The DOI matches its Crossref record; 111 of the 111 references it cites were found in a registry or an index.
Ammonia as Green Fuel in Internal Combustion Engines: State-of-the-Art and Future Perspectives
Open accessAbstract
Ammonia (NH 3 ) is among the largest-volume chemicals produced and distributed in the world and is mainly known for its use as a fertilizer in the agricultural sector. In recent years, it has sparked interest in the possibility of working as a high-quality energy carrier and as a carbon-free fuel in internal combustion engines (ICEs). This review aimed to provide an overview of the research on the use of green ammonia as an alternative fuel for ICEs with a look to the future on possible applications and practical solutions to related problems. First of all, the ammonia production process is discussed. Present ammonia production is not a “green” process; the synthesis occurs starting from gaseous hydrogen currently produced from hydrocarbons. Some ways to produce green ammonia are reviewed and discussed. Then, the chemical and physical properties of ammonia as a fuel are described and explained in order to identify the main pros and cons of its use in combustion systems. Then, the most viable solutions for fueling internal combustion engines with ammonia are discussed. When using pure ammonia, high boost pressure and compression ratio are required to compensate for the low ammonia flame speed. In spark-ignition engines, adding hydrogen to ammonia helps in speeding up the flame front propagation and stabilizing the combustion. In compression-ignition engines, ammonia can be successfully used in dual-fuel mode with diesel. On the contrary, an increase in NOx and the unburned NH 3 at the exhaust require the installation of apposite aftertreatment systems. Therefore, the use of ammonia seems to be more practicable for marine or stationary engine application where space constraints are not a problem. In conclusion, this review points out that ammonia has excellent potential to play a significant role as a sustainable fuel for the future in both retrofitted and new engines. However, significant further research and development activities are required before being able to consider large-scale industrial production of green ammonia. Moreover, uncertainties remain about ammonia safe and effective use and some technical issues need to be addressed to overcome poor combustion properties for utilization as a direct substitute for standard fuels.
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“Ammonia's versatility allows it to be utilized as a fuel in various energy conversion systems, including direct use in ICEs and gas turbines for power generation or decomposition back into hydrogen and nitrogen for use in fuel cells [304].”
From Biofuels, E-Fuels, and Waste-Derived Fuels: Advances, Challenges, and Future Directions (2025) · cites this paper as [304]
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Green ammonia production: Process technologies and challenges
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Metadata
- Authors
- Tornatore, C., Marchitto, L., Sabia, P., & De Joannon, M.
- Affiliations
- National Research Council (IT)
- Corresponding author
- Marchitto, Luca
- Venue
- Frontiers in Mechanical Engineering
- Publisher
- Frontiers Media SA
- Published
- 2022-07-22
- Volume
- 8
- ISSN
- 2297-3079 (ISSN-L)
- OpenAlex
- W4286697497
- Cited by
- 204
- References
- 110
- Citations by year
- 2026: 51 · 2025: 75 · 2024: 54 · 2023: 24
- FWCI
- 15.11
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- Locations
- Frontiers in Mechanical Engineering (publishedVersion, cc-by)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
- Topics
- Physical Sciences › Chemical Engineering › Fluid Flow and Transfer Processes › Advanced Combustion Engine Technologies
- Physical Sciences › Engineering › Computational Mechanics › Combustion and flame dynamics
- Physical Sciences › Energy › Fuel Technology › Biodiesel Production and Applications
- Keywords
- ammonia fuel, green ammonia, internal combustion engines, ammonia synthesis, hydrogen production, flame speed, spark ignition engine, compression ignition engine, NOx emissions, unburned ammonia, aftertreatment systems, marine engines, stationary engines, carbon-free fuels, engine retrofitting
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