Development and characterisation of novel heterogeneous palm oil mill boiler ash-based catalysts for biodiesel production

► Novel heterogeneous palm oil mill boiler ash-based catalysts were developed. ► The optimum catalyst is 15 wt% calcined CaCO3 at 800 °C loaded onto fly ash. ► Fly ash exhibited fine morphology size (<5 μm) and high surface area (1.719 m2/g). ► Maximum crude palm oil conversion of 94.48% is achieved using the novel catalyst.