This research article is based on the biodiesel synthesis from the marine green macroalga Ulva fasciata, collected fromthe coast of Karachi, Pakistan using new and the most potential waste catalysts from Pakistan Steel Industry. The oil was extracted with n-hexane then it was analyzed by GC, TLC and by the examination of fuel properties. The metal analysis of catalysts was carried out by chemical tests and flame atomic absorption spectroscopy (FAAS). The thermal treatment of catalysts at 1500-1700 degrees C during various processes in steel manufacturing industry converted the metals to metal oxides. The presence of CaO, MgO and ZnO in these catalysts made them highly reactive for biodiesel synthesis. The basicity of waste industrial catalysts was calculated to know their basic strength. The transesterification of U. fasciata oil was performed by fast stirring using 9:1 molar ratio of methanol/oil in the presence of seven different waste industrial catalysts for 6 h at 80-100 degrees C. The solid catalysts were easily separated from product for re-use. In addition, the rate of reaction in the presence of these catalysts was found to be quite feasible. The waste brown dust fromthe steel converter gave the highest yield (88%) of biodiesel. The production of biodiesel was confirmed by TLC examination and fuel properties in comparison with the ASTM standards. (C) 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.