Lithium impregnated calcium oxide has been prepared by wet impregnation method in nano particle form as supported by powder X-ray diffraction and transmission electron microscopy. Basic strength of the same was measured by Hammett indicators. Calcium oxide impregnated with 1.75 wt% of lithium was used as solid catalyst for the transesterification karanja and jatropha oil, containing 3.4 and 8.3 wt% of free fatty acids, respectively. The reaction parameters, viz., reaction temperature, alcohol to oil molar ratio, free fatty acid contents, amount of catalyst and amount of impregnated lithium ion in calcium oxide support, have been studied to establish the most suitable condition for the transesterification reaction. The complete transesterification of karanja and jatropha oils was achieved in 1 and 2 h, respectively, at 65 degrees C, utilizing 12:1 molar ratio of methanol to oil and 5 wt% (catalyst/oil, w/w) of catalyst. Few physicochemical properties of the prepared biodiesel samples have been studied and compared with standard values. (C) 2011 Elsevier Ltd. All rights reserved.