Source Of Methane Research Articles

Spectral Fingerprinting of Methane from Hyper-Spectral Sounder Measurements Using Machine Learning and Radiative Kernel-Based Inversion

Satellite-based hyper-spectral infrared (IR) sensors such as the Atmospheric Infrared Sounder (AIRS), the Cross-track Infrared Sounder (CrIS), and the Infrared Atmospheric Sounding Interferometer (IASI) cover many methane (CH4) spectral features, including the ν1 vibrational band near 1300 cm−1 (7.7 μm); therefore, they can be used to monitor CH4 concentrations in the atmosphere. However, retrieving CH4 remains a challenge due to the limited spectral information provided by IR sounder measurements. The information required to resolve the weak absorption lines of CH4 is often obscured by interferences from signals originating from other trace gases, clouds, and surface emissions within the overlapping spectral region. Consequently, currently available CH4 data product derived from IR sounder measurements still have large errors and uncertainties that limit their application scope for high-accuracy climate and environment monitoring applications. In this paper, we describe the retrieval of atmospheric CH4 profiles using a novel spectral fingerprinting methodology and our evaluation of performance using measurements from the CrIS sensor aboard the Suomi National Polar-orbiting Partnership (SNPP) satellite. The spectral fingerprinting methodology uses optimized CrIS radiances to enhance the CH4 signal and a machine learning classifier to constrain the physical inversion scheme. We validated our results using the atmospheric composition reanalysis results and data from airborne in situ measurements. An inter-comparison study revealed that the spectral fingerprinting results can capture the vertical variation characteristics of CH4 profiles that operational sounder products may not provide. The latitudinal variations in CH4 concentration in these results appear more realistic than those shown in existing sounder products. The methodology presented herein could enhance the utilization of satellite data to comprehend methane’s role as a greenhouse gas and facilitate the tracking of methane sources and sinks with increased reliability.

The hidden roots of wetland methane emissions.

Wetlands are the largest natural source of methane (CH4 ) globally. Climate and land use change are expected to alter CH4 emissions but current and future wetland CH4 budgets remain uncertain. One important predictor of wetland CH4 flux, plants, play an important role in providing substrates for CH4 -producing microbes, increasing CH4 consumption by oxygenating the rhizosphere, and transporting CH4 from soils to the atmosphere. Yet, there remain various mechanistic knowledge gaps regarding the extent to which plant root systems and their traits influence wetland CH4 emissions. Here, we present a novel conceptual framework of the relationships between a range of root traits and CH4 processes in wetlands. Based on a literature review, we propose four main CH4 -relevant categories of root function: gas transport, carbon substrate provision, physicochemical influences and root system architecture. Within these categories, we discuss how individual root traits influence CH4 production, consumption, and transport (PCT). Our findings reveal knowledge gaps concerning trait functions in physicochemical influences, and the role of mycorrhizae and temporal root dynamics in PCT. We also identify priority research needs such as integrating trait measurements from different root function categories, measuring root-CH4 linkages along environmental gradients, and following standardized root ecology protocols and vocabularies. Thus, our conceptual framework identifies relevant belowground plant traits that will help improve wetland CH4 predictions and reduce uncertainties in current and future wetland CH4 budgets.

Single-blind test of nine methane-sensing satellite systems from three continents

Abstract. Satellite-based remote sensing enables detection and mitigation of large point sources of climate-warming methane. These satellites will have the greatest impact if stakeholders have a clear-eyed assessment of their capabilities. We performed a single-blind test of nine methane-sensing satellites from three continents and five countries, including both commercial and government satellites. Over 2 months, we conducted 82 controlled methane releases during satellite overpasses. Six teams analyzed the resulting data, producing 134 estimates of methane emissions. Of these, 80 (58 %) were correctly identified, with 46 true positive detections (34 %) and 34 true negative non-detections (25 %). There were 41 false negatives, in which teams missed a true emission, and 0 false positives, in which teams incorrectly claimed methane was present. All eight satellites that were given a nonzero emission detected methane at least once, including the first single-blind evaluation of the EnMAP, Gaofen 5, and Ziyuan 1 systems. In percent terms, quantification error across all satellites and teams is similar to aircraft-based methane remote sensing systems, with 55 % of mean estimates falling within ±50 % of the metered value. Although teams correctly detected emissions as low as 0.03 metric tons of methane per hour, it is unclear whether detection performance in this test is representative of real-world field performance. Full retrieval fields submitted by all teams suggest that in some cases it may be difficult to distinguish true emissions from background artifacts without a known source location. Cloud interference is significant and appears to vary across teams and satellites. This work confirms the basic efficacy of the tested satellite systems in detecting and quantifying methane, providing additional insight into detection limits and informing experimental design for future satellite-focused controlled methane release testing campaigns.

Ground-Based Mobile Measurements to Track Urban Methane Emissions from Natural Gas in 12 Cities across Eight Countries.

To mitigate methane emission from urban natural gas distribution systems, it is crucial to understand local leak rates and occurrence rates. To explore urban methane emissions in cities outside the U.S., where significant emissions were found previously, mobile measurements were performed in 12 cities across eight countries. The surveyed cities range from medium size, like Groningen, NL, to large size, like Toronto, CA, and London, UK. Furthermore, this survey spanned across European regions from Barcelona, ES, to Bucharest, RO. The joint analysis of all data allows us to focus on general emission behavior for cities with different infrastructure and environmental conditions. We find that all cities have a spectrum of small, medium, and large methane sources in their domain. The emission rates found follow a heavy-tailed distribution, and the top 10% of emitters account for 60-80% of total emissions, which implies that strategic repair planning could help reduce emissions quickly. Furthermore, we compare our findings with inventory estimates for urban natural gas-related methane emissions from this sector in Europe. While cities with larger reported emissions were found to generally also have larger observed emissions, we find clear discrepancies between observation-based and inventory-based emission estimates for our 12 cities.

Salinity causes widespread restriction of methane emissions from small inland waters

Inland waters are one of the largest natural sources of methane (CH4), a potent greenhouse gas, but emissions models and estimates were developed for solute-poor ecosystems and may not apply to salt-rich inland waters. Here we combine field surveys and eddy covariance measurements to show that salinity constrains microbial CH4 cycling through complex mechanisms, restricting aquatic emissions from one of the largest global hardwater regions (the Canadian Prairies). Existing models overestimated CH4 emissions from ponds and wetlands by up to several orders of magnitude, with discrepancies linked to salinity. While not significant for rivers and larger lakes, salinity interacted with organic matter availability to shape CH4 patterns in small lentic habitats. We estimate that excluding salinity leads to overestimation of emissions from small Canadian Prairie waterbodies by at least 81% ( ~ 1 Tg yr−1 CO2 equivalent), a quantity comparable to other major national emissions sources. Our findings are consistent with patterns in other hardwater landscapes, likely leading to an overestimation of global lentic CH4 emissions. Widespread salinization of inland waters may impact CH4 cycling and should be considered in future projections of aquatic emissions.

Elevated methane flux in a tropical peatland post-fire is linked to depth-dependent changes in peat microbiome assembly

Fires in tropical peatlands extend to depth, transforming them from carbon sinks into methane sources and severely limit forest recovery. Peat microbiomes influence carbon transformations and forest recovery, yet our understanding of microbiome shifts post-fire is currently limited. Our previous study highlighted altered relationships between the peat surface, water table, aboveground vegetation, and methane flux after fire in a tropical peatland. Here, we link these changes to post-fire shifts in peat microbiome composition and assembly processes across depth. We report kingdom-specific and depth-dependent shifts in alpha diversity post-fire, with large differences at deeper depths. Conversely, we found shifts in microbiome composition across all depths. Compositional shifts extended to functional groups involved in methane turnover, with methanogens enriched and methanotrophs depleted at mid and deeper depths. Finally, we show that community shifts at deeper depths result from homogeneous selection associated with post-fire changes in hydrology and aboveground vegetation. Collectively, our findings provide a biological basis for previously reported methane fluxes after fire and offer new insights into depth-dependent shifts in microbiome assembly processes, which ultimately underlie ecosystem function predictability and ecosystem recovery.

Nitrous Oxide Emissions during Cultivation and Fallow Periods from Rice Paddy Soil under Urea Fertilization

Rice cultivation serves as a significant anthropogenic source of methane (CH4) and nitrous oxide (N2O). Although N2O emissions remain relatively small compared to CH4 emissions, they are remarkably affected by nitrogen-fertilized soil conditions during rice cultivation. While numerous studies have investigated nitrous oxide emissions in response to nitrogen fertilization, existing research assessing nitrous oxide emissions based on nitrogen fertilizer levels has often been limited to cultivation periods. Therefore, there is a need for comprehensive analyses covering the entire year, including the dry periods, to address nitrous oxide emissions as an important source throughout the entire agricultural cycle. In this case study, we investigated the characteristics of N2O emissions in a central region of South Korea, where a single rice-cropping cycle occurs annually over a span of three whole years, from May 2020 to May 2023. We investigated the impact of variations in temperature and soil moisture on N2O emissions during rice cultivation and fallow periods. In this context, we attempted to discover the complex dynamics of N2O emissions by comparing longer fallow periods with the rice cultivation periods and extended non-dry periods with irrigated periods. We discovered that the greater contribution of cumulative N2O emissions during the fallow period made a much greater contribution (up to approximately 90%) to the whole-year N2O emissions than those during the rice cultivation period. During the fallow period from rice harvest to rice planting in the following year, variations in N2O emissions were associated with high-flux events after rainy periods on dry soils. This highlights the considerable influence of soil moisture content and weather conditions on N2O emissions during the fallow period. This affects high emission events, which in turn significantly impact the cumulative emissions over the entire period. We underscore that assessing N2O emissions solely based on the rice cultivation period would underestimate annual emissions. To prevent underestimation of N2O emissions, periodic gas collection throughout a year covering both rice cultivation and fallow phases is required in alignment with the monitoring of different temperature and soil moisture conditions. We captured statistical differences in cumulative N2O emissions due to nitrogen fertilization treatments across the three years. However, no significant difference was observed in the three-year average emissions among the different (one, one-and-a-half, and double) nitrogen fertilization treatments, with the exception of the control treatment (no fertilization). Based on the findings, we recommend at least three whole-year evaluations to ensure the estimation accuracy of N2O emissions under different nitrogen fertilization conditions. The findings from this study could help prepare the further revision or refinement of N2O emission factors from rice cultivation in the national greenhouse gas inventories defined by the inter-governmental panel on climate change (IPCC).

SPATIAL VARIABILITY OF METHANE EMISSIONS FROM SOILS OF WET FORESTS: A BRIEF REVIEW

SPATIAL VARIABILITY OF METHANE EMISSIONS FROM SOILS OF WET FORESTS: A BRIEF REVIEW

Changes in inundation drive carbon dioxide and methane fluxes in a temperate wetland

Wetlands cycle carbon by being net sinks for carbon dioxide (CO2) and net sources of methane (CH4). Daily and seasonal temporal patterns, dissolved oxygen (DO) availability, inundation status (flooded or dry/partially flooded), water depth, and vegetation can affect the magnitude of carbon uptake or emissions, but the extent and interactive effects of these variables on carbon gas fluxes are poorly understood. We characterized the linkages between carbon fluxes and these environmental and temporal drivers at the Old Woman Creek National Estuarine Research Reserve (OWC), OH. We measured diurnal gas flux patterns in an upstream side channel (called the cove) using chamber measurements at six sites (three vegetated and three non-vegetated). We sampled hourly from 7 AM to 7 PM and monthly from July to October 2022. DO concentrations and water levels were measured monthly. Water inundation status had the most influential effect on carbon fluxes with flooded conditions supporting higher CH4 fluxes (0.39 μmol CH4 m−2 s−1; −1.23 μmol CO2 m−2 s−1) and drier conditions supporting higher CO2 fluxes (0.03 μmol CH4 m−2 s−1; 0.86 μmol CO2 m−2 s−1). When flooded, the wetland was a net CO2 sink; however, it became a source for both CH4 and CO2 when water levels were low. We compared chamber-based gas fluxes from the cove in flooded (July) and dry (August) months to fluxes measured with an eddy covariance tower whose footprint covers flooded portions of the wetland. The diurnal pattern of carbon fluxes at the tower did not vary with changing water levels but remained a CO2 sink and a CH4 source even when the cove where we performed the chamber measurements dried out. These results emphasize the role of inundation status on wetland carbon cycling and highlight the importance of fluctuating hydrologic patterns, especially hydrologic drawdowns, under changing climatic conditions.

Mid-season drain severity impacts on rice yields, greenhouse gas emissions and heavy metal uptake in grain: evidence from on-farm studies

Context or ProblemFlooded rice systems produce an important staple crop but are a source of methane (CH4) and arsenic (As) exposure. Introducing non-continuous flooding events can decrease seasonal CH4 emissions and grain As concentration. A single mid-season drain (MD: a 7-to 10-day soil drying period during the mid-season) is easier for farmers to manage than multiple drain events (e.g. alternate wetting and drying). Previous research has shown that a MD can accomplish these goals without yield reduction. However, depending on soils and precipitation, the soil drying severity during a MD can vary substantially. Objective or Research QuestionThe objectives of this study were to compare a MD to the farmer practice under on-farm conditions with respect to yields, greenhouse gas (GHG) emissions and As and cadmium (Cd – which can increase with non-continuous flooding). Second, to quantify the relationship between soil drying severity during the MD and the reduction in CH4 emissions and grain As. MethodsA three-year study with seven on-farm trials was implemented. Each trial had two treatments: a MD and the farmer practice. Grain yields, GHG emissions, and grain As and Cd concentrations were quantified for each treatment. ResultsGrain yields were similar between treatments. The MD decreased seasonal CH4 emissions by 20–77% (average of 52%), with the magnitude of reduction being related to soil-drying severity during the MD. Combining previous on-station data with this on-farm data, indicates that for every 1% reduction in soil gravimetric water content (GWC), seasonal CH4 emissions were reduced by 2.5% (r2 = 0.47). With MD, N2O emissions increased (average = 0.25 kg N2O-N ha−1), but accounted for only 3% of the global warming potential. The MD decreased grain As concentration (by 20% on average, but not related to soil drying severity), and there was no effect on grain Cd concentrations. ConclusionsGiven these results, an MD has similar GHG mitigation potential to other non-continuous flooding practices that require more drain periods and may be more difficult to implement. These results indicate that a MD is a viable on-farm management practice for GHG mitigation and reducing grain As concentration with limited risk of yield reduction. Implications or SignificanceThis is the first research that has documented the relationship between soil drying severity and reduction in CH4 emissions across soils. This relationship is a potentially useful tool for on-farm monitoring, but will need to be developed further across more locations.

Radiative forcing of methane emission completely offsets net carbon dioxide uptake in a temperate freshwater marsh from the present to future

Wetlands serve a dual function as carbon dioxide (CO2) sinks and methane (CH4) sources. Emissions of CH4 from wetlands have long been considered to potentially offset net cooling effect of CO2 uptakes, yet there is a paucity of detailed knowledge on the tradeoff of wetland CO2 and CH4 fluxes under current and future climate conditions. This study used the eddy covariance technique to measure ecosystem-scale CO2 and CH4 fluxes in a Phragmites australis-dominated freshwater marsh from 2020 to 2023. Furthermore, we projected future CO2 and CH4 fluxes based on six Earth System Models under four Representative Concentration Pathways (RCP). Our results show that the P. australis marsh is a large CO2 sink and a hotspot for CH4 emissions, with a 3-year annual average net CO2 uptake of 926 g CO2 m‒2 and CH4 emission of 42 g CH4 m‒2. The negative radiative forcing caused by CO2 uptake was entirely counterbalanced by wetland CH4 emissions, resulting in a mean annual net CO2-equivalent (CO2-eq) emission of 970 g CO2-eq m‒2 over a 100-year time horizon. The interannual variability of net CO2-eq fluxes was driven by hydrological variations, with lower net CO2-eq fluxes occurring during dry years. In future scenarios, the radiative forcing of CH4 emissions could persistently and completely offset the net CO2 uptake in this freshwater marsh. Alarmingly, future net CO2-eq fluxes exhibit a significant increasing trend under the RCP8.5 scenario because CH4 emissions are more responsive than CO2 uptake to increasing temperatures and precipitation. Conversely, under the RCP2.6 scenario, future net CO2-eq fluxes show a significant downward trend, primarily due to the slowdown of positive warming-wetland CH4 feedback and the radiation-driven continuous rise in CO2 uptake. Overall, our findings affirm the role of wetlands in sequestrating atmospheric CO2 but highlight the current and growing importance of wetland CH4 emissions in regulating wetland-climate feedback.

Bio-Waste from Urban and Rural Areas as a Source of Biogas and Methane—A Case Study from Poland

The growing volume of household waste, especially bio-waste, poses a significant challenge to waste management systems. In Poland, bio-waste accounts for almost one third of total waste generation. To address this challenge, in the context of optimising the waste biomass value chain, we are investigating the potential of methane fermentation to convert bio-waste into valuable end products in the form of digestate (organic recycling) and biogas (a renewable energy source with a wide range of downstream applications). This paper presents the moisture content, loss on ignition and biogas and methane production efficiency for bio-waste and for the seven types of waste that are the main constituents of selectively collected bio-waste (meat, other edible waste (dairy), fruits and vegetables, grass, leaves, branches and the < 10 mm fraction). Data on the technological properties of bio-waste and its constituents may be of interest to a range of stakeholders. The average moisture content ranged from 41.9% (<10 mm fraction and others) to 84.4% (fruits and vegetables), and the average organic matter content of the dry weight of the waste ranged from 37.8% (<10 mm fraction and others) to 88.7% (edible constituents other than meat and fruits and vegetables). The bio-waste had an average moisture content of 71.3 ± 1.7% and loss on ignition of 68.6 ± 1.7%. Biogas production from selectively collected bio-waste ranged from 285 to 404 Ndm3∙kg−1 DM (mean: 347 ± 53 Ndm3∙kg−1 DM), and methane production ranged from 191 to 271 Ndm3∙kg−1 DM (mean: 215 ± 33 Ndm3∙kg−1 DM).

Distinct microbial hydrogen and reductant disposal pathways explain interbreed variations in ruminant methane yield.

Ruminants are essential for global food security, but these are major sources of the greenhouse gas methane. Methane yield is controlled by the cycling of molecular hydrogen (H2), which is produced during carbohydrate fermentation and is consumed by methanogenic, acetogenic, and respiratory microorganisms. However, we lack a holistic understanding of the mediators and pathways of H2 metabolism and how this varies between ruminants with different methane-emitting phenotypes. Here, we used metagenomic, metatranscriptomic, metabolomics, and biochemical approaches to compare H2 cycling and reductant disposal pathways between low-methane-emitting Holstein and high-methane-emitting Jersey dairy cattle. The Holstein rumen microbiota had a greater capacity for reductant disposal via electron transfer for amino acid synthesis and propionate production, catalyzed by enzymes such as glutamate synthase and lactate dehydrogenase, and expressed uptake [NiFe]-hydrogenases to use H2 to support sulfate and nitrate respiration, leading to enhanced coupling of H2 cycling with less expelled methane. The Jersey rumen microbiome had a greater proportion of reductant disposal via H2 production catalyzed by fermentative hydrogenases encoded by Clostridia, with H2 mainly taken up through methanogenesis via methanogenic [NiFe]-hydrogenases and acetogenesis via [FeFe]-hydrogenases, resulting in enhanced methane and acetate production. Such enhancement of electron incorporation for metabolite synthesis with reduced methanogenesis was further supported by two in vitro measurements of microbiome activities, metabolites, and public global microbiome data of low- and high-methane-emitting beef cattle and sheep. Overall, this study highlights the importance of promoting alternative H2 consumption and reductant disposal pathways for synthesizing host-beneficial metabolites and reducing methane production in ruminants.

Researchers Develop Mexico’s First Comprehensive Greenhouse Gas Budget

A new study delves into 2 decades of data to create a comprehensive quantification of carbon, methane, and nitrous oxide sources and sinks that could help guide climate policy.

Synthetic methane for closing the carbon loop: Comparative study of three carbon sources for remote carbon-neutral fuel synthetization

Achieving carbon neutrality is probably one of the most important challenges of the 21st century for our societies. Part of the solution to this challenge is to leverage renewable energies. However, these energy sources are often located far away from places that need the energy, and their availability is intermittent, which makes them challenging to work with. In this paper, we build upon the concept of Remote Renewable Energy Hubs (RREHs), which are hubs located at remote places with abundant renewable energy sources whose purpose is to produce carbon-neutral synthetic fuels. More precisely, we model and study the Energy Supply Chain (ESC) that would be required to provide a constant source of carbon-neutral synthetic methane, also called e-NG (electric Natural Gas) or e-methane (electric methane), in Belgium from an RREH located in Morocco. To be carbon neutral, a synthetic fuel has to be produced from existing carbon dioxide (CO2) that needs to be captured using either Direct Air Capture (DAC) or Post Combustion Carbon Capture (PCCC). In this work, we detail the impact of three different carbon sourcing configurations on the price of the e-methane delivered in Belgium. Our results show that sourcing CO2 through a combination of DAC and PCCC is more cost-effective, resulting in a cost of 146 €/MWh for e-methane delivered in Belgium, as opposed to relying solely on DAC, which leads to a cost of 158 €/MWh. Moreover, these scenarios are compared to a scenario where CO2 is captured in Morocco from a CO2 emitting asset that allow to deliver e-methane for a cost of 136 €/MWh.

Analysis of low-carbon rice farming behavior and its influencing factors in farmers under the distributed cognition perspective—empirical study based on 2,173 farmers in Jiangxi Province

IntroductionRice production is the core component of the food security strategy in China, but it is also a major source of methane and nitrous oxide. Promoting low-carbon rice farming (LCRF) to increase the carbon sink, decrease carbon emissions, and achieve low-carbon, high-yield production is an inevitable “win-win” choice for achieving “double carbon” targets and guaranteeing national food security. This study contributes to the advancement of research on farmers’ adoption decisions and fills gaps in LCRF’s technical research on farmers’ decision-making behavior. The results also provide a basis for formulating policies to encourage LCRF and protect cultivated land.MethodsThis study conducted field research on 2,173 farming households in Jiangxi Province, a traditional agricultural province in China, and examined the effects of personal forces, local forces, and cultural forces on LCRF adoption behavior by introducing the distributed cognition theoretical framework based on a status quo analysis and employing the multivariate ordinal logistic model.Results and discussionThe results of the study showed that: 1) the overall acceptance of LCRF behavior is currently not very high. In the 2173 questionnaires, the mean number of LCRF behavior items accepted by farmers was 3.10 items; 153 farmers did not adopt any LCRF behavior, and only 77 farmers adopted all LCRF behaviors. Most farmers (n = 535) adopted three LCRF behaviors. 2) In distributed cognition affecting LCRF behavior, acceptance was primarily affected by cultural forces, followed by local forces, while the effects of personal forces were limited. Therefore, it is recommended that training and promotion should be increased, policy subsidies should be increased, the land market should be improved, and LCRF demonstrations should be carried out to increase the acceptance of LCRF behavior among rice farmers.

Ferrihydrite Addition Activated Geobacteraceae, the Most Abundant Iron-reducing Diazotrophs, and Suppressed Methanogenesis by Heterogeneous Methanogens in Xylan-amended Paddy Soil Microcosms.

Paddy fields are a major emission source of the greenhouse gas methane. In the present study, the addition of ferrihydrite to xylan-amended paddy soil microcosms suppressed methane emissions. PCR-based and metatranscriptomic ana-lyses revealed that the addition of ferrihydrite suppressed methanogenesis by heterogeneous methanogens and simultaneously activated Geobacteraceae, the most abundant iron-reducing diazotrophs. Geobacteraceae may preferentially metabolize xylan and/or xylan-derived carbon compounds that are utilized by methanogens. Geomonas terrae R111 utilized xylan as a growth substrate under liquid culture conditions. This may constitute a novel mechanism for the mitigation of methane emissions previously observed in ferric iron oxide-applied paddy field soils.

Biochar-composting substantially reduces methane and air pollutant emissions from dairy manure

Dairy manure is one of the largest sources of methane (CH4) emissions and air pollution from agriculture. In a previous study, we showed that composting dairy manure with biochar substantially reduces CH4 emissions and could help the dairy industry meet climate goals. However, it remained unclear whether biochar could also mitigate the emission of air pollutants and odor during composting. Here, we conducted a full-scale composting study at a dairy farm and monitored the emission of greenhouse gases (CO2, CH4, N2O) and air pollutants (H2S, VOCs, NO x , NH3) from compost piles amended with or without biochar. We found that amending compost with biochar significantly reduced total CH4 emissions by 58% (±22%) and cut H2S, VOCs, and NO x emissions by 67% (±24%), 61% (±19%) and 70% (±22%), respectively. We attribute this reduction in emissions to improved oxygen diffusion from the porous biochar and the adsorption of gas precursors to the biochar surface. Interestingly, NO x fluxes from the composting dairy manure were much higher than the few values reported in the literature, suggesting that dairy manure could also be a significant source of NO x emissions. We estimate that biochar-composting of dairy manure would reduce the social cost of manure emissions from this farm by over $66 000 annually. Results from this study suggest that composting dairy manure with biochar, in addition to reducing CH4 emissions, may help to improve air quality and the health and wellbeing of rural communities, but further studies are needed to test the quantitative impacts.

Meeting the moment: Reducing methane emissions and the need for better diagnostics

Methane has over 80 times the greenhouse gas warming potential of carbon dioxide in the short term (i.e., 20-year timeframe). As a consequence, reducing methane emissions can have significant and rapid impact towards reducing climate change. Several categories of anthropogenic sources contribute to methane emissions including the oil and gas industry, coal and other extractive mining, agricultural production, and landfills. Recent atmospheric mapping efforts are identifying and quantifying sources of methane – highlighting the need for improved technologies and processes to reduce methane emissions, and national policies are incentivizing mitigating methane emissions. The urgent and timely need to address the challenge of methane emissions motivates the development of improved diagnostics for laboratory and field applications. This paper describes the context of methane emissions (e.g., sources, concentrations and key transients) with an emphasis on flares and the opportunity for next-generation diagnostics to address the challenges and global need for accurate methane measurements in diverse applications. In particular, trends in prior field-scale flare measurements are presented including effects of cross-wind and heating value on flare combustion efficiency and hydrocarbon removal efficiency. Prior results show the effectiveness of flares at many operating conditions, and conditions where flare performance can be improved. The challenges and need to improve and expand flare emissions measurements are particularly highlighted.

Microbial mediation of cryptic methane cycle in semiclosed marine water column

<p>The continuous expansion of oxygen minimum zones (OMZs) has promoted methane emissions, and the origin and fate of methane in semi enclosed OMZs are poorly understood. In this study, we sampled 21 water layers across a 300-m depth of the Yongle blue hole (YBH) located in the South China Sea for metagenomics and metatranscriptomics work, coupled with data from global anoxic/suboxic water columns. The 16S rDNA reads in the metagenomes indicate high percentages of unclassified prokaryotes (on average 38%) and high microbiome novelty scores in anoxic layers of YBH, which are significantly higher than other semiclosed oxygen minimum zones. Analyses of 318 draft genomes and functional genes indicate that the methane source of YBH probably resulted from microbial cleavage of methylphosphonate (MPn) and dimethylsulfoniopropionate (DMSP). Methane oxidation that prevents methane emission from YBH was probably conducted by a new group of anaerobic methanotrophic Planctomycetota, Bacteroidota, and Verrucomicrobiota in suboxic and anoxic environments of YBH, in addition to Methylococcales in oxic layers. The Bacteroidota solely contribute to ~77% of methane decline from the peak at 180 m depth. Our research casts light on the cryptic methane cycle mediated by the novel microbiome that controls the release of greenhouse gases from marine geographic depressions exemplified by YBH, offering valuable insights into mitigating climate change effects in marine environments.</p>