Publications

This study evaluates the potential of hydrogen as a clean additive to conventional diesel fuel. Experiments were carried out on a single-cylinder air-cooled diesel engine under half- and full-load conditions across engine speeds ranging from 1000 to 3000 rpm. Hydrogen produced on site via a proton exchange membrane electrolyser was supplied to the engine at a constant flow rate of 0.5 L/min. Compared to pure diesel the hydrogen–diesel blend reduced specific fuel consumption by 10% and increased brake thermal efficiency by 10% at full load. Emissions of carbon monoxide and carbon dioxide decreased by 13% and 17% respectively at half load. Additionally nitrogen oxide emissions dropped by 17%. These results highlight the potential of hydrogen to improve combustion efficiency while significantly mitigating emissions offering a viable transitional solution for cleaner power generation using existing diesel infrastructure.

Hydrogen energy as a medium for long-term energy storage needs to ensure the continuous and stable operation of the electrolyzer during the production of green hydrogen using wind energy. In this paper based on the overall model of a wind power hydrogen production system an integrated control strategy aimed at improving the quality of wind power generation smoothing the hydrogen production process and enhancing the stability of the system is proposed. The strategy combines key measures such as the maximum power point tracking control of the wind turbine and the adaptive coordinated control of the electrochemical energy storage system which can not only efficiently utilize the wind resources but also effectively ensure the stability of the bus voltage and the smoothness of the hydrogen production process. The simulation results show that the electrolyzer can operate at full power to produce hydrogen while the energy storage device is charging when wind energy is sufficient; the electrolyzer continuously produces hydrogen according to the wind energy when the wind speed is normal; and the energy storage device will take on the task of maintaining the operation of the electrolyzer when the wind speed is insufficient to ensure the stability and reliability of the system.

Hydrogen storage remains the main barrier to the broader use of hydrogen as an energy carrier despite hydrogen’s high energy density and clean combustion. This study presents a comparative evaluation of conventional and emerging storage methods integrating thermodynamic kinetic economic and environmental metrics to assess capacity efficiency cost and reversibility. Physisorption analysis reveals that metal organic frameworks can achieve storage capacities up to 14.0 mmol/g. Chemical storage systems are evaluated including nanostructured MgH2 (7.6 wt%) catalyzed reversible complex hydrides liquid organic hydrogen carriers and clathrate hydrates. Techno-economic analysis shows storage costs from $500–700/kg H2 to $30–50/kg H2 with energy efficiencies of 50%–90%. Life cycle assessment identifies manufacturing as the primary source of emissions with carbon footprints varying from 150 to 2057 kg CO2 -eq/kg H2 . Cryo-compressed is the most practical transportation option while metal hydrides suit stationary use. This study provides a quantitative foundation to guide material selection and system design for next-generation hydrogen storage technologies.

Hydrogen tanks used in transportation are equipped with thermal pressure relief devices to prevent a tank rapture in case of fire exposure. The opening of the pressure relief valve in such a scenario would likely result in an impinging and (semi-) confined hydrogen jet fire. Therefore twelve largescale experiments of hydrogen jet fires and one large-scale propane reference experiment have been conducted with various degrees of confinement orientations of the jet and distances from the nozzle to the impinging surface. Infrared and visible light videos temperatures heat fluxes and mass flow rate of hydrogen or propane were recorded in each experiment. It was found that the hydrogen flame can be visible under certain conditions. The main difference between an open impinging jet and an enclosed impinging jet fire is the extent of the high-temperature region in the steel target. During the impinging jet fire test 51% of the exposed target area exceeded 400C while 80% of the comparable area exceeded 400C during the confined jet fire test. A comparison was also made to an enclosed propane jet fire. The temperature distribution during the propane fire was more uniform than during the hydrogen jet fire and the localized hot spot in the impact region as seen in the hydrogen jet fires was not recorded.

The article presents the results of an experimental study on the influence of hydrogen as gaseous fuel on the combustion process parameters of a single-cylinder diesel engine operating in dual-fuel mode. The study is conducted at an average engine speed of n = 2000 min⁻ 1 four engine load levels and two different diesel fuel injection timing angles. Indicator diagrams are recorded for each operating mode at varying hydrogen mass fractions in the total fuel supplied to the engine. The data from the indicator diagrams are processed using a developed software that enables the determination of combustion process parameters. The analysis of the experimental results focuses on changes in cylinder temperature the coefficients of total and active heat release the rate of heat release the duration of the combustion process phases and other parameters as a function of the hydrogen mass fraction in the total fuel mixture.

Hydrogen as fuel in civil aviation gas turbines is promising due to its no-carbon content and higher net specific energy. For an entry-level market and cost-saving strategy it is advisable to consider reusing existing engine components whenever possible and retrofitting existing engines with hydrogen. Feasible strategies of retrofitting state-of-theart Jet A-1 fuelled turbofan engines with hydrogen while applying minimum changes to hardware are considered in the present study. The findings demonstrate that hydrogen retrofitted engines can deliver advantages in terms of core temperature levels and efficiency. However the engine operability assessment showed that retrofitting with minimum changes leads to a ~5% increase in the HP spool rotational speed for the same thrust at take-off which poses an issue in terms of certification for the HP spool rotational speed overspeed margin.

This review article provides an overview of the use of hydrogen and tyre pyrolysis oil as fuels for homogeneous charge compression ignition (HCCI) engines. It discusses their properties the ways they are produced and their sustainability which is of particular importance in the present moment. Both fuels have certain advantages but also throw up many challenges which complicate their application in HCCI engines. The paper scrutinises engine performance with hydrogen and tyre pyrolysis oil respectively and compares the fuels’ emissions a crucial focus from an environmental perspective. It also surveys related technologies that have recently emerged their effects and environmental impacts and the rules and regulations that are starting to become established in these areas. Furthermore it provides a comparative discussion of various engine performance data in terms of combustion behaviour emission levels fuel economy and potential costs or savings in real terms. The analysis reveals significant research gaps and recommendations are provided as to areas for future study. The paper argues that hydrogen and tyre pyrolysis oil might sometimes be used together or in complementary ways to benefit HCCI engine performance. The importance of life-cycle assessment is noted acknowledging also the requirements of the circular economy. The major findings are summarised with some comments on future perspectives for the use of sustainable fuels in HCCI engines. This review article provides a helpful reference for researchers working in this area and for policymakers concerned with establishing relevant legal frameworks as well as for companies in the sustainable transport sector.

It is believed that hydrogen will play an essential role in energy transition and achieving the net-zero target by 2050. Currently global hydrogen production mostly relies on processing fossil fuels such as coal and natural gas commonly referred to as grey hydrogen production while releasing substantial amounts of carbon dioxide (CO2). Developing economically and technologically viable pathways for hydrogen production while eliminating CO2 emissions becomes paramount. In this critical review we examine the common grey hydrogen production techniques by analyzing their technical characteristics production efficiency and costs. We further analyze the integration of carbon capture utilization and storage (CCUS) technology establishing the zero-carbon strategy transiting from grey to blue hydrogen production with CO2 capture and either utilized or permanently stored. Today grey hydrogen production exhibits technological diversities with various commercial maturities. Most methods rely on the effectiveness of catalysts necessitating a solution to address catalyst fouling and sintering in practice. Although CCUS captures utilizes or stores CO2 during grey hydrogen production its wide application faces multiple challenges regarding the technological complexity cost and environmental benefits. It is urgent to develop technologically mature low-cost and low-energy-consumption CCUS technology implementing extensive large-scale integrated pilot projects.

Hydrogen is a critical energy carrier in the transition to sustainable energy but its properties such as high diffusivity wide flammability range and low ignition energy present unique safety challenges during transportation. This study aims to improve on-road hydrogen transport safety by developing a dynamic traffic-dependent risk assessment framework for both Compressed Gaseous Hydrogen (CGH₂) tube trailers and Liquid Hydrogen (LH₂). A key advancement in this study is the use of dynamic occupancy data capturing variations in traffic density throughout the day instead of relying on average traffic density to estimate ignition source distribution. Additionally a qualitative Hazard and Operability (HAZOP) study was conducted for a potential central distribution terminal in Fort Saskatchewan Alberta Canada to systematically identify process hazards during the loading of hydrogen on-road carriers. Results reveal that the ignition probability for minor CGH2 leaks significantly increases with road occupancy rising from 0.003 at 0.1% to 0.149 at 5% emphasizing the importance of scheduling transport during off-peak hours Vapor Cloud Explosions (VCE) from LH2 extend up to 257 meters compared to 122.42 meters for CGH₂ underscoring the need for stricter land-use planning in densely populated areas. The analysis suggests prioritizing lower-traffic rural routes which exhibit lower release frequencies (e.g. 1.80E-05 per year) over high-traffic urban routes with higher release frequencies (e.g. 6.47E-05 per year).

Even if the aviation sector only accounts for 2% of global energy-related CO2 emissions and is the most challenging sector to decarbonize. As aviation demand grows and the need for sustainable jet fuels becomes urgent green hydrogen could substitute conventional fossil fuels thereby enabling carbon-free flights. This study investigates a techno-economic analysis of onsite versus off-site green hydrogen supply chains. A case study at the Toulouse-Blagnac airport (Europe’s first station for the production and distribution of renewable hydrogen) in France is developed to meet commercial aviation's hydrogen fuel demand between 2025 and 2050. Demand of hydrogen is projected based on the trend of jet fuel consumption. First the cost of solar-based renewable electricity is estimated at the two green hydrogen production sites using levelized cost of electricity production. Second levelized cost of hydrogen (LCOH) is evaluated for three value chain scenarios: one on-site (Toulouse airport) and two off-site (Marseille) for gaseous and cryogenic transportation of liquid hydrogen (LH2). A relative cost advantage is shown for the off-site case with cryogenic truck transportation at LCOH of €9.43/kg.LH2. This study also reveals the importance of electricity price investment costs operation costs economies of scale and transportation distance in different scenarios.

MgH2 shows significant potential for a solid-state hydrogen storage medium due to the advantages of high hydrogen capacity excellent reversibility and low cost. However its large-scale application still requires overcoming significant thermodynamic and kinetic hurdles. Catalyst design and optimization enhancements are crucial for the hydrogen storage properties of MgH2 wherein single-atom catalysts characterized by their small size and high proportion of unsaturated coordination sites have recently demonstrated a significant advance and considerable promise in this regard. This review presents recent progress on state-of-the-art single-atom catalysts for enhancing MgH2 hydrogen storage examining both supported and unsupported catalyst types i.e. transition metal @ N-modified carbon materials and transition metal @ transition metal compounds and metallene-derived compounds and single-atom alloys respectively. We systematically discussed the single-atom catalysts in MgH2 hydrogen storage systems focusing on synthesis strategies characterization techniques catalytic mechanisms as well as existing challenges and future perspectives. We aimed to provide a comprehensive and cohesive understanding for researchers in the field and promote the development of single-atom catalysts and their significant optimization of the hydrogen storage performance of MgH2.

In the pursuit of establishing a sustainable fuel cell (FC) energy system this review highlights the necessity of examining the operational principles technical details environmental consequences and economic concerns collectively. By adopting an integrated approach the review research into various fuel cells types extending their applications beyond transportation and evaluating their potential for seamless integration into sustainable practices. A detailed analysis of the technical aspects including FC membranes performance and applications is presented. The environmental impact of hydrogen generation through fuel cell/electrolyzer is quantitatively assessed emphasizing a comparative emission footprint against traditional hydrogen generation methods. Economic considerations of fuel cell technology adoption are explored through an extensive examination of market growth and forecasts and investments into the FC systems. Some flagship commercial projects of FC technology are also discussed along with their future prospective. The article concludes with a thorough analysis of challenges associated with FC adoption encompassing membrane research performance hurdles infrastructure development and application-specific challenges. This all-round review serves as an indispensable tool for academicians and policymakers providing a directed and comprehensive FC perspective.

In the twenty-first century global energy consumption is rapidly increasing particularly in emerging nations hastening the depletion of fossil fuel reserves and emphasizing the vital need for sustainable and renewable energy sources. This study aims to analyze hybrid renewable energy systems (HRESs) that use solid waste to generate power focusing on difficulties linked to intermittent renewable sources using a techno-economic framework. Employing the HOMER Pro software prefeasibility analysis is performed to meet the energy needs of an Indian community. System architecture optimization depends on factors like minimizing net present cost (NPC) achieving the lowest cost of energy (COE) and maximizing renewable source utilization. This study evaluates the technical economic and environmental feasibility of a hybrid renewable energy system (HRES) comprising a 400-kW solar photovoltaic (PV) array a 100-kW wind turbine (WT) a 100-kW electrolyzer 918 number of 12V batteries a 200-kW converter a 200-kW reformer and a 15-kg hydrogen tank (H-tank). This optimal configuration has the lowest NPC of $26.8 million and COE of $4.32 per kilowatt-hour and a Renewable Fraction (RF) of 100%. It can provide a dependable power supply and satisfy 94% of the daily onsite load demand which is 1080 kilowatt-hours per day. The required electricity is sourced to load demand entirely from renewable energy at the given location. Additionally the study highlights the benefits of HRES in solid waste management considering technological advancements and regulatory frameworks. Furthermore sensitivity analysis is conducted to measure economic factors that influence HRES accounting for fluctuations in load demand project lifespan diesel fuel costs and interest rates. Installing an HRES custom-made to the local environmental conditions would provide a long-lasting reliable and cost-effective energy source. The results show that the optimal HRES system performs well and is a viable option for sustainable electrification in rural communities.

The study presents the development of a novel integrated wind-biomass energy system designed for sustainable urban development leveraging municipality waste and wind power energy sources. This innovative system is capable of producing multiple forms of energy including electricity cooling heat and hydrogen addressing the diverse energy needs of urban communities. It integrates advanced thermodynamic cycles like Kalina and water electrolysis via an alkaline electrolyzer. In addition the system uniquely combines power and refrigeration while utilizing landfills as an energy source. The designed system is thermodynamically modeled using the Engineering Equation Solver and process wise simulated by the Aspen Plus software to ensure better performance. By integrating advanced thermodynamic cycles such as the Kalina and combined power and refrigeration system the overall system is designed to maximize the utilization of biomass energy content and enhances overall performance. The thermodynamic analysis results reveal that the system achieved remarkable results with an energy efficiency of 67.60% and an exergy efficiency of 59.7% demonstrating its tangible performance compared to other standalone energy systems. The refrigeration system itself achieves an energetic COP of 5.41 and an exergetic COP of 1.7. Additionally the system's hydrogen production facilitated by an alkaline electrolyzer reaches a rate of 5.38 kg/h highlighting its potential to contribute to clean hydrogen energy solutions. Moreover the exergo-environmental assessment shows that the system is environmentally friendly. The cost assessment shows that the system reaches profitability in 7 years and demonstrates growth achieving a substantial NPV of 192.39 million by 30 years highlighting its long-term financial viability.

Hydrogen is a promising carbon-free energy carrier for large-scale applications yet its adoption faces unique safety challenges. Microscopic physicochemical properties such as high diffusivity low ignition energy and distinct chemical pathways alter the safety of hydrogen systems. Analyzing the HIAD 2.0 incident database an occurrence-based review of past hydrogen incidents shows that 59% arise from general industrial failures common to other hydrocarbon carrier systems. Of the remaining 41% only 15% are unequivocally linked to the fuel’s unique properties. This study systematically isolates hazards driven by hydrogen’s intrinsic properties by filtering out confounding factors and provides an original clear characterization of the different failure mechanisms of hydrogen systems. These hydrogen-specific cases are often poorly described limiting their contribution to safety strategies and regulations improvement. A case study on pipeline failures illustrates how distinguishing hydrogen-specific hazards supports targeted risk mitigation. The findings highlight the need for evidence-based regulation over broadly precautionary approaches.

The teams sits down with Johannah Christensen to discuss regulatory policies and risk mitigation for vessel owners switching to green fuels and what we can do to encourage that jump as well as ensure a Just Transition.

The podcast can be found on their website.

Hydrogen-fueled Internal Combustion Engines (H2-ICEs) are typically operated with lean mixtures to minimize NOx emissions and reduce the risk of abnormal combustion events. Due to hydrogen’s low Lewis number premixed hydrogen-air flames in lean conditions exhibit strong thermodiffusive instabilities which make the numerical simulation of the combustion process particularly challenging. Indeed the intensity of these instabilities is significantly influenced by thermodynamic parameters – such as mixture temperature pressure and dilution rate – resulting in substantial variations in combustion behaviour across different operating conditions. Therefore they have to be properly considered not only to ensure model robustness but also to improve model accuracy over a wider range of operations. In this study the combustion process in a Direct Injection H2-ICE was analyzed using 3D-CFD simulations relying on a flamelet-based combustion model. Two sets of lookup flame speed maps were defined: laminar flame speed (SL) maps derived from standard 1D-CFD simulations in homogeneous reactor and freely propagating flame speed (SM) maps which account for the effects of thermodiffusive instabilities. The model that uses SL maps required the recalibration of some combustion model parameters when changing the dilution rate to ensure consistency with experimental data. Instead the model relying on SM maps featured a noticeable accuracy across different air-to-fuel ratios without the need for recalibration any combustion model parameter highlighting the key role of thermodiffusive flame instabilities on the combustion process. Based on these findings the impact of such instabilities was evaluated throughout the entire combustion process from both global and local perspectives. The relevance of thermodiffusive instabilities was observed to increase with the air-to-fuel ratio thereby enhancing combustion speed in leaner mixtures. Additionally the implementation of thermodiffusive instabilities was found to affect also preferred direction of flame propagation as stronger instabilities were identified in the leanest and low-temperature portions of the flame front. Novelty and significance This study addresses a critical knowledge gap regarding the role of thermodiffusive flame instabilities in accurately replicating the combustion process of a direct-injection internal combustion engine within a RANS simulation framework. Indeed while these instabilities have been shown to significantly enhance the mixture consumption rate in quiescent environments at low to moderate pressures and temperatures particularly in lean mixtures their impact on the burn rate under engine-like conditions has not yet been systematically investigated to the best of the authors’ knowledge. This work provides a comprehensive analysis of the significance of these instabilities in the combustion process of a direct-injection hydrogen internal combustion engine. The analysis is conducted from both a global perspective assessing their overall influence on the combustion process and a local perspective examining how they alter flame front characteristics when incorporated into the model.

Alternative fuel opportunities can satisfy energy security and reduce carbon emissions. In this regard the hydrogen fuel is derived from the source of environmental pollutants like sewage and algae wastewater through hydrothermal gasification technique using a KOH catalyst with varied gasification process parameters of duration and temperature of 6–30 min and 500-800 ◦C. The novelty of the work is to identify the optimum gasification process parameter for obtaining the maximum hydrogen yield using a KOH catalyst as an alternative fuel for agricultural engine applications. Influences of gasification processing time and temperature on H2 selectivity Carbon gasification efficiency (CE) Lower heating value (LHV) Hydrogen yield potential (HYP) and gasification efficiency (GE) were studied. Its results showed that the gasifier operated at 800 ◦C for 30 min offering maximum hydrogen yield (26 mol/kg) and gasification efficiency (58 %). The synthesized H2 was an alternative fuel blended with diesel fuel/TiO2 nanoparticles. It was experimentally studied using an internal combustion engine. Influences of H2 on engine perfor mance like brake-specific fuel consumption brake thermal efficiency and emission performances were measured and compared with diesel fuel. The results showed that DH20T has the least (420g/kWh) brake-specific fuel consumption (BSFC) and superior brake thermal efficiency of about 25.2 %. The emission results revealed that the DH20T blend showed the NOX value increased by almost 10.97 % compared to diesel fuel whereas the CO UHC and smoke values reduced by roughly 31.25 28.34 and 42.35 %. The optimum fuel blend (DH20T) result is rec ommended for agricultural engine applications.

Climate change and global warming concerns promote interest in alternative fuels especially zero-carbon fuels like hydrogen. Modifying existing combustion engines for dual-fuel operation can decrease emissions of vehicles that are already on the road. The procedure of a deep learning-based model predictive control as a machine learning implementation practical for complex nonlinear systems with input and state constraints has been developed and tested on a hydrogen/diesel dual-fuel (HDDF) engine application. A nonlinear model predictive controller (NMPC) utilizing a deep neural network (DNN) process model is proposed to control the injected hydrogen and diesel. This DNN model has eight inputs and four outputs and has a short computational time compared to the physics-based model. The architecture and hyperparameters of the DNN model of the HDDF process are optimized through a two-stage Bayesian optimization to achieve high accuracy while minimizing the complexity of the model described. The final DNN architecture has two hidden layers with 31 and 23 neurons. A modified engine capable of HDDF operation is compared to standard diesel operation to evaluate the engine performance and emissions. During experimental engine testing the controller required an average computational time of 2 ms per cycle on a low-cost processor satisfying the real-time requirements and was faster than recurrent networks. The control performance of the DNN-NMPC for the HDDF engine showed a mean absolute error of 0.19 bar in load tracking while maximizing average hydrogen energy share (68%) and reducing emissions. Specifically the particulate matter emissions decrease by 87% compared to diesel operation.

An increasing demand for energy coupled with rising pollution levels is driving the search for environmentally clean alternative energy resources to replace fossil fuels. Hydrogen has emerged as a promising clean energy carrier and raw material for various applications. However its environmental benefits depend on sustainable production methods. The rapid development of nanomaterials (NMs) has opened new avenues for the conversion and utilization of renewable energy (RE). NMs are becoming increasingly important in addressing challenges related to hydrogen (H₂) generation. This review provides an overview of current advancements in H₂ production from biomass via thermochemical (TC) and biological (BL) processes including associated costs and explores the applications of nanomaterials in these methods. Research indicates that biological hydrogen (BL-H₂) production remains costly. The challenges associated with the TC conversion process are examined along with potential strategies for improvement. Finally the technical and economic obstacles that must be overcome before hydrogen can be widely adopted as a fuel are discussed.

As Europe transitions away from natural gas dependency and accelerates its adoption of renewable energy 12 green hydrogen has emerged as a key energy carrier for industrial and automotive applications. Similarly plans 13 to export hydrogen and ammonia from resource-rich regions like Australia and the Middle East to major importers 14 such as Japan and South Korea underline the global commitment to decarbonization. Central to these efforts is 15 the advancement of efficient hydrogen compression technologies which are essential for establishing a 16 sustainable hydrogen supply chain. This study provides a comparative analysis of two key hydrogen compression 17 technologies categorized under positive displacement and non-mechanical systems. The evaluation emphasizes 18 the technical characteristics energy efficiency and potential applications of these systems in the emerging 19 hydrogen economy. Special focus is placed on electric motor-driven compressors which integrate advanced 20 materials and optimized designs to enhance efficiency and minimize energy consumption. By addressing the gap 21 in comparative evaluations this paper offers insights into the performance and sustainability of these technologies 22 contributing to the development of cost-effective and reliable hydrogen supply systems.

The FuelEU Maritime Regulation part of the European Union’s (EU’s) Fit for 55 initiative aims to achieve significant reductions in greenhouse gas (GHG) emissions within the maritime sector. This study assesses the feasibility of alternative fuels for the Estonian pilot fleet using a Well-to-Wake (WtW) life cycle assessment (LCA) methodology. Operational data from 18 vessels sourced from the Estonian State Fleet’s records were analyzed including technical specifications fuel consumption patterns and operational scenarios. The study focused on marine diesel oil (MDO) biomethane hydrogen biodiesel ammonia and hydrotreated vegetable oil (HVO) each presenting distinct trade-offs. Biomethane achieved a 59% GHG emissions reduction but required a volumetric storage capacity up to 353% higher compared to MDO. Biodiesel reduced GHG emissions by 41.2% offering moderate compatibility with existing systems while requiring up to 23% larger storage volumes. HVO demonstrated a 43.6% emissions reduction with seamless integration into existing marine engines. Ammonia showed strong potential for long-term decarbonization but its adoption is hindered by low energy density and complex storage requirements. This research underscores the importance of a holistic evaluation of alternative fuels taking into account technical economic and environmental factors specific to regional and operational contexts. The findings offer a quantitative basis for policymakers and maritime stakeholders to develop effective decarbonization strategies for the Baltic Sea region.

This study explores the potential of renewable seafood shell waste for sustainable energy conversion and longterm storage particularly for isolated communities. Despite its rich chitin and protein composition seafood shell waste is often neglected. The research evaluates and compares three advanced gasification technologies: biomass gasification plasma gasification and chemical looping to convert seafood shell waste into syngas and H2. The study uses validated Aspen Plus models to optimize feedstock blending ratios and operational parameters. Results show that feedstocks high in lobster and shrimp shells yield higher H2 outputs and improved syngas quality compared to clam-dominated blends. For instance biomass gasification at 1200 ◦C yielded approximately 500 kg/h of H2 from pure lobster or shrimp feeds while plasma gasification at 4500 ◦C achieved yields near 730 kg/ h. Plasma gasification when integrated with fuel cell conversion and heat recovery systems can generate over 10000 kWh during a 6-hour peak period enough to power over 1100 single-detached homes. Its levelized cost of hydrogen (LCOH) varies from $5.72-$8.37/kg H2 making it less expensive than chemical looping and biomass gasification. Plasma gasification also has the lowest global warming potential (GWP) at 6 kg CO2e/kg H2. Combining plasma gasification with carbon capture and storage may reduce GWP to 0.3 kg CO2e/kg H2 and can be further explored. These findings underscore the technical and economic viability of converting seafood shell renewable waste into H2 advancing sustainable energy transitions and supporting net-zero goals.

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.

The growing interest in hydrogen as an alternative fuel has stimulated research into methods that enable the global shift to sustainable green energy. One promising pathway is the production of green hydrogen via electrolysis particularly when coupled with renewable energy sources like solar power. Integrating a proton exchange membrane (PEM) electrolyzer with solar energy can aid this transition. Using treated sewage effluent instead of deionized water can make the process more economical and sustainable. Thus the objective of this research is to demonstrate that an integrated electrolysis-water treatmentsolar energy system can be a viable candidate for producing green hydrogen in a sustainable manner. This study assesses different combinations of water pretreatment (RO and UF) and solar energy input (PV ST and PTC) evaluating their techno-economic feasibility efficiencies environmental impact and sustainability. The study shows that CSP scenarios have the highest CAPEX roughly fourfold that of PV cases and sevenfold that of national grid cases. Using solar energy sources like PV ST and PTC results in high material efficiency (94.87%) and environmental efficiency (98.34%) while also reducing CO2 emissions by approximately 88% compared to the national grid. The process’s economic sustainability averages 57% but it could reach 90% if hydrogen production costs fall to $2.08-$2.27 per kg. The outcome of this study is to provide a green hydrogen production pathway that is technically feasible environmentally sustainable and economically viable.