Controlling Methane Emissions Research Articles

Bioelectrochemical approach for control of methane emission from wetlands

To harvest electricity and mitigate methane emissions from wetlands, a novel microbial fuel cell coupled constructed wetland (MFC-CW) was assembled with an anode placing in the rhizosphere and a cathode on the water surface. Plant-mediated methane accounted for 71–82% of the total methane fluxes. The bioanode served as an inexhaustible source of electron acceptors and resulted in reduced substantial methane emissions owing to electricigens outcompeting methanogens for carbon and electrons when substrate was deficient. However, when supplying sufficient organic carbon, both electricity and methane increased, indicating that electrogenesis and methanogenesis could co-exist in harmony. Direct methane emission (diffusion/ebullition) and plant-mediated methane emission were affected by operating conditions. Methanogenesis was significantly suppressed (∼98%) at HRT of 96h and with external resistance of 200Ω, accompanied with improved coulombic efficiency of 14.9% and current density of 187mA/m2. Contrarily, change of electrode polarity in the rhizosphere led to more methane efflux.

Anaerobic Methane Oxidation Driven by Microbial Reduction of Natural Organic Matter in a Tropical Wetland.

Wetlands constitute the main natural source of methane on Earth due to their high content of natural organic matter (NOM), but key drivers, such as electron acceptors, supporting methanotrophic activities in these habitats are poorly understood. We performed anoxic incubations using freshly collected sediment, along with water samples harvested from a tropical wetland, amended with 13C-methane (0.67 atm) to test the capacity of its microbial community to perform anaerobic oxidation of methane (AOM) linked to the reduction of the humic fraction of its NOM. Collected evidence demonstrates that electron-accepting functional groups (e.g., quinones) present in NOM fueled AOM by serving as a terminal electron acceptor. Indeed, while sulfate reduction was the predominant process, accounting for up to 42.5% of the AOM activities, the microbial reduction of NOM concomitantly occurred. Furthermore, enrichment of wetland sediment with external NOM provided a complementary electron-accepting capacity, of which reduction accounted for ∼100 nmol 13CH4 oxidized · cm-3 · day-1 Spectroscopic evidence showed that quinone moieties were heterogeneously distributed in the wetland sediment, and their reduction occurred during the course of AOM. Moreover, an enrichment derived from wetland sediments performing AOM linked to NOM reduction stoichiometrically oxidized methane coupled to the reduction of the humic analogue anthraquinone-2,6-disulfonate. Microbial populations potentially involved in AOM coupled to microbial reduction of NOM were dominated by divergent biota from putative AOM-associated archaea. We estimate that this microbial process potentially contributes to the suppression of up to 114 teragrams (Tg) of CH4 · year-1 in coastal wetlands and more than 1,300 Tg · year-1, considering the global wetland area.IMPORTANCE The identification of key processes governing methane emissions from natural systems is of major importance considering the global warming effects triggered by this greenhouse gas. Anaerobic oxidation of methane (AOM) coupled to the microbial reduction of distinct electron acceptors plays a pivotal role in mitigating methane emissions from ecosystems. Given their high organic content, wetlands constitute the largest natural source of atmospheric methane. Nevertheless, processes controlling methane emissions in these environments are poorly understood. Here, we provide tracer analysis with 13CH4 and spectroscopic evidence revealing that AOM linked to the microbial reduction of redox functional groups in natural organic matter (NOM) prevails in a tropical wetland. We suggest that microbial reduction of NOM may largely contribute to the suppression of methane emissions from tropical wetlands. This is a novel avenue within the carbon cycle in which slowly decaying NOM (e.g., humic fraction) in organotrophic environments fuels AOM by serving as a terminal electron acceptor.

Anaerobic Methanotrophic Archaea of the ANME-2d Cluster Are Active in a Low-sulfate, Iron-rich Freshwater Sediment.

ANaerobic MEthanotrophic (ANME) archaea remove the greenhouse gas methane from anoxic environments and diminish its flux to the atmosphere. High methane removal efficiencies are well documented in marine environments, whereas anaerobic oxidation of methane (AOM) was only recently indicated as an important methane sink in freshwater systems. Freshwater AOM-mediating microorganisms lack taxonomic identification and only little is known about metabolic adaptions to prevailing biogeochemical conditions. One of the first study sites providing information about AOM activity in freshwater sediment is Lake Ørn, a low-sulfate, iron-rich Danish lake. With the aim to identify freshwater AOM-mediating archaea, we incubated AOM-active anoxic, nitrate-free freshwater sediment from Lake Ørn with 13C-labeled methane (13CCH4) and 13C-labeled bicarbonate (13CDIC) and followed the assimilation of 13C into RNA by stable isotope probing. While AOM was active, 13CCH4 and probably also 13CDIC were incorporated into uncultured archaea of the Methanosarcinales-related cluster ANME-2d, whereas other known ANME lineages were not detected. This finding strongly suggests that ANME-2d archaea perform AOM coupled to sulfate and/or iron reduction and may have the capability of mixed assimilation of CH4 and DIC. ANME-2d archaea may thus play an important role in controlling methane emissions from nitrate-depleted and low-sulfate freshwater systems.

Trump order could affect energy prices, technology development

President Donald J. Trump’s March 28 order to reexamine or kill a host of federal actions to combat climate change might help lower U.S. energy prices but may hurt development of new energy technologies. And the decision means the U.S. will likely miss its emissions targets under an international climate change accord. Trump says his directive is an assault on what he calls burdensome energy regulations and policies, most of which are fossil-fuel related. He says the order will create jobs, particularly for U.S. coal miners. Among policies targeted are the Clean Power Plan to limit carbon dioxide emissions from new and existing coal-fired power plants and regulations to control methane emissions from oil and gas drilling. The order may contribute to a more diverse and affordable energy supply, says the American Chemistry Council, a chemical industry association. ACC adds that a variety of factors—market forces and state and regional

EPA scraps methane reporting for oil and gas industries

The Trump Administration has withdrawn an EPA request that oil and natural gas companies provide information on their methane emissions from field operations. The Obama Administration had sent the data request to some 15,000 oil and gas companies late last year. It asked for basic information on the numbers and types of equipment used at onshore drilling and production facilities as well as more detailed information on methane emission sources and control devices. Earlier in 2016, EPA issued methane control regulations for new oil and gas facilities but did not address existing facilities. The data collection rule was an attempt by the Obama EPA to learn more about oil and gas operations in preparation for emissions regulations at operating facilities. Oil and gas operations are the largest industrial source of methane, a greenhouse gas 25 times as potent as carbon dioxide, according to EPA. The U.S. is experiencing an oil

Performance of Biocover in Mitigating Fugitive Methane Emissions from Municipal Solid Waste Landfills in Cold Climates

AbstractManipulation of landfill covers to maximize oxidation capacity provides a promising complementary strategy for the control of methane emissions from landfills. Engineered biocovers (i.e., a...

A methane emission control strategy in the initial mining range at a spontaneous combustion-prone longwall face: A case study in coal 15, Shigang Mine, China

Abstract: Fast drainage is a key in balancing coal bed methane (CBM) control and coal fire prevention in highly gassy and spontaneous combustion-prone longwall faces in the initial mining range. In this case study, two similar working faces, the 15202 and 15203 faces of Shigang Mine, were studied for the CBM emission history and its control strategy in the initial mining range. The field observation results from the 15202 face show that the distance of the initial mining range can be estimated to be 40 m. It was found that there was a noticeable high-concentration phase during the initial mining range in the 15202 face. This high-concentration phase is caused by the CBM desorbed from the upper-close-Coal 14 after the initial caving of the immediate roof and the subsequently relieved overlying layers. In the 15203 face, a targeted CBM control strategy was proposed to supplement the basic CBM control strategy in the initial mining range. Firstly, an additional roadway was introduced to construct in-seam boreholes in the Coal 14 before the face advancement. Secondly, fractures between upper drainage roadway and Coal 14 were enhanced by a splitting blasting. The application results show that the high-concentration phase disappeared after the application of the new CBM control strategy. It is concluded that the proposed CBM control strategy in the initial mining range is effective to control CBM emission and prevent coal spontaneous combustion in the gob at Shigang Mine. This case study provides an important engineering practice example for the CBM emission control in other CBM-rich and spontaneous combustion-prone underground coal mines.

How Do Seagrasses Control Methane Emissions from Coastal Marine Environments?

How Do Seagrasses Control Methane Emissions from Coastal Marine Environments?

Top-down control of methane emission and nitrogen cycling by waterfowl.

Aquatic herbivores impose top-down control on the structure of wetland ecosystems, but the biogeochemical consequences of herbivory on methane (CH4 ) and nitrogen (N) are poorly known. To investigate the top-down effects of waterfowl on wetland biogeochemistry, we implemented exclosure experiments in a major waterfowl overwintering wetland in the southeastern United States over two growing seasons. We found that herbivory inhibited the oxidation of CH4 , leading to a mean increase in emission by 230% over control plots, and prevented nitrification, as indicated by low nitrate availability and undetectable emissions of nitrous oxide. Herbivory reduced belowground biomass of macrophytes, retarding the subsequent spring emergence of aerenchymous stems, effectively starving wetland soils of oxygen necessary for CH4 oxidation and nitrification. The recognition that important populations of aquatic herbivores may influence the capacity for wetlands to emit greenhouse gases and cycle N is particularly salient in the context of climate change and nutrient pollution mitigation goals. For example, our results suggest that (1) annual emissions of 23 Gg CH4 /yr from ~57 000ha of publicly owned waterfowl impoundments in the southeastern United States could be tripled by overgrazing and that (2) waterfowl impoundments may export as much N as agricultural fields. We discuss potential implications for habitat management in the context of historic wetland loss and waterfowl population recovery.

Innovations in Measuring Field Scale Biological Methane Oxidation at Two Soil-Covered Closed Landfills

One of the most promising and cost-effective options for control of low-level methane (CH4) emissions is the use of engineered bio-based systems. It has been proved that in landfill cover soil, micro-organisms remove CH4 from Landfill Gas (LFG) as the gas migrates through aerobic regions above the buried waste. However, one of the main issues delaying the field implementation of such techniques capable of reducing CH4 emissions from landfills is the lack of a proper field technique to assess the level of CH4 oxidation under field conditions. Only specialized Stable Isotope (SI) based methods are capable of such a task. Gas Push Pull Test (GPPT) method was developed and used to assess in-situ methane oxidation in two low-emitting closed landfills. Simple interpretations of the GPPT data was developed. Stable carbon isotope data was also obtained in conjunction with the GPPTs which provides an independent verification of CH4 oxidation. The GPPT analysis yielded an average percent oxidation of 40 and 52% for the two closed sites. The GPPT methane oxidation results agreed with the SI based values obtained from 20 above ground air samples from each of the closed sites. The study suggests that GPPT can be easily used to as-sess methane oxidation in in the field. Additionally, the results of the GPPT and the Isotopes analysis were lower than the overall oxidation rates estimated from the modeled generation and the measured tracer-based total emissions testing performed at the two landfills. Keywords: Closed landfills, gas push pull test, greenhouse gas emissions, LFG, methane emissions, methane oxidation.

Methane turnover and environmental change from Holocene lipid biomarker records in a thermokarst lake in Arctic Alaska

Arctic lakes and wetlands contribute a substantial amount of methane to the contemporary atmosphere, yet profound knowledge gaps remain regarding the intensity and climatic control of past methane emissions from this source. In this study, we reconstruct methane turnover and environmental conditions, including estimates of mean annual and summer temperature, from a thermokarst lake (Lake Qalluuraq) on the Arctic Coastal Plain of northern Alaska for the Holocene by using source-specific lipid biomarkers preserved in a radiocarbon-dated sediment core. Our results document a more prominent role for methane in the carbon cycle when the lake basin was an emergent fen habitat between ~12,300 and ~10,000 cal yr BP, a time period closely coinciding with the Holocene Thermal Maximum (HTM) in North Alaska. Enhanced methane turnover was stimulated by relatively warm temperatures, increased moisture, nutrient supply, and primary productivity. After ~10,000 cal yr BP, a thermokarst lake with abundant submerged mosses evolved, and through the mid-Holocene temperatures were approximately 3°C cooler. Under these conditions, organic matter decomposition was attenuated, which facilitated the accumulation of submerged mosses within a shallower Lake Qalluuraq. Reduced methane assimilation into biomass during the mid-Holocene suggests that thermokarst lakes are carbon sinks during cold periods. In the late-Holocene from ~2700 cal yr BP to the most recent time, however, temperatures and carbon deposition rose and methane oxidation intensified, indicating that more rapid organic matter decomposition and enhanced methane production could amplify climate feedback via potential methane emissions in the future.

Greenhouse gas emissions estimation from proposed El Fukhary Landfill in the Gaza Strip

ABSTRACTLandfills throughout the world are contributing to the global warming problem. This is due to the existence of the most important greenhouse gases (GHG) in landfill gas (LFG); namely, methane (CH4) and carbon dioxide (CO2). The aim of this paper is quantifying the total potential emissions, as well as the variation in production with time of CH4 from a proposed landfill (El Fukhary landfill) in the Gaza Strip, Palestine. Two different methods were adopted in order to quantify the total potential CH4 emissions; the Default methodology based on the intergovernmental panel on climate change (IPCC) 1996 revised guidelines and the Landfill Gas Emissions model (LandGEM V3.02) provided by the United States Environmental Protection Agency (EPA). The second objective of the study has been accomplished using the Triangle gas production model. The results obtained from both Default and LandGEM methods were found to be nearly the same. For 25 years of disposing MSW, El Fukhary landfill expected to have potential CH4 emissions of 1.9542 ± 0.0037 ×109 m3. Triangle model showed that the peak production in term of CH4 would occur in 2043; 28 years beyond the open year. Moreover, the model shows that 50 % of the gas will be produced approximately at the middle of the total duration of gas production. Proper control of Methane emissions from El Fukhary landfill is highly suggested in order to reduce the harmful effects on the environment.Implications: Although, GHG emissions are extensively discussed in the developed countries throughout the world, it has gained little concern in the developing countries because they are forced most of the time to put environmental concerns at the end of their priority list. The paper shows that developing countries have to start recognizing their fault and change their way of dealing with environmental issues especially GHG emissions (mainly Methane and carbon dioxide). The authors estimated the potential methane emissions from a proposed central landfill that has been approved to be built in Palestine, a country that is classified as a developing country.

Assessment of alternative disposal methods to reduce greenhouse gas emissions from municipal solid waste in India.

Open dumping, the most commonly practiced method of solid waste disposal in Indian cities, creates serious environment and economic challenges, and also contributes significantly to greenhouse gas emissions. The present article attempts to analyse and identify economically effective ways to reduce greenhouse gas emissions from municipal solid waste. The article looks at the selection of appropriate methods for the control of methane emissions. Multivariate functional models are presented, based on theoretical considerations as well as the field measurements to forecast the greenhouse gas mitigation potential for all the methodologies under consideration. Economic feasibility is tested by calculating the unit cost of waste disposal for the respective disposal process. The purpose-built landfill system proposed by Yedla and Parikh has shown promise in controlling greenhouse gas and saving land. However, these studies show that aerobic composting offers the optimal method, both in terms of controlling greenhouse gas emissions and reducing costs, mainly by requiring less land than other methods.

Attribution of changes in global wetland methane emissions from pre-industrial to present using CLM4.5-BGC

An understanding of potential factors controlling methane emissions from natural wetlands is important to accurately project future atmospheric methane concentrations. Here, we examine the relative contributions of climatic and environmental factors, such as precipitation, temperature, atmospheric CO2 concentration, nitrogen deposition, wetland inundation extent, and land-use and land-cover change, on changes in wetland methane emissions from preindustrial to present day (i.e., 1850–2005). We apply a mechanistic methane biogeochemical model integrated in the Community Land Model version 4.5 (CLM4.5), the land component of the Community Earth System Model. The methane model explicitly simulates methane production, oxidation, ebullition, transport through aerenchyma of plants, and aqueous and gaseous diffusion. We conduct a suite of model simulations from 1850 to 2005, with all changes in environmental factors included, and sensitivity studies isolating each factor. Globally, we estimate that preindustrial methane emissions were higher by 10% than present-day emissions from natural wetlands, with emissions changes from preindustrial to the present of +15%, −41%, and −11% for the high latitudes, temperate regions, and tropics, respectively. The most important change is due to the estimated change in wetland extent, due to the conversion of wetland areas to drylands by humans. This effect alone leads to higher preindustrial global methane fluxes by 33% relative to the present, with the largest change in temperate regions (+80%). These increases were partially offset by lower preindustrial emissions due to lower CO2 levels (10%), shifts in precipitation (7%), lower nitrogen deposition (3%), and changes in land-use and land-cover (2%). Cooler temperatures in the preindustrial regions resulted in our simulations in an increase in global methane emissions of 6% relative to present day. Much of the sensitivity to these perturbations is mediated in the model by changes in methane substrate production and the areal extent of wetlands. The detrended interannual variability of high-latitude methane emissions is explained by the variation in substrate production and wetland inundation extent, whereas the tropical emission variability is explained by both of those variables and precipitation.

Analysis of gob gas venthole production performances for strata gas control in longwall mining

Longwall mining of coal seams affects a large area of overburden by deforming it and creating stress-relief fractures, as well as bedding plane separations, as the mining face progresses. Stress-relief fractures and bedding plane separations are recognized as major pathways for gas migration from gas-bearing strata into sealed and active areas of the mines. In order for strata gas not to enter and inundate the ventilation system of a mine, gob gas ventholes (GGVs) can be used as a methane control measure. The aim of this paper is to analyze production performances of GGVs drilled over a longwall panel. These boreholes were drilled to control methane emissions from the Pratt group of coals due to stress-relief fracturing and bedding plane separations into a longwall mine operating in the Mary Lee/Blue Creek coal seam of the Upper Pottsville Formation in the Black Warrior Basin, Alabama. During the course of the study, Pratt coal's reservoir properties were integrated with production data of the GGVs. These data were analyzed by using material balance techniques to estimate radius of influence of GGVs, gas-in-place and coal pressures, as well as their variations during mining.The results show that the GGVs drilled to extract gas from the stress-relief zone of the Pratt coal interval is highly effective in removing gas from the Upper Pottsville Formation. The radii of influence of the GGVs were in the order of 330–380m, exceeding the widths of the panels, due to bedding plane separations and stress relieved by fracturing. Material balance analyses indicated that the initial pressure of the Pratt coals, which was around 648KPa when longwall mining started, decreased to approximately 150KPa as the result of strata fracturing and production of released gas. Approximately 70% of the initial gas-in-place within the area of influence of the GGVs was captured during a period of one year.

Valuing the Ozone-Related Health Benefits of Methane Emission Controls

Methane is a greenhouse gas that oxidizes to form ground-level ozone, itself a greenhouse gas and a health-harmful air pollutant. Reducing methane emissions will both slow anthropogenic climate change and reduce ozone-related mortality. We estimate the benefits of reducing methane emissions anywhere in the world for ozone-related premature mortality globally and for eight geographic regions. Our methods are consistent with those used by the US Government to estimate the social cost of carbon (SCC). We find that the global short- and long-term premature mortality benefits due to reduced ozone production from methane mitigation are (2011) $790 and $1775 per tonne methane, respectively. These correspond to approximately 70 and 150 % of the valuation of methane’s global climate impacts using the SCC after extrapolating from carbon dioxide to methane using global warming potential estimates. Results for monetized benefits are sensitive to a number of factors, particularly the choice of elasticity to income growth used when calculating the value of a statistical life. The benefits increase for emission years further in the future. Regionally, most of the global mortality benefits accrue in Asia, but 10 % accrue in the United States. This methodology can be used to assess the benefits of methane emission reductions anywhere in the world, including those achieved by national and multinational policies.

Multiregional environmental comparison of fossil fuel power generation—Assessment of the contribution of fugitive emissions from conventional and unconventional fossil resources

In this paper we investigate the influence of fugitive methane emissions from coal, natural gas, and shale gas extraction on the greenhouse gas (GHG) impacts of fossil fuel power generation through its life cycle. A multiregional hybridized life cycle assessment (LCA) model is used to evaluate several electricity generation technologies with and without carbon dioxide capture and storage. Based on data from the UNFCCC and other literature sources, it is shown that methane emissions from fossil fuel production vary more widely than commonly acknowledged in the LCA literature. This high variability, together with regional disparity in methane emissions, points to the existence of both significant uncertainty and natural variability. The results indicate that the impact of fugitive methane emissions can be significant, ranging from 3% to 56% of total impacts depending on type of technology and region. Total GHG emissions, in CO2-eq./kWh, vary considerably according to the region of the power plant, plant type, and the choice of associated fugitive methane emissions, with values as low as 0.08kg CO2-eq./kWh and as high as 1.52kg CO2-eq./kWh. The variability indicates significant opportunities for controlling methane emissions from fuel chains.

Planning of methane emission control from hoggery using an inexact two-stage optimization model

This study aims to develop an inexact two-stage optimization model to gather manure distributed over the southwest Taiwan and convert it into bioenergy. In the method, local optimization of each hauling zone is performed first using a gray mixed-integer programming model. Then, the hauling zones are prioritized by its performance on four gray scenarios. Although the biogas yield and the manure generation rate are ambiguous, one can easily evaluate his opportunity and risk by gray interval, which is a group of values within the lower and upper bounds. The analyses reveal that the biogas yield dominates the profit in this project, and it leads to the failure of the project when the biogas yield is below the level of 0.2 m3 kg−1. With the goal of reducing 45% of methane emissions from pig farms, seven hauling zones are required to be developed. The farmers living in these zones from the project get carbon credits ranging from 478 to 3269 ton CO2eq per year, and the investors own the carbon credits in the range of 3264–11820 ton CO2eq per year. Through the carbon trading, both the investors and pig farmers are able to make profits by trading their carbon credits.Implications:Biogas recovered from hoggery can be used as a bioenergy source and mitigate the atmospheric greenhouse effect and global warming. This research develops an inexact two-stage optimization model to evaluate the potential of gathering manure for biogas and converting it into bioenergy. The analyses reveal that the biogas yield dominates the profit in this project, and it leads to the failure of the project when the biogas yield is below the level of 0.2 m3 kg−1. This study has provided a useful reference for the management of biogas production and carbon trading from hoggery for bioenergy.

Eddy covariance based methane flux in Sundarbans mangroves, India

We report the initial results of the methane flux measured using eddy covariance method during summer months from the world’s largest mangrove ecosystem, Sundarbans of India. Mangrove ecosystems are known sources for methane (CH4) having very high global warming potential. In order to quantify the methane flux in mangroves, an eddy covariance flux tower was recently erected in the largest unpolluted and undisturbed mangrove ecosystem in Sundarbans (India). The tower is equipped with eddy covariance flux tower instruments to continuously measure methane fluxes besides the mass and energy fluxes. This paper presents the preliminary results of methane flux variations during summer months (i.e., April and May 2012) in Sundarbans mangrove ecosystem. The mean concentrations of CH4 emission over the study period was 1682 ± 956 ppb. The measured CH4 fluxes computed from eddy covariance technique showed that the study area acts as a net source for CH4 with daily mean flux of 150.22 ± 248.87 mg m−2 day−1. The methane emission as well as its flux showed very high variability diurnally. Though the environmental conditions controlling methane emission is not yet fully understood, an attempt has been made in the present study to analyse the relationships of methane efflux with tidal activity. This present study is part of Indian Space Research Organisation–Geosphere Biosphere Program (ISRO–GBP) initiative under ‘National Carbon Project’.

Biofiltration of methane using an inorganic filter bed: influence of inlet load and nitrogen concentration

An upflow lab-scale biofilter was operated with an inorganic filter material to control methane emissions. The influence of the inlet load on methane removal was investigated and the maximum elimination capacity obtained was 36 g/(m3·h) for an inlet load of 95 g/(m3·h). The influence of the nitrogen concentration, which was provided in the form of nitrate through a nutrient solution, was also determined. We established that the optimum nitrogen concentration required for biofilter operation decreases with the methane inlet load. In fact, it was around 0·75 g/L for inlet loads comprised between 55 and 95 g/(m3·h) and of 0·50 g/L when the inlet load was comprised between 20 and 55 g/(m3·h). During this study, a nitrogen concentration of 1·00 g/L inhibited methane removal in the biofilter. In addition, the use of a nitrogen concentration superior to its optimum level can cause, in the long-term run, severe damages to the biofilter performance.