Environmental life cycle assessment of polypropylene made from used cooking oil

Used cooking oil (UCO) has received much attention as feedstock for the production of renewable fuels and bio-based materials. This study aims to assess the environmental impact of UCO-based polypropylene (PP) by a cradle-to-factory gate Life-Cycle Assessment (LCA). 16 impact categories were assessed. The results were interpreted with normalization and weighting steps. For several multi-output processes, different allocation procedures were scrutinized. On a normalized and weighted basis, the environmental impacts of UCO-based PP are dominated by climate change (28%), fossil resource use (23%) and water use (11%). The following environmental hotspots are identified: the polymerization process (38%), the production of hydrogen (21%), the production of LPG (18%) and the combustion of LPG (8%). Compared to petrochemical PP, cradle to factory gate impact reductions of 40–62% for climate change and 80–86% for fossil fuel resource use can be achieved by UCO-based PP, depending on the allocation approach chosen. For other impact categories, the environmental footprint of bio-based PP is strongly influenced by the choice of the allocation method.