Abstract Global warming and energy insecurity have intensified the search for sustainable fuel alternatives to mitigate emissions from internal combustion engines. This study systematically reviews existing research on alternative fuels in Iraq and the Middle East, emphasizing ethanol–gasoline, biodiesel–diesel, and hydrogen–LPG blends. Using the PRISMA 2020 framework, 87 peer-reviewed studies from 2000 to 2025 were analyzed across Scopus, IEEE Xplore, Web of Science, ScienceDirect, and Google Scholar. Findings reveal that ethanol–gasoline blends (E10–E20) enhance brake thermal efficiency by up to 9% and reduce CO and HC emissions by 25%–50%, though higher ethanol ratios increase NOx. Biodiesel and ethanol–diesel mixtures significantly lower particulate matter and CO emissions, with cetane improvers (e.g. 2-ethylhexyl nitrate) further enhancing combustion stability. Hydrogen-enriched LPG fuels improve flame speed and efficiency but require optimized control to prevent instability. Despite these advances, Iraq’s outdated refining systems and fuel quality constraints hinder full adoption. The study concludes that integrating renewable blends with modern engine calibration can substantially reduce emissions and improve thermal performance, offering a viable transition pathway toward sustainable energy systems in Iraq.
Kadhim et al. (Thu,) studied this question.