The commercial zirconia nanopowder was modified using sulfuric acid and calcium oxide to synthesize SO4/ZrO2 and Zr/CaO catalysts. The wet impregnation technique was utilized to obtain SO4/ZrO2 acid catalyst, and the Zr/CaO base catalyst was produced as well using reflux method through the microwave heating process. The highest total acidity of SO4/ZrO2 catalyst was treated by 0.9 M H2SO4 and 500 °C of calcination temperature, and this catalyst was succeeded in reducing used coconut cooking oil FFA from 1.18% to 0.42% in the esterification process. The highest total alkalinity was reached using 1% w/w Zr/CaO and 900 °C of calcination temperature, and this catalyst was applied in the transesterification stage and successfully converted used coconut cooking oil into biodiesel by 62.25%. The formation of biodiesel was confirmed by the presence of methyl laurate (50.48%), methyl myristate (19.05%), methyl stearate (11.05%), methyl 11-octadecanoic (6.09%), methyl octanoate (5.25%), methyl decanoate (5.05%), and methyl octadecanoate (3.03%)
