Green hydrogen: A key energy carrier replacing fossil fuels across multiple sectors

Urgent action is required to limit the increase in global temperatures. While mitigation efforts are primarily directed at transitioning away from fossil fuels, given their overwhelming contribution to greenhouse gas emissions, infrastructural change is slow to effect. Thus, behavioural changes, which can be effected rapidly, are also critical. To limit healthcare-related emissions, a widespread transition away from pressurised metered-dose inhalers (pMDIs), containing hydrofluorocarbons with high global warming potential (GWP), to dry powder inhalers (DPIs) with minimal GWP, has been proposed. This paper discusses whether the stated grounds for this transition are robust and are proportionate to the potential environmental gain and, while not to be ignored, whether a greater emphasis should be placed upon other measures that may have a greater impact.

ABSTRACT Uncertainty regarding sustainability has become a central challenge for advanced economies, eroding policy credibility, discouraging long-term investment, and heightening systemic risk. The United States illustrates this contradiction: it leads globally in technological innovation but remains heavily dependent on fossil fuels and constrained by decentralized governance. This study provides the first empirical assessment of U.S. sustainability uncertainty using quarterly data from 2003Q1–2022Q4. Employing wavelet quantile regression, wavelet quantile correlation, and quantile-on-quantile Granger causality, the analysis captures nonlinear, asymmetric, and scale-dependent dynamics often missed by standard econometric approaches. Results reveal that renewable energy transition and environmental governance heighten uncertainty in median and stable states, reflecting transitional frictions and institutional volatility. Technological innovation exerts mixed effects – reducing uncertainty under stable conditions but amplifying it in turbulent periods. Digital inclusion consistently reduces uncertainty, especially in high states, underscoring its role as a resilience-enhancing factor. Robustness checks using Kernel Regularized Quantile Regression confirm the validity of these findings. Policy implications emphasize the need for coherent governance, smoother energy transitions, balanced innovation regulation, and broader digital access. Together, these measures can convert volatility into resilience, enabling the U.S. to pair technological leadership with sustainable stability among advanced economies.

This is the absence of accountability between massive carbon emissions by industrial activities and the reported climate damage, which is one of the most impactful governance failures of modern times. Although the scientific evidence of most anthropogenic greenhouse gas emissions can be traced to a few identifiable producers of fossil fuels, the so-called carbon majors have theoretically immature and practically inadequate legal mechanisms through which the afflicted communities could seek redress, and have been fragmented. The article fills a key theoretical gap in the current body of literature: the literature on attribution science, climate litigation, corporate accountability, and climate governance has proceeded to develop individually, but no single theoretical model has ever brought together these four strands into a consistent accountability structure of emitter accountability. This article creates such a framework by relying on a systematic conceptual review of peer-reviewed scholarship in environmental law, climate science, governance theory, and tort doctrine. It is theorized that, when incorporated with the changing legal standards in causation and corporate knowledge-liability theory and climate governance theory, climate attribution science facilitates the creation of a plausible and analytically sound attribution chain between large emitters and reported climate damage and actionable claims to remedy. The article connotes four conceptual findings: causal-legal accountability chain; the typology of legal barriers and the theoretical resolutions; the nexus of corporate knowledge-deception-liability; and the reparative architecture in loss and damage with legal redress. These results are pulled together into a coherent and multi-strand theoretical model of emitter accountability arranged into four analytically separate strands of scientific accountability based on attribution, legal accountability based on tort and human rights, moral accountability based on the knowledge-deception nexus, and governance accountability based on litigation as a regulatory tool. With the rising development of attribution science and increasing judicial faith in probabilistic causal evidence, attribution litigation targeting climate change has an opportunity to rapidly become not just a fringe enforcement tool, but a structural-level implementative instrument of climate accountability with implications to both legal science and climate justice movement, and global regulation design.

Abstract The international community faces a conundrum. Without more ambitious action to curtail fossil fuel production, climate goals are impossible to realize. To date, an emerging array of minilateral international governance initiatives has promoted cooperation to reduce support to fossil fuels, through export finance and subsidies and through voluntary commitments to forgo fossil fuel reserves. However, a just transition away from fossil fuels will require more multilateral responses to address challenges such as uneven capacity to diversify economies, differential obligations to move away from fossil fuels based on historical patterns of consumption and the financial constraints which inhibit many states from reducing their fossil fuel dependence. Such a move will be fiercely resisted by fossil fuel-dependent powers. This article explores the tensions between the need for an orderly and just transition but one that is simultaneously able to disrupt incumbent forms of power currently resisting measures to cut the supply of fossil fuels, before assessing potential pathways forward. A growing number of states now recognize the need for global oversight and regulation of fossil fuel production, and they are starting to articulate what form a response might take. This article takes stock of such efforts and explores future political and institutional pathways towards a more orderly and just exit from fossil fuels. It argues that, while minilateral ‘club’ responses create important momentum, ultimately a multilateral agreement will be necessary to address the competing goals, diverse interests and different dimensions of a just transition.

Abstract Driven by rising global energy demand and environmental concerns over fossil fuels, photocatalytic water splitting for solar-driven hydrogen production has gained prominence. Herein, we propose a novel GeC/B 2 SSe van der Waals (vdW) heterostructure. Employing the quantum ESPRESSO code based on density functional theory (DFT), combined with the HSE06 hybrid functional and DFT-D3 van der Waals correction, we conduct a comprehensive evaluation of its structural, electronic, optical, and transport properties, alongside its strain-tunable photocatalytic behaviour. The heterostructure exhibits only 3.75% lattice mismatch and is stabilized by weak vdW interactions, ensuring energetic, dynamic, and thermodynamic stability at room temperature. It is an indirect bandgap semiconductor (2.64 eV) with a Type-II band alignment, enabling spatial charge separation. A built-in interfacial electric field (2.47 eV) further suppresses electron–hole recombination. The band edges straddle the water redox potentials across the entire pH range of 1–14, fulfilling the thermodynamic criteria for universal overall water splitting. The system shows strong visible-light absorption with a peak absorption coefficient of 1.04 × 10 5 cm −1 at 3.03 eV and ultrahigh hole mobility (69276.91 cm 2 V −1 s −1 along the armchair direction), with mobility asymmetry between carriers reducing recombination. Under biaxial strain (–6% to +6%), the redox alignment is preserved, and tensile strains (+4% to +6%) notably enhance light absorption. These results establish GeC/B 2 SSe as a highly promising photocatalyst for solar hydrogen generation, offering a solid theoretical basis for future experimental development.

To compete with fossil fuels, biofuels produced from renewable waste biomass must be cost-effective, adaptable to existing heat and power infrastructure, and possess desirable fuel properties and performance metrics matching those of fossil fuels, while having a much lower carbon footprint. However, handling and processing biowastes in thermochemical biorefineries is challenging owing to their high moisture content, low bulk density, poor grindability, low calorific value, and heterogeneous physicochemical properties. Torrefaction has emerged as an effective thermochemical technology for upgrading biowastes into torrefied biomass, which exhibits improved, homogeneous physicochemical properties, including higher calorific value, higher bulk density, better grindability, and hydrophobicity. This review synthesizes the current state of research on torrefaction, with particular emphasis on process parameters, reactor designs, commercial-scale implementations, and an analysis of its strengths, weaknesses, opportunities, and threats. The comparative advantages and limitations of different torrefaction reactors are highlighted, emphasizing how each reactor’s characteristics determine its suitability for specific circumstances and operating conditions. This article also considers the technical and economic challenges associated with scaling up torrefaction. The discussion on specific case studies on techno-economic analysis of torrefaction outlines the key barriers and provides incentives for researchers to consider when upscaling the technology. The strengths, weaknesses, opportunities, and threat analysis offers strategic insights for policymakers and industry stakeholders into possible actions to support torrefaction and its upscaling.

Exploring advanced materials for efficient activation and conversion of CO2 is a crucial approach to mitigate climate change and reduce reliance on fossil fuels. Extensive joint gas-phase mass spectroscopy and kinetic studies performed herein indicate that a mass-selected B6+ monocation can consecutively activate and convert up to seven CO2 to CO under ambient conditions, setting up a record number of CO2 molecules that an isolated cluster can activate in experiments. Detailed theoretical calculations and analyses reveal the ground-state, intermediate, and transition-state geometries as well as CO2-activation and CO-desorption pathways of the concerned species. The catalyst-free CO2-reduction reactions B6+ + nCO2 → B6On+ + nCO (n = 1-7) all appear to be barrier-free in kinetics and thermodynamically favorable at room temperatures, with the calculated exothermicities increasing almost linearly with the number (n) of CO2 molecules activated in the processes. Two electron-deficient periphery B atoms in B6On+ (n = 0-6) are found to serve as active sites to form one effective σ-donation and two weak π-back-donations each in two consecutive steps, with the first site activating a π-bond in O=C=O to form the O≡C-O-adsorption states, while the second site releasing a CO molecule from the CO-desorption states to form the final products, B6On+, unveiling the important role of boron as a honorary transition metal in CO2 activation and conversion.

Microalgae have the potential to produce hydrogen through photosynthesis, making them a promising alternative to traditional fossil fuels. Although the progress in large-scale production is limited by biological constraints, such as low hydrogen production rates and sensitivity to environmental conditions, the bioengineering of microalgae is an important tool that will help overcome these limitations by enhancing hydrogen production efficiency and improving tolerance to varying environmental conditions. The review indicates the effectiveness of the inhibition of photosystem II (PSII), the introduction of oxygen-tolerant hydrogenase variants, and enhanced electron flow to hydrogenase enzymes as effective strategies to improve hydrogen production in microalgae. The role of integrated systems that combine hydrogen production with co-product generation, such as biofuels, bioplastics, or high-value metabolites, will enhance economic feasibility and sustainability. Also, advancements in bioreactor designs, coupled with real-time monitoring and control systems, create optimized environments that favor large-scale production. This integrated bioengineering approach not only maximizes biohydrogen potential, but also aligns with circular bioeconomy principles by minimizing waste and utilizing resources efficiently. Exploring new ways to enhance the integration of the use of microalgae for biohydrogen production and other valuable products will drive a more efficient and environmentally friendly bioprocess.

Abstract The transition from fossil fuels to renewable energy is urgent, yet political polarization around climate change continues to impede progress. Strategic communication may help counter ideological resistance and foster bipartisan support for green energy initiatives. Guided by the Elaboration Likelihood Model and Moral Foundations Theory, this study examines how morally framed messages may enhance elaboration through increasing personal relevance. It also explores how this relationship varies by political ideology and how elaboration influences attitudes toward offshore wind and geothermal energy. Across two experiments, we found some evidence that the use of moral framing may increase elaboration, though the results did not reveal that these effects varied by ideology. We also found that increased elaboration with a persuasive message may lead to stronger attitudes toward green energy.

The intend of this paper is to see the impact of artificial intelligence on climate change. As AI is increasingly being adopted across various sectors like energy systems, manufacturing, healthcare, and urban infrastructure, it is improving efficiency, reducing wastage and supporting better management through forecasting. Adoption of AI can reduce the energy per unit of output which further reduces greenhouse gas emissions, but at the same time, it can significantly increase the consumption of water and electricity through data centres and computational infrastructure. If this transformative technology is powered by fossil fuels, it can be detrimental for the environment since it increases emissions. Additionally, if there are efficiency gains, the cost of production decreases which further stimulates increase in production and consumption, offsetting environmental benefits. There are three main objectives of the paper- The first objective is to provide a conceptual framework explaining the dual effect of AI in climate outcomes; the second objective is to analyse the trends in AI venture capital investment across the United States, China and India and across key sectors; the third objective is to draw policy lessons for India based on the performances and experiences of China and the United States. Data on AI venture capital investment is from 2012 to 2024, which shows rapid growth in AI funding, especially in manufacturing and transport sector. Trend of emissions from various sectors suggest that more efficiency coexists with more economic activity. By comparing the United States and China, importance of good government policy is observed for positive environmental outcomes. In the United States advanced technologies like AI are mostly market driven, whereas in China the government takes a lead in planning and execution. Both these methods can improve the efficiency and lead to economic growth. However, the emissions depend on the scale of production and use of energy. Developing countries like India should take key lessons on AI policies which align with climate goals. Without strong government policies and clean energy expansion, growth driven by AI can further increase energy demand instead of reducing emissions.

ABSTRACT The climate crisis and global commitments to achieve net-zero emissions by 2050 have intensified the focus on renewable energy. However, Australia’s renewable energy sector faces significant challenges, particularly reliance on imported materials and technologies. This study evaluates trends and policy developments, identifies challenges to Australia’s renewable energy transition and proposes strategic recommendations to enhance economic viability and environmental sustainability. A review of 45 selected studies based on the energy transition theory, sustainable supply chain management and global-local interdependencies, reveals key barriers such as reliance on fossil fuels, grid integration issues and regional disparities. These findings highlight the need for technological innovation, policy reforms and strategic investments to strengthen grid resilience and build sustainable supply chains. Australia has strong potential to lead the global renewable energy transition by expanding domestic manufacturing capacity, upgrading infrastructure and fostering coordinated action between government and industry. A comprehensive conceptual framework is presented to guide sustainable sector development. This study also identifies priorities for future research, including advanced grid technologies, local production systems, recycling practices and region-specific energy strategies to support a resilient and competitive renewable energy ecosystem.

In the Latin American Pacific region, rivers are the primary transportation routes for isolated and non-interconnected areas; however, river transport relies heavily on fossil fuels, resulting in high operating costs, CO2 emissions, and energy dependence. To address this challenge, this study proposes a methodology for the optimal sizing of renewable-based charging stations specifically adapted to the environmental and operational conditions of the Colombian Pacific coast. This research fills a critical gap in the literature by moving beyond urban-centric charging models and simplified theoretical assumptions, instead integrating real river navigation data with technical modeling of electric boat energy consumption. The methodology evaluates the technical, economic, and operational performance of photovoltaic and hybrid photovoltaic–hydrokinetic microgrids designed to ensure reliability under the region’s extreme resource seasonality and bimodal pluvial regime. Results indicate that while purely photovoltaic systems offer lower initial investment costs, hybrid configurations significantly enhance energy resilience by leveraging complementary renewable sources during periods of low solar irradiation. Crucially, the transition to electric propulsion reduces annual CO2 emissions by more than 98%, mitigating approximately 3421 kg per vessel compared to conventional 20 HP gasoline engines. A comparative analysis shows that the 1.1 kW electric boat is a cost-effective solution, with a 1.76-year return on investment. In contrast, the 4 kW model offers operational performance comparable to conventional gasoline boats, with a 4.95-year payback. This study provides a foundational framework for sustainable mobility in high-vulnerability territories by adapting technological solutions to site-specific environmental realities.

The global ambition to achieve net-zero emissions by 2050 is driving intense research into low-carbon energy vectors to mitigate the climate impact of the dominant use of fossil fuels. This challenge creates significant demand for sustainable energy sources to support the transition. While hydrogen is a key component of the green energy economy, ammonia has emerged as a highly promising alternative. Its distinctive qualities as a carbon-free fuel and an efficient hydrogen carrier offer a viable pathway to reduce emissions. Ammonia can both complement existing energy infrastructure (such as natural gas or grey/blue hydrogen) to accelerate near-term decarbonization and ultimately serve as a mainstream renewable energy vector in a fully net-zero economy. This review details the potential of ammonia as a renewable energy carrier, its storage, production, and distribution. It encompasses technologies such as the traditional Haber-Bosch process and new ammonia production methods, including electrochemical synthesis, and focuses on their efficiency, scalability, and environmental impact. The recent advances, principles, and challenges of direct ammonia fuel cells are discussed, with a focus on different cell mechanisms, electrolyte materials, and catalysts. The review also discusses applications of ammonia-based solid electrolyte fuel cells across sectors, highlighting their flexibility and economic potential as critical decarbonization technologies.

Methane is considered one of the cleanest energy sources as it produces fewer pollutants upon burning compared to other fossil fuels. Its accidental release during extraction, transportation, and use, however, poses significant environmental and safety risks, warranting advanced sensing technologies to monitor its concentration in ambient air. Here, we prepare nanoparticle-based materials for sensing methane at concentrations that are highly relevant in the atmospheric environment. The nanoparticle (NP) building blocks of the sensing materials are produced by spark-ablating and simultaneously quenching Sn electrodes with a N2 flow at atmospheric pressure. The resulting Sn NPs are subsequently collected and oxidized to SnO2 by thermal annealing in ambient air before doctor blading them onto substrates with interdigitated electrodes. The synthesized materials were characterized by X-ray diffraction and photoelectron spectroscopy, Brunauer-Emmett-Teller analysis, as well as atomic force, transmission, and scanning electron microscopy. The results show that our sensing materials can quantify methane concentrations down to 0.2 ppm, having a signal-to-noise ratio of 58 and a theoretical limit of detection of ca. 7 ppb. What is more, they maintain excellent robustness across a relative humidity range of 20-80% and exhibit a high cycling stability and repeatability; features that render them superior compared to other metal oxide semiconducting materials reported in the literature so far. Based on our measurements, we also offer new insight into how the NP synthesis process can affect sensor sensitivity, demonstrating a correlation between spark-ablation energy and NP size, which in turn determines the crystal size, the specific surface area, as well as the fraction of adsorbed oxygen on the surface of the sensing material, and consequently its interaction with the target gas. Combined with the simplicity of their preparation, these sensing materials hold great potential for a wide range of environmental and industrial applications.

Abstract Transitioning away from fossil fuels is in the best interest for long-term stakeholders of oil firms to mitigate risk from climate policy. Yet firms have an informational and positional advantage over strategies to mitigate climate-related risks, such that there is little incentive to decarbonize. Building on theories of firm behavior and the three faces of political power, we argue that investor pressure will be unlikely to change the climate strategy of fossil fuel firms. To measure climate strategy, we develop a novel technique using natural language processing tools to parse annual filings of all publicly-listed oil firms in the US. Using a difference-in-differences design exploiting an exogenous shock to shareholder power from a Securities and Exchange Commission regulatory amendment, we find no effects of shareholder pressure on deep reforms to climate strategies and weak effects on incremental pro-climate behavior. Through a case study of ExxonMobil, we show that climate-motivated investors are unable to overcome internal stakeholder resistance, despite shareholder pressure through direct communication, filed resolutions, and media campaigns. Our findings illustrate that polluting firms remain resistant to financial pressure for decarbonization, suggesting an important role for policy.

In 2025, escalating consumption of fossil fuels has driven the atmospheric CO2 concentration to 430 ppm, which is the highest value in human history. Photoelectrocatalytic CO2 reduction offers a viable strategy to mitigate CO2 levels, while addressing the surging demand for fossil energy. Herein, an in situ synthesis strategy of a solvothermal method combining with successive ionic layer adsorption and reaction (SILAR) was developed to fabricate a 3D honeycomb-structured In2S3/CdS heterojunction on carbon paper mimicking plant cells for PEC CO2 reduction. The carbon paper substrate exhibits an excellent photothermal effect, with its surface temperature reaching 65 °C. Photochemical and photoelectrochemical analyses indicate that the formation of the heterojunction can effectively enhance the utilization of photogenerated carriers. Thus, the optimal In2S3/CdS-4h catalyst reduces CO2 to HCOOH, CH3COOH, and CH3CH2OH products under mild reaction conditions, with a carbon-based product formation rate of 28.75 μM h-1 cm-2 and an electron selectivity for C2 products of 88.8%. Repeated experiments reveal a favorable reproducibility of In2S3/CdS-4h photoelectrodes with the RSD lower than 10%. Moreover, the In2S3/CdS-4h heterojunction exhibits improved stability, retaining 70.5% of its initial activity after five cycles (10 h), whereas CdS retains only 53.8%. Considering the underlying mechanism, optical simulations and chemical field simulations confirm the benefits of this honeycomb structure on light absorption and C2 product selectivity, respectively. Operando IR spectra identified the key *OCHO and *OC-COH intermediates responsible for the formation of the C1 and C2 products, respectively. Finally, DFT calculations show that the In2S3/CdS interface specifically promotes C-C coupling (forming *OC-COH) compared with the individual components. This work presents a perspective for the rational design of catalysts via multieffect synergy, advancing efficient PEC CO2 reduction to C2 products.

With the aim of reducing greenhouse gas emissions from energy consumption and advancing the green energy transition, this study employs sodium hydroxide and water glass as activators to facilitate the replacement of fossil fuels with renewable energy sources, with physically activated recycled micro-powder serving as an auxiliary cementitious material to prepare alkali-activated recycled hollow concrete. This study pioneers the application of the coarse aggregate tight-packing theory (bulk density method) to the preparation of alkali-activated recycled hollow concrete containing sand. By integrating Matlab image binarization techniques, we quantitatively analyzed the causes of porosity deviation, achieving precise alignment between target and actual porosity. This work fills a theoretical gap in the quantitative design of porosity for this concrete type. Additionally, the effects of different binder material dosages and pore volumes on the mechanical properties and permeability coefficients of sand-containing porous concrete were evaluated. Experimental results indicate that the calculated pore volume of sand-containing porous concrete prepared using the dense-packing theory (bulk density method) exhibits a smaller average error compared to the actual pore volume. As the amount of cementitious materials increases, the compression strength of permeable concrete gradually increases. When the cementitious material content is 450 kg/m3, and the target porosity is 15%, the concrete’s 28-day compressive strength reaches 21.4 MPa. At a porosity of 15%, the permeability coefficient ranges from 5.2 to 5.7 mm/s.

Cities worldwide face immense challenges in transitioning to a sustainable future. While being structurally and politically bound to continuous growth, the striving for a constant increase in production and consumption puts enormous pressure on our planet and its ecosystems. Degrowth has been proposed as a pathway to solving this dilemma. Although scholarly attention to urban degrowth has expanded, a central aspect of cities remains partly unexplored: mobility. Urban mobility, being motorized and dependent on fossil fuels, has a substantial environmental and social impact, making it a central issue for sustainability. Within mobility research, urban sustainability has primarily been addressed by problematizing automobility and discussing how to replace the car as the dominant mode of transport. However, the relationship between mobility and growth extends beyond cars and needs to be addressed more generally. This article develops and expands the conversation between the degrowth and sustainable mobility literatures through a theoretical exploration of the concept of “limits.” It proposes a relational conceptualization of limits, providing an analysis of this concept in relation to key vectors of urban mobility: space, speed, and the body. Our study suggests not only that limits should be conceptualized along these vectors but also that these specific limits could be used to tease out what sustainable urban mobility might mean in practice.

As environmental pollution and the depletion of fossil fuels become more serious problems, biodiesel has become a viable renewable alternative. This study employs a systematic physicochemical analysis to examine the potential of Cola rostrata seed oil as a novel biodiesel feedstock. The result shows that the produced biodiesel exhibited a yellow coloration typical of conventional biodiesels, with a density of 0.885 kg/m³ and kinematic viscosity of 3.20 mm2/s, conforming to ASTM D6751 (1.9-6.0 mm2/s) and EN 14214 (3.5-5.0 mm2/s) specifications. The transesterification process significantly reduced viscosity from 17.30 mm2/s to 3.20 mm2/s. While the flash point (76°C) fell below biodiesel standards (ASTM: 130°C min; EN: 120°C min), it remained comparable to petrodiesel (74°C). The fuel demonstrated superior cetane number (54.33) exceeding both ASTM (47 min) and EN (51 min) requirements, suggesting excellent ignition quality. However, cold flow properties (cloud point: 5°C, pour point: -3°C) indicated limitations in low-temperature performance. Energy content analysis revealed a heating value of 34.73 MJ/kg, lower than petrodiesel but within functional range. Comparative analysis showed favorable properties relative to other biodiesels: higher cetane number than soybean (49) and sunflower (55) biodiesels, lower viscosity than palm (4.5 mm2/s), and intermediate density between palm (878 kg/m3) and castor (917.16 kg/m3) biodiesels. The study provides critical baseline data for further development of this underutilized feedstock, contributing to the diversification of sustainable biodiesel sources.