Sustainable biodiesel from used cooking oil: a comparative life cycle, energy, and uncertainty analysis

This study focuses on analyzing the environmental impacts of biodiesel production from Used Cooking Oil (UCO) as a waste management strategy. Using a cradle-to-gate life cycle assessment approach, it compares UCO-derived biodiesel with the first-generation biofuel derived from palm oil. The research addresses the pressing need for sustainable energy alternatives that reduce environmental impacts while promoting waste utilization. The study analyzes multiple environmental impact categories, cumulative energy demand (CED), and includes uncertainty analysis to address variability in data and assumptions across the life cycle. Regression and scatter plot analyses are used to identify correlations between inventory inputs and environmental effects. The study shows that the total carbon and environmental footprint per kg of biodiesel produced from UCO was 0.22 kg CO₂ eq. and 0.11 mPt, compared to 9.87 kg CO₂ eq. and 1.34 mPt for palm oil biodiesel. Electricity, methanol, and steam-derived heat are the primary factors influencing this emission. The total CED for UCO biodiesel was 6.78 MJ, compared to that of palm oil at 18.5 MJ. The net energy ratio of UCO biodiesel is 5.49, outperforming palm oil biodiesel (2.01) and conventional diesel (0.83). The study also shows significant reduction in impacts when including avoided products into the system boundary. The uncertainty of the study is within 10%, which confirms the reliability and robustness of the impact results for UCO biodiesel. This study provides valuable insights for decision-makers in the biofuel industry, promoting waste-to-energy solutions to reduce environmental footprints and support the transition to greener energy systems.