Co-pyrolysis of lipid waste and red mud was investigated to achieve valorization of red mud by fabricating biochar composite. For the further sustainable approach, this study intentionally employed carbon dioxide (CO2) as reaction medium in the co-pyrolysis process. The use of CO2 on co-pyrolysis of lipid waste and red mud enabled manipulation of the carbon distributions between pyrogenic products. CO2 expedited the thermal cracking of lipid waste and further reacted with lipid waste during the thermolysis. These mechanistic roles of CO2 were catalytically enhanced by the presence of mineral phases (Fe2O3) in red mud, thereby resulting in the enhanced formation of CO (40 times more at 550 degrees C). However, CO2 suppressed dehydrogenation of lipid waste (50%), which resulted in the different pathway for reducing iron oxide in red mud. Moreover, as an aspect of valorization of red mud, catalytic capability of biochar composite was evaluated. As a case study, biodiesel (FAMEs) were synthesized, and all experimental findings suggested that biochar composite could be an effective catalyst for biodiesel synthesis. As compare to biodiesel synthesis using silica (92% yield at 360 degrees C), the equivalent biodiesel yield was achieved with the biochar at much lower temperature (130 degrees C).