Fuels

Intermediate temperature solid oxide fuel cell (SOFC) operation provides numerous advantages such as high combined heat and power (CHP) efficiency, potentially long-term material stability, and the use of low-cost materials. However, due to the sluggish kinetics of the oxygen reduction reaction at intermediate temperatures (500–700 °C), the cathode of SOFC requires an efficient and stable catalyst. Significant progress in the development of cathode materials has been made over recent years. In this article, multiple strategies for improving the performance of cathode materials have been extensively reviewed such as A- and B-site doping of perovskites, infiltration of catalytic active materials, the use of core-shell composites, etc. Emphasis has been given to intrinsic properties such as chemical and thermal stability and oxygen transport number. Furthermore, to avoid any insulating phase formation at the cathode/electrolyte interface, strategies for interfacial layer modifications have also been extensively reviewed and summarized. Based on major technical challenges, future research directions have been proposed for efficient and stable intermediate temperature solid oxide fuel cell (SOFC) operation. Full article

In current times, the diminishing reserves of petroleum, increased energy consumption across various sectors, and their consequential environmental impact have become apparent. Consequently, it is necessary to develop sustainable and eco-friendly energy sources to meet growing demands. The article aimed to blend castor and neem oils (in a 50:50 ratio) to rectify the drawbacks present in castor biodiesel such as elevated kinematic viscosity and density. Response surface methodology was used to study the optimization of the two-step biodiesel production process through the use of a central composite design (CCD). For the esterification step, a methanol-to-oil molar ratio of 7.5:1, 1.75 wt.% of H₂SO₄, and a temperature of 55 °C were optimal. In the transesterification step, optimized conditions included a methanol-to-oil molar ratio of 9:1, 2.50 wt.% of calcium oxide, a temperature of 55 °C, and a stirring speed of 900 rpm, resulting in a 93% yield of methyl ester. Different properties of produced biodiesel were examined using the standard values provided by EN 14214 and ASTM D6751. The production of biodiesel from a mixture of castor and neem oils did not have any adverse impacts on food security. Full article

How accurate are current estimation methods for fugitive methane emissions in methane-producing facilities, and how do they vary across biogas plants, wastewater treatment plants (WWTPs), and landfills? Based on this, the hypothesis posited in this study is that current methods significantly underestimate methane emissions, particularly in WWTPs and biogas plants, due to limitations in accounting for recovered methane and the reliance on general parameters such as the oxidation factor. To test this, a comparative analysis was carried out involving 33 biogas plants, 87 WWTPs, and 119 landfills in the Iberian Peninsula, comparing officially recorded data with estimates derived from our own calculations. Our findings confirm the lack of precision in current emission estimation methods, particularly for WWTPs and biogas plants, where factors like the omission of recovered methane lead to underreporting. This study highlights that WWTPs emit the largest amount of methane due to their organic material processing, exceeding emissions from landfills and biogas plants. In contrast, methods for estimating emissions in landfills are found to be more reliable. The results suggest that improving calculation methodologies, especially for WWTPs and biogas plants, as well as enhancing leak monitoring and methane recovery systems, is crucial to reducing the environmental impact of methane-producing facilities. Full article

In this work, dry carbonization (DC) and hydrothermal carbonization (HTC) of refuse-derived fuel (RDF) pellets were conducted to evaluate the physical, chemical, and fuel properties of the produced chars. In the dry carbonization tests, biomass sawdust was incorporated in different proportions on the samples to minimize agglomeration caused by the melting of the plastic fraction. The experiments were carried out in a temperature of 400 °C (DC) and 250–300 °C (HTC), in a residence time of 30 min. The respective chars and hydrochars were characterized according to their mass yield, apparent density, proximate, elemental, and mineral composition, chlorine content, high heating value, thermogravimetric profile, and surface functional groups. The results showed that the dry carbonization of RDF pellets with biomass incorporation, followed by a washing step, resulted in the production of chars with improved properties such as higher fixed carbon and higher heating value (HHV) (25–26 MJ/kg) and lower ash and chlorine content. Additionally, the HTC experiments demonstrated that hydrochars showed improved properties without the need for biomass addition and washing, however, with no significant difference in the HHV (20–21 MJ/kg). Therefore, DC of RDF pellets with 10% biomass incorporation seems to be a promising option to overcome the constraints of RDF utilization as an alternative fuel. Full article

Poor wellbore cleaning is a significant challenge in oil drilling, primarily due to the accumulation of cuttings at the bottom of the well, particularly in deviated and horizontal wells. This study addresses this issue by employing Computational Fluid Dynamics (CFD) with the commercial software ANSYS FLUENT (2023-R1) to simulate a solid–liquid multiphase flow in an annulus. The primary objective is to analyze the cuttings concentration, pressure loss, and solid velocity profiles across various drilling parameters, including drill pipe rotation, the flow rate, rate of penetration, inclination angle, and fluid rheology. Our results underscore the critical role of these parameters in enhancing cuttings transport efficiency. Specifically, the drill pipe rotation, flow rate, and rate of penetration emerge as the most influential factors affecting the wellbore cleaning performance. With a validated model exhibiting an average error of 4.24%, this study provides insights into optimizing drilling operations to improve wellbore cleaning and increase hydrocarbon recovery. Full article

In recent years, due to the spike in natural gas spot prices, gas-fired power corporations’ operating costs have skyrocketed. Traditional power generation corporations have gradually been withdrawing from gas power generation investment, replaced by oil and gas enterprises with upstream resources. The development of gas-fired power plants helps to maintain the stability of the power grid and has a positive effect on the realization of carbon neutrality goals. At present, most of the financial evaluation methods for gas power generation projects tend to focus on the static tariffs of the project itself and lack consideration for the overall contribution to the industry chain and the latest “gas–electricity price linkage” mechanisms in China, leading to oil and gas enterprises reducing investment in gas-fired power plants due to yield constraints. In this paper, a financial evaluation methodology for gas power generation projects based on the industrial chain and the “gas–electricity price linkage” mechanism was proposed. The investment return characteristics of specific gas power generation projects under the “gas–electricity price linkage” mechanism in different provinces were revealed through this methodology. Considering the characteristics and industrial development trends in major provinces in China, investment and operation strategies for gas power generation were proposed. These studies provide oil and gas enterprises with references and suggestions for future investment decisions for new gas power generation projects. Full article

As the mining depth increases, the effect of stress on the gas adsorption of coal gradually becomes significant. There are significant differences in the pore volume, specific surface area, and adsorption characteristics of coal before and after stress. In this study, the porosity variation characteristics of coal were studied using axial and confining pressure loading processes, and volumetric stress was introduced to characterize the pore variation law of coal under triaxial stress. By calculating the stress values at different burial depths, gas isothermal adsorption experiments were conducted on coal under different stress effects. The Langmuir equation, D-A equation, and Freundlich empirical formula were used to fit the adsorption experimental results. Combining experiments and models to predict the adsorbed and free gas content under stress, we described the gas adsorption law of coal under different stress effects. Full article

Hydraulic fracturing has enabled production from unconventional reservoirs in the U.S., but production rates often decline sharply, limiting recovery factors to under 10%. This study proposes an optimization workflow for the CO₂ huff-n-puff process for multistage-fractured horizontal wells in the Wolfcamp A formation in the Delaware Basin. The potential for enhanced oil recovery and CO₂ sequestration simultaneously was addressed using a coupled geomechanics–reservoir simulation. Geomechanical properties were derived from a 1D mechanical earth model and integrated into reservoir simulation to replicate hydraulic fracture geometries. The fracture model was validated using a robust production history matching. A fluid phase behavior analysis refined the equation of state, and 1D slim tube simulations determined a minimum miscibility pressure of 4300 psi for CO₂ injection. After the primary production phase, various CO₂ injection rates were tested from 1 to 25 MMSCFD/well, resulting in incremental oil recovery ranging from 6.3% to 69.3%. Different injection, soaking and production cycles were analyzed to determine the ideal operating condition. The optimal scenario improved cumulative oil recovery by 68.8% while keeping the highest CO₂ storage efficiency. The simulation approach proposed by this study provides a comprehensive and systematic workflow for evaluating and optimizing CO₂ huff-n-puff in hydraulically fractured wells, enhancing the recovery factor of unconventional reservoirs. Full article

In this research work, the feasibility of using fusel oil, a by-product of the sugar–alcohol industry, as an LVLC solvent in blends with straight vegetable oils (SVOs) and diesel was investigated. Concretely, diesel/fusel oil/sunflower oil (D/FO/SO) and diesel/fusel oil/castor oil (D/FO/CO) triple blends were prepared and characterized by measuring the most important physicochemical properties, i.e., viscosity, density, cold flow properties, flash point and cetane number. An appreciable improvement in cold flow values has been achieved with triple blends, without compromising properties such as calorific value and cetane number. Likewise, the triple blends meet the viscosity and density requirements specified by the European quality standard EN 14214 and the American standard ASTM D6751. After characterization, the triple blends were used on a diesel engine, evaluating different parameters such as power output, opacity, exhaust emissions (CO and NO_x) and consumption at different engine loads. The results indicate that as the biofuel content in the blend increases, engine power decreases while fuel consumption rises. Nevertheless, the values obtained with D/FO/CO are better than those for D/FO/SO and are also very similar to those of fossil diesel. Regarding opacity values and NO_x emissions obtained with the utilization of the triple blends, they are lower than those produced by diesel. However, in the case of CO emissions, it depends on the type of oil used, with the samples prepared with castor oil exhibiting the best results. Full article

The aim of this research is to investigate the environmental emission effects and combustion properties of burning different types of FAME biodiesel fuels in an industrial oil burner. These burner heads are used in many areas of industry for heating various boilers and tube furnaces. The fuels used, the area of use, the emission norm values, and the climatic conditions are key factors in this investigation. In this research, two plant-based oils are examined, the properties of which have been compared to standard commercial heating oil. The raw material of the two tested bio-based components was rapeseed. The main gas emission parameters CO, THC, CO₂, O₂, HC, water content, and consumption data were measured. The measurements were performed in an AVL engine brake platform infrastructure, where gas emissions were measured with an AVL AMA i60 FTIR emission gas analyzer, fuel consumption was meticulously gauged using a fuel flow meter, fuel temperature was monitored using an AVL 745 fuel temperature conditioning system, and air consumption was measured with an AVL Flowsonix intake air flow meter. The measurement results showed that both tested biofuels can be burned stably in industrial oil burners, have favorable properties in terms of ignition and flame extinction tendencies, and there is no significant difference in emission parameters compared to standard fuel oil. Full article

The high externalized and still partly unknown costs of fossil fuels through air pollution from combustion, and their limited resources have caused mankind to (re)turn to renewable sources such as wind, solar, and biomass to meet its energy needs. Converting biomass to synthesis gas is advantageous since it can utilize a wide variety of (waste) feedstocks to obtain an energetic and versatile product at low cost in large quantities. Gasification is no new technology; yet in recent years, biomass gasification has attracted significant attention. Due to the non-depletable nature of agricultural waste and similar biomass side streams, which have little value and can bring environmental problems when mismanaged such as methane emissions, it is possible to obtain cheap electrical or thermal energy through the gas produced with high efficiencies. Combined heat and power (CHP) is the preferred use case, and recently the focus has moved to polygeneration, e.g., to make value-added products from the synthesis gas. Fischer–Tropsch synthesis from coal-derived syngas is now being complemented by the gas fermentation of biobased synthesis gas, where microorganisms yield materials from CO/H₂ (and CO₂) in an anaerobic process and from CH₄/O₂ in an aerobic process. Syngas methanation offers an alternative route to produce synthetic natural gas (SNG, or bio-SNG) as additional feedstock for gas fermentation. Materials made from syngas are decoupled from primary agricultural operations and do not compete with feed and food production. Due to the ample raw material base for gasification, which can basically be all kinds of mostly dry biomass, including waste such as municipal solid waste (MSW), syngas-derived products are highly scalable. Amongst them are bioplastics, biofuels, biobased building blocks, and single-cell protein (SCP) for feed and food. This article reviews the state-of-the-art in biomass gasification with a spotlight on gas fermentation for the sustainable production of high-volume materials. Full article

Catalyst deactivation, mainly due to coke deposition, presents a significant challenge in the process of dry reforming of methane (DRM). This study focused on coke-resistant catalysts for DRM, particularly nickel-based catalysts supported on hydroxyapatite (HAP). A novel HAP formulation (HAP_S) with a Ca/P ratio of 1.54, below the stochiometric ratio studied in previous studies, was compared with commercial HAP (HAP_C), and both were impregnated with 10 wt% nickel. The synthesis of HAP_S involved low temperature (60 °C), moderate stirring, and a pH of 11, using a custom setup. Dry-reforming reactions were conducted under severe conditions (T = 800 °C) to assess the resistivity of both supports over 120 h. Our findings indicated sustained high conversion rates, reaching 93% for CH₄ and 98% for CO₂ with HAP_S, despite an increase in gas hourly space velocity. Characterisation, including X-ray diffraction, thermogravimetric analysis, and transmission electron microscopy, revealed coke formation using HAP_C, leading to initial deactivation, in contrast with the custom support. This discrepancy may be attributed to the distinct physical and chemical properties of the catalysts, their reaction mechanisms, and the deactivation precursors. Overall, the performance of nickel-based catalysts significantly hinges on support–catalyst interactions, in addition to thermal stability. Full article

The maritime shipping sector needs to transition towards a low- or zero-emission future to align with the 1.5 °C temperature goal and the recently adopted and revised greenhouse gas (GHG) strategy at the International Maritime Organization (IMO). A significant research gap exists in understanding how socio-economic and socio-political processes can lead to the adoption of alternative marine fuels that will be essential in meeting the aforementioned goals. The aim of this paper is to use a case study of an existing transition to understand how diffusion takes place, specifically how the adoption of liquified natural gas (LNG) in Norway has unfolded and what lessons can be learnt from this process. To answer this question, a combination of semi-structured interviews with key maritime stakeholders and documentary evidence was collected covering the period from 1985 to 2015. The collected data were analysed through a content analysis approach applying the multilevel perspective (MLP) as a heuristic. The qualitative results paint an interesting picture of the changing attitudes towards LNG as a marine fuel in Norway. In the early years, the adoption of LNG was primarily driven by air pollution and political considerations of using Norwegian natural gas, which over time, evolved into a more focused maritime paradigm painted through the lens of the Norwegian maritime industry under wider regulatory developments such as emission control areas (ECAs). By the 2010s, these drivers were superseded by GHG considerations such as methane slip concerns and a less favourable natural gas market leading to a slowdown of LNG adoption. These findings provide valuable insights for understanding future adoption dynamics of alternative zero-emission fuels, particularly in relation to the role of strong technology champions, institutional modification requirements, and starting conditions for a transition. Full article

The aim of this work was to verify the possibility of forming Ni-Fe and Co-Fe alloys via topotactic ion exchange exsolution in Fe-infiltrated (La,Sr,Ce)_0.9(Ni,Ti)O_3-δ or (La,Sr,Ce)_0.9(Co,Ti)O_3-δ ceramics. For this purpose, samples were synthesized using the Pechini method and then infiltrated with an iron nitrate solution. The reduction process in dry H₂ forced the topotactic ion exchange exsolution, leading to the formation of additional round-shape structures on the surfaces of grains. EDS scans and XRD analysis confirmed the formation of bimetallic alloys, which suggests that these materials have great potential for further use as anode materials for Solid Oxide Fuel Cells (SOFCs). Full article

Dew point pressure (DPP) emerges as a pivotal factor crucial for forecasting reservoir dynamics regarding condensate-to-gas ratio and addressing production/completion hurdles, alongside calibrating EOS models for integrated simulation. However, DPP presents challenges in terms of predictability. Acknowledging these complexities, we introduce a state-of-the-art approach for DPP estimation utilizing advanced machine learning (ML) techniques. Our methodology is juxtaposed against published empirical correlation-based methods on two datasets with limited sizes and diverse inputs. With superior performance over correlation-based estimators, our ML approach demonstrates adaptability and resilience even with restricted training datasets, spanning various fluid classifications. We acquired condensate PVT data from publicly available sources and GeoMark RFDBASE, encompassing dew point pressure (the target variable), as well as compositional data (mole percentages of each component), temperature, molecular weight (MW), and specific gravity (SG) of heptane plus, which served as input variables. Before initiating the study, thorough assessments of measurement quality and results using statistical methods were conducted leveraging domain expertise. Subsequently, advanced ML techniques were employed to train predictive models with cross-validation to mitigate overfitting to the limited datasets. Our models were juxtaposed against the foremost published DDP estimators utilizing empirical correlation-based methods, with correlation-based estimators also trained on the underlying datasets for equitable comparison. To improve outcomes, pseudo-critical properties and artificial proxy features were utilized, leveraging generalized input data. Full article

This work provides an extended description of the tools developed in the Wolfram Mathematica environment to characterize proton exchange membrane (PEM) fuel cells. These tools, with their user-friendly interface, facilitate the calculation of the main parameters required to obtain the PEM fuel cell polarization curve, offering a seamless and intuitive experience. Various mathematical models and algorithms are coded to accurately calculate the parameters needed for the polarization curve analysis. This study presents the development and validation of a computational tool designed to simulate the performance of proton exchange membrane (PEM) fuel cells. The tool integrates thermodynamic and electrochemical equations to predict key operational parameters, and was validated using experimental data from a commercial Ballard^® PEM fuel cell to ensure its accuracy. The validation process involved comparing the numerical predictions with empirical measurements under various operating conditions. The results demonstrate that the computational tool accurately replicates the performance characteristics observed in the experimental data, confirming its reliability and instilling confidence in its use for simulating PEM fuel cell behavior. This tool offers a valuable resource for optimizing fuel cell design and operation, providing insights into the efficiency, output, and potential areas for improvement. Future work will expand the tool’s capabilities to include degradation mechanisms and long-term performance predictions. This advancement underscores the tool’s potential as a comprehensive solution for academic research and industrial applications in fuel cell technology. Full article

Addressing escalating energy demands and greenhouse gas emissions in the oil and gas industry has driven extensive efforts in carbon capture and utilization (CCU), focusing on power plants and industrial facilities. However, utilizing CO₂ as a raw material to produce valuable chemicals, materials, and fuels for transportation may offer a more sustainable and long-term solution than sequestration alone. This approach also presents promising alternatives to traditional chemical feedstock in industries such as fine chemicals, pharmaceuticals, and polymers. This review comprehensively outlines the current state of CO₂ capture technologies, exploring the associated challenges and opportunities regarding their efficiency and economic feasibility. Specifically, it examines the potential of technologies such as chemical looping, membrane separation, and adsorption processes, which are advancing the frontiers of CO₂ capture by enhancing efficiency and reducing costs. Additionally, it explores the various methods of CO₂ utilization, highlighting the potential benefits and applications. These methods hold potential for producing high-value chemicals and materials, offering new pathways for industries to reduce their carbon footprint. The integration of CO₂ capture and utilization is also examined, emphasizing its potential as a cost-effective and efficient approach that mitigates climate change while converting CO₂ into a valuable resource. Finally, the review outlines the challenges in designing, developing, and scaling up CO₂ capture and utilization processes, providing a comprehensive perspective on the technical and economic challenges that need to be addressed. It provides a roadmap for technologies, suggesting that their successful deployment could result in significant environmental benefits and encourage innovation in sustainable practices within the energy and chemical sectors. Full article

Climate change and the growing demand for energy have prompted research on alternative eco-friendly energy sources. This study focused on the potential for biogas production from water hyacinth and banana peel waste through physicochemical characterization and batch anaerobic digestion tests. The water hyacinth and banana peel samples were dried, ground, and subjected to elemental, proximate, and fiber content analyses. Subsequently, banana peel waste, water hyacinth stems, and leaves were used for batch anaerobic digestion tests in 500 mL glass flask bottles for 21 days under mesophilic conditions in n = 3 trials. Kruskal–Wallis and Dunnett’s tests were performed to identify the significance of the differences in biogas yield among the samples. The analyses of the elemental, proximate, and fiber contents of water hyacinth and banana peels revealed that they possess a suitable chemical composition and essential nutrients for the production of high-yield biogas. The biogas yields from water hyacinth leaves, stems, and banana peels were 280.15, 324.79, and 334.82 mL/g VS, respectively. These findings indicate that water hyacinth and banana peel waste have significant potential for biogas production. Full article