Kalsilite (KAlSiO(4)) was used as a heterogeneous catalyst for transesterification of soybean oil with methanol to biodiesel. Kalsilite showed relatively low catalytic activity for transesterification reaction. The catalytic activity of this catalyst was significantly enhanced by introducing a small amount of lithium nitrate by the impregnation method. A biodiesel yield of 100% and a kinematic viscosity of 3.84 cSt were achieved at a mild temperature of only 120 degrees C over this lithium modified kalsilite catalyst (2.3 wt.% Li). (C) 2010 Elsevier Ltd. All rights reserved.