In the present study, rice husk ash (RHA, a solid waste from agriculture) was served as the support for loading
calcined eggshell (another material derived from waste source) to prepare solid base catalyst. This catalyst was
then applied for catalytically converting palm oil into biodiesel. The effects of catalyst preparation conditions
(such as rice husk treatment temperature, the loading of calcined eggshell on the RHA, and the calcination
temperature of eggshell-loaded RHA), reaction conditions (such as reaction time, methanol-to-oil molar ratio
and catalyst loading) and the catalyst reusability were carefully studied. The experimental results revealed that
30% RHA800-800 exhibited the highest catalytic activity. More specifically, when the reaction was carried out
with a reaction time of 4 h, methanol-to-oil molar ratio of 9:1, and catalyst loading of 7 wt.%, the biodiesel
yield could reach 91.5%. Besides, after reused for more than 8 cycles, the catalyst could still possess a rather
high biodiesel yield (above 80%).