Production & Supply Chain

Dark fermentation (DF) has gained increasing interest over the past two decades as a sustainable route for biohydrogen production; however understanding how reproducible the process can be both from macro- and microbiological perspectives remains limited. This study assessed the reproducibility of a parallel continuous DF system using fruit-vegetable waste as a substrate under strictly controlled operational conditions. Three stirred-tank reactors were operated in parallel for 90 days monitoring key process performance indicators. In addition to baseline operation different process enhancement strategies were tested including bioaugmentation supplementation with nutrients and/or additional fermentable carbohydrates and modification of key operational parameters such as pH and hydraulic retention time all widely used in the field to improve DF performance. Microbial community structure was also analyzed to evaluate its reproducibility and potential relationship with process performance and metabolic patterns. Under these conditions key performance indicators and core microbial features were reproducible to a large extent yet full consistency across reactors was not achieved. During operation unforeseen operational issues such as feed line clogging pH control failures and mixing interruptions were encountered. Despite these disturbances the system maintained an average hydrogen productivity of 3.2 NL H2/L-d with peak values exceeding 6 NL H2/L-d under optimal conditions. The dominant microbial core included Bacteroides Lactobacillus Veillonella Enterococcus Eubacterium and Clostridium though their relative abundances varied notably over time and between reactors. An inverse correlation was observed between lactate concentration in the fermentation broth and the amount of hydrogen produced suggesting it can serve as a precursor for hydrogen. Overall the findings presented here demonstrate that DF processes can be resilient and broadly reproducible. However they also emphasize the sensitivity of these processes to operational disturbances and microbial shifts. This underscores the necessity for refined control strategies and further systematic research to translate these insights into stable high-performance real-world systems.

Water electrolyzers play a crucial role in green hydrogen production. However their efficiency and scalability are often compromised by bubble dynamics across various scales from nanoscale to macroscale components. This review explores multi-scale modeling as a tool to visualize multi-phase flow and improve mass transport in water electrolyzers. At the nanoscale molecular dynamics (MD) simulations reveal how electrode surface features and wettability influence nanobubble nucleation and stability. Moving to the mesoscale models such as volume of fluid (VOF) and lattice Boltzmann method (LBM) shed light on bubble transport in porous transport layers (PTLs). These insights inform innovative designs including gradient porosity and hydrophilic-hydrophobic patterning aimed at minimizing gas saturation. At the macroscale VOF simulations elucidate two-phase flow regimes within channels showing how flow field geometry and wettability affect bubble discharging. Moreover artificial intelligence (AI)-driven surrogate models expedite the optimization process allowing for rapid exploration of structural parameters in channel-rib flow fields and porous flow field designs. By integrating these approaches we can bridge theoretical insights with experimental validation ultimately enhancing water electrolyzer performance reducing costs and advancing affordable highefficiency hydrogen production.

The paper investigates the potential of co-electrolysis as a viable pathway for hydrogen production and industrial decarbonization expanding on previous studies on water electrolysis. The analysis adopts a general and critical perspective aiming to assess the realistic scope of this technology with regard to current energy and environmental needs. Although co-electrolysis theoretically offers improved efficiency by simultaneously converting H2O and CO2 into syngas the practical advantages are difficult to consolidate. The study highlights that the energetic margins of the process remain relatively narrow and that several key aspects including system irreversibility and the limited availability of CO2 in many contexts significantly constrain its applicability. Despite the growing interest and promising technological developments co-electrolysis still faces substantial challenges before it can be implemented on a larger scale. The findings suggest that its success will depend on targeted integration strategies advanced thermal management and favorable boundary conditions rather than on the intrinsic efficiency of the process alone. However there are specific sectors where assessing the implementation potential of co-electrolysis could be of interest a perspective this paper aims to explore.

The current study evaluates the feasibility of a forward osmosis membrane bioreactor (FO-MBR) for dark fermentation aiming at simultaneous biohydrogen production and wastewater treatment. Optimal microbial inoculation was achieved via heat-treated activated sludge enriching Clostridium sensu stricto 1 and yielding up to 2.21 mol H2.(mol hexose)− 1 in batch mode. In continuous operation a substrate concentration of 4.4 g L− 1 and a hydraulic retention time (HRT) of 12 h delivered the best results producing 1.51 mol H2.(mol hexosesupplied) − 1 . The FO-MBR configured with a 1.1 m2 hollow fiber side-stream membrane module and operated under dynamic HRT (2.5–12 h) dependent on membrane flux was integrated with intermittent CSTR (Continuous stirred tank reactor) operation to counter metabolite accumulation. This system outperformed a conventional CSTR achieving a hydrogen yield of 1.78 mol H2.(mol hexosesupplied) − 1 . Remarkable treatment efficiencies were observed with BOD5 COD and TOC removal rates of 95.32 % 99.02 % and 99.10 % respectively and an 83.8 % reduction in total waste volume. Additionally the FO-MBR demonstrated strong antifouling performance with 96.14 % water flux recovery achieved after a brief 5 min hydraulic rinse following 47.5 h of continuous highstrength broth exposure. These results highlight the FO-MBR system’s ability as a sustainable and highperformance alternative for integrated hydrogen production and effluent treatment. Further studies are recommended to address long-term fouling control and metabolite management for industrial scalability.

Photoelectrochemical (PEC) water splitting is a promising technology for green hydrogen production by harnessing solar energy. Traditionally this sustainable approach is studied under light intensity of 100 mW/cm2 mimicking the natural solar irradiation at the Earth’s surface. Sunlight can be easily concentrated using simple optical systems like Fresnel lens to enhance charge carrier generation and hydrogen production in PEC water splitting. Despite the great potentials this strategy has not been extensively studied and faces challenges related to the stability of photoelectrodes. To prompt the investigations and applications this work outlines the best practices and protocols for conducting PEC solar water splitting under concentrated sunlight illumination incorporating our recent advancements and providing some experimental guidelines. The key factors such as light source calibration photoelectrode preparation PEC cell configuration and long-term stability test are discussed to ensure reproducible and high performance. Additionally the challenges of the expected photothermal effect and the heat energy utilization strategy are discussed.

This study focuses on enhancing the efficiency of alkaline water electrolysis technology a key process in green hydrogen production by leveraging the synergy of magnetic fields and in situ electrode activation. Optimizing AWE efficiency is essential to meet increasing demands for sustainable energy solutions. In this research nickel mesh electrodes were modified through the application of magnetic fields and the addition of hypo-hyper d-metal (cobalt complexes and molybdenum salt) to the electrolyte. These enhancements improve mass transfer facilitate bubble detachment and create a high-surface-area catalytic layer on the electrodes all of which lead to improved hydrogen evolution rates. The integration of magnetic fields and in situ activation achieved over 35% energy savings offering a cost-effective and scalable pathway for industrial green hydrogen production.

This review investigates hydrogen production via photocatalysis using ammonia a carbon-free source potentially present in wastewater. Photocatalysis offers low energy requirements and high conversion efficiency compared to electrocatalysis thermocatalysis and plasma catalysis. However challenges such as complex material synthesis low stability spectral inefficiency high costs and integration barriers hinder industrial scalability. The review addresses thermodynamic requirements reaction mechanisms and the role of pH in optimizing photocatalysis. By leveraging ammonia’s potential and advancing photocatalyst development this study provides a framework for scalable sustainable hydrogen production and simultaneous ammonia decomposition paving the way for innovative energy solutions and wastewater management.

This study offers a novel techno-economic evaluation of a small hydrogen generation system included into a residential villa in Sharjah. The system is designed to utilize solar energy for hydrogen production using an electrolyzer. The study assesses two scenarios: one lacking a fuel cell and the other incorporating a fuel cell stack for backup power. The initial scenario employs a solar-powered electrolyzer for hydrogen production attaining a competitive levelized cost of energy (LCOE) of $0.1846 per kWh and a hydrogen cost of $4.65 per kg. These data underscore the economic viability of utilizing electrolyzers for hydrogen generation. The system produces around 1230 kg of hydrogen per annum rendering it appropriate for many uses. Nevertheless the original investment expenditure of $73980 necessitates more optimization. The second scenario includes a 10 kW fuel cell for energy autonomy. This scenario has a marginally reduced LCOE of 0.1811 $/kWh and a cumulative net present cost of $72600. The fuel cell runs largely at night proving the efficiency of the downsizing option in decreasing capital expense. The system generates electricity from solar panels (66.1 MWh/year) and the fuel cell (16.9 MWh/year) exhibiting a multi-source power generating technique. The results indicate that scaled-down hydrogen generation systems both with and without fuel cells may offer sustainable and possibly lucrative renewable energy options for household use especially in areas with ample solar resources such as Sharjah.

Green hydrogen (GH2) a sustainable and clean energy carrier is increasingly regarded as a solution to energy challenges and environmental issues. Industrial wastewater possesses a significant potential for hydrogen generation using biological chemical and electrochemical methods. This review analysis evaluates progress in GH2 production from industrial wastewater highlighting its environmental and cost benefits. Process optimization technological improvements and enhancements in catalysts for chemical and electrochemical hydrogen generation are also provided. It also considers the integration of GH2 production methods with wastewater treatment procedures to achieve synergistic benefits including enhanced pollutant removal and energy recovery. Challenges associated with GH2 production include substrate variability economic viability reactor scalability and environmental sustainability are also discussed. Also this review provides a future outlook to promote sustainable energy solutions and tackle global environmental issues related to GH2 from industrial wastewater.

This study investigates the integration of multiple energy carriers within a unified multi-carrier energy system using an energy cascade approach. The system harnesses geothermal energy to power interconnected subsystems including an organic Rankine cycle (ORC) liquefied natural gas (LNG) and a solid oxide fuel cell (SOFC) stack. The dual ORC system and LNG stream are directly fed from the geothermal source while the SOFC stack uses methane produced during LNG regasification. Besides electricity the system generates hydrogen and desalinated water by incorporating a proton exchange membrane (PEM) electrolyzer and a reverse osmosis (RO) desalination plant. The electricity produced by the upper ORC powers the PEME for hydrogen production while freshwater production is supported by the combined output from the lower ORC LNG turbine and SOFC. A detailed thermo-economic analysis assesses the system’s efficiency and economic feasibility. Optimization efforts focus on three areas: electrical efficiency hydrogen and freshwater production using artificial neural networks (ANN) and genetic algorithms (GA). The optimization results reveal that Ammonia-propylene excels in electrical efficiency R1234ze(Z)-ethylene in net power output R1233zd(E)-propylene in cost-effectiveness R1234ze(Z)-propylene in hydrogen production and Ammonia-ethane in water production. The study offers valuable insights into enhancing the efficiency cost-effectiveness and sustainability of integrated energy systems.

Developing clean and renewable energy instead of the ones related to hydrocarbon resources has been known as one of the different ways to guarantee reduced greenhouse gas emissions. Geothermal systems and native hydrogen exploration could represent an opportunity to diversify the global energy matrix and lower carbon-related emissions. All of these natural energy sources require a well to be drilled for its access and/or extractions similar to the petroleum industry. The main focuses of this technical–scientific contribution and research are (i) to evaluate the global energy matrix; (ii) to show the context over the years and future perspectives on geothermal systems and natural hydrogen exploration; and (iii) to present and analyze the importance of developing technologies on drilling process optimization aiming at accessing these natural energy resources. In 2022 the global energy matrix was composed mainly of nonrenewable sources such as oil natural gas and coal where the combustion of fossil fuels produced approximately 37.15 billion tons of CO2 in the same year. In 2023 USD 1740 billion was invested globally in renewable energy to reduce CO2 emissions and combat greenhouse gas emissions. In this context currently about 353 geothermal power units are in operation worldwide with a capacity of 16335 MW. In addition globally there are 35 geothermal power units under pre-construction (project phase) 93 already being constructed and recently 45 announced. Concerning hydrogen the industry announced 680 large-scale project proposals valued at USD 240 billion in direct investment by 2030. In Brazil the energy company Petroleo Brasileiro SA (Petrobras Rio de Janeiro Brazil) will invest in the coming years nearly USD 4 million in research involving natural hydrogen generation and since the exploration and access to natural energy resources (oil and gas natural hydrogen and geothermal systems among others) are achieved through the drilling of wells this document presents a technical–scientific contextualization of social interest.

The widespread penetration of hydrogen in mainstream energy systems requires hydrogen production processes to be economically competent and environmentally efficient. Hydrogen if produced efficiently can play a pivotal role in decarbonizing the global energy systems. Therefore this study develops a framework which evaluates hydrogen production processes and quantifies deficiencies for improvement. The framework integrates slack-based data envelopment analysis (DEA) with fuzzy analytical hierarchy process (FAHP) and fuzzy technique for order of preference by similarity to ideal solution (FTOPSIS). The proposed framework is applied to prioritize the most efficient and sustainable hydrogen production in Pakistan. Eleven hydrogen production alternatives were analyzed under five criteria including capital cost feedstock cost O&M cost hydrogen production and CO2 emission. FAHP obtained the initial weights of criteria while FTOPSIS determined the ultimate weights of criteria for each alternative. Finally slack-based DEA computed the efficiency of alternatives. Among the 11 three alternatives (wind electrolysis PV electrolysis and biomass gasification) were found to be fully efficient and therefore can be considered as sustainable options for hydrogen production in Pakistan. The rest of the eight alternatives achieved poor efficiency scores and thus are not recommended.

In this paper we propose an alternative strategy to produce green hydrogen in a more sustainable way than standard water electrolysis where a substantial amount of the electrical energy is wasted in the oxygen evolution quite often simply released in the atmosphere. The HER (hydrogen evolution reaction) is effectively coupled with the oxidation of guaiacol at the anode leading to the simultaneous production of H2 and valuable guaiacol oligomers. Significative points i) a substantial decrease of the potential difference for the HER 0.85 V with guaiacol ii) HER is accompanied by the production of industrially appealing and sustainable guaiacol based oligomers iii) guaiacol oxidation runs efficiently on carbon-based surfaces like graphite and glassy carbon which are cheap and not-strategic materials. Then the electrochemical oxidation mechanism of guaiacol is studied in detail with in-situ EPR measurements and post-electrolysis product characterization: LC-DAD LC-MS and NMR. Experimental results and theoretical calculations suggest that guaiacol polymerization follows a Kane-Maguire mechanism.

In Spain the winery industry exerts a great influence on the national economy. Proportional to the scale of production a significant volume of waste is generated estimated at 2 million tons per year. In this work a laboratory-scale reactor was used to study the feasibility of the energetic valorization of winery effluents into hydrogen by means of dark fermentation and its subsequent conversion into electrical energy using fuel cells. First winery wastewater was characterized identifying and determining the concentration of the main organic substrates contained within it. To achieve this a synthetic winery effluent was prepared according to the composition of the winery wastewater studied. This effluent was fermented anaerobically at 26 ◦C and pH = 5.0 to produce hydrogen. The acidogenic fermentation generated a gas effluent composed of CO2 and H2 with the percentage of hydrogen being about 55% and the hydrogen yield being about 1.5 L of hydrogen at standard conditions per liter of wastewater fermented. A gas effluent with the same composition was fed into a fuel cell and the electrical current generated was monitored obtaining a power generation of 1 W·h L−1 of winery wastewater. These results indicate that it is feasible to transform winery wastewater into electricity by means of acidogenic fermentation and the subsequent oxidation of the bio-hydrogen generated in a fuel cell.

A comprehensive literature review highlights how the nature of active metals support materials promoters and synthesis methods influences catalytic performance with particular attention to ruthenium-based catalysts as the current benchmark. Kinetic models are presented to describe the reaction pathway and predict catalyst behavior. Various reactor configurations including fixed-bed membrane catalytic membrane perovskitebased and microreactors are evaluated in terms of their suitability for ammonia decomposition. While ruthenium remains the benchmark catalyst alternative transition metals such as iron nickel and cobalt have also been investigated although they typically require higher operating temperatures (≥500 °C) to achieve comparable conversion levels. At the industrial scale catalyst development must balance performance with cost. Inexpensive and scalable materials (e.g. MgO Al2O3 CaO K Na) and simple preparation techniques (e.g. wet impregnation incipient wetness) may offer lower performance than more advanced systems but are often favored for practical implementation. From a reactor engineering standpoint membrane reactors emerge as the most promising technology for combining catalytic reaction and product separation in a single unit operation. This review provides a critical overview of current advances in ammonia decomposition for hydrogen production offering insights into both catalytic materials and reactor design strategies for sustainable energy applications.

The production of hydrogen through water electrolysis has emerged as a promising alternative to decarbonizing the energy sector especially when integrated with renewable energy sources. Among the key operational parameters that affect electrolysis performance temperature and current density play a critical role in determining the energy efficiency hydrogen yield and durability of the system. The study presents a Systematic Literature Review (SLR) that includes peer-reviewed publications from 2018 to 2025 focusing on the effects of temperature and current density across a variety of electrolysis technologies including alkaline (AEL) proton exchange membrane (PEMEL) and solid oxide electrolysis cells (SOEC). A total of seven high-quality studies were selected following the PRISMA 2020 framework. The results show that high temperatures improve electrochemical kinetics and reduce excess potential especially in PEM and SOEC systems but can also accelerate component degradation. Higher current densities increase hydrogen production rates but lead to lower Faradaic efficiency and increased material stress. The optimal operating range was identified for each type of electrolysis with PEMEL performing best at 60–80 ◦C and 500–1000 mA/cm2 and SOEC at >750 ◦C. In addition system-level studies emphasize the importance of integrating hydrogen production with flexible generation and storage infrastructure. The review highlights several research gaps including the need for dynamic modeling multi-parameter control strategies and techno-economic assessments. These findings provide a basic understanding for optimizing hydrogen electrolysis systems in low-carbon energy architectures.

Hydrogen (H2) yields from various gasification and hydrothermal processes demonstrate significant variability depending on feedstock catalysts and process parameters. This systematic review explores hydrogen production through hydrochar-based gasification technologies focusing on the unique properties of hydrochar derived from biomass. Known for its ability to enhance syngas production especially hydrogen hydrochar’s porous structure high surface area and active catalytic sites significantly improve syngas quality and hydrogen yield. Studies show that supercritical water gasification (SCWG) of almond shells with hydrochars yielded up to 11.63 mmol/g while catalytic subcritical and SCWG of waste tires reached 19.7 mmol/g. Hydrothermal carbonization (HTC) coupled with gasification yields as high as 76.7 g H2/kg biochar for sewage sludge hydrochar with processes like anaerobic digestion and HTC producing 1278 mL/g from hemp hurd hydrochar. Key aspects such as the catalytic influence of hydrochar the role of additives and co-catalysts and optimization of gasification parameters including temperature pressure and equivalence ratios are explored. The review also delves into hydrochar preparation advancements such as alkali and alkaline earth metals (AAEMs) incorporation and highlights hydrochar’s role in reducing tar formation enhancing H2/CO ratios and stabilizing syngas heating value.

The industrial sector’s movement toward decarbonization is regarded as essential for governments. This paper assesses a system that uses only solar energy to synthesize liquid hydrogen and ammonia as energy carriers. Photovoltaic modules deliver electrical power while parabolic dish collectors are responsible for directing thermal energy to the solid oxide electrolyzer for hydrogen production which then mixes with nitrogen to produce ammonia after a number of compression stages. To investigate the proposed system comprehensive thermodynamic and exergo-economic studies are performed using an engineering equation solver and ASPEN PLUS software.

The present work aims to develop a uniquely designed experimental test rig for hydrogen (H2) production from hydrogen sulfide (H2S) and perform performance tests. The experimental activity focuses on the FeCl3 hybrid process for H2S cracking followed by H2S absorption sulfur purification and electrolysis for efficient H2 production. Hydrogen production is studied using KOH and FeCl3 electrolytes under varying temperatures between 20-80 ◦C. An electrochemical impedance spectroscopy (EIS) is employed to characterize the electrochemical cell under potentiostatic (0.5-2.0 V) and galvanostatic (0-0.5 mA) modes to analyze the system’s electrochemical response. The study results showed that hydrogen production increased by over 426 % from 20 ◦C to 80 ◦C. EIS analysis under potentiostatic mode showed Nyquist semicircle diameter reduced as the applied voltage increased from 0.5 V to 1.5 V and phase angle shifted from -5.59◦ to -1.27◦ confirming enhanced conductivity. Under galvanostatic mode the impedance dropped from ~25 Ω to ~21 Ω as current increased demonstrating improved kinetics for efficient H2 production.

Green hydrogen plays a vital role in facilitating the transition to sustainable energy systems with stable and high-capacity offshore wind resources serving as an ideal candidate for large-scale green hydrogen production. However as the capacity of offshore wind turbines continues to grow the increasing size and weight of these systems pose significant challenges for installation and deployment. This study investigates the application of high-temperature superconducting (HTS) materials in the generator and the power conducting cables as a promising solution to these challenges. Compared to conventional wind turbines HTS wind turbines result in significant reductions in weight and size while simultaneously enhancing power generation and transmission efficiency. This paper conducts a comprehensive review of mainstream electrolysis-based hydrogen production technologies and advanced hydrogen storage methods. The main contribution of this research is the development of an innovative conceptual framework for a superconducting offshore windto-hydrogen energy system where a small amount of liquid hydrogen is used to provide a deep-cooling environment for the HTS wind turbine and the remaining liquid hydrogen is used for the synthesis of ammonia as a final product. Through functional analysis this study demonstrates its potential for enabling large-scale offshore hydrogen production and storage. Additionally this paper discusses key challenges associated with real-world implementation including optimizing the stability of superconducting equipment and ensuring component coordination. The findings offer crucial insights for advancing the offshore green hydrogen sector showing that HTS technology can significantly enhance the energy efficiency of offshore wind-to-hydrogen systems. This research provides strong technical support for achieving carbon neutrality and fostering sustainable development in the offshore renewable energy sector.

High-temperature electrolysis offers a solution for industry decarbonisation by high-efficiency hydrogen production. This study presents a system based on Solid Oxide Electrolysis Cells (SOEC) fed by photovoltaic and waste heat recovery for hydrogen blending with natural gas in industrial burners. The aim of this work is to assess techno-economic feasibility of the proposed configuration investigating hydrogen blending limits Levelized Cost of Hydrogen (LCOH) and decarbonisation cost. LCOH values below 6 €/kgH2 cannot be achieved at current SOEC costs. The system can be applied without significant burner modifications since maximum hydrogen volumetric fractions are less than 20 %. Higher efficiency and emission reduction potential in comparison to alkaline electrolysers can be achieved but they are offset by higher LCOH and carbon abatement costs. Forthcoming reduction in SOEC costs can improve the cost-effectiveness and high natural gas prices experienced during the energy crisis make the decarbonisation cost competitive with the emission trading system.

N-type sulfide semiconductors are promising photocatalysts due to their broad visible-light absorption facile synthesis and chemical diversity. However photocorrosion and limited electron transport in one-step excitation and solid-state Z-scheme systems hinder efficient overall water splitting. Liquidphase Z-schemes offer a viable alternative but sluggish mediator kinetics and interfacial side reactions impede their construction. Here we report a stable Z-scheme system integrating n-type CdS and BiVO₄ with a [Fe(CN)₆]³⁻/[Fe(CN)₆]⁴⁻ mediator achieving 10.2% apparent quantum yield at 450 nm with stoichiometric H₂/O₂ evolution. High activity reflects synergies between Pt@CrOx and Co3O4 cocatalysts on CdS and cobalt-directed facet asymmetry in BiVO₄ resulting in matched kinetics for hydrogen and oxygen evolution in a reversible mediator solution. Stability is dramatically improved through coating CdS and BiVO4 with different oxides to inhibit Fe4[Fe(CN)6]3 precipitation and deactivation by a hitherto unrecognized mechanism. Separate hydrogen and oxygen production is also demonstrated in a twocompartment reactor under visible light and ambient conditions. This work unlocks the long-sought potential of n-type sulfides for efficient durable and safe solar-driven hydrogen production.

Hydrogen plays a key role in many industrial applications and is currently seen as one of the most promising energy vectors. Many efforts are being made to produce hydrogen with zero CO 2 footprint via water electrolysis powered by renewable energies. Nevertheless the use of fossil fuels is essentialin the short term. The conventional coal gasification and steam methane reforming processes for hydrogen production are undesirable due to the huge CO2 emissions. A cleaner technologybased on natural gas that has received special attention in recent years is methane pyrolysis. The thermal decomposition of methane gives rise to hydrogen and solid carbon and thus the release of greenhouse gases is prevented. Therefore methane pyrolysis is a CO2-free technology that can serve as a bridge from fossil fuels torenewable energies.

As global energy demand increases and reliance on fossil fuels becomes unsustainable hydrogen presents a promising clean energy alternative due to its high energy density and potential for significant CO2 emission reductions. However current hydrogen production methods largely depend on fossil fuels contributing to considerable CO2 emissions and underscoring the need to transition to renewable energy sources and improved production technologies. Life Cycle Analysis (LCA) is essential for evaluating and optimizing hydrogen production by assessing environmental impacts such as Global Warming Potential (GWP) energy consumption toxicity and water usage. The key findings indicate that energy sources and feedstocks heavily influence the environmental impacts of hydrogen production. Hydrogen production from renewable energy sources particularly wind solar and hydropower demonstrates significantly lower environmental impacts than grid electricity and fossil fuel-based methods. Conversely hydrogen production from grid electricity primarily derived from fossil fuels shows a high GWP. Furthermore challenges related to data accuracy economic analysis integration and measuring mixed gases are discussed. Future research should focus on improving data accuracy assessing the impact of technological advancements and exploring new hydrogen production methods. Harmonizing assessment methodologies across different production pathways and standardizing functional units such as “1 kg of hydrogen produced “ are critical for enabling transparent and consistent sustainability evaluations. Techniques such as stochastic modelling and Monte Carlo simulations can improve uncertainty management and enhance the reliability of LCA results.

Hydrogen gas is a promising clean-energy vector that can alleviate the current imbalance between energy supply and demand diversify the energy portfolio and underpin the sustainable development of oil and gas resources. This study pinpoints the factors that govern hydrogen quantification by pulsed-neutron logging. Monte Carlo simulations were performed to map the spatial distribution of capture γ-rays in formations saturated with either water or hydrogen and to systematically assess the effects of pore-fluid composition hydrogen density gas saturation lithology and borehole-fluid type. The results show that the counts of capture γ-rays are litter in hydrogen-bearing formations. For lowto moderate-porosity rocks the dynamic response window for hydrogensaturated pores is approximately 10% wider than that for methane-saturated pores. Increasing hydrogen density or decreasing gas saturation raises the capture-γ ratio while narrowing the dynamic range. Changes in borehole fluid substantially affect the capture-γ ratio yet have only a minor impact on the dynamic range. Lithology imposes an additional control: serpentinite enriched in structural water generates markedly higher capture-γ ratios that may complicate the quantitative evaluation of hydrogen.