Submitted to: Progress in Energy and Combustion Science (PECS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2016
Publication Date: 11/9/2016
Publication URL: https://handle.nal.usda.gov/10113/5695403
Citation: Knothe, G.H., Razon, L.F. 2016. Biodiesel fuels. Progress in Energy and Combustion Science (PECS). 58:36-59.

Interpretive Summary: Many plant oils, for example soybean, canola, palm, and other oils, as well as other materials, for example used cooking oils, animal fats, and algal oils, consisting of the same major components called triacylglycerols can be converted into biodiesel, which is an alternative to conventional diesel fuel produced from petroleum. The chemical reaction and the many process variations and improvements for the production of biodiesel from the various feedstocks are discussed. The properties of the various components of biodiesel are assessed and how they influence the properties of biodiesel produced from different feedstocks. Different options for improving the properties are elucidated from the properties of the individual components. Overall, it is discussed that the alkyl esters of plant oils (biodiesel) are very suitable as a fuel but also have good lubricant and solvent properties.

Technical Abstract: The mono-alkyl esters, most commonly the methyl esters, of vegetable oils, animal fats or other materials consisting mainly of triacylglycerols, often referred to as biodiesel, are an alternative to conventional petrodiesel for use in compression-ignition engines. The fatty acid esters that thus comprise biodiesel largely determine many important fuel properties. In turn, the composition of the biodiesel depends on the composition of the parent feedstock because feedstocks with widely varying fatty acid composition can be used for biodiesel production. The use of different feedstocks is also significant under aspects of increasing biodiesel supply and socio-economic issues. In this article, biodiesel production is briefly described, followed by a discussion of biodiesel fuel properties and the influence of varying fatty acid profiles and feedstocks. It is shown that the properties of biodiesel least influenced by minor components can be determined by a straightforward equation in which the properties of the biodiesel fuel are calculated from the amounts of the individual component fatty esters and their properties. Optimizing biodiesel composition is also addressed.