Blending of additives with biodiesels to improve the cold flow properties, combustion and emission performance in a compression ignition engine—A review

Biodiesel is widely accepted as comparable fuel to diesel in compression ignition engines. It offers many advantages including: higher cetane number; reduced emissions of particulates, NOx, SOx, CO, and hydrocarbons; reduced toxicity; improved safety; and lower lifecycle CO2 emissions. A characteristic of biodiesel limiting its application is its relatively poor low-temperature flow properties. Improvement of its low temperature flow characteristic still remains one of the major challenges when using biodiesel as an alternative fuel for diesel engines. The biodiesel fuels derived from fats or oils with significant amounts of saturated fatty compounds display higher cloud points and pour points thus limiting their applications.The cold flow properties of different biodiesel were evaluated with various additives towards the objectives of improving the viscosity, pour point and cloud point. Methanol ethanol, kerosene, Mg additives, etc. have been tried many researchers to improve the cold flow behavior of biodiesels. Varying results of improvement in cold flow properties have been obtained by using different additives. Similarly different additives have been used by different researchers to improve the performance of a compression ignition engine and its emissions.This review has been taken up to identify the various additives used to improve the cold flow properties of biodiesels and improve the performance of a diesel engine and its emissions while using additive blended biodiesels. The review concludes that the additives usage in biodiesel is inseparable both for improving the cold flow properties and for the better engine performance and emission control and further research is needed to develop biodiesel specific additives.