Measurements Of Methane Emissions Research Articles

Using open-path dual-comb spectroscopy to monitor methane emissions from simulated grazing cattle

Abstract. Accurate whole-farm or herd-level measurements of livestock methane emissions are necessary for anthropogenic greenhouse gas inventories and to evaluate mitigation strategies. A controlled methane (CH4) release experiment was performed to determine if dual-comb spectroscopy (DCS) can detect CH4 concentration enhancements produced by a typical herd of beef cattle in an extensive grazing system. Open-path DCS was used to measure downwind and upwind CH4 concentrations from 10 point sources of methane simulating cattle emissions. The CH4 mole fractions and wind velocity data were used to calculate CH4 flux using an inverse dispersion model, and the simulated fluxes were then compared to the actual CH4 release rate. For a source located 60 m from the downwind path, the DCS system detected 10 nmol mol−1 CH4 horizontal concentration gradient above the atmospheric background concentration with a precision of 6 nmol mol−1 in 15 min interval. A CH4 release of 3970 g d−1 was performed, resulting in an average concentration enhancement of 24 nmol mol−1 of CH4. The calculated CH4 flux was 4002 g d−1, showing good agreement with the actual CH4 release rate. Periodically altering the downwind path, which may be needed to track moving cattle, did not adversely affect the ability of the instruments to determine the CH4 flux. These results give us confidence that CH4 flux can be determined by grazing cattle with low disturbance and direct field-scale measurements.

Measurement of unburned methane emissions in laboratory flames using mid-infrared hyperspectral imaging

In this study, we present a novel method for measuring unburned methane (CH4) emissions in laboratory flames using mid-infrared hyperspectral imaging. Given the environmental significance of methane’s global warming potential, accurately quantifying emissions from combustion processes is critical. Our approach integrates an extended-area blackbody as the infrared source and a bandpass interference filter to mitigate issues of noise, low signal levels and detector saturation. This setup enabled high-resolution spectral analysis, capturing detailed concentration and temperature maps of methane around the flame. We tracked the dynamics of methane pockets escaping the flame using the hyperspectral imaging system in high-speed camera mode, providing insights into the behavior of unburned gases, such as the velocity of methane pockets. The study demonstrates the feasibility of this technique for assessing combustion efficiency by quantifying the flow of unburned methane through a control surface. Our findings suggest that mid-infrared hyperspectral imaging is a robust tool for remote sensing of methane emissions, offering significant advancements in the accurate measurement and analysis of combustion processes, and providing a benchmarking platform for measurement approaches intended for field applications.

372 What we have learned and are still learning about enteric methane emission measurements in extensive grazing environments

Abstract Across the Western U.S., beef cattle spend considerable time grazing extensive rangelands. Enteric methane (CH4) production in grazing systems represents more than 80% of the total enteric CH4 emissions. However, more measured CH4 data from cattle grazing extensive rangelands is needed to inform measurement, reporting, modeled emissions, and to identify mitigation opportunities. The availability of pasture-ready automatic head-chamber systems (AHCS; C-Lock Inc, Rapid City, South Dakota) has allowed the determination of emissions in rangelands. In this regard, different methods to ensure an accurate determination of enteric CH4 using this measurement technique have been evaluated in recent years. An initial step to obtaining accurate enteric emissions data is ensuring efforts secure adequate AHCS visitation. Investigations in small (< 99 ac) pastures have shown that ≥ 15 visits to ≥ 55 visits in feedlot pens are adequate for robust enteric CH4 production data. Here, our goal is to examine AHCS visitation outcomes to inform the use of this technique in extensive rangeland. For two grazing seasons at the USDA ARS Central Plains Experimental Range (CPER), we have studied enteric CH4 emissions from yearling steer herds ranging in size from 26 to 60 animals in continuously stocked rangeland (Table 1). After 30 d of acclimation in 2022, 46% of individuals continued using an AHCS until the end of the drought-shortened grazing season, totaling 60 d of constant AHCS exposure. In 2023, individuals were measured first at post-weaning, and those with ≥ 15 visits to an AHCS were stocked at CPER. These steers were previously exposed to an AHCS on average 69 d earlier (range: 28 to 118). Of these 60 individuals, 68% used the two available AHCS ≥ 15 times when grazing rangeland for 76 d, totaling 137 d of discontinuous AHCS exposure. While grazing, individual visits per season were reduced in 2022 and substantially greater in 2023. At this point in our enteric CH4 emission investigation, we learned that either exposing an individual multiple times to an AHCS after weaning or doubling the days of exposure in the acclimation phase increases visitation during the measurement phase by about 20% at the herd level and 450% on an individual basis. Insights learned on rangeland have uncovered several considerations for measuring enteric CH4 emissions in extensive environments: lengthy past exposure to AHCS is ideal for adequate visitation during the measurement phase and visitation of unacclimated individuals is unlikely during the measurement phase. Further work should determine the true number of individual visits required for accurate methane measurement in extensive rangelands and evaluate 1) efficacy of different acclimation practices, 2) continued use of previously exposed animals and temporal visitation decay, and 3) alternative placement of AHCS, and use of palatable attractants to increase AHCS visitation may improve measurement of enteric CH4 emissions.

Constructing a measurement-based spatially explicit inventory of US oil and gas methane emissions (2021)

Abstract. Accurate and comprehensive quantification of oil and gas methane emissions is pivotal in informing effective methane mitigation policies while also supporting the assessment and tracking of progress towards emissions reduction targets set by governments and industry. While national bottom-up source-level inventories are useful for understanding the sources of methane emissions, they are often unrepresentative across spatial scales, and their reliance on generic emission factors produces underestimations when compared with measurement-based inventories. Here, we compile and analyze previously reported ground-based facility-level methane emissions measurements (n=1540) in the major US oil- and gas-producing basins and develop representative methane emission profiles for key facility categories in the US oil and gas supply chain, including well sites, natural-gas compressor stations, processing plants, crude-oil refineries, and pipelines. We then integrate these emissions data with comprehensive spatial data on national oil and gas activity to estimate each facility's mean total methane emissions and uncertainties for the year 2021, from which we develop a mean estimate of annual national methane emissions resolved at 0.1° × 0.1° spatial scales (∼ 10 km × 10 km). From this measurement-based methane emissions inventory (EI-ME), we estimate total US national oil and gas methane emissions of approximately 16 Tg (95 % confidence interval of 14–18 Tg) in 2021, which is ∼ 2 times greater than the EPA Greenhouse Gas Inventory. Our estimate represents a mean gas-production-normalized methane loss rate of 2.6 %, consistent with recent satellite-based estimates. We find significant variability in both the magnitude and spatial distribution of basin-level methane emissions, ranging from production-normalized methane loss rates of < 1 % in the gas-dominant Appalachian and Haynesville regions to > 3 %–6 % in oil-dominant basins, including the Permian, Bakken, and the Uinta. Additionally, we present and compare novel comprehensive wide-area airborne remote-sensing data and results for total area methane emissions and the relative contributions of diffuse and concentrated methane point sources as quantified using MethaneAIR in 2021. The MethaneAIR assessment showed reasonable agreement with independent regional methane quantification results in sub-regions of the Permian and Uinta basins and indicated that diffuse area sources accounted for the majority of the total oil and gas emissions in these two regions. Our assessment offers key insights into plausible underlying drivers of basin-to-basin variabilities in oil and gas methane emissions, emphasizing the importance of integrating measurement-based data when developing high-resolution spatially explicit methane inventories in support of accurate methane assessment, attribution, and mitigation. The high-resolution spatially explicit EI-ME inventory is publicly available at https://doi.org/10.5281/zenodo.10734299 (Omara, 2024).

Detection of Methane Leaks via a Drone-Based System for Sustainable Landfills and Oil and Gas Facilities: Effect of Different Variables on the Background-Noise Measurement

In recent years, thanks to the great diffusion of drone technology and the development of miniaturized sensors that can be connected to drones, in order to increase the sustainability of landfills and oil and gas facilities, interest in finding methane leaks and quantifying the relative flow has grown significantly. This operation requires the methane background concentration to be subtracted from the calculations. Therefore, in order to proceed with a right estimate of CH4 flows emitted, the possibility of correctly measuring or estimating the background level becomes crucial. The present work intends to illustrate the effects of different variables on the background-noise measurement in a drone-based system that uses a tunable diode laser absorption spectrometer (TDLAS). The methodology used is that of field testing; the data acquisition campaign consisted of the execution of 80 flights during which different flight variables (drone speed, flight altitude) were tested; the flights were repeated in different weather and climate conditions both during the same day and in different periods of the year. Different surfaces, similar to those found in landfill or natural gas sites, were also tested. In some of the field trials, a controlled methane release test was performed in order to verify how much the quantification of the methane flow can vary depending on the background level used. The results of the different field trials highlighted the best conditions under which to measure methane emissions with a TDLAS sensor in order to minimize the number of outliers: flight altitude not exceeding 15 m above ground level; the drone speed appears to have less impact on the results, however, it is optimal between 1 and 2 ms−1; a very sunny day produces much higher methane background levels than a cloudy one. The type of surface also significantly affects the measurement of background noise. Finally, tests conducted with a controlled methane release highlighted that different levels of background have a significant impact on the estimation of the methane flux emitted.

Quantifying methane emissions during dry season and estimating emission factors in alpacas grazing Andean grasslands

This study aimed to (1) measure methane emissions from alpacas grazing in Andean grasslands during the dry season and compare them with those of sheep under similar conditions, and (2) estimate the methane conversion and emission factor for alpacas grazing in Andean grasslands, considering methodology, animal class, and season. The comparison involved nine alpacas and nine sheep, with measurements taken for dry matter intake, diet composition, and enteric methane emissions measured with the sulfur hexafluoride technique. Alpacas selected a more digestible diet than sheep (0.62 vs. 0.50 g/g of dry matter), even with limited feed availability. Methane emissions were similar between the two species. For the second objective, the study used observations from the first objective and mean treatments from a literature review. The developed model predicted methane conversion factors, considering animal class and measurement methodology, with no significant influence observed for season. The predicted methane conversion factors (% gross energy in feed converted to methane) for alpacas grazing in Andean grasslands were 7.71 for juveniles (i.e., tuis) alpacas and 8.71 for adults, corresponding to emission factors of 6.49 and 9.77 g per alpaca and day, respectively. These results emphasize the importance of considering animal class, measurement methods, and regional variations when estimating methane emission factors for alpacas.

Measurement and quantification of methane emissions from residential gas stoves and tankless water heaters in China

Methane is a short-lived and potent greenhouse gas with a rapid warming effect. Gas stoves and water heaters, which are the most widely used domestic gas appliances (over 250 million in China), emit methane because of incomplete combustion and leakage. This study quantified the methane emissions of these two gas appliances at different ages through field measurements and laboratory tests to assess their impact on the climate. Their methane concentrations typically spiked quickly and decayed rapidly during ignition and extinguishment, but were low and stable during the steady-on state. Tankless water heaters emitted 1.69‰ (95% confidence interval: 1.44‰, 2.01‰) of the natural gas consumed, primarily during the on-pulse phase. More than four-fifths of the methane emissions from gas stoves occurred in the steady-on state, and the emission rates were positively correlated with the age of the gas stoves (r2 = 0.79, p < 0.001). Therefore, approximately 28.1 (27.5, 28.6) Gg of methane emissions annually can be attributed to Chinese residential gas appliances, corresponding to a 0.8 Mt. carbon dioxide equivalent over a 100-y scale.

Session 13. Oral Presentation for: Developing a ‘fit for purpose’ approach to measuring methane emissions

Session 13. Oral Presentation for: Developing a ‘fit for purpose’ approach to measuring methane emissions

Self‐Made Equipment for Automatic Methane Diffusion and Ebullition Measurements From Aquatic Environments

AbstractFreshwater ecosystems are believed to account for about half of global methane emissions, but this estimate is uncertain due to few measurements in some geographical regions and most important for our purposes, large local variations. We propose a simple, cheap (&lt;200€), and effective solution to the urgent need for equipment that can provide accurate data on methane emission at high spatial and temporal resolution for many days, across many ecosystems and regions, and with limited inspection. A low‐cost metal oxide semiconductor sensor, placed in a floating chamber equipped with an air pump to flush the chamber's headspace at regular intervals, provides frequent and accurate high‐resolution measurements of diffusive and ebullitive methane emissions from lakes and rivers. We made several improvements that yield more useful data and enable the setup to operate for several days without visual inspection. To test the accuracy of the equipment, we compared its measurements of methane emission to parallel measurements by an expensive, commercially available laser sensor. The correspondence was excellent (R2 ≥ 0.94) and the deviation of measurements was minimal at fluxes within ranges encountered in the field. We also designed an R‐package (FluxSeparator), which associates the large sensor‐generated data sets with diffusive and ebullitive flux activity. Both the sensor setup and the R‐package are flexible and have been made publicly available to encourage others to use and further improve the equipment and calculations.

A satellite constellation dedicated to frequently monitor methane emissions from oil and gas facilities around the world

This paper discusses GHGSat’s pioneering operating satellites dedicated to high-resolution measurements of methane emissions. We demonstrate their role as an integral part of an emissions intensity improvement strategy. The instrument on board each satellite uses spectroscopy principles to detect and quantify methane emissions, exhibiting a spatial resolution of less than 30 m. A discussion on how this constellation can be used as a key system in the mitigation of emissions is presented. Results reflect observations taken with GHGSat’s satellites. Recent examples of oil and gas emitting facilities around the world are shown followed by how this constellation can serve three objectives: (1) emissions mitigation; (2) regulatory compliance; and (3) a system to achieve voluntary efforts such as OGMP 2.0. The intention is to show that there isn’t a one-size-fits-all solution, but that the use of a satellite constellation is a complimentary and efficient way of monitoring for large leaks with increased frequency. This paper also reviews GHGSat’s top-down approach through its aircraft sensor technology as another solution for monitoring smaller leaks. Mitigation success stories are discussed providing opportunities for achievement of regulatory certifications in regions like the United States, Australia and Iraq. The resulting datasets are integrated into GHGSat’s ESRI ArcGIS-based portal, SPECTRA, to facilitate the interpretation of its high-resolution measurements, giving further insights through the available analytics layers. This platform provides situational awareness of methane emissions to operators, creating opportunities for mitigation.

Developing a ‘fit for purpose’ approach to measuring methane emissions

Tackling methane emissions from fossil fuel operations represents one of the best near- and medium-term opportunities for limiting the effects of climate change. Over the last few years, independent methane studies have challenged the accuracy and completeness of publicly disclosed emissions estimates. To address this, new methane accounting and reporting frameworks have been developed. Central to these frameworks are key principles linked to measurement, monitoring, reporting, verification (MMRV) and reduction. Woodside has taken specific actions to measure and reduce its methane emissions and is developing a pathway to embed ongoing and sustainable measurements technologies in its operations. Previously, Woodside discussed the management and valuation of methane reductions, this paper will describe the approach taken to develop methane measurement plans including (i) the objective of measurement plans, (ii) measurement technology attributes and (iii) the identification of measurement technology use cases. It also overviews measurement techniques such as satellite, aerial, drone, handheld and continuous monitoring which can form part of a curated multi-scale approach to MMRV across a portfolio of assets.

9 Use of new technology to measure methane emissions

Abstract Over recent decades, the impact of human-induced climate change and the role of ruminant agriculture has been of growing concern for both the public and the scientific community. This has led to rapid advancements in technology needed to measure methane emissions accurately and precisely. Primarily, these advancements have been focused on measurements of enteric methane, with the proliferation of GreenFeed emission measurement systems (GEM; C-Lock, Inc; Rapid City, SD) being utilized by animal scientists across the world. The GEM relies on spot measurements collected in a portable head-box, either in a freestall or on a trailer. The GEM uses bait feed to entice animals to place their head into the head-box to collect measurements. Use of respiration chambers or head-boxes are still considered the “gold standard”, but the GEM allows for quantification in production environments and with greater number of animals. While enteric emissions are the primary source of methane from ruminant agriculture, manure methane emissions account for 15.8% of direct emissions from cattle in the U.S. This emission source is a significant contributor to confined feeding operations’ greenhouse gas emissions (GHG), where consolidation and changes in manure handling practices have occurred over the last several decades. From 2010 to 2020, manure methane emissions were a larger contributor to climate warming than enteric methane (90.8 MMT CO2-we vs. 89.2 MMT CO2-we, respectively) when calculated using the new GWP* metric. However, few advancements have been made in quantifying emissions from manure, with the cost-effective static chamber methodology still widely used. This technique allows for the determination of temporal gas concentration change in a known volume of air with a PVC cylinder, inserted 5-10 cm in the soil and posteriorly closed with a PVC lid to generate “known volume” headspace. However, this method does have known limitations on spatial and temporal flux calculations. These limitations include: the PVC chamber may alter the soil microenvironment thereby altering soil GHG flux estimates; they have potential for technician bias; and are short term monitoring, limiting interpretations to that snapshot in time and making comparisons across experiments difficult. Differing measuring techniques, such as eddy covariance and dual-comb, that more accurately and precisely monitor the soil-atmosphere interface may help better understand gas fluxes from livestock systems. Key Word: cattle, enteric, manure, methane

Подземные источники балки Пещерная озера Баскунчак: гидрохимические особенности и эмиссия парниковых газов

For the first time, full-scale measurements of methane and carbon dioxide emissions by the chamber method were carried out in summer for groundwater sources discharged in the valley of the Peshernaya Gulch creek, located in the north-west of Lake Baskunchak. pH values, concentrations of CH4, basic ions, gross Fe and Mn were determined in the water of the sources; concentrations of CH4, H2S, organic matter, Eh and pH values, density and humidity were determined in various layers of bottom sediments (up to 27 cm). A detailed description of the identified groundwater sources was carried out, their primary morphometric and morphological characteristics were measured, as well as the flow rate. It was found that more than 10 ascending karst sources of groundwater are discharged in the Peshchernaya beam, 5 of which were active during the research period and mainly confined to the left screw of the beam. The active sources of the left screw of the beam are characterized by a small flow rate and are sodium chloride brines with a mineralization of 93.9–107.1 g/l. The bottom sediments accumulating in the sinkholes of underground sources are characterized by a neutral acid-base environment and restorative conditions. The concentrations of CH4 and ∑H2S in the sediments of the sources varied, respectively, in the range of 0.08–0.77 µg/g vl.o. and 0.023–2.63 mg/g vl.o. with minimal values for both gases in the lower less reduced layer with a low content of Sorg. The concentration of methane in the water of active sources varied from 26.3 up to 38.4 µl/l and was on average 2 times higher than in the waters of a stream fed by them and an inactive source. The specific methane flux from the water surface of active sources varied in the range of 0.6–1.5 mg/(m2∙h), which is 2 orders of magnitude lower than the specific CO2 flux of 46.4–106.1 mg/(m2∙h). The isotopic composition of carbon (δ13C) CH4 and CO2 measured in gas bubbles rising from the bottom of one of the ascending sources indicates the modern biochemical genesis of these greenhouse gases.

Analyses of plasma metabolites using a high performance four-channel CIL LC-MS method and identification of metabolites associated with enteric methane emissions in beef cattle.

Reducing enteric methane (one greenhouse gas) emissions from beef cattle not only can be beneficial in reducing global warming, but also improve efficiency of nutrient utilization in the production system. However, direct measurement of enteric methane emissions on individual cattle is difficult and expensive. The objective of this study was to detect plasma metabolites that are associated with enteric methane emissions in beef cattle. Average enteric methane emissions (CH4) per day (AVG_DAILYCH4) for each individual cattle were measured using the GreenFeed emission monitoring (GEM) unit system, and beef cattle with divergent AVG_DAILYCH4 from Angus (n = 10 for the low CH4 group and 9 for the high CH4 group), Charolais (n = 10 for low and 10 for = high), and Kinsella Composite (n = 10 for low and 10 for high) populations were used for plasma metabolite quantification and metabolite-CH4 association analyses. Blood samples of these cattle were collected near the end of the GEM system tests and a high performance four-channel chemical isotope labeling (CIL) liquid chromatography (LC) mass spectrometer (MS) method was applied to identify and quantify concentrations of metabolites. The four-channel CIL LC-MS method detected 4235 metabolites, of which 1105 were found to be significantly associated with AVG_DAILYCH4 by a t-test, while 1305 were significantly associated with AVG_DAILYCH4 by a regression analysis at p<0.05. Both the results of the t-test and regression analysis revealed that metabolites that were associated with enteric methane emissions in beef cattle were largely breed-specific whereas 4.29% to 6.39% CH4 associated metabolites were common across the three breed populations and 11.07% to 19.08% were common between two breed populations. Pathway analyses of the CH4 associated metabolites identified top enriched molecular processes for each breed population, including arginine and proline metabolism, arginine biosynthesis, butanoate metabolism, and glutathione metabolism for Angus; beta-alanine metabolism, pyruvate metabolism, glycolysis / gluconeogenesis, and citrate cycle (TCA cycle) for Charolais; phenylalanine, tyrosine and tryptophan biosynthesis, phenylalanine metabolism, arginine biosynthesis, and arginine and proline metabolism for Kinsella Composite. The detected CH4 associated metabolites and enriched molecular processes will help understand biological mechanisms of enteric methane emissions in beef cattle. The detected CH4 associated plasma metabolites will also provide valuable resources to further characterize the metabolites and verify their utility as biomarkers for selection of cattle with reduced methane emissions.

ENTERIC METHANE PRODUCTION IN RUMINANTS: ITS EFFECT ON GLOBAL WARMING AND MITIGATION STRATEGIES-A REVIEW

Anthropic activities produce around 2/3 share of the total methane emission in the world, with the livestock sector being the primary contributor. Methane is a potent greenhouse gas, exhibiting a warming effect more than 21 times that of carbon dioxide, and is produced by microbes called methanogens during anaerobic fermentation. The release of methane from ruminants indicating a loss of feed energy that has the potential to elevate production. Economic and population growth will increase milk and meat demand, increasing CH4 production from the livestock sector. Various approaches including feed manipulation, supplementation of feed additives, management practices, genetic selection and vaccinations all were aimed at mitigating CH4 from the livestock sector. These measures change the composition of rumen and alter the working of methane-producing microbes. The addition of feed additives reduces the CH4 emission but human well-being limits their usage. Methane inhibitors, like those with a hydrogen sink property that has no adverse effects on rumen microbe populations, are considered ideal for reducing emissions. Research also shows that methane emission is a heritable and repeatable trait and that genomic and genetic traits present a considerable opportunity to minimize methane emissions from ruminants the accuracy of methane measurements is crucial and attention to background information in publications regarding measurement context and methods is necessary for comprehensive interpretation of results. Each method for measuring methane emissions from livestock has limitations tied to its original intent of use. Standardization within and between techniques, especially in respiration chambers, SF6 and Greenfeed Emission Monitoring System, can enhance result reliability. However, using these technologies beyond their intended purpose is risky, and extrapolating estimations may lead to unintended consequences. Combining different methods may offer the most comprehensive approach, but further research is needed to validate and compare individual methods, especially in wide-ranging production systems and to develop standardization protocols.

Onshore methane emissions measurements from the oil and gas industry: a scoping review

Abstract Research on methane (CH4) emissions from the oil and gas (O&amp;G) industry informs policies, regulations, and international initiatives that target reductions. However, there has been little integration and synthesis of the literature to document the state of knowledge, identify gaps, and determine key insights that can guide research priorities and mitigation. To address this, we performed a scoping review of 237 English-language peer-reviewed articles on CH4 emissions from onshore O&amp;G sources, charting data on five research themes: publication trends, geography, measurement levels and methods, emissions sources, and emissions rates. Almost all articles (98%) were published between 2012 and 2022 with an increasing publication rate, indicating a nascent and evolving understanding of the science. Most articles (72%) focused on CH4 emissions from the U.S. O&amp;G industry and were written by U.S.-based authors (69%), while other major O&amp;G-producing countries like Saudi Arabia, Russia, and China were under-represented. Upstream was the most frequently studied supply chain segment, where U.S.-focused articles accounted for 75% of the research. Nearly half the articles (43%) included in the review reported site-level measurements, limiting the identification of equipment- and component-level emissions sources and root cause. Articles that measured or identified equipment-level sources (18%) noted high emissions from tanks, unlit flares, and compressors. The most common stand-off measurement platforms were vehicles and aircraft, while the use of satellites increased in articles published since 2019. Reported emissions profiles were consistently heavy-tailed and indicate method-based and geographic differences in magnitude and skew. All articles (n = 26) that compared inventory- to measurement-based estimates of emissions found large discrepancies in that inventories under-estimated the latter by a factor of 1.2–10 times. We recommend future research focus on: (i) field-based emissions studies for under-represented regions and source categories, (ii) identifying root causes and linking measurements to mitigation, and (iii) multi-level measurement integration.

A low-methane rice with high-yield potential realized via optimized carbon partitioning

Global rice cultivation significantly contributes to anthropogenic methane emissions. The methane emissions are caused by methane-producing microorganisms (methanogenic archaea) that are favoured by the anoxic conditions of paddy soils and small carbon molecules released from rice roots. However, different rice cultivars are associated with differences in methane emission rates suggesting that there is a considerable natural variation in this trait. Starting from the hypothesis that sugar allocation within a plant is an important factor influencing both yields and methane emissions, the aim of this study was to produce high-yielding rice lines associated with low methane emissions. In this study, the offspring (here termed progeny lines) of crosses between a newly characterized low-methane rice variety, Heijing 5, and three high-yielding elite varieties, Xiushui, Huayu and Jiahua, were selected for combined low-methane and high-yield properties. Analyses of total organic carbon and carbohydrates showed that the progeny lines stored more carbon in above-ground tissues than the maternal elite varieties. Also, metabolomic analysis of rhizospheric soil surrounding the progeny lines showed reduced levels of glucose and other carbohydrates. The carbon allocation, from roots to shoots, was further supported by a transcriptome analysis using massively parallel sequencing of mRNAs that demonstrated elevated expression of the sugar transporters SUT-C and SWEET in the progeny lines as compared to the parental varieties. Furthermore, measurement of methane emissions from plants, grown in greenhouse as well as outdoor rice paddies, showed a reduction in methane emissions by approximately 70 % in the progeny lines compared to the maternal elite varieties. Taken together, we report here on three independent low-methane-emission rice lines with high yield potential. We also provide a first molecular characterisation of the progeny lines that can serve as a foundation for further studies of candidate genes involved in sugar allocation and reduced methane emissions from rice cultivation.

Measurements of Methane Emissions from a Biofertilizer Storage Tank Using Ground-Based Hyperspectral Imaging and Flux Chambers.

Open storages of organic material represent potentially large sources of the greenhouse gas methane (CH4), an emissions source that will likely become more common as a part of societal efforts toward sustainability. Hence, monitoring and minimizing CH4 emissions from such facilities are key, but effective assessment of emissions without disturbing the flux is challenging. We demonstrate the capacity of using a novel high-resolution hyperspectral camera to perform sensitive CH4 flux assessments at such facilities, using as a test case a biofertilizer storage tank for residual material from a biogas plant. The camera and simultaneous conventional flux chamber measurements showed emissions of 6.0 ± 1.3 and 13 ± 5.7 kg of CH4 h-1, respectively. The camera measurements covered the whole tank surface of 1104 m2, and the chamber results were extrapolated from measurements over 5 m2. This corresponds to 0.7-1.4% of the total CH4 production at the biogas plant (1330 N m3 h-1 corresponding to 950 kg h-1). The camera could assess the entire tank emission in minutes without disturbing normal operations at the plant and revealed additional unknown emissions from the inlet to the tank (17 g of CH4 h-1) and during the loading of the biofertilizer into trucks (3.1 kg of CH4 h-1 during loading events). This study illustrates the importance of adequate measurement capacity to map methane fluxes and to verify that methane emission mitigation efforts are effective. Given the high methane emissions observed, it is important to reduce methane emissions from open storage of organic material, for example by improved digestion in the biogas reactor, precooling of sludge before storage, or building gastight storage tanks with sealed covers. We conclude that hyperspectral, ground-based remote sensing is a promising approach for greenhouse gas monitoring and mitigation.

Landfill gas collection efficiency: Categorization of data from existing in-situ measurements

Landfill methane emissions are commonly estimated using cover-type dependent default collection efficiency values, with a first-order decay model or measured gas collection. Current default collection efficiencies used in the United States were predominately derived from 4 studies conducted during or prior to 2007 that relied on flux chambers. Flux chambers are limited by small sample sizes, placement restrictions, and the inability to measure emissions from gas or leachate collection systems. Since 2007, over 14 new studies have been completed using more advanced technologies that allow for direct measurement of methane plumes from most or all of a landfill’s surface. On average, these measurements are 2–3 times greater than emissions predicted by current models and collection efficiency defaults. In lieu of measuring emissions from all landfills, updating collection efficiency defaults can bring modeled emissions into better alignment with measurements. To this end, collection efficiency estimates derived from measured data were categorized into cover types and then adjusted to account for cases where whole plume measurement was an amalgamation of multiple cover types. The resultant adjusted default values were 41% for daily cover, 69% for intermediate cover, and 71% for final cover. Direct measurement of landfill methane emissions is preferrable to account for the full range of variables driving landfill emissions, including collection system design and operation. However, applying these updated defaults back into the landfill emission models eliminates underprediction of landfill emissions for the dataset reviewed, and would provide a more accurate estimate of landfill gas emissions where measurements are unavailable.

The first data on the concentration and emission of methane and carbon dioxide in the underground sources of the Peshernaya beam of Lake Baskunchak

For the first time, full-scale measurements of methane and carbon dioxide emissions by the chamber method were carried out in summer for groundwater sources discharged in the valley of the creek of the Peshernaya beam, located in the north-west of Lake Baskunchak. The values of pH, temperature, concentration of basic ions and methane were determined in the water of the sources. A detailed description of the identified groundwater sources was carried out, their primary morphometric and morphological characteristics were measured, as well as the flow rate. It has been established that more than ten ascending karst groundwater sources are discharged in the Peshernaya gully, five of which were active during the research period and were mainly confined to the left branch of the gully. The active sources of the left side of the beam are characterized by a small flow rate and are sodium chloride brines with a mineralization of 93.9–107.1 g/l. The concentration of methane in the water of active sources varied between 26.3–38.4 µl/l and was on average more than 2 times higher than in the waters of the stream fed by them and an inactive source. The specific flow of methane from the water surface of active sources varied in the range of 0.6–1.5 mg/(m2·hour), which is 2 orders of magnitude lower than the specific flow of CO2, which is 46.4–106.1 mg/(m2·hour).