In the present report, the fatty acid alkyl esters and fatty acid amides were synthesized from natural triglycerides by highly selective solvent-free one-step methods using 3.5-CaO@KC-400 nanocrystals as a heterogeneous catalyst. A modified wetness chemical impregnation method was used to prepared potassium carbonate-doped CaO, ZnO, and MgO nanocrystals. The prepared 3.5-CaO@KC-400 nanocrystals were found as the most efficient heterogeneous catalyst (5%, w/w) for amidation (6:1 M ratio of diethanolamine/oil, 110 degrees C) and transesterification (12:1 M ratio of methanol/oil, 65 degrees C) of waste cooking oil and took 30 minutes for the completion of both the reactions. The 3.5-CaO@KC-400 nanocrystals were found to be efficient at room temperature also and reused for 10 reaction cycles for both reactions. The pseudo-first-order kinetic model was applied and the first-order rate constant was calculated as 0.15 minute(-1) and 0.103 minute(-1) for the amidation and transesterification reactions of waste cooking oil, respectively.