Butanol and pentanol: The promising biofuels for CI engines – A review

Existing fossil fuels may not be able to meet the energy demand in near future due to rapid increase in oil consumption. Fluctuating oil prices, depleting oil reserves and high level of harmful emissions through the use of conventional diesel forced the research community to focus their attention on the use of biofuels in compression ignition (CI) engines. Extensive use of biofuels offer multitude of advantages such as social structure, self-sustainability, soil development, effective use of cultivable land and self-employment. Butanol and pentanol are the most attractive biofuels, which could relieve energy crisis and reduce carcinogenic particulate matter (PM) emissions that are customary in CI engines. Research in the recent past has witnessed the notable amount of study in the use of these alcohols, mainly because of the improved yield through modern fermentation processes. Present work reviews the literature on the effects of using butanol and pentanol on the combustion, performance and exhaust emissions of CI engines operating under various test conditions. Attention is paid towards the review of strategies employed for use of higher alcohols in neat or in blended form to increase the renewable fraction of fuels in CI engines. The combination of exhaust gas recirculation (EGR) rates, delayed injection and the use of higher alcohols can enable low temperature combustion (LTC) strategy in CI engines, which presents simultaneous reduction in oxides of nitrogen (NOx) and soot emissions with increased efficiency. This paper also summarizes the key findings of earlier researchers contributed for use of biofuels in CI engines emphasizing higher alcohols. These biofuels are potential and attractive alternatives for the use in CI engines for improved performance and substantial reduction of harmful emissions.