Drainage and utilization of Chinese coal mine methane with a coal–methane co-exploitation model: Analysis and projections

Coal mine methane (CMM) released during coal mining attributes to unsafe working conditions and environmental impact. China, the largest coal producer in the world, is facing problems associated with CMM such as fatal gas accidents and intense greenhouse gas emission along the path to deep mining. Complicated geological conditions featured with low permeability, high gas pressure and gas content of Chinese coal seams have been hindering the coal extraction. To solve these problems, a model of coal–methane co-exploitation is proposed. This model realizes the extraction of two resources with safety ensured and has been successfully applied in Huainan coalfield, China. The current situation of drainage and utilization of CMM in China are diagnosed. Connections between the coal production, methane emissions, drainage and utilization are analyzed. Estimations of future coal production, methane emissions, drainage and utilization are made in a co-exploitation based scenario. The emitted, drained and utilized CMM are projected to reach 26.6, 13.3 and 9.3 billion m³, respectively by adapting the assumption of 3800 million metric tons of coal production by 2020.     

Transport and reaction processes affecting the attenuation of landfill gas in cover soils

Methane and trace organic gases produced in landfill waste are partly oxidized in the top 40 cm of landfill cover soils under aerobic conditions. The balance between the oxidation of landfill gases and the ingress of atmospheric oxygen into the soil cover determines the attenuation of emissions of methane, chlorofluorocarbons, and hydrochlorofluorocarbons to the atmosphere. This study was conducted to investigate the effect of oxidation reactions on the overall gas transport regime and to evaluate the contributions of various gas transport processes on methane attenuation in landfill cover soils. For this purpose, a reactive transport model that includes advection and the Dusty Gas Model for simulation of multicomponent gas diffusion was used. The simulations are constrained by data from a series of counter-gradient laboratory experiments. Diffusion typically accounts for over 99% of methane emission to the atmosphere. Oxygen supply into the soil column is driven exclusively by diffusion, whereas advection outward offsets part of the diffusive contribution. In the reaction zone, methane consumption reduces the pressure gradient, further decreasing the significance of advection near the top of the column. Simulations suggest that production of water or accumulation of exopolymeric substances due to microbially mediated methane oxidation can significantly reduce diffusive fluxes. Assuming a constant rate of methane production within a landfill, reduction of the diffusive transport properties, primarily due to exopolymeric substance production, may result in reduced methane attenuation due to limited O(2) -ingress.     

Tapping the leakages: Methane losses, mitigation options and policy issues for Russian long distance gas transmission pipelines

The Russian natural gas industry is the world's largest producer and transporter of natural gas. This paper aims to characterize the methane emissions from Russian natural gas transmission operations, to explain projects to reduce these emissions, and to characterize the role of emissions reduction within the context of current GHG policy. It draws on the most recent independent measurements at all parts of the Russian long distance transport system made by the Wuppertal Institute in 2003 and combines these results with the findings from the US Natural Gas STAR Program on GHG mitigation options and economics.With this background the paper concludes that the methane emissions from the Russian natural gas long distance network are approximately 0.6% of the natural gas delivered. Mitigating these emissions can create new revenue streams for the operator in the form of reduced costs, increased gas throughput and sales, and earned carbon credits. Specific emissions sources that have cost-effective mitigation solutions are also opportunities for outside investment for the Joint Implementation Kyoto Protocol flexibility mechanism or other carbon markets.     

Greenhouse Impact Due to the Use of Combustible Fuels: Life Cycle Viewpoint and Relative Radiative Forcing Commitment

Extensive information on the greenhouse impacts of various human actions is important in developing effective climate change mitigation strategies. The greenhouse impacts of combustible fuels consist not only of combustion emissions but also of emissions from the fuel production chain and possible effects on the ecosystem carbon storages. It is important to be able to assess the combined, total effect of these different emissions and to express the results in a comprehensive way. In this study, a new concept called relative radiative forcing commitment (RRFC) is presented and applied to depict the greenhouse impact of some combustible fuels currently used in Finland. RRFC is a ratio that accounts for the energy absorbed in the Earth system due to changes in greenhouse gas concentrations (production and combustion of fuel) compared to the energy released in the combustion of fuel. RRFC can also be expressed as a function of time in order to give a dynamic cumulative picture on the caused effect. Varying time horizons can be studied separately, as is the case when studying the effects of different climate policies on varying time scales. The RRFC for coal for 100 years is about 170, which means that in 100 years 170 times more energy is absorbed in the atmosphere due to the emissions of coal combustion activity than is released in combustion itself. RRFC values of the other studied fuel production chains varied from about 30 (forest residues fuel) to 190 (peat fuel) for the 100-year study period. The length of the studied time horizon had an impact on the RRFC values and, to some extent, on the relative positions of various fuels.     

Biogas upgrading and utilization from ICEs towards stationary molten carbonate fuel cell systems

Biogas production from anaerobic digestion has increased rapidly in the last years, in many parts of the world, mainly due to its local scale disposition and to its potential on greenhouse gases (GHG) emissions mitigation. Biogas can be used as fuel for combined heat and power systems (CHP), in particular for internal combustion engines (ICEs). In recent investigations, fuel cells have been considered as alternative CHP systems. In the present article, two different energy conversion systems are compared: a 1.4 MW class MCFC system, running on pipeline natural gas, and an in situ ICE, running on biogas. In the first case, biogas is considered as a source fuel to obtain upgraded gas to be injected in the natural gas grid. In such scenario, the location of the fuel cell power plant is no longer strictly connected to the anaerobic digester site. Several energy balances are evaluated, considering different upgrading techniques and different biogas methane/carbon dioxide ratios.     

Capturing fugitive methane emissions from natural gas compressor buildings

Fugitive methane emissions account for about 50% of the greenhouse gas (GHG) emissions from the Canadian conventional oil and gas sector. Sources include leaks in natural gas transmission facilities such as pipelines and compressor stations. There are three sources of methane emissions in a compressor station. The first is emissions resulting from incomplete combustion in the engine; the second is leaks in valves, flanges and other equipment in the building; and the third results from instrument venting. Fugitive methane emissions may be in low concentration relative to air, and thus cannot be destroyed by conventional combustion (below flammability limits of about 5-16%). The present study investigates the feasibility of capturing methane emissions from a compressor station. Computer modelling of the flow patterns of lean methane emissions inside the building is used to show the influence of doors, vents and leak location. Simulations show that for a typical building most fugitive methane exits through the ridge vent provided that the main doors remain closed. When the extraction rate through the ridge vent is controlled, the methane concentration is at acceptable levels for destruction in a catalytic flow reverse reactor, that is, in the range of 0.1-1% by volume.     

Characteristics of coal mine ventilation air flows

Coal mine methane (CMM) is not only a greenhouse gas but also a wasted energy resource if not utilised. Underground coal mining is by far the most important source of fugitive methane emissions, and approximately 70% of all coal mining related methane is emitted to the atmosphere through mine ventilation air. Therefore, research and development on mine methane mitigation and utilisation now focuses on methane emitted from underground coal mines, in particular ventilation air methane (VAM) capture and utilisation. To date, most work has focused on the oxidation of very low concentration methane. These processes may be classified based on their combustion kinetic mechanisms into thermal oxidation and catalytic oxidation. VAM mitigation/utilisation technologies are generally divided into two basic categories: ancillary uses and principal uses. However, it is possible that the characteristics of ventilation air flows, for example the variations in methane concentration and the presence of certain compounds, which have not been reported so far, could make some potential VAM mitigation and utilisation technologies unfeasible if they cannot cope with the characteristics of mine site ventilation air flows. Therefore, it is important to understand the characteristics of mine ventilation air flows. Moreover, dust, hydrogen sulphide, sulphur dioxide, and other possible compounds emitted through mine ventilation air into the atmosphere are also pollutants. Therefore, this paper presents mine-site experimental results on the characteristics of mine ventilation air flows, including methane concentration and its variations, dust loadings, particle size, mineral matter of the dust, and other compounds in the ventilation air flows. The paper also discusses possible correlations between ventilation air characteristics and underground mining activities.     

Assessment of the greenhouse effect impact of technologies used for energy recovery from municipal waste: A case for England

Waste management activities contribute to global greenhouse gas emissions approximately by 4%. In particular the disposal of waste in landfills generates methane that has high global warming potential. Effective mitigation of greenhouse gas emissions is important and could provide environmental benefits and sustainable development, as well as reduce adverse impacts on public health. The European and UK waste policy force sustainable waste management and especially diversion from landfill, through reduction, reuse, recycling and composting, and recovery of value from waste. Energy from waste is a waste management option that could provide diversion from landfill and at the same time save a significant amount of greenhouse gas emissions, since it recovers energy from waste which usually replaces an equivalent amount of energy generated from fossil fuels. Energy from waste is a wide definition and includes technologies such as incineration of waste with energy recovery, or combustion of waste-derived fuels for energy production or advanced thermal treatment of waste with technologies such as gasification and pyrolysis, with energy recovery. The present study assessed the greenhouse gas emission impacts of three technologies that could be used for the treatment of Municipal Solid Waste in order to recover energy from it. These technologies are Mass Burn Incineration with energy recovery, Mechanical Biological Treatment via bio-drying and Mechanical Heat Treatment, which is a relatively new and uninvestigated method, compared to the other two. Mechanical Biological Treatment and Mechanical Heat Treatment can turn Municipal Solid Waste into Solid Recovered Fuel that could be combusted for energy production or replace other fuels in various industrial processes. The analysis showed that performance of these two technologies depends strongly on the final use of the produced fuel and they could produce GHG emissions savings only when there is end market for the fuel. On the other hand Mass Burn Incineration generates greenhouse gas emission savings when it recovers electricity and heat. Moreover the study found that the expected increase on the amount of Municipal Solid Waste treated for energy recovery in England by 2020 could save greenhouse gas emission, if certain Energy from Waste technologies would be applied, under certain conditions.     

An approach for measuring methane emissions from whole farms

Estimates of enteric methane (CH4) emissions from ruminants are typically measured by confining animals in large chambers, using head hoods or masks, or by a ratiometric technique involving sampling respired air of the animal. These techniques are not appropriate to evaluate large-scale farm emissions and the variability between farms that may be partly attributed to different farm management. This study describes the application of an inverse-dispersion technique to calculate farm emissions in a controlled tracer-release experiment. Our study was conducted at a commercial dairy farm in southern Alberta, Canada (total of 321 cattle, including 152 lactating dairy cows). Sulfur hexafluoride (SF6) and CH4 were released from 10 outlet locations (barn and open pens) using mass-flow controllers. A Lagrangian stochastic (LS) dispersion model was then used to infer farm emissions from downwind gas concentrations. Concentrations of SF6 and CH4 were measured by gas chromatography analysis and open path lasers, respectively. Wind statistics were measured with a three-dimensional sonic anemometer. Comparing the inferred emissions with the known release rate showed we recovered 86% of the released CH4 and 100% of the released SF6. The location of the concentration observations downwind of the farm was critically important to the success of this technique.     

Methane emissions from grazing cattle using point-source dispersion

The ability to accurately measure greenhouse gas (GHG) emissions is essential to gauge our ability to reduce these emissions. Enteric methane from ruminants is an important but often difficult source to quantify since it depends on the amount and type of feed intake. Unfortunately, many of the available measurement techniques for estimating enteric methane emissions can impose a change in feed intake. Our study evaluates a nonintrusive technique that uses a novel approach (point-source dispersion with multiple open-path concentrations) to calculate enteric methane emissions from grazing cattle, reported as the major source of GHG in many countries, particularly Australia. A scanner with a mounted open-path laser was used to measure methane concentration across five paths above a paddock containing 18 grazing cattle over 16 d. These data were used along with wind statistics in a dispersion model (WindTrax) to estimate an average herd methane emission rate over 10-mm intervals. Enteric methane emissions from the herd grazing a combination of Rhodes grass (Chlotis gayana Kunth) and Leucaena [Leucaena leucocephala (Lam.)] averaged (+/- SD) 141 (+/- 147) g animal(-1) d(-1). In a release-recovery experiment, the technique accounted for 77% of the released methane at a single point. Our study shows the technique generates more reliable methane emissions during daytime (unstable stratification).     

Environmental impacts of absorption-based CO2 capture unit for post-combustion treatment of flue gas from coal-fired power plant

This study assesses potential environmental impacts of the absorption-based carbon dioxide (CO₂) capture unit that is integrated to coal-fired power plant for post-combustion treatment of flue gas. The assessment was performed by identifying potential pollutants and their sources as well as amounts of emissions from the CO₂ capture unit and also by reviewing toxicology, potential implications to human health and the environment, as well as the environmental laws and regulations associated with such pollutants. The assessment shows that, while offering a significant environmental benefit through a reduction of greenhouse gas emissions, the installation of CO₂ capture units for post-combustion treatment might induce unintentional and potential burdens to human health and the environment through four emission pathways, including treated gas, process wastes, fugitive emissions, and accidental releases. Such burdens nevertheless can be predetermined and properly mitigated through a well-established environmental management program and mitigation measures. Recommendations to minimize these impacts are provided in this paper.     

The Potential Use of Synthetic Aperture Radar for Estimating Methane Ebullition From Arctic Lakes1

Abstract: Arctic lakes are significant emitters of methane (CH₄), a potent greenhouse gas, to the atmosphere; yet no rigorous quantification of the magnitude and variability of pan‐Arctic lake emissions exists. In this study, we demonstrate the potential for a new method using synthetic aperture radar (SAR) imagery to detect methane bubbles in lake ice to scale up whole‐lake measurements of CH₄ ebullition (bubbling) to regional scales. We estimated ebullition from lakes, which is often the dominant mode of lake emissions, by mapping the distribution of bubble clusters frozen in early winter ice across surfaces of seven tundra lakes and one boreal forest lake in Alaska. Applying previously measured ebullition rates associated with four distinct classes of bubble clusters found in lake ice, we estimated whole‐lake emissions from individual lakes. The percent surface area of lake ice covered with bubbles (R² = 0.68) and CH₄ ebullition rates from lakes (R² = 0.59) and were correlated with radar return values from RADARSAT‐1 Standard Beam mode 3 for the tundra lakes, suggesting that with appropriate scaling and consideration for variability in lake‐ice conditions, this technique has the potential to be used for estimating broader‐scale regional and pan‐Arctic lake methane emissions.     

Application of modeling and simulation tools in costs and pollution monitoring

This paper presents the development and application of process modeling and simulation tools to aid in the monitoring and measuring of pollution from industry, and investigate a plant's overall performance. A case study of a generic reduction plant is investigated, taking into account the underlying principles that determine the amount of fluoride emissions released from the plant's processes. The simulation study includes the investigation of the gas cleaning system within the plant, such as the system's operating relationships between the scrubbing efficiency, wear of the scrubber filter bags, maintenance costs and its response to the change of scrubbing circulation. Two sets of simulation runs are performed to seek a balance for the plant's overall system performance, taking into account environmental issues (fluoride emissions) and cost. The final simulation result demonstrates that cost savings can be achieved when the plant operates in a cleaner manner.     

美国和中国油气系统甲烷排放状况

文章通过调研、分析美国和中国近年来油气系统中甲烷排放状况,对比分析美国与中国应用的主要甲烷计算方法,表明:美国油气系统中对甲烷排放量的计算方法可采用1996IPCC指南中提供的第一层次(Tier1)和第二层次(Tier2)法,计算结果相对比较准确,甲烷的排放呈逐年增加趋势;中国油气系统中甲烷排放量的计算方法目前只限于1996IPCC指南中提供的Tier1法,中国甲烷排放量相对于美国等发达国家较少,但整体呈增长趋势。     

国内外石油公司甲烷排放差异性分析及启示

甲烷排放管控是国际石油公司推动低碳能源转型的一项重要举措,也是达成净零碳排放愿景的一个重要手段。研究发现,国内外石油公司的油气生产活动水平、甲烷排放控制水平、甲烷排放核算方法等3个方面均存在较大差异性。我国油井单井产量低,地面工程量大、工艺复杂,流程工艺中甲烷排放突出,油气系统甲烷排放水平较高,油气生产甲烷排放控制水平与国外石油公司相比尚有较大差距,与国外甲烷排放核算方法也存在较大差异性。着眼于甲烷排放管控,我国石油公司应充分衡量甲烷排放现状、生产活动水平、甲烷排放控制措施经济性和适用性等多重因素,严格控制潜在甲烷排放节点,并进一步做好甲烷排放检测、监测和数据统计工作,持续完善甲烷排放报告和核查体系。     

Abundances and flux estimates of volatile organic compounds from a dairy cowshed in Germany

Animal husbandry and manure treatment have been specifically documented as significant sources of methane, ammonia, nitrous oxide, and particulate matter. Although volatile organic compounds (VOCs) are also produced, much less information exists concerning their impact. We report on chemical ionization mass spectrometry and photo-acoustic spectroscopy measurements of mixing ratios of VOCs over a 2-wk measurement period in a large cowshed at the Federal Agricultural Research Centre (FAL) in Mariensee, Germany. The high time resolution of these measurements enables insight into the sources of the emissions in a typical livestock management setting. During feeding hours and solid manure removal, large mixing ratio spikes of several VOCs were observed and correlated with simultaneous methane, carbon dioxide, and ammonia level enhancements. The subsequent decay of cowshed concentration due to passive cowshed ventilation was used to model emission rates, which were dominated by ethanol and acetic acid, followed by methanol. Correlations of VOC mixing ratios with methane or ammonia were also used to calculate cowshed emission factors and to estimate potential nationwide VOC emissions from dairy cows. The results ranged from around 0.1 Gg carbon per year (1 Gg = 10(9) g) for nonanal and dimethylsulfide, several Gg carbon per year for volatile fatty acids and methanol, to over 10 Gg carbon per year of emitted ethanol. While some estimates were not consistent between the two extrapolation methods, the results indicate that animal husbandry VOC emissions are dominated by oxygenated compounds and may be a nationally but not globally significant emission to the atmosphere.     

Radiative Forcing Due to Anthropogenic Greenhouse Gas Emissions from Finland: Methods for Estimating Forcing of a Country or an Activity

The objective of this study was to assess the radiative forcing due to Finnish anthropogenic greenhouse gas emissions in three scenarios. All the Kyoto Protocol gases, i.e., CO₂, CH₄, N₂O, and fluorinated gases, were included. The calculations showed that forcing due to Finnish emissions will increase in the case of all gases except methane by the year 2100. In 1990, radiative forcing due to Finland's emission history of all Kyoto Protocol gases was 3.2 mW/m², of which 71% was due to carbon dioxide, 17% to methane, and the rest to nitrous oxide. In 1990 the share of fluorinated gases was negligible. The share of methane in radiative forcing is decreasing, whereas the shares of carbon dioxide and of fluorinated gases are increasing and that of nitrous oxide remains nearly constant. The nonlinear features concerning additional concentrations in the atmosphere and radiative forcing due to emissions caused by a single country or activity are also considered. Radiative forcing due to Finnish emissions was assessed with two different approaches, the marginal forcing approach and the averaged forcing approach. The impact of the so-called background scenario, i.e., the scenario for concentration caused by global emissions, was also estimated. The difference between different forcing models at its highest was 40%, and the averaged forcing approach appeared to be the more recommendable. The effect of background concentrations in the studied cases was up to 11%. Hence, the choice of forcing model and background scenario should be given particular attention.     

A low pressure direct gas injection system for a four stroke LPG: Diesel dual fuel engine

Internal combustion engines running on gaseous fuels produce low torque because the inducted gaseous fuel displaces air and reduces the volumetric efficiency. This can be overcome by injecting the gaseous fuel directly into the cylinder after the intake of air is completed. This work is a step in developing and demonstrating a cost effective system, as such systems are not readily available for small applications. A low-pressure gas injector was mounted on the cylinder barrel of a fully instrumented dual fuel engine. Its location is such that the injector will be exposed to the cylinder gases about 65.5 degrees before bottom dead center, where the cylinder pressure and temperature will be relatively low. An electronic controller was also developed to time the injection process to occur after the intake valve closes and also to control the duration of injection (quantity). Experiments were conducted with LPG (Liquefied petroleum gas) as the primary fuel that was injected with this new system and diesel as the pilot fuel at the rated speed of 1500 rpm with different amounts of LPG at 80% and 100% load. Comparisons of performance, combustion and emissions with the conventional manifold injection of LPG were done. The system allowed greater amounts of LPG to be used without knock as compared to manifold injection. On the whole the developed system has potential for application in small dual fuel and spark ignited gas engines and can be taken up for further optimization.     

Emissions study of co-firing waste carpet in a rotary kiln

Post-consumer carpet represents a high volume, high energy content waste stream. As a fuel for co-firing in cement kilns, waste carpet, like waste tires, has potential advantages. Technological challenges to be addressed include assessing potential emissions, in particular NO emissions (from nylon fiber carpets), and optimizing the carpet feed system. This paper addresses the former. Results of pilot-scale rotary kiln experiments demonstrate the potential for using post-consumer waste carpet as a fuel in cement kilns. Continuous feeding of shredded carpet fiber and ground carpet backing, at rates of up to 30% of total energy input, resulted in combustion without transient puffs and with almost no increase in CO and other products of incomplete combustion as compared to kiln firing natural gas only. NO emissions increased with carpet waste co-firing due to the nitrogen content of nylon fiber. In these experiments with shredded fiber and finely ground backing, carpet nitrogen conversion to NO ranged from 3 to 8%. Conversion increased with enhanced mixing of the carpet material and air during combustion. Carpet preparation and feeding method are controlling factors in fuel N conversion.     

美国油气行业国家温室气体清单和报送体系

甲烷是由人类活动造成的仅次于二氧化碳的第二大温室气体,大幅度减少甲烷排放有助于降低近期温升,是实现巴黎协定目标的必要手段,也是中国实现“碳中和”目标的重要抓手。相比其他排放源,油气行业的甲烷减排最快、最有经济性。而有效的减排政策和监管必须建立在完整、准确的甲烷排放清单基础上。文章以甲烷为重点,概述了美国国家温室气体清单和油气行业的报送制度,介绍了两个报送体系的覆盖范围、要求等相关差异,说明了设施界定、排放因子和活动水平来源、监测方法以及有待改进之处,并针对中国油气行业甲烷排放数据的质量改善提出了建议。