corners region that had a different sectoral mix
. The largest methane emitters in California are a subset of landfills, which exhibit persistent anomalous activity. Methane point-source emissions in California are dominated by landfills (41 per cent), followed by dairies (26 per cent) and the oil and gas sector (26 per cent). Our data have enabled the identification of the 0.2 per cent of California's infrastructure that is responsible for these emissions. Sharing these data with collaborating infrastructure operators has led to the mitigation of anomalous methane-emission activity
.
Solid waste management represents one of the largest anthropogenic methane emission sources. However, precise quantification of landfill and composting emissions remains difficult due to variety of ...site-specific factors that contribute to landfill gas generation and effective capture. Remote sensing is an avenue to quantify process-level emissions from waste management facilities. The California Methane Survey flew the Next Generation Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-NG) over 270 landfills and 166 organic waste facilities repeatedly during 2016-2018 to quantify their contribution to the statewide methane budget. We use representative methane retrievals from this campaign to present three specific findings where remote sensing enabled better landfill and composting methane monitoring: (1) Quantification of strong point source emissions from the active face landfills that are difficult to capture by in situ monitoring or landfill models, (2) emissions that result from changes in landfill infrastructure (design, construction, and operations), and (3) unexpected large emissions from two organic waste management methods (composting and digesting) that were originally intended to help mitigate solid waste emissions. Our results show that remotely-sensed emission estimates reveal processes that are difficult to capture in biogas generation models. Furthermore, we find that airborne remote sensing provides an effective avenue to study the temporally changing dynamics of landfills. This capability will be further improved with future spaceborne imaging spectrometers set to launch in the 2020s.
Comparisons of carbon uptake estimates from bottom-up terrestrial biosphere models (TBMs) to top-down atmospheric inversions help assess how well we understand carbon dioxide (CO2) exchange between ...the atmosphere and terrestrial biosphere. Previous comparisons have shown varying levels of agreement between bottom-up and top-down approaches, but they have almost exclusively focused on large, aggregated scales (e.g., global or continental), providing limited insights into reasons for the mismatches. Here we explore how consistency, defined as the spread in net ecosystem exchange (NEE) estimates within an ensemble of TBMs or inversions, varies with at finer spatial scales ranging from 1∘×1∘ to the continent of North America. We also evaluate how well consistency informs accuracy in overall NEE estimates by filtering models based on their agreement with the variability, magnitude, and seasonality in observed atmospheric CO2 drawdowns or enhancements. We find that TBMs produce more consistent estimates of NEE for most regions and at most scales relative to inversions. Filtering models using atmospheric CO2 metrics causes ensemble spread to decrease substantially for TBMs, but not for inversions. This suggests that ensemble spread is likely not a reliable measure of the uncertainty associated with the North American carbon balance at any spatial scale. Promisingly, applying atmospheric CO2 metrics leads to a set of models with converging flux estimates across TBMs and inversions. Overall, we show that multiscale assessment of the agreement between bottom-up and top-down NEE estimates, aided by regional-scale observational constraints is a promising path towards identifying fine-scale sources of uncertainty and improving both ensemble consistency and accuracy. These findings help refine our understanding of biospheric carbon balance, particularly at scales relevant for informing regional carbon-climate feedbacks.
Accurate and timely detection, quantification, and attribution of methane emissions from Underground Gas Storage (UGS) facilities is essential for improving confidence in greenhouse gas inventories, ...enabling emission mitigation by facility operators, and supporting efforts to assess facility integrity and safety. We conducted multiple airborne surveys of the 12 active UGS facilities in California between January 2016 and November 2017 using advanced remote sensing and in situ observations of near-surface atmospheric methane (CH4). These measurements where combined with wind data to derive spatially and temporally resolved methane emission estimates for California UGS facilities and key components with spatial resolutions as small as 1-3 m and revisit intervals ranging from minutes to months. The study spanned normal operations, malfunctions, and maintenance activity from multiple facilities including the active phase of the Aliso Canyon blowout incident in 2016 and subsequent return to injection operations in summer 2017. We estimate that the net annual methane emissions from the UGS sector in California averaged between 11.0 3.8 GgCH4 yr−1 (remote sensing) and 12.3 3.8 GgCH4 yr−1 (in situ). Net annual methane emissions for the 7 facilities that reported emissions in 2016 were estimated between 9.0 3.2 GgCH4 yr−1 (remote sensing) and 9.5 3.2 GgCH4 yr−1 (in situ), in both cases around 5 times higher than reported. The majority of methane emissions from UGS facilities in this study are likely dominated by anomalous activity: higher than expected compressor loss and leaking bypass isolation valves. Significant variability was observed at different time-scales: daily compressor duty-cycles and infrequent but large emissions from compressor station blow-downs. This observed variability made comparison of remote sensing and in situ observations challenging given measurements were derived largely at different times, however, improved agreement occurred when comparing simultaneous measurements. Temporal variability in emissions remains one of the most challenging aspects of UGS emissions quantification, underscoring the need for more systematic and persistent methane monitoring.
This study derives methane emission rates from 92 airborne observations collected over 23 facilities including 5 refineries, 10 landfills, 4 wastewater treatment plants (POTWs), 2 composting ...operations, and 2 dairies in the San Francisco Bay Area. Emission rates are measured using an airborne mass-balance technique from a low-flying aircraft. Annual measurement-based sectorwide methane emissions are 19,000 ± 2300 Mg for refineries, 136,700 ± 25,900 Mg for landfills, 11,900 ± 1,500 Mg for POTWs, and 11,100 ± 3,400 Mg for composting. The average of measured emissions for each refinery ranges from 4 to 23 times larger than the corresponding emissions reported to regulatory agencies, while measurement-derived landfill and POTW estimates are approximately twice the current inventory estimates. Significant methane emissions at composting facilities indicate that a California mandate to divert organics from landfills to composting may not be an effective measure for mitigating methane emissions unless best management practices are instituted at composting facilities. Complementary evidence from airborne remote sensing imagery indicates atmospheric venting from refinery hydrogen plants, landfill working surfaces, composting stockpiles, etc., to be among the specific source types responsible for the observed discrepancies. This work highlights the value of multiple measurement approaches to accurately estimate facility-scale methane emissions and perform source attribution at subfacility scales to guide and verify effective mitigation policy and action.
Methane (CH4), an important greenhouse gas and pollutant, has been targeted for mitigation. Our recent California airborne survey identified >500 CH4 point source super-emitters, which accounted for ...34%-46% of the statewide CH4 emissions inventory for 2016 (Duren et al 2019 Nature 575 180-184). Individual plumes were observed in close proximity to expected methane emitting infrastructure, including gas storage facilities, hydrocarbon storage tanks, landfills, dairy lagoons, and pipeline leaks. In order to systematically attribute these plumes to their sources, we developed Vista-CA a geospatial database, that contains more than 900 000 validated CH4 infrastructure elements in the state of California. In parallel, we developed a complimentary algorithm that attributes any individual CH4 plume observation to the most likely Vista-CA source with 99% accuracy. The present study illustrates the capabilities of the Vista-CA CH4 database along with the Airborne Visible/Infrared Imaging Spectrometer-Next Generation airborne CH4 retrievals to locate and attribute CH4 point sources to specific economic sectors to improve the state CH4 budget and identify mitigation targets.
During the U.S.-Mexican War (1846-48) the U.S. army invaded Mexico from several fronts. The Mexican Army was unable to prevent U.S. troops marching into and occupying Mexico City, resulting in the ...transfer of a vast swath of territory from Mexico to the United States. Historians offer several explanations for Mexico's inability to repel this invasion, and one of them is the disunity of the Mexican nation. Evidence of this disunity can be seen in the response of some local leaders when they were confronted with the invading army: instead of fighting, they elected to surrender, allowing U.S. troops to occupy their town. This decision was viewed as treasonous by many Mexicans. However, local leaders were not motivated by any desire to overthrow their country; rather, their choices were prompted by localism: the prioritization of local community affairs over national affairs. By examining the war experience of two particular towns, La Paz, Baja California, and Santa Fe, Nuevo-Mexico, it becomes clear that localism was a significant factor during the U.S.-Mexican War. Furthermore, it becomes clear that an analysis of the relationship between the local community and the nation is crucial to fully understand not only historical facts, but human behaviors and identities.
As climate change and greenhouse gas emissions become an increasing concern, there is a push for phasing out traditional combustion engine vehicles and replacing them with electric vehicles. The ...University of Washington has ambitious carbon emissions reduction plans including electrification of the UW Transportation vehicle fleet of over 500 vehicles. To successfully accommodate an electrified fleet with minimal cost implications and infrastructure upgrades, UW Transportation must deploy charge management and charge scheduling techniques to minimize energy, power, and charger requirements for the fleet. This thesis analyzes several strategies for when and where to charge electric vehicles in the UW Transportation fleet. As a result, charging every fleet vehicle every weekday and splitting charging between weekdays and weekends are the best options. The approach used in this analysis can be expanded to apply to other fleets using the UW Transportation fleet as a case study.
There is a lack of understanding of the impact of generalized joint mobility, joint hypermobility, and resting scapular position on neurodynamic testing of the median nerve. The objectives of the ...study were to determine: 1) the reliability of the Beighton score (BS) with and without the cutoff score for general joint hypermobility (GJH); 2) if there are differences in the Median Neurodynamic Test 1 (MNT 1) based on the Beighton cutoff score for GJH; 3) if there are differences in the MNT 1 based on an assessment of resting scapular position; 4) if there are relationships between the BS with and without the cutoff score for GJH, resting scapular position, and MNT 1.
Testing was performed by two testers at two-time intervals at least 1 week apart. The population of interest was healthy asymptomatic adults. The outcome measures included the BS, resting scapular position, and MNT 1.
Intraclass correlation coefficients (ICC2,1) were 0.52 for intertester reliability at visit 1 and 0.86 at visit 2, with intratester reliability of 0.88 for Tester 1 and 0.71 for Tester 2 for the BS. Intertester prevalence-adjusted bias-adjusted kappa (PABAK) values for the Beighton GJH cutoff scores were 0.80–0.84 and 0.80 to 0.92 for intratester reliability. There were no statistically significant differences or relationships for any of the other variables of interest.
Joint mobility and resting scapular position are not confounding variables when performing MNT 1 in an asymptomatic population.
Fens, marshy wetlands with an accumulation of partially decomposed organic matter known as peat, are estimated to store up to a third of the Earth’s soil organic carbon. The Chattanooga Fen, located ...in the San Juan National Forest in southwestern Colorado, is anthropogenically and endogenously impacted by elevated concentrations of toxic metals. The anthropogenic source of metals to the Fen is Acid Mine Drainage (AMD), acidic metal-rich effluent formed by oxidized metals from the nearby Gold Finch Mine. The endogenous metal impact on the Fen is a result of subsurface acid rock drainage (ARD) formed from the natural oxidation of sulfur-bearing minerals. While the entirety of the Fen is naturally impacted by ARD-associated metals, the geographical terrain bisects the Fen into AMD-affected and AMD-unaffected portions. The chemical profiles of ARD and AMD are distinctly different from each other in terms of dissolved metal concentrations, pH, and anions. This study aimed to elucidate the impact of AMD in shaping the taxonomic diversity and carbon usage of the microbial communities within this rare, uncharacterized Fen. Sediment cores and water samples were collected in July and September 2016 at the outflow of the Gold Finch mine, along an AMD-gradient, and from naturally metal-impacted sediments unimpacted by AMD. Illumina high-throughput sequencing of extracted 16S rDNA from sediments provided the taxonomic structure of the bacterial communities within the different areas of the Fen. Carbon source usage was evaluated via BIOLOG EcoPlates and qPCR of three glycoside hydrolase (GH) genes. Data suggests that differences in both taxonomic structure and carbon source utilization can be explained by the presence of AMD. Sediments unaffected by AMD had a higher relative abundance of Acidobacteria, while Deltaproteobacteria was dominant in AMD-affected sediments. The communities within the AMD-affected sediments also utilized a higher proportion of carboxylic acids on the culture-based EcoPlates, while the unaffected samples displayed a greater usage of carbohydrates in terms of resulting optical density values. However, there were two commonalities between AMD-affected and unaffected sediments which was the use of xylose and cellobiose. The average number of carbon sources utilized by unaffected samples was 35.5% greater than affected; the lowest number of substrates being used was observed with the direct acid mine effluent samples. The abundance of all three GH genes was also greater in all AMD-unaffected samples compared to AMD-affected samples. The understanding of how metal source impacts the diversity and functional potential of microorganisms within the Chattanooga Fen, and other similar fen systems, will be essential in influencing future management decisions.
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