Resource recovery and fuel potential of pyrolysis products from waste cooking oil sludge

Waste cooking oil sludge generated during biodiesel feedstock pre-treatment is typically treated as a low-value residue, despite its high organic content and potential for conversion into useful products. This study tested whether pyrolysis could recover valuable fuel products and carbon-rich solid residue from this waste stream. The results showed effective conversion into liquid, gas, and solid products. The liquid fraction could be further separated into light, middle, and heavy fuel cuts with high heating values of 44.3–44.6 MJ kg −1 , while the gas product also exhibited strong fuel quality, with a Wobbe Index of 53.6 MJ Nm −3 , indicating suitability for thermal applications. The biochar retained moderate energy value and carbon-storage potential, although its use in land application would require attention to salinity and alkali-related constraints. In general, increasing pyrolysis temperature shifted the product distribution from liquid to gas. These findings indicate that pyrolysis is a practical route for recovering energy and material value from biodiesel-related sludge streams, supporting waste reduction and circular resource use. This creates a practical opportunity for biodiesel and waste-oil processing industries to reduce disposal burden while recovering useable fuel products from an overlooked residue. Future work should focus on scale-up, safety, product upgrading, and techno-economic evaluation.