A Comprehensive Review on Oxygenated Fuel Additive Options for Unregulated Emission Reduction from Diesel Engines

Compared to petrol and diesel engines, higher fuel economy along with higher power output is obtainable from diesel engines. Further, it has better thermal efficiencies and torque characteristics. On the negative side, the diesel engines are a major source of both regulated and unregulated emissions causing deterioration in air quality causing greater health hazard. Therefore, there is an urgent need to mitigate the society from this peril. From the authors’ point of view compared to regulated emissions unregulated emissions should be tackled with greater zeal. There are three possibilities (i)to get rid of IC engines and to use electric vehicles,(ii)to discard present day petro diesel and go for hydrogen as a fuel,(iii)to use alternate source of energy like biodiesel and oxygenated additives to diesel. The third one is relatively easy, quick and viable since no major change to be incorporated to the millions of existing engines. In this chapter, a review on the option of using oxygenated fuel additives such as biodiesel, acetone–butanol–ethanol (ABE) solution and water-emulsion as additives to reduce unregulated emissions is carried out. From this review, it becomes clear that more systematic research is absolutely essential to come to a definite conclusion on unregulated emissions such as polycyclic aromatic hydrocarbons (PAHs), persistent organic compounds (POPs) and carbonyls. When biodiesel and/or ABE solution in the diesel blends is used emissions such as particulate matter (PM), CO, PAHs and POPs do reduce. However, in most cases, the NOx emission increases. Further, through this review, a combination of factors such as higher oxygen content, more complete combustion and cooling effect could be brought out. Unregulated pollutant emissions can be reduced considerably if diesel blend, which contains proper amount of biodiesel, ABE solution and a small amount of water (0.5%), is employed appropriately. This means that such green fuels exhibit excellent performance in both brake thermal efficiency (BTE) and NOx–PM trade-off and in significant emission reductions for PAHs and POPs. This chapter proposes a green diesel fuel blend not only for scientific study but also for future practical application.