The spent bleaching clay (SBC) from the edible oil refining industries contains different types of contaminants, including fatty acids and trace amounts of heavy metals and hazardous materials. Therefore, the conventional procedure of landfilling of SBC is not safe for the environment. Because of this, researchers have been trying to find alternative routes, such as novel processes to regenerate the clay and reuse it. The large amounts of oil remaining in SBC justifies the investigation of in-situ transesterification of the oil to biodiesel. In this study, clays that have been de-oiled by in-situ transesterification at various operating conditions are investigated for their final regenerated bleaching capacity. The different in-situ operating parameters considered are: the choice between two different alkali catalysts, catalyst/SBC ratio, ethanol/SBC ratio, temperature, and reaction time. With 60 different experiments and using the method of experimental design, the optimum operating parameters were determined and presented for achieving maximum bleaching capacity of the regenerated clay. The suggested conditions were then confirmed experimentally. Results showed that the maximum bleaching capacity at these optimum conditions was 17.03%. (C) 2019 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.