Which one of the following is an example of a clean fuel?

Propane is widely recognized as a clean-burning fuel due to its low carbon content and high combustion efficiency. It was officially approved as a clean fuel under the 1990 Clean Air Act because it produces significantly fewer greenhouse gases and air pollutants compared to conventional fuels like gasoline and diesel. While it is a fossil fuel, its combustion results in minimal particulate matter and lower emissions of nitrogen oxides (NOx) and carbon monoxide [2]. In contrast, fuels like coke and petrol are associated with higher levels of soot, sulfur oxides, and nitrogen oxides, which are major environmental pollutants [2]. Petrol vehicles, for instance, require stringent emission norms like BS-VI to mitigate their high NOx and hydrocarbon output [4]. Propane's ability to burn with a clean flame and its lower life cycle greenhouse gas emissions make it the most suitable example of a clean fuel among the given options [2].

Sources

1. [1] https://www.epa.gov/sites/default/files/2020-09/documents/1.5_liquefied_petroleum_gas_combustion.pdf
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > Activity 4.4 > p. 70
3. [4] https://www.sciencedirect.com/topics/earth-and-planetary-sciences/coal-derived-liquids