Synthesis of fatty acid methyl ester from used vegetable cooking oil by solid reusable Mg1−x Zn1+xO2 catalyst

► A reusable heterogeneous catalyst (Mg1−x Zn1+xO2 solid catalyst) was developed. ► Significant operating parameters in FAME production were studied with the developed catalyst on used vegetable cooking oil (UVCO). ► High selectivity of the synthesized catalyst towards ester production was observed. ► Leaching of active components was minimized when the effect of two precipitating media was investigated. ► Stability of catalyst observed with no changes in textural properties when regenerated and reused after four cycles.