The need for the production of biodiesel in an eco-friendly way has led to the search for photocatalysts that are proficient in converting waste lipids to renewable fuels even under mild conditions. The current research introduces a bioinspired and environmentally friendly Ni/C–CeO 2 –g-C 3 N 4 nanohybrid photocatalyst developed through a two-step sustainable route utilizing carbon obtained from cashew nut shells. The developed ternary heterostructure comprises semiconductors that respond to both UV and visible light coupled with direct Z-scheme electron transfer thereby facilitating efficient charge separation and covering broad solar light. The Ni/C matrix provides π -conjugated conductivity and acts as an electron mediator between CeO 2 and g-C 3 N 4 leading to a 93.5% Fatty Acid Methyl Esters (FAME) yield from used cooking oil via visible-light irradiation. Gas chromatography (GC) quantitatively confirmed the FAME yield and composition, thus confirming the photocatalyst’s high transesterification efficiency. Characterizations of the structures, optical features, and morphology (FTIR, SEM-EDX, UV–Vis, PL) are consistent with the existence of the synergistic interfacial interactions that promote the mobility of charges and enhance the catalytic performance. Overall, the present work illustrates a sustainable photocatalytic route for the synthesis of green biodiesel, while the use of hybrid materials derived from bio-waste in renewable energy applications is emphasized.