A highly efficient solid base catalyst was prepared from waste carbide slag and tested for biodiesel production from soybean oil with methanol. The effect of calcination temperature for carbide slag and various reaction parameters on the catalytic performances was systematically investigated. The carbide slag waste calcined at 650 degrees C (CS-650) exhibited 91.3% yield of fatty acid methyl esters (FAME) at reaction temperature of 65 degrees C, methanol/oil molar ratio of 9, catalyst/oil mass ratio of 1.0 wt.% within a short reaction time of 30 min, which was much higher than that of commercial CaO. Furthermore, the relationship between the surface basicity and activity indicated that stronger basicity was responsible for the higher catalytic activity. The merits of high catalytic activity, low cost, and abundant storage make the waste carbide slag a promising catalyst in the production of biodiesel. (C) 2014 Published by Elsevier B.V.