Diesel engines are internal combustion engines characterized by high compression ratios and direct fuel injection, eliminating the need for spark plugs. They operate at high temperatures, resulting in high thermal efficiency and fuel economy. The future trends in diesel technology include increased use of biofuels and synthetic fuels to reduce CO2 emissions, advancements in Selective Catalytic Reduction (SCR) systems to lower NOx emissions significantly, and a growing market share for diesel-electric hybrid systems improving fuel efficiency and reducing noise pollution. Diesel engines produce emissions such as polycyclic aromatic hydrocarbons (PAHs), nitrogen oxides (NOx), and particulate matter (PM), which pose significant environmental and health challenges. Effective emission control technologies are crucial for mitigating these effects.