Biodiesel production using chemical and biological methods - A review of process, catalyst, acyl acceptor, source and process variables

The indiscriminate extraction and consumption of fossil fuels have left the world with a corner kick into the area of exponential fuel demand and now the race is on for alternate energy source. The fortunate improvements in Biodiesel fuel production techniques has been the heading topic of economic and environment sustainability so far. Biodiesel have the potential to replace diesel in vehicle engines. It has been tested and proved that engines running on biodiesel have shown low smoke emission and low toxic gas emission. Biodiesel properties such as oxidation stability, cloud point, iodine value, linoleic acid and poly-unsaturated fatty acid methyl ester content of biodiesel are dependent upon the quality of the feedstock. Processing parameters such as density, viscosity, acid value, distillation property are dependent on feedstock as well as the reaction conditions or the extent of reaction. Combustion property greatly varies with the substrates used and almost all the varieties have been proven to be as superior as that of conventional diesel fuel. Though the existing fossil and terrestrial biomass based oil cannot realistically satisfy the existing demands, algal oil source scores the most out of demanded factors like oil content, extractability, comfortable cultivation and efficient biomass production. Algae are a diverse group of plant like microorganisms, prokaryotic and eukaryotic, mostly autotrophic in nature with basic requirement such as CO2 and light for their normal growth and metabolic activity. Being micro scaled in physiology, most species of algae have less doubling time and the oil productivity greatly exceeds the outcome of best oil producing crops which clearly portrays that microalgae acts as a renewable source and can yield enough amount of oil for biodiesel production to meet the present intensifying demands. This article aims at reviewing the technical aspects of various biodiesel production methods from diverse oil feedstocks, their importance and significance of microalgal, process availability, commercialization potential of various processes. (C) 2014 Elsevier Ltd. All rights reserved.