A statistical investigation of biodiesel physical and chemical properties, and their correlation with the degree of unsaturation

In the present work, a detailed statistical investigation is conducted in order to a) assess the average values of all properties (incl. fatty acid composition) of the most investigated biodiesels and b) quantify the effects of feedstock unsaturation on the physical and chemical properties of the derived methyl ester. To this aim, the available literature on biodiesel properties and fatty acid composition was gathered (more than 750 papers published in International Journals and Conferences), and the reported measurements are statistically analyzed with respect to the feedstock and its chemical composition and structure; in total, 26 different biodiesel feedstocks are studied, comprising of twenty-two edible and non-edible vegetable oils and four animal fats. From the analysis, collective results and statistical data are derived for each property that are then compared with the European and American specifications. The effects of unsaturation are investigated with separate best-fit linear curves provided for each interesting property with respect to the average number of double bonds. The various trends observed are discussed and explained based on fundamental aspects of fuel chemistry and on the consequences they have on real engine operation. (C) 2012 Elsevier Ltd. All rights reserved.