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Renewable Fuels: A Key Step Towards Global Sustainability

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A: Sustainable Energy".

Deadline for manuscript submissions: 5 August 2025 | Viewed by 1352

Special Issue Editors


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Guest Editor
Escuela de Ingeniería y Arquitectura, Universidad de Zaragoza, María de Luna 3, 50018 Zaragoza, Spain
Interests: power to gas; energy storage; carbon capture
Special Issues, Collections and Topics in MDPI journals

E-Mail Website
Guest Editor
Escuela de Ingeniería y Arquitectura, Universidad de Zaragoza, María de Luna 3, 50018 Zaragoza, Spain
Interests: biomass; power-to-gas

Special Issue Information

Dear Colleagues,

Renewable fuels continue to gain attention as a key component in the global pursuit of sustainability, especially in reducing greenhouse gas emissions and addressing climate change. As the world transitions from reliance on fossil fuels to more sustainable energy sources, renewable fuels offer a practical and scalable solution for decarbonizing energy-intensive sectors, including transportation, industry, and power generation. These fuels are produced from natural, replenishable resources such as biomass, organic waste, algae, and renewable electricity, making them a sustainable alternative to conventional fossil fuels.

Around the world, biodiesel and ethanol are among the most widely used renewable fuels in the transport sector. This is because they can be easily blended with traditional fossil fuels in almost any proportion, allowing reduced carbon emissions and dependence on fossil fuels. Another key benefit of biofuels is their ability to integrate into existing fuel infrastructure, enabling their deployment without major changes to the current energy systems.

Other promising renewable fuels are biogas and biomethane, produced through the anaerobic digestion of organic waste. Notably, biomethane, a purified form of biogas with similar properties to natural gas, can be injected into existing natural gas grids. This makes biomethane an attractive option for decarbonizing sectors like heating and heavy industry, where electrification may be challenging.

Hydrogen is another renewable fuel with significant potential for sustainability when produced using renewable energy sources. Hydrogen is particularly promising in hard-to-electrify sectors. Additionally, hydrogen fuel cells provide a clean energy alternative for vehicles, offering longer ranges and faster refueling times than battery-electric vehicles, making them particularly suitable for heavy-duty transport.

The role of renewable fuels in combating climate change cannot be overstated. Compared to fossil fuels, renewable fuels significantly reduce carbon emissions. Moreover, they support the circular economy by repurposing waste materials and utilizing sustainable feedstocks, reducing the overall environmental impact of energy production. Renewable fuels can serve as a critical bridge technology to reduce carbon emissions in the short term in regions where the energy transition to full electrification is slower or technically infeasible.

However, the widespread adoption of renewable fuels faces several challenges. The production of biofuels and biogas often competes with food crops for land and water resources, raising concerns about food security and environmental degradation. In addition, the high production costs of renewable fuels, particularly hydrogen, remain a barrier to large-scale deployment.

Based on before, this Special Issue aims to present and disseminate the latest advancements in:

  • Biofuels in transportation;
  • Green hydrogen for industry;
  • Renewable fuels and carbon neutrality;
  • Biogas from organic waste;
  • Sustainability of biomass;
  • Challenges of renewable fuel production;
  • Renewable fuels for aviation;
  • Biomethane in power generation;
  • Policy support for renewable fuels .

Dr. Manuel Bailera
Dr. Alexander García Mariaca
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • biofuels
  • hydrogen
  • biogas
  • sustainability
  • decarbonization

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Published Papers (2 papers)

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Research

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15 pages, 2070 KiB  
Article
Performance and Emissions of Spark-Ignition Internal Combustion Engine Operating with Bioethanol–Gasoline Blends at High Altitudes Under Low- and High-Speed Conditions
by Alexander García Mariaca, Jorge Villalba, Rodrigo Morillo Castaño and Manuel Bailera
Energies 2025, 18(6), 1401; https://doi.org/10.3390/en18061401 - 12 Mar 2025
Viewed by 495
Abstract
Several countries have cities located at elevations above 2000 m. Consequently, the internal combustion engines (ICEs) that operate there do not achieve the desired performance and emissions under these atmospheric conditions. One approach to mitigate these effects and, at the same time, address [...] Read more.
Several countries have cities located at elevations above 2000 m. Consequently, the internal combustion engines (ICEs) that operate there do not achieve the desired performance and emissions under these atmospheric conditions. One approach to mitigate these effects and, at the same time, address climate change is the use of biofuel–fossil fuel blends. However, ICEs must operate under a wide range of rpm to meet varying workload demands, raising concerns that these fuel blends may not be fully effective in achieving the desired performance and emission outcomes under such conditions. To address this issue, a series of experimental tests were conducted at low and high rpm of a spark-ignition (SI) ICE fuelled with bioethanol–gasoline blends in the ratios of E10, E15, E20, E40, E60, E85, and E100. The tests were conducted at 2600 m above sea level (masl) under various engine loads. The E20 and E40 blends showed outstanding performance at 2700 rpm, achieving high brake power and low emissions of CO2 and HCs. At 4300 rpm, the E40 blend exhibited great performance because the engine produced high brake power and low emissions of CO and NOx. Based on these results, it can be concluded that bioethanol concentrations of between 20 and 40% in the blend effectively compensate for the reduced atmospheric oxygen at high altitudes, enhancing the combustion process in SI-ICEs. Full article
(This article belongs to the Special Issue Renewable Fuels: A Key Step Towards Global Sustainability)
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Review

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31 pages, 3781 KiB  
Review
Hydrogen Properties and Their Safety Implications for Experimental Testing of Wing Structure-Integrated Hydrogen Tanks
by Javed A. Butt and Johannes F. C. Markmiller
Energies 2025, 18(8), 1930; https://doi.org/10.3390/en18081930 - 10 Apr 2025
Viewed by 442
Abstract
Hydrogen is a promising candidate for addressing environmental challenges in aviation, yet its use in structural validation tests for Wing Structure-Integrated high-pressure Hydrogen Tanks (SWITHs) remains underexplored. To the best of the authors’ knowledge, this study represents [...] Read more.
Hydrogen is a promising candidate for addressing environmental challenges in aviation, yet its use in structural validation tests for Wing Structure-Integrated high-pressure Hydrogen Tanks (SWITHs) remains underexplored. To the best of the authors’ knowledge, this study represents the first attempt to assess the feasibility of conducting such tests with hydrogen at aircraft scales. It first introduces hydrogen’s general properties, followed by a detailed exploration of the potential hazards associated with its use, substantiated by experimental and simulation results. Key factors triggering risks, such as ignition and detonation, are identified, and methods to mitigate these risks are presented. While the findings affirm that hydrogen can be used safely in aviation if responsibly managed, they caution against immediate large-scale experimental testing of SWITHs due to current knowledge and technology limitations. To address this, a roadmap with two long-term objectives is outlined as follows: first, enabling structural validation tests at scales equivalent to large aircraft for certification; second, advancing simulation techniques to complement and eventually reduce reliance on costly experiments while ensuring sufficient accuracy for SWITH certification. This roadmap begins with smaller-scale experimental and numerical studies as an initial step. Full article
(This article belongs to the Special Issue Renewable Fuels: A Key Step Towards Global Sustainability)
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