BET surface area 1 Biodiesel 1 Carbon dioxide 1 Catalyst loadings 1 Catalysts 1 Esterification 1 Esters 1 Fatty acids 1 Fourier transform infrared spectroscopy 1 High fatty acids 1 High free fatty acids 1 Infrared spectroscopy 1 Low cost methods 1 Methanol 1 Palm fatty acid distillate 1 Scanning electron microscopy 1 Shells (structures) 1 Sulfated calcium oxide 1 Supercritical 1 Supercritical methanol 1 Temperature programmed desorption 1 Waste shell X ray diffraction 1