Waste Sesamum indicum plant derived heterogeneous catalyst was utilized for the first time for biodiesel synthesis from sunflower oil. The derived catalyst was characterized by using Powder XRD, FT-IR, BET, TGA, XRF, AAS, XPS, SEM-EDX and TEM, and the characterization revealed the presence of Na, K, Ca, Mg, Fe, Mn, Zn, Si, Sr and Cl with high percentage of K (29.64 wt %) and Ca (33.80 wt %) as oxides and carbonates. The catalyst with a moderate surface area of 3.66 m(2) g(-1) exhibited excellent catalytic activity producing a yield of 98.9% biodiesel under the optimized conditions of 12:1 methanol to oil molar ratio and catalyst loading of 7 wt % at the reaction temperature of 65 degrees C in a short reaction time of only 40 min. The catalyst could be reused up to the 3rd cycle of reaction with the yield of 94.2% biodiesel. The characterization of biodiesel was done by using FT-IR, NMR, and GC-MS techniques. The fuel property of produced biodiesel meets the prescribed limits of international standard. The prepared catalyst is easy to handle, reusable, and found to be highly efficient green catalyst that could help in reduction of biodiesel cost. Thus, the catalyst can be recommended as a potential candidate for cost-effective biodiesel production at a large scale. (C) 2019 Elsevier Ltd. All rights reserved.