Methods for improved manufacture of green biodiesel focus on the selection and use of one or more solid metallic oxide base catalyst(s) selected from the group consisting of calcium oxide (CaO), calcium aluminum oxide (CaO—Al2O3), calcium titanate (CaTiO3), barium titanate (BaTiO3), magnesium aluminum oxide (MgO—Al2O3), zinc oxide (ZnO), copper (II) oxide (CuO), nickel oxide (NiO), manganese oxide (MnO), titanium oxide (TiO), vanadium oxide (VO), cobalt oxide (CoO), iron oxide (FeO), chromite (FeCr2O4), hydrotalcite (Mg6Al2(CO3)(OH)16.4(H2O), magnetite (Fe3O4), magnesium silicate and calcium silicate.