Alternative Fuels in Spark Ignition Engines

Alternative fuels for spark ignition engines encompass a diverse array of oxygenated and renewable compounds, chiefly bioethanol, butanol, methanol and emerging candidates such as acetone and 2,5-dimethylfuran. These fuels are blended with conventional gasoline or used in higher proportions to raise the research octane number, improve combustion stability and reduce tailpipe emissions. Key metrics include brake specific fuel consumption (BSFC), brake thermal efficiency and pollutant emissions (CO, HC, NOx and particulate matter). While bioethanol is widely adopted due to its high octane rating and established supply chains, it suffers from lower energy density and hygroscopicity, which can increase fuel consumption and risk of phase separation. Butanol offers higher heating value and lower water affinity, enhancing engine performance and reducing corrosive wear. Methanol, with its simple molecular structure, presents a compelling route to carbon-neutral operation when produced renewably, but raises challenges in material compatibility. Advances in port-fuel injection and gasoline direct injection platforms have demonstrated that tailored fuel–engine calibration can unlock efficiency gains across variable load and speed conditions. Globally, these developments underpin strategies for decarbonisation of road transport, enabling existing engine architectures to meet tightening emission standards while leveraging non-fossil feedstocks.

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Alternative Fuels in Spark Ignition Engines publication trend

The graph below shows the total number of articles in alternative fuels in spark ignition engines across all publications each year (not limited to Nature Index journals).

Technical terms

Brake specific fuel consumption (BSFC): The mass or volume of fuel consumed per unit brake power output, typically expressed as g kW⁻¹ h⁻¹ or L kW⁻¹ h⁻¹.

Research octane number (RON): A standard index of a fuel’s resistance to knock under controlled engine conditions, higher values indicating better anti-knock quality.

Brake thermal efficiency: The ratio of brake power output to the chemical energy input of the fuel, indicating how effectively the engine converts fuel energy into mechanical work.

Spark ignition engine (SI engine): An internal combustion engine in which the air–fuel mixture is ignited by an electric spark, as opposed to compression ignition.

Gasoline direct injection (GDI): A fuel delivery system in which gasoline is injected directly into the combustion chamber, improving atomisation, efficiency and control of the combustion process.

References

1. Cost determination of using bioethanol to improve properties of Nigerian gasoline. Case Studies in Chemical and Environmental Engineering (2023).
2. Butanol-gasoline blends impact on performance and exhaust emissions of a four stroke spark ignition engine. Case Studies in Thermal Engineering (2023).
3. Investigation on Blending Effects of Gasoline Fuel with N-Butanol, DMF, and Ethanol on the Fuel Consumption and Harmful Emissions in a GDI Vehicle. Energies (2019).
4. An Experimental Study on the Potential Usage of Acetone as an Oxygenate Additive in PFI SI Engines. Energies (2016).
5. Theoretical Study of the Effects of Spark Timing on the Performance and Emissions of a Light-Duty Spark Ignited Engine Running under Either Gasoline or Ethanol or Butanol Fuel Operating Modes. Energies (2017).
6. State of Art of Using Biofuels in Spark Ignition Engines. Energies (2021).
7. Comparative Assessment of Ethanol and Methanol–Ethanol Blends with Gasoline in SI Engine for Sustainable Development. Sustainability (2023).