Explore the vast range of titles available.

As the push for carbon-neutral transport continues, the aviation sector is facing increasing pressure to reduce its carbon footprint. Furthermore, commercial air traffic is expected to resume the continuous growth experienced until the pandemic, highlighting the need for reduced emissions. The use of alternative fuels plays a key role in achieving future emission goals, while also lowering the dependency on fossil fuels. The so-called sustainable aviation fuels (SAF), which encompass bio and synthetic fuels, are currently the most viable option, but hydrogen is also being considered as a long-term solution. The present paper reviews the production methods, logistical and technological barriers, and potential for future mass implementation of these alternative fuels. In general, biofuels currently present higher technological readiness levels than other alternatives. Sustainable mass production faces critical feedstock-related challenges that synthetic fuels, together with other solutions, can overcome. All conventional fuel replacements, though with different scopes, will be important in meeting long-term goals. Government support will play an important role in accelerating and facilitating the transition towards sustainable aviation.

Lignin is an abundant source of renewable aromatics that has long been targeted for valorization. Traditionally, the inherent heterogeneity and reactivity of lignin has relegated it to direct combustion, but its higher energy density compared with polysaccharides makes it an ideal candidate for biofuel production. This Review critically assesses lignin’s potential as a substrate for sustainable aviation fuel blendstocks. Lignin can generate the necessary cyclic compounds for a fully renewable, sustainable aviation fuel when integrated with current paraffinic blends and can meet the current demand 2.5 times over. Using an energy-centric analysis, we show that lignin conversion technologies have the near-term potential to match the enthalpic yields of existing commercial sustainable aviation fuel production processes. Key factors influencing the viability of technologies for converting lignin to sustainable aviation fuel include lignin structure, delignification extent, depolymerization performance, and the development of stable and tunable deoxygenation catalysts. Lignin is an abundant source of renewable aromatic carbon and is of interest as a feedstock for sustainable fuels. This Review provides an overview of production technologies, jet fuel requirements, effects of lignin chemistry, depolymerization techniques, upgrading of bio-oils and challenges for catalysis using real biomass feedstocks.

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.

Aviation fuels are essential for flight transportation. The increasing demand for such fuels threatens the present efforts to mitigate global warming. Changing to renewable energy sources and hydrogen to drive airplanes is not ready and will take a few decades. Therefore, alternative fuels such as sustainable aviation fuels (SAFs, also so-called bio-jet fuels) could play an excellent role in mitigating greenhouse emissions. SAFs encompass blends of bio and synthetic fuels. Some SAF pathways have already been certified (such as oil-to-jet, alcohol-to-jet, gas-to-jet, and sugar-to-jet), and some are on the way to being certified. This review starts by providing a detailed overview of the current status of aviation fuels, including their growth, types, and emission trends. After that, it comprehensively delves into a thorough discussion of SAFs, covering various aspects such as their types, combustion properties, production technologies and pathways, cost evolution, and life cycle assessments. The paper discusses the SAFs’ future prospects while providing practical recommendations based on the analysis. It was shown that the oil-to-fuel (HEFA) pathway is more mature with less carbon emissions. SAFs face challenges, including high costs, limited production scale, feedstock availability, energy-intensive production methods, land-use competition, potential indirect environmental impacts, certification standards, infrastructure, and public acceptance. Much research is needed to reduce SAF costs substantially less than conventional aviation fuels.

Modern aviation is one of the main consumers of petroleum-based fuels, consuming nearly 100 million gallons of fuel per year, and this consumption continues to grow. On the other hand, airlines have committed to achieving net-zero carbon dioxide (CO2) emissions in the industry by 2050. Fulfilling this commitment necessitates the investigation of new and the optimization of existing processes for the production of alternative, renewable, and environmentally safe feedstocks. This article was prepared as part of the research project “Development of Technological Solutions for Obtaining Composite Motor Fuels from Secondary Raw Materials to Enhance Energy Security”.

This comprehensive review examines the role of sustainable aviation fuels (SAFs) in promoting a more environmentally responsible aviation industry. This study explores various types of biofuels, including hydroprocessed esters and fatty acids (HEFAs), Fischer–Tropsch (FT) fuels, alcohol-to-jet (ATJ) fuels, and oil derived from algae. Technological advancements in production and processing have enabled SAF to offer significant reductions in greenhouse gas emissions and other pollutants, contributing to a cleaner environment and better air quality. The review addresses the environmental, economic, and technical benefits of SAF, as well as the challenges associated with their adoption. Lifecycle analyses are used to assess the net environmental benefits of SAF, with a focus on feedstock sustainability, energy efficiency, and potential impacts on biodiversity and land use. Challenges such as economic viability, scalability, and regulatory compliance are discussed, with emphasis on the need for supportive policies and international collaboration to ensure the long-term sustainability of SAF. This study also explores current applications of SAF in commercial airlines and military settings, highlighting successful case studies and regional differences driven by policy frameworks and government incentives. By promoting technological innovation and addressing regulatory and economic barriers, SAF has the potential to play a crucial role in the aviation industry’s transition toward sustainability.

The continuous fossil fuel exhaustion, as well as the increasing environmental challenges that are occurring globally, has underscored the need for research on alternative pathways of producing biofuels that will minimize aviation emissions over the next decades. The present review explores the employment of diverse waste sources as feedstock and enzymes as catalysts as environmentally friendly methods for producing sustainable aviation fuels (SAF). To achieve this goal, a comprehensive review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. The results demonstrated that waste feedstocks catalyzed by enzymes represent an innovative alternative for SAF production. Specifically, the combination of enzymatic hydrolysis and microbial fermentation demonstrated considerable effectiveness in transforming complex waste feedstocks, such as lignocellulosic biomass, municipal solid waste, and food waste, into SAF precursors, including bio-isobutene and fatty acid methyl esters. Moreover, employing fatty acid photodecarboxylase enzymes for photoenzymatic decarboxylation demonstrated significant conversion efficiency, particularly under gentle conditions, low energy consumption and remarkable selectivity. However, further research and development of the reviewed methods are necessary to enable the industrialization of these technologies.

Background The economic viability of hydrodeoxygenation process using Camelina, Carinata and Jatropha feedstocks for aviation biofuel production was evaluated for two product profiles: (i) maximum diesel production and (ii) maximum jet fuel production (HRJ). Results Deterministic analysis of Camelina and Carinata diesel facilities returned positive NPVs and IRRs of 25 and 18%, respectively. Stochastic analysis suggested that the probabilities of positive NPVs were 75, 59 and 15%, respectively, for Camelina, Carinata and Jatropha diesel plants. Jet fuel facilities presented probabilities of loss of 98, 99 and 100% for Camelina, Carinata and Jatropha scenarios, respectively. Sensitivity analysis determined that financial performance was majorly influenced by feedstock and fuel prices. Categories of subsidies to enhance the attractiveness of the projects were studied. Conclusions Camelina, Carinata and Jatropha plants targeting HRJ required incentives of 0.31, 0.39 and 0.61 US$/L of biofuel produced, respectively, to reduce the probabilities of loss to approximately 30%.

The present work provides an analysis of the potential impact of fossil-based Low Carbon Aviation Fuels (LCAF) for the European aviation sector, with a time horizon to 2050. LCAF are a crude-derived alternative to kerosene, offering some Green House Gas (GHG) savings, and have been defined by ICAO as eligible fuels for mitigating the environmental impact of aviation. A methodological framework to evaluate the EU technical potential for LCAF production is developed, based on data on crude utilization for jet fuel production in EU refineries, relevant carbon intensity reduction technologies, market prices, and aviation fuel volumes. Two different baselines for fossil-derived kerosene carbon intensity (CI) are considered: a global figure of 89 gCO2e/MJ and an EU-27-specific one of 93.1 gCO2eq/MJ. Three scenarios considering increasing levels of CI reduction are then defined, taking into account the current and potential commercial availability of some of the most relevant carbon intensity reduction technologies. The analysis demonstrates that, even if LCAF could offer GHG saving opportunities, their possible impact, especially when compared to the ambition level set in the most recent European legislative proposals, is very limited in most of the analysed scenarios, with the exception of the most ambitious ones. At 2030, a non-zero technical potential is projected only in the higher CI reduction scenario, ranging between 1.8% and 14.2% of LCAF market share in the EU-27 (equal to 0.6 to 4.75 Mtoe), depending on the considered Baseline for CI. At 2050, almost all considered scenarios project a larger technical potential, ranging between 6.9% and 22.2% for the global Baseline (2.21 to 7.13 Mtoe), and between 1.8% and 16.2% for the EU-27 Baseline (0.58 to 5.2 Mtoe). LCAF additional costs to current production costs are also discussed, given their relevance in large-scale deployment of these technologies, and are projected to range between 39 and 46.8 USD/toe.

Sustainable aviation fuel (SAF) is anticipated to have a significant impact on decarbonizing the aviation industry owing to its ability to be seamlessly incorporated into the current aviation infrastructure. This paper analyzes the potential of meeting the proposed SAF targets set by the ReFuelEU initiative. The approved SAF production pathways according to ASTM D7566 using renewable bio-based feedstocks were defined and analyzed. Moreover, a detailed matrix for comparison was used to provide an overview of the current state of those pathways. The analysis has shown that hydroprocessed esters of fatty acids (HEFA), alcohol to jet (ATJ), and Fischer–Tropsch (FT-SPK) are the most promising pathways in the foreseeable future due to their high technology readiness and fuel levels. HEFA is the most mature and affordable pathway; therefore, it is expected to form the backbone of the industry and stimulate the market in the short term despite its low sustainability credentials, limited feedstock, and geopolitical implications. On the other hand, FT-SPK can utilize various feedstocks and has the lowest greenhouse gas emissions with around 7.7 to 12.2 gCO2e/MJ compared to the conventional jet fuel baseline of 89 gCO2e/MJ. Overall, the EU has enough sustainable feedstocks to meet the short-term SAF targets using the current technologies. In the long term, the reliability and availability of biomass feedstocks are expected to diminish, leading to a projected deficit of 1.35 Mt in SAF production from bio-based feedstocks. Consequently, a further policy framework is needed to divert more biomass from other sectors toward SAF production. Moreover, a significant investment in R&D is necessary to improve process efficiencies and push new technologies such as power-to-liquid toward commercial operation.