Biodiesel, the fuel of future, synthesis from waste cooking oil (WCO) following esterification and transesterification processes in the presence of a base catalyst KOH, and iron-impregnated activated carbon materials (FeACs) is reported. Various characterizations techniques such as SEM, TEM, HRTEM, SAED, XPS, TPR-H₂, TPD-CO₂ and TPD-NH₃ were used to thoroughly characterize the morphology, surface characters and catalytic potential of the FeACs which were accountable for the catalytic conversion of WCO into biodiesel. The catalytic potential of FeACs was described by the conversion of WCO into fatty acid methyl ester (FAME) in a laboratory scale set up. Among all the FeACs prepared, catalyst E having equimolar ratios (1:1) of KMnO₄ to FeSO₄·7H₂O showed the highest FAME yield, up to 78% under mild reaction conditions. The FAME characterizations and confirmation were examined via FTIR and GC-FID analyses. Moreover, the spent catalyst (E) was found reusable with a consistent FAME yield up to 78% in the first three cycles. Graphical abstract After using the fresh cooking oils for various purposes, the waste cooking oil (WCO) which is frequently sent into the drain can be reused in a better way e.g. producing the fuel for energy i.e. biodiesel by using ecofriendly technique and a commonly available substrate material i.e. activated carbon.