Showing papers on "Natural gas published in 2016"

Upward revision of global fossil fuel methane emissions based on isotope database

Abstract: Revisions in isotopic source signatures reveal that global total fossil fuel methane emissions from industry plus natural geological seepage are much larger than thought. Stefan Schwietzke et al. re-evaluate the global methane budget and the contribution of the fossil fuel industry to methane emissions on the basis of long-term global methane and methane carbon isotope records. They find that total fossil fuel methane emissions (fossil fuel industry plus natural geological methane seepage) are not increasing over time, but are 60–110 per cent greater than was previously thought. They also conclude that methane emissions from natural gas, oil and coal production and their usage are 20–60 per cent greater than inventories and that methane emissions from natural gas as a fraction of production have declined from about 8 per cent to 2 per cent over the past three decades. Methane has the second-largest global radiative forcing impact of anthropogenic greenhouse gases after carbon dioxide, but our understanding of the global atmospheric methane budget is incomplete. The global fossil fuel industry (production and usage of natural gas, oil and coal) is thought to contribute 15 to 22 per cent of methane emissions1,2,3,4,5,6,7,8,9,10 to the total atmospheric methane budget11. However, questions remain regarding methane emission trends as a result of fossil fuel industrial activity and the contribution to total methane emissions of sources from the fossil fuel industry and from natural geological seepage12,13, which are often co-located. Here we re-evaluate the global methane budget and the contribution of the fossil fuel industry to methane emissions based on long-term global methane and methane carbon isotope records. We compile the largest isotopic methane source signature database so far, including fossil fuel, microbial and biomass-burning methane emission sources. We find that total fossil fuel methane emissions (fossil fuel industry plus natural geological seepage) are not increasing over time, but are 60 to 110 per cent greater than current estimates1,2,3,4,5,6,7,8,9,10 owing to large revisions in isotope source signatures. We show that this is consistent with the observed global latitudinal methane gradient. After accounting for natural geological methane seepage12,13, we find that methane emissions from natural gas, oil and coal production and their usage are 20 to 60 per cent greater than inventories1,2. Our findings imply a greater potential for the fossil fuel industry to mitigate anthropogenic climate forcing, but we also find that methane emissions from natural gas as a fraction of production have declined from approximately 8 per cent to approximately 2 per cent over the past three decades.

Methane emissions from the 2015 Aliso Canyon blowout in Los Angeles, CA

Abstract: Single-point failures of natural gas infrastructure can hamper methane emission control strategies designed to mitigate climate change. The 23 October 2015 blowout of a well connected to the Aliso Canyon underground storage facility in California resulted in a massive release of natural gas. Analysis of methane and ethane data from dozens of plume transects, collected during 13 research-aircraft flights between 7 November 2015 and 13 February 2016, shows atmospheric leak rates of up to 60 metric tons of methane and 4.5 metric tons of ethane per hour. At its peak, this blowout effectively doubled the methane emission rate of the entire Los Angeles basin and, in total, released 97,100 metric tons of methane to the atmosphere.

Methane Leaks from Natural Gas Systems Follow Extreme Distributions.

Abstract: Future energy systems may rely on natural gas as a low-cost fuel to support variable renewable power. However, leaking natural gas causes climate damage because methane (CH4) has a high global warming potential. In this study, we use extreme-value theory to explore the distribution of natural gas leak sizes. By analyzing ∼15 000 measurements from 18 prior studies, we show that all available natural gas leakage data sets are statistically heavy-tailed, and that gas leaks are more extremely distributed than other natural and social phenomena. A unifying result is that the largest 5% of leaks typically contribute over 50% of the total leakage volume. While prior studies used log-normal model distributions, we show that log-normal functions poorly represent tail behavior. Our results suggest that published uncertainty ranges of CH4 emissions are too narrow, and that larger sample sizes are required in future studies to achieve targeted confidence intervals. Additionally, we find that cross-study aggregation o...

CH4 conversion to value added products: Potential, limitations and extensions of a single step heterogeneous catalysis

Abstract: Natural gas is envisioned as a primary source of energy and hydrocarbons in the foreseeable future. Though shale gas has recently become abundant, it has two main concerns: its environmental impact and sustainable utilization. The former is the result of recent reports of natural gas emissions and flares into the environment, where it acts as a powerful greenhouse gas, whereas the latter is dictated by the need for efficient hydrocarbon utilization. Modern natural gas processing units that yield clean fuels and feedstock from methane, CH 4 , require extremely large capital investments and are not economical in remote natural gas extraction sites. Single step (direct), non-syngas based catalytic routes of CH 4 conversion to value added products have not been competitive economically and need to be reevaluated in the light of shale gas availability. This perspective discusses general considerations for the desired hydrocarbon products, the thermodynamic limitations involved in a single step conversion of CH 4 and heterogeneous catalytic routes based on high temperatures and oxide based catalysts. We then discuss other catalysts and methods of CH 4 activation that have recently emerged and are conceptually different from metal oxide catalyst based routes, such as those using sulfur or halogens. Lastly, we discuss a possible route of CH 4 monetization beyond the first reactive product (such as ethylene oligomerization into fuels), as well as currently explored photo(electro)chemical routes of CH 4 activation.

Postextraction Separation, On-Board Storage, and Catalytic Conversion of Methane in Natural Gas: A Review

Abstract: In today’s perspective, natural gas has gained considerable attention, due to its low emission, indigenous availability, and improvement in the extraction technology. Upon extraction, it undergoes several purification protocols including dehydration, sweetening, and inert rejection. Although purification is a commercially established technology, several drawbacks of the current process provide an essential impetus for developing newer separation protocols, most importantly, adsorption and membrane separation. This Review summarizes the needs of natural gas separation, gives an overview of the current technology, and provides a detailed discussion of the progress in research on separation and purification of natural gas including the benefits and drawbacks of each of the processes. The transportation sector is another growing sector of natural gas utilization, and it requires an efficient and safe on-board storage system. Compressed natural gas (CNG) and liquefied natural gas (LNG) are the most common form...

Inhibition of methane and natural gas hydrate formation by altering the structure of water with amino acids.

Abstract: Natural gas hydrates are solid hydrogen-bonded water crystals containing small molecular gases. The amount of natural gas stored as hydrates in permafrost and ocean sediments is twice that of all other fossil fuels combined. However, hydrate blockages also hinder oil/gas pipeline transportation, and, despite their huge potential as energy sources, our insufficient understanding of hydrates has limited their extraction. Here, we report how the presence of amino acids in water induces changes in its structure and thus interrupts the formation of methane and natural gas hydrates. The perturbation of the structure of water by amino acids and the resulting selective inhibition of hydrate cage formation were observed directly. A strong correlation was found between the inhibition efficiencies of amino acids and their physicochemical properties, which demonstrates the importance of their direct interactions with water and the resulting dissolution environment. The inhibition of methane and natural gas hydrate formation by amino acids has the potential to be highly beneficial in practical applications such as hydrate exploitation, oil/gas transportation, and flow assurance. Further, the interactions between amino acids and water are essential to the equilibria and dynamics of many physical, chemical, biological, and environmental processes.

Welfare and Distributional Implications of Shale Gas

Abstract: Technological innovations in horizontal drilling and hydraulic fracturing have enabled tremendous amounts of natural gas to be extracted profitably from underground shale formations that were long thought to be uneconomical. In this paper, we provide the first estimates of broad-scale welfare and distributional implications of this supply boom. We provide new estimates of supply and demand elasticities, which we use to estimate the drop in natural gas prices that is attributable to the supply expansion. We find large, positive welfare impacts for four broad sectors of gas consumption (residential, commercial, industrial, and electric power) and a negative impact for producers, with variation across regions. We then examine the evidence for a gas-led “manufacturing renaissance” and for pass-through to prices of products such as retail natural gas, retail electricity, and commodity chemicals. We conclude with a discussion of environmental externalities from unconventional natural gas, including limitations of the current regulatory environment. Overall, we find that between 2007 and 2013 the shale gas revolution led to an increase in welfare for natural gas consumers and producers of $48 billion per year, but more data are needed on the extent and valuation of the environmental impacts of shale gas production.

Methane Emissions from Conventional and Unconventional Natural Gas Production Sites in the Marcellus Shale Basin.

Abstract: There is a need for continued assessment of methane (CH4) emissions associated with natural gas (NG) production, especially as recent advancements in horizontal drilling combined with staged hydraulic fracturing technologies have dramatically increased NG production (we refer to these wells as “unconventional” NG wells). In this study, we measured facility-level CH4 emissions rates from the NG production sector in the Marcellus region, and compared CH4 emissions between unconventional NG (UNG) well pad sites and the relatively smaller and older “conventional” NG (CvNG) sites that consist of wells drilled vertically into permeable geologic formations. A top-down tracer-flux CH4 measurement approach utilizing mobile downwind intercepts of CH4, ethane, and tracer (nitrous oxide and acetylene) plumes was performed at 18 CvNG sites (19 individual wells) and 17 UNG sites (88 individual wells). The 17 UNG sites included four sites undergoing completion flowback (FB). The mean facility-level CH4 emission rate amo...

Contribution of oil and natural gas production to renewed increase in atmospheric methane (2007–2014): top–down estimate from ethane and methane column observations

Abstract: . Harmonized time series of column-averaged mole fractions of atmospheric methane and ethane over the period 1999–2014 are derived from solar Fourier transform infrared (FTIR) measurements at the Zugspitze summit (47° N, 11° E; 2964 m a.s.l.) and at Lauder (45° S, 170° E; 370 m a.s.l.). Long-term trend analysis reveals a consistent renewed methane increase since 2007 of 6.2 [5.6, 6.9] ppb yr−1 (parts-per-billion per year) at the Zugspitze and 6.0 [5.3, 6.7] ppb yr−1 at Lauder (95 % confidence intervals). Several recent studies provide pieces of evidence that the renewed methane increase is most likely driven by two main factors: (i) increased methane emissions from tropical wetlands, followed by (ii) increased thermogenic methane emissions due to growing oil and natural gas production. Here, we quantify the magnitude of the second class of sources, using long-term measurements of atmospheric ethane as a tracer for thermogenic methane emissions. In 2007, after years of weak decline, the Zugspitze ethane time series shows the sudden onset of a significant positive trend (2.3 [1.8, 2.8] × 10−2 ppb yr−1 for 2007–2014), while a negative trend persists at Lauder after 2007 (−0.4 [−0.6, −0.1] × 10−2 ppb yr−1). Zugspitze methane and ethane time series are significantly correlated for the period 2007–2014 and can be assigned to thermogenic methane emissions with an ethane-to-methane ratio (EMR) of 12–19 %. We present optimized emission scenarios for 2007–2014 derived from an atmospheric two-box model. From our trend observations we infer a total ethane emission increase over the period 2007–2014 from oil and natural gas sources of 1–11 Tg yr−1 along with an overall methane emission increase of 24–45 Tg yr−1. Based on these results, the oil and natural gas emission contribution (C) to the renewed methane increase is deduced using three different emission scenarios with dedicated EMR ranges. Reference scenario 1 assumes an oil and gas emission combination with EMR = 7.0–16.2 %, which results in a minimum contribution C > 39 % (given as lower bound of 95 % confidence interval). Beside this most plausible scenario 1, we consider two less realistic limiting cases of pure oil-related emissions (scenario 2 with EMR = 16.2–31.4 %) and pure natural gas sources (scenario 3 with EMR = 4.4–7.0 %), which result in C > 18 % and C > 73 %, respectively. Our results suggest that long-term observations of column-averaged ethane provide a valuable constraint on the source attribution of methane emission changes and provide basic knowledge for developing effective climate change mitigation strategies.

Electricity-Natural Gas Operation Planning With Hourly Demand Response for Deployment of Flexible Ramp

Abstract: This paper proposes an integrated stochastic day-ahead scheduling model to dispatch hourly generation and load resources and deploy flexible ramping for managing the variability of renewable energy system. A comprehensive framework for the natural gas transportation network is considered to address the dispatchability of a fleet of fuel-constrained natural gas-fired units. System uncertainties include the day-ahead load and renewable generation forecast errors. Illustrative examples demonstrate that the real-time natural gas delivery can directly impact the hourly dispatch, flexible ramp deployment, and power system operation cost. Meanwhile, the demand side participation can mitigate the dependency of electricity on natural gas by providing a viable option for flexible ramp when the natural gas system is constrained.

Chemical Methanation of CO2: A Review

Abstract: The chemical methanation of CO2 may become a ubiquitous process for the production of renewable substitute natural gas from any CO2 source coupled with renewable hydrogen. The produced gas can be fed into the natural gas pipeline or used as fuel. Over the past few years, great efforts have been made in developing the process of CO2 methanation. In this paper, the chemical methanation, which is the most common process, is reviewed. The purpose is to present a comprehensive updated review of the process. The CO2 methanation, covering the process mechanisms, thermodynamics, catalysts, kinetics, and reactors are discussed with the aim to outline the pathways for the future development of the methanation process.

Water-Stable Anionic Metal-Organic Framework for Highly Selective Separation of Methane from Natural Gas and Pyrolysis Gas.

Abstract: A 3D water-stable anionic metal–organic framework [Zn4(hpdia)2]·[NH2(CH3)2]·3DMF·4H2O (FJI-C4) was constructed based on an elaborate phosphorus-containing ligand 5,5′-(hydroxyphosphoryl)diisophthalic acid (H5hpdia). FJI-C4 with narrow one-dimensional (1D) pore channels exhibits high selectivity of C3H8/CH4 and C2H2/CH4. It is the first time for the MOF which contains phosphorus for selective separation of methane from natural gas and pyrolysis gas.

Tunable Polyaniline-Based Porous Carbon with Ultrahigh Surface Area for CO2 Capture at Elevated Pressure

Abstract: Natural gas is the cleanest fossil fuel source. However, natural gas wells typically contain considerable amounts of CO2, with on-site CO2 capture necessary. Solid sorbents are advantageous over traditional amine scrubbing due to their relatively low regeneration energies and non-corrosive nature. However, it remains a challenge to improve the sorbent's CO2 capacity at elevated pressures relevant to natural gas purification. Here, the synthesis of porous carbons derived from a 3D hierarchical nanostructured polymer hydrogel, with simple and effective tunability over the pore size distribution is reported. The optimized surface area reaches 4196 m2 g−1, which is among the highest of carbon-based materials, with abundant micro- and narrow mesopores (2.03 cm3 g−1 with d < 4 nm). This carbon exhibits a record-high CO2 capacity among reported carbons at elevated pressure (i.e., 28.3 mmol g−1 total adsorption at 25 °C and 30 bar). This carbon also shows good CO2/CH4 selectivity and excellent cyclability. Molecular simulations suggest increased CO2 density in micro- and narrow mesopores at high pressures. This is consistent with the observation that these pores are mainly responsible for the material's high-pressure CO2 capacity. This work provides insights into material design and further development for CO2 capture from natural gas.