Elevated Methane Emissions Research Articles

Mutation of rice SM1 enhances solid leaf midrib formation and increases methane emissions.

The leaf midrib system is essential for plant growth and development, facilitating nutrient transport, providing structural support, enabling gas exchange, and enhancing resilience to environmental stresses. However, the molecular mechanism regulating leaf midrib development is still unclear.In this study, we reported a rice solid midrib 1 (sm1) mutant, exhibiting solid leaf aerenchyma and abaxial rolling leaves due to abnormal development of parenchyma and bulliform cells. Map-based cloning revealed that SM1 encodes a litter zipper protein (ZPR). SM1 was mainly expressed in the sheaths and basal midrib and was associated with the nucleus. Further experiments indicated that SM1 can interact with OSHB1, preventing the formation of OSHB:OSHB dimers and subsequently repressing the expression of OSH1 involved in the regulation and maintenance of apical stem meristem formation. The sm1 mutant reduced long-distance oxygen transport ability from shoot to root. The impaired oxygen transport in the sm1 mutant may have contributed to the increase in methanogens and elevated methane emissions. Collectively, our findings revealed that the SM1-OSHB1-OSH1 modules regulate leaf aerenchyma development in rice. These modules not only enhance our understanding of the molecular mechanism of rice leaf aerenchyma development but also offer insights for reducing methane emissions through genetic modification.

Mitigating the Invasive Method of Hydraulic Fracturing Through a Phase Out Policy Plan

Hydraulic fracturing, or fracking, is a process used to extract natural gas from shale deposits deep below the surface. Fracking is heralded as a “clean” energy source compared to other extraction methods due to comparatively low carbon emissions. The fracking industry decreases the U.S.’s dependence on foreign nations for energy and brings valuable job opportunities when sites are first established; however, affected communities do not experience the benefits of these economic “booms” for long. Concerns like increased cancer risk from air and water contamination are linked to fracking activity. Fracking operators are not required to disclose the contents of ‘proprietary’ fracking fluids used in extraction, which are known to contain chemicals that threaten public and environmental health. Fracking has detrimental effects on national public health and contributes to climate change through elevated methane emissions. Therefore, to help mitigate these challenges, we recommend a phase out plan including 1) increasing setback requirements and eliminating any exemptions, 2) managing methane (CH₄) leakages and improving monitoring systems on all sites, 3) mandating disclosure reports, and 4) mandating the collection of preliminary data to facilitate a bottom-up approach to management. We use Pennsylvania as a case study due to the state’s prevalence of fracking and the current policies and regulations in place for drilling.

Full-Size Experimental Measurement of Combustion and Destruction Efficiency in Upstream Flares and the Implications for Control of Methane Emissions from Oil and Gas Production

Accurately measuring the combustion and destruction removal efficiency of flaring is important when accounting for methane emissions from oil and gas production. Despite this, the amount of experimental data from full-size flares is limited, especially for flares built without air or steam assistance. The use of a single destruction value of 98% is commonly applied. In this paper, we present new empirical measurements of flare efficiency using three common flare designs employed in upstream applications. Combustion products were analyzed using an extractive sampling method. The results demonstrate that whilst destruction efficiencies in excess of 98% are achievable, if the gas composition falls below a critical heating value of ~300 BTU/scf, the efficiency deteriorates leading to elevated methane emissions. This is further complicated by accurately measuring the flow of combustible gas and the impact of crosswinds. In an operational setting, continuous tracking of flare conditions is therefore a key resource in reducing methane emissions but further work is required to standardize how continuous performance tracking is evaluated if such measurements are to attain full traceability.

Decomposition of lignin and carbohydrates in a rewetted peatland: a comparative analysis of surface water and anaerobic soil layers

The rewetting of long-term drained peatlands leads to the development of eutrophic shallow lakes, gradually inhabited by reed communities. These shallow lakes are characterized by significant nutrient and methane emissions. To comprehend the fate of organic compounds from decaying Phragmites australis litter in water and anaerobic soil layers, we conducted a 1.6-year decomposition experiment. The experiment employed bulk and lignin-derived phenol analysis, as well as Fourier-transform infrared spectroscopy. As anticipated, the highest level of decomposition was observed in the surface water body of the shallow lake, while the non-rooted degraded peat exhibited the lowest decay. The bulk mass loss of plant litter decreased with depth from 55 to 27% across the four decomposition environments. Analysis using infrared spectroscopy indicated that the decrease in mass loss was primarily driven by the breakdown of carbohydrates, which constitute a significant portion of plant litter. Interestingly, litter in the rooted degraded peat layer exhibited the highest degree of lignin decay. Furthermore, the study revealed a preferential loss of vanillin phenols and an accumulation of p-hydroxyl phenols. These findings suggest that the increased methane emissions in rewetted fens may be partially attributed to the demethoxylation of vanillin phenols and the subsequent formation of p-hydroxyl phenols. In conclusion, this study provides valuable insights into anaerobic lignin decomposition of plant litter and sheds light on potential mechanisms underlying elevated methane emissions in rewetted peatlands. Furthermore, the study’s findings hold significant implications for both carbon cycling and sequestration within these ecosystems, thereby stimulating further research into the microbial community and its extended effects.

Strategies to Mitigate Enteric Methane Emissions from Ruminant Animals.

Human activities account for approximately two-thirds of global methane emissions, wherein the livestock sector is the single massive methane emitter. Methane is a potent greenhouse gas of over 21 times the warming effect of carbon dioxide. In the rumen, methanogens produce methane as a by-product of anaerobic fermentation. Methane released from ruminants is considered as a loss of feed energy that could otherwise be used for productivity. Economic progress and growing population will inflate meat and milk product demands, causing elevated methane emissions from this sector. In this review, diverse approaches from feed manipulation to the supplementation of organic and inorganic feed additives and direct-fed microbial in mitigating enteric methane emissions from ruminant livestock are summarized. These approaches directly or indirectly alter the rumen microbial structure thereby reducing rumen methanogenesis. Though many inorganic feed additives have remarkably reduced methane emissions from ruminants, their usage as feed additives remains unappealing because of health and safety concerns. Hence, feed additives sourced from biological materials such as direct-fed microbials have emerged as a promising technique in mitigating enteric methane emissions.

Microbial drivers of methane emissions from unrestored industrial salt ponds

Wetlands are important carbon (C) sinks, yet many have been destroyed and converted to other uses over the past few centuries, including industrial salt making. A renewed focus on wetland ecosystem services (e.g., flood control, and habitat) has resulted in numerous restoration efforts whose effect on microbial communities is largely unexplored. We investigated the impact of restoration on microbial community composition, metabolic functional potential, and methane flux by analyzing sediment cores from two unrestored former industrial salt ponds, a restored former industrial salt pond, and a reference wetland. We observed elevated methane emissions from unrestored salt ponds compared to the restored and reference wetlands, which was positively correlated with salinity and sulfate across all samples. 16S rRNA gene amplicon and shotgun metagenomic data revealed that the restored salt pond harbored communities more phylogenetically and functionally similar to the reference wetland than to unrestored ponds. Archaeal methanogenesis genes were positively correlated with methane flux, as were genes encoding enzymes for bacterial methylphosphonate degradation, suggesting methane is generated both from bacterial methylphosphonate degradation and archaeal methanogenesis in these sites. These observations demonstrate that restoration effectively converted industrial salt pond microbial communities back to compositions more similar to reference wetlands and lowered salinities, sulfate concentrations, and methane emissions.

Infectious Diseases, Livestock, and Climate: A Vicious Cycle?

Ruminant livestock are a significant contributor to global methane emissions. Infectious diseases have the potential to exacerbate these contributions by elevating methane outputs associated with animal production. With the increasing spread of many infectious diseases, the emergence of a vicious climate–livestock–disease cycle is a looming threat.

Comprehensive emission characterisation of exhaust from alternative fuelled cars

Abstract Exhaust emissions from Euro 2-6a cars using diesel, gasoline, high concentration ethanol (E85) fuel and compressed natural gas (CNG) were studied comprehensively, with a focus on results obtained at −7 °C test temperature. Higher emissions than desired were noticed in some cases, e.g. elevated methane emissions from natural gas fuelled cars, as well as methane and acetaldehyde emissions from E85 fuelled flexible fuel vehicles. Additionally, mutagenicity of PM samples and oxidative potential of semivolatile samples were observed. However, emission performance improved significantly when moving from older to newer Euro 6a cars, showing that low tailpipe exhaust emissions can be achieved when combining new car technology with CNG, E85, gasoline and diesel fuels. Furthermore, the climate impact of these technologies could reduce by using renewable counterparts of these fuels.

Predominance of methanogens over methanotrophs in rewetted fens characterized by high methane emissions

Abstract. The rewetting of drained peatlands alters peat geochemistry and often leads to sustained elevated methane emission. Although this methane is produced entirely by microbial activity, the distribution and abundance of methane-cycling microbes in rewetted peatlands, especially in fens, is rarely described. In this study, we compare the community composition and abundance of methane-cycling microbes in relation to peat porewater geochemistry in two rewetted fens in northeastern Germany, a coastal brackish fen and a freshwater riparian fen, with known high methane fluxes. We utilized 16S rRNA high-throughput sequencing and quantitative polymerase chain reaction (qPCR) on 16S rRNA, mcrA, and pmoA genes to determine microbial community composition and the abundance of total bacteria, methanogens, and methanotrophs. Electrical conductivity (EC) was more than 3 times higher in the coastal fen than in the riparian fen, averaging 5.3 and 1.5 mS cm−1, respectively. Porewater concentrations of terminal electron acceptors (TEAs) varied within and among the fens. This was also reflected in similarly high intra- and inter-site variations of microbial community composition. Despite these differences in environmental conditions and electron acceptor availability, we found a low abundance of methanotrophs and a high abundance of methanogens, represented in particular by Methanosaetaceae, in both fens. This suggests that rapid (re)establishment of methanogens and slow (re)establishment of methanotrophs contributes to prolonged increased methane emissions following rewetting.

Confirmation of Elevated Methane Emissions in Utah's Uintah Basin With Ground‐Based Observations and a High‐Resolution Transport Model

AbstractLarge CH4 leak rates have been observed in the Uintah Basin of eastern Utah, an area with over 10,000 active and producing natural gas and oil wells. In this paper, we model CH4 concentrations at four sites in the Uintah Basin and compare the simulated results to in situ observations at these sites during two spring time periods in 2015 and 2016. These sites include a baseline location (Fruitland), two sites near oil wells (Roosevelt and Castlepeak), and a site near natural gas wells (Horsepool). To interpret these measurements and relate observed CH4 variations to emissions, we carried out atmospheric simulations using the Stochastic Time‐Inverted Lagrangian Transport model driven by meteorological fields simulated by the Weather Research and Forecasting and High Resolution Rapid Refresh models. These simulations were combined with two different emission inventories: (1) aircraft‐derived basin‐wide emissions allocated spatially using oil and gas well locations, from the National Oceanic and Atmospheric Administration (NOAA), and (2) a bottom‐up inventory for the entire U.S., from the Environmental Protection Agency (EPA). At both Horsepool and Castlepeak, the diurnal cycle of modeled CH4 concentrations was captured using NOAA emission estimates but was underestimated using the EPA inventory. These findings corroborate emission estimates from the NOAA inventory, based on daytime mass balance estimates, and provide additional support for a suggested leak rate from the Uintah Basin that is higher than most other regions with natural gas and oil development.

The long-term fate of permafrost peatlands under rapid climate warming.

Permafrost peatlands contain globally important amounts of soil organic carbon, owing to cold conditions which suppress anaerobic decomposition. However, climate warming and permafrost thaw threaten the stability of this carbon store. The ultimate fate of permafrost peatlands and their carbon stores is unclear because of complex feedbacks between peat accumulation, hydrology and vegetation. Field monitoring campaigns only span the last few decades and therefore provide an incomplete picture of permafrost peatland response to recent rapid warming. Here we use a high-resolution palaeoecological approach to understand the longer-term response of peatlands in contrasting states of permafrost degradation to recent rapid warming. At all sites we identify a drying trend until the late-twentieth century; however, two sites subsequently experienced a rapid shift to wetter conditions as permafrost thawed in response to climatic warming, culminating in collapse of the peat domes. Commonalities between study sites lead us to propose a five-phase model for permafrost peatland response to climatic warming. This model suggests a shared ecohydrological trajectory towards a common end point: inundated Arctic fen. Although carbon accumulation is rapid in such sites, saturated soil conditions are likely to cause elevated methane emissions that have implications for climate-feedback mechanisms.

THE CURRENT DYNAMICS OF THE SUBMARINE PERMAFROST AND METHANE EMISSION ON THE SHELF OF THE EASTERN ARCTIC SEAS

We study the methane emission over the East Siberian Arctic Shelf (ESAS) under the changing sub-aquatic permafrost conditions from the time of inundation 9–6 thousand years BP to present and further until the end of the millennium. The study is based on the full-physics model of hydrothermal regime of soil. Our results indicate that the current elevated methane emission from ESAS is responsible for 0.01 oС global air temperature rise. Even under the hypothetic climate scenario that overestimates the range of near-bottom water temperature rise, projected by the end of the millennium thawing of the bottom sediments is likely to be about90 mand will thus not reach the upper limit of the methane hydrate stability zone that is located 100–140 munderneath the sea bottom. The results of the study do not support the so called «methane bomb» hypothesis that is widely discussed in the scientific literature and in the media.

Assessment of an integrated peat-harvesting and reclamation method: peatland-atmosphere carbon fluxes and vegetation recovery

We document a two-year experimental trial of a recently-developed integrated peat-harvesting and reclamation technique at a poor fen in northern Ontario, Canada. We removed and conserved the uppermost ~0.3 m of peat in blocks while deeper peat was harvested from the resultant pit. We allowed the extraction pit to flood with shallow groundwater, and then reclaimed the conserved surficial peat blocks by transplanting them into the flooded pit where they formed a low, floating mat. In the 2nd year after harvest average Sphagnum cover in our experimental plot was intermediate (~25 %) between hummocks (~100 %) and hollows (~10 %) at an adjacent unharvested reference plot. Mean rates of Sphagnum productivity were greater in the experimental plot (65–86 g m−2 month−1) than in the reference plot (45–55 g m−2 month−1) for both hummock (S. fuscum) and lawn (S. magellanicum) species, although not significantly so, indicating that the transplant had no adverse effects on Sphagnum health. The inundated soil conditions in the trial pit prevented the large carbon dioxide emissions that are characteristic of many harvested peatlands. During the second growing season midday net ecosystem exchange at the experimental plot was similar to that at hollows in the reference plot. However, the anoxic soil conditions in the experimental plot led to highly elevated methane emissions in both years. Our results demonstrate that the method can enable rapid re-establishment of a healthy Sphagnum mat and carbon dioxide sequestration function in harvested peatlands, although the global warming potential of our experimental trial was high due to elevated methane emissions.

Elevated methane emissions from a paddy field in southeast China occur after applying anaerobic digestion slurry

AbstractOne hundred million tons of farm stalk waste and livestock and poultry excrement are used every year in China for the production of clean energy (biogas) by anaerobic digestion. Consequently, a large amount of fermented liquid is produced, and if disposed of improperly, it will result in secondary pollution. Agricultural application of this anaerobic slurry as a liquid fertilizer would reduce possible eutrophication of water sources from random slurry discharge and supply a superior organic fertilizer for farming. This study investigated the effect of applying anaerobic digestion slurry as a liquid fertilizer on the methane emitted from a paddy field. A two‐year (2008–2009) field experiment replacing chemical fertilizer with liquid fertilizer from anaerobically digested pig manure slurry was conducted in a paddy field in Yixing, Jiangsu, China. A static closed chamber method was used to measure methane fluxes over the period from June 2008 to October 2009. All fertilizer treatments increased methane emissions relative to untreated controls, with increases in methane ranging from 40–70% in 2008 to 48–84% in 2009. Paddy fields treated with anaerobically digested pig manure slurry had greater methane emissions (8–84% in 2008 and 3–26% in 2009) than those treated with chemical fertilizer. This suggests that the anaerobic digestion slurry would increase methane emission and so is unsuitable as a liquid fertilizer in paddy fields without development of cultivation practices to limit these emissions.

Global agriculture needs smart science and policies

Food insecurity and climate change, the twin crises that may define the future [1] have brought agriculture back into the spotlight of international debate. In spite of the growing threats of climate change to agricultural yields and livelihoods, global agriculture must produce additional food to feed a growing population [2]. Today, more than ever before, we understand the significance that climate has for agriculture. Major weather and food price shocks are becoming the new norm – the recent droughts in the horn of Africa, Russia, Australia, and United States markedly affected food production and prices, and increased the vulnerability of the poor. Agriculture’s direct reliance on the natural resource base is a defining characteristic of the sector, consuming 70% of global freshwater and occupying 40% of global land area. Conventional forms of agricultural production are often unsustainable, pollute the environment and deplete the natural resources on which production relies over time. Low agricultural productivity is often associated with poverty, food insecurity, and nutrient depletion in Africa, where just 4% of smallholder farmers use improved seeds, the average fertilizer application is 9 kg per hectare, and only 1% of arable land is under irrigation. In Asia, inappropriate irrigation practices lead to elevated methane emissions and salinization, and high nitrogen fertilizer levels to greenhouse gas emissions. Agriculture is the world’s leading source of methane and nitrous oxide emissions, a substantial source of carbon emissions, and the principal driver behind deforestation worldwide. Some 30% of global greenhouse gas emissions are attributable to agriculture and deforestation. The growing consensus on the need for a climate-smart agriculture (CSA) emerged largely out of awareness of the sector’s negative impacts. More recently, this perspective of agriculture as a source of greenhouse gas emissions and environmental pollution has become more balanced, with a growing understanding of the environmental services the sector can provide if production is well-managed. CSA

Effects of low temperature on the cold start gaseous emissions from light duty vehicles fuelled by ethanol-blended gasoline

According to directives 2003/30/EC and 2009/28/EC of the European Parliament and the Council, Member States should promote the use of biofuel. Consequently, since 2011 all fuels on the market used for transport purpose must contain a fraction of 5.75% renewable energy sources. Ethanol in gasoline is a promising solution to reach this objective. In addition to decrease the dependence on fossil fuel, ethanol contributes to reducing air pollutant emissions during combustion (carbon monoxide and total hydrocarbons), and has a positive effect on greenhouse gas emissions. These considerations rely on numerous emission studies performed in standard conditions (20–30°C), however, very few emission data are available for cold ambient temperatures, as they prevail in winter times in e.g., Northern Europe. This paper presents a chassis dynamometer study examining the effect of ethanol (E75–E85) versus gasoline (E5) at standard and low ambient temperatures (22°C and −7°C, respectively). Emissions of modern passenger cars complying with the latest European standards (Euro4 and Euro5a) were recorded over the New European Driving Cycle (NEDC) and the Common Artemis Driving Cycle (CADC). Unregulated compounds such as methane, ammonia, and small chain hydrocarbons were monitored by an online Fourier Transformed Infra-Red spectrometer. In addition, a number of ozone precursors (carbonyls and volatile organic hydrocarbons) were collected and analyzed offline by liquid and gas chromatography in order to evaluate the ozone formation potential (OFP) of the exhaust. Results showed higher unregulated emissions at −7°C than at 22°C, regardless of the ethanol content in the fuel blend. More carbonyls were associated with oxygenated fuel, and acetaldehyde emissions were found particularly enhanced at −7°C with E75. In addition, elevated methane emission was measured at low ambient temperature when ethanol fuel was used. Moreover, the OFP of the exhaust gas at −7°C increased with the amount of ethanol in gasoline when the cold start excess emissions were included. However, regardless of the ambient temperature, the ammonia and toluene emissions associated to E75–E85 were lower than with E5.

Methane emissions from tropical freshwater wetlands located in different climatic zones of Costa Rica

Wetlands are the largest natural source of the greenhouse gas methane to the atmosphere. Despite the fact that a large percentage of wetlands occur in tropical latitudes, methane emissions from natural tropical wetlands have not been extensively studied. The objective this research was to compare methane emissions from three natural tropical wetlands located in different climatic and ecological areas of Costa Rica. Each wetland was within a distinct ecosystem: (1) a humid flow-through wetland slough with high mean annual temperatures (25.9 °C) and precipitation (3700 mm yr⁻¹); (2) a stagnant rainforest wetland with high mean annual temperatures (24.9 °C) and precipitation (4400 mm yr⁻¹); or (3) a seasonally wet riverine wetland with very high mean annual temperatures (28.2 °C) and lower mean annual precipitation (1800 mm yr⁻¹). Methane emission rates were measured from sequential gas samples using nonsteady state plastic chambers during six sampling periods over a 29-month period from 2006 to 2009. Methane emissions were higher than most rates previously reported for tropical wetlands with means (medians) of 91 (52), 601 (79), and 719 (257) mg CH₄-C m⁻² day⁻¹ for the three sites, with highest rates seen at the seasonally flooded wetland site. Methane emissions were statistically higher at the seasonally wet site than at the humid sites (P<0.001). Highest methane emissions occurred when surface water levels were between 30 and 50 cm. The interaction of soil temperature, water depth, and seasonal flooding most likely affected methanogenesis in these tropical sites. We estimate that Costa Rican wetlands produce about 0.80 Tg yr⁻¹ of methane, or approximately 0.6% of global tropical wetland emissions. Elevated methane emissions at the seasonally wet/warmer wetland site suggest that some current humid tropical freshwater wetlands of Central America could emit more methane if temperatures increase and precipitation becomes more seasonal with climate change.

Seabed methane emissions and the habitat of frenulate tubeworms on the Captain Arutyunov mud volcano (Gulf of Cadiz)

Submarine mud volcanism represents an important pathway for methane from deeper reservoirs to the surface, where it enters the benthic carbon cycle. To quantify overall methane release from the Captain Arutyunov mud volcano (CAMV) and to assess the contribution of mac- robenthic seep organisms to the regulation of the benthic methane flux, we linked water column methane concentrations, seabed methane emission and pore water geochemistry to the spatial distri- bution of seep biota. Prominent organisms of the CAMV seep biota were 3 different species of frenu- late tubeworms. Seabed methane emission ranged from 0.001 to 0.66 mmol m -2 d -1 . Dense patches of tubeworms were associated with the lowest seabed methane emission. Elevated methane emission was associated with a sporadic distribution of tubeworms and the occurrence of numerous mud clasts. Despite the presence of a large subsurface methane reservoir, the estimated total methane release from CAMV was low (0.006 × 10 6 mol yr -1 ). In addition to direct methane consumption by Siboglinum poseidoni, the tubeworms likely contribute to the retention of methane carbon in the sed- iment by affecting bacterial communities in the proximity of the tubes. The siboglinids create new meso-scale habitats on the sediment surface, increasing habitat heterogeneity and introducing niches for bacterial communities.