Search Results (60)

Sustainable aviation fuels (SAFs) are vitally important for aviation decarbonization. The laminar burning velocity (LBV), a key parameter reflecting the combustion behavior of fuel/oxidizer mixtures, serves as a fundamental metric for evaluating SAF performance. This paper systematically reviews and evaluates the LBV experiment method and the performance of traditional aviation fuel, SAFs produced via different pathways, and individual components (n-alkanes, iso-alkanes, cycloalkanes, and aromatic hydrocarbons, as well as the impacts of isomers and homologues) in aviation fuels. It is found that LBV values of different SAFs exhibit significant fluctuations, approaching or slightly deviating from those of conventional aviation fuels. Carbon number, branching degree, substituent types, and testing methods in the components all affect LBV performance. Specifically, increased branching in iso-alkanes reduces LBV, cyclohexane and benzene show higher LBV than their methylated counterparts (methylcyclohexane and toluene), and n-alkylcyclohexanes/benzenes with short (C1–C3) side chains demonstrate minimal LBV variation. Spherical flame methods yield more consistent (and generally lower) LBV values than stagnation flame techniques. These findings provide insights for optimizing SAF–conventional fuel blends and enhancing drop-in compatibility while ensuring operational safety and usability. Full article

The generation of fine coal particles during mining and processing presents significant environmental and logistical challenges, particularly in coal-dependent, developing countries like South Africa (SA). This review critically evaluates the technical viability of fine coal briquetting as a sustainable waste-to-energy solution within a SA context, while drawing from global best practices and comparative benchmarks. It examines abundant feedstocks that can be used for valorization strategies, including fine coal and agricultural biomass residues. Furthermore, binder types, manufacturing parameters, and quality optimization strategies that influence briquette performance are assessed. The co-densification of fine coal with biomass offers a means to enhance combustion efficiency, reduce dust emissions, and convert low-value waste into a high-calorific, manageable fuel. Attention is also given to briquette testing standards (i.e., South African Bureau of Standards, ASTM International, and International Organization of Standardization) and end-use applications across domestic, industrial, and off-grid settings. Moreover, the review explores socio-economic implications, including rural job creation, energy poverty alleviation, and the potential role of briquetting in SA’s ‘Just Energy Transition’ (JET). This paper uniquely integrates technical analysis with policy relevance, rural energy needs, and practical challenges specific to South Africa, while offering a structured framework for bio-coal briquetting adoption in developing countries. While technical and economic barriers remain, such as binder costs and feedstock variability, the integration of briquetting into circular economy frameworks represents a promising path toward cleaner, decentralized energy and coal waste valorization. Full article

The increasing global demand for sustainable energy solutions has intensified the need to replace fossil fuels in gas turbines, particularly in aviation and power generation where alternatives to gas turbines are currently limited. This review explores the feasibility of utilizing sustainable liquid and gaseous fuels in gas turbines by evaluating their environmental impacts, performance characteristics, and technical integration potential. The study examines a broad range of alternatives, including biofuels, hydrogen, alcohols, ethers, synthetic fuels, and biogas, focusing on their production methods, combustion behavior, and compatibility with existing turbine technology. Key findings indicate that several bio-derived and synthetic fuels can serve as viable drop-in replacements for conventional jet fuels, especially under ASTM D7566 standards. Hydrogen and other gaseous alternatives show promise for industrial applications but require significant combustion system adaptations. The study concludes that a transition to sustainable fuels in gas turbines is achievable through coordinated advancements in combustion technology, fuel infrastructure, and regulatory support, thus enabling meaningful reductions in greenhouse gas emissions and advancing global decarbonization efforts. Full article

To address global climate change and the energy crisis, there is an urgent need to meet human demands through utilizing renewable energy sources. The deoxygenation of lipids to produce liquid biofuels has emerged as a promising alternative, particularly for carbon emission reduction in the aviation industry. This review critically examines recent progress in catalyst development and reaction control strategies for lipid deoxygenation. Emphasis is focused on the design of different kinds of catalysts to meet the requirements, including noble metal catalysts, non-noble metal catalysts, and non-noble metal compound catalysts, with strategies such as morphology control, utilization of metal support interactions, and constructing synergistic effects between metal acid centers and metal oxygen vacancies. The reaction networks, mechanisms, and selectivity control strategies for lipid deoxygenation, cracking, isomerization, and aromatization are comprehensively discussed. Finally, we propose that it requires focusing on the precise regulation of multiple active sites to optimizing deoxygenation performance and reusability. It is essential to integrate in situ characterization to deepen the study of structure–active relationships and explore the reaction mechanisms within complex reaction systems. Full article

In the last five years, the use of hydrogen as an energy carrier has received rising attention because it can be used in internal combustion and jet engines, and it can even generate electricity in fuel cells. The scope of this work was to critically review the methods of H₂ production from renewable and non-renewable sources, with a focus on bio-H₂ production from the perennial grass giant reed (Arundo donax L.) due to its outstanding biomass yield. This lignocellulosic biomass appears as a promising feedstock for bio-H₂ production, with a higher yield in dark fermentation than photo-fermentation (217 vs. 87 mL H₂ g⁻¹ volatile solids on average). The H₂ production can reach 202 m³ Mg⁻¹ of giant reed dry matter. Assuming the average giant reed dry biomass yield (30.3 Mg ha⁻¹ y⁻¹), the attainable H₂ yield could be 6060 m³ ha⁻¹ y⁻¹. A synthetic but comprehensive review of methods of H₂ production from non-renewable sources is first presented, and then a more detailed analysis of renewable sources is discussed with emphasis on giant reed. Perspectives and challenges of bio-H₂ production, including storage and transportation, are also discussed. Full article

The co-production of BHD with other renewable fuels (i.e., using a novel process involving carbon dioxide utilization to achieve the global sustainability goal) is presented. The three configurations of BHD production from refined bleached deodorized palm oil (RBDPO), including (1) the conventional BHD process with hydrogen recovery (BHD process), (2) the BHD process coupled with the Fischer–Tropsch process (BHD-FT process), and (3) the BHD process coupled with the bio-jet fuel and methanol processes (BHD-BIOJET-MEOH process) are investigated using the process model developed in Aspen Plus. The effect of the operating parameters is studied, and the condition of each process offering the highest BHD yield is proposed. Then, the pinch analysis and heat exchanger network (HEN) design of each proposed process are performed to find the highest energy-efficient configuration. The economic and environmental analysis is later performed to investigate the sustainability performance of each configuration. The conventional BHD process requires less hydrogen and consumes less energy than the others. The BHD-BIOJET-MEOH process is the most economically feasible, offering the highest net present value (NPV) of USD 7.93 million and the shortest payback period of 3 years and 1 month. However, it offers the highest carbon footprint of 0.820 kgCO₂ eq./kg of BHD, and it presented the highest potential environmental impact (PEI) in all categories. Full article

This paper investigates how the present paths support massive manufacturing by evaluating the existing state of sustainable aviation fuel (SAF) technologies, examining technology readiness levels (TRL), fuel readiness levels (FRL), costs, economic conditions, emissions, etc. This assessment summarizes major conclusions about bio-jet replacements for conventional jet fuels. In order for SAF to play a sustainable role, a full life cycle emissions assessment, techno-economic analysis (TEA), and discussions about the sustainability of SAF materials are required. The life cycle assessment (LCA) discusses the capability of SAF in cutting down emissions, TEA argues for its economic viability, and the sustainable supply of SAF feedstock is a third critical factor determining the sustainability of the industry. With all the analyses, this overview provides recommendations for the sustainable development of the SAF industry and calls on industry stakeholders to enhance cooperation. Full article

This study presents an efficient process for producing sustainable aviation fuel (SAF) from soybean oil through hydrodeoxygenation (HDO) and hydroisomerization (HI). The research utilized a commercial nickel catalyst for the HDO step, and a newly developed platinum catalyst supported on SAPO-11 zeolite for the hydroisomerization (HI) stage. The process parameters, including temperature and pressure, were optimized to maximize conversion efficiency and meet ASTM D7566 standards. The results indicate that the HDO process using the nickel catalyst achieved a high yield of n-alkanes (97.8% ± 0.4%) with complete conversion of triglycerides. In the subsequent hydroisomerization step, the platinum catalyst demonstrated excellent selectivity for Jet-A1 fuel, yielding a bio-jet fraction of 87.5% ± 1.6% in a 200 h continuous test. This study also highlights the minimal coking phenomena and high catalyst stability throughout the process. This work suggests that soybean oil, as a readily available feedstock, could significantly contribute to the production of SAF and reduce greenhouse gas emissions in the aviation sector. Additionally, the optimization of temperature and pressure conditions is crucial for enhancing the yield and quality of the final bio-jet product. Full article

Aviation is of crucial importance for the transportation sector and fundamental for the economy as it facilitates trade and private travel. Nonetheless, this sector is responsible for a great amount of global carbon dioxide emissions, exceeding 920 million tonnes annually. Alternative energy fuels (AEFs) can be considered as a promising solution to tackle this issue, with the potential to lower greenhouse gas emissions and reduce reliance on fossil fuels in the aviation industry. A life cycle analysis is performed considering an aircraft running on conventional jet fuel and various alternative fuels (biojet, methanol and DME), including hydrogen and ammonia. The comparative assessment investigates different fuel production pathways, including the following: JETA-1 and biojet fuels via hydrotreated esters and fatty acids (HEFAs), as well as hydrogen and ammonia employing water electrolysis using wind and solar photovoltaic collectors. The outputs of the assessment are quantified in terms of carbon dioxide equivalent emissions, acidification, eutrophication, eco-toxicity, human toxicity and carcinogens. The life cycle phases included the following: (i) the construction, maintenance and disposal of airports; (ii) the operation and maintenance of aircrafts; and (iii) the production, transportation and utilisation of aviation fuel in aircrafts. The results suggest that hydrogen is a more environmentally benign alternative compared to JETA-1, biojet fuel, methanol, DME and ammonia. Full article

Biofuels’ induced land-use change (ILUC) emissions have been widely studied over the past 15 years. Many studies have addressed uncertainties associated with these estimates. These studies have broadly examined uncertainties associated with the choice of economic models, their assumptions and parameters, and a few bio-physical variables. However, uncertainties in land-use emission factors that represent the soil and vegetation carbon contents of various land types across the world and are used to estimate carbon fluxes due to land conversions are mostly overlooked. This paper calls attention to this important omission. It highlights some important sources of uncertainty in land-use emissions factors, explores the range in these factors from established data sources, and compares the influence of their variability on ILUC emissions for several sustainable aviation fuel (SAF) pathways. The estimated land-use changes for each pathway are taken from a well-known computable general equilibrium model, GTAP-BIO. Two well-known carbon calculator models (CCLUB and AEZ-EF) that represent two different sets of emissions factors are used to convert the GTAP-BIO estimated land-use changes to ILUC emissions. The results show that the calculated ILUC emissions obtained from these carbon calculators for each examined SAF pathway are largely different, even for the same amortization time horizon. For example, the ILUC emissions values obtained from the AEZ-EF and CCLUB models for producing jet fuel from corn ethanol for a 25-year amortization period are 24.9 gCO₂e/MJ and 15.96 gCO₂e/MJ, respectively. This represents a 60% difference between the results of these two carbon calculators for the same set of land-use changes. The results show larger differences for other pathways as well. Full article

The aeronautical sector faces challenges in meeting its net-zero ambition by 2050. To achieve this target, much effort has been devoted to exploring sustainable aviation fuels (SAF). Accordingly, we evaluated the technical performance of potential SAF production in an integrated first- and second-generation sugarcane biorefinery focusing on Brazil. The CO₂ equivalent and the renewability exergy indexes were used to assess environmental performance and impact throughout the supply chain. In addition, exergy efficiency (η_B) and average unitary exergy costs (AUEC) were used as complementary metrics to carry out a multi-criteria approach to determine the overall performance of the biorefinery pathways. The production capacity assumed for this analysis covers 10% of the fuel demand in 2020 at the international Brazilian airports of São Paulo and Rio de Janeiro, leading to a base capacity of 210 kt jet fuel/y. The process design includes sugarcane bagasse and straw as the feedstock of the biochemical processes, including diverse pre-treatment methods to convert lignocellulosic resources to biojet fuel, and lignin upgrade alternatives (cogeneration, fast pyrolysis, and gasification Fischer-Tropsch). The environmental analysis for all scenarios shows a GHG reduction potential due to a decrease of up to 30% in the CO₂ equivalent exergy base emissions compared to fossil-based jet fuel. Full article

Jet fuel production is a key element in the aviation industry’s strategy to reduce operating costs and environmental impacts. Alternatives are required, and bioturbosine obtained from biomass can replace significant amounts of jet fuel. In this investigation, the properties of the production of bioturbosine from coconut oil and mixtures of B5, B10, B20, B1OO, bottom, and jet fuel were measured according to the ASTM standards. A transesterification reaction between coconut oil and methanol was carried out using ultrasound, resulting in 99.93% conversion of triglycerides into bioturbosine at room temperature for 10 min, with a 6:1 molar ratio of methanol and oil. The catalyst concentration was 1.0 g/100 g of oil, and purification was carried out without water using an ion-exchange resin to remove impurities. The results obtained for density and viscosity were within the regulations. The temperature of the clogging point for a cold filter in the mixtures was up to −30 °C. The average caloric values of mixtures B5, B10, and B20 were 45,042, 44,546, and 43,611 MJ/Kg, respectively. In a copper corrosion test, the result for all samples was class 1A. It is expected that the results of this research may influence the use of bioturbosine in the aviation industry. Full article

A series of bifunctional catalysts, MoS₂/Al₂O₃ (70 wt.%), zeolite (30 wt.%) (zeolite—ZSM-5, ZSM-12, and ZSM-22), and silica aluminophosphate SAPO-11, were synthesized for hydroconversion of methyl palmitate (10 wt.% in dodecane) in a trickle-bed reactor. Mo loading was about 7 wt.%. Catalysts and supports were characterized by different physical-chemical methods (HRTEM-EDX, SEM-EDX, XRD, N₂ physisorption, and FTIR spectroscopy). Hydroprocessing was performed at a temperature of 250–350 °C, hydrogen pressure of 3.0–5.0 MPa, liquid hourly space velocity (LHSV) of 36 h⁻¹, and an H₂/feed ratio of 600 Nm³/m³. Complete conversion of oxygen-containing compounds was achieved at 310 °C in the presence of MoS₂/Al₂O₃-zeolite catalysts; the selectivity for the conversion of methyl palmitate via the ‘direct’ hydrodeoxygenation (HDO) route was over 85%. The yield of iso-alkanes gradually increases in order: MoS₂/Al₂O₃ < MoS₂/Al₂O₃-ZSM-12 < MoS₂/Al₂O₃-ZSM-5 < MoS₂/Al₂O₃-SAPO-11 < MoS₂/Al₂O₃-ZSM-22. The sample MoS₂/Al₂O₃-ZSM-22 demonstrated the highest yield of iso-alkanes (40%). The hydroisomerization activity of the catalysts was in good correlation with the concentration of Brønsted acid sites in the synthesized supports. Full article

In this work, microbial lipid production from non-detoxified Eucalyptus bark hydrolysate (EBH) with oleaginous xylose-utilizing Ashbya gossypii strains was explored. The best producing strain from a set of engineered strains was identified in synthetic media mimicking the composition of the non-detoxified EBH (SM), the lipid profile was characterized, and yeast extract and corn steep liquor (CSL) were pinpointed as supplements enabling a good balance between lipid accumulation, biomass production, and autolysis by A. gossypii. The potential of the engineered A. gossypii A877 strain to produce lipids was further validated and optimized with minimally processed inhibitor-containing hydrolysate and high sugar concentration, and scaled up in a 2 L bioreactor. Lipid production from non-detoxified EBH supplemented with CSL reached a lipid titer of 1.42 g/L, paving the way for sustainable single-cell oil production within the concept of circular economy and placing lipids as an alternative by-product within microbial biorefineries. Full article

The aviation industry is a significant contributor to global carbon dioxide emissions, with over 920 million tonnes per year, and there is a growing need to reduce its environmental impact. The production of biojet fuel from renewable biomass feedstocks presents a promising solution to address this challenge, with the potential to reduce greenhouse gas emissions and dependence on fossil fuels in the aviation sector. This review provides an in-depth discussion of current and emerging biojet fuel conversion technologies, their feasibility, and their sustainability, focusing on the promising conversion pathways: lipids-to-jet, sugar-to-jet, gas-to-jet, alcohol-to-jet, and whole biomass-to-jet. Each technology is discussed in terms of its associated feedstocks, important chemistries, and processing steps, with focus on recent innovations to improve yields of biojet product at the required specifications. In addition, the emerging power-to-liquid technology is briefly introduced. With the integrated biorefinery approach, consideration is given to biomass pretreatment to obtain specific feedstocks for the specific technology to obtain the final product, with the embedded environmental sustainability requirements. In addition, the review highlights the challenges associated with the biojet production technologies, with embedded suggestions of future research directions to advance the development of this important and fast-growing sustainable fuel industry. Full article