The price of biodiesel compared with petrodiesel is sufficiently high to be a deterrent to consumers. By utilising calcium oxide catalysts, the cost of one of the operational inputs, the catalyst amount, can be decreased. These catalysts are derived via calcination from calcium carbonate containing materials such as marlstones. This research investigated the catalytic potential of two types of marlstones in the trans-esterification of high free fatty acid (FFA) non-edible coconut oil. The marlstones were calcined at 700, 900 and 1000 degrees C for 1.5, 2 and 3 h. For the transesterification reaction, 5 and 15 wt% catalyst were used at 2 h reaction time, 60 degrees C and a 6:1 methanol to oil molar ratio in the presence of vigorous stirring. 15 wt% catalyst for both red and white marlstones produced yields >= 90%. The highest yield of 97% was produced by 15 wt% white marlstones calcined at 1000 degrees C and 1.5 h, with an additional 6 calcined marlstones producing yields >= 90%. All marlstones where yield was >= 90% were fully characterized for surface morphology, elemental analysis, functional group analysis and basicity. (C) 2015 Elsevier Ltd. All rights reserved.