Valorization of dairy waste scum oil and rice husk ash-supported CuO nanocatalyst towards cleaner production of biodiesel: A waste-to-energy approach

This study surveys the valorization of dairy waste scum oils (DWSO) to synthesis biodiesel using a novel rice husk ash-supported CuO nanocatalyst. The rice husk ash-supported CuO nanocatalyst was synthesized through a facile impregnation method and characterized by BET, XRD, FTIR, EDX, CO₂/TPD, TEM, and FESEM to confirm its structural and morphological features. Transesterification of DWSO was conducted under optimized conditions, achieving a maximum biodiesel yield of 97.42 % at temperature of 62.36°C, methanol/DWSO proportion of 11:12, and nanocatalyst loading of 2.76 wt% within 2.85 h. Kinetic studies revealed that the transesterification reaction follows a pseudo-first-order model with an activation energy of 100.34 kJ/mol. Thermodynamic analysis indicated that the reaction is endothermic (ΔH = 100.26 kJ/mol) and non-spontaneous (ΔG = −11043.6 kJ/mol) at the studied temperature range, suggesting the requirement of external heat to drive the process. Reusability tests demonstrated that the rice husk ash-supported CuO nanocatalyst retains over 86 % of its initial activity after seven cycles, highlighting its potential for practical applications. This study highlights the dual benefits of utilizing agro-industrial waste for both feedstock and catalyst support, promoting a cleaner and economically viable approach for biodiesel generation.