The extensive availability of electricity and hydrogen in Texas provides enormous potential for adopting alternative energy for transportation. The operational phase of alternative energy infrastructure is an essential element in its environmental impact assessment and has not been evaluated up to this point, especially in terms of its utilization and vehicle mix. This study aims to evaluate the environmental impacts of alternative energy options, including fast/slow electric vehicle charging and hydrogen refueling at charging/refueling stations. The AFLEET Charging and Fueling Infrastructure (CFI) Emissions Tool was used to analyze the burden reductions in life cycle GHGs and air pollutants. The station operation considered infrastructure type, utilization, and vehicle mix (LDVs and HDVs). High utilization of the station yielded more burden reductions. Fast-charging supply equipment resulted in higher GHG burden reductions compared to the slow counterpart (367% in moderate utilization). Elevated burden reductions were observed in GHGs, VOC, and CO pollutants with more LDVs. There was an increase in NOx burden reductions of approximately 5200 lb. (moderate utilization), while transiting from 100% LDV to 75% LDV. Increased burden reductions were noted in particulate matter for 50% LDV. Also, enhanced burden reductions were observed in SOx with more HDVs for EVs and equal vehicle mix in hydrogen. Increased GHG burden reductions were identified in SMR than electrolysis. These results recommend policy makers focus on maximized utilization of the new or existing infrastructure to reduce environmental loads.

ABSTRACT The decarbonization of shipping sector necessitates the replacement of conventional fuels with sustainable alternative fuels. This paper investigates the environmental performance of three e-fuels (e-LNG, e-methanol, and e-DME) for use in a ferry operating in the Adriatic Sea. A life cycle assessment methodology is employed to assess the environmental impacts of these e-fuels across impact categories: climate change, acidification, and human toxicity. The e-fuels are compared with their fossil counterparts as well as diesel. The findings of the study indicate that e-LNG achieves 61% reduction of GHG emissions compared to LNG and 58% reduction compared to diesel. E-methanol and e-DME result in negative CO2-eq emissions in the WTT phase, while in the TTW phase e-methanol generates low CO2-eq emissions and e-DME remains at zero. E-fuels can be regarded as a promising alternative to conventional fuels, offering significant reductions in climate change impacts and contributing to lower levels of acidification and human toxicity.

A review of hybrid computational fluid dynamics and machine learning approaches for the combustion of alternative fuels

Unveiling pyrolysis mechanism of furfural: a theoretical and kinetic study.

The multimodal North Sea–Baltic corridor, consisting of 6934 km of road, is an integral part of the EU’s trans-European transport network. However, an unsatisfied level of development of alternative fuels infrastructure for road transport is considered one of the obstacles to connecting northern Member States and North-East countries. A “what-if” scenario was employed to obtain useful insights into how a given situation might be handled, and a comparison of several paths forward to make better decisions was analysed. Environmental insights for transportation sector scenarios in 2030–2035 were explored and analysed using the COPERT v5.5.1 software program. In this study, the installation of natural gas infrastructures of various station sizes and with varying capacities and types of natural gas (LNG, CNG, bio-methane) dispensed was evaluated in detail. Replacement of the existing HDV fleet (heavy-duty vehicles) with LNG-powered trucks would result in the following investment to upgrade the existing network and build new stations to meet rising LNG demand: from €21.47 to €32.3 million (the scenario of 10% market share for HDVs running on LNG), €42.94 to €64.6 (20%), and €64.4 to €96.9 (30%). The dual-fuel 10–diesel fuel 90% scenario seems to be the safest option for a large-scale investment until 2035 which may lead to moderate emission savings of 84.6 kton CO2 eq. compared to 2022 levels.

The processing of waste tires is a significant challenge. The pyrolysis of waste tires offers a sustainable pathway to produce fuels, addressing both waste management and energy recovery challenges. However, due to the presence of a large amount of unsaturated, aromatic hydrocarbons and sulfur compounds, their direct use as fuel is not possible. Catalysts based on Pd, Pt, and other metals are commonly used for the hydrotreating of pyrolysis oil for producing alternative transportation fuels. The effect of hydrotreating with the commercial Pt/Al2O3 and NiMo/Al2O3 catalysts on the chemical composition of tire pyrolysis oil was analyzed by GC-MS following a developed extraction sample preparation procedure. The pyrolysis of tires was conducted at 500 °C in a nitrogen atmosphere. The catalytic hydrotreating was performed using a 250 mL reactor at 250-350 °C and 6.5 MPa hydrogen pressure. The hexane solution of pyrolysis oil was sequentially extracted with water and dimethyl sulfoxide and then treated with oleum to separate complex pyrolysis oil into water-soluble compounds, polycyclic aromatic hydrocarbons, and saturated hydrocarbons (naphthalenes and alkanes). It was found that unsaturated hydrocarbons and water-soluble compounds were effectively removed from pyrolysis oil by hydrotreating with the NiMo/Al2O3 catalyst, which demonstrated superior performance compared to the Pt/Al2O3 catalyst that showed only partial removal. Moreover, it was demonstrated that NiMo/Al2O3 was a more efficient catalyst for the hydrotreating of pyrolysis oil to reduce the contents of toxic PAHs, sulfur, nitrogen, and oxygen in pyrolysis oil. Compared with the conventional Urals crude oil, TPOs possessed higher proportions of valuable gasoline and diesel but contained significantly more sulfur, nitrogen, and aromatic compounds as contaminants. Although hydrotreating produced a diesel fraction meeting key fuel specifications (e.g., heating value, flash point, and density), its residual PAH (0.200 wt%) and sulfur (0.0432 wt%) content still exceeded commercial diesel standards.

Dialkyl carbonates (DACs) have emerged as renewable alternative fuels, attracting considerable interest from researchers in their combustion characteristics. Compared with short-chain DACs, longer-chain DACs have a higher lower-heating value and are more reactive at low temperatures, making them more promising alternatives to diesel. Although extensive studies have been conducted on short-chain DACs, research on longer-chain DACs remains limited. This study conducted the first experimental and modeling investigation into the oxidation chemistry of the longer-chain dibutyl (DBC) and dipentyl (DPeC) carbonates using a jet-stirred reactor (JSR). The mole fractions of the reactants and oxidation products were measured at three equivalence ratios of 0.5, 1.0, and 2.0 within a temperature range of 500-1100 K. Notably, the results revealed that both DBC and DPeC exhibited a pronounced negative temperature coefficient (NTC) behavior, which was absent in short-chain DACs. A detailed kinetic mechanism was developed and validated against the experimental data. Furthermore, a comprehensive analysis of reaction pathways and sensitivity was performed based on the newly developed mechanism. The difference in the oxidation reactivity of DACs with a changed carbon chain length is also illustrated in detail. Analysis of the reaction path reveals that at low temperatures, the fuel molecules are primarily consumed through H-abstraction reactions, generating fuel radicals. A considerable amount of ketohydroperoxides (KHPs) undergo decomposition reactions to form alkyl radicals. The subsequent chain-branching pathways of both the primary fuel radicals and the alkyl radicals contribute to the pronounced low-temperature oxidation reactivity observed for DBC and DPeC. The sensitivity analysis indicates that H-abstraction reactions by OH radicals exert the most significant promoting effect at low temperatures, while the chain-terminating reactions of the key ROO species in both fuel and alkane oxidation chemistry exhibit notable inhibiting effects.

Shipping is a high-energy-intensive sector and a major source of climate-relevant and harmful air pollutant emissions. In response to growing environmental concerns, the sector has been subject to increasingly stringent regulations, promoting the uptake of alternative fuels and emission control technologies. Accurate and diverse emission factors (EFs) are critical for quantifying shipping’s contribution to current emission inventories and projecting future developments under different policy scenarios. This study advances the development of load-dependent EFs for ships by incorporating alternative fuels, biofuels and emission control technologies. The methodology combines statistical analysis of data from an extensive literature review with newly acquired on-board emission measurements, including two-stroke propulsion engines and four-stroke auxiliary units. To ensure broad applicability, the updated EFs are expressed as functions of engine load and are categorized by engine and fuel type, covering conventional marine fuels, liquified natural gas, methanol, ammonia and biofuels. The results provide improved resolution of shipping emissions and insights into the role of emission control technologies, supporting robust, up-to-date emission models and inventories. This work contributes to the development of effective strategies for sustainable maritime transport and supports both policymakers and industry stakeholders in their decarbonization efforts.

Over the past one hundred years, traditional engine have an undeniable impact on the development of human civilization.It is precisely because of the invention of traditional engines that significant breakthroughs have been achieved in many fields. Nevertheless, the use of them contribute large amount of greenhouse gas, such as carbon dioxide. The emission of these gas significantly deteriorate global environment. Additionally, due to the excessive reliance of humans on traditional engines, a large amount of fossil energy has been consumed. The fuels used in traditional engines are mostly non-renewable fossil energy. Therefore, the use of traditional engines has always been detrimental to the sustainable development of humanity in the future. In response, alternative fuel engine (hybrid engine,battery electric engine,fuel cell engine), have developed by people. As time went by and with the development of the times, their appearance gradually replaced the use of traditional engines.In this era where both traditional engines and alternative fuel engines are indispensable, this article focuses on the analysis of their working principles, performance comparisons, advantages and disadvantages comparisons, as well as emissions comparisons.

The development of computationally efficient kinetic mechanisms for alternative fuels remains a critical bottleneck for large-scale CFD simulations in engine design. This work presents a novel integrated data-driven workflow that automates kinetic mechanism development by coupling chemical lumping, skeletal reduction, and parameter optimisation within a unified framework, demonstrated through a compact OME2 combustion mechanism. Using the SciExpeM data ecosystem, the workflow automatically manages mechanism construction, reduction, and optimisation with minimal manual intervention. The approach treats aggressive skeletal reduction as the foundation for two-stage optimisation, where temporary accuracy loss is systematically recovered through targeted parameter adjustment within physically consistent uncertainty bounds. The integrated workflow achieved a decrease in the number of species from 150 to 55 using DRGEP-based reduction, followed by evolutionary parameter optimisation through OptiSMOKE++. Comprehensive validation against experimental data spanning ignition delay times, jet-stirred reactor speciation, and laminar flame speeds demonstrated reliability across operating conditions relevant to compression ignition engines (650–1700 K, 1–50 atm, ϕ = 0.3–2.0). The optimised mechanism successfully recovered the accuracy lost during reduction, particularly in the critical intermediate temperature regime (770–910 K). The integrated workflow further improved the traditional size-accuracy trade-off through systematic parameter recalibration, achieving computational efficiency for CFD applications while maintaining chemical fidelity comparable to detailed mechanisms. This methodology establishes a foundation for rapid development of compact kinetic mechanisms for alternative fuels with automated workflows ensuring physical consistency.

Abstract The environmental imperative of reducing carbon emissions by 2050 and seeking energy diversification has forced the transport and logistics sector to consider how these demanding objectives can be secured and how new environmental practices can be implemented. This paper aims to review and classify the mechanisms and the methodologies applied, mainly in the European Union, to achieve sustainable goals in freight transportation. The paper covers aspects like partnership strategies (including vertical and horizontal cooperation), intermodal freight transport actions, government policies, alternative fuels, electric and autonomous vehicles, and technological innovation measures for developing less pollutant engines. To analyze the practical implications of these mechanisms, we present two public sector novel examples in Navarre (Spain). A comparative analysis with regions such as Lombardy, South Holland, and
Aquitaine highlights transferable practices and contextual challenges, offering targeted guidance for stakeholders. The paper concludes with recommendations and open challenges for integrating sustainable practices into freight transportation systems.

Reducing CO2 emissions from global shipping remains a critical challenge in the pursuit of sustainable international trade. Though the technical and operational (T/O) measures and alternative fuel (AF) solutions have shown promise, the global maritime sector continues to face strategic and structural hurdles. This thematic narrative review revisits the fundamentals and explores the roles of T/O measures and Alternative fuel options in reducing CO2 emissions in international shipping, with a focus on the maritime energy transition. The study reveals that maximizing the benefits of T/O measures, alongside establishing a balanced energy transition matrix encompassing clean energy sources, can foster an environment conducive to future sustainability performance and substantial CO2 emission reductions. More specifically, combining operational efficiency improvements with scalable, future-focused, infrastructure-ready alternative fuels can yield significant emission reductions. The paper also introduces a conceptual model to guide the maritime energy transition, outlining a phased pathway that leverages innovation, policy, and system-level design. These insights contribute to shaping a resilient roadmap for decarbonizing international shipping by enhancing the sector’s sustainability performance.

Many environmental and energy concerns exist, including air pollution and shortages of fossil fuels, and these concerns have motivated much research. Communities are seeking alternative fuels and nations are trying to implement them appropriately. The main alternative is renewable energy, including solar, geothermal, and wind. This systematic review analyzed 39 studies (2010-2024) on renewable energy applications in sports facilities, revealing distinct adoption patterns: solar energy dominated the research (64% of studies), followed by hybrid systems (23%), geothermal (8%), and wind (5%). Our PRISMA-guided analysis shows these renewable sources can be effectively used in sports facilities, especially new ones. Key findings indicate that solar applications achieve average energy savings of 39.1% (34.6-43.6% CI) in studied facilities, while geothermal systems show higher savings at 51.3% (45.8-56.8% CI). The primary emphasis in implementation is placed on solar and hybrid applications at sports stadiums (72% of cases), but geothermal and wind power are rarely employed (15% combined), which can be explained through geographical factors and higher initial costs (average $2.8M vs $1.2M for solar installations). Since these technologies have been advancing over the last few years, their application in sports stadiums and high-energy sports arenas will likely increase. Our review found that facilities adopting renewable energy reduced operational costs by 28-47% annually. Equipping new sport facilities with renewable energies typically makes them more environmentally benign, with demonstrated CO₂ reductions averaging 1,287 tons/year per facility. An important aspect is increased energy efficiency, with hybrid systems showing 47.2% (42.1-52.3% CI) improvement over conventional systems. The integration of renewable energy systems into sports facilities leads to considerable cost savings in the long term (average payback period 6.2 years), demonstrates commitment to environmental stewardship, and aligns facilities with sustainable development principles.

Alternative fuels’ potential to decarbonize the transport sector in Serbia

This study evaluated waste cooking oil (WCO), waste engine oil (WEO), and their 50:50 blend as alternative fuels using a TOYA commercial burner, analyzing thermal efficiency, emissions profile, and combustion characteristics. Results showed that the 50:50 blend demonstrated superior performance, achieving both the fastest water boiling time (5.31 minutes) and the highest thermal efficiency (19.8%). Flame temperature profiles revealed significant differences: WCO showed the lowest (420-453°C) and most variable temperatures, while WEO burned more stably at higher temperatures. Notably, the blend achieved the most consistent peak temperatures around 500°C, directly supporting its enhanced combustion efficiency. Emission measurements showed the blend's environmental advantages, producing significantly lower carbon monoxide (8.4 ppm vs 15-16 ppm for pure oils) and particulate matter (PM 2.5 : 412.6 μg/m³ vs WCO's 469.3 μg/m³) while maintaining moderate CO₂ output. The combination of stable high-temperature combustion, reduced emissions, and minimal residue formation confirms that blending WCO and WEO creates an efficient, cleaner-burning fuel. These findings demonstrate how waste oil blending can improve both performance and environmental impact in thermal applications.

Crumb rubber is one of the main export commodities in Indonesia from the plantation sector. In the industrial scale, the process of crumb rubber drying generally still uses industrial diesel oil (IDO) as fuel. In order to participate in supporting the government's program for the development of renewable energy, especially biofuels to replace fossil fuels, many research has been conducted regarding the use of biodiesel-water emulsion (W/O) as an alternative fuel for crumb rubber drying. The biodiesel used is a mixture of 70% diesel oil and 30% FAME (B30-water) and a mixture of 60% diesel oil and 40% FAME (B40-water) from crude palm oil (CPO). The use of water as substituent agent for biodiesel is intended to increase fuel economy and minimize NOx and PM emissions which potential to decrease the rubber quality. A homogeneous and stable water biodiesel emulsion (90:10), namely B30-water and B40-water, was obtained by adding 5% emulsifier consisting of a mixture of Span 80 and Tween 80 as surfactants to form a B30-water and B40-water emulsion. Homogenization of biodiesel, water and surfactants mixture using a high-speed mixer (23,000 rpm) for 1-2 minutes resulting homogenous and stable B30-water and B40-water emulsions minimum 24 hours were then used as alternative fuel for crumb rubber drying by direct heating to the rubber surface at a drying temperature of 130-135 °C and drying air rate 1-1.5 m/sec. The results showed that B30-water and B40-water emulsions with a water content of 10% were appropriate to use as alternative fuels for crumb rubber drying. The quality of the dry crumb rubber produced was fulfill the requirement standard according to SNI 1903: 2017.

Numerical investigation on the effect of physical properties of alternative fuels on in-nozzle cavitation in a full-scale injector for a two-stroke marine engine

Gas turbines are essential for high-power energy generation, but growing demands to reduce NOₓ and CO₂ emissions make traditional combustion chamber design increasingly complex and costly. This work proposes a new modeling paradigm that combines high-fidelity Computational Fluid Dynamics using neural network learning to accelerate emission prediction. A Computational Fluid Dynamics model was developed using the Reynolds-averaged Navier-Stokes equations with the k–ε turbulence model and a non-premixed Probability Density Function approach to simulate turbulent methane combustion. NOₓ emissions were calculated post-simulation using the Zeldovich mechanism. Model validation included varying fuel flow, excess air ratio, and wall heat loss. To speed up evaluations, a multilayer perceptron neural network was trained on Computational Fluid Dynamics results to predict NOₓ and CO₂ emissions based on key inputs (fuel rate, air excess, temperature, pressure, cooling). The model achieved high accuracy with a coefficient of determination (R^2) of 0.998 for NOₓ and 0.956 for CO₂ on an independent test set. Results showed good agreement with both experimental data and a Network of ideal reactors model using detailed kinetic scheme of methane combustion - Mech 3.0. This neural network serves as a fast surrogate model for emissions assessment, enabling rapid optimization of low-emission combustor designs. The approach is suitable for digital twins and combustion control systems and is adaptable to alternative fuels like hydrogen and ammonia.

Rising environmental concerns and the depletion of fossil fuels increase the research into the use of alternative fuels in engines with minimal structural modifications. Liquefied petroleum gas (LPG) is a promising alternative due to its high octane rating and low carbon content. In this research, a high-compression diesel engine was converted to a spark-ignition (SI) engine fueled with LPG using 0/1 D numerical modeling with AVL Cruise M software. The model was validated with experimental data of the diesel regime. Applications with LPG are typically conducted at low compression ratios, and in this study, the conversion effects were investigated in a high-compression (17.5:1) engine. The parametric effects of start of combustion (SOC) timing on combustion characteristics, performance, and emissions were investigated.The converted LPG engine demonstrated approximately 13.7% higher power and 4.7% higher efficiency compared to the diesel regime. Delaying SOC from +0°CA ATDC to +15°CA ATDC reduced NOₓ by 79% but increased CO by 46%.

Diesel-electric locomotives remain the dominant mode of freight rail traction in many countries, relying heavily on petroleum-based fuels and significantly contributing to greenhouse gas and pollutant emissions. This study introduces the Well-to-Wheel Locomotive Emissions Assessment framework, grounded in ISO 14040/44 standards, offering a structured, scalable, and globally replicable method for assessing railway fuel strategies. Using real-world data from the Vitória-Minas Railway, five fuel scenarios were modeled, including blends of petroleum diesel (B10), biodiesel (B25), and liquefied natural gas (LNG). Although developed for Brazil, the framework accommodates diverse locomotive types, regional fuel chains, and operational conditions, making it suitable for application in other national contexts. The results showed that the most favorable scenario, an 80% LNG and 20% B25 blend, achieved reductions of 24.93% in CO 2 e, 36.09% in NOx, 45.23% in particulate matter, and 63.05% in SO 2 emissions compared with current operations. These findings could offer valuable guidance for transport authorities, infrastructure operators, and energy policy planners worldwide. By integrating upstream and downstream emissions, this research delivers practical, internationally relevant insights into cleaner rail transport solutions and advances the application of life cycle thinking in the freight sector.