Egg shells were used as catalyst for biodiesel production from both commercial fresh soybean oil and waste cooking oil (WCO) at room temperature. After 11 h of regular stirring, high yield of fatty acid methyl ester (FAME) was obtained from fresh soybean oil (98 wt.%) and WCO (97 wt.%). The current work demonstrates the feasibility of utilization and storage of the catalyst as well as the performance of the transesterification reaction at ambient conditions. The reusability of the egg shell-derived catalyst was demonstrated for five cycles for WCO and ten cycles for fresh soybean oil. The catalyst can be stored for at least three months without any decrease in its catalytic activity and for a year with only 10% decrease in FAME yield. Utilization of waste materials (egg shells and used cooking oil) and performing the reaction at ambient conditions make the current method a cheap and environmentally-friendly technique for biodiesel production. (C) 2016 Elsevier Ltd. All rights reserved.