Methane Emissions Research Articles

Characterization and mitigation measures for carbon dioxide, methane, and ammonia emissions in dairy barns

The agricultural sector is a major contributor to global greenhouse gas emissions, with dairy production being a significant source. In this context, the study aims to characterize CO₂, CH₄, and NH₃ emissions—key greenhouse gases in dairy barns—and to evaluate strategies for mitigating these emissions. Inside dairy barns, the primary sources of CO₂, CH₄, and NH₃ emissions are linked to the enteric processes of the animals and the waste deposited within the dairy barns. CO₂ mainly originates from animal respiration and the decomposition of organic matter. CH₄ is generated through enteric fermentation in the rumen and the anaerobic decomposition of manure. Additionally, NH₃ is released from the enzymatic breakdown of urea in urine. Mitigation efforts have shown promise within dairy barns through various approaches. Optimizing animal diets by incorporating supplements and controlling protein intake helps reduce methane production from enteric fermentation. Enhanced manure management practices, including separating feces and urine, adjusting manure pH, and increasing cleaning frequency, are effective in minimizing ammonia and methane emissions within dairy barns. Nevertheless, achieving significant emission reductions also requires effective waste management beyond the facilities. This study contributes to the ongoing dialogue on sustainable livestock production by addressing both emission sources and potential solutions in dairy farming.

Methane emissions at pressure-regulating stations in China: A comparative analysis of various quantitative methods.

As a key component of the distribution system, metering and pressure-regulating (M&R) stations provide an opportunity for effective mitigation of methane emissions. Given that these stations are readily accessible, above-ground facilities, routine methane emission monitoring can identify issues and with repair or upgrades this can lead to reduced methane emissions. This practice has become an important measure for addressing climate change. China aims to actively promote the monitoring, evaluation, and inventory improvement of distribution systems. In this study, methane detection and analysis were conducted at 11 pressure regulation-metering stations operated by a company in North China and Central China. Methane emissions were estimated using the dynamic flux chamber method, the inverse Gaussian plume modeling method (OTM33A), and the stochastic Lagrangian (LS) inverse modeling method. The results of the dynamic flux chamber method indicate that flanges, instrumentation and meters, and connectors are the primary sources of methane emissions at pressure-regulating stations, with emission factors of 0.0034kg/h (CI: 0.0030-0.0038kg/h), 0.0022kg/h (CI: 0.0018-0.0025kg/h), and 7.1e-04 (CI: 6.3e-04-8.0e-04) kg/h, respectively. The correlation between detected concentration and emission rate was weak. The cumulative fluxes calculated by the three methods were 0.109kg/h (CI: 0.094-0.125kg/h), 0.143kg/h (CI: 0.015-0.337kg/h), and 0.125kg/h (CI: 0.035-0.218kg/h). The results of controlled tests and field measurements suggest that the LS method offers a more reliable and physically accurate analysis of methane fluxes for pressure regulating-metering stations with limited measurement distances (typically less than 30m) and small continuous emissions. The emission factor for the pressure-regulating stations in this study is 0.013kg/h (CI: 0.008-0.023kg/h) using the bootstrap Monte Carlo method. This research provides guidance for operators to implement fixed monitoring, which is crucial for building emission inventories and ensuring production safety.

Unveiling the dynamic flows and spatial inequalities arising from agricultural methane and nitrous oxide emissions

Tracing the spatial transfer and heterogeneity of agricultural methane (CH4) and nitrous oxide (N2O) emissions in China is a prerequisite for the sustainable transformation of agricultural systems. In this study, we established a research framework for evaluating agricultural CH4 and N2O flows and convergence. Using this framework, we established an inventory of China's agricultural CH4 and N2O emissions calculated according to the IPCC inventory guidelines, built a food trade model to simulate the spatial transfer, and revealed the regional differences. Finally, we analyzed the influence mechanism by combining extended Kaya identity and the logarithmic mean divisia index (LMDI) model. We found that inter-regional transfer of agricultural CH4 and N2O emissions in China have intensified, increasing from 56.14 % of total transfers in 2000 to 67.28 % in 2019. The spatial inequalities of agricultural CH4 and N2O increased, and emission intensity varied more within regions than between regions, with per capita emissions showing a club convergence with “intragroup convergence and intergroup divergence”. Although the contribution of agricultural CH4 and N2O emissions varies across provinces, controlling emissions intensity and land use intensity while maintaining GDP per capita is the key to emission mitigation. Our study provides theoretical support for prioritizing policies to mitigate agricultural CH4 and N2O emissions.

Effects of polyphenol-rich extracts and compounds on methane and ammonia emissions from pig slurry during 28-day incubation

Animal manure in livestock production facilities is a major source of methane (CH4) and ammonia (NH3) emissions from agriculture. In this study, we investigated different polyphenol-rich extracts and chemicals including commercial chestnut tannin (CT), shea meal extract (SME) and lignosulfonic acid (LSA) in combination with 1 mM of urease inhibitors acetohydroxamic acid (AHA) and/or sodium fluoride (NaF) to mitigate CH4 and NH3 in an in-vitro setup with 0.5 L slurry reactors mimicking slurry pits in livestock facilities. Daily addition of pig feces and urine along with additives were conducted for 28 days at room temperature, while CH4 and NH3 emissions were monitored by cavity ring-down spectroscopy (CRDS) continuously. SME and SME+NaF added to slurry reduced CH4 emission by 72% and 88%, and NH3 emission by 45% and 52%, respectively. CT+NaF at the CT concentration of 2.6, 4.25 and 8.5 mg mL-1, resulted in 48-55%, 70-72% and 81% reduction in CH4 emission, and 17-29%, 40-49% and 49% reduction in NH3 emission, respectively. Emission reduction based on the dosage of CT revealed that the relationship between dosage and emission reduction is not linear, therefore the reduction efficiency was calculated by emission reduction divided by concentration. CH4 reduction efficiency at the CT concentration of 2.6, 4.25 and 8.5 mg mL-1 were 18-21, 16-17 and 10 % (mg mL-1)-1. Therefore, the optimum dosage of CT was 4.25 mg mL-1. In conclusion, addition of CT and SME along with NaF resulted in significant reductions of both CH4 and NH3 emissions, while supplementation of LSA and AHA to CT+NaF did not enhance the mitigation effect.

Controls on spatial variation in porewater methane concentrations across United States tidal wetlands

Tidal wetlands can be a substantial sink of greenhouse gases, which can be offset by variable methane (CH4) emissions under certain environmental conditions and anthropogenic interventions. Land managers and policymakers need maps of tidal wetland CH4 properties to make restoration decisions and inventory greenhouse gases. However, there is a mismatch in spatial scale between point-based sampling of porewater CH4 concentration and its predictors, and the coarser resolution mapping products used to upscale these data. We sampled porewater CH4 concentrations, salinity, sulfate (SO42−), ammonium (NH4+), and total Fe using a spatially stratified sampling at 27 tidal wetlands in the United States. We measured porewater CH4 concentrations across four orders of magnitude (0.05 to 852.9 μM). The relative contribution of spatial scale to variance in CH4 was highest between- and within-sites. Porewater CH4 concentration was best explained by SO42− concentration with segmented linear regression (p < 0.01, R2 = 0.54) indicating lesser sensitivity of CH4 to SO42− below 0.62 mM SO42−. Salinity was a significant proxy for CH4 concentration, because it was highly correlated with SO42− (p < 0.01, R2 = 0.909). However, salinity was less predictive of CH4 with segmented linear regression (p < 0.01, R2 = 0.319) relative to SO42−. Neither NH4+, total Fe, nor relative tidal elevation correlated significantly with porewater CH4; however, NH4+ was positively and significantly correlated with SO42− after detrending CH4 for its relationship with SO42− (p < 0.01, R2 = 0.194). Future sampling should focus on within- and between-site environmental gradients to accurately map CH4 variation. Mapping salinity at sub-watershed scales has some potential for mapping SO42−, and by proxy, constraining spatial variation in porewater CH4 concentrations. Additional work is needed to explain site-level deviations from the salinity-sulfate relationship and elucidate other predictors of methanogenesis. This work demonstrates a unique approach to remote team science and the potential to strengthen collaborative research networks.

Adsorption of Methane–Nitrogen mixtures with flexible Zeolitic Imidazolate Framework-7 (ZIF-7)

ZIF–7 is a pressure–regulated flexible metal–organic framework with a notably lower admission pressure for CH4 relative to N2, making it highly-prospective for curbing fugitive emissions of methane. Here, the separation of CH4 from N2 by an improved variant of ZIF–7 was studied over a range of pressures, temperatures, and compositions using multiple complementary techniques. Pure gas adsorption isotherms measured from (283 to 323) K at up to 16 MPa reveal this variant of ZIF-7 exhibits 50–60 % higher adsorption capacities for both CH4 and N2 in the large–pore phase than previous ZIF–7 samples. Binary mixture adsorption isotherms from dynamic column breakthrough experiments were consistent with those predicted from pure–gas isotherms using Ideal Adsorbed Solution Theory. Methane uptake increased significantly when the pore phase transition pressure for the mixture was reached, while the uptake of nitrogen remained small. Consequently, the equilibrium CH4-over–N2 selectivity of ZIF-7 is always larger than 5.5 and can increase to around 9, significantly above that of conventional adsorbents. Further characterisation showed the rate of the adsorption on ZIF–7 initially decreases as the pore phase transition begins before it increases significantly. Raman spectra acquired at various pressures along the adsorption isotherms revealed changes in certain vibrational modes associated with the structural change. Collectively, these observations indicate that the conceptually simple gating mechanism often used to describe the pore phase transitions in ZIF-7 in fact depends on interactions between the guest molecules and the adsorbent framework that continue to operate once the material is in the large–pore state.

Anaerobic oxidation of methane coupled to reductive immobilization of hexavalent chromium by “Candidatus Methanoperedens”

The anaerobic oxidation of methane (AOM) carried out by anaerobic methanotrophic archaea (ANME) plays an important role in mitigating methane emissions from aqueous environments and has applications in bioremediation and wastewater treatment. Previous studies showed that AOM could be coupled to chromate reduction. However, the specific responsible microorganisms and the biochemical mechanisms are unclear. Herein, we showed that a consortium dominated by ANME “Candidatus Methanoperedens” was able to couple AOM to the reduction of Cr(VI) to Cr(III) at a stoichiometry close to the theoretical ratio. Quantitative distribution analysis of Cr(III) products suggested Cr(VI) was predominantly reduced via the extracellular respiratory pathways. Further Cr(III)-targeted fluorescent visualization combined with single-cell electron microscopic imaging suggested that Cr(VI) was reduced by “Ca. Methanoperedens” independently. Biochemical mechanism investigation via proteomic analysis showed proteins for nitrate reduction under nitrate-reducing conditions were significantly downregulated in Cr(VI)-reducing incubation. Instead, many multiheme cytochrome c (MHCs) were among the most upregulated proteins during the Cr(VI) reduction process, suggesting MHC-governed pathways for extracellular Cr(VI) reduction. The significant upregulation of a formate-dependent nitrite reductase during Cr(VI) reduction indicated its potential contribution to the small proportion of Cr(VI) reduction inside cells.

Prediction of methane emission and electricity generation from landfills: Deep learning approach

Prediction of methane emission and electricity generation from landfills: Deep learning approach

Biofeed through bioconversion process with the engineered methyl-microbium buryatense strain 5GBC1-RO1

This study presents a novel approach to mitigate methane emissions while simultaneously addressing the growing demand for sustainable animal feed through the development of an engineered methanotrophic strain, Methylomicrobium buryatense 5GB1C-RO1. Utilizing advanced genetic engineering techniques, including CRISPR/Cas9 and horizontal gene transfer, we have optimized the ribulose monophosphate (RuMP) cycle and enhanced oxidase activity in this strain. The bioconversion process is facilitated by innovative bioreactor designs, including Two-Phase Partitioning Bioreactors (TPPBs) and Inverse Membrane Bioreactors (IMBRs), which significantly improve methane solubility and mass transfer. Through metabolic flux analysis and computational modeling, we have achieved high biomass yields and efficient methane utilization. The resulting biofeed demonstrates a superior nutritional profile, with optimized macronutrient content and essential components. This integrated approach not only contributes to greenhouse gas mitigation but also offers a promising solution for sustainable animal nutrition. Our findings suggest that the 5GB1C-RO1 strain and associated bioprocesses have the potential to revolutionize both environmental protection and agricultural sustainability.

The Assessment of the Ecological State of Leachate from the Largest landfill of Georgia and Its Impact on Climate Change

Over the past decade the municipal solid waste management status in Georgia remained at the stage of mixed waste collection and disposal in landfills having negative impacts on entire ecosystem. It results the formation of large amounts of leachate, methane gas, potential resource depletion and is potential to health hazards. Landfill leads to groundwater contamination, soil &amp; land pollution, harm to animals exposing to harmful materials &amp; foods. Landfills are vulnerable to accidental fires due to the methane produced by decomposing organic waste, financial costs that can be expensive for municipalities or city councils and taxpayers. The aim of this study is to assess the adversee impact of leachate management technology on water resources, as well as on climate change. For utilisation of leachate in this research, the technology of distributing the collected leachate over the surface of the landfill is used. The main objectives include, the study of physical-chemical and microbiological parameters of leachate and the calculation of GHG (methane) emissions from sedimentation systems/tanks/reservoirs of leachate. Physical-chemical and microbiological analysis of leachate water indicates that the concentrations of organic, biogenic and microbiological parameters in research samples exceed limits of discharge by ten times. In this study, for the first time an index of water pollution and greenhouse gas emissions was calculated for leachate of the biggest landfill in Georgia. Leachates belong to class VII according to water pollution index. Emission of methane from leachate for 2024-year estimated as 5% additionally to total methane emissions from the studied landfill.

Gallic and Ellagic Acids Differentially Affect Microbial Community Structures and Methane Emission When Using a Rumen Simulation Technique.

Dietary tannins can affect rumen microbiota and enteric fermentation to mitigate methane emissions, although such effects have not yet been fully elucidated. We tested two subunits of hydrolyzable tannins named gallic acid (GA) and ellagic acid (EA), alone (75 mg/g DM each) or combined (150 mg/g DM in total), using the Rusitec system. EA and EA+GA treatments decreased methane production, volatile fatty acids, nutrient degradation, relative abundance of Butyrivibrio fibrisolvens, Fibrobacter succinogenes, Ruminococcus flavefaciens but increased Selenomonas ruminantium. EA and EA+GA increased urolithins A and B. Also, EA and EA+GA reduced bacterial richness, with limited effects on archaeal richness. For bacteria, Megasphaera elsdenii was more abundant after EA and EA+GA, while Methanomethylophilaceae dominated archaea in all treatments. EA was more effective than GA in altering rumen microbiota and fermentation but GA did not reduce VFA and nutrient degradation. Thus, dietary supplementation of EA-plant extracts for ruminants may be considered to mitigate enteric methane, although a suitable dosage must be ensured to minimize the negative effects on fermentation.

Tidal influence on carbon dioxide and methane fluxes from tree stems and soils in mangrove forests

Abstract. Mangroves are critical blue carbon ecosystems. Measurements of methane (CH4) emissions from mangrove tree stems have the potential to reduce uncertainty in the capacity of carbon sequestration. This study is the first to simultaneously measure CH4 fluxes from both stems and soils throughout tidal cycles. We quantified carbon dioxide (CO2) and CH4 fluxes from mangrove tree stems of Avicennia marina and Kandelia obovata, which have distinct root structures, during tidal cycles. Tree stems of both species served as net CO2 and CH4 sources. Compared to fluxes in the soils, the mangrove tree stems exhibited remarkably lower CH4 fluxes but no difference in CO2 fluxes. The stems of A. marina exhibited an increasing trend in CO2 flux from low to high tides. However, CH4 fluxes showed high temporal variability, with the stems of A. marina functioning as a CH4 sink before tidal inundation and becoming a source after ebbing. In contrast, the stems of K. obovata showed no consistent pattern in the CO2 or CH4 fluxes. Based on our findings, the stem CH4 fluxes in A. marina may vary by up to 1200 % when considering tidal influence, compared to when tidal influence is ignored. Therefore, sampling only during low tides might underestimate stem CO2 and CH4 fluxes on a diurnal scale. This study highlights the necessity of considering tidal influence and species when quantifying greenhouse gas (GHG) fluxes from mangrove tree stems. Further study is needed to explore the underlying mechanisms driving the observed flux variations and improve the understanding of GHG dynamics in mangrove ecosystems.

Seasonal and altitudinal dynamics in secondary metabolite composition of Commelina forage species in Konso zone, southern Ethiopia.

Exploring the type and amounts of the secondary metabolites (SMs) in a given fodder species was considered as a meaningful act for safe and profitable utilization of that particular feedstuff in the livestock industry. This study was conducted in the Konso zone, southern Ethiopia, to explore the secondary metabolite composition of Commelina species in two seasons and at two different altitudes. Samples were collected from the two altitudes and seasons. A completely randomized design was used in a factorial arrangement (five species (C. benghalensis, C. imberbis, C. diffusa, C. albescens, and C. africana), two altitudes, and two seasons) with three repetitions per treatment. The SM contents of the Commelina species were reasonably influenced by both seasonal and altitudinal changes. The mean alkaloid (3.67%), total phenols (9.76 mg GAE/g), flavonoid (3.81 mg CE/g) and condensed tannin (1.10 mg CE/g) values for the herb species in wet season inclined (p < 0.001) to 7.02%, 14.07 mg GAE/g, 7.68 mg CE/g and 2.38 mg CE/g, respectively, in dry season. The wet season saponin concentration of the species (2.65 g/Kg) significantly decreased (p < 0.001) to 1.28 g/Kg in the dry season. Similarly, the lowland saponin (2.26 g/Kg), alkaloid (3.70%), total phenols (10.89 mg GAE/g), flavonoid (4.71 mg CE/g), and condensed tannin (0.98 mg CE/g) contents were increased (p < 0.01) to 3.03 g/Kg, 5.47%, 13.61 mg GAE/g, 6.37 mg CE/g, and 1.81 mg CE/g, respectively, in the midlands. Alkaloids, total phenols, flavonoids and condensed tannin concentrations showed positive correlations with each other (P<0.05) and with seasonal (P<0.001) and altitudinal changes (P<0.001) as well. The findings of this study suggested that the SM concentrations of Commelina species were within the limits tolerable for ruminants. In conclusion, Commelina species could serve as a safe and beneficial forage herb to boost nutrient intake, improve nutrient use efficiency and hinder methane emissions, for animals consuming them, in areas where they are available in abundance.

First Investigation of Long-Term Methane Emissions from Wastewater Treatment Using Satellite Remote Sensing

Wastewater treatment (WWT) contributes 2–9% of global greenhouse gas (GHG) emissions. The noticeable uncertainty in emissions estimation is due in large part to the lack of measurement data. Several methods have recently been developed for monitoring fugitive GHG emissions from WWT. However, limited by the short duration of the monitoring, only “snapshot” data can be obtained, necessitating extrapolation of the limited data for estimating annual emissions. Extrapolation introduces substantial errors, as it fails to account for the spatial and temporal variations of fugitive emissions. This research evaluated the feasibility of studying the long-term CH4 emissions from WWT by analyzing high spatial resolution Sentinel-2 data. Satellite images of a WWT plant in Calgary, Canada, taken between 2019 and 2023, were processed to retrieve CH4 column concentration distributions. Digital image processing techniques were developed and used for extracting the time- and space-varying features of CH4 emissions, which revealed daily, monthly, seasonal, and annual variations. Emission hotspots were also identified and corroborated with ground-based measurements. Despite limitations due to atmospheric scattering, cloud cover, and sensor resolution, which affect precise ground-level concentration assessments, the findings reveal the dynamic nature of fugitive GHG emissions from WWT, indicating the need for continuous monitoring. The results also show the potential of utilizing satellite images for cost-effectively evaluating fugitive CH4 emissions.

A novel irrigation system to reduce methane emissions in paddy fields

A novel irrigation system to reduce methane emissions in paddy fields

Probability of Detection and Multi-Sensor Persistence of Methane Emissions from Coincident Airborne and Satellite Observations.

Satellites are becoming a widely used measurement tool for methane detection and quantification. The landscape of satellite instruments with some methane point-source quantification capabilities is growing. Combining information across available sensor platforms could be pivotal for understanding trends and uncertainties in source-level emissions. However, to effectively combine information across sensors of varying performance levels, the probability of detection (POD) for all instruments must be well characterized, which is time-consuming and costly, especially for satellites. In August 2023, we timed methane-sensing aerial surveys from the Global Airborne Observatory (GAO) to overlap with observations from the NASA Earth Surface Mineral Dust Source Investigation (EMIT). We show how these coincident observations can be used to determine and verify the detection limits of EMIT and to develop and test a multisensor persistence framework. Under favorable conditions, the 90% POD at 3 for EMIT is 1060. We further derive a Bayesian model to infer probabilistically whether nondetected emissions were truly off, and we validate and show how this model can be used to assess the intermittency of emissions with GAO and EMIT. Time-averaged emission rates from persistent sources can be underestimated if POD is not characterized and if differences in POD across multisensor frameworks are not properly accounted for.

Effects of cashew nutshell extract inclusion into a high-grain finishing diet on methane emissions, nutrient digestibility, and ruminal fermentation in beef steers.

By 2050, the U.S. beef industry must produce an extra 40 million tons of beef to satisfy the global demand. Such an increase in inventory will undoubtedly enhance methane (CH4) production from livestock, which should be reduced by over 20%. The addition of plant secondary metabolites, such as anacardic acid present in cashew nutshell extract (CNSE), has shown promising results in reducing CH4 yield, although its effects seemed to be diet dependent. This study evaluated the addition of CNSE to a high-grain diet (85:15 Grain: forage) on in vivo CH4 emissions, nutrients digestibility, performance, feeding behavior, and ruminal fermentation parameters of beef steers. Sixteen Angus crossbred steers [599 ± 40kg of bodyweight (BW)] and six ruminally cannulated crossbred steers (490 ± 51kg of BW) were utilized in a crossover design with 2 experimental periods of 56 d each, composed by 14 d of adaptation, 35 d of measurement, and 7 d of washout. Following adaptation, steers were sorted by BW, and assigned to receive no additive (CON) or CNSE at 5g/steer/d. Data were analyzed using the MIXED procedure of SAS. Inclusion of CNSE increased (P < 0.05) propionate concentration and molar proportion (MP; mol/100mol), tended to decrease acetate MP (P = 0.10), reduced the acetate: propionate (A:P) ratio (P = 0.05), and MP of branched chain volatile fatty acids (P < 0.01). Neither in vitro organic matter digestibility nor in vitro CH4 yield were affected by CNSE inclusion (P > 0.05). Steers receiving CNSE exhibited greater (P < 0.05) final BW, dry matter intake (DMI), and average daily gain (ADG) but lesser (P < 0.05) in vivo CH4 emission rate (g/d), yield (g/kg of DMI), and intensity (g/kg of ADG). Meal length, bunk visit duration, and apparent total tract digestibility of DM increased (P < 0.05) after CNSE addition. Considering CNSE-supplemented steers spent more time in the feedbunk and exhibited higher DMI, CH4 mitigation was unlikely associated with intake reduction. The addition of CNSE to a high-grain diet in beef steers demonstrated significant improvements in animal performance and reduced CH4 emissions, as the result of shifts in ruminal fermentation patterns, favoring propionate instead acetate concentration, leading to a reduction in the A:P ratio. CNSE shows promise as a strategy to enhance beef industry sustainability.

Author Correction: Oxygen priming induced by elevated CO2 reduces carbon accumulation and methane emissions in coastal wetlands

Author Correction: Oxygen priming induced by elevated CO2 reduces carbon accumulation and methane emissions in coastal wetlands

Development of prechamber enabled mixing-controlled combustion strategy for ultra-low methane emissions from lean burn natural gas engines

Development of prechamber enabled mixing-controlled combustion strategy for ultra-low methane emissions from lean burn natural gas engines

The roles of phytogenic feed additives, trees, shrubs, and forages on mitigating ruminant methane emission

The roles of phytogenic feed additives, trees, shrubs, and forages on mitigating ruminant methane emission