15 - Eco friendly biofuels for CI engine applications

Abstract

Rising greenhouse gas emission levels and environmental pollution have had detrimental effects on the ecosystem and this has made a shift from fossil fuels imperative. Besides, the rapid depletion of fossil fuels and the finite nature of their sources is bound to result in serious fuel shortages in the near future. Consequently, development of alternative sources of energy that can partially replace the fossil fuels, without major modifications, in existing engines is of prime importance. Among many ecofriendly fuels, biofuels have been found to be promising candidates that can effectively substitute diesel in CI engines because their use as fuels serves dual purposes of reduced toxic exhaust emissions and safe disposal of residual wastes from food industries. Among many biofuels, biodiesels have gained popularity because of the similarity in properties of diesel and biodiesel. Lower carbon monoxide (CO), carbon dioxide and hydrocarbon emissions result from biodiesel as compared to diesel while nitrogen oxide emissions increase. But the usage of biodiesel has been limited because of their high viscosity and low temperature flow properties. To tackle this issue, alcohols possessing good combustion efficiencies and high oxygen content have been explored as eligible additives to biodiesel in CI engines. Alcohol usage increases NOx emissions while reducing CO, CO2, and HC emissions. Gaseous fuels such as compressed natural gas (CNG), liquefies petroleum gas (LPG), biogas and hydrogen gas have been used in dual fuel mode in CI engines to have a better combustion and reduced emissions. The hydrocarbon and CO emissions for the dual fuel mode has increases when compared to diesel mode, but nitrogen oxide emissions decrease. The usage of gaseous fuels has been limited because of the few modifications that needs to be done.