Although homogenous catalysts result in higher yields in biodiesel processes, a multitude of factors, such as saponification, excess reactant consumption, and additional separation costs, present disadvantages. Hence, we are witnessing an increase in efforts to implement high yield, reusable, non-saponifying heterogeneous catalysts. In the present work, possible use of a low cost volcanic tufa-based catalyst as a support material in the methyl ester reaction was studied and the results were compared with the yields obtained with MCM-41. KI and Mg(NO3)(2) were loaded onto this support by soaking. Effects of temperature, concentration, methanol to oil ratio, reaction time, support materials, particle size distribution, and nature of the active material on esterification yield was studied. The highest yield was obtained with a catalyst of a 500-mu m particle size volcanic tufa prewashed with pure water and loaded with 90 mg KI/g oil active material. The most suitable reaction conditions were found with 0.08 g support/g oil catalyst at 1.1 g methanol/g oil reaction medium at 220 degrees C and reaction duration of 3 h when a methyl ester yield of 91.06 was obtained.