Engine emissions with air pollutants and greenhouse gases and their control technologies

Diesel and gasoline are the most used fossil fuels due to their high energy release and low cost for engines. However, the emission of air pollutants and greenhouse gases has caused severe environmental issues, and emission regulations are becoming stricter. Recently, several advances in emission control technologies for fossil fuel engines have been available, which need to be reviewed to manifest future research. Here, we reviewed the primary pollutants emitted from the diesel and gasoline-powered engines, their formation process, and the present technologies to control the emissions of greenhouse gases and air pollutants, especially during the COVID-19 pandemic. In this regard, this review concentrates on a particular matter (PM2.5 and PM10), carbon monoxide (CO), nitrogen oxides (NOx), unburned hydrocarbons (UHC), and greenhouse gases (water vapor, CO2, N2O, etc.) as exhaust emissions, the difficulties they cause, and the strategies employed to reduce emissions. This review also provides a framework for understanding how to reduce air pollution and greenhouse gasses generated by diesel and gasoline-powered engines.