Gases, Volume 4, Issue 3 (September 2024) – 11 articles

Since retrofitting existing natural gas-fired (NGF) power plants is an essential strategy for enhancing their efficiency and controlling greenhouse gas emissions, this paper compares the carbon footprint of natural gas-fired power generation from an NGF power plant in Brazil (BR-NGF) with and without retrofitting. The former scenario entails retrofitting the BR-NGF power plant with combined-cycle gas turbine (CCGT) technology. In contrast, the latter involves continuing the BR-NGF power plant operation with open-cycle gas turbine (OCGT) technology. Our analysis considers the BR-NGF power plant’s life cycle (construction, operation, and decommissioning) and the natural gas’ life cycle (natural gas extraction and processing, liquefaction, liquefied natural gas transportation, regasification, and combustion). Moreover, it is based on data from primary and secondary sources, mainly the Ecoinvent database and the ReCiPe 2016 method. For OCGT, the results showed that the BR-NGF power plant and the natural gas life cycles are responsible for 620.87 gCO₂eq./kWh and 178.58 gCO₂eq./kWh, respectively. For CCGT, these values are 450.04 gCO₂eq./kWh and 129.30 gCO₂eq./kWh. Our findings highlight the relevance of the natural gas’ life cycle, signaling additional opportunities for reducing the overall carbon footprint of natural gas-fired power generation. Full article

This paper investigates the operating benefits and limitations of utilizing carbon dioxide in hydro-pneumatic energy storage systems, a form of compressed gas energy storage technology, when the systems are deployed offshore. Allowing the carbon dioxide to transition into a two-phase fluid will improve the storage density for long-duration energy storage. A preliminary comparative study between an air-based and a carbon dioxide-based subsea hydro-pneumatic energy storage system is first presented. The analysis is based on thermodynamic calculations assuming ideal isothermal conditions to quantify the potential augmentation in energy storage capacity for a given volume of pressure containment when operating with carbon dioxide in lieu of air. This is followed by a transient thermal analysis of the carbon dioxide-based hydro-pneumatic energy storage system, taking into account the real scenario of a finite thermal resistance for heat exchange between the gas and the surrounding seawater. Results from numerical modelling revealed that the energy storage capacity of a carbon dioxide-based subsea hydro-pneumatic energy storage system operating under ideal isothermal conditions can be theoretically increased by a factor of 2.17 compared to an identical air-based solution. The numerical modelling revealed that, under real conditions under which transient effects resulting from a finite thermal resistance are accounted for, the achievable factor is lower, depending on the charging and discharging time, the initial temperature, and whether a polyethene liner for corrosion prevention is considered or not. Full article

This paper presents an analysis of NO₂ emissions in Mashhad City utilizing statistical evaluations and the Cisco Network Model. The present study begins by evaluating NO₂ emissions through statistical analysis, followed by the application of histograms and radar statistical appraisals. Subsequently, a model execution logic is developed using the Cisco Network Model to further understand the distribution and sources of NO₂ emissions in the city. Additionally, the research incorporates managerial insights by employing Petri Net modeling, which enables a deeper understanding of the dynamic interactions within the air quality management system. This approach aids in identifying critical control points and optimizing response strategies, thus enhancing the overall effectiveness of urban air pollution mitigation efforts. The findings of this study provide valuable insights into the levels of NO₂ pollution in Mashhad City and offer a structured approach to modeling NO₂ emissions for effective air quality management strategies which can be extended to the other megacities as well. Full article

In this work, we analyze non-Darcy two-component single-phase isothermal flow in naturally fractured tight gas reservoirs. The model is applied in a scenario of enhanced gas recovery (EGR) with the possibility of carbon dioxide storage. The properties of the gases are obtained via the Peng–Robinson equation of state. The finite volume method is used to solve the governing partial differential equations. This process leads to two subsystems of algebraic equations, which, after linearization and use of an operator splitting method, are solved by the conjugate gradient (CG) and biconjugate gradient stabilized (BiCGSTAB) methods for determining the pressure and fraction molar, respectively. We include inertial effects using the Barree and Conway model and gas slippage via a more recent model than Klinkenberg’s, and we use a simplified model for the effects of effective stress. We also utilize a mesh refinement technique to represent the discrete fractures. Finally, several simulations show the influence of inertial, slippage and stress effects on production in fractured tight gas reservoirs. Full article

Methane is a powerful greenhouse gas with a 25 times higher 100-year warming potential than carbon dioxide and is a target for mitigation to achieve climate goals. To control and curb methane emissions, estimates are required from the sources and sectors which are typically generated using bottom-up methods. However, recent studies have shown that national and international bottom-up approaches can significantly underestimate emissions. In this study, we present three bottom-up approaches used to estimate methane emissions from all emission sectors in the Denver-Julesburg basin, CO, USA. Our data show emissions generated from all three methods are lower than historic measurements. A Tier 1/2 approach using IPCC emission factors estimated 2022 methane emissions of 358 Gg (0.8% of produced methane lost by the energy sector), while a Tier 3 EPA-based approach estimated emissions of 269 Gg (0.2%). Using emission factors informed by contemporary and region-specific measurement studies, emissions of 212 Gg (0.2%) were calculated. The largest difference in emissions estimates were a result of using the Mechanistic Air Emissions Simulator (MAES) for the production and transport of oil and gas in the DJ basin. The MAES accounts for changes to regulatory practice in the DJ basin, which include comprehensive requirements for compressors, pneumatics, equipment leaks, and fugitive emissions, which were implemented to reduce emissions starting in 2014. The measurement revealed that normalized gas loss is predicted to have been reduced by a factor of 20 when compared to 10-year-old normalization loss measurements and a factor of 10 less than a nearby oil and production area (Delaware basin, TX); however, we suggest that more measurements should be made to ensure that the long-tail emission distribution has been captured by the modeling. This study suggests that regulations implemented by the Colorado Department of Public Health and Environment could have reduced emissions by a factor of 20, but contemporary regional measurements should be made to ensure these bottom-up calculations are realistic. Full article

As carbon capture and storage (CCS) technologies mature, the concept of a low-carbon or net-zero-carbon economy becomes more and more feasible. While many chemical and energy products do not contain carbon in their compounds, the upstream production process does. An added CCS module allows the removal of carbon emissions from the production process, which expands the value chain. This paper focuses on one of such commodities—low-carbon-intensity ammonia (LCIA). Even though ammonia is carbon-free in its final product, it is commonly made from natural gas, and the production process could generate significant carbon emissions. The idea of LCIA is to reduce the carbon footprint of the ammonia production process (e.g., blue ammonia) or eliminate carbon from the production process (e.g., green ammonia via electrolysis) so that the entire supply chain is decarbonized. The goal of this paper is two-fold. We first explore the US domestic market and the international market for LCIA. We then discuss relevant federal and local policies that could help grow markets for LCIA. The agricultural sector will be the center of the discussion, which consumes an estimated 70–90% of the global ammonia supply as fertilizers. The paper also examines other potential uses of LCIA, such as alternative fuels for decarbonizing agricultural machinery and transportation sectors. Finally, we argue that developing a comprehensive LCIA value chain, supported by dedicated policy measures and broad stakeholder engagement, is critical for materializing the potential of LCIA in contributing to a climate-resilient and sustainable economy. Full article

To reduce and convert biodegradable waste into energy-rich biogas, anaerobic digestion technology is usually employed. Hence, this takes place inside the biogas digester. Studies have revealed that these digesters are designed and constructed using bricks, cement, and metal; often require a large footprint; and are bulky and expensive. The innovation of portable biogas digesters has come into the market to address these challenges. This present review provides an overview of the in-depth and comprehensive information on portable biogas digesters in the literature. Areas covered in the review include the modification of the biogas digester design, the need for a portable biogas digester, recent studies on the factors affecting the performance of portable biogas digesters, and specific assumptions taken into consideration for designing any portable biogas digester. Convincingly, portable biogas digesters appeal to small rural families because of their ease of operation, maintenance, and ability to save space. The material for the construction and comparison of the portable biogas digester with other designs and the economic feasibility of the system were also reviewed. Implications: The full-scale design, fabrication, and utilization of a portable biogas digester are viable but not widely employed compared to other designs. However, there is a lack of readily available information on the portable design of biogas digesters. This review presents various aspects relating to portable biogas digesters and the quality of biogas produced. Therefore, the review suits audiences in energy process design and engineers, energy researchers, academics, and economists. Full article

Phased injection of natural gas into internal combustion marine engines is a promising solution for optimizing performance and reducing harmful emissions, particularly unburned methane, a potent greenhouse gas. This innovative practice distinguishes itself from continuous injection because it allows for more precise control of the combustion process with only a slight increase in system complexity. By synchronizing the injection of natural gas with the intake and exhaust valve opening and closing times while also considering the gas path in the manifolds, methane release into the atmosphere is significantly reduced, making a substantial contribution to efforts to address climate change. Moreover, phased injection improves the efficiency of marine engines, resulting in reduced overall fuel consumption, lower fuel costs, and increased ship autonomy. This technology was tested on a single-cylinder, large-bore, four-stroke research engine designed for marine applications, operating in dual-fuel mode with diesel and natural gas. Performance was compared with that of the conventional continuous feeding method. Evaluation of the effect on equivalent CO₂ emissions indicates a potential reduction of up to approximately 20%. This reduction effectively brings greenhouse gas emissions below those of the diesel baseline case, especially when injection control is combined with supercharging control to optimize the air–fuel ratio. In this context, the boost pressure in DF was reduced from 3 to 1.5 bar compared with the FD case. Full article

The systematic analysis of measurement data allows a large amount of information to be obtained from existing measurements in a short period of time. Especially in vehicle development, many measurements are performed, and large amounts of data are collected in the process of emission calibration. With the introduction of Real Driving Emissions Tests, the need for targeted analysis for efficient and robust calibration of a vehicle has further increased. With countless possible test scenarios, test-by-test analysis is no longer possible with the current state-of-the-art in calibration, as it takes too much time and can disregard relevant data when analyzed manually. In this article, therefore, a methodology is presented that automatically analyzes exhaust measurement data in the context of emission calibration and identifies emission-related critical sequences. For this purpose, moving analyzing windows are used, which evaluate the exhaust emissions in each sample of the measurement. The detected events are stored in tabular form and are particularly suitable for condensing the collected measurement data to a required amount for optimization purposes. It is shown how different window settings influence the amount and duration of detected events. With the example used, a total amount of 454 events can be identified from 60 measurements, reducing 184,623 s of measurements to a relevant amount of 12,823 s. Full article

Climate projects can become one of the key tools for decarbonization in Russia. They have powerful potential in terms of solving the problems of reducing emissions and increasing the absorption of greenhouse gases, as well as monetization potential for businesses. Despite the geopolitical crisis and sanctions imposed on Russia, certain opportunities for implementing climate projects have remained accessible. This study aims to provide a comprehensive analysis of the current status, including the regulations and approved methodologies, prospects, and challenges for climate projects in the carbon market in Russia. It also offers an overview of international carbon market mechanisms and analyses the advantages and disadvantages of the nature-based and technological solutions of climate projects for carbon sequestration. This, in turn, can facilitate the realization of future strategies for realizing the bigger potential of Russian climate projects in the domestic and international carbon markets. This research also provides up-to-date data on the current situation of the carbon market in Russia. Full article

In a previous study, we demonstrated a change in membrane morphology and gas separation performance by varying the recipe of a casting solution based on polysulfone in a certain solvent system. Although all results were reproducible, all used solvents were harmful and not sustainable. In this study, the solvents tetrahydrofuran (THF) and N,N-dimethylacetamide (DMAc) are replaced by the more sustainable solvents 2-methyl-tetrahydrofuran (2M-THF), N-butyl pyrrolidinone (NBP) and cyclopentyl methyl ether (CPME). The gas permeation performance and, for the first time, morphology of the membranes before and after solvent replacement were determined and compared by single gas permeation measurements and SEM microscopy. It is shown that THF can be replaced by 2M-THF and NBP without decreasing the gas permeation performance. With CPME replacing THF, no membranes were formed. Systems with 2M-THF as a THF alternative showed the best gas permeation results. Permeances for the tested gases oxygen (O₂), nitrogen (N₂), carbon dioxide (CO₂) and methane (CH₄) were 5.91 × 10⁻², 8.84 × 10⁻³, 4.00 × 10⁻¹ and 1.00 × 10⁻² GPU, respectively. Permselectivities of those membranes for the gas pairs O₂/N₂, CO₂/N₂ and CO₂/CH₄ were 6.7, 38.3 and 34.0, respectively. When also replacing DMAc in the solvent system, no or only porous membranes were obtained, even if the precipitation procedure was adjusted. These findings indicate that a complete replacement of the solvent system without affecting the membrane morphology or gas permeation performance is not possible. By varying the temperature of the precipitation bath, the formation of mechanically stable PSU membranes is possible only if THF is replaced by 2M-THF. Full article