Tehran ? the capital city of the Islamic Republic of Iran ? has a daytime population of 13 million people. At night the population drops as people leave for satellite towns. But regardless of time of day, Tehran is still one of the most polluted cities in the world. Based on official statistics, air pollution claims 2,900 to 4000 people?s lives in Tehran only. The main cause of air pollution in the city is reportedly vehicle exhaust fumes. As a result of this poor air quality and in order to lower the rate of pollution, the Government of Iran is forced to declare some days as public holidays every year. However, there are other ways in which the level of pollution can be decreased. For example, recycling used cooking oil into biodiesel. Biodiesel is an alternative fuel which can be easily blended at different ratios with conventional diesel fuel. No vehicle modifications or special fueling equipment?s are required for blending ratios as high as 20%. In other words, biodiesel is a more sustainable fuel that can be used instead of fossil-based diesel fuel to run vehicles. In line with this, Global Environmental Facility/Small Grant Project/UNDP introduced a project titled ?Establishment of the regional site for practical training of sustainable management of waste cooking oil for the establishment of biodiesel as a model in megacities.? Every year in Iran, hundreds of thousands of litres of waste cooking oil are being disposed of in the municipal sewerage system or illegally re-used in the cosmetics industry (mainly for the production of soap), animal feed production and confectionary production. Such non-hygienic uses of used cooking oil poses serious health concerns such as skin irritation, rash and at times even cancer. It should be noted that the disposal of used cooking oil into the municipal sewerage system leads to numerous problems such as congestion of piping systems as well of severe contamination of water resources including underground waters and rivers. Extension Group of Environmentalists in collaboration with Biofuel Research Team ? grantees of GEF SGP/ UNDP ? as well as Iranian Biofuels Society (IBS), Talented Students Organization of Iran along with Danesh (science) National Radio Channel and Javan National Radio Channel organized many events to achieve the goals set forth for the project. The conducted activities ranged from holding hands-on trainings to radio and TV programs, from designing and fabricating WCO biodiesel reactors to participating in national exhibitions and fairs. Over 100,000 individuals were exposed to the teachings of this program directly or indirectly. The aim of the project has been simple ? a cleaner sky for Tehran and the other Iran`s megacities.