ROLE OF BIOFUELS IN REDUCING DIESEL ENGINE EMISSIONS: A SYSTEMATIC REVIEW

Diesel engines are widely used due to their high thermal efficiency and
reliability, but they contribute significantly to environmental pollution,
especially nitrogen oxides (NOx), particulate matter (PM), carbon monoxide
(CO), and unburned hydrocarbons (UHC). Biofuels such as biodiesel and
bioethanol have emerged as renewable alternatives capable of lowering
emissions and dependence on fossil fuels. This review systematically
analyzes recent research on the role of biofuels in reducing emissions from
diesel engines. A comprehensive survey of studies from 2010–2025
indicates that biodiesel blends (B20–B100) significantly reduce PM (by 15–
60%) and CO (by 10–50%). However, biodiesel can increase NOx by 2–15%
depending on blend ratio and engine conditions. The review also discusses
fuel properties, combustion characteristics, environmental impacts, and
challenges, presenting both quantitative and qualitative data.