Biodiesel production through thermally induced transesterification from waste cooking oil using calcium phosphate catalyst

Abstract

Growing concerns over climate change have accelerated the global shift from fossil fuels to renewable energy sources. Among these, biodiesel stands out as a viable alternative due to its compatibility with existing diesel engines. In this context, the development of sustainable and cost-effective strategies for biodiesel production is of increasing importance. This study investigates the potential of waste bovine bone as a low-cost, sustainable catalyst for biodiesel production via thermally induced transesterification. Bovine bones were calcined at 500, 600, and 650 ˚C and subsequently employed in the transesterification of waste cooking oil. Prior to application, their physicochemical properties of the calcined bones were characterized, revealing well-developed meso-/ macro-porous structures and a high calcium content. These structural and compositional features facilitated efficient transesterification, enabling rapid and high biodiesel yields compared to conventional catalytic processes. The biodiesel yield and optimal reaction conditions were dependent on the calcination temperature. With increasing calcination temperature, calcium phosphate was progressively transformed into stoichiometric hydroxyapatite, which enhanced the density of catalytically active sites. Specifically, bovine bone calcined at 650 ˚C exhibited the highest basicity, reaching 0.193 mmol g− 1 , indicating an abundance of basic sites capable of facilitating transesterification by activating methanol. As a result, bovine bone calcined at 650 ˚C achieved a biodiesel yield of 97.7 wt% at 140 ˚C within 1 min, whereas the sample calcined at 500 ˚C showed negligible conversion under identical conditions. Overall, this strategy offers environmentally sustainable and technically effective biodiesel production, while simultaneously promoting the valorization of waste materials.