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Developing efficient and cheap electrocatalysts as substitutes for commercial Pt/C in the oxygen reduction reaction(ORR)is extremely necessary. Herein, paper mill sludge (PMS) was utilized to produce iron, nitrogen and sulfur co-doped carbon nanotube/nanoporous carbon nanocomposite (PMS-CNT/C) by pyrolysis. PMS-CNT/C-b, one of as-prepared PMS-CNT/C exhibited excellent oxygen reduction reaction activity with an onset potential of 0.99 V vs. RHE and half-wave potential of 0.77 V vs. RHE, which was similar to the commercial Pt/C catalyst (onset potential of 0.99 V vs. RHE and half-wave potential of 0.76 V vs. RHE). It had longer-term stability and higher methanol tolerance in alkaline medium than Pt/C. Moreover, the new catalyst also exhibited excellent catalytic performance in neutral solution. The energy output of microbial fuel cells loaded with PMS-CNT/C-b catalyst was also higher than that of commercial Pt/C under neutral condition. The excellent ORR performance of PMS-CNT/C-b was due to the carbon nanotube/nanoporous structure and the synergistic effect of abundant N groups, iron nitrides and thiophene-S. The formation of CNTs in the carbon nanotube/nanoporous carbon nanocomposite was mainly attributed to melamine, which was added into PMS and was at first just considered as a nitrogen source to develop N-doped PMS-based catalysis in this work. The synthesis of paper mill sludge-based carbon nanotube/nanoporous nanocomposite and its excellent ORR activity will make the new catalyst a promising cathodic electrocatalyst alternative for fuel cells. • Paper mill sludge (PMS) was utilized to fabricate Fe, N and S co-doped carbon materials. • Melamine was directly added into PMS to assist the formation of CNTs. • The PMS-based nanocomposites exhibited excellent catalytic activity for ORR. • A green and efficient strategy was developed for the reuse of PMS. [ABSTRACT FROM AUTHOR]

Composting is considered to be a natural, sustainable, and highly beneficial method for solid waste disposal. The objective of this study was to investigate the two-stage composting of green waste (GW) as affected by the addition of sugar beet pulp (SBP; at 0, 25, and 35%) and/or paper waste (PW; at 0, 5, and 10%) as bulking agents. The combination of SBP and PW greatly improved the composting conditions and the final compost quality in terms of composting temperature; pH; emissions of ammonia, nitrite nitrogen, and carbon dioxide; lignocellulose degradation; microbial abundance; enzyme activities; particle-size distribution; the ratio of water-soluble organic carbon to organic nitrogen; and phytotoxicity. The optimal two-stage composting process of GW and the highest quality compost product were obtained with the combination of 25% SBP and 10% PW. This optimal combination of bulking agents produced a mature and stable final compost product in only 20 days. [ABSTRACT FROM AUTHOR]

Paper mulberry, a fast-growing and vigorous plant, is a potential substrate for producing lignocellulosic bioethanol and an important renewable alternative to fossil fuels. In order to improve the economic feasibility of ethanol production from paper mulberry, H 3 PO 4 /H 2 O 2 pretreatment was selected as the most suitable pretreatment method that could produce the highest glucose concentration (131 g/L) compared with other pretreatments (73.2–89.3 g/L) at high solid loading. Whereafter, the final solid loading of H 3 PO 4 /H 2 O 2 pretreatment was significantly increased to 40% (w/v) without any decrease in the final glucose concentration. Finally, a novel Fed-nonisothermal-simultaneous saccharification and fermentation was constructed using H 3 PO 4 /H 2 O 2 pretreated paper mulberry, which bypassed the inhibition caused by paper mulberry solid and high temperature on the traditional simultaneous saccharification and fermentation, improving ethanol concentration (63.9 g/L), ethanol productivity (1.33 g/L/h) and ethanol yield (0.160 g/g-biomass) by 30.4%, 30.4% and 30.1%, respectively, compared to those obtained from SSF (simultaneous saccharification and fermentation) process. Thus, we have opened up a novel way to produce ethanol or other biofuels using the paper mulberry as an outstanding alternative substrate. • We are the first to produce ethanol from paper mulberry. • An extremely high solid loading (40%) was used in the pretreatment process. • A novel Fed-nonisothermal-SSF was developed, improving ethanol yield by 30.1%. [ABSTRACT FROM AUTHOR]

The valorization of paper sludge is a high-potential process to develop renewable fuels and chemicals, which can be integrated with pulp and paper mills. Calcium carbonate is the main ash component in sludge, which plays a role in buffering pH and potentially lowering the conversion during enzymatic hydrolysis. Therefore, it is important to investigate the effect of ash on sugar yields and examine pH change to introduce efficient and economical enzymatic hydrolysis of sludge. Carbohydrate conversion was enhanced when the ash was removed by fractionation. On the other hand, the highest sugar recovery was obtained when the sludge contained 20% ash content. The pH change during enzymatic hydrolysis was influenced by ash and explained why sludge-derived hydrolysate showed lower carbohydrate conversion. Therefore, a high shear process with the increased acid amount is suggested to prohibit the negative effect of ash and enhance the accessibility of cellulase to fibers. This study highlights the feasibility of using wet waste streams generated by the paper industry. • Enhanced carbohydrate conversion of sludge containing low ash after fractionation. • Enhanced carbohydrate conversion by lowering the starting pH environment. • Observed pH change during hydrolysis to understand the adverse effect of ash. • Obtained maximum sugar recovery when paper sludge contained 20% ash. • Provided the efficiency of enzymatic hydrolysis depending on the ash content. [ABSTRACT FROM AUTHOR]

Biomass is a renewable energy and had been recognized as a promising feedstock for producing bio-fuels. In this work, pyrolysis of black wattle residues was investigated with the aim to study the product distribution and their chemical composition and predicting the optimal condition for maximized bio-oil especially aromatics content by using a two level factorial design of experiment. The pyrolysis were performed at temperature of 380 – 580 o C, Under screw feeder carried the biomass residues and weight of dolomite as catalyst of 1-5 wt% inside pyrolyzer with nitrogen gases flow rate of 20 to 80 cm 3 /min The detention time was controlled by reactor screw feeder at feeding rate of 120 to 240 rpm. Based on the analysis from a design-expert program to determine the appropriated condition of experiment was 515.18 o C, 120.01 rpm of feed rate and 20.00 cm 3 /min of nitrogen flow rate using 5.00wt% of dolomite catalyst. The elemental and physicochemistry analysis of bio-oil were determined, the chemical composition also investigated using gas chromatography-mass spectrometry and 1 H NMR. The composition of bio-oil mainly oxygenated compound with high molecular weight and phenol. The results show that the biomass residual can be considered as a potential alternative fuels and relevant to valuable chemical feedstock. [ABSTRACT FROM AUTHOR]

The global cement industry produces over four billion tonnes annually. In recent years, the quest for increasing energy efficiency has led this industry to test and use “waste” materials as alternative fuels (AF). The objective of this study was to examine the use, as alternative fuel, of the shredded non-recycled plastics and paper residue (NRPP) of a materials recovery facility at the Balcones plant in San Antonio, Texas; this material has a Lower Heating Value (LHV) of about 17 MJ/kg and is called “engineered fuel” (EF). The results showed that EF consists of mostly paper fiber, a biogenic material, so its use helps to decrease CO 2 emissions from cement production. In the US, on an average about 4.3 MJ of thermal energy are used to dry, decompose, and sinter the carbonate minerals to produce one kg of “clinker” that is then ground to cement powder and mixed with other compounds. If the maximum amount of EF that can be used by the U.S. cement industry (83 million tonnes of cement per year) were to be separated at Material Recovery Facilities and used as alternative fuel in cement kilns, the diversion of non-recycled paper and plastics from landfills would amount to 17.7 million tonnes of EF. The general methodology used for the Life Cycle Assessment (LCA) is Eco-indicators 99 that uses the SimaPro database and four scenarios were assessed. The corresponding chemical structure of the EF was calculated and the associated emissions during combustion were determined. The laboratory analyses determined the average makeup of the sampled fuels consisted of 20% fossil based carbon and 80% biogenic. The use of EF in the cement industry reduces greenhouse gas emission by up to 3 tonnes of CO 2 per tonne of EF used in place of a high-quality coal. The study also found that use of EF in cement production has no adverse effect on the stack emissions of cement plants, nor on the quality of cement produced. The mercury concentration in the stack gas of U.S. cement kilns is well below the U.S. standard and the total dioxin emissions of all cement plants amount to only 0.05% of the dioxins emitted by all U.S. sources. Furthermore, the cement process incorporates the residual ash in the EF into the final clinker, thus resulting in both energy and materials recovery. [ABSTRACT FROM AUTHOR]

This work reports an innovative simulation method for effectively utilizing paper-mill sludge based on the co-gasification approach for energy-enriched renewable fuel production. An Aspen plus-based co-gasification model was developed to simulate and examine the synergetic effects of biomass and paper-mill sludge co-gasification. Initially, the model was validated using experimental data from the reported literature and found good agreement regarding gasification and co-gasification approaches. Sensitivity analysis of biomass gasification revealed that the maximum H 2 content of 29.6% and CO (36.0%), LHV (7.8 MJ/Nm3), 72.2% (CCE) was obtained at optimal (850 °C: temperature; 1 bar: pressure; 0.2: ER) conditions. Further, the H 2 proportion enhanced, and CO declined to 38.8 and 30.7% at the same operating conditions, respectively, with a co-gasification ratio of 50% compared to 0% (H 2 : 29.6% and CO: 36.0%). However, with increasing the co-gasification ratio beyond 20%, the CO content started to follow upward trends; at the same CGR, the H 2 , LHV, and CCE observed were 36.0%, 7.76 MJ/Nm3, and 65.2%, respectively. Hence, the developed co-gasification model can provide vital information for large-scale gasifier design, operating decisions, and optimization using different biomass blends. • Biomass and PMS utilization to produce renewable fuel. • Co-gasification parametric effects evaluation on product yield. • Increasing the proportion of PMS in feedstock mixture increases H 2 content. • 20% PMS co-gasification provided consistency with reported literature. [ABSTRACT FROM AUTHOR]

Under the dual pressure of energy consumption and environmental pollution, mankind hopes to develop clean and renewable alternative energy, and the rapid development of fuel cells meets people's demand for energy-efficient power systems. The emergence of portable micro energy systems represented by microfluidic fuel cells, such as paper-based microfluidic fuel cells, has greatly enriched the means of medical detection to better cope with the threat of disease transmission. In this work, the numerical simulation method is innovatively introduced to study the paper-based microfluidic fuel cells. Both transient and steady-state modes are employed to demonstrate the whole operation process of the paper-based microfluidic fuel cell. In addition, the different structural parameters, including electrode spacing, the distance between electrode and inlet, channel thickness, and electrode length, are also investigated their influence mechanisms on cell performance. Results show that the increase of most structural parameters decreases cell output power in different degrees. Even on the premise that increasing channel thickness has a positive impact on the output power, the fuel utilization still shows a downward trend. These conclusions provide theoretical support and reference for future optimization work and accelerate the development of microfluidic fuel cells. • Numerical simulation is employed to study paper-based microfluidic fuel cell. • The effects of structure parameters on cell performance are discussed. • Through fuel concentration distribution to reveal cell performance mechanism. • Fuel utilization is used to evaluate energy efficiency. [ABSTRACT FROM AUTHOR]

• SRF composition influences on melting characteristic of ashes. • Slag viscosity index Sr forecasts the influence of ash oxide composition on melting. • High concentration of calcium compounds counteracts the ash melting point reduction. • High concentration of calcium compounds prevents the melt phase formation. • The ashes of SRF rich in waste paper (CaCO 3) has high values of the melting point. Various types of solid recovered fuels (SRFs) were investigated, then the waste was chemically leached and co-fired with coal and sewage sludge. Ashes with different properties and oxide compositions were used to explain the influence of various ash components (mainly sodium, potassium and calcium) on the Ash Fusion Temperatures (AFTs). Oxide compositions and empirical indices were determined and the effect of these data on the measured AFTs was investigated. An attempt to explain the effects of specific oxides on SRF melting temperatures using FactSage thermodynamic equilibrium software is presented. Thermodynamic equilibrium calculations are also used to predict the onset temperature of the molten phase, the percentage of molten phase at different combustion temperatures, and the possible solid phases that may exist at different temperatures. The mechanism of transformation of the inorganic substance of SRF turned out to be more complex than that of the mineral substance of coal, which resulted from the variable composition of the SRF. The character of temperature changes of the studied wastes after leaching in water and acetic acid in most cases is similar to the courses determined experimentally. For all investigated ashes from obtained the leaching of SRF wastes, the melting temperature decreases with the applied leaching. Potassium and sodium are the key elements causig the formation of low-melting silicates. Depending on the type of waste and leaching agent the lower the value of the B/A and α indices and the CaO content in ash, the lower the shrinkage temperature of the ash. [ABSTRACT FROM AUTHOR]

Nowadays, hydrogen is gaining attention as one of the green energy alternatives within transition to a zero-emission economy. Increasing demand for hydrogen and its production has prompted the development of low-carbon strategies and technologies for hydrogen generation from hydrocarbons. This paper provides a thorough analysis of traditional and innovative methods for hydrogen production from fossil feedstock, reviewing the critical aspects and recent advancements in the field. The paper emphasizes the potential of in situ hydrogen generation as the most promising method, taking into account CO2 emission concerns. Additionally, this study explores the use of software packages for modeling hydrogen production, outlining their advantages and disadvantages and proposing the most favorable software for in situ hydrogen generation from hydrocarbons. Subsequent analysis sheds light on the effectiveness, economic viability, environmental impact, and future perspectives of various hydrogen production technologies. • Overview of hydrogen production technologies: conventional and innovative methods. • Key issues and best practices of the latest experimental and numerical studies. • Comparative analysis of various hydrogen production technologies and approaches. • Subsurface hydrogen generation has a great development potential. • There are methods for clean hydrogen production from hydrocarbon feedstock. [ABSTRACT FROM AUTHOR]

Shifting from fossil fuels to clean alternative fuel options such as hydrogen is an essential step in decarbonising the road freight transport sector and facilitating an efficient transition towards zero-emissions goods distribution of the future. Designing an economically viable and competitive Hydrogen Supply Chain (HSC) to support and accelerate the widespread adoption of hydrogen powered Heavy Goods Vehicles (H 2 -HGVs) is, however, significantly hindered by the lack of the infrastructure required for producing, storing, transporting and distributing the required hydrogen. This paper focuses on a bespoke design of a hydrogen supply chain and distribution network for the long-haul road freight transportation in the UK and develops an improved end-to-end and spatially-explicit optimisation tool to perform scenario analysis and provide important first-hand managerial and policy making insights. The proposed methodology improves over existing grid-based methodologies by incorporating spatially-explicit locations of Hydrogen Refuelling Stations (HRSs) and allowing further flexibility and accuracy. Another distinctive feature of the method and the analyses carried out in the paper pertains to the inclusion of bulk geographically agnostic, as well as geological underground hydrogen storage options, and reporting on significant cost saving opportunities. Finally, the curve for H 2 -HGVs penetration levels, safety stock period decisions, and the transport mode capacity against hydrogen levelized cost at pump have been generated as important policy making tools to provide decision support and insights into cost, resilience and reliability of the HSC. [ABSTRACT FROM AUTHOR]

The objective of this paper is to evaluate and assess the potential of green hydrogen (H 2) as a substitute fuel for Cameroon's road transportation system. To achieve this objective, we start by providing a status quo of Cameroon's road transport. Then, we conduct an empirical analysis on the potential of H 2 as a fuel for vehicles. Based on photovoltaic electrolysis, we estimate the amount of H 2 needed to fuel vehicles with the associated costs as well as the quantity of carbon emissions that could be reduced in the event of an energy switch over the period 2020–2035. Finally, techno-economic indicators are used to assess the cost-effectiveness of an H 2 vehicle in comparison to a petrol car. Results reveal that if a transition were to take place before 2035 the Cameroonian road transport sector would need between 1.75 MT and 2.5 MT of H 2 fuel per year. With this transition, Cameroon could reduce its emissions by around 26% (or 429 megatons of CO 2 equivalent). Hydrogen-fuelled vehicles offer the greatest potential for initiating this transition with the current level of technology. Indeed, starting from an investment cost for PV of 0.42 USD/Wp, H 2 in a hydrogen-fuelled vehicle can be cost-effective compared with petrol in an internal combustion engine with a PV efficiency of 40%. Therefore, a hydrogen fuel-based transport sector could emerge through technological and production advances. This study contributes to solving the problems related to fossil fuel availability and greenhouse gas emissions arising from the expansion of the road transport sector in Cameroon, envisaging H 2 as an alternative fuel. • The situation of Cameroon's vehicle fleet and its expansion are thoroughly examined. • The challenges of alternative fuels are discussed with highlights on car technologies. • The cost of producing H 2 with photovoltaic electrolysis is also studied in this paper. • Cameroon's road transport would need between 1.75 MT and 2.5 MT of H2 fuel per year. • An H 2 transport sector could emerge through technological and production advances. [ABSTRACT FROM AUTHOR]

The production of energy, food, water, and other utensils by fossil fuels generates pollution that causes constant climate change. To minimize and avoid this phenomenon, opting for less polluting energy production sources is increasingly necessary. Green hydrogen (H 2), a renewable and clean fuel, is analyzed in bibliometric terms in the present work, emphasizing photosynthetic H 2. The data were obtained through the journal database list in Web of Science, in which a total of 1507 was published between January 2010 to September 2022, dealing with the production of photosynthetic green hydrogen. The country with the most significant publication is China, with respectively 24.50% of the publications, and the Chinese Academy of Sciences has 60 co-authored papers, the largest in co-authorship—most papers published in the international journal of hydrogen energy, with 19.49% of the publications. The raw materials identified as emerging are cyanobacteria and microalgae, Rhodobacter capsulatus , synechocystis sp pcc6803 and Chlamydomonas reinhardtii pointed out as the microalgae of most significant interest. However, it is necessary to improve them, given the decrease in inactivity provided by the Calvin-Benson cycle. Life cycle assessment studies are needed, as well as H 2 storage. There is a need to reduce the levelized cost of H 2 production, which is around 9.65–25.22 USD/gallon. Studies also point to using cyanobacteria and microalgae to produce other biofuels (bioethanol biodiesel) and materials (supercapacitors, batteries, and polymers). [Display omitted] • Evaluation of the photosynthetic production of green hydrogen. • Analysis of 1507 papers from the Web of Science with CiteSpace, Vosviwer and Exell. • Advanced bibliometric analysis of future trends in the production of green hydrogen. • Using photosynthetic methods to produce biofuels. • Polymer production uses carbon dioxide and green hydrogen. [ABSTRACT FROM AUTHOR]

The urgent need to address greenhouse gas (GHG) emissions, particularly in relation to climate change, is driving the demand for new sustainable renewable fuels. This demand is promoting the expansion of de-carbonization efforts, which hold tremendous potential as a renewable energy source. One area of focus is the production of hydrogen (H 2), which has long been a popular subject of discussion. Currently, large quantities of H 2 are generated using conventional fossil fuels. However, the finite nature of these resources has compelled the global community to explore alternative, more environmentally friendly options like biomass. Generating H 2 on a large scale from various biomasses presents a complex challenge. Researchers have identified thermochemical (TC) and biological (BL) processes as the primary methods for converting biomass into H 2 , although other techniques exist as well. Commercializing H 2 as a fuel presents significant technological, financial, and environmental hurdles. Nevertheless, nanomaterials (NMs) have shown promise in overcoming some of the obstacles associated with H 2 production. This review focuses on the use of NMs in TC and BL processes for H 2 generation. Additionally, the paper provides a brief overview of the methods and financial considerations involved in enhancing biomass-based H 2 production. Studies indicate that the production of bio-H 2 is relatively expensive. Direct bio-photolysis costs range from $2.13 kg−1 to $7.24 kg-1, indirect bio-photolysis costs range from $1.42 kg−1 to $7.54 kg−1, fermentation costs range from $7.54 kg−1 to $7.61 kg−1, biomass pyrolysis costs range from $1.77 kg−1 to $2.05 kg−1, and gasification costs $1.42 kg−1. The paper also explores various challenges related to biomass conversion and utilization for H 2 production, aiming to better understand the feasibility of a biomass-based H 2 economy. [Display omitted] • The biological and thermochemical routes for renewable H 2 are elucidated and compared. • Biological routes basically have low H 2 production rate than thermochemical ones. • Ni and Fe are the most promising nanomaterials for H 2 production. • Economic analysis and challenges associated with both routes are explained. • Future research directions are presented based on identified literature gaps. [ABSTRACT FROM AUTHOR]

Hydrogen is seen as an ideal alternative fuel to fossil fuels because it is green and sustainable. With the increasing energy crisis, developing efficient catalysts for hydrogen production to alleviate resource depletion is urgent. As a new member in the family of two-dimensional (2D) transition metal dichalcogenides (TMDs), 2D rhenium disulfide have attracted much attention based on their unique properties. In this paper, based on the unusual structural features and excellent properties of 2D rhenium disulfide, we cite their applications in the field of electrocatalytic water splitting and provide an in-depth understanding of the reaction mechanism. Furthermore, we enumerate the various synthetic methods of 2D rhenium disulfide and summarize the different strategies and current research progress in modulating their catalytic performances. Finally, we discuss the challenges faced by 2D rhenium disulfide in terms of synthetic methods and modulation strategies, and provide insights into their possible future development directions, hoping to provide valuable guidance for the design and preparation of high-performance rhenium-based electrocatalysts in the future. [Display omitted] • The unique structure and properties of 2D rhenium disulfide are presented. • Various synthetic methods of 2D rhenium disulfide are summarized. • Strategies for improving the catalytic performances are discussed. [ABSTRACT FROM AUTHOR]

Diesel engines are commonly used due to its higher reliability and better fuel conversion efficiency. However, it produces exhaust emissions like carbon dioxide (CO 2) and particulate matter (PM). Hydrogen gas is regarded as a clean fuel as it is free from carbon. The addition of hydrogen fuel enhances the burning rates and extends the flammability limits of fossil fuels, and therefore has the potential of reduced exhaust emission in diesel engines operating on dual fuel mode. This paper has investigated the effect of hydrogen addition to the performance and emissions of a single-cylinder diesel engine, working in dual fuel mode with additive di-tert butyl peroxide (DTBP). About 25% hydrogen was introduced into the cylinder on a mass basis via the engine intake manifold with the addition of additive di-tert butyl peroxide up to 5% in diesel fuel. In this experimental study, mean gas temperature, indicated mean effective pressure (IMEP), brake mean effective pressure (BMEP), polytropic index, and exhaust emissions were studied at medium (53%) and high (69%) load conditions. The indicated mean effective and brake mean effective pressure was 9.79 bar with a 3% addition of additive and 4.15 bar with the 5% addition of additive as compared with 8.71 bar and 4.11 bar diesel fuel operation. 16% hydrogen addition with 1% di-tert butyl peroxide, IMEP, and BMEP are 10.92 bar, and 4.14 bar respectively. • Additive with hydrogen fuel work as alternative fuel in diesel engine. • Effect of temperature and pressure with additive (1%–5%) and diesel fuel. • At 53% load, the reduction in polytropic index with additive from 3% to 5%. • At 69% load, enhanced in polytropic index from 1% to 5% additive. • Indicated mean effective pressure and brake mean effective pressure enhanced. [ABSTRACT FROM AUTHOR]

To limit the negative impact on the environment, increasingly stringent regulations are being introduced regarding the reduction of pollutant emissions. In automotive applications, reciprocating internal combustion engines (ICE) are under immense pressure due to emissions. Society aims to move away from fossil fuels. However, it is acknowledged that ICE will continue to play a significant role in electricity generation systems and certain transportation sectors. To achieve zero emissions or drastically reduce emissions, alternative carbon-free fuels are being pursued. Hydrogen (H 2) is a natural substitute for fossil fuels, and recently, ammonia (NH 3) has been considered an intriguing fuel. Ammonia is easier to transport and store compared to hydrogen. NH 3 is a good hydrogen carrier with significant potential for use in ICE. However, ammonia combustion in such applications exhibits challenges related to its low burning rate. Here, hydrogen emerges as a high reactivity fuel, used as a combustion enhancer for NH 3. Hydrogen-assisted ammonia combustion shows great promise for future of ICE. This paper presents a summary of research findings on the NH 3 /H 2 combustion process in a spark-ignition ICE. Concepts of dual-fuel NH 3 /H 2 engine operation, the influence of fuel proportions on cylinder pressure profiles, heat release, combustion stages, and engine emissions aspects are discussed. The directions of development of SI piston engines powered by NH 3 /H 2 are given. • Assessment of NH 3 and NH 3 /H 2 combustion strategies in the SI engine • Direct injection of ammonia reduces its content in exhaust gases. • SI engine powered by NH 3 requires high ignition energy. • The challenge is to reduce N 2 O emissions. • Hydrogen expands the spectrum of application of NH 3 as a fuel for the SI engine. [ABSTRACT FROM AUTHOR]

A current topic that has surfaced among Public Transport Companies (PTCs) is the selection of alternative fuels for their bus fleets. Both European and Italian regulations are pushing toward abandoning diesel fuel and the consolidation of alternative traction power sources, such as battery-electric vehicles, fuel-cell electric vehicles, and hydrogen-electric vehicles. The literature has provided some approaches toward assessing this selection such as multicriteria-decision-methods in some countries in the world. However, not enough specific attention has been paid to cost criteria, experts involved, and the type of service required. This paper intends to address these gaps by applying an integrated method, which includes: (i) the Analytical Hierarchy Process (AHP) to define the weights of criteria; (ii) the ELimination Et Choix Traduisant la REalitè I (ELECTRE I) to find a good compromise solution among the fuel alternatives and (iii) a simple Weighted Sum Model (WSM) to refine ranking. This integrated method was applied in Italy involving a panel of experts from whom the data was collected. Different fuel alternatives for both urban and interurban services and with and without funding are discussed. The results provide a useful tool supporting PTC policies, which aims to rationalise and prioritise bus fuel alternatives when deciding on fleet renewal. • Bus fuel selection studies lack cost criteria, experts involved, and service type. • The multicriteria-decision-methods (MCDM) considers the previous issues. • An integrated MCDM method selects fuel alternatives for urban/interurban bus services. • Results prioritise the economically advantageous fuels for with and without funding. [ABSTRACT FROM AUTHOR]

Nowadays, the increasing consumption of conventional fuels has led to rising pollutant emissions, among which soot has received much attention due to its harmful effects. In this paper, previous typical soot models are reviewed. Based on empirical, semi-empirical and detailed models, phenomenological models, the most popular models of recent years, are also summarized. This work also summarizes the application of existing soot models in combination with other models and methods in turbulent flame and diesel engine development based on existing models. Besides, as the development of clean alternative fuels continues, new fuels have received significant attention as a method to reduce soot formation. For different fuels, the reasons for reducing soot formation have also attracted the interest of researchers, and thus this paper reviews the current research about relevant carbon soot modeling for biodiesel, natural gas, and other new fuels. A detailed understanding of soot generation and soot modelling can help further research into methods to reduce soot emissions. [Display omitted] [ABSTRACT FROM AUTHOR]

Hydrogen can be a capable alternative to fossil fuels due to its carbon-free characteristics, in this content, biological hydrogen production is considered a practical approach because technology is green. Due to parameters affecting biohydrogen production, such as operating conditions, it is crucial to predict the process to see the proper yield. There are several conventional and unconventional models used in biohydrogen production prediction. This paper derived a triple first-order prediction model from a previously presented multi-scale kinetic model polynomial built upon the multi-stage growth hypothesis for bio-hydrogen production prediction. The original model was applied to batch and continuous stirred tank reactor studies for their model evaluation, this study evaluated the newly derived model for studies of membrane bioreactors. Due to their increased production yield, membrane bioreactors are an emerging field in biohydrogen production. Although the previous study was mainly applied for batch dark fermentations consisting of various microorganisms, the results presented in this study indicate that it is also applicable for continuous and photo fermentation systems. The original model results reported significant fitness accuracy among different datasheets compared to conventional models like the modified Gompertz model, considering essential factors impacting biohydrogen production suggested in the original model, this paper investigated eleven case studies of dynamic membrane bioreactors with modeling fitness of 99% for most cases. This study reports even higher fitness accuracy compared to the original model, even with different operating conditions. • Investigating biohydrogen production rate of membrane bioreactors (MBR). • A multi-scale kinetic model based on multi-stage growth hypothesis for MBRs. • Providing excellent data fitting for dark/photo fermentations in MBRs. • A flexible black-box data driven model proper for a range of processes. [ABSTRACT FROM AUTHOR]

This paper presents detailed investigations of the combustion characteristics of NH 3 /H 2 blends as a possible alternative fuel to address the pressing environmental and energy security challenges. The experimental measurements of laminar burning velocity (LBV) are reported for a range of mixture equivalence ratios (φ) varied from 0.8 to 1.2 and mixture temperatures up to 720 K using the externally heated diverging channel (EHDC) method. It is observed that LBV increases nearly four times for specific NH 3 /H 2 blends with an increase in mixture temperature from 300 K to 650 K. While predictions from various kinetic models align well at ambient conditions, discrepancies emerge at higher temperatures, emphasizing the need for refining these models to accurately predict flame propagation behaviour. A detailed sensitivity analysis of the NH 3 /H 2 /air fuel blend provides insights into critical reactions and species influencing burning velocity across different mixture conditions. Notably, reactions involving NNH radicals are found to strongly influence LBV for low hydrogen fractions in NH 3. Additionally, reaction pathway analysis (RPA) highlights dominant reactions under various conditions and reveals temperature-dependent NO emissions. The present study helps highlight the importance of understanding the combustion behaviour of NH 3 /H 2 blends for achieving carbon-free energy needs. The experimental data at elevated temperatures offers valuable insights into the combustion behaviour of these mixtures, enabling the advancements for cleaner energy solutions. [Display omitted] • LBV for X H2 = 0.3 increased fourfold from 300 K to 650 K. • Predicted LBVs aligned with low-temperature data but differed at higher temperatures. • Burning velocity rises with H 2 addition due to increased H, O, and OH species. • The significance of critical NNH radical reactions increased with H 2 addition. • Higher hydrogen fractions introduce NH + H N + H 2 resulting in Zeldovich mechanism. [ABSTRACT FROM AUTHOR]

• Biomethanol production from biomass gasification represents a circular economy approach for chemicals production. • Advanced configurations based on membranes for obtaining cleaning syngas from biomass are discussed. • The implementation of microchannels reaction technology is proposed to enhance the chemical engineering aspects of biomethanol production. • The production of biomethanol has an important socio-ecomnomic impact. The Intergovernmental Panel on Climate Change (IPCC) recognises the pivotal role of renewable energies in the future energy system and the achievement of the zero-emission target. The implementation of renewables should provide major opportunities and enable a more secure and decentralised energy supply system. Renewable fuels provide long-term solutions for the transport sector, particularly for applications where fuels with high energy density are required. In addition, it helps reducing the carbon footprint of these sectors in the long-term. Information on biomass characteristics feedstock is essential for scaling-up gasification from the laboratory to industrial-scale. This review deals with the transformation biogenic residues into a valuable bioenergy carrier like biomethanol as the liquid sunshine based on the combination of modified mature technologies such as gasification with other innovative solutions such as membranes and microchannel reactors. Tar abatement is a critical process in product gas upgrading since tars compromise downstream processes and equipment, for this, membrane technology for upgrading syngas quality is discussed in this paper. Microchannel reactor technology with the design of state-of-the-art multifunctional catalysts provides a path to develop decentralised biomethanol synthesis from biogenic residues. Finally, the development of a process chain for the production of (i) methanol as an intermediate energy carrier, (ii) electricity and (iii) heat for decentralised applications based on biomass feedstock flexible gasification, gas upgrading and methanol synthesis is analysed. [Display omitted] [ABSTRACT FROM AUTHOR]

The paper evaluates all important aspects related to V present in coal and its behaviour during coal combustion with particular attention paid to its potential extraction from ash and slag wastes. Due to great environmental benefits of co-combustion of coal and wastes, these alternative fuels and corresponding ash and slag counterparts were also taken into evaluation. Specifically, the paper summarizes V levels in world coals, in other related materials (alternative fuels, additives etc.) and in ash and slag residues including V speciation and discussion of its valence states. Theoretically predicted (equilibrium-based) calculations and species are compared with experimental results; due to a significant effect on mitigating CO 2 emissions, attention is paid also to oxy-fuel combustion conditions. With the aim to extract V out of the ash and slag residues, physical, chemical, and biotechnological separation methods are discussed in detail along with dominant affecting factors. The paper includes also concluding remarks and highlights the most promising trends and limitations thereby providing suggestions for future research. [Display omitted] [ABSTRACT FROM AUTHOR]

The hydrogen carrier ammonia is considered a prominent carbon-free alternative fuel. This paper examines the impact of flue gas recirculation (FR) on combustion instability and emission behavior of premixed CH 4 /NH 3 /air swirl flame at different equivalence ratios (Φ) and ammonia mole fractions (χ NH 3 ). Experimental results show that FR is beneficial to suppressing the self-excited pulsating pressure and pulsating heat release rate of CH 4 /NH 3 /air flame, and the pulsating frequency decreases monotonically with the increase of FR. Under fuel-lean and stoichiometric conditions, FR is beneficial to suppressing NOx formation but will increase CO and NH 3 emissions. Under fuel-rich conditions, FR reduces CO emissions but increases NOx emissions. The NO emissions obtained from the chemical reactor network simulation are in qualitative agreement with the experimental results. The results show that the elementary reactions related to HNO and NHi radicals play a crucial role in the influence of FR on NO formation. • Flue gas recirculation (FR) suppresses combustion instability of CH 4 /NH 3 /air flame. • FR decreases NOx emission but increases CO emission under non-rich conditions. • FR increases NOx emission but decreases CO emission under fuel-rich conditions. • Chemical reactor network reveals the main reactions of FR affecting NO formation. [ABSTRACT FROM AUTHOR]

The increasing concern about environmental degradation and an energy crisis due to geopolitical conflicts, economic sanctions, and worsened energy security has prompted energy researchers to find environmentally friendly and renewable sources as an alternative to fossil fuel sources. Hydrogen is one of the most suitable replacements for fossil fuels due to its good thermal properties, wide applicability, multiple sources, and being carbon-free. Hydrogen can be produced sustainably from different biomass sources through biological and thermochemical pathways. This manuscript aims to present a comprehensive analysis of current approaches for producing hydrogen from biomass sources, elucidating recent advancements in this domain. The manuscript outlines the benefits and drawbacks of different approaches. Furthermore, a thorough bibliometric analysis using VOSviewer software was carried out for the years 2000–2023, covering 1840 relevant references. The incorporation of an extensive bibliometric analysis enhances the scholarly depth of the research. Through the mapping of historical and contemporary research emphases, significant contributors, and emerging trends, the paper provides a precise visual depiction of the research landscape. This not only contributes to a nuanced comprehension of the field's present condition but also functions as a valuable instrument for researchers in strategizing future studies. [Display omitted] • Biological and Thermochemical Pathways for H 2 production were reviewed and summarized. • Advantages and disadvantages of the common methods were clarified. • Bibliometric study unveils H 2 production from sustainable resources literature trends, research status, and future potential. [ABSTRACT FROM AUTHOR]

Hydrogen stands out as a compelling alternative to fossil fuels for combustion engines. Predictive combustion models are instrumental in developing hydrogen-fuelled engines. A fundamental metric of these models is the laminar burning velocity (LBV), which can be precisely determined through laminar flame propagation simulations. In this context, the selection of an appropriate combustion mechanism is critical. This paper aims to propose the appropriate combustion mechanism for calculating LBV in predictive combustion models of hydrogen-fuelled engines. 15 state-of-the-art combustion mechanisms were applied to reproduce the LBV measurements in engine-like conditions, especially considering the application of lean combustion and water injection. The FFCM 1.0 mechanism was identified from them and further optimised to improve its prediction accuracy at elevated pressures for the lean mixture. The maximum deviation of LBV was reduced from 17.6 % to 8.7 % by this optimisation, in comparison to 10.5 % for its closest competitor mechanism, ELTE (Varga et al., 2015). • 15 combustion mechanisms were selected as the candidates for optimisation. • Test cases consider applications of lean combustion and water injection. • Many mechanisms predict laminar burning velocities at elevated pressure inadequately. • FFCM 1.0 mechanism was optimised to a new mechanism for modelling H2-fuelled engines. • Prediction errors of laminar burning velocity by the new mechanism are within 8.7 %. [ABSTRACT FROM AUTHOR]

Achieving net-zero emissions in the maritime sector requires adopting carbon-neutral practices in terms of shipbuilding, operation and recycling. However, research integrating life cycle and energy analysis is missing to inform decision-makers. Consequently, the paper presents models combining a model-based life cycle assessment (MBLCA) and ship energy simulations to examine the footprints of a generic New Panamax Containership (DTC). Analyses were conducted to assess the energy and carbon effects of using synthetic methanol as marine fuel. The life-cycle analysis confirms the overwhelming prevalence of operations in the total greenhouse gases emission during the ship's lifetime. The analysis highlights the potential of carbon savings if the vessel consumes methanol produced from neutral energy and renewable carbon sources. However, the magnitude of shipping fuel requirements may profoundly impact energy infrastructures while still requiring large volumes of carbon offset credits. The paper confirms the usefulness of integrating life-cycle analysis and energy modelling to discuss future energy scenarios. The completeness of the models also allows for future research analysing other energy solutions. • The paper assesses GWP100, energy intensity, and renewable carbon needs of a New-Panamax vessel using heavy fuel oil or carbon-neutral methanol. • The methodology integrates a novel energy modelling tool into ISO life cycle analysis for maritime decarbonation research. • Findings indicate that operational energy consumption accounts for 60%–98% of the vessel's total carbon footprint. • Results reveal that 80% of the shipbuilding carbon footprint is attributable to the production of steel and main machinery. • The authors underscore the importance of cradle-to-grave approaches, accounting for externalities in fuel substitution strategies supporting decarbonation. [ABSTRACT FROM AUTHOR]

Large ships are more utilized than ever before to facilitate transporting heavy goods and oils overseas. However, they rely on fossil fuels and cause severe environmental impacts. Utilizing alternative fuels and implementing new engine designs are considered promising methods to reduce greenhouse gas emissions and improve engine performance. This paper compares three developed, hybridized marine engines operated using five fuel blends of hydrogen, methanol, dimethyl ether, ethanol, and methane. In addition, the paper presents a multi-objective particle swarm optimization to increase the engine power and its exergetic efficiency and reduce the cost and environmental impact. A marine engine (SRC-GT-SOFC) containing a steam Rankine cycle, a gas turbine, and a solid oxide fuel cell is considered to weigh less and perform better. It is found that the optimized SRC-GT-SOFC engine power is increased by about 10 %, corresponding to 16269 kW with an increased exergetic efficiency of 70.6 %, respectively. Its specific fuel and product exergetic costs are found to be 12 $/GJ and 15.67 $/GJ, and its specific fuel and product environmental impacts are 7.4 Pt/GJ and 9.3 Pt/GJ, respectively. This results in a significant reduction in the relative cost difference and the relative environmental impact difference of the optimized SRC-GT-SOFC of 30 % and 25.4 %, respectively. • Three hybridized marine engines are compared and optimized to raise performance. • Optimized SRC-GT-SOFC engine has 16.3 MW power and 70.6 % exergetic efficiency. • Specific exergetic cost reduced to 12 $/GJ for fuel and 16 $/GJ for product. • Specific exergetic environmental impact for fuel and product becomes 7.4 and 9.3 Pt/GJ. • New operation conditions of SRC-GT-SOFC have low price and environmental impact. [ABSTRACT FROM AUTHOR]

In the modern world, zero-carbon society has become a new buzzword of the era. Many projects have been initiated to develop alternatives not only to the environmental crisis but also to the shortage of fossil fuels. With successful projects in automobile technology, hydrogen fuel is now being tested and utilized as a sustainable green fuel in the aviation sector which will lead to zero carbon emission in the future. From the mid-20th century to the early 21st numerous countries and companies have funded multimillion projects to develop hydrogen-fueled aircraft. Empirical data show positive results for various projects. Consequently, large companies are investing in various innovations undertaken by researchers under their supervision. Over time, the efficiency of hydrogen-fueled aircraft has improved but the lack of refueling stations, large production cost, and consolidated carbon market share have impeded the path of hydrogen fuel being commercialized. In addition, the Unmanned Aerial Vehicle (UAV) is another important element of the Aviation industry, Hydrogen started to be commonly used as an alternative fuel for heavy-duty drones using fuel cell technology. The purpose of this paper is to provide an overview of the chronological development of hydrogen-powered aircraft technology and potential aviation applications for hydrogen and fuel cell technology. Furthermore, the major barriers to widespread adoption of hydrogen technology in aviation are identified, as are future research opportunities. [Display omitted] • Hydrogen is extensively researched and acknowledged as a viable mainstream fuel option. • Hydrogen fuel is now being tested and utilized as a sustainable green fuel in the aviation sector. • Numerous countries and companies have funded multimillion projects to develop hydrogen-fueled aircraft. • Empirical data show positive results for various projects. • New engine modules have been designed to accommodate hydrogen fuel cells economically. [ABSTRACT FROM AUTHOR]

Green hydrogen, proposed as a sustainable alternative for conventional fuels, has gained utmost importance due to its reduced carbon footprint and potential application in maintaining balance between energy generation and demand. Utilization of hydrogen-based systems are challenged by cost effective storage methods. Bio-hydrogen storage technologies using cryogenic and adsorptive methods are discussed in this review paper, along with their operating conditions and storage capacities. An analysis of operational challenges and recent advancements in hydrogen storage techniques is presented. With a storage pressure of 70 MP, cryogenic hydrogen is almost twice as dense as compressed hydrogen. Technical challenges such as material cost and explosion risk can be addressed by hydrogen adsorption on activated carbon active sites. Maximum hydrogen storage capacity are reported by activated carbon obtained from Chitosan (6.77 wt%), Bamboo (6.6 wt%) and African palm shell (6.5 wt%) at 77 K and 4–20 Mpa. Further, nanotechnology approaches are presented in detail for increasing hydrogen storage capacity in pristine Si and Mg. The future perspectives in terms of technological, and economic aspects are discussed. • Detailed review on hydrogen storage methods is presented. • Role of cryogenics and adsorptive media are discussed. • The comparative performance of various methods is tabulated. • Existing research gap and future perspectives are analyzed. [ABSTRACT FROM AUTHOR]

Variable Renewable Energy Sources are crucial for decarbonizing industries and efficient energy storage. Hydrogen storage technologies are limited in their large-scale capabilities. PtL technology can synthesize alternative fuels like methanol, which can be used in existing energy infrastructures to produce liquid fuel. The paper presents an innovative approach for utilizing in-situ thermal energy, using a hot reservoir rock (HRR) system for methanol synthesis at high temperature and pressure in an underground large-scale natural reservoir reactor. This approach aims to integrate renewable energy technologies into a single energy generation and fuel production system, including the direct utilization of renewable sources. Solutions from the oil and gas industry can be adapted to this action, such as continuous injection, alternate injection, separate injection, or chemical flooding. Conventional geothermal reservoirs, HDR systems, and depleted hydrocarbon reservoirs can be used as "underground reactors". However, it was also noted that there are challenges, such as catalyst distribution and the complexity of reservoir pore space. • Reservoir rock as a geochemical reactor for underground in-situ e-methanol synthesis. • Synergy between energy storage, CCUS, e-methanol production, and geothermal energy. • Effective use of surplus renewable energy with hydrogen technologies. • Risk reduction related to chemical processing and high environmental neutrality. • Use of resources related to the oil and gas industry for the energy transition. [ABSTRACT FROM AUTHOR]

The increasing demand for green hydrogen and power production necessitates the development of novel and upgraded power generation technologies. The solid oxide fuel cell combined heat and power (SOFC–CHP) system is a promising solution due to its high efficiency, clean operation, and fuel flexibility. In practical terms, SOFCs can operate using a variety of fuels such as alcoholic fuel, hydrogen, ammonia, etc. Recently, methanol and ammonia have become noteworthy alternative fuel options as it possesses advantages such as low transportation cost and high hydrogen storage capacity. In this paper, we have established two SOFC–CHP models fueled by methanol or ammonia integrated with the steam Rankine cycle. A comprehensive thermodynamic model is proposed for energy and exergy analyses. Sensitivity analysis is performed to study the system's characteristics. The results show that the SOFC–CHP system fueled by ammonia exhibits superior performance, the maximum electrical power, efficiency, and exergy efficiency is 430W, 7% and 10% greater than the methanol fueled system. The operating temperature is about 30K higher in methanol supplied system. The largest thermal power difference can reach 0.65 kW. Overall, the ammonia fueled SOFC–CHP system shows greater potential than that fueled by methanol. [Display omitted] • Using ammonia as fuel can improve energy and exergy efficiency by 7% and 10%. • Methanol fueled system requires almost half fuel than that supplied by ammonia. • The operating temperature is about 30K higher in methanol supplied system. • The largest thermal power difference can reach 0.65 kW. • The exergy destruction of preheat process accounts for the majority of both systems. [ABSTRACT FROM AUTHOR]

Owing to contamination of air and environmental hazards, the demand for sustainable fuels in power plants and other heat engines has climbed undeniably. Aluminum metal is classified among high energy density and low carbon content, which can be reacted with water and repeatedly released a large amount of heat and hydrogen. Since hydrogen is one of the zero-carbon and clean fuels, aluminum can be exploited as a promising energy-carrying and renewable source of energy. This paper is dedicated to the customization of two novel schemes of the combined cycle of power generation systems. The main components of the proposed integrated installations include a hydrogen turbine, gas turbine, multi pressure steam turbines, condenser, heat recovery steam generator and aluminum-water reactor, in which pressurized water absorbs produced heat of the reactor then superheated steam expands in steam turbines. Direct supplied hydrogen, which is generated from the Al-water reaction, expands in the hydrogen turbine and subsequently burns in the combustion chamber of the gas turbine. Hydrogen properties, consumed heat of reactor, generated powers, effects of streams pressure, energetic and exergetic productivity variation of both schemes were evaluated comparatively to ensure the best system performance along with the high net efficiency. According to the numerical analysis of the thermodynamic characteristics in steady state regime using EES software, the energy and energy efficiencies of scheme A were calculated to be 40.72% and 38.36%, besides in scheme B were 39.6% and 37.3%, respectively. [Display omitted] • Demands for environmentally friendly fuels have been raised exponentially. • Aluminum water reaction can release repeatedly heat and hydrogen. • Hydrogen as zero-carbon fuel burns in combustion chamber. • Stream of steam can absorb produced heat in Al-water reaction. • Performance of reheat cycle is better than cycle without reheat. [ABSTRACT FROM AUTHOR]

Hydrogen fuel has shown promise as a clean, alternative fuel aiding in the reduction of fossil fuel dependence within the transportation sector. However, hydrogen refueling stations and infrastructure remains a barrier and are a prerequisite for consumer adoption of low-cost and low-emission fuel cell electric vehicles (FCEVs). The costs for FCEV fueling include both station capital costs and operation and maintenance (O&M) costs. Contributing to these O&M costs, unscheduled maintenance is presently more costly and more frequent than for similar gasoline fueling infrastructure and is asserted to be a limiting factor in achieving FCEV customer acceptance and cost parity. Unscheduled maintenance leads to longer station downtime, therefore, causing an increase in missed fueling opportunities, which forces customers to seek refueling at other operable stations that may be significantly farther away. This research proposes a framework for a hydrogen station prognostics health monitoring (H2S PHM) model that can minimize unexpected downtime by predicting the remaining useful life for primary hydrogen station components within the major station subsystems. The H2S PHM model is a data-driven statistical model, based on O&M data collected from 34 retail hydrogen stations located in the U.S. The primary subcomponents studied are the dispenser, compressor, and chiller. The remaining useful life calculations are used to decide whether or not maintenance should be completed based on the prediction and expected future station use. This paper presents the background, method, and results for the H2S PHM model as for a means for improving station availability and customer confidence in FCEVs and hydrogen infrastructure. • Hydrogen station reliability is a key contributor to market success. • Mean fills between failure and station availability are lower than conventional technologies. • A prognostics health monitoring system can improve hydrogen station availability. • Estimated remaining useful life of primary components assists in maintenance decisions. [ABSTRACT FROM AUTHOR]

Climate change and the energy crisis urge the transition from fossil to renewable fuels. Ammonia and hydrogen are the most versatile carbon-free chemical energy carriers. Hydrogen-diluted ammonia combustion can drastically lower the emission of nitrogen oxides. The present paper focuses on the numerical analysis of ammonia/hydrogen combustion in a lean-premixed swirl burner, highlighting the effect of hydrogen share and equivalence ratio. The hydrogen share notably influences the axial position of the heat release maximum due to the higher reactivity, while it marginally influences the global velocity field. Unburned ammonia was observed at lean condition and low hydrogen concentration. At ultra-lean conditions, nitrogen oxide emission increases with hydrogen content, while a maximum can be reached by increasing the equivalence ratio. The values are compared to experimental data from the literature. Dinitrogen oxide emission decreases with both hydrogen concentration and equivalence ratio. Non-reacting flow field was validated by Particle Image Velocimetry measurements. [Display omitted] • H 2 /NH 3 flames were modeled by k-ω SST turbulence and EDC models. • The heat release pattern was influenced by the H 2 share. • A maximum in NO emission was observed for richer mixtures by increasing H 2. • A compromise should be made between NO and N 2 O emissions. • The numerical results were validated by PIV for non-reacting airflow. [ABSTRACT FROM AUTHOR]

This paper reports the performance of a molten carbonate fuel cell (MCFC) fed directly with liquid fuels referenced against results with hydrogen fuel in experiments conducted by the research team. Alcohols have greater energy density than pure hydrogen in normal conditions and, if presented as biofuels, the MCFC can be deemed a renewable energy source. For evaluation purposes various alcohols occurring in standard conditions in the liquid state were used for electricity generation in the MCFC: methanol, ethanol, propanol, butanol and glycerol. Since these alcohols can be subjected to steam reforming when mixed with water in specific ratios, they can be delivered directly in the liquid state to the fuel cell, where hydrogen is released and used to produce electricity and heat. The alcohols were mixed with water in ratios of 1:2, 1:3, 1:4. The results were compared to the MCFC fed with pure hydrogen as a fuel. In terms of power referenced to hydrogen (100%), the maximums achieved were 78% for butanol, 80% for glycerol, 83% for propanol, 86% for ethanol and 93% for methanol in comparison to the same amount of hydrogen delivered to the fuel cell in ideal steam reforming situation. Threats such as carbon deposition on the fuel cell surface were also evaluated. • MCFC fed directly with various mixtures of alcohols and water have been studied. • The steam reforming of mixtures of alcohols and water generates energy. • Temperature and anode material provide the necessary conditions for steam reforming. • Maximum power compared to hydrogen fuel for various fuels ranges between 78 and 93%. • Carbon deposition in the anode channel of commercial units can be a problem. [ABSTRACT FROM AUTHOR]

Energy plays a crucial role in human life as it is necessary for survival and enables us to perform daily activities. The passage of time has driven progress, with various tools, machines, and devices created to facilitate human affairs. Everything is very dependent on Energy. Unfortunately, the prevalent reliance on fossil fuels as the primary energy source has resulted in an environmental disparity attributed to greenhouse gas emissions. Besides, the depletion of fossil fuel reserves is a long-term concern for nations involved in fossil fuel production including Malaysia, which necessitates a delicate equilibrium between escalating energy demands and escalating pollution levels. This review paper aims to highlight the potential of renewable energy based on green hydrogen in Malaysia. The energy scenario in Malaysia has been reviewed by discussing energy demand, current population, energy policy synopsis, conventional energy sources, carbon emissions, and the direction of renewable energy in Malaysia. Besides, the conceptual framework for hydrogen as renewable energy was discussed covering the hydrogen economy, production technology, storage, and energy production using green hydrogen. Finally, potential applications for using hydrogen energy have been presented so that the future direction of using this alternative energy can be well planned in Malaysia. •An overview of hydrogen energy as Malaysian alternative energy is comprehensively discussed. •The hydrogen energy prospects are described in detail such as hydrogen economy, production, and consumption. •The progress of hydrogen energy implementation in Malaysia is studied towards embarking on this effort. [ABSTRACT FROM AUTHOR]

Biomass is a renewable and clean energy source, offering the potential to reduce fossil fuel consumption and greenhouse gas emissions when it is used as a biofuel. However, the disadvantages of raw biomass such as poor grindability, high moisture content, and low calorific value hinder its widespread industrial combustion. Thermochemical conversion techniques are widely used to convert biomass to biochar, which serves not only as an adsorbent and soil amendment but also as solid fuels alternative to fossil energy. The upgraded biochar exhibits better physicochemical properties and improved combustion performance. This paper focuses on the properties and combustion behavior of biochar as a solid fuel, reviewing common production techniques of biochar and their effects on yields and properties of biochar. It also examines the combustion characteristics and kinetics of biochar in single- and co-combustion scenarios with other fuels, such as coal, sludge, and petroleum coke, analyzing the influencing factors of combustion behavior and kinetic parameters. This study further investigates the emission characteristics during the combustion of biochar, including gaseous pollutants (such as CO, NO x , SO x , and HCl), ash-related issues, and particulate matter (PM) emissions. Additionally, a new fuel type named "bioslurry", which is developed with biochar as a main material, is introduced. Furthermore, this paper discusses the techno-economic and environmental aspects of biochar application, exploring the feasibility of its industrial production and utilization. • The thermochemical pretreatment methods of biomass to produce biochar are summarized. • Combustion behavior and kinetics during single- and co-firing of biochar are reviewed. • The pollutant emission characteristics during biochar combustion are investigated. • The techno-economic and environmental evaluation during biochar combustion are given. [ABSTRACT FROM AUTHOR]

Hydrogen Direct Reduction of Iron (HDRI) combined with renewable electricity is an attractive option for low-carbon steel production. In this paper, we present a novel and computationally efficient techno-economic power-to-x-plant optimization model which is then applied to an HDRI plant located in Finland. Plant dimensioning was carried out in several current and future power market and regulatory scenarios. We predict a production cost of 373 €/t for hot briquetted iron, and 351 €/t for a future scenario of 2025–2030. When the recently introduced EU rules for renewable fuels of non-biological origin are applied, the production costs increased by 30–46 €/t. The rules also have a significant increasing effect on the required hydrogen storage. The flexibility of the direct reduction shaft emerged as an important parameter affecting the required hydrogen storage as well as total production cost. The results of this paper hold significance for the optimal design of future low-carbon steel plants. • Computationally efficient optimization model for Power-to-X operations and dimensions. • Hydrogen Direct Reduction Ironmaking (HDRI) plant using wholesales and wind power. • Significant amounts of intermittent wind power can be absorbed by the HDRI plant. • HDRI/HBI production costs analyzed for EU regulatory scenarios on green hydrogen. • Emission reductions over 96% compared to CO 2 emissions of fossil steelmaking. [ABSTRACT FROM AUTHOR]

The depletion of fossil fuels and the increasing environmental problems, make biomass energy a serious alternative resource of energy. Biomass gasification is one of the major biomass utilization technologies to produce high quality gas. In this paper, biomass gasification was performed in a self-designed fluidized bed. The main factors (equivalence ratio, bed temperature, added catalyst, steam) influenced the gasification process were studied in detail. The results showed that the combustible gas content and the heating value increased with the increase of the temperature, while the CO 2 content decreased. The combustible gas content decreased with the increase of the equivalence ratio (ER), but CO 2 content increased. At the same temperature and at different ratios of CaO (from 0 to 20%), H 2 content was increased significantly, CO content was also increased, CH 4 content increased slightly, but CO 2 content was decreased. With the addition of steam at different temperature, the gas in combustible components increased, the content of H 2 increased obviously. The growth rate was 50% increased. As the bed temperature increased, gas reforming reaction increased, the CO and CH 4 content decreased, but CO 2 and H 2 content increased. • The main factors influenced the gasification process were studied in detail. • The results showed that the combustible gas content and the heating value increased with the increase of the temperature. • The combustible gas content decreased with the increase of the equivalence ratio. • With the addition of steam at different temperature, the gas in combustible components increased. [ABSTRACT FROM AUTHOR]

Recently, ammonia has been explored as a potential fuel for internal combustion engines, gas turbines and other industrial purposes. Ammonia consists of 17.6% by weight of hydrogen and is thus considered a carbon-free emission fuel. The synthesis of ammonia for bulk production takes place using the Haber-Bosch process. The production, storage and transportation of ammonia is relatively safe. This paper reports various aspects of ammonia as an alternative fuel for combustors. Several studies reporting the laminar burning velocity of ammonia and its blends are discussed. Recent advances in the development of chemical kinetics for ammonia combustion are presented. The paper explores all experimental and numerical works on ammonia as a fuel for I C engines, gas turbines and other combustion systems.This review further suggests ways to overcome the disadvantages associated with ammonia combustion, such as lower burning velocities and high NOx emissions. • A comprehensive study on the ammonia-fuelled combustion systems are carried out. • Different ammonia methods are compared and analyzed. • Breakthrough studies of the ammonia combustion are qualitatively, quantitatively discussed. • Discussions around methods to reduce NOx emissions from ammonia combustion. • Fundamentals of ammonia combustion have been critically analyzed and presented. [ABSTRACT FROM AUTHOR]

This paper presents an alternative well-balanced and energy stable method for the system of non-homogeneous Shallow Water Equations (SWE) on unstructured grids based on the residual distribution (RD) approach. The motivation of the work is based on the grid insensitivity of RD method. The newly proposed method has a positive first order part, a linearity-preserving second order scheme as well as a limited scheme which works for both steady and unsteady problems using simple, explicit time integration techniques. Numerical results herein confirm the accuracy and efficacy of the new methods in preserving both energy stability and well-balancedness. [ABSTRACT FROM AUTHOR]

Alternative energy carriers such as hydrogen and ammonia play an important role for the energy transition to reduce global CO 2 emissions substantially. These substances will be produced and used in much larger amounts in the near future to replace hydrocarbons that are widely used nowadays. Therefore, consequences and risks of bulk storage, handling and transport of these materials must be addressed accurately. Because these substances have a low molecular weight, pressurised or liquefied gases released by accident may undergo a transition from heavy gas to rising plume behaviour during dispersion depending on the storage, release and atmospheric conditions, as well as surface effects such as heat transfer. The plume lift-off, plume rise, and the entrainment of ambient air play a significant role in the effect distances and the volume of a flammable or toxic cloud. The consequence modelling software tool EFFECTS contains different dispersion models for neutral and heavy gas dispersion, which are based on a 1-D discretisation method. Since the code for these dispersion models was developed in the past with the focus on heavy or neutral gas conditions, the simulation of buoyant plumes so far was limited. The aim of the present research was to improve the accuracy of the EFFECTS dispersion model for strongly buoyant plumes and predict the transition from the momentum dominated to the buoyant regime correctly. The paper describes the theoretical background of the extensions implemented in the dispersion model in EFFECTS. These extensions are aimed at improving the modelling approach for lighter than air plumes. The validation of the models incorporating these improvements has been performed and is based on results compared against experimental data including instantaneous and continuous releases, jets and low momentum releases from the ground for different materials including helium and hydrogen. [ABSTRACT FROM AUTHOR]

• The city of Burdur has been selected as the target city. • Solar power target of Turkey has been analyzed at urban level for Burdur. • The results show that the solar share of the total installed capacity will reach 49%. The energy profile of a city, with all of the relevant details about production and consumption phases, is a significant part of its sustainability rating. Therefore, municipalities have initiated the development of Sustainable Energy Action Plans as a key document to introduce the respective course of actions in order to define the technology adaptation process, identify the principal sources of CO 2 emissions and their respective reduction potentials for the designated target years. A complete energy-strategy plan is required to handle the financial, technical, and environmental dimensions, not just for the country, but also for cities. As a powerful energy model generator among the energy planning and optimization tools, TIMES utilizes the energy, economy, and environmental parameters simultaneously. This paper aims to oversee and indicate the possible implications of "2023 energy targets" of Turkey in a city-level energy modeling. In this perspective, the city of Burdur is selected as the target to implement the designated solar energy policy targets. With this paper, nationwide official targets are evaluated for a city level by calculating long-term effects and costs to the system. A total of 5000 MW of solar energy utilization target of Turkey has been reduced to the urban level for Burdur, depending on its share of solar energy, and then applied as an alternative scenario on the energy model developed for this analysis. The results show that the solar share of the total installed capacity of Burdur city will reach 49% while tripling the solar-based electricity generation in its energy mix. [ABSTRACT FROM AUTHOR]

• Mercury content in the waste-derived fuels varies within a very wide range. • Co-combustion of waste-derived fuels may result in exceeding the emission limits. • Mercury content of alternative fuels should be strictly controlled. • Appropriate waste management enable the production fuels with suitable Hg content. The progressive decarbonisation of industry is leading to a reduction in coal consumption and the substitution for coal with other types of fuels, including waste-derived alternative fuels. These fuels are characterised by high variation in the content of highly toxic mercury. Co-combustion with coal can cause significant emissions, exceeding mercury emission limits. Various alternative fuels (refuse-derived fuel (RDF), waste paper, textiles, plastics, film, tires and their char, and sewage sludge) were examined for mercury content. The mercury content in analysed alternative fuels ranged from 0.4 to 92.0 µg Hg/MJ, with an average of 17.7 µg Hg/MJ. The fuels with the highest mercury content were RDFs (2.0–79.3 µg Hg/MJ) and sewage sludge (42.3–92.0 µg Hg/MJ). An acceptable amount of RDF added to hard coal which would remain within the emission limits was estimated to be 9–24% of the chemical energy in the blend. For sewage sludge, this amount was estimated to be 5–13%. For brown coal, with a much higher mercury content than hard coal, co-combustion with alternative fuels has a positive effect on reducing mercury emissions. It is possible to meet the mercury emission limits with a 95% contribution of the chemical energy coming from RDF. The blending of various types of waste supported by mild pyrolysis of high-mercury waste allows alternative fuels with relatively low mercury content to be produced. Such fuels may contribute a reduction in mercury emissions from coal-fired power plants in Poland. [ABSTRACT FROM AUTHOR]

Computable General Equilibrium (CGE) models are very popular for analyzing a wide range of policy issues. CGE applications vary from estimating the welfare impact of tax reform and alternative energy policies to the effect of foreign trade reforms, labour markets and employment. CGE models are commonly developed at the country level; however, modified versions of CGE, so called Regional CGE (RCGE) models, can be used at subnational disaggregation to examine impacts studied at the national counterparts on a specific region. RCGE models have grown in popularity as an alternative to the Input-Output (I-O) models, which are regularly used for regional analysis. RCGE models can provide comprehensive information, which make them more desirable analytical models for many researchers. Yet, RCGE models have not yet become a "go-to" for governmental policy practitioners when they are developing regional public policies. This paper reviews the current state of regional CGE models, describes their features, contributions and limitations and surveys some applications of the main three classes of RCGE models: region-specific, bottom-up, and top-down models. This paper concludes that the applications of RCGE are quite variable and flexible, with a new and more complex type of application to be developed with the advancement of computation economics. The paper offers recommendations on the micro, meso and macro conditions that are necessary to increase policy practitioners' utilization of RCGE models. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of spray characterization of MD-NH (a blend of methyl decanoate and n-heptane in a molar ratio of 1:1 to characterize biodiesel) in an in-cylinder environment of diesel engines to provide a reference for the experimental study of engines in advanced combustion mode. Based on the Peng-Robinson state equation, the thermodynamic model of real fluid was established, and the influence law of ambient temperature and pressure on the diffusion characteristics of fuel flow was analyzed. Based on the constant volume combustion bomb experiments, the variations of spray penetration distance, spray cone angle, spray projection area, spray air entrainment mass, and spray fragmentation forms in different critical environment conditions were studied. The results show that the transport properties of the fuel change abruptly within the critical point neighborhood of the fuel. As the ambient temperature increases, near the critical temperature, the thermal conductivity of biodiesel decreases and then increases; density and kinematic viscosity decrease at an accelerated rate; and surface tension increases to a maximum and then disappears sharply. The diffusion coefficient decreases sharply when the ambient pressure reaches the critical pressure. The spray characteristics of biodiesel in sub/supercritical conditions were different. Compared with the subcritical environment, the biodiesel spray penetration distance decreases, the spray cone angle increases, the spray projection area decreases, and the air entrainment mass increases in the supercritical atmosphere, which induces a gas-liquid interface mixing layer and promotes the mixing of biodiesel with the atmosphere gas. The experimental data in this paper fill the gap in the study of biodiesel spray characteristics in supercritical environments and provide a basis for high-fidelity numerical simulation of the spray model. • This paper used MD-NH (a blend of 1 mol of methyl decanoate and 1 mol of n-heptane) as the characterization fuel for biodiesel. • The influence laws of temperature and pressure on the thermophysical properties of MD-NH fuel were investigated. • The spray characteristics of MD-NH in real engine environmental conditions were quantitatively analyzed using the schlieren method. • The spray fragmentation form of MD-NH fuel in different environments was analyzed multivariable. [ABSTRACT FROM AUTHOR]

The substitution of fossil fuels with renewable energy sources such as hydrogen is a decisive factor in making aviation environmentally compatible. A key parameter for the use of hydrogen is the storage system. In the design of a flight-capable storage system, not only the mass but especially the volume of the hydrogen has to be considered. Therefore, in this paper different techniques are compared and evaluated from the point of view of their application in aircraft design. The analyses are performed on two reference aircraft, the Airbus A320 and the Embraer E 190, in the short- and medium-haul range. Simplified, it is assumed that the respective max. Take-off mass (MTOM) remains constant. The change of the necessary periphery has no influence on the MTOM. A tank concept could be designed, which can find applications in today's conventional aircraft design. • Energy consumption calculated for A320 and E 190. • Flight data evaluation. • Comparison of different storage methods. • Calculation of volumes for different storage methods and ambient pressures. • Discussion about possible constructive misplacement. [ABSTRACT FROM AUTHOR]

In this paper, we propose a simple approach consisting in the use of a coating layer on a commercial SOFC in order to increase its fuel flexibility. Using the same CO 2 -laser-cut cell, we compared the I–V curves and impedance spectra (EIS) of four experiments. Three different ceramics (NiCu-CGO, NiFe-CGO, and NiCo-CGO) were evaluated as protective layers for cells fed with dry biogas or bioethanol, with the goal of determining which layer would be most promising. Electrochemical experiments revealed that an additional layer adds resistance to the cell, which negatively affects its performance. A slight decrease in maximum performance was observed when the coated cells were fed H 2. However, power density was not significantly different from the bare cell at potentials between 0.7 and 0.8 V, which provide a trade-off between performance and voltage efficiency. Additionally, such an approach improved the effectiveness of cells in using simulated biogas and ethanol as demonstrated by I–V curves and EIS analysis. As shown in the test results, NiCo-CGO provided the highest power density of 0.56 W cm−2 at 0.6 V. However, all the cells with protective layers performed significantly better than the bare cell in the dry biofuel tests. [ABSTRACT FROM AUTHOR]

Surmounted environmental concerns and energy challenges have created an augmented awareness among the public and policymakers about alternate energy resources. Using a network approach, this paper aims to investigate the dependence between cryptocurrencies and the alternative energy market using data from January 1, 2018, to December 23, 2021. For this investigation, first, we build a static dependency network for a given set of variables using partial correlations. Then, we demonstrate within-system connections in a minimum spanning tree (MST) to assess the centrality of all variables. Finally, rolling-window estimations are made to exhibit time variations in both dependency and centrality networks. We find that clean alternative markets (SPGCE, ELEVHC & WILCE) and ETH are net risk transmitters to other markets and system-wide net contributors. We also demonstrate how SPGCE is essential for tying together the various parts of the networks and provide convincing evidence of time-varying within-system dependency. Our thorough examination of the dependency analysis offers significant insights to macroprudential regulators, policymakers, and portfolio managers, enabling them to safeguard the most vulnerable markets and choose the best legislative and policy measures to protect investors' interests in the face of unforeseen financial and economic conditions. [ABSTRACT FROM AUTHOR]