Search Results (63)

The rally to mitigate growing carbon emissions and climate change necessitates decarbonization strategies, with hydrogen emerging as a key candidate option across multiple sectors. This review examines the current state of the hydrogen economy, including production, implementation, and associated risks. Hydrogen’s versatility in industry, transportation, and energy storage is highlighted, alongside the challenges of transitioning from fossil fuel-based production. It explores the current state of hydrogen technologies, differentiating between green, blue, and gray hydrogen production methods, and highlights advancements in production techniques like thermochemical water splitting. Key findings show that while green hydrogen offers the cleanest pathway, high production costs and infrastructure limitations remain significant barriers to widespread adoption. This study also addresses safety concerns and public perception, emphasizing the need for robust risk assessment methodologies and management approaches. Furthermore, this paper underscores the importance of technological innovations, such as high-temperature electrolysis and synergies with renewable energy sources, to enhance efficiency and sustainability. Policy recommendations include financial incentives, regulatory frameworks, and international cooperation to accelerate hydrogen adoption and balance its development with other low-carbon solutions. Full article

The transformation of waste plastics into hydrogen and functional carbon (C) materials represents a promising pathway for achieving both resource recycling and the production of value-added products. Owing to their tunable physicochemical properties, plastic-derived carbons have attracted significant attention in electrochemical energy storage applications. Various C nanostructures, including graphene, porous C, hard C, and C nanotubes (CNTs), can be generated from discarded plastics through thermochemical processes. The electrochemical performance of these materials is closely governed by their structural characteristics, such as pore architecture, specific surface area, heteroatom doping, surface functionalities, and dimensional morphology. This review aims to provide a comprehensive and systematic overview of the conversion of waste plastics into functional C nanomaterials via thermochemical routes, particularly catalytic pyrolysis and carbonization. The resulting C nanostructures are systematically categorized based on their dimensional architectures (0D, 1D, 2D, and 3D) and comparatively analyzed in terms of their structural features and electrochemical performance. Emphasis is placed on the transformation of diverse plastic feedstocks into high-value C materials with tailored dimensional architectures, including graphene, CNTs, C nanospheres, C nanosheets, porous carbons, and their composites. Furthermore, recent progress and critical challenges in utilizing these materials for electrochemical energy storage systems, such as supercapacitors and rechargeable batteries (Li-ion, Na-ion, K-ion, Li-S, and Zn-air), are discussed. Distinct from previous reports, this review highlights the correlation between thermochemical processing strategies, resulting structural features, and electrochemical performance, providing new insights into the rational design of high-performance C materials. These findings are expected to facilitate the advancement of sustainable energy storage technologies while contributing to effective plastic waste valorization. Full article

The water–energy–carbon (WEC) nexus provides a systems framework for minimizing trade-offs among water security, energy reliability, and carbon mitigation. Within this framework, waste-derived biochar catalysts offer a circular pathway that simultaneously valorizes residues, reduces process energy demand, and supports carbon management through stable carbon storage and catalytic co-benefits. This review consolidates recent advances in biochar-based catalysts engineered from agricultural, industrial, municipal, and sludge-derived wastes, highlighting how feedstock selection and thermochemical processing, namely pyrolysis, hydrothermal carbonization (HTC), and torrefaction, as well as activation and post-modification (heteroatom doping and metal/metal-oxide incorporation) govern structure–property–performance relationships. The synthesized catalysts have been widely applied in water and wastewater treatment, including adsorption–advanced oxidation process (AOP) hybrids, Fenton-like systems, peroxydisulfate/persulfate (PS) and peroxymonosulfate (PMS) activation, photocatalysis, and the removal of emerging contaminants. They have also demonstrated strong potential in energy conversion processes such as the hydrogen evolution reaction (HER), oxygen reduction and evolution reactions (ORR/OER), biomass reforming, and carbon dioxide (CO₂) conversion. In addition, these materials contribute to carbon management through sequestration pathways, avoided emissions, and life cycle assessment (LCA)-based sustainability evaluations. Finally, we propose a WEC-aligned design roadmap integrating techno-economic analysis (TEA), LCA, and scale-up considerations to guide next-generation biochar catalysts toward robust performance in real matrices and deployment-ready systems. Full article

Processes for generating clean hydrogen from waste plastics through thermochemical methods such as pyrolysis and gasification are a promising solution for both waste management and clean energy initiatives. Then, this derived hydrogen powers the fuel cell, which produces electricity that can be directly fed to charge electric vehicles (EVs). Although this complex process has many challenges related to energy efficiency during the conversion processes—starting from the generation of hydrogen from thermochemical processes and hydrogen storage and followed by fueling the fuel cells and charging EV infrastructure—the simplistic conceptual modeling developed for this research demonstrates how an ecosystem of such processes can be made feasible commercially. Clean hydrogen generated using known techniques reported in the literature is promising for commercialization, but harnessing hydrogen from plastics offers additional benefits, such as reducing greenhouse gas (GHG) emissions. Overall, the feasibility of clean hydrogen using this methodology is not limited by potential cost inefficiencies, especially when savings from GHG emissions reduction are taken into account. EVs have become commercially viable thanks to high-energy-density Li-ion batteries. And therefore, research continues to optimize charging performance through the integration of renewable energy and battery storage systems. This study examines another potential of clean hydrogen: its use as a power source in grids, especially V-2-G (vehicle-to-grid) systems. Additionally, direct current (DC) power from a fuel cell powers an EV charger at DC input voltages for e-ambulances. In particular, this designed system operates on DC voltages throughout the power system, combining high-voltage direct current (HVDC) lines, renewable energy sources, DC-DC converters, DC EV chargers, and other supporting components. The literature review identified gaps in plastics production, waste management, and processes for converting them into useful energy. The presented model is a stepping stone towards a novel, innovative process for clean hydrogen production to power electric vehicle charging infrastructure for emergency response systems in healthcare, thereby improving public safety. The limitations of the study would be governed by the effective establishment of locations where waste management services are performed (for example, landfills) and adoption by local government authorities with deregulated power systems. Full article

Hydrogen is emerging as a key energy carrier in the transition to a low-carbon economy. This study reviews blue and green hydrogen, analysing their production technologies, environmental impacts, economic viability and global deployment trends. Blue hydrogen, derived from natural gas, coal or biomass with carbon capture, utilisation and storage, offers a transitional pathway by reducing emissions relative to unabated fossil routes, but its benefits depend on high CO₂ capture efficiencies and strict methane leakage control. Green hydrogen, produced via renewable-powered electrolysis and advanced thermochemical, photochemical and photoelectrochemical methods, represents the most sustainable long-term solution, though it is currently limited by cost and scale. This comparative assessment shows that green hydrogen’s production emissions, in the range of 0.67 kgCO-eq/kgH to 1.74 kgCO₂-eq/kgH₂, are substantially lower than those of blue hydrogen, in the range of 1.21 kgCO₂-eq/kgH₂ to 4.56 kgCO₂-eq/kgH₂, reinforcing its alignment with climate neutrality goals. Global production remains below 1% from low-emission sources, yet momentum is growing, with renewable-rich regions investing in large-scale electrolysers. A long short-term memory forecast suggests that blue hydrogen will dominate in the short term, but green hydrogen will surpass it around 2042. Together, both pathways are essential, blue hydrogen as a bridging option and green hydrogen as the foundation of a sustainable hydrogen economy. Full article

Biomethane plays a key role in the green transition, offering a renewable, carbon-neutral substitute for natural gas while enabling the storage and use of intermittent renewable energy. This work presents a techno-economic assessment of biomethane production through the Power-to-Biomethane concept, which combines electrolytic hydrogen from renewable electricity with the direct catalytic methanation of raw biogas from anaerobic digestion. The main objective of this study is to identify the optimal plant size and configuration, taking into account the different operational management strategies of the system’s constituting units. The analysis integrates thermochemical modeling with a techno-economic optimization procedure. Three different configurations for renewable energy production, photovoltaic-based, wind-based, and hybrid photovoltaic–wind, were evaluated for a case study in Southern Italy. Results show that the hybrid configuration provides the best techno-economic balance, achieving the highest annual biomethane output (≈2288 t) and the lowest levelized cost of biomethane (EUR 97.4/MWh). While current biomethane production costs exceed natural gas prices, the proposed pathway represents a viable long-term solution for renewable integration and climate-neutral gas supply. Full article

The urgent need to reduce greenhouse gas emissions and shift towards renewable energy has increased attention on biochar as a viable negative emission strategy. This review assesses the potential of biochar produced from organic and waste biomass via thermochemical processes—including pyrolysis, gasification, and hydrothermal carbonization—to address climate and energy challenges. Recent advances in biochar production are critically examined, highlighting how process design controls improve key properties such as carbon stability, atomic ratios, porosity, and energy density. These factors influence biochar’s performance in carbon sequestration and its utility across industrial sectors, ranging from agriculture and construction to energy generation and carbon capture systems. Results indicate that large-scale adoption of biochar could lower carbon emissions, enhance soil fertility, and produce renewable fuels like hydrogen, while also benefiting circular economy initiatives. However, obstacles remain, including economic costs, feedstock logistics, process optimization, and potential environmental or social impacts. This review underscores that unlocking biochar’s full promise will require interdisciplinary research, robust quality standards, and supportive policies. With integrated efforts across science, industry, and policy, biochar can serve as an effective and sustainable technology for emission reduction and contribute significantly to global carbon neutrality goals. Full article

Fuel cell electric vehicles (FCEVs) offer a promising solution for energy saving and emission reduction in transportation. However, several challenges must be addressed for their application. This study conducts a full life cycle assessment (LCA) of FCEVs, dividing it into the fuel cycle and vehicle cycle to separately assess energy consumption (EC) and emissions. The fuel cycle examined 18 hydrogen production–storage–transport pathways, while the vehicle cycle evaluates energy use and emissions associated with vehicle component production, assembly, disposal, battery production, and fluid consumption. Based on the GREET database, total energy consumption and emissions over a lifetime were calculated. Five environmental impact indicators were used for evaluation, and a comprehensive environmental assessment (CEA) indicator was established for different scenarios. Results indicate that nuclear thermochemical water splitting is the best hydrogen production method, and pipeline transportation is the most efficient for hydrogen transport. Additionally, water electrolysis for hydrogen production is only practical when paired with renewable energy. The study also identified that the Hydrogen production method, “Body”, “Proton Exchange Membrane Fuel Cells (PEMFCs) System”, “Chassis”, “Hydrogen Storage System” and lifetime significantly impact energy consumption and emissions. These stages or products represent high-impact leverage points for enhancing the lifecycle sustainability evaluation of FCEVs. Full article

Hydrogen is critical for achieving carbon neutrality as a clean energy source. However, its low ambient energy density poses challenges for storage, making efficient and safe hydrogen storage a bottleneck. Metal hydride-based solid-state hydrogen storage has emerged as a promising solution due to its high energy density, low operating pressure, and safety. In this work, the thermodynamic and kinetic characteristics of the hydrogenation and dehydrogenation processes are investigated and analyzed in detail, and the effects of initial conditions on the thermochemical hydrogen storage reactor are discussed. Multiphysics field modeling of the magnesium-based hydrogen storage tank was conducted to analyze the reaction processes. Distributions of temperature and reaction rate in the reactor and temperature and pressure during the hydrogen loading process were discussed. Radially, wall-adjacent regions rapidly dissipate heat with short reaction times, while the central area warms into a thermal plateau. Inward cooling propagation shortens the plateau, homogenizing temperatures—reflecting inward-to-outward thermal diffusion and exothermic attenuation, alongside a reaction rate peak migrating from edge to center. Axially, initial uniformity transitions to bottom-up thermal expansion after 60 min, with sustained high top temperatures showing nonlinear decay under $∆$t = 20 min intervals, where cooling rates monotonically accelerate. The greater the hydrogen pressure, the shorter the period of the temperature rise and the steeper the curve, while lower initial temperatures preserve local maxima but shorten plateaus and cooling time via enhanced thermal gradients. Full article

Nuclear energy cogeneration, which integrates electricity generation with thermal energy utilization, presents a transformative pathway for enhancing energy efficiency and decarbonizing industrial and urban sectors. This comprehensive review synthesizes advancements in technological stratification, economic modeling, and sectoral practices to evaluate the viability of nuclear cogeneration as a cornerstone of low-carbon energy transitions. By categorizing applications based on temperature requirements (low: <250 °C, medium: 250–550 °C, high: >550 °C), the study highlights the adaptability of reactor technologies, including light water reactors (LWRs), high-temperature gas-cooled reactors (HTGRs), and molten salt reactors (MSRs), to sector-specific demands. Key findings reveal that nuclear cogeneration systems achieve thermal efficiencies exceeding 80% in low-temperature applications and reduce CO₂ emissions by 1.5–2.5 million tons annually per reactor by displacing fossil fuel-based heat sources. Economic analyses emphasize the critical role of cost allocation methodologies, with exergy-based approaches reducing levelized costs by 18% in high-temperature applications. Policy instruments, such as carbon pricing, value-added tax (VAT) exemptions, and subsidized loans, enhance project viability, elevating net present values by 25–40% for district heating systems. Case studies from Finland, China, and Canada demonstrate operational successes, including 30% emission reductions in oil sands processing and hydrogen production costs as low as USD 3–5/kg via thermochemical cycles. Hybrid nuclear–renewable systems further stabilize energy supply, reducing the levelized cost of heat by 18%. The review underscores the necessity of integrating Generation IV reactors, thermal storage, and policy alignment to unlock nuclear cogeneration’s full potential in achieving global decarbonization and energy security goals. Full article

The application of environmentally friendly technologies, such as phytoremediation, for contaminated soil remediation and biofuel generation should be one of the goals of sustainable development. Phytoremediation is based on the use of plants and their associated microorganisms to clean contaminated soils, resulting in a positive impact on the environment and the production of biomass that can be utilized for biofuel production. Combining phytoremediation with advanced thermochemical conversion technologies like thermo-catalytic reforming process (TCR) allows for the production of high-quality biochar, bio-oil comparable to fossil crude oil, and hydrogen-rich syngas. This study presents a full-scale phytoremediation experiment conducted at a former oil storage site using energy crops like Jerusalem artichokes (Helianthus tuberosus), where the biomass was later converted into biofuel and other by-products using lab-scale technology. Significant and promising results were obtained: (i) within two years, the initial total petroleum hydrocarbons (TPH) contamination level (698 mg/kg) was reduced to a permissible level (146 mg/kg); (ii) the yield of the harvested Jerusalem artichoke biomass reached 18.3 t/ha dry weight; (iii) the thermochemical conversion produced high-quality products, such as a thermally stable oil a higher heating value (HHV) of 33.85 MJ/kg; (iv) the two-year phytoremediation costs for the rejuvenated soil amounted to3.75 EUR/t. Full article

Hydrogen has emerged as a critical energy carrier for achieving global decarbonization and supporting a sustainable energy future. This review explores key advancements in hydrogen production technologies, including electrolysis, biomass gasification, and thermochemical processes, alongside innovations in storage methods like metal hydrides and liquid organic hydrogen carriers (LOHCs). Despite its promise, challenges such as high production costs, scalability issues, and safety concerns persist. Biomass gasification stands out for its dual benefits of waste management and carbon neutrality yet hurdles like feedstock variability and energy efficiency need further attention. This review also identifies opportunities for improvement, such as developing cost-effective catalysts and hybrid storage systems, while emphasizing future research on improving storage efficiency and tackling production bottlenecks. By addressing these challenges, hydrogen can play a central role in the global transition to cleaner energy systems. Full article

This paper focuses on the critical role of long-duration energy storage (LDES) technologies in facilitating renewable energy integration and achieving carbon neutrality. It presents a systematic review of four primary categories: mechanical energy storage, chemical energy storage, electrochemical energy storage, and thermal energy storage. The study begins by analyzing the technical advantages and geographical constraints of pumped hydro energy storage (PHES) and compressed air energy storage (CAES) in high-capacity applications. It then explores the potential of hydrogen and synthetic fuels for long-duration clean energy storage. The section on electrochemical energy storage highlights the high energy density and flexible scalability of lithium-ion batteries and redox flow batteries. Finally, the paper evaluates innovative advancements in large-scale thermal energy storage technologies, including sensible heat storage, latent heat storage, and thermochemical heat storage. By comparing the performance metrics, application scenarios, and development prospects of various energy storage technologies, this work provides theoretical support and practical insights for maximizing renewable energy utilization and driving the sustainable transformation of global energy systems. Full article

This study assesses and characterizes six woody biomass (WB) species commonly harvested in the Republic of Congo: Millettia laurentii (WB1), Millettia eetveldeana (WB2), Hymenocardia ulmoides (WB3), Markhamia tomentosa (WB4), Pentaclethra eetveldeana (WB5), and Hymenocardia acida (WB6). Characterization was performed using proximate analysis with a Thermo Gravimetric Analyser (TGA), ultimate analysis with a CHNS Analyser, higher heating value (HHV) determination, metal content analysis by X-ray fluorescence (XRF), and aboveground biomass (AGB) estimation. The proximate analysis results showed that volatile matter varied between 74.6% and 77.3%, while the ultimate analysis indicated that carbon content ranged from 43% to 46%, with low nitrogen content. XRF analysis revealed low levels of heavy metals in all samples. The HHV results, using three models (Dulong’s equation, Friedl, and proximate analysis), showed higher values with Friedl’s method (17.3–18.2 MJ/kg) and proximate analysis (15.26–19.23 MJ/kg) compared to Dulong’s equation (13.9–14.9 MJ/kg). Savannah biomass (WB6) exhibited high AGB (7.28 t), 14.55 t/ha, and carbon stock (7.28 t). Compared to forest biomass, savannah biomass presents a higher potential for bioenergy production. Minimal statistical analysis of wood biomass showed that parameters such as volatile matter (VM), carbon (C), hydrogen (H), and calculated HHV have low variability, suggesting the biomass is relatively homogeneous. However, moisture and nitrogen showed significant standard deviations, indicating variability in storage conditions or sample nature. Statistical analysis of forest biomass estimation revealed different mean values for diameter, AGB (t and t/ha), and carbon stock, with high standard deviations, indicating a heterogeneous forest with both young and mature trees. These analyses and estimates indicate that these WB species are suitable for biofuel and bioenergy production using gasification, pyrolysis, and combustion processes. Among these thermochemical processes, gasification is the most efficient compared to combustion and pyrolysis. Full article

In this paper, a novel mixed Tutton salt (K_0.86Na_0.14)₂Ni(SO₄)₂(H₂O)₆ was successfully synthesized as a single crystal and evaluated as a thermochemical heat storage material. Its thermal and thermochemical properties were correlated with the structure, which was determined by powder X-ray diffraction using the Le Bail and Rietveld methods. The elemental ratio between the K⁺ and Na⁺ monovalent cations was established by energy-dispersive X-ray spectroscopy. Similar compounds such as Na₂Ni(SO₄)₂(H₂O)₄ and K₂Ni(SO₄)₂(H₂O)₆ were also synthesized and used for structural comparisons. The (K_0.86Na_0.14)₂Ni(SO₄)₂(H₂O)₆ salt crystallizes in monoclinic symmetry with the P2₁/c-space group, typical of hexahydrate crystals from the Tutton salt family. The lattice parameters closely resemble those of K₂Ni(SO₄)₂(H₂O)₆. A comprehensive analysis of the intermolecular contacts, based on Hirshfeld surfaces and 2D fingerprint mappings, revealed that the primary interactions are hydrogen bonds (H···O/O···H) and ion-dipole interactions (K/Na···O/O···Na/K). The unit cell exhibits minimal void space, accounting for only 0.2%, indicative of strong atomic packing. The intermolecular molecular and atomic packing are important factors influencing crystal lattice stabilization and thermal energy supplied to release crystallographic H₂O. The thermal stability of mixed Tutton salt ranges from 300 K to 365 K. Under the dehydration of its six H₂O molecules, the dehydration reaction enthalpy reaches 349.8 kJ/mol, yielding a thermochemical energy storage density of 1.79 GJ/m³. With an H₂O desorption temperature ≤393 K and a high energy storage density ≥1.3 GJ/m³ (criteria established for applications at the domestic level), the (K_0.86Na_0.14)₂Ni(SO₄)₂(H₂O)₆ shows potential as a thermochemical material for small-sized heat batteries. Full article