Submitted to: Fuel
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2012
Publication Date: 3/9/2012
Citation: Knothe, G.H., Cermak, S.C., Evangelista, R.L. 2012. Methyl esters from vegetable oils with hydroxy fatty acids: Comparison of lesquerella and castor methyl esters. Fuel. 96:535-540.
Interpretive Summary: Biodiesel is an alternative diesel fuel usually obtained from vegetable oils such as soybean oil or other sources such as animal fats and waste frying oils. However, there are not enough oils and fats available for biodiesel production to replace all diesel fuel obtained from petroleum. For this reason, oils that not have been commonly studied or used for biodiesel production are of significant interest. Castor oil is such an oil but has a composition differing from that of other vegetable oils. It is also not grown domestically. In this work, lesquerella oil, which somewhat resembles the composition of castor oil but is grown domestically, was investigated for its fuel properties. The research showed that the fuel properties of biodiesel from lesquerella oil are overall better than those of biodiesel from castor oil.
Technical Abstract: The search for alternative feedstocks for biodiesel as partial replacement for petrodiesel has recently extended to castor oil. In this work, the castor oil methyl esters were prepared and their properties determined in comparison to the methyl esters of lesquerella oil, which in turn is seen as alternative to castor oil. Both oils contain high amounts of hydroxy fatty acids, castor oil containing ricinoleic acid, lesquerella oil containing lesquerolic acid as C20 homologue of ricinoleic acid. Lesquerella oil, however, contains higher amounts of conventional C18 fatty acids than castor oil. The methyl esters of lesquerella oil exhibit a higher cetane number and lower kinematic viscosity than the methyl esters of castor oil, both values for lesquerella methyl esters being closer to specifications in biodiesel standards while oxidative stability of castor methyl esters is higher although this issue appears complex. Both lesquerella and castor oil methyl esters do not meet biodiesel standards requirements in terms of cetane number, kinematic viscosity and density. Overall, however, lesquerella methyl esters appear to have more favorable fuel properties than castor methyl esters although sulfur content is elevated. Both lesquerella and castor methyl esters have a greater tendency to exceed free glycerol and water specifications in biodiesel standards. The 1H- and 13C-NMR spectra of lesquerella methyl esters are reported.