Search Results (809)

Maritime transport entered the EU Emissions Trading System (EU ETS) in 2024, turning a route’s carbon performance into an economic variable. Existing studies examine this on established routes; the case for a new (greenfield) short-sea corridor under the post-2024 regime remains unaddressed, particularly in the under-served south-eastern Baltic. This study proposes a transparent, transferable methodology linking multi-criteria route selection, a lane-metre demand model, a speed-dependent fuel-consumption model and a consignment-level modal-shift carbon balance, applied to a prospective Gdynia–Liepāja Ro-Pax connection (148 nautical miles). At high deck utilization, each freight unit shifted from the 850 km road alternative avoids roughly 300–380 kg of CO₂ (a 44–55% reduction), because a short-sea leg replaces a long road haul rather than because the ferry is cleaner per tonne-kilometre. The benefit is conditional: the corridor is climate-beneficial only above a break-even freight-deck occupancy of about 45% at design speed, falling to about 34% under slow steaming. Across the demand scenarios (about 17,900–35,900 units per year), it avoids on the order of 10,000–13,400 t of CO₂ annually under high demand, while under low demand the annual balance ranges from a small net increase at design speed to a modest saving under slow steaming. The corridor relieves the congested Suwałki Gap and aligns with smart-port enablers, providing a replicable decision tool for operators and port authorities. Full article

Background: AML cells can be defined by impairments in glycolytic metabolism, resulting in increased glucose uptake coupled with reduced glycolytic flux. Consequently, cells rely on alternative pathways such as glutamine metabolism to fuel mitochondrial respiration through anapleurosis. AML cells express upregulated levels of glutamine transporters and catabolic enzymes such as solute carrier family 1 member 5 (SLC1A5) and glutaminase 1 (GLS-1), respectively, to support metabolic needs; impairment of glutamine metabolism induces proliferative arrest. Our previous work identified plumbagin (PLB) as a selective activator of pyruvate kinase isoform M2 (PKM2), resulting in increased PKM2 tetrameric protein, impaired PKM2 nuclear translocation and suppressed c-Myc expression. Objective: Therefore, we aimed to investigate whether PLB-mediated PKM2 activation influences glutamine metabolism as a downstream effect of c-Myc suppression in AML. Methods/Results: AML cell lines treated with PLB were cultured in the presence or absence of glutamine and were compared to cell models with genetically suppressed PKM2 to assess for differences in growth. Spectrophotometric analysis revealed that PLB treatment reduces intracellular glutamine uptake, and immunoblotting indicated suppression of GLS-1 expression, ultimately leading to reduced AML cell proliferation and viability. Supplementation with glutamine partially restored cell growth, indicating that PKM2 modulation is associated with impaired glutamine uptake and utilization. Conclusion: Overall, this study explores the downstream implications of PLB-induced alterations in the c-Myc/PKM2 axis, expanding the understanding of PKM2’s function beyond glycolysis. The findings presented confirm that PKM2 activation leads to indirect consequences on glutamine metabolism in AML, providing further insight into the mechanisms of PLB-mediated AML cell death. Full article

Assessing climate performance through emission-centric metrics provides an incomplete picture of countries’ progress toward integrated climate objectives. This study proposes the Climate Integrated Performance Index (CIPI), a multidimensional and explainable composite indicator for 27 European countries during 2015–2023. CIPI integrates six thematic dimensions: emissions, energy systems, mitigation capacity, transport, agriculture, and waste–land-use interactions, using robust normalization, a policy-informed weighting framework, and formal statistical validation. Based on 243 country–year observations, the results indicate that CIPI is non-redundant. Pearson correlations reveal strong positive associations with the Energy Index (r = 0.899) and Mitigation Index (r = 0.894), alongside a significant negative association with the Agriculture Index (r = −0.659), highlighting sectoral trade-offs. Variance decomposition further shows that energy and mitigation dimensions jointly account for approximately 87% of explained variance, whereas agriculture exerts a systematic counterbalancing influence. To support structural interpretation, an explainable machine learning framework combining XGBoost and SHAP was implemented as a diagnostic layer. Renewable-energy capacity emerged as the dominant structural driver of integrated climate performance, and SHAP-based analyses revealed a nonlinear threshold effect, with positive contributions accelerating beyond a normalized renewable-capacity level of approximately 0.58 (95% bootstrap confidence interval: 0.54–0.62), particularly under low fossil-fuel dependency conditions. Because the machine learning models use indicators that also contribute to index construction, the results are interpreted as evidence of structural consistency and diagnostic interpretability rather than independent predictive discovery. To address this limitation, repeated cross-validation, subsample validation, benchmark comparisons, and weighting-sensitivity analyses were conducted. Ranking robustness remained high under alternative weighting schemes (Spearman ρ > 0.96), while comparison with an emission-centric benchmark demonstrated substantial rank reversals, indicating that broader sectoral and policy dimensions influence climate-performance assessment. Overall, CIPI functions not only as a benchmarking tool but also as a transparent diagnostic framework for identifying structural trade-offs, nonlinear relationships, and policy-relevant climate-transition dynamics. Full article

The maritime sector is increasingly focused on green propulsion technologies to address stringent regulations on greenhouse gas emissions and other pollutants. In recent years, research has proposed novel electric and hybrid propulsion architectures and advanced energy management systems. This paper reviews the fundamentals and the most recent developments of hybrid and electric propulsion technologies, evaluating their environmental and economic implications. Particular attention is given to the various onboard energy storage, conversion, and generation technologies, outlining their potential and limitations. Through the analysis of numerous research studies in alternative marine propulsion, the suitability of Li-ion batteries, supercapacitors, flywheels, and different types of fuel cells for maritime transport needs is evaluated, along with the possibilities offered by renewable energy to reduce the environmental impact of marine energy systems. Additionally, it discusses important future directions, research gaps, and emerging paradigms in sustaining maritime eco-systems. Unlike previous reviews that mainly focus on individual technologies, this study provides an integrated analysis connecting propulsion architectures, energy storage systems, fuel cells, alternative fuels, renewable energy integration, and energy management strategies. The review also discusses technology limitations, operational suitability for different vessel categories, and future research challenges toward maritime decarbonization. In presenting these issues, the author’s intention is to promote interdisciplinary cooperation between shipbuilders, policymakers, and researchers for the benefit of more sustainable development of the maritime industry. Full article

Low-emission zones, known in Poland as clean transport zones, grant or deny access according to a vehicle’s Euro standard, age and fuel. These administrative labels, however, are only loosely connected to what an internal combustion engine (ICE) actually emits on the road. The founding assumption of a Euro-based zone is that the Euro stage is a usable proxy for the mass a vehicle emits, so admitting newer classes lowers the fleet emission inventory, the activity-weighted sum of class emission factors defined as the product of fleet frequency, in-zone activity and emission factor. This paper tests that assumption directly. A paradox follows: a newer, compliant, large and heavy vehicle can release more carbon dioxide (CO₂), nitrogen oxides (NOx) and particulate matter (PM) than an older, smaller vehicle that the same rule turns away. We develop a reproducible emission-accounting framework that pairs real-world emission factors, resolved by Euro standard, fuel, engine displacement and mass, with a mass-dependent treatment of non-exhaust particles. Given the number of petrol, diesel, liquefied-petroleum-gas (LPG) and electric vehicles in a fleet and the areas of the city and the zone, the model returns daily emissions and their density per square kilometre before and after a rule is applied. For a fleet parameterised on Polish statistics, the Warsaw and Kraków criterion removes about 80% of zone NOx, because the oldest vehicles are also the high-NOx diesels; the same rule, however, removes only about 40% of CO₂ and 48% of PM, and it shifts the admitted fleet toward heavier vehicles that produce more non-exhaust PM. Emission-based, fuel-based and hybrid criteria deliver larger and fairer reductions at the same level of stringency. Aligning zone access with real combustion emissions is therefore both more effective and more equitable, and it supports the wider goals of sustainable, low-carbon urban mobility. Full article

Biomass-derived fast pyrolysis oil (PO) represents a promising alternative fuel for aviation and heavy transport. However, its high content of oxygenated organic molecules necessitates catalytic hydrodeoxygenation (HDO) before it is viable to be sent to a refinery. Single-step upgrading processes have encountered significant challenges, particularly reactor plugging and catalyst deactivation. To address these issues, an initial stabilization step at lower temperatures has been proposed to stabilize the most reactive compounds in the oil prior to hydrodeoxygenation. In this study, a range of different carbon- and Al₂O₃-supported catalysts (Ni/Al₂O₃, sulfided NiMo/Al₂O₃, Ru/C, Pd/C, Pd/Al₂O₃, Pt/C, and Pt/Al₂O₃) were evaluated for furfural stabilization in a batch reactor for 1 h with an initial pressure of 90 bar H₂ and 180 °C with and without sulfur present. Sulfur tolerance was assessed by repeating all experiments with the addition of 1170 wt-ppm sulfur to the feedstock. The most active catalysts—Ni/Al₂O₃, Ru/C, Pd/C, and Pd/Al₂O₃—also exhibited the highest susceptibility to sulfur poisoning. Although Pt/C did not demonstrate the highest overall activity, sulfur addition appeared to enhance its performance, both in terms of furfural conversion and liquid yield of desired products. Full article

The electrification of road transportation has been widely proposed as a viable strategy for minimizing fossil fuel dependency and the environmental impacts of traditionally powered motor vehicles. This strategy has led to the increased adoption of electric vehicles (EVs), such as electric cars, electric buses (e-buses), electric trucks (e-trucks), etc., in cities, as they are more sustainable. Initiatives directed towards the electrification of vehicles can contribute towards sustainable transportation. One of these initiatives is the development of electric road systems (ERSs), which enable roadways to supply electric power to electric vehicles when the vehicles are in motion. The deployment of ERSs has developed as an alternative to address issues that negatively impact the adoption of EVs, such as long charging times, higher costs, short driving ranges, etc. Accordingly, this article explores the literature to understand how to ensure the reliable and safe operation of future electric road technologies and system deployments in municipalities. This study examines how ERSs power e-buses without relying solely on batteries. Additionally, this article analyzes the technological, legal, political, economic, and social factors that impact the electrification of road transport. Grounded in the literature, this study suggests that ERSs offer a cost-effective option to electrify heavy-duty transport, such as e-buses and e-trucks. The study provides insights for road authorities, municipalities, and policymakers to improve ERS deployment strategies, ensuring sustainable transportation while decarbonizing road transport. Full article

Hydrotreated vegetable oil (HVO) is considered a promising drop-in alternative to conventional diesel fuel for reducing greenhouse gas emissions in road freight transport. However, empirical evidence on its performance under real-world operating conditions remains limited. This is particularly true for complex logistics systems such as agricultural transport. This study assesses the effect of neat HVO (HVO100) on fuel consumption using high-resolution vehicle operational data collected from three heavy-duty trucks during a full-scale sugar beet logistics campaign in Germany. Vehicle operation was recorded via a manufacturer-independent fleet management system interface and combined with satellite-based positioning data for route reconstruction. After data preprocessing and quality filtering, a total of 3353 valid transport tours were analyzed. Fuel consumption values during HVO100 operation were corrected for density-related measurement bias. The effect of fuel type was evaluated using a linear mixed-effects model. The model accounted for load status, route topography, driving speed, and their interactions. In addition, stratified pairwise comparisons were conducted across operational conditions. The results show that, in the full three-vehicle model, HVO100 was associated with a statistically significant increase in fuel consumption of 0.51 L/100 km under baseline conditions with an empty vehicle, low topographic variability, and medium driving speed, corresponding to approximately 2.3%. In a sensitivity analysis excluding the diesel-only truck, the estimated difference decreased to 0.34 L/100 km and was no longer statistically significant. Load status and topography were identified as the dominant drivers of fuel consumption with substantially larger effects than fuel choice. Overall, the findings indicate that the effect of HVO100 on fuel consumption is small relative to operational variability. Under many real-world operating conditions, operational factors outweighed the differences attributable to fuel type. These findings indicate that switching to HVO100 did not result in a substantial volumetric fuel-consumption penalty in the investigated agricultural logistics system. Full article

Proton-exchange membranes are crucial for water electrolyzers and fuel cells, but their performance declines under low humidity due to dehydration. Existing reviews mainly list experimental results without analyzing the mechanisms of proton conductivity stabilization. This review systematically summarizes approaches to enhance moisture-independent proton conductivity and evaluates their prospects. Key factors governing conductivity include microstructure, sulfonic group concentration, and hydration level. Stability under dry conditions depends on water retention and thermal resistance. Main strategies involve hybrid composite membranes, ionomer structure control via pre-treatments, and novel proton-conducting polymers. Promising directions include oriented channel structures, MOFs, and graphene-based materials. The stabilization mechanism relies on retaining water through hydrophilic additives that form stable hydrates, enabling proton transport even under harsh conditions (up to 120 °C and 50% RH, per US DOE targets). Among Nafion alternatives, sulfonated aromatic polymers and phosphoric-acid-doped polybenzimidazole demonstrate good performance at elevated temperatures (100–200 °C), though durability remains a challenge for the latter. Despite ongoing research, Nafion-based composites still offer one of the best overall balances of conductivity, stability, and processability. A significant research gap persists: long-term membrane performance is poorly studied, and many additives degrade over time or block proton transport sites due to ion exchange with metal cations. Full article

Achieving the Sustainable Development Goals (SDGs) requires countries to simultaneously advance renewable energy transitions, environmental innovation, carbon efficiency, and sustainable governance mechanisms. Although previous research has extensively examined sustainability transitions and environmental sustainability, comparative assessments integrating renewable energy, environmental innovation, carbon efficiency, fiscal instruments, and fossil fuel dependency remain limited. Using 2023 data from 31 OECD countries, the study analyzes eight sustainability-related indicators through an integrated CRITIC-ARAS multi-criteria decision-making framework. The CRITIC method is employed to determine objective criterion weights, while the ARAS method evaluates countries’ performance relative to an ideal sustainability profile. The findings reveal considerable differences in sustainability performance across OECD countries. CO₂ emissions from air transport per capita emerge as the most influential criterion within the weighting structure. According to the results, Slovenia, Iceland, and Norway demonstrate the strongest transition performance. Countries with higher renewable electricity generation, stronger environmental innovation support, lower transport-related emissions, and lower fossil fuel dependency generally achieve better outcomes. Sensitivity analysis supports the overall stability of the ranking structure under alternative weighting scenarios, although the exclusion of the highest-weighted criterion produces noticeable ranking shifts for some countries. The results indicate that sustainability performance depends not only on environmental outcomes but also on countries’ ability to coordinate renewable energy policies, environmental innovation, fiscal instruments, and decarbonization strategies. From a policy perspective, the findings emphasize the importance of renewable energy expansion, environmental taxation, transport decarbonization, environmental R&D support, and fossil fuel subsidy reform for strengthening long-term sustainable development strategies. This study contributes to the sustainability assessment literature by providing a comparative and policy-oriented framework for benchmarking sustainability-oriented green transition performance across countries through integrated environmental, energy-related, and innovation-based indicators. Full article

The National Electric Vehicle Infrastructure (NEVI) Program is a major federal initiative to expand electric vehicle (EV) charging infrastructure and support transportation electrification in the United States. This study examines the evolution of NEVI implementation across New York, New Jersey, and Pennsylvania between 2022 and 2026. A qualitative comparative longitudinal approach was used to analyze 23 official documents, including NEVI deployment plans, annual implementation updates, Federal Highway Administration guidance, and Joint Office of Energy and Transportation resources. The findings show that implementation evolved beyond compliance with the Alternative Fuel Corridor toward broader transportation electrification, characterized by adaptive governance, infrastructure scalability, and operational resilience. New York demonstrated the most advanced implementation through extensive interagency coordination, infrastructure integration, and long-term planning. New Jersey emphasized metropolitan charging accessibility, adaptive planning, and alignment with statewide zero-emission vehicle objectives. Pennsylvania followed a more gradual implementation trajectory shaped by phased deployment, regional accessibility priorities, and procurement-related challenges. The study demonstrates that implementation trajectories differed despite a common federal framework and contributes to the literature by providing a comparative longitudinal perspective on how governance and institutional adaptation influence large-scale EV infrastructure deployment. Full article

Direct methanol fuel cells (DMFCs) have attracted considerable attention recently for various applications ranging from portable ones to transportation. The efficiency of DMFCs depends on the kinetics of anodic and cathodic electrocatalysts. Due to sluggish anodic methanol oxidation reaction (MOR), DMFCs require an effective and bifunctional catalyst for promoting efficient MOR. The state-of-the-art MOR catalysts, such as Pt/C and Pt-Ru/C, have been shown to exhibit reasonable MOR activity; however, the insufficient mass activity and poor stability of carbon-supported catalysts have been a major limitation, requiring an alternative, efficient, electrocatalyst that exhibits high mass and specific activities. In addition, electrocatalysts without any carbon support (self-supported electrocatalysts) further mitigate their poor stability and therefore enhance their durability. In this regard, metal aerogel catalysts, which are entirely composed of metallic networks, recently attained special interest due to their specific advantages over conventional carbon supports, such as high catalyst utilization and improved electronic conductivity and stability. In this review, we systematically reviewed various metal aerogel catalysts developed for MOR since their first discovery in 2009. The metal aerogel demonstrated superior MOR performance relative to carbon-supported commercial catalysts, with enhancements ranging from 2-fold to 22-fold of mass activity. We also statistically compared the mass activity of metal aerogels with traditional carbon-supported, non-carbon-supported, and advanced shape-controlled catalysts and found that metal aerogels exhibited high mass activities compared to other catalyst systems. Therefore, we clearly establish that metal aerogel catalysts possess great potential as efficient MOR catalysts in DMFCs. In addition, we have provided several future research directions and strategies for further development of metal aerogel-integrated DMFC devices. Full article

Photobiological hydrogen (H₂) production by microalgae and cyanobacteria is widely seen as a promising and sustainable alternative to H₂ produced from fossil fuels. However, its efficiency remains limited because the enzymes responsible for H₂ production are highly sensitive to oxygen (O₂), while photosynthesis itself generates O₂ that can suppress their activity. This mini-review explores how different photosynthesis inhibitors affect H₂ production in these microorganisms, with a focus on their molecular targets and their physiological effects. In both microalgae and cyanobacteria, compounds such as DCMU, atrazine, DBMIB, CCCP, and KCN influence H₂ metabolism by altering electron transport, O₂ release, proton gradients, and cellular redox balance. The reviewed studies indicate that complete inhibition of photosynthetic electron flow is usually unfavorable for sustained H₂ production because it reduces the electron supply required by H₂-evolving enzymes. Therefore, anaerobiosis is more reliably established by physiological or cultivation-based strategies, whereas photosynthetic and respiratory inhibitors are best used as mechanistic probes or as auxiliary modulators under carefully optimized conditions. Their effects are strongly context-dependent, reflecting the balance between O₂ suppression, residual electron transport, respiratory O₂ consumption, and competing electron sinks. Full article

The energy transition in maritime shipping is increasing the importance of alternative fuels and port infrastructure capable of handling them in a safe, regular, and economically justified manner. In this context, LNG remains a transitional fuel with a relatively high level of technological and organizational maturity, particularly in regions characterized by intensive liner, ferry, and RO-RO traffic. This article proposes a universal model for organizing LNG distribution within the port–transport system, based on three interdependent dimensions: demand potential, infrastructure readiness, and operational feasibility. The model structure enables the classification of ports according to their functions within the regional bunkering network and the identification of nodes of the greatest systemic importance. The model was validated using data on vessel calls, the structure of container and RO-RO traffic, LNG infrastructure status, and monthly traffic variability. The analysis demonstrated that the most justified LNG distribution arrangement in the Baltic Sea is polycentric in nature and concentrated in ports, combining a high degree of transport regularity with confirmed LNG readiness. The results indicate that the rationale for LNG infrastructure development is selective in nature and depends on the actual position of a port within the transport network, rather than solely on cargo throughput volume. The proposed model also retains its applicability to other alternative fuels after adjustment of technological, regulatory, and operational parameters. By supporting the selective development of alternative-fuel infrastructure in ports with the highest systemic relevance, the model contributes to sustainable maritime transport planning and to the transition toward lower-emission port–transport systems. Full article

The development of low-emission and reliable propulsion systems is essential for extending the operational capability of unmanned aerial vehicles (UAVs). Although aviation decarbonization is widely recognized as an important objective, it must be considered within the broader context of limited renewable-energy availability. Recent system-level analyses of transportation decarbonization have shown that the allocation of renewable electricity and sustainable fuels should prioritize sectors where direct electrification is most efficient, while hard-to-electrify sectors require alternative pathways. Aviation is one of the most difficult transport sectors to electrify because of strict energy-density requirements, especially for long-endurance airborne platforms. Therefore, sustainable liquid fuels and hybrid propulsion systems should not be considered universal replacements for electrification, but rather complementary solutions for applications where batteries alone cannot provide the required endurance, payload capacity or operational flexibility. In this context, the present study focuses on alcohol–kerosene blends for hybrid UAV power systems, where liquid-fuel energy density and partial emission reduction remain relevant engineering requirements. This work provides one of the first systematic experimental evaluations of ethanol–, butanol– and octanol–kerosene blends in a micro-turboprop engine operating as part of a hybrid UAV power-generation architecture. Unlike previous studies focused mainly on micro-turbojet thrust response, the present work evaluates the coupled influence of alcohol chain length and blending ratio on exhaust gas temperature, gaseous emissions, electrical output and operational stability under multi-load conditions representative of UAV operation. Jet-A and nine alcohol–kerosene blends containing 10%, 20% and 30% ethanol, butanol or octanol by volume were tested over four operating regimes, from idle to 2500 W electrical load. The results show that ethanol blends provided the strongest CO reduction, with E30 reducing CO by 24.9% relative to Jet-A under R3, while E10 offered the most balanced behavior across the full operating range. Higher ethanol fractions improved CO suppression but introduced NOx and low-load stability penalties. Octanol blends, particularly O20, exhibited the most kerosene-like and stable response, supporting reliable power delivery with reduced operational variability. Butanol blends showed intermediate behavior without providing a dominant advantage. A multi-criteria evaluation combining emissions, EGT behavior, relative performance, operational stability and cost identified E10 as the best overall compromise for hybrid UAV use. The study demonstrates that alcohol chain length produces nonlinear system-level effects in hybrid micro-turboprop architectures and provides an experimental basis for fuel selection in low-emission UAV power systems. Full article